GaAlAs／GaAs量子阱结构的光致发光研究

阐述了用ＭＯＣＶＤ生长的ＧａＡｌＡｓ／ＧａＡｓ梯度折射率分别限制量子阱结构及其光学性质。样品经高分辨率光致发光（ＰＬ）测试显示,在１０Ｋ下对于８ｎｍ的单量子阱,通过激发产生的荧光谱半峰宽（ＦＷＨＭ）为６．２ｎｍ,同时具有较高的强度。表明量子阱结构具有陡峭的界面;另外还观察到,Ｘ（ｅ－ｈｈ）峰值位置相对于激发能级的移动。测试结果表明,样品质量符合设计要求,结果令人满意。     

(CdSe)1(ZnSe)3/ZnSe短周期超晶格多量子阱的共振Ramam谱

在(CdSe)₁(ZnSe)₃/ZnSe短周期超晶格多量子阱中,根据一维线性链模型计算的结果与实验结果的比较表明,我们在不同的共振条件下分别观察到了来自多量子阱的阱中和垒中ZnSe限制纵光学声子模的Raman散射。与GaAs/AlAs量子阱的偏振选择定则不同,在共振条件下,我们在两种偏振配置下都观察到了阱中ZnSe限制模LO₁,并认为这种不同可能来源于样品特殊的电子子带结构和光学声子行为。 关键词：     

Linear and nonlinear intersubband optical absorption in symmetric double semi-parabolic quantum wells

The linear and the nonlinear intersubband optical absorption in the symmetric double semi-parabolic quantum wells are investigated for typical GaAs/AlxGa1−xAs. Energy eigenvalues and eigenfunctions of an electron confined in finite potential double quantum wells are calculated by numerical methods from Schrödinger equation. Optical properties are obtained using the compact density matrix approach. In this work, the effects of the barrier width, the well width and the incident optical intensity on the optical properties of the symmetric double semi-parabolic quantum wells are investigated. Our results show that not only optical incident intensity but also structure parameters such as the barrier and the well width really affect the optical characteristics of these structures.     

Linear and nonlinear intersubband optical absorption coefficients and refractive index changes in symmetric double semi-V-shaped quantum wells

In this study, the changes in the refractive index and intersubband optical absorption coefficients in symmetric double semi-V-shaped quantum wells are investigated theoretically. The energy levels and the envelope wave functions of an electron confined in finite potential double semi-V-shaped quantum wells are calculated within the effective-mass approximation framework. The analytical expressions of the refractive index and intersubband optical absorption coefficients are obtained using the compact density matrix approach. The effects of the incident optical intensity and structure parameters, such as the barrier width, confinement potential and the well width, on the optical properties of the double semi-V-shaped quantum wells are investigated. The numerical results show that both the incident optical intensity and structure paremeters have a great effect on the optical characteristics of these structures.     

Charge carrier recombination mechanisms in Sb-containing quantum well laser structures

The dynamics of interband luminescence in structures with InGaAsSb-based quantum wells and barriers of different types was studied at different temperatures and excitation levels. The lifetime of optically injected charge carriers in quantum wells at different temperatures and optical excitation levels was determined. An increased recombination rate in structures with deep electron quantum wells was discovered; it is associated with the occurrence of resonance Auger recombination. It was concluded that the application of quinary solid solutions as barriers in laser structures for a 3—4 fum wavelength range is to be preferred.     

Coulomb enhancement of the third-order nonlinearities in the mesoscopic semiconductor structures

The prospects for the enhancement of the third-order optical nonlinearity in the mesoscopic semiconductor structures: quantum wells, wires, and boxes are analyzed. It is shown, that if the structures are designed in such a way that the ground state and the excited states wavefunctions are spatially separated, then the electrostatic Coulomb interactions will result in the enhancement of the optical nonlinearity. The enhancement factor has been analyzed for the structures of different shapes and material compositions. It was found that the possible enhancement factor ranges from 2 for quantum wells to 10 for quantum wires and boxes.     

Optical gain and threshold properties of strained InGaAlAs/AlGaAs quantum wells for 850-nm vertical-cavity surface-emitting lasers

The valence subband structures, optical gain spectra, transparency carrier densities, and transparency radiative current densities of different compressively strained InGaAlAs quantum wells with Al_0.3Ga_0.7As barriers are systematically investigated using a 6 × 6 k · p Hamiltonian including the heavy hole, light hole, and spin-orbit splitting bands. The results of numerical calculations show that the maximum optical gain, transparency carrier densities, transparency radiative current densities, and differential gain of InGaAlAs quantum wells can be enhanced by introducing more compressive strain in quantum wells. However, further improvement of the optical properties of InGaAlAs quantum wells becomes minimal when the compressive strain is higher than approximately 1.5%. The simulation results suggest that the compressively strained InGaAlAs quantum wells are of advantages for application in high-speed 850-nm vertical-cavity surface-emitting lasers.     

Impact of optical antenna and plasmonics on infrared imagers

The advent of nanophotonics allows devising and fabricating optical antenna as the advanced optical structures that can enhance light–matter interaction in quantum structures such as quantum wells. Improving infrared photodetector performance is discussed theoretically in this paper. We also investigate our recent demonstration of optical antenna integrated on quantum well infrared photodetector which improves the performance of the detector as can be evidence in responsivity of the detector.     

InGaN/GaN laser diode characterization and quantum well number effect

The effect of quantum well number on the quantum efficiency and temperature characteristics of In- GaN/GaN laser diodes （LDs） is determined and investigated. The 3-nm-thick In0.13Ca0.87N wells and two 6-am-thick GaN barriers are selected as an active region for Fabry-Perot （FP） cavity waveguide edge emitting LD. The internal quantum efficiency and internal optical loss coefficient are extracted through the simulation software for single, double, and triple InGaN/GaN quantum wells. The effects of device temperature on the laser threshold current, external differential quantum efficiency （DQE）, and output wavelength are also investigated. The external quantum efficiency and characteristic temperature are improved significantly when the quantum well number is two. It is indicated that the laser structures with many quantum wells will suffer from the inhomogeneity of the carrier density within the quantum well itself which affects the LD performance.     

有机多层量子阱结构的光致发光特性的研究

采用多源高真空有机分子束沉积系统(OMBDs),将两种有机小分子材料PBD和Alq₃以交替生长的方式,制备了不同厚度的PBD/Alq₃有机多层量子阱结构(OMQWs), 并利用电化学循环伏安法和光吸收分别测定了PBD和Alq₃的最低空分子轨道(LUMO)和最高占据分子轨道(HOMO)。该结构类似于无机半导体中的Ⅰ型量子阱结构,PBD层作为势垒层,Alq3层作为势阱层和发光层,并进行了小角X射线衍射(XRD)的测量。利用荧光光谱研究了OMQWs光致发光(PL)特性,得到随着阱层厚度的降低,光致发光的峰位将蓝移;同时随垒层厚度的减小,PBD的发光峰逐渐消失。利用量子阱结构可以使PBD的能量有效的传递给Alq₃,从而增强Alq₃的发光。     

Boundary conditions of continuum states in characterizing photocurrent of GaAs/AlGaAs quantum well infrared photodetector

We study the optical transition between bound-to-continuum states in a GaAs/AlGaAs multiple quantum well infrared photodetector (QWIP) by analyzing three possible boundary conditions for the continuum states. Comparing with experimental results, it has been suggested that the Bloch-state boundary conditions are proper for continuum states in the QWIPs consisting of multiple quantum wells and the fine structures in the responsivity spectrum result from the energy dispersion relationship of the multiple quantum wells.     

Effect of normal and reversed polarizations on optical characteristics of ultraviolet-violet InGaN laser diodes

The optical characteristics of ultraviolet-violet InGaN laser diodes with different numbers of quantum wells under normal and reversed polarizations are numerically investigated. For the laser structures under normal polarization, the lowest threshold current is obtained when the number of quantum wells is two in the spectral range of 380-408 nm. For the laser structures under reversed polarization, the single quantum-well laser structure possesses the lowest threshold current. The simulation results suggest that the physical origin for these phenomena is caused by the sufficiently suppressed electron and hole leakage currents when the laser diode is under reversed polarization.     

半导体微结构物理效应及其应用讲座第三讲半导体的激子效应及其在光电子器件中的应用

人们对半导体中的电子空穴对在库仑互作用下形成的激子态及其有关的物理性质进行了深入研究.激子效应对半导体中的光吸收、发光、激射和光学非线性作用等物理过程具有重要影响,并在半导体光电子器件的研究和开发中得到了重要的应用.与半导体体材料相比,在量子化的低维电子结构中,激子的束缚能要大得多,激子效应增强,而且在较高温度或在电场作用下更稳定.这对制作利用激子效应的光电子器件非常有利.近年来量子阱、量子点等低维结构研究获得飞速的进展,已大大促进了激子效应在新型半导体光源和半导体非线性光电子器件领域的应用.     

Photoluminescence and secondary ion mass spectroscopy characterization of GaAs-AlGaAs quantum wells grown on GaAs (1 0 0) substrates with different surface treatments

GaAs (1 0 0) substrates prepared in a quartz chamber under a H₂/As₄ flux, and then exposed to air were used for the subsequent growth of GaAs-AlGaAs single quantum wells by molecular beam epitaxy. The substrates prepared by this method showed atomically flat surfaces corroborated by atomic force microscopy analysis. Quantum wells grown directly on these substrates without a GaAs buffer layer exhibited narrow and intense photoluminescence peaks, an indication of a high quality material. The secondary ion mass spectroscopy analysis showed oxygen and carbon traces on the first AlGaAs barrier layer grown after air exposure with no effects on the quantum wells optical emissions. From the results we conclude that the prepared GaAs surfaces are useful for the epitaxial growth of high quality quantum structures.     

纤锌矿InGaN staggered量子阱中的激子态和光学性质

本文将基于有效质量近似下的变分法,理论研究了纤锌矿InGaN/GaN staggered 量子阱中的激子态和光学性质。数值结果显示了InGaN量子阱中的量子尺寸和staggered受限垒对束缚于量子阱中的激子态和光学性质有着明显地影响。当阱宽增加时,量子受限效应减弱,激子结合能降低, 带间发光波长增加。另一方面,当量子阱中staggered受限势增加时,量子受限效应增强,激子结合能升高,带间发光波长降低。本文的理论结果证明了可以通过调节staggered垒高和量子尺寸来调控纤锌矿InGaN staggered 量子阱中的激子态和光学性质。     

纤锌矿InGaN staggered量子阱中的激子态和光学性质

本文将基于有效质量近似下的变分法,理论研究了纤锌矿InGaN/GaN staggered量子阱中的激子态和光学性质.数值结果显示了InGaN量子阱中的量子尺寸和staggered受限垒对束缚于量子阱中的激子态和光学性质有着明显的影响.当阱宽增加时,量子受限效应减弱,激子结合能降低,带间发光波长增加.另一方面,当量子阱中staggered受限势增加时,量子受限效应增强,激子结合能升高,带间发光波长降低.本文的理论结果证明了可以通过调节staggered垒高和量子尺寸来调控纤锌矿InGaN staggered量子阱中的激子态和光学性质.     

Growth and properties of wide spectral white light emitting diodes

Wide spectral white light emitting diodes have been designed and grown on a sapphire substrate by using a metal-organic chemical vapor deposition system. Three quantum wells with blue-light-emitting, green-light-emitting and red-light-emitting structures were grown according to the design. The surface morphology of the film was observed by using atomic force microscopy. The films were characterized by their photoluminescence measurements. X-ray diffraction θ/2θ scan spectroscopy was carried out on the multi-quantum wells. The secondary fringes of the symmetric ω/2θ X-ray diffraction scan peaks indicate that the thicknesses and the alloy compositions of the individual quantum wells are repeatable throughout the active region. The room temperature photoluminescence spectra of the structures indicate that the white light emission of the multi-quantum wells is obtained. The light spectrum covers 400-700 nm, which is almost the whole visible light spectrum.     

加偏置电场的双曲线量子阱中的光整流效应

用量子力学中密度矩阵算符理论导出了加偏置电场的双曲线量子阱中光整流系数的解析表达式.并以典型的GaAs双曲线量子阱为例进行了数值计算。研究结果表明,该势阱中的光整流系数与势阱的形状和偏置电场的强度有关。通过调节势阱参量a以及外加偏置电场,在该势阱中可获得一个大的光整流系数.     

一种特殊的非对称量子阱中的电光效应

运用密度矩阵方法推导出了特殊非对称量子阱中电光系数的解析表达式,并以典型的GaAs/AlGaAs非对称量子阱为例进行了数字计算.计算结果表明,量子阱的非对称性随着参数a的增大而增强,随着参数V₀的增大而减小.电光系数的最大值也随着参数a的增大而增大,随着参数V₀的增大而减小,表明电光系数将随着量子阱非对称性的增大而增大.在取不同的参数a和不同的参数V₀时,电光系数和入射光子能量的关系分别被绘制成曲线图.在图中分别有三个不同的峰,而且系统的非对称性越大,峰值就越大.随着量子阱非对称性的增大,曲线中的峰向能量低的方向移动.另外,在这种量子阱中得到了比较大的电光系数,大约在10^-6m/V量级.随着近来纳米制作技术的进步,使得在实验上制作这种特殊非对称量子阱并得到较好的非线性材料成为可能.     

Influence of electron-beam irradiation in SEM on the cathodoluminescence and electron-beam-induced current in InGaN/GaN light-emitting diodes with a buried active region

The influence of irradiation in a scanning electron microscope on the optical properties inherent to light-emitting diodes (LEDs) with multiple InGaN/GaN quantum wells, assembled by means of the flip-chip mounting technique, has been investigated via the cathodoluminescence (CL) and electron-beam-induced current methods. It is demonstrated that the action of an electron beam qualitatively varies both these LEDs and structures with a thin upper GaN layer only at large beam energies. It has been revealed that irradiation not only leads to changes in the spectrum and intensity of CL but also decreases the energy corresponding to the excitation of emission associated with quantum wells. A similar effect is also observed in structures whose external quantum efficiency has been decreased several times due to long-running tests performed at an injection current density of 35 A/cm² and a temperature of 100°C.