Developemnt of Single-Crystal Wire and Cable 112_0779-000075

/cgi/content/full/341/6146/640/DC1Supplementary Materials forA Semi-Floating Gate Transistor for Low-Voltage Ultrafast Memoryand Sensing OperationPeng-Fei Wang,* Xi Lin, Lei Liu, Qing-Qing Sun, Peng Zhou, Xiao-Yong Liu, Wei Liu, YiGong, David Wei Zhang*Corresponding author. E-mail: pfw@Published 9 August 2013, Science341, 640 (2013)DOI: 10.1126/science.1240961This PDF file includes:Materials and MethodsSupplementary TextFigs. S1 to S8ReferenceMaterials and MethodsThe Semi-Floating-Gate (SFG) transistors were fabricated using the 0.18-μm manufacturing technologies with specifically designed ion-implant processes and photolithography masks. The process flow and device structures are summarized in Fig. S1. First, a phosphorous-doped drain extension region was formed by ion-implantation and a 6-nm gate oxide layer was grown (Fig. S1A). Then a contact window inside the gate oxide was opened by lithography and buffered-HF wet etching. Boron was implanted into this contact window using the photo-resist as a masking layer (Fig. S1B). After that, the first boron-doped poly-Si layer was deposited and contacted the drain extension region via the aforementioned contact window. The Semi-FG pattern was then formed by lithography and reactive ion etching process which stops on the underlying thin SiO2 layer. This plasma-damaged SiO2 layer was then etched away and a 6 nm SiO2 dielectric was grown and nitrided as the inter-poly-dielectric. An n+-doped poly-Si was then deposited and the control-gate structure shown in Fig. S1C was formed. After the spacer processes, arsenic ions were implanted to form the heavily n-doped source and drain regions. The transmission electron microscope (TEM) cross-sections of the device are shown in Fig. S1D. In Fig. S1E, there is a SiO2 layer between the p+ doped poly-Si and the silicon substrate. However, at the position indicated in Fig. S1F, that SiO2 layer was etched away. With the p+ poly contacts the n-doped drain extension region, a floating pn-junction is formed and became the floating-gate of the device. The processed structures show very good process compatibility with the commercial dual-poly-gate manufacturing technology. Only minor modifications on the standard manufacturing process flow are required and high device yield on 8-inch silicon wafer is obtained. To further reduce the cell size, self-aligned techniques can be used to minimize the size of contact window between the p+ poly and the n-extension region.Supplementary TextThe DC characteristics of the SFG transistors were measured using a parameter analyzer (model Agilent B1500) and a RF probe-station. Figs. S2A to S2D compare the device symbols, the typical transfer I-V curves for MOSFET, FG-MOSFET, and two types of SFG transistors. For comparison, a MOSFET has a gate over the semiconductor channel (Fig. S2A) and a floating-gate MOSFET has a floating-gate between the control-gate and the semiconductor channel (Fig. S2B). The floating-gate MOSFET stores logic “0” with high V th or “1” with low V th by changing the amount of charge inside the floating-gate. By adding a diode or a gated diode between the floating-gate and the drain electrode of FG-MOSFET, a SFG transistor is realized. When the SFG transistor is exposed under light, the photo-carriers generated from the pn-junction diode will be partially collected by the floating-gate and in turn the I D-V CG curves will shift accordingly when changing the light intensity and exposure time. The change in threshold voltage of SFG transistor ( ) is expressed as , where is the change of the amount of charges inside the floating-gate (), is the floating-gate capacitance, and is the coupling ratio of control-gate (S1). During the light exposure process, is increased due to the photocurrent flowing into the floating-gate. The device symbol andthe measured transfer I D-V CG curves for SFG transistor for light sensing are shown in Fig. S2C. It can be seen that V th decreases when the light intensity increases. The device symbol and the measured I D-V CG curves of a SFG transistor optimized for memory function are shown in Fig. S2D. Compared to the SFG transistor shown in Fig. S2C, this SFG cell extends the control-gate over the pn-diode. A gate controlled diode or Tunneling FET (TFET) is formed and connects the semi-floating-gate to the drain. As a result, the TFET can now be used to charge or discharge the floating-gate. The current of TFET depends on the band-to-band tunneling generation rate, i.e. . G BTBT is the band-to-band tunneling generation rate, and it is expressed as. A BTBT and B BTBT are constants, E g is the band-gap energy, and E is the magnitude of the electric field. With a higher V D, the electric field increases and the charge current increases exponentially. As shown in Fig. S2D, the threshold voltage decreases when the drain voltage increases. Fast switching behavior is also observed in the transfer I D-V CG curves. The subthreshold swing even reaches 30 mV/dec when V D equals 3.0V.Because SFG transistor has an entirely new device structure, process and device simulations were carried out using Silvaco TCAD tools before device fabrication. First, the process simulations were performed. The resulted structure was then imported to the device simulator for transient behavior simulation. The ion-implantation conditions were designed for the optimized device performance from the device simulation. Asymmetric doping profiles for the source and drain of the embedded P-TFET are specifically designed to obtain the favorable device electrical behavior. Since the processing parameters were obtained from the process simulation results, the simulated structure is almost identical to the experimental device structure shown in Fig. S1D. The models for simulating a conventional MOSFET were included in the SFG transistor simulation. In addition, Kane’s local band-to-band tunneling model was included for simulating the tunneling current during the device operation. Fig. S3A - S3D display the simulated device structures with current and potential contours. The writing-1 operation is with V CG = -2.0 V and V D = 2.0 V. During the writing-1 operation, the drain is positively biased and the semi-floating-gate has a negative potential, resulting in current flows from the drain to the semi-floating-gate (Fig. S3A). The writing-0 operation is with V CG = 2.0 V and V D = 0 V. During the writing-0 operation, the n+ drain is biased with 0 V and the semi-floating-gate potential is elevated by the capacitive coupling of increased V CG, resulting in current flows from the semi-floating-gate to the drain (Fig. S3B). After writing-1 and writing-0 operations, the potential contours for the “1” and “0” devices at the standby status are plotted in Fig. S3C and S3D. It can be seen that the semi-floating-gate potential of the “1” state is 0.75 V, which is 1.64 V higher than that of the “0” state with the same bias conditions.The transient electrical behavior of the simulated device is shown in Fig. S3E. With the band-to-band tunneling model turned on, the high-speed memory function is realized (black line in the read-out current subfigure of Fig. S3E). It is found from the simulation that the gate-controlled band-to-band tunneling current is the key to high speed writingoperation, especially at the nano-second level. The green line in the read-out current subfigure of Fig. S3E is simulated with the band-to-band tunneling model turned off. It can be seen that writing-1 operation does not work with the same voltage setting. For comparison, the measured transient operation characteristic of the SFG transistor is shown in Fig. S3F. The transient behavior of the measured device is similar to the simulated device with band-to-band tunneling model.The transient behaviors of SFG transistors were measured using the circuit configuration shown in Fig. S4A. The measurement environment includes a RF probe-station, a pulse generator, a transimpedance amplifier circuit, and a high-speed oscilloscope. Two channel signal pulses were generated by the pulse generator (Agilent 81160A) and coupled to the drain and the control-gate electrodes of SFG transistor. A transimpedance amplifier circuit (Fig. S4B) was designed to convert the read-out current of SFG transistor to voltage signal for oscilloscope tracing. In Fig. S4C, the examples of traces captured by the oscilloscope during transient operation are shown. The writing-1 operation was performed by pulses of V D = 2V and V CG = -2V for 3 ns. Then, during the read operation, the voltage drop on the feedback resistor R f was measured by the oscilloscope and then converted to the I drain signal shown in Fig. S4D. It can be seen the readout current is about 2 μA after a 3-ns writing “1” operation. Unlike the conventional DRAM cell, the read operation of the SFG memory device is non-destructive because of its gain cell nature, which means no write-back operation is needed after the reading operation.In order to evaluate the operation speed of SFG transistor for memory application, short writing time with the target pulse width of 0.6 ns was executed (Fig. S5A). Due to the parasitic capacitance of the measurement cables, the rising / falling edges were 0.9 ns and the actual peak width at half height (PWHH) was increased to 1.3 ns. However, the writing-1 and writing-0 operations were successfully demonstrated in Fig. S5B. Meanwhile, it was found that the off-chip read-out circuit oscillates at the beginning of reading operation. Figs. S5B to S5D show the transient operation of the devices with different reading operation time. The reading operation duration was 9 μs in Fig. S5B. First, a writing-1 operation was performed with V D= 2V and V CG= -1.8V. A read-out current of about 1.5 μA was measured for the “1” cell. Then, a writing-0 operation was performed with V D= 0V and V CG= 2V. A very small current representing “0” was measured for the “0” cell. It can be seen that the read-out current oscillates at the beginning of the reading operation. With longer reading time such as 22.4 μs and 45 μs shown in Figs. S5C and S5D, the read-out current became stable. The oscillation was caused by the amplification circuit board (Fig. S4B) which can be improved by using the on-chip read-out circuits. Meanwhile, higher operation speed is expected by reducing the rising / falling edges of the pulses when using the integrated supporting circuits.In Figure S6A, 40 test devices were tested. The operation sequence was writing-0, reading, writing-1, and then reading. A “0” could be written into the transistor with V D of -1V and V CG of 2 V for 3 ms. During the subsequent reading operation, a very small drain current of 30 nA was measured with V D = 2 V and V CG = 2 V. After a writing-1 operation at V D =2 V and V CG = -2 V for 3 ms, the threshold voltage was lowered and a large draincur rent of about 2 μA was measured with V D = 2 V and V CG = 2 V. The wafer map of the reading-1 drain current of 40 test devices showed high uniformity across the whole wafer. The retention time and operation endurance properties were evaluated. In Fig. S6B, the retention time for “0” cell reaches 1 second at room temperature, while the “1” cell does not have retention issue because the semi-floating-gate voltage will be pinned to the drain voltage in the standby state. The retention performance of “0” is good because of the low leakage current of reversely biased p-n structure in the standby status. In Fig. S6C, the device operation endurance was investigated by repeating the full operation sequences. Almost no degradation was observed for 1012cycles of operation. The extrapolated endurance reaches 1015, which is far beyond the endurance of 106 for the conventional floating-gate memory cell.As a memory device, the immunity to various disturb mechanisms is also very important. Figs. S7A to S7F show the disturb properties of SFG memory cell measured at room temperature. Six types of disturb mechanisms on “1” and “0” cells are characterized. Most of the disturb endurances exceed 100 ms except for the disturbance of the writing-0 control-gate voltage on the “1” cell when V D at standby status is set to 1.0 V. During this writing-0 V CG disturb with V CG = 2.0 V and V D = 1.0 V, the pn junction will be weakly forward-biased if “1” is already stored inside the cell. The disturb endurances can be further improved by optimizing the operation voltages and the operation sequences. Using the image sensing SFG transistor, an imaging array can be configured. In Fig. S8, the schematic view of the SFG image sensor array is shown. The source lines and bit lines are arranged above the shallow trench isolation (STI) structure to maximize the fill factor. Using SFG cell as an APS cell, the pixel density of image sensing chip can be increased and the reading operation becomes non-destructive.Fig. S1.Brief summary of the process flow for fabricating the SFG transistor (A to C) and the TEM pictures of SFG transistor along the channel direction (D to F). Inset E is taken from the MOSFET channel where poly-Si on SiO2 can be seen. Inset F is taken from the contact interface between semi-floating-gate and n-doped drain extension region whereno oxide interface exists.Fig. S2Device symbols and transfer characteristics for MOSFET (A), FG-MOSFET (B), and SFG transistors (C, D). The semi-floating-gate is realized by connecting the floating-gate of FG-MOSFET to the drain via a pn junction diode. When the diode works as a photo-diode, photo-sensing function can be realized. When extending the control-gate over the diode, an embedded TFET is formed and dramatically accelerates the writing-1operation.Fig. S3(A, B) Simulated current contours of writing-1 operation and writing-0 operation. During the writing-1 operation, the drain is positively biased and the semi-floating-gate has a negative potential. Current will flow from the drain to the semi-floating-gate. During the writing-0 operation, the n+ drain is biased with 0 V and the semi-floating-gate potential is elevated by the capacitive coupling of increased V CG. Current will flow from the semi-floating-gate to the drain. (C, D) Simulated potential contours for the “1” and “0” devices at the standby state. The semi-floating-gate potential of the “1” state is higher than that of the “0” state with the same external voltages. (E) Simulated transient operation of the SFG transistor. V CG, V D, and the read out I D are displayed separately. In the read out I D figure the simulation results with or without the band-to-band tunneling model are compared. Device does not work when the band-to-band tunneling model is turned off in the simulation. (F) Experimental transient operations are shown for comparison with thesimulation results of Fig. S3E.Fig. S4(A) Transient measurement circuit. The measurement environment includes a RF probe-station, a pulse generator, a transimpedance amplifier circuit, and a high-speed oscilloscope. (B) Specific transimpedance amplifier circuit for converting the current signal to voltage signal for oscilloscope tracing. (C) Examples of measured voltage signals shown on the screen of oscilloscope. (D) Control-gate voltage, drain voltage, and the read-out current of a SFG transistor using 3-ns writing-1 pulse. The voltages are measured directly and the read-out current is converted from the voltage-drop on thefeedback resistor.Fig. S5(A) Measured drain voltage and control-gate voltage pulses for writing “1” and writing “0”, where the peak-width-at-half-height (PWHH) is measured as 1.3 ns. Transient measurement sequence of writing “1” - standby - reading - writing “0” - standby -reading with various reading pulse widths of 9 μs (B), 22.5 μs (C), and 45μs (D).Fig. S6(A) Measured reading-1 drain current wafer map and two transient operation cycles of 40 SFG transistors. The operation sequence is writing-0, reading, writing-1, and then reading. (B) Data retention time of “1” and “0” at room temperature. The read-out operation is performed with various standby periods after the writing operation. (C) Measured operation endurance property. Full writing-reading sequences are repeated with3 ns writing time.Fig. S7Disturb performances of SFG memory cell measured at room temperature. (A) Writing-1 V D disturb on the “1” and “0” cells. (B) Writing-1 V CG disturb on the “1” and “0” cells.(C) Writing-0 V D disturb on the “1” and “0” cells. (D) Writing-0 V CG disturb on the “1” and “0” cells. (E) Reading-operation V D disturb on the “1” and “0” cells. (F) Reading-operation V CG disturb on the “1” and “0” cells.Fig. S8Schematic view of the SFG image sensor array. The source lines and bit lines arearranged above the shallow trench isolation (STI) structure to maximize the fill factor.ReferencesS1. P. Pavan, L. Larcher, and A. Marmiroli, Floating gate devices: operation and compact modeling (Kluwer Acdemic Publisher, Dordrecht, 2004), pp. 37-40.。

半导体分离芯材料英语Semiconductor Materials for Isolation Cores.Semiconductor materials play a crucial role in modern electronics, particularly in the fabrication of isolation cores. Isolation cores are essential components in integrated circuits, ensuring that different sections of the circuit operate independently without interference. This article delves into the world of semiconductor materials suitable for isolation cores, discussing their properties, applications, and challenges.1. Introduction to Semiconductor Materials.Semiconductors are materials that have an electrical conductivity falling between that of conductors and insulators. They exhibit unique electronic properties, making them ideal for use in electronic devices. Silicon (Si) and germanium (Ge) are the most commonly used semiconductors, but others such as gallium arsenide (GaAs)and silicon carbide (SiC) are also finding applications in specific areas.2. Properties of Semiconductor Materials.Bandgap Energy: The bandgap energy is a measure of the energy required to excite an electron from the valence band to the conduction band. Materials with larger bandgap energies are better suited for high-temperature applications.Doping: Semiconductors can be doped with impurities to alter their conductivity. Dopants such as boron (B) or phosphorus (P) are introduced to create p-type or n-type semiconductors, respectively.Lattice Structure: The atomic lattice structure of semiconductors determines their physical and electrical properties. Silicon and germanium have diamond-like lattice structures, which contribute to their widespread use.3. Isolation Cores and Their Importance.Isolation cores are critical in integrated circuits, where they prevent electrical signals from leaking between different circuit sections. This isolation ensures that signals are contained within their designated paths, preventing crosstalk and noise. Isolation cores are typically made from insulating materials, but semiconductor materials can also be used to achieve isolation.4. Semiconductor Materials for Isolation Cores.Silicon-on-Insulator (SOI): SOI technology involves a thin layer of silicon sandwiched between two layers of insulating material, such as silicon dioxide or sapphire. This structure provides excellent isolation between different circuit sections. SOI wafers are widely used in high-performance microelectronics, as they offer reduced parasitic capacitance and improved thermal performance.Silicon Carbide (SiC): SiC is a wide-bandgap semiconductor material with excellent thermal conductivity and chemical stability. It is suitable for high-temperatureand high-power applications. SiC-based isolation cores can withstand extreme operating conditions, making them idealfor use in power electronics and aerospace applications.Gallium Arsenide (GaAs): GaAs has a smaller bandgap than silicon but offers higher electron mobility and saturation velocity. GaAs-based isolation cores are commonly used in high-frequency applications such as microwave and millimeter-wave circuits. GaAs also finds applications in optoelectronics due to its ability to emit and detect light.5. Challenges and Future Outlook.Despite the many advantages of semiconductor materials for isolation cores, there are still challenges to overcome. One major challenge is the scalability of these materialsfor smaller and more complex integrated circuits. Another challenge lies in the fabrication process, which requires precise control over doping levels, lattice structures, and defect densities.Future research in this area will focus on developing new semiconductor materials with improved properties and on optimizing fabrication processes for better scalability and performance. Materials such as two-dimensional semiconductors and topological insulators are beingactively explored for their potential in next-generation electronics.Conclusion.Semiconductor materials play a pivotal role in the fabrication of isolation cores, enabling the reliable operation of integrated circuits. Silicon, silicon carbide, and gallium arsenide are among the most commonly used semiconductors for this purpose, each offering its unique advantages and applications. Future research in this field will focus on addressing challenges related to scalability and fabrication processes while exploring novel materials with improved properties.。

半导体器件英文版Semiconductor devices are electronic components thatutilize the unique properties of semiconductors to perform various functions in electronic circuits. These devices playa crucial role in modern technology and are essential for the operation of almost all electronic devices.One of the most common types of semiconductor devices is the diode, which allows current to flow in only one direction. Diodes are used in rectifiers to convert alternating current (AC) to direct current (DC) and in circuits to protect components from reverse voltage.Transistors are another important semiconductor devicethat are used to amplify or switch electronic signals. There are two main types of transistors: bipolar junctiontransistors (BJTs) and field-effect transistors (FETs). BJTsuse a current to control the flow of another current, while FETs use an electric field to control the flow of current.Integrated circuits (ICs) are semiconductor devices that contain thousands or even millions of individual components, such as transistors, diodes, and resistors, all embedded on a single semiconductor chip. ICs are the building blocks of most electronic devices and can be found in smartphones, computers, televisions, and many other electronic gadgets.Another important semiconductor device is the light-emitting diode (LED), which emits light when an electric current passes through it. LEDs are widely used in displays, indicators, and lighting applications due to their energy efficiency and long lifespan.Semiconductor devices have revolutionized the electronics industry and have enabled the development of advanced technologies such as computers, smartphones, and renewable energy systems. As semiconductor technology continues toevolve, new devices with improved performance and capabilities are being developed to meet the increasing demands of modern electronics.。

《分析化学》阅读材料06 摘自Analytical Chemistry (FECS) ● Molecular systems can be identifies by their characteristic energy term schemes consisting of discrete electronic, vibrational and rotational states. At room temperature the substances are mainly in their electronic and vibrational ground states （电子和振动基态）. Upon interaction with the appropriate type of electromagnetic radiation, characteristic electronic, vibrational and rotational transitions can be induced in the sample. Thses excited states （激发态）usually decay to their original ground states within 10-8s, either by emitting the previously absorbed radiation in all directions with the same or a lower frequency, or by “radiationless” relaxation （无辐射松弛）.● Molecular spectra （分子光谱）can be obtained in the absorption or emission mode from samples in the gaseous, liquid or solid state. They are images of the interactions mentioned above and contain analytical information about the sample.● Most UV-VIS spectra are obtained by measuring the intensity of the absorption of monochromatic radiation across a range of wavelengths passing through a solution in a cuvette （液池）. The practical wavelength region extends from 190-400 nm (UV range) and from 400-780 nm (VIS range).● In a typical experiment, a light beam of intensity I 0 strikes a sample consisting of a quartz or glass cell containing a solution. After passing through the cell, the light beam has a reduced intensity I due to reflection losses at the cell windows, absorption in the sample and, eventually, by scattering at dispersed particles. Only the absorption losses are caused by the dissolved sample. The run is repeated using an identical cell containing only solvent to compensate for reflection and scattering losses, and the transmittance （透射率）T is calculated using the following equation, T =I / I 0 ≈I solution / I solvent . The presentation of transmittance T, as a function of wavelength λ, is the required spectrum of the sample.● The intensity of an absorption band, i.e., the absorbance, is proportional to the number of absorbing species in the illuminated part of the cell. Absorbance, A, is defined by the equation, A = –logT =log(I 0/I) and is proportional to the cell thickness, b [cm], the concentration of the solution c [mol/L]; and a substance-specific proportionality constant ε called the molar absorptivity, [L.mol -1 cm -1]. A = ε b c , the Beer’s Law.● For a given system, a linear relationship exists between A and the sample concentration, but usually only for dilute solution (c ≤ 0.1 mol/L).● The distribution of a solute S, equilibrated between an aqueous phase and an organic solvent may be described by an equilibrium equation: S aq S org .There is no need to choose an aqueous phase as one of the two phase, and we can describe distributions between any pair of immiscible solvents, liquid 1 and liquid 2, with the appropriate solutes, S 1 and S 2, respectively: S 1 S 2. Such systems are described by an equilbrium constant: K D = [S]org / [S]aq or [S]2 / [S]1. Where K D is called the partition coefficient （分配系数）.● In the context of practical chemical procedures, we have to go a step further beyond ideal thermodynamic behavior. For example, in the extraction of an acid HA from an aqueous into an organic phase, we dealing with more than one chemical entity, namely, the dissociated and undissociated acid forms. We can define a partition coefficient only to the ratio of the undissociated acid K D = [HA]org / [HA]aq , which dose not tell the whole story, because, in the aqueous phase the acid may coexist in the dissociated form, and in the organic phase, higher ion pair products may be formed. In general total solute concentrations are determined by analytical investigations, and the information gained is used to explain the distribution of the species between the two phases, including speciation. The ratio of the total concentrations of the solute is a practical means of dealing with distribution equilibrium situations, and is called the distribution ratio （分配比）Dc:Problem1. A solution contains 3.0 mg of iron per liter. The iron is converted into a complex with 1.10-phenanthroline （邻二氮菲）； and the absorbance of the solution in a 2.0 cm cell is 1.20. The molecular weight of the complex is 596. Calculate (a) the absorptivity （吸收系数）and (b)the molar absorptivity （摩尔吸收系数）of the ferrous complex.2. 100 mL of a solution which is 0.100 mol/L in the weak acid HA is extracted with 25.0 mL of ether. After theextraction a 25.0 aliquot of the aqueous phase required 20.0 mL of 0.0500 mol/L NaOH for titration. Calculate the distribution ratio of HA organic to aqueous.3. A sample solution contains Cd 2+ and Zn 2+.A 25.00 mL aliquot is titration with 0.01000 mol/L EDTA at pH5.0, requiring 32.50 mL; another 25.00 mL portion adds potassium iodide in excess, then it is passed through a anion-exchange column （阴离子交换柱）in the basic form. If 20.20 mL of 0.0100 mol/L EDTA is required to titrate the effluent （流出液）at pH 5.0. Calculate the concentrations of Cd 2+ and Zn 2+ in the sample solution. aq org HA of forms all of ion concentrat tatal HA of forms all of ion concentrat tatal Dc ][][=。

半导体物理与器件英语Semiconductor Physics and DevicesThe field of semiconductor physics and devices is a crucial aspect of modern technology, as it underpins the development of a wide range of electronic devices and systems that have transformed our daily lives. Semiconductors, which are materials with electrical properties that lie between those of conductors and insulators, have been the backbone of the digital revolution, enabling the creation of integrated circuits, transistors, and other essential components found in smartphones, computers, and a myriad of other electronic devices.At the heart of semiconductor physics is the study of the behavior of electrons and holes within these materials. Electrons, which are negatively charged particles, and holes, which are the absence of electrons and carry a positive charge, are the fundamental charge carriers in semiconductors. The interactions and movement of these charge carriers within the semiconductor lattice structure are governed by the principles of quantum mechanics and solid-state physics.One of the fundamental concepts in semiconductor physics is theenergy band structure. Semiconductors have a unique energy band structure, with a filled valence band and an empty conduction band separated by an energy gap. The size of this energy gap determines the semiconductor's electrical properties, with materials having a smaller energy gap being more conductive than those with a larger gap.The ability to manipulate the energy band structure and the behavior of charge carriers in semiconductors has led to the development of a wide range of electronic devices. The most prominent of these is the transistor, a fundamental building block of modern electronics. Transistors are used to amplify or switch electronic signals and power, and they are the essential components in integrated circuits, which are the heart of digital devices such as computers, smartphones, and various other electronic systems.Another important class of semiconductor devices are diodes, which are two-terminal devices that allow the flow of current in only one direction. Diodes are used in a variety of applications, including power supplies, rectifiers, and light-emitting diodes (LEDs). LEDs, in particular, have become ubiquitous in modern lighting and display technologies, offering improved energy efficiency, longer lifespan, and enhanced color quality compared to traditional incandescent and fluorescent light sources.Semiconductor devices are not limited to electronic applications; they also play a crucial role in optoelectronics, a field that deals with the interaction between light and electronic devices. Photodetectors, such as photodiodes and phototransistors, are semiconductor devices that convert light into electrical signals, enabling a wide range of applications, including imaging, optical communication, and solar energy conversion.The development of semiconductor physics and devices has been a continuous process, driven by the relentless pursuit of improved performance, efficiency, and functionality. Over the past several decades, we have witnessed remarkable advancements in semiconductor technology, with the miniaturization of devices, the introduction of new materials, and the development of innovative device architectures.One of the most significant trends in semiconductor technology has been the scaling of transistor dimensions, often referred to as Moore's Law. This observation, made by Intel co-founder Gordon Moore in 1965, predicted that the number of transistors on a microchip would double approximately every two years, leading to a dramatic increase in computing power and a corresponding decrease in device size and cost.This scaling has been achieved through a combination ofadvancements in fabrication techniques, material engineering, and device design. For example, the use of high-k dielectric materials and the implementation of FinFET transistor architectures have allowed for continued scaling of transistor dimensions while maintaining or improving device performance and power efficiency.Beyond the scaling of individual devices, the integration of multiple semiconductor components on a single integrated circuit has led to the development of increasingly complex and capable electronic systems. System-on-a-chip (SoC) designs, which incorporate various functional blocks such as processors, memory, and input/output interfaces on a single semiconductor die, have become ubiquitous in modern electronic devices, enabling greater functionality, reduced power consumption, and improved overall system performance.The future of semiconductor physics and devices holds immense promise, with researchers and engineers exploring new materials, device architectures, and application domains. The emergence of wide-bandgap semiconductors, such as silicon carbide (SiC) and gallium nitride (GaN), has opened up new possibilities in high-power, high-frequency, and high-temperature electronics, enabling advancements in areas like electric vehicles, renewable energy systems, and communication networks.Additionally, the integration of semiconductor devices with otheremerging technologies, such as quantum computing, neuromorphic computing, and flexible/wearable electronics, is paving the way for even more transformative applications. These developments have the potential to revolutionize fields ranging from healthcare and transportation to energy and communication, ultimately enhancing our quality of life and shaping the technological landscape of the future.In conclusion, the field of semiconductor physics and devices is a cornerstone of modern technology, underpinning the development of a vast array of electronic devices and systems that have become indispensable in our daily lives. The continuous advancements in this field, driven by the relentless pursuit of improved performance, efficiency, and functionality, have been instrumental in driving the digital revolution and shaping the technological landscape of the21st century. As we move forward, the future of semiconductor physics and devices promises even more remarkable innovations and transformative applications that will continue to shape our world.。

The properties of quantum dotsQuantum dots (QDs) are tiny crystals made up of semiconductor materials. At a size of just a few nanometers, they are too small for us to see with the naked eye and too small even for traditional microscopes to detect. But despite their minuscule size, QDs have captured the attention of scientists and researchers for their unique properties, which have the potential to revolutionize fields from electronics to medicine.One of the key properties of QDs is their size-dependent optical and electronic behavior. Because they are so small, the electrons in QDs are confined to a small space, leading to quantized energy levels. This has important consequences for their behavior in light and electricity. For example, larger QDs absorb light of longer wavelengths while smaller QDs absorb shorter wavelengths. This property can be exploited in a variety of applications, including color-converting LEDs, solar cells, and biological imaging agents.Another significant property of QDs is their high level of luminescence. When illuminated with light of the appropriate wavelength, QDs emit light of a different color, which is highly dependent on the size and composition of the QD. This property makes them useful probes in biological imaging, as they can be targeted to specific molecules and even individual cells, providing high-resolution images with minimal damage to the sample.In addition to their optical properties, QDs also possess unique mechanical and thermal properties. Because of their small size, QDs have a high surface-to-volume ratio, making them extremely sensitive to their environment. This sensitivity can be exploited for sensing applications, such as detecting toxins in the environment or monitoring glucose levels in the body. The high surface area of QDs also allows for efficient heat dissipation, making them promising materials for use in electronics and energy applications.However, despite their many advantages, QDs also pose some challenges. One of the main concerns surrounding QDs is their potential toxicity. Some QDs are composed of heavy metals, such as cadmium and lead, which are known to be toxic to humans and theenvironment. Researchers are working to develop safer QDs made from non-toxic materials, such as zinc and selenium, and to develop methods for removing toxic QDs from the environment.Another challenge facing QD research is their production and scalability. Currently, QDs are produced in small batches using complex chemical synthesis methods, making them expensive and time-consuming to produce. However, researchers are exploring new methods for producing QDs, such as biologically-inspired synthesis using enzymes and bacteria, which could make QDs more accessible for a variety of applications.In conclusion, QDs possess many unique and useful properties, from their size-dependent optical behavior to their high level of luminescence and thermal properties. Though they present some challenges, including toxicity and scalability, ongoing research is exploring new methods and materials to overcome these obstacles and unlock the full potential of QDs for a wide range of applications. As our understanding of these tiny crystals continues to evolve, QDs may prove to be a valuable tool for advancing fields from electronics to medicine and beyond.。

第15卷 第1期 太赫兹科学与电子信息学报Vo1．15，No．1 2017年2月 Journal of Terahertz Science and Electronic Information Technology Feb．，2017 文章编号：2095-4980(2017)01-0015-06太赫兹探测器读出电路的单电子晶体管制备刘永涛1,2，李欣幸2，张志鹏2，方靖岳3，秦 华2*，俞圣雯1*(1.上海大学 材料科学与工程学院，上海 200444；2.中国科学院 苏州纳米技术与纳米仿生研究所 纳米器件与应用重点实验室，江苏 苏州 215123；3.国防科学技术大学 理学院，湖南 长沙 410073)摘 要：射频单电子晶体管具有高电荷灵敏度和高读出速率的特点，可用于超导太赫兹单光子探测器产生的微弱电荷信号的读出。

采用绝缘体上硅(SOI)材料制备的硅基单电子晶体管具有结构可控、工艺可重复的优点。

但是，目前单电子晶体管的成品率约为30%，难以满足探测器阵列化的需求。

为进一步提高单电子晶体管成品率，首先采用电子束零宽度线曝光工艺精确设定单电子晶体管的图形，其次对感应耦合等离子体刻蚀工艺中的气氛比例进行优化，实现电子束曝光图形的良好转移。

最后通过降低氧化温度进一步保持了图形转移的准确度。

单电子晶体管的隧穿势垒宽度得到了良好的控制，使成品率提高到90%，增强了单电子晶体管作为阵列化超导太赫兹单光子探测器读出电路的可行性。

关键词：零宽度线曝光；单电子晶体管；近邻效应；太赫兹单光子探测器；隧穿势垒中图分类号：TN325.2文献标志码：Ａ doi：10.11805/TKYDA201701.0015Fabrication of single electron transistors as the readoutcircuits for terahertz detectorsLIU Yongtao1,2，LI Xinxing2，ZHANG Zhipeng2，FANG Jingyue3，QIN Hua2*，YU Shengwen1*(1.School of Material Science and Engineering，Shanghai University，Shanghai 200444，China；2.Key Laboratory of Nanodevicesand Applications，Suzhou Institute of Nano-Tech and Nano-Bionics，Chinese Academy of Sciences，Suzhou Jiangsu 215123，China；3.National University of Defense Technology，Changsha Hunan 410073，China)Abstract：Radio-Frequency Single-Electron-Transistor(RF-SET) allows for readout of sub-electron-charge with high speed. Hence，a RF-SET could be used as a readout circuit for superconducting terahertzsingle-photon detector which converts photons into charges. SETs could be fabricated on Silicon onInsulator(SOI) with good controllability and reproducibility. However, the current yield of SETs on SOI(about 30%)is not yet sufficient for realizing a detector array. In order to improve the yield, single-lineexposure mode of Electron-Beam Lithography(EBL) is used to precisely define the width of tunnelingbarriers; and the etching gas in Inductively-Coupled Plasma(ICP) etching is optimized to realize goodpattern transfer; oxidation of silicon is performed at a lower temperature to maintain the precision in thedefinition of SETs. Since the tunneling barriers are precisely controlled, the yield of SETs has been increasedto 90%. Such a high yield makes it more practical to implement SETs as readout circuits in detector arrays.Keywords：Single-line exposure；Single Electron Transistor；proximity-effect；THz single photon detector；tunneling barrier太赫兹波(频段0.1∼10 THz)有着极为丰富的电磁波与物质相互作用的效应，并包含了宇宙空间50%的空间光子能量，内含丰富的彗星、行星大气和宇宙背景辐射等信息[1]。

半导体一些术语的中英文对照离子注入机ionimplanterLSS理论LindhandScharffandSchiotttheory 又称“林汉德-斯卡夫-斯高特理论”。

沟道效应channelingeffect射程分布rangedistribution深度分布depthdistribution投影射程projectedrange负性光刻胶negativephotoresist正性光刻胶positivephotoresist无机光刻胶inorganicresist多层光刻胶multilevelresist电子束光刻胶electronbeamresistX射线光刻胶X-rayresist刷洗scrubbing甩胶spinning涂胶photoresistcoating后烘postbaking光刻photolithographyX射线光刻X-raylithography电子束光刻electronbeamlithography离子束光刻ionbeamlithography深紫外光刻deep-UVlithography光刻机maskaligner投影光刻机projectionmaskaligner曝光exposure接触式曝光法contactexposuremethod接近式曝光法proximityexposuremethod光学投影曝光法opticalprojectionexposuremethod磷硅玻璃phosphorosilicateglass硼磷硅玻璃boron-phosphorosilicateglass钝化工艺passivationtechnology 多层介质钝化multilayerdielectricpassivation划片scribing电子束切片electronbeamslicing烧结sintering印压indentation热压焊thermocompressionbonding热超声焊thermosonicbonding冷焊coldwelding点焊spotwelding球焊ballbonding楔焊wedgebonding内引线焊接innerleadbonding外引线焊接outerleadbonding梁式引线beamlead装架工艺mountingtechnology附着adhesion封装packaging金属封装metallicpackagingAmbipolar双极的Ambienttemperature环境温度Amorphous无定形的，非晶体的Amplifier功放扩音器放大器Analogue(Analog)comparator模拟比较器Angstrom埃Anneal退火Anisotropic各向异性的Anode阳极Arsenic(AS)砷Auger俄歇Augerprocess俄歇过程Avalanche雪崩Avalanchebreakdown雪崩击穿Avalancheexcitation雪崩激发Backgroundcarrier本底载流子Backgrounddoping本底掺杂Backward反向Backwardbias反向偏置Ballastingresistor整流电阻Ballbond球形键合Band能带Bandgap能带间隙Barrier势垒Barrierlayer势垒层Barrierwidth势垒宽度Base基极Basecontact基区接触Basestretching基区扩展效应Basetransittime基区渡越时间Basetransportefficiency基区输运系数Base-widthmodulation基区宽度调制Basisvector基矢Bias偏置Bilateralswitch双向开关Binarycode二进制代码Binarycompoundsemiconductor二元化合物半导体Bipolar双极性的BipolarJunctionTransistor(BJT)双极晶体管Bloch布洛赫Blockingband阻挡能带Chargeconservation电荷守恒Chargeneutralitycondition电中性条件Chargedrive/exchange/sharing/transfer/storage电荷驱动/交换/共享/转移/存储Chemmicaletching化学腐蚀法Chemically-Polish化学抛光Chemmically-MechanicallyPolish(CMP)化学机械抛光Chip芯片Chipyield芯片成品率Clamped箝位Clampingdiode箝位二极管Cleavageplane解理面Clockrate时钟频率Clockgenerator时钟发生器Clockflip-flop时钟触发器Close-packedstructure密堆积结构Close-loopgain闭环增益Collector集电极Collision碰撞CompensatedOP-AMP补偿运放Common-base/collector/emitterconnection共基极/集电极/发射极连接Common-gate/drain/sourceconnection共栅/漏/源连接Common-modegain共模增益Common-modeinput共模输入Common-moderejectionratio(CMRR)共模抑制比Compatibility兼容性Compensation补偿Compensatedimpurities补偿杂质Compensatedsemiconductor补偿半导体ComplementaryDarlingtoncircuit互补达林顿电路ComplementaryMetal-Oxide-SemiconductorField-Effect-Transistor(CMOS)互补金属氧化物半导体场效应晶体管Complementaryerrorfunction余误差函数Computer-aideddesign(CAD)/test(CAT)/manufacture(CAM)计算机辅助设计/测试/制De.broglie德布洛意Decderate减速Decibel(dB)分贝Decode译码Deepacceptorlevel深受主能级Deepdonorlevel深施主能级Deepimpuritylevel深度杂质能级Deeptrap深陷阱Defeat缺陷Degeneratesemiconductor简并半导体Degeneracy简并度Degradation退化DegreeCelsius(centigrade)/Kelvin摄氏/开氏温度Delay延迟Density密度Densityofstates态密度Depletion耗尽Depletionapproximation耗尽近似Depletioncontact耗尽接触Depletiondepth耗尽深度Depletioneffect耗尽效应Depletionlayer耗尽层DepletionMOS耗尽MOSDepletionregion耗尽区Depositedfilm淀积薄膜Depositionprocess淀积工艺Designrules设计规则Die芯片（复数dice）Diode二极管Dielectric介电的Dielectricisolation介质隔离Difference-modeinput差模输入Differentialamplifier差分放大器Differentialcapacitance微分电容Diffusedjunction扩散结Diffusion扩散Diffusioncoefficient扩散系数Diffusionconstant扩散常数Diffusivity扩散率Diffusioncapacitance/barrier/current/furnace扩散电容/势垒/电流/炉Electrostatic静电的Element元素/元件/配件Elementalsemiconductor元素半导体Ellipse椭圆Ellipsoid椭球Emitter发射极Emitter-coupledlogic发射极耦合逻辑Emitter-coupledpair发射极耦合对Emitterfollower射随器Emptyband空带Emittercrowdingeffect发射极集边（拥挤）效应Endurancetest=lifetest寿命测试Energystate能态Energymomentumdiagram能量-动量(E-K)图Enhancementmode增强型模式EnhancementMOS增强性MOSEntefic(低)共溶的Environmentaltest环境测试Epitaxial外延的Epitaxiallayer外延层Epitaxialslice外延片Expitaxy外延Equivalentcurcuit等效电路Equilibriummajority/minoritycarriers平衡多数/少数载流子ErasableProgrammableROM(EPROM)可搽取（编程）存储器Errorfunctioncomplement余误差函数Etch刻蚀Etchant刻蚀剂Etchingmask抗蚀剂掩模Excesscarrier过剩载流子Excitationenergy激发能Excitedstate激发态Exciton激子Extrapolation外推法Extrinsic非本征的Extrinsicsemiconductor杂质半导体Face-centered面心立方Falltime下降时间Heatsink散热器、热沉Heavy/lightholeband重/轻空穴带Heavysaturation重掺杂Hell-effect霍尔效应Heterojunction异质结Heterojunctionstructure异质结结构HeterojunctionBipolarTransistor（HBT）异质结双极型晶体Highfieldproperty高场特性High-performanceMOS.(H-MOS)高性能MOS.Hormalized归一化Horizontalepitaxialreactor卧式外延反应器Hotcarrior热载流子Hybridintegration混合集成Image-force镜象力Impactionization碰撞电离Impedance阻抗Imperfectstructure不完整结构Implantationdose注入剂量Implantedion注入离子Impurity杂质Impurityscattering杂志散射Incrementalresistance电阻增量（微分电阻）In-contactmask接触式掩模Indiumtinoxide(ITO)铟锡氧化物Inducedchannel感应沟道Infrared红外的Injection注入Inputoffsetvoltage输入失调电压Insulator绝缘体InsulatedGateFET(IGFET)绝缘栅FETIntegratedinjectionlogic集成注入逻辑Integration集成、积分Interconnection互连Interconnectiontimedelay互连延时Interdigitatedstructure交互式结构Interface界面Interference干涉Internationalsystemofunions国际单位制Internallyscattering谷间散射Matching匹配Maxwell麦克斯韦Meanfreepath平均自由程Meanderedemitterjunction梳状发射极结Meantimebeforefailure(MTBF)平均工作时间Megeto-resistance磁阻Mesa台面MESFET-MetalSemiconductor金属半导体FETMetallization金属化Microelectronictechnique微电子技术Microelectronics微电子学Millenindices密勒指数Minoritycarrier少数载流子Misfit失配Mismatching失配Mobileions可动离子Mobility迁移率Module模块Modulate调制Molecularcrystal分子晶体MonolithicIC单片ICMOSFET金属氧化物半导体场效应晶体管Mos.Transistor(MOST)MOS.晶体管Multiplication倍增Modulator调制Multi-chipIC多芯片ICMulti-chipmodule(MCM)多芯片模块Multiplicationcoefficient倍增因子Nakedchip未封装的芯片（裸片）Negativefeedback负反馈Negativeresistance负阻Nesting套刻Negative-temperature-coefficient负温度系数Noisemargin噪声容限Nonequilibrium非平衡Nonrolatile非挥发（易失）性Normallyoff/on常闭/开Numericalanalysis数值分析Occupiedband满带Officienay功率Photoelectriccell光电池Photoelectriceffect光电效应Photoenicdevices光子器件Photolithographicprocess光刻工艺(photo)resist（光敏）抗腐蚀剂Pin管脚Pinchoff夹断PinningofFermilevel费米能级的钉扎（效应）Planarpro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WidenModulator(PWM)脉冲宽度调制Punchthrough穿通Push-pullstage推挽级Qualityfactor品质因子Quantization量子化Schottkybarrier肖特基势垒Schottkycontact肖特基接触Schrodingen薛定厄Scribinggrid划片格Secondaryflat次平面Seedcrystal籽晶Segregation分凝Selectivity选择性Selfaligned自对准的Selfdiffusion自扩散Semiconductor半导体Semiconductor-controlledrectifier可控硅Sendsitivity灵敏度Serial串行/串联Seriesinductance串联电感Settletime建立时间Sheetresistance薄层电阻Shield屏蔽Shortcircuit短路Shotnoise散粒噪声Shunt分流Sidewallcapacitance边墙电容Signal信号Silicaglass石英玻璃Silicon硅Siliconcarbide碳化硅Silicondioxide(SiO2)二氧化硅SiliconNitride(Si3N4)氮化硅SiliconOnInsulator绝缘硅Siliverwhiskers银须Simplecubic简立方Singlecrystal单晶Sink沉Skineffect趋肤效应Snaptime急变时间Sneakpath潜行通路Sulethreshold亚阈的Solarbattery/cell太阳能电池Solidcircuit固体电路SolidSolubility固溶度Sonband子带Transistoraging(stress)晶体管老化Transittime渡越时间Transition跃迁Transition-metalsilica过度金属硅化物Transitionprobability跃迁几率Transitionregion过渡区Transport输运Transverse横向的Trap陷阱Trapping俘获Trappedcharge陷阱电荷Trianglegenerator三角波发生器Triboelectricity摩擦电Trigger触发Trim调配调整Triplediffusion三重扩散Truthtable真值表Tolerahce容差Tunnel(ing)隧道（穿）Tunnelcurrent隧道电流Turnover转折Turn-offtime关断时间Ultraviolet紫外的Unijunction单结的Unipolar单极的Unitcell原（元）胞Unity-gainfrequency单位增益频率Unilateral-switch单向开关Vacancy空位Vacuum真空Valence(value)band价带Valuebandedge价带顶Valencebond价键Vapourphase汽相Varactor变容管Varistor变阻器Vibration振动Voltage电压Wafer晶片Waveequation波动方程Waveguide波导Wavenumber波数CT:ContaminationThreshold??污染阀值Ctrl:Control控制；管理；抑制D:Die芯片DAC igitalAnalogConverter??数字转换器DSP igitalSignalProcessing数字信号处理EFO:ElevtronicFlame-Off电子打火系统FA:FaceAngle顶锥角（面锥角）FAB:FreeAirBall空气球FD:FloppyDisk软盘，软式磁碟片Frd:Forward??前进GEM:GenericHi:HightMagnification高倍率Hybd:Hybrid混合动力/混合式Impd:Impedence阻抗Ins:Inspection检查，检验L/F eadFrame框架Lo:LowMagnification低倍率PM reventiveMaintenance??PR atternRecognitionT/P:TopPlate??顶板UPH:UnitPerHour??每小时产量UTI:UltrasonicTransducerInterface超声波传感受器接口VLL:VisualLeadLocator导脚定位W/C:WireClamp??线夹W/H:WorkHolder??轨道W/S:WireSpool??线轴ESD:ElectroStaticDischarge静电释放EPa:ESDProtectedarea??静电防护区ESDS??????????????????????静电敏感设备BM:BreakdownMaintenance事后维修CM:CorrectiveMaintenance改良保养PVM:PreventiveMaintenance预防保养MP:MaintencePreventive保养预防PM:ProductionMaintenance生产保养BG：backgrinding??背部研磨DS：diesaw????将wafer切die DA：dieattach??=DB:diebond??装片WB：wirebond焊线????。

附录附录A:外文资料翻译—原文部分SemiconductorA semiconductor is a solid material that has electrical conductivity between those of a conductor and an insulator; it can vary over that wide range either permanently or dynamically.[1]Semiconductors are important in electronic technology. Semiconductor devices, electronic components made of semiconductor materials, are essential in modern consumer electronics, including computers, mobile phones, and digital audio players. Silicon is used to create most semiconductors commercially, but dozens of other materials are used.Bragg reflection in a diffuse latticeA second way starts with free electrons waves. When fading in an electrostatic potential due to the cores, due to Bragg reflection some waves are reflected and cannot penetrate the bulk, that is a band gap opens. In this description it is not clear, while the number of electrons fills up exactly all states below the gap.Energy level splitting due to spin state Pauli exclusionA third description starts with two atoms. The split states form a covalent bond where two electrons with spin up and spin down are mostly in between the two atoms. Adding more atoms now is supposed not to lead to splitting, but to more bonds. This is the way silicon is typically drawn. The band gap is now formed by lifting one electron from the lower electron level into the upper level. This level is known to be anti-bonding, but bulk silicon has not been seen to lose atoms as easy as electrons are wandering through it. Also this model is most unsuitable to explain how in graded hetero-junction the band gap can vary smoothly.Energy bands and electrical conductionLike in other solids, the electrons in semiconductors can have energies only within certain bands (ie. ranges of levels of energy) between the energy of the ground state, corresponding to electrons tightly bound to the atomic nuclei of the material, and the free electron energy, which is the energy required for an electron to escape entirely from the material. The energy bands each correspond to a large number of discrete quantum states of the electrons, and most of the states with low energy (closer to the nucleus) are full, up to a particular band called the valence band. Semiconductors and insulators are distinguished from metals because the valence band in the semiconductor materials is very nearly full under usual operating conditions, thus causing more electrons to be available in the conduction band.The ease with which electrons in a semiconductor can be excited from the valence band to the conduction band depends on the band gap between the bands, and it is the size of this energybandgap that serves as an arbitrary dividing line (roughly 4 eV) between semiconductors and insulators.In the picture of covalent bonds, an electron moves by hopping to a neighboring bond. Because of the Pauli exclusion principle it has to be lifted into the higher anti-bonding state of that bond. In the picture of delocalized states, for example in one dimension that is in a wire, for every energy there is a state with electrons flowing in one direction and one state for the electrons flowing in the other. For a net current to flow some more states for one direction than for the other direction have to be occupied and for this energy is needed. For a metal this can be a very small energy in the semiconductor the next higher states lie above the band gap. Often this is stated as: full bands do not contribute to the electrical conductivity. However, as the temperature of a semiconductor rises above absolute zero, there is more energy in the semiconductor to spend on lattice vibration and — more importantly for us — on lifting some electrons into an energy states of the conduction band, which is the band immediately above the valence band. The current-carrying electrons in the conduction band are known as "free electrons", although they are often simply called "electrons" if context allows this usage to be clear.Electrons excited to the conduction band also leave behind electron holes, or unoccupied states in the valence band. Both the conduction band electrons and the valence band holes contribute to electrical conductivity. The holes themselves don't actually move, but a neighboring electron can move to fill the hole, leaving a hole at the place it has just come from, and in this way the holes appear to move, and the holes behave as if they were actual positively charged particles.One covalent bond between neighboring atoms in the solid is ten times stronger than the binding of the single electron to the atom, so freeing the electron does not imply destruction of the crystal structure.Holes: electron absence as a charge carrierThe notion of holes, which was introduced for semiconductors, can also be applied to metals, where the Fermi level lies within the conduction band. With most metals the Hall effect reveals electrons to be the charge carriers, but some metals have a mostly filled conduction band, and the Hall effect reveals positive charge carriers, which are not the ion-cores, but holes. Contrast this to some conductors like solutions of salts, or plasma. In the case of a metal, only a small amount of energy is needed for the electrons to find other unoccupied states to move into, and hence for current to flow. Sometimes even in this case it may be said that a hole was left behind, to explain why the electron does not fall back to lower energies: It cannot find a hole. In the end in both materials electron-phonon scattering and defects are the dominant causes for resistance.Fermi-Dirac distribution. States with energy εbelow the Fermi energy, here μ, have higher probability n to be occupied, and those above are less likely to be occupied. Smearing of the distribution increases with temperature.The energy distribution of the electrons determines which of the states are filled and which are empty. This distribution is described by Fermi-Dirac statistics. The distribution is characterized bythe temperature of the electrons, and the Fermi energy or Fermi level. Under absolute zero conditions the Fermi energy can be thought of as the energy up to which available electron states are occupied. At higher temperatures, the Fermi energy is the energy at which the probability of a state being occupied has fallen to 0.5.The dependence of the electron energy distribution on temperature also explains why the conductivity of a semiconductor has a strong temperature dependency, as a semiconductor operating at lower temperatures will have fewer available free electrons and holes able to do the work.Energy–momentum dispersionIn the preceding description an important fact is ignored for the sake of simplicity: the dispersion of the energy. The reason that the energies of the states are broadened into a band is that the energy depends on the value of the wave vector, or k-vector, of the electron. The k-vector, in quantum mechanics, is the representation of the momentum of a particle.The dispersion relationship determines the effective mass, m* , of electrons or holes in the semiconductor, according to the formula:The effective mass is important as it affects many of the electrical properties of the semiconductor, such as the electron or hole mobility, which in turn influences the diffusivity of the charge carriers and the electrical conductivity of the semiconductor.Typically the effective mass of electrons and holes are different. This affects the relative performance of p-channel and n-channel IGFETs, for example (Muller & Kamins 1986:427).The top of the valence band and the bottom of the conduction band might not occur at that same value of k. Materials with this situation, such as silicon and germanium, are known as indirect bandgap materials. Materials in which the band extrema are aligned in k, for example gallium arsenide, are called direct bandgap semiconductors. Direct gap semiconductors are particularly important in optoelectronics because they are much more efficient as light emitters than indirect gap materials.Carrier generation and recombinationWhen ionizing radiation strikes a semiconductor, it may excite an electron out of its energy level and consequently leave a hole. This process is known as electron–hole pair generation.Electron-hole pairs are constantly generated from thermal energy as well, in the absence of any external energy source.Electron-hole pairs are also apt to recombine. Conservation of energy demands that these recombination events, in which an electron loses an amount of energy larger than the band gap, beaccompanied by the emission of thermal energy (in the form of phonons) or radiation (in the form of photons).In some states, the generation and recombination of electron–hole pairs are in equipoise. The number of electron-hole pairs in the steady state at a given temperature is determined by quantum statistical mechanics. The precise quantum mechanical mechanisms of generation and recombination are governed by conservation of energy and conservation of momentum.As the probability that electrons and holes meet together is proportional to the product of their amounts, the product is in steady state nearly constant at a given temperature, providing that there is no significant electric field (which might "flush" carriers of both types, or move them from neighbour regions containing more of them to meet together) or externally driven pair generation. The product is a function of the temperature, as the probability of getting enough thermal energy to produce a pair increases with temperature, being approximately 1×exp(−E G / kT), where k is Boltzmann's constant, T is absolute temperature and E G is band gap.The probability of meeting is increased by carrier traps – impurities or dislocations which can trap an electron or hole and hold it until a pair is completed. Such carrier traps are sometimes purposely added to reduce the time needed to reach the steady state.DopingThe property of semiconductors that makes them most useful for constructing electronic devices is that their conductivity may easily be modified by introducing impurities into their crystal lattice. The process of adding controlled impurities to a semiconductor is known as doping. The amount of impurity, or dopant, added to an intrinsic (pure) semiconductor varies its level of conductivity. Doped semiconductors are often referred to as extrinsic.DopantsThe materials chosen as suitable dopants depend on the atomic properties of both the dopant and the material to be doped. In general, dopants that produce the desired controlled changes are classified as either electron acceptors or donors. A donor atom that activates (that is, becomes incorporated into the crystal lattice) donates weakly-bound valence electrons to the material, creating excess negative charge carriers. These weakly-bound electrons can move about in the crystal lattice relatively freely and can facilitate conduction in the presence of an electric field. (The donor atoms introduce some states under, but very close to the conduction band edge. Electrons at these states can be easily excited to conduction band, becoming free electrons, at room temperature.) Conversely, an activated acceptor produces a hole. Semiconductors doped with donor impurities are called n-type, while those doped with acceptor impurities are known as p-type. The n and p type designations indicate which charge carrier acts as the material's majority carrier. The opposite carrier is called the minority carrier, which exists due to thermal excitation at a much lower concentration compared to the majority carrier.For example, the pure semiconductor silicon has four valence electrons. In silicon, the most common dopants are IUPAC group 13 (commonly known as group III) and group 15 (commonly known as group V) elements. Group 13 elements all contain three valence electrons, causing them to function as acceptors when used to dope silicon. Group 15 elements have five valence electrons, which allows them to act as a donor. Therefore, a silicon crystal doped with boron creates a p-type semiconductor whereas one doped with phosphorus results in ann-type material.Carrier concentrationThe concentration of dopant introduced to an intrinsic semiconductor determines its concentration and indirectly affects many of its electrical properties. The most important factor that doping directly affects is the material's carrier concentration. In an intrinsic semiconductor under thermal equilibrium, the concentration of electrons and holes is equivalent. That is,n = p = n iIf we have a non-intrinsic semiconductor in thermal equilibrium the relation becomes:n0 * p0 = (n i)2Where n is the concentration of conducting electrons, p is the electron hole concentration, and n i is the material's intrinsic carrier concentration. Intrinsic carrier concentration varies between materials and is dependent on temperature. Silicon's n i, for example, is roughly 1.6×1010 cm-3 at 300 kelvin (room temperature).In general, an increase in doping concentration affords an increase in conductivity due to the higher concentration of carriers available for conduction. Degenerately (very highly) doped semiconductors have conductivity levels comparable to metals and are often used in modern integrated circuits as a replacement for metal. Often superscript plus and minus symbols are used to denote relative doping concentration in semiconductors. For example, n+ denotes an n-type semiconductor with a high, often degenerate, doping concentration. Similarly, p−would indicate a very lightly doped p-type material. It is useful to note that even degenerate levels of doping imply low concentrations of impurities with respect to the base semiconductor. In crystalline intrinsic silicon, there are approximately 5×1022 atoms/cm³. Doping concentration for silicon semiconductors may range anywhere from 1013 cm-3 to 1018 cm-3. Doping concentration above about 1018 cm-3 is considered degenerate at room temperature. Degenerately doped silicon contains a proportion of impurity to silicon in the order of parts per thousand. This proportion may be reduced to parts per billion in very lightly doped silicon. Typical concentration values fall somewhere in this range and are tailored to produce the desired properties in the device that the semiconductor is intended for.Effect on band structureDoping a semiconductor crystal introduces allowed energy states within the band gap but very close to the energy band that corresponds with the dopant type. In other words, donor impurities create states near the conduction band while acceptors create states near the valence band. The gap between these energy states and the nearest energy band is usually referred to as dopant-sitebonding energy or E B and is relatively small. For example, the E B for boron in silicon bulk is0.045 eV, compared with silicon's band gap of about 1.12 eV. Because E B is so small, it takes little energy to ionize the dopant atoms and create free carriers in the conduction or valence bands. Usually the thermal energy available at room temperature is sufficient to ionize most of the dopant.Dopants also have the important effect of shifting the material's Fermi level towards the energy band that corresponds with the dopant with the greatest concentration. Since the Fermi level must remain constant in a system in thermodynamic equilibrium, stacking layers of materials with different properties leads to many useful electrical properties. For example, the p-n junction's properties are due to the energy band bending that happens as a result of lining up the Fermi levels in contacting regions of p-type and n-type material.This effect is shown in a band diagram. The band diagram typically indicates the variation in the valence band and conduction band edges versus some spatial dimension, often denoted x. The Fermi energy is also usually indicated in the diagram. Sometimes the intrinsic Fermi energy, E i, which is the Fermi level in the absence of doping, is shown. These diagrams are useful in explaining the operation of many kinds of semiconductor devices.Preparation of semiconductor materialsSemiconductors with predictable, reliable electronic properties are necessary for mass production. The level of chemical purity needed is extremely high because the presence of impurities even in very small proportions can have large effects on the properties of the material. A high degree of crystalline perfection is also required, since faults in crystal structure (such as dislocations, twins, and stacking faults) interfere with the semiconducting properties of the material. Crystalline faults are a major cause of defective semiconductor devices. The larger the crystal, the more difficult it is to achieve the necessary perfection. Current mass production processes use crystal ingots between four and twelve inches (300 mm) in diameter which are grown as cylinders and sliced into wafers.Because of the required level of chemical purity and the perfection of the crystal structure which are needed to make semiconductor devices, special methods have been developed to produce the initial semiconductor material. A technique for achieving high purity includes growing the crystal using the Czochralski process. An additional step that can be used to further increase purity is known as zone refining. In zone refining, part of a solid crystal is melted. The impurities tend to concentrate in the melted region, while the desired material recrystalizes leaving the solid material more pure and with fewer crystalline faults.In manufacturing semiconductor devices involving heterojunctions between different semiconductor materials, the lattice constant, which is the length of the repeating element of the crystal structure, is important for determining the compatibility of materials.附录B:外文资料翻译—译文部分半导体半导体是一种导电性能介于导体与绝缘体之间的固体材料。