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Addition Energy Spectra of Semiconductor Quantum Dots

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Journal of the Korean Physical Society,Vol.34,No.,April1999,pp.S46∼S49Addition Energy Spectra of Semiconductor Quantum DotsIn-Ho LeeSchool of Physics,Korea Institute for Advanced Study,Seoul130-012We determined the electron-number-dependent capacitive energy,the energy required to add an additional electron to a quantum dot,by self-consistent solution of the Kohn-Sham equation.Shell-filling and spin configuration effects are identified,as found in electronic structure of the atoms.The peak positions of the capacitive energy at the number of electrons N=2,6,and12for thecylindrical symmetric quantum dot are in good agreement with experimental data.I.INTRODUCTIONAdvances in the semiconductor technologies allow the realization of quantum dot structure in which afinite number of electrons are confined by an artificial po-tentials[1–3].The number of electrons in a quantum dot,denoted N,which can also be controlled experi-mentally,affects many physical properties of the quan-tum dot.By changing the quantum dot size and the number of electrons,far-infrared absorption[3–7],capac-itance spectroscopy[8],and conductance measurements [2,3]determine the tunneling conductance and capaci-tance resulting from the competition of quantum con-finements and Coulomb interactions.Recently,Tarucha and his coworkers probed the electronic states of a few-electron quantum dot through single-electron tunneling spectroscopy[4].They also measured the effects of spin configuration and confirmed Hund’s rule favoring thefill-ing of parallel spins by applying tunable magneticfields to the quantum dots.Furthermore,Macucci et al.have calculated the shell-filling behavior of two-dimensional cylindrical quantum dots within the framework of den-sity functional theory[9,10].Many-body effects due to the electron-electron interactions show a broad range of electronic structures similar to those of the real atoms. The capacitive energy of up to thirteen electrons is ob-tained through a self-consistent total energy calculation for model three-dimensional quantum dots.The explicit electron-spin interactions are taken into account via spin density functional theory,which properly describes the spin effects of atomic systems.The outline of this paper is as follows.In Sec.II,we concisely present our theoretical method.The calculated results and discussion are shown in Sec.III.A brief summary is given in Sec.IV.II.THEORETICAL METHODSWe assume that there is no coupling between thedot and the metallic gate contacts as found in ex-periments.The effective mass and the dielectric con-stant are denoted by m∗andε,respectively.Rescaled atomic units are used throughout,with energy in units of2Ry∗=m∗e4/¯h2ε2and lengths in units of the effec-tive Bohr radius a∗B=¯h2ε/m∗e2.We calculated the electronic structure of GaAs quantum dots by using the dielectric constant ofε=12.9and effective mass of m∗=0.067m e.The corresponding energy and lengthscales are2Ry∗=10.96meV and a∗B=101.88˚A,re-spectively.Within the effective mass approximation and spin density functional theory,one can write the spin polarized effective Hamiltonians of quantum dot,ˆH±=−12∇2+12ω2x x2+12ω2y y2(1)+12ω2z z2+V H(r)+V±xc(r),including the external potentials described byωx,ωy, andωz of the anisotropic parabolic three-dimensional po-tential,Hartree V H(r),and exchange-correlation V xc(r) as shown in Eq.(1).We used the higher-orderfi-nite difference formula for the Laplacian operator in the Hamiltonian[11,12],with a seven-point stencil in each direction,and iteratively diagonalized the Hamiltonian in three-dimensional Cartesian coordinates with uniform grids.Spin polarized Kohn-Sham equations[13,14]were solved self-consistently to calculate the total energy of the quantum dots.The Hartree potential and energy due to the electrons in the quantum dot were obtained by solving the Poisson equation using preconditioned con-jugate gradient method.[15,16]We used the simplified version of the recent GGA func-tional by Perdew,Burke,and Ernzerhof[17,18],which satisfies many exact properties of density functional the-ory.In our calculations we have taken the effective ki-netic energy cutoff(πh)2Ry∗≈110Ry∗related to theuniform grid spacing h in a∗Bas found in usual plane wave basis set formulation.The chemical potentialµ(N)for N electrons can be defined[19]by the total energy differ-ence between the number of N and the number of N−1-S46-Addition Energy Spectra of Semiconductor Quantum Dots–In-Ho LEE et al.-S47-Fig. 1.The three confinement potentials are character-ized by the harmonic confinements in meV units of(ωx=ωy,ωz)=(20,45),(10,45),and(4,45),respectively.The sym-bols circles,boxes,and triangles represent the above quantum dots in descending order of x−y confinement strength of po-tentials.electrons as follows:µ(N)=E(N)−E(N−1).(2) From the chemical potential,one can derive the capaci-tance C(N)of the quantum dots,the energy required to add charge e[1,19].C(N)=e2µ(N+1)−µ(N).(3)Therefore,the capacitive energy e2C(N)is easily obtainedby total energy calculations for the three different charge states of system.III.RESULTS AND DISCUSSIONWefirst considered a system with isotropic confine-ment in the x−y plane to investigate the effects of the cylindrical symmetry.We choose theωz=45meV to approximate the thickness of the quasi-two-dimensional electron gas in experiments.From the choice ofωz=45 meV,we can calculate the characteristic length of har-monic oscillator l c=ω−12zand assign the thickness of two-dimensional model electron gas by2×l c≈10.1nm.Fig. 2.The external potential energies are shown in the lower panel and the relative magnitudes of the kinetic(k) and Hartree-exchange-correlation(Hxc)energy with respect to external potential energy are shown in the upper panel. The Hartree-exchange-correlation contribution is larger in the case of N=12than the case of N=2.For the three cases of confinement potentials the same symbol notations are used as in Fig.1.In Fig.1we plot the total energy E(N),chemical po-tentialµ(N),and the capacitive energyµ(N+1)−µ(N) as a function of the number of electrons in the quantum dot.The circles,boxes,and triangles are represent the confinement potential parametersωx=ωy(in units of meV)20,10,and4,respectively.Here,we also show the spin polarization,N↑−N↓N↑+N↓where N↑and N↓are in-tegers which denote the number of electrons with spin up and spin down.For the three values ofωx(=ωy), the total energies increase monotonically with N.The chemical potential abruptly changes at N=3,N=7, and N=13for the case of strong confinement of exter-nal potentials.The electron spins are fully unpolarized for N=2,6,and12,coinciding with the peaks of the capacitive energy of the quantum dot and a completely filled shell.For the cylindrical symmetric two-dimensional quan-tum dot,the simple harmonic potential gives two nonnegative integer quantum numbers for the nonin-teracting single particle energy spectrum say(n x,n y) and form a distinct energy group for each spin {(0,0)},{(1,0),(0,1)},{(1,1),(2,0),(0,2)},...and so on.These energy group form a complete shell structure at N=2,6,and12for the cylindrical two-dimensional quantum dot.The polarizations as a function of the number of electrons satisfy Hund’s rule,i.e.,there is-S48-Journal of the Korean Physical Society,Vol.34,No.,April1999Fig.3.The capacitive energies are calculated for the two anisotropic cases of confinements in meV units of(ωx,ωy)= (10,20)and(ωx,ωy)=(7,10).The circles and boxes represent the(10,20)and(7,10)confinement potentials.maximum spin polarization for partiallyfilled shells.The capacitive energies decrease as the shell index increases, which is consistent with experimentalfindings.[4]The capacitive energy is another version of the ionization en-ergy minus electron affinity in density functional the-ory.The calculated energy gaps of the threefilled shells (N=2,6,and12)are in meV units(17.1,15.0,11.5), (7.8,6.6,5.3),and(2.6,2.1,1.8)for the three confine-ments of model quantum dots in descending order of x−y confinement strengths.The calculated energy gap is de-creasing as the shell index increases from one to three for the three quantum dots considered here.This is mainly due to the electron-electron interactions in quan-tum dots.Thus,we confirmed that both the energy gap and capacitive energy decrease as a function of the shell index.In Fig.2,we plot the kinetic and Hartree-exchange-correlation energies in units of the external po-tential energy to show the relative importance of their contributions to the total energy.We found that neither kinetic nor Hartree-exchange-correlation is greater than external potential energy for the three shells.As shell in-dex increases,the kinetic energy contribution decreases, while the Hartree-exchange-correlation increases.This shows that in the larger dot the electron-electron inter-action is more important.In order to see the effects of asymmetry of confine-ment potentials on the electronic structure weconsideredFig. 4.The capacitive energies and polarizations for the two quantum dots are compared.The solid line represent the nonparabolic confinement potentials,while the dotted line represent the confinement of potential byωx=ωy=4meV. two different anisotropic confinement potentials in thex−y plane characterized by(ωx,ωy)=(10,20)meV and(ωx,ωy)=(7,10)meV for thefixed confinement ofωz=45meV along the z direction.The latter case of con-finement is closely related to the quad-gate planar quan-tum dot structures in experiment.The results includingtotal energy,chemical potential,capacitive energy,andpolarization are shown in Fig. 3.The relative peaks inthe capacitive energy are not much higher than those ofthe cylindrical symmetric dot,partially due to the weak-ness of the confinement potentials.The capacitive energypeaks at N=2,6,and12found for the symmetric con-finement potential are not found for the anisotropic con-finement potentials.The second shell in anisotropic con-finement potentials is formed at N=4due to the sym-metry breaking in x−y coordinate exchange.In thesecases the spin polarization effects are weaker than forthe case of cylindrical symmetric confinement potentials.We can assign electronic states to the two-dimensionalshell without considering interactions between electronsonly for a small number of electrons in quantum dot{(0,0)},{(1,0)},{(0,1),(2,0)},{(1,1),(3,0)},...and so on,for the anisotropic x−y confinement of potentialby(ωx,ωy)=(10,20)meV.We can easily confirm theabove shell structures of the anisotropic quantum dotfrom the peaks in the capacitive energy at N=2,4,8,Addition Energy Spectra of Semiconductor Quantum Dots–In-Ho LEE et al.-S49-and12.In the case of anisotropic confining potential by(ωx,ωy)=(10,20)meV,we found relatively small vari-ations of the addition energy around N=5,6,and7as shown in Fig.3.This is basically a result of thefill-ing procedures of the third shell characterized by nodesin wave functions{(0,1),(2,0)}for each spin.To maxi-mize the exchange interaction spin-parallel configurationis preferred during thefilling of the this shell.Nagarajaet al.[20]pointed out the existence of the‘Coulomb de-generacy’which is related to the lower addition energiesin quad-gate dot for the charging of N=5,6,and7.This is consistent with our results even their calculationsare based on the spin-unpolarized local density approxi-mation.We include the nonparabolic confinement potentials asshown in Eq.(4)to see the effects of the nonparabolicityin confinement.V(r)=a4(x2+y2)2+a6(x2+y2)3+a8(x2+y2)4.(4)The coefficients are set to the values a4=5×10−10meV˚A−4,a6=5×10−16meV˚A−6,and a8=5×10−22meV˚A−8.This potential does not change the basic cylindrical symmetry of the two-dimensional parabolic potentials in Eq.(2).For the case of a small number of electrons and relatively strong lateral confinement potentials,the potential is still close to parabolic.The electronic struc-ture of the large parabolic potentials ofωx=ωy=20 andωx=ωy=10meV withfixedωz=45meV is almost unchanged by the inclusion of the higher order terms in the potential.However,for a weaker parabolic potential,ωx=ωy=4meV,the nonparabolic terms in the potential change spin configurations at N=9and 10.We note that{(2,0),(0,2)}and{(1,1)}have the same energy in the pure harmonic confinement potential, while shell{(2,0),(0,2)}has lower energy than that of the shell{(1,1)}after inclusion of the nonparabolic po-tential.Consequently thefilled shell structures are found at N=2,6,10,and12.In Fig.4,we plot the ca-pacitive energy,polarization,and the external potentials versus the distance from the center of dots.The solid line represents the external potential after inclusion of the nonparabolic part of the potential,while the dotted line represents the parabolic confinement of potential by ωx=ωy=4meV.The nonparabolic terms in the con-finement potential increase the capacitive energy relative to the case of the pure parabolic potential since the non-parabolic terms cause greater confinement.The calcu-lated gaps for thefirst three shells are increased in meV units from(2.6,2.1,1.8)to(3.7,3.6,2.2)after inclusion of the nonparabolic potentials.This is also consistent with the overall increment in the capacitive energy.IV.CONCLUSIONSWe determined the electron-number-dependent capac-itive energy,the energy required to add an additional electron to a quantum dot,by self-consistent solution of the Kohn-Sham equation.We found that in the larger quantum dot the electron-electron interaction is more important than the effect due to quantum confinement. The calculated energy gap in the eigenvalue spectrum and the capacitive energy are a decreasing function of the shell index,and the peak positions of the capacitive energy at the number of electrons N=2,6,and12 for the cylindrical symmetric quantum dot are in good agreement with experimental data.ACKNOWLEDGMENTSWe thank Vivek Rao,Richard M.Martin,and Jean-Pierre Leburton for discussions and supports.=-1000ptREFERENCES[1]M.A.Kastner,Phys.Today46,24(1993).[2]R.C.Ashoori,H.L.Stormer,J.S.Weiner,L.N.Pfeiffer,K.W.Baldwin and K.W.West,Phys.Rev.Lett.71, 613(1993).[3]J.Weis,R.J.Haug,K.v.Klitzing and K.Ploog,Phys.Rev.Lett.71,4019(1993).[4]S.Tarucha, D.G.Austing,T.Honda,R.J.van derHage and L.P.Kouwenhoven,Phys.Rev.Lett.77,3613 (1996).[5]A.Lorke,J.P.Kotthaus and K.Ploog,Phys.Rev.Lett.64,2559(1990).[6]T.Demel,D.Heimann,P.Grambow and K.Ploog,Phys.Rev.Lett.64,788(1990).[7]C.T.Liu,K.Nakamura,D.C.Tsui,K.Ismail,D.A.Antoniadis and H.I.Smith,Appl.Phys.Lett.55,168 (1989).[8]W.Hansen,T.P.Smith,III,K.Y.Lee,J.A.Brum,C.M.Knoedler,J.M.Hong and D.P.Kern,Phys.Rev.Lett.62,2168(1989).[9]M.Macucci,K.Hess and G.J.Iafrate,Phys.Rev.B55,R4579(1997).[10]M.Koskinen,M.Manninen and S.M.Reimann,Phys.Rev.Lett.79,1389(1997).[11]J.R.Chelikowsky,N.Troullier and Y.Saad,Phys.Rev.Lett.72,1240(1994).[12]B.Fornberg and D.Sloan,in Acta Numerica1994,editedby A.Iserles(Cambridge University Press,Cambridge, 1994),pp.203-267.[13]P.Hohenberg and W.Kohn,Phys.Rev.136,864B(1964).[14]R.O.Jones and O.Gunnarsson,Rev.Mod.Phys.61,689(1989).[15]M.C.Payne,M.P.Teter,D.C.Allan,T.A.Arias andJ.D.Joannopoulos,Rev.Mod.Phys.64,1045(1992).[16]D.M.Bylander,L.Kleinman and S.Lee,Phys.Rev.B42,1394(1990).[17]J.P.Perdew,K.Burke and M.Ernzerhof,Phys.Rev.Lett.77,3865(1996).[18]I.-H.Lee and R.M.Martin,Phys.Rev.B56,7197(1997).[19]G.J.Iafrate,K.Hess,J.B.Krieger and M.Macucci,Phys.Rev.B52,10737(1995).-S50-Journal of the Korean Physical Society,Vol.34,No.,April1999 [20]S.Nagaraja,P.Matagne,V.-Y.Thean,J.-P.Leburton,Y.-H.Kim and R.M.Martin,Phys.Rev.B56,15752(1997).。

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Einsteinsscientificachievement,爱因斯坦的科学成就

Einsteinsscientificachievement,爱因斯坦的科学成就

Einsteinsscientificachievement,爱因斯坦的科学成就All his life Albert Einstein was interested in trying to understand the laws of the Universe. He was atheoretical physicist, asking probing questions and carrying out experiments in his mind.In his Special Theory of Relativity, Einstein revolutionised the thinking about space and time. This theory provided the basis for the development of the famous equation E = mc2 which illustrates that matter and energy are interchangeable, and that a small amount of mass is made up of a large amount of energy.The year 1905 is sometimes called Einstein's annus mirabilis (miracle year). In that year he published four outstanding scientific papers:An explanation of the photoelectric effect indicating that light energy came in chunks or quanta.This changed thinking on the nature of light.A discussion of Brownian motion demonstrating the existence of molecules.The nature of space and time.The dynamics of individual moving bodies.These last two formed the basis of Einstein's Special Theory of Relativity and led to that famous equation,E = mc2.In 1921, Einstein was awarded the Nobel Prize for Physics 'for his services to theoretical physics and in particular for his discovery of the law of the 'photoelectric effect'. When he made his delayed acceptance speech in 1923, he ignored the citation and spoke on his theory of relativity.Einstein was a great intellect. He came up with explanationswhich at the time could not be verifiedexperimentally and many of his theories took a long time to be accepted even within the scientific world.Greater credence was attached to his theories as science and technology advanced sufficiently to allow experimentation involving high speed travel and nuclear reactions.It is still difficult for many people to accept or understand his theories since they require thinking beyond normal experiences.Following is an outline of the principles that Einstein developed in a number of scientific fields.Special Theory of RelativityRelativity explains the way an object appears to be relative to an observer. You can understand this if you consider yourself in a car, observing other cars. Imagine you are observing a car travelling at 20 km/h. If your car is stationary, then the other car's speed relative to you is 20 km/h. However if you are travelling alongside the car also doing 20 km/h, then the other car seems to be stationary compared to you. Its speed relative to you is zero! (Ever been at the traffic lights when another car has moved away and you thought you were rolling backwards?)Einstein developed the special theory of relativity by thinking about travelling alongside a light beam at the same speed as the light. He determined that the speed of light is constant, no matter what you are doing or how fast you are travelling, light always travels through empty space at 'the speed of light'. This means that time and length are not absolute, but depend on the relative motion of the object and the observer. If you are stationary, an object that is moving seems to get shorter and heavier, and time slows down for the object. In everyday situations, the slight changes are immeasurable, but they becomeobvious as the speed increases towards the speed of light. As the object travels closer to the speed of light, the length of the object appears closer to zero. Its height stays the same unless it moves up or down —the contraction only happens in the direction of movement. However if you are travelling at the same speed as the object, then everything looks normal! The 'contraction' of moving objects is the contraction of space itself not the object within space.In moving through space, time changes. Space and time are two parts of one whole called spacetime. If you stand still, you are only moving through time. If you move at the speed of light, you move throughspace only and not through time —time stands still. In between, you move partly through one and partly through the other!So the famous twin trip example: Twin A travels round the world at fast pace in a space ship while the twin B stands still. When twin A returns, (s)he will be younger than twin B. Twin B has moved only through time, twin A has moved partly through space and only partly through time —less time than the twin who stayed still.The Special theory of relativity also led to the most famous equation which first appeared in an article by Einstein in 1907. There is a fundamental relationship between rest energy and mass according to the equation E = mc2 where E is the rest energy of an object, m is the mass of the object and c is the velocity of light. The mass of something is a measure of the energy within it; matter and energy are interchangeable, and a small amount of mass is made up of a large amount of energy.In the 1930s nuclear fission was discovered. This gave a wayto release the energy stored in the nuclei of atoms, and the possibility of nuclear weapons was realised.The General Theory of RelativityThe Special Theory applies to objects moving in straight lines at constant speeds. Shortly after its publication, Einstein started work on generalising the theory to include curved paths and accelerating objects, considering the motion that makes planets move in orbit, and the fall of objects to the earth. This led to the equivalence principle which states that in free fall the acceleration and the force due to gravity are equivalent, and the force due to gravity is neutralised, ie in freefall you are weightless.In 1907 Einstein developed the ideas that space and time are not constant, but they change, and that gravity was a property of spacetime rather than being an external force. As he put it: "Matter tells space how to bend and space tells matter how to move." A glimpse into the workings of Einstein's four dimensional spacetime can be gained by imagining the spacetime as a rubber sheet. Stars and planets have mass and cause the sheet close to them to change shape and curve around them. Another massive object coming close will have its motion affected by this deformation of spacetime.The general theory predicted that a light beam passing near a massive object would actually be bent, and by how much. This prediction was supported during a total eclipse of the Sun in May 1919, and again by observations of a total eclipse in Australia in 1922.One of the predictions of the general theory is that the Universe is expanding, giving a basis for the 'big bang' theory of the origins of the Universe. It has also been used to explain black holes and quasars. Quantum TheoryThe nature of light had been debated for many years. Was it made up of particles or waves? Isaac Newton believed light to be made up of particles, Christiaan Huygens stated it was a wave phenomenon, and this was reinforced when Thomas Young demonstrated interference. Later Maxwell suggested and Hertz proved that light was part of the electromagnetic spectrum.In 1905 Einstein reintroduced the particle theory of light. A few years earlier, Max Planck had proposed that energy in an atom occurs in little chunks called quanta. Einstein suggested that light also existed in chunks or quanta. These quanta are now called photons. He concluded this by examining the photoelectric effect – the release of electrons from metals when light shines on them. To make this happen, the light needed to be high frequency (ultraviolet). Low frequency light (red) would not make it happen, no matter how bright the light was. Einstein explained this by thinking of light in terms of photons. Each electron is pushed out from the metal by one photon — as long as that photon has enough energy. Only high frequency light has photons with enough energy. Low frequency light has low energy photons, and no matter how many there are, none of them has enough energy to dislodge an electron.Between 1916 and 1925, Einstein made other contributions to the study of light, including the idea of stimulated emission of radiation – a concept which led to the development of the laser.Unified Field TheoryThe quest to explain gravity and electromagnetism together as aspects of a common phenomenon occupied Einstein's scientific thoughts for much of the last thirty years of his life until he died in 1955. He wanted to provide a basis to explain the Universe in a way other than quantum mechanics whichdescribed activities in terms of probabilities. He did not succeed. Since then the weak and strong nuclear forces have been discovered.Electromagnetism and the nuclear forces can be explained using quantum mechanics, and the search continues for a theory to explain everything!。

量子垒高度对深紫外LED 调制带宽的影响

量子垒高度对深紫外LED 调制带宽的影响

第43卷㊀第1期2022年1月发㊀光㊀学㊀报CHINESE JOURNAL OF LUMINESCENCEVol.43No.1Jan.,2022㊀㊀收稿日期:2021-10-25;修订日期:2021-11-11㊀㊀基金项目:国家重点研发计划(2017YFB0404104);国家自然科学基金(61974139);北京自然科学基金(4182063)资助项目Supported by National Key R&D Program of China (2017YFB0404104);National Natural Science Foundation of China (61974139);Beijing Natural Science Foundation(4182063)文章编号:1000-7032(2022)01-0001-07量子垒高度对深紫外LED 调制带宽的影响郭㊀亮1,2,郭亚楠1,2,羊建坤1,2,闫建昌1,2,王军喜1,2,魏同波1,2∗(1.中国科学院半导体研究所半导体照明研发中心,北京㊀100083;2.中国科学院大学材料与光电研究中心,北京㊀100049)摘要:AlGaN 基深紫外LED 由于具有高调制带宽和小芯片尺寸,在紫外光通信领域受到越来越多的关注㊂本研究通过改变生长AlGaN 量子垒层的Al 源流量,生长了三种具有不同量子垒高度的深紫外LED,研究了量子垒高度对深紫外LED 光电特性和调制特性的影响㊂研究发现,随着量子垒高度的增加,深紫外LED 的光功率出现先增加后减小的趋势,量子垒中Al 组分为55%的深紫外LED 的光功率相比50%和60%的深紫外LED 提升了近一倍㊂载流子寿命则出现先减小后增大的趋势,且发光峰峰值波长逐渐蓝移㊂APSYS 模拟表明,随着量子垒高度增加,量子垒对载流子的束缚能力增强,电子空穴波函数空间重叠增加,载流子浓度和辐射复合速率增加;但进一步增加量子垒高度又会由于电子泄露,空穴浓度降低,从而辐射复合速率降低㊂量子垒中Al 组分为55%的深紫外LED 的-3dB 带宽达到94.4MHz,高于量子垒Al 组分为50%和60%的深紫外LED㊂关㊀键㊀词:紫外光通信;深紫外发光二极管;多量子阱层;调制带宽;发光功率中图分类号:TN383+.1;TN929.12㊀㊀㊀文献标识码:A㊀㊀㊀DOI :10.37188/CJL.20210331Effect of Barrier Height on Modulation Characteristics ofAlGaN-based Deep Ultraviolet Light-emitting DiodesGUO Liang 1,2,GUO Ya-nan 1,2,YANG Jian-kun 1,2,YAN Jian-chang 1,2,WANG Jun-xi 1,2,WEI Tong-bo 1,2∗(1.Research and Development Center for Semiconductor Lighting Technology ,Institute of Semiconductors ,Chinese Academy of Sciences ,Beijing 100083,China ;2.Center of Materials Science and Optoelectronics Engineering ,University of Chinese Academy of Sciences ,Beijing 100049,China )∗Corresponding Author ,E-mail :tbwei @Abstract :AlGaN-based deep ultraviolet LED has attracted more and more attention in ultravioletcommunication due to its high modulation bandwidth and small chip size.In this study,AlGaN-based deep ultraviolet LEDs with varied Al composition of 50%,55%,60%in quantum barriers are fabricated.The effect of barrier height on the photoelectric and modulation characteristics of deep ultraviolet LEDs is studied.It is found that the optical power and external quantum efficiency (EQE)of the deep ultraviolet LED increase first and then decreased,and carrier lifetime decreases first and then increases as the quantum barrier height increases.The peak wavelength of the spectra shows a blue-shift.APSYS simulation revealed that the spacial overlap between the wave function of electron and hole is enhanced as Al composition increases.But further increase on barrier height will lead to current leakage which reduces the radiation recombination rate and carrier density in . All Rights Reserved.2㊀发㊀㊀光㊀㊀学㊀㊀报第43卷quantum well layer.The-3dB bandwidth of deep ultraviolet LED with55%Al composition inquantum barrier is measured to be94.4MHz,higher than those with50%and60%Al composition in quantum barrier.Key words:ultraviolet communication;deep ultraviolet light-emitting diodes;multiple-quantum-well layer;modula-tion bandwidth;optical power1㊀引㊀㊀言随着深紫外LED和日盲探测器的发展,紫外光通信受到越来越多的关注㊂紫外光通信利用紫外光传输信号,该信号可以被漂浮在空气中的微粒和气溶胶等散射和反射,实现非视距通信[1-2]㊂紫外光通信中使用的紫外光也称为日盲紫外光,它在光谱中位于200~280nm之间[3-4]㊂当太阳辐射穿过大气层时,会被空气中的水蒸气㊁二氧化碳㊁氧气㊁臭氧㊁悬浮颗粒和其他气体分子强烈散射㊁吸收或反射,从而导致太阳光谱不连续㊂在所有分子和粒子中,仅占大气0.01%~0.1%的臭氧在紫外光谱中具有很强的吸收带,从而使得到达地表的太阳光中日盲紫外光含量极少,这则为紫外光通信提供了低背景噪声的通信环境[5]㊂同时,紫外光通信还具有高保密性㊁无需频段许可㊁抗干扰能力强等优势,这使得紫外光通信在军事领域具有重要应用价值㊂紫外光源作为紫外光通信系统中重要的组成部分,其光功率决定了紫外光通信系统的传输距离,而其带宽决定了通信速率的上限[6]㊂紫外光通信系统中最常用的三种光源包括气体放电灯㊁激光器和LED㊂气体放电灯制造成本低㊁输出功率大,激光器的光线相干性高㊁单色性好㊁发散性低,然而这两种光源都存在体积大㊁功耗大㊁调制速率低的缺点㊂AlGaN基LED由于具有更高的调制带宽和更小的芯片尺寸,在紫外光通信中得到了越来越广泛的应用[7-9]㊂近年来,越来越多的研究团体开始研究基于深紫外LED作为光源的紫外光通信㊂Alkhazragi等基于商用发光波长为279nm的深紫外LED实现了1m链路上通信速率为2.4Gbps的紫外光通信系统,测得调制带宽为170MHz[10]㊂2018年,Kojima等基于调制带宽为153MHz㊁发光波长为280nm的深紫外LED,在1.5m链路上实现了1.6Gbps的通信速率[11]㊂2019年,He等制备了AlGaN基262nm深紫外Micro-LED阵列,在71 A/cm2电流密度下,测得调制带宽达到了438 MHz,在0.3m链路上实现了高达1.1Gbps的数据传输速率[12]㊂Zhu等制备了100μm深紫外Micro-LED,在400A/cm2电流密度下,测得调制带宽为452.53MHz[13]㊂尽管AlGaN基深紫外LED在紫外光通信中已经得到了广泛应用,但目前大部分研究仍集中在LED芯片工艺的改进上㊂关于深紫外LED外延结构对调制特性的影响的研究几乎处于空白状态㊂本研究通过改变生长AlGaN量子垒层时的Al源流量,控制了量子垒中Al组分分别为50%㊁55%和60%,生长了三种具有不同量子垒高度的深紫外LED,研究了量子垒高度对深紫外LED光电特性和调制特性的影响㊂并借助APSYS模拟和时间分辨光致发光光谱对实验结果进行了深入分析㊂2㊀实㊀㊀验2.1㊀样品制备实验中首先在c面蓝宝石衬底上生长1μm 厚的AlN缓冲层,然后在1130ħ下沉积20个周期的AlN(2nm)/Al0.6Ga0.4N(2nm)超晶格层㊂然后依次生长1.8μm厚Si掺杂浓度为3ˑ1018 cm-3的n-Al0.61Ga0.39N层,5个周期Al0.4Ga0.6N图1㊀紫外外延片结构示意图Fig.1㊀Wafer structure of ultraviolet LED. All Rights Reserved.㊀第1期郭㊀亮,等:量子垒高度对深紫外LED调制带宽的影响3㊀(3nm)/Al0.5/0.55/0.6Ga0.5/0.45/0.4N(12nm)多量子阱层,50nm厚的Mg掺杂p-Al0.6Ga0.4N电子阻挡层,30nm厚p-Al0.5Ga0.5N层以及150nm厚Mg 掺杂浓度为1ˑ1018cm-3的p-GaN层㊂随后,在800ħ氮气气氛下退火20min以激活Mg受主㊂对生长得到的深紫外LED外延片使用标准紫外流片工艺,制备了倒装结构深紫外LED,芯片尺寸为250μmˑ550μm,图1为外延片结构示意图㊂2.2㊀样品表征LED光功率测试采用的是远方光电公司HAAS-2000高精度快速光谱辐射计,该设备光谱范围为200~2550nm㊂光致发光光谱测试采用215nm紫外激光器作为激发光源,激光功率为31 mW,所用光栅线密度为1200l/mm,测试波长范围为240~320nm,步长为0.2nm,积分时间为1.0s,测试环境温度为295K㊂带宽测试系统采用安捷伦E5061B型网络分析仪,其扫描频率范围为5Hz~3GHz,可覆盖氮化物LED的频率响应范围㊂直流偏置源采用Keithley2420作为电流源,该电流源最大输出电流为3A,最大输出电压为60 V㊂紫外探测器采用Thorlabs公司APD430A2/M 型硅基雪崩探测器,可探测波长范围是200~ 1000nm,可覆盖整个UVC波段㊂图2为实验中使用的带宽测试系统示意图㊂图2㊀带宽测试系统示意图Fig.2㊀Diagram of bandwidth testing system3㊀结果与讨论3.1㊀电致发光光谱图3是3种不同量子垒高度深紫外LED的EL测试结果㊂在20mA电流下,量子垒中Al组分为50%㊁55%和60%的深紫外LED的峰值波长分别为280.4,276.5,274.0nm,可以看出随着量子垒中Al组分的增加,深紫外LED的峰值波长逐渐蓝移㊂这是因为随着量子垒高度增加,量子阱对电子空穴的束缚能力增加,电子和空穴波函数的空间分离减小,量子限制效应增强,从而导致蓝移㊂同时可以看出,随着电流从20mA增加到100mA,深紫外LED的峰值波长逐渐红移㊂Al组分为50%的深紫外LED的峰值波长红移了1.2nm,Al组分为55%的深紫外LED的峰值波长红移了2nm,Al组分为60%的深紫外LED的峰值波长红移了1nm㊂同时LED的发光峰半高宽也逐渐展宽,Al组分为50%的深紫外LED的半高宽从9.9nm展宽到10.8nm,Al组分为55%的深紫外LED的半高宽从11.3nm展宽到12nm, Al组分为60%的深紫外LED的半高宽从10.7nm图3㊀量子垒中Al组分为50%(a)㊁55%(b)㊁60%(c)的深紫外LED的EL光谱随电流的变化㊂Fig.3㊀EL spectra of ultraviolet LED with Al composition of 50%(a),55%(b),60%(c)in quantum barrierunder varied currents.. All Rights Reserved.4㊀发㊀㊀光㊀㊀学㊀㊀报第43卷展宽到11.7nm㊂这是因为根据焦耳定律,随着电流增加,单位时间内产生的热量增加㊂根据能带宽度和温度的关系,深紫外LED的能带宽度会随着温度升高而线性减小,从而导致发光波长红移[14]㊂热量的增加还会导致量子限制斯塔克效应增强,从而导致半高宽增加[15]㊂3.2㊀光功率对3种不同量子垒高度的深紫外LED芯片进行光电测试,得到不同测试电流下的光功率测试结果,如图4所示㊂可以看出光功率随着量子图4㊀量子垒中Al组分为50%㊁55%㊁60%的深紫外LED 的光功率随电流的变化㊂Fig.4㊀Optical power of ultraviolet LED with Al composition of50%,55%,60%in quantum barrier under var-ied currents.垒高度的增加,出现先增大后减小的趋势㊂这是因为随着量子垒高度的增加,量子阱对电子空穴的束缚能力增强,使得电子空穴浓度增加,从而导致光功率增大㊂但进一步增加量子垒高度,会导致电子阻挡层对过冲电子的束缚能力减弱,过冲电子与p型区的空穴复合,导致空穴电流减小,最终导致光功率降低[16]㊂3.3㊀APSYS模拟我们使用APSYS软件对不同量子垒高度的AlGaN基深紫外LED的能带结构进行了模拟㊂模拟时,深紫外LED的注入电流为62.5mA,器件尺寸为250μmˑ250μm,从下到上为蓝宝石衬底㊁AlN缓冲层㊁n-Al0.55Ga0.45N层㊁有源区㊁p-Al0.65Ga0.35N电子阻挡层㊁p-Al0.55Ga0.45N层㊁p-GaN层㊂有源区由5个量子阱层和6个量子垒层组成,阱层为2nm厚的Al0.45Ga0.55N,垒层为10nm厚的Al0.5/0.55/0.6Ga0.5/0.45/0.4N㊂不同量子垒高度的AlGaN基的深紫外LED的能带结构如图5(a)㊁(b)㊁(c)所示㊂可以看出,随着量子垒高度的增加,电子和空穴的波函数空间分离逐渐减小,我们进一步对其辐射复合速率进行了模拟,模拟结果如图5(d)所示㊂辐射复合速率随着量子垒高度出现了先增加后减小的趋势㊂这是因为随着量子垒高度的增加,量子垒对载流子的束缚作图5㊀量子垒中Al组分为50%(a)㊁55%(b)㊁60%(c)的深紫外LED的能带结构示意图;(d)量子垒中Al组分为50%㊁55%和60%的深紫外LED的辐射复合速率分布示意图㊂Fig.5㊀Band structure of ultraviolet LED with Al composition of50%(a),55%(b),60%(c)in quantum barrier.(d)Ra-diation recombination rate of ultraviolet LED with Al composition of50%,55%and60%in quantum barrier.. All Rights Reserved.㊀第1期郭㊀亮,等:量子垒高度对深紫外LED调制带宽的影响5㊀用增加,使得量子阱内的载流子浓度增大,同时由于电子和空穴的空间波函数重叠增加,辐射复合所占的比重也会增加,从而辐射复合速率增大㊂但进一步增加量子垒高度又会由于电子泄漏,从而导致辐射复合速率减小[17-18]㊂3.4㊀时间分辨光致发光光谱我们对不同量子垒高度的深紫外LED进行了时间分辨光致发光光谱(TRPL)测试㊂不同量子垒高度深紫外LED的TRPL测试结果如图6所示㊂通过对曲线的衰减部分使用以下公式进行双衰减指数拟合[19]:I(t)=A1e-ττ1+A2e-ττ2,(1)其中τ1满足1/τ1=1/τnr+1/τ2,τnr为非辐射复合载流子寿命,τ2为辐射复合载流子寿命㊂量子垒中Al组分为50%㊁55%和60%的深紫外LED的载流子寿命分别为432,276,352ps㊂可以看出载流子寿命随着量子垒中Al组分的增加出现先减小后增大的趋势㊂图6㊀量子垒中Al组分为50%㊁55%㊁60%的深紫外LED的TRPL光谱随电流的变化㊂Fig.6㊀TRPL spectra of ultraviolet LED with Al composition of50%,55%,60%in quantum barrier.热平衡状态下,pn结中的载流子复合速率可以由以下公式得到:R=B(N0+Δn)(P0+Δn)-BN0P0,(2)其中B为复合常数,N0为电子浓度,P0为空穴浓度,Δn为过剩载流子浓度㊂经整理后可以得到如下公式:R=B(N0+P0+Δn)Δn,(3)由于在p型区中,P0远大于N0,因此上述公式可以进一步简化为:R=B(P0+Δn)Δn,(4)载流子寿命可以由以下公式表示:τ=Δn R=1B(P0+Δn),(5)由于载流子寿命和辐射复合速率成反比,随着量子垒高度增加,量子垒对载流子的束缚作用增强,辐射复合速率增加,载流子寿命因此减小㊂但进一步增加量子垒高度又会由于电子泄漏,导致辐射复合速率减小,载流子寿命增加[20]㊂3.5㊀调制带宽测试在60mA电流下,测试得到了深紫外LED的频率响应结果如图7所示㊂量子垒中Al组分为50%㊁55%和60%的深紫外LED的-3dB带宽分别为75.0,94.4,82.0MHz㊂深紫外LED的调制带宽随着量子垒高度的增加,出现了先增加后减小的趋势㊂LED的调制带宽主要受到载流子寿命和RC 时间常数决定,并且对于常规尺寸LED,其主要受载流子辐射复合寿命决定㊂载流子辐射复合寿命决定了发光强度在交变信号下的上升和下降时间,也决定了光功率随交变信号变化反应的快慢㊂两者之间满足以下关系[21]:f-3dB=12πτBJ qd,(6)其中f-3dB为LED的-3dB带宽,B为双分子复合系数,J为电流密度,q为元电荷,d为有源区厚度㊂载流子寿命越短,则光子随外电流变化反应的速度越快,从而调制带宽越高㊂这一结果也与3.4中载流子寿命的结果相吻合㊂图7㊀量子垒中Al组分为50%㊁55%㊁60%的深紫外LED 的频率响应图㊂Fig.7㊀Frequency response of ultraviolet LED with Al com-position of50%,55%,60%in quantum barrier. 4㊀结㊀㊀论本文研究了量子垒高度对深紫外LED光电. All Rights Reserved.6㊀发㊀㊀光㊀㊀学㊀㊀报第43卷特性和调制特性的影响,制备了3种具有不同量子垒高度的深紫外LED㊂研究发现,随着量子垒高度的增加,深紫外LED的光功率和外量子效率出现先增加后减小的趋势,载流子寿命则出现先减小后增大的趋势,EL光谱发光峰峰值波长逐渐蓝移㊂最后,我们使用基于网络分析仪的带宽测试系统对不同量子垒高度的深紫外LED进行了带宽测试,测得量子垒中Al组分为50%㊁55%和60%的深紫外LED的-3dB带宽分别为75.0, 94.4,85.0MHz㊂本文专家审稿意见及作者回复内容的下载地址: /thesisDetails#10.37188/ CJL.20210331.参㊀考㊀文㊀献:[1]UAN R Z,MA J S.Review of ultraviolet non-line-of-sight communication[J].China Commun.,2016,13(6):63-75.[2]DROST R J,SADLER B M.Survey of ultraviolet non-line-of-sight communications[J].Semicond.Sci.Technol.,2014,29(8):084006-1-11.[3]SHAW G A,NISCHAN M L,IYENGAR M A,et al.NLOS UV communication for distributed sensor systems[C].Pro-ceedings of SPIE4126,Integrated Command Environments,San Diego,CA,United States,2000:83-96.[4]KHAN A,BALAKRISHNAN K,KATONA T.Ultraviolet light-emitting diodes based on group three nitrides[J].Nat.Photonics,2008,2(2):77-84.[5]VAVOULAS A,SANDALIDIS H G,CHATZIDIAMANTIS N D,et al.A survey on ultraviolet C-band(UV-C)communica-tions[J].IEEE Commun.Surv.Tutor.,2019,21(3):2111-2133.[6]GUO L,GUO Y N,WANG J X,et al.Ultraviolet communication technique and its application[J].J.Semicond.,2021,42(8):081801.[7]ZHANG H,HUANG C,SONG K,et positionally gradedⅢ-nitride alloys:building blocks for efficient ultraviolet op-toelectronics and power electronics[J].Rep.Prog.Phys.,2021,84(4):044401-1-28.[8]HUANG C,ZHANG H C,SUN H D.Ultraviolet optoelectronic devices based on AlGaN-SiC platform:towards monolithicphotonics integration system[J].Nano Energy,2020,77:105149.[9]YU H B,MEMON M H,WANG D H,et al.AlGaN-based deep ultraviolet micro-LED emitting at275nm[J].Opt.Lett.,2021,46(13):3271-3274.[10]ALKHAZRAGI O,HU F C,ZOU P,et al.Gbit/s ultraviolet-C diffuse-line-of-sight communication based on probabilistical-ly shaped DMT and diversity reception[J].Opt.Express,2020,28(7):9111-9122.[11]KOJIMA K,YOSHIDA Y,SHIRAIWA M,et al.1.6-Gbps LED-based ultraviolet communication at280nm in direct sun-light[C].Proceedings of the2018European Conference on Optical Communication,Rome,Italy,2018:1-3.[12]HE X Y,XIE E Y,ISLIM M S,et al.1Gbps free-space deep-ultraviolet communications based onⅢ-nitride micro-LEDsemitting at262nm[J].Photonics Res.,2019,7(7):B41-B47.[13]ZHU S J,QIU P J,QIAN Z Y,et al.2Gbps free-space ultraviolet-C communication based on a high-bandwidth micro-LEDachieved with pre-equalization[J].Opt.Lett.,2021,46(9):2147-2150.[14]BAUMGARTNER H,VASKURI A,KÄRHÄP,et al.Temperature invariant energy value in LED spectra[J].Appl.Phys.Lett.,2016,109(23):231103-1-4.[15]WANG T,NAKAGAWA D,WANG J,et al.Photoluminescence investigation of InGaN/GaN single quantum well and multi-ple quantum wells[J].Appl.Phys.Lett.,1998,73(24):3571-3573.[16]REN Z J,YU H B,LIU Z L,et al.Band engineering ofⅢ-nitride-based deep-ultraviolet light-emitting diodes:a review[J].J.Phys.D:Appl.Phys.,2020,53(7):073002.[17]GUTTMANN M,HÖPFNER J,REICH C,et al.Effect of quantum barrier composition on electro-optical properties of Al-GaN-based UVC light emitting diodes[J].Semicond.Sci.Technol.,2019,34(8):085007-1-6.[18]王玮东,楚春双,张丹扬,等.俄歇复合㊁电子泄漏和空穴注入对深紫外发光二极管效率衰退的影响[J].发光学报,2021,42(7):897-903.WANG W D,CHU C S,ZHANG D Y,et al.Impact of auger recombination,electron leakage and hole injection on efficiency . All Rights Reserved.㊀第1期郭㊀亮,等:量子垒高度对深紫外LED 调制带宽的影响7㊀droop for DUV LEDs [J].Chin.J.Lumin .,2021,42(7):897-903.(in Chinese)[19]ZHUANG Z,GUO X,LIU B,et al.Great enhancement in the excitonic recombination and light extraction of highly ordered InGaN /GaN elliptic nanorod arrays on a wafer scale [J].Nanotechnology ,2016,27(1):015301.[20]刘恩科,朱秉升,罗晋生.半导体物理学[M].第7版.北京:电子工业出版社,2008.LIU E K,ZHU B S,LUO J S.The Physics of Semiconductors [M].7th ed.Beijing:Publishing House of Electronics Indus-try,2008.(in Chinese)[21]ZHU S C,YU Z G,ZHAO L X,et al.Enhancement of the modulation bandwidth for GaN-based light-emitting diode by sur-face plasmons [J].Opt.Express ,2015,23(11):13752-13760.郭亮(1996-),男,江西吉安人,硕士研究生,2018年于合肥工业大学获得学士学位,主要从事通信用深紫外LED 的研究㊂E-mail:guoliang18@semi.ac.cn魏同波(1978-),男,山东潍坊人,博士,研究员,2007年于中国科学院半导体研究所获得博士学位,主要从事宽禁带半导体材料生长及器件制备的研究㊂E-mail:tbwei@. All Rights Reserved.。

《分析化学》专业英语阅读材料06

《分析化学》专业英语阅读材料06

《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 ][][=。

半导体一些术语的中英文对照

半导体一些术语的中英文对照

半导体一些术语的中英文对照离子注入机ion implanterLSS理论Lindhand Scharff and Schiott theory 又称“林汉德-斯卡夫-斯高特理论”。

沟道效应channeling effect射程分布range distribution深度分布depth distribution投影射程projected range阻止距离stopping distance阻止本领stopping power标准阻止截面standard stopping cross section 退火annealing激活能activation energy等温退火isothermal annealing激光退火laser annealing应力感生缺陷stress-induced defect择优取向preferred orientation制版工艺mask-making technology图形畸变pattern distortion初缩first minification精缩final minification母版master mask铬版chromium plate干版dry plate乳胶版emulsion plate透明版see-through plate高分辨率版high resolution plate, HRP超微粒干版plate for ultra-microminiaturization 掩模mask掩模对准mask alignment对准精度alignment precision光刻胶photoresist又称“光致抗蚀剂”。

负性光刻胶negative photoresist正性光刻胶positive photoresist无机光刻胶inorganic resist多层光刻胶multilevel resist电子束光刻胶electron beam resistX射线光刻胶X-ray resist刷洗scrubbing甩胶spinning涂胶photoresist coating后烘postbaking光刻photolithographyX射线光刻X-ray lithography电子束光刻electron beam lithography离子束光刻ion beam lithography深紫外光刻deep-UV lithography光刻机mask aligner投影光刻机projection mask aligner曝光exposure接触式曝光法contact exposure method接近式曝光法proximity exposure method光学投影曝光法optical projection exposure method 电子束曝光系统electron beam exposure system分步重复系统step-and-repeat system显影development线宽linewidth去胶stripping of photoresist氧化去胶removing of photoresist by oxidation等离子［体］去胶removing of photoresist by plasma 刻蚀etching干法刻蚀dry etching反应离子刻蚀reactive ion etching, RIE各向同性刻蚀isotropic etching各向异性刻蚀anisotropic etching反应溅射刻蚀reactive sputter etching离子铣ion beam milling又称“离子磨削”。