In0.53Ga0.47As/In0.52Al0.48As量子阱中双子带占据的二维电子气的输运特性

研究了不同沟道厚度的In_0.53Ga_0.47As/In_0.52Al_0.48As量子阱中双子带占据的二维电子气的输运特性.在考虑了两个子带电子之间的磁致子带间散射效应后,通过分析Shubnikov-de Haas振荡一阶微分的快速傅里叶变换结果,获得了每个子带电子的浓度、输运散射时间、量子散射时间以及子带之间的散射时间.结果表明,对于所研究的样品,第一子带电子受到的小角散射更强,这与第一子带电子受到了更强的电离杂质散射有 关键词： 二维电子气 散射时间 自洽计算     

In0.53Ga0.47AS/In0.52Al0.48As量子阱中的正磁电阻效应

在低温强磁场条件下,对In0.53 Ga0.47 As/In0.52AI0.48As量子阱中的二维电子气进行了磁输运测试.在低磁场范围内观察到正磁电阻效应,在高磁场下这一正磁电阻趋于饱和,分析表明这一现象与二维电子气中的电子占据两个子带有关.在考虑了两个子带之间的散射效应后,通过分析低磁场下的正磁电阻,得到了每个子带电子的迁移率,结果表明第二子带电子的迁移率高于第一子带电子的迁移率.进一步分析表明,这主要是由两个子带之间的散射引起的.     

In0.53Ga0.47As/In0.52Al0.48As量子阱中的正磁电阻效应

在低温强磁场条件下,对In_0.53Ga_0.47As/In_0.52Al_0.48As量子阱中的二维电子气进行了磁输运测试.在低磁场范围内观察到正磁电阻效应,在高磁场下这一正磁电阻趋于饱和,分析表明这一现象与二维电子气中的电子占据两个子带有关.在考虑了两个子带之间的散射效应后,通过分析低磁场下的正磁电阻,得到了每个子带电子的迁移率,结果表明第二子带电子的迁移率高于第一子带电子的迁移率.进一步分析表明,这主要是由两个子带之间的 关键词： 二维电子气 正磁电阻 子带散射     

双δ掺杂In0.65Ga0.35As/In0.52Al0.48As赝型高迁移率晶体管材料子带电子特性研究

研究了基于InP基的In0.65Ga0.35As/In0.52Al0.48As赝型高迁移率晶体管材料中纵向磁电阻的Shubnikov-deHaas(SdH)振荡效应和霍耳效应,通过对纵向磁电阻SdH振荡的快速傅里叶变换分析,获得了各子带电子的浓度,并因此求得了各子带能级相对于费米能级的位置.联立求解Schrdinger方程和Poisson方程,自洽计算了样品的导带形状、载流子浓度分布以及各子带能级和费米能级位置.理论计算和实验结果很好符合.实验和理论计算均表明,势垒层的掺杂电子几乎全部转移到了量子阱中,转移率在95%以上.     

AlxGa1-xN/GaN异质结二维电子气磁输运性质研究

在1.5K低温和0～9T的高磁场下研究了AlGaG/GaN异质结二维电子气的磁输运性质.实验结果在4块样品中都观察到了Shubnikov-da HaSS振荡的双周期行为.表明异质结的三角势阱中有两个子带被电子占据.通过电子子带占据时电子浓度分配的线形行为得到第二子带被占据的阈值浓度为7.2×1012cm-2.通过对不同样品量子散射时间和输运迁移率的研究,说明在1.5K下远程离化施主散射在量子散射时间中起主要作用.     

单边掺杂InAlAs/InGaAs单量子阱中二维电子气的磁输运特性

研究了双子带占据的In_0.52Al_0.48As/In_0.53Ga_{0 .47}As单量子阱中磁电阻的Shubnikov-de Haas(SdH)振荡效应和霍耳效应，获得了不 同子带电子的浓度、迁移率、有效质量和能级位置.低磁感应强度(B＜1.5T)下由迁移率谱和 多载流子拟合相结合的方法得到的各子带电子浓度与通过SdH振荡得到的结果一致.在d ²ρ/dB²-1/B的快速傅里叶变换 关键词： InAlAs/InGaAs单量子阱 SdH振荡 二维电子气 磁致子带间散射     

AlxGa1-xN/GaN调制掺杂异质结构的子带性质研究

通过低温和强磁场下的磁输运测量研究了Al0.22Ga0.78N/GaN调制掺杂异质结构中2DEG的子带占据性质和子带输运性质.在该异质结构的磁阻振荡中观察到了双子带占据现象,并发现2DEG的总浓度随第二子带浓度的变化呈线性关系.得到了该异质结构中第二子带被2DEG占据的阈值电子浓度为7.3×1012cm-2.采用迁移率谱技术得到了不同样品的分别对应于第一和第二子带的输运迁移率.发现当样品产生应变弛豫时第一子带的电子迁移率骤然下降,而且第二子带的电子迁移率远大于第一子带的电子迁移率.用电子波函数分布和应变弛豫时的失配位错散射解释了上述现象.同时进一步说明了界面粗糙散射和合金无序散射是决定AlxGa1-xN/GaN异质结构中2DEG迁移率的主要散射机理.     

不同量子阱宽度的InP基In0.53GaAs/In0.52AlAs高电子迁移率晶体管材料二维电子气的性能研究

用Shubnikov-de Haas(SdH)振荡效应，研究了在1.4 K下不同量子阱宽度(10—35 nm)的InP基高电子迁移率晶体管材料的二维电子气特性.通过对纵向电阻SdH振荡的快速傅里叶变换分析，得到不同阱宽时量子阱中二维电子气各子带电子浓度和量子迁移率.研究发现，在Si掺杂浓度一定时，阱宽的改变对于量子阱中总的载流子浓度改变不大，但是随着阱宽的增加，阱中的电子从占据一个子带到占据两个子带，且第二子带上的载流子迁移率远大于第一子带迁移率.当量子阱宽度为20 nm时，处在第二子能级上的电子数与处在 关键词： 量子阱宽 二维电子气 Shubnikov-de Haas振荡 高电子迁移率晶体管     

InAs/InP柱型量子线中隧穿时间和逃逸问题的研究

在有效质量近似和绝热近似下,利用转移矩阵法研究了电子通过In As/In P/In As/In P/In As柱形量子线共振隧穿二极管的输运问题,分析和讨论了电子居留时间以及电子的逃逸过程.详细研究了外加电场、结构尺寸效应对居留时间和电子逃逸的影响.居留时间随电子纵向能量的演化呈现出共振现象;同时,结构的非对称性对电子居留时间有很大的影响,随着结构非对称性的增加,居留时间表现出不同的变化.利用有限差分方法研究了非对称耦合量子盘中电子的相干隧穿逃逸过程.     

量子点器件的三端电测量研究

利用三端电测量方法，研究了调制掺杂二维电子气结构的量子点器件输运特性.报道了可分别测量二维电子气电阻和量子点隧穿电阻的实验方法.实验结果表明：量子点的横向耦合控制了量子点器件在小偏压下的电输运特性. 关键词： 自组装量子点 二维电子气 量子隧穿 肖特基接触     

Study of single event effect for the InP-based HEMT with In0.53Ga0.47As/In0.3Ga0.7As/In0.7Ga0.3As composite channel

In this study, the single event effects in In_0.53Ga_0.47As/In_0.3Ga_0.7As/In_0.7Ga_0.3As composite channel InP-based HEMT are investigated using TCAD simulation for the first time. Due to the higher conduction band difference between bottom In_0.7Ga_0.3As channel and InAlAs buffer, the electrons in the buffer layer induced by ions strike cannot enter the channel, led to reduce the peak concentration in the composite channel and significantly weakened the drain current for composite channel device. Meanwhile, higher barrier height under the gate for composite channel InP-based HEMT is formed after particle strike, and further attenuate the drain current. Therefore, the single event effects can be effectively reduced by designing channel structure. In addition, drain voltage and incident position also show significant impact drain current. With the increase in the drain voltage, the drain current increase and the most sensitive incident position is the gate electrode for the device.     

Annealing of ion-implanted Ga0.47In0.53As

We have investigated annealing of ion-implanted GaInAs using transmission electron microscopy. We have found that the best condition for the post-implantation anneals for GalnAs is a 30 second anneal at a temperature of 700–800°C. This produces a material similar in character to the untreated GaInAs. Anneals for longer than 30 seconds produce crystal defects becoming increasingly complex with time for similar temperatures.     

应力导致InAs/In0.15Ga0.85As量子点结构中 In0.15Ga0.85As阱层的合金分解效应研究

利用固源分子束外延技术,在In0.15Ga0.85As/GaAs量子阱生长了两个InAs/In0.15Ga0.85As量子点(DWELL)样品.通过改变其中一个InAs DWELL样品中的In0.15Ga0.85As阱层的厚度和生长温度,获得了量子点尺寸增大而且尺寸分布更均匀的结果.结合光致发光光谱(PL)和压电调制光谱(PzR)实验结果,发现该样品量子点的光学性质也同时得到了极大的优化.基于有效质量近似的数值计算结果表明:量子点后生长过程中应力导致In0.15Ga0.85As阱层合金分解机理是导致量子点尺寸和光学性质得到优化的主要原因.     

两个子带占据的In0.53Ga0.47As/In0.52Al0.48As量子阱中填充因子的变化规律

研究了低温(1.5K)和强磁场(0-13T)条件下,InP基In0.53Ga0.47As/In0.52Al0.48As量子阱中电子占据两个子带时填充因子随磁场的变化规律.结果表明,在电子自旋分裂能远小于朗道能级展宽的情况下,如果两个子带分裂能是朗道分裂能的整数倍时,即⊿E21=κ*ωc(其中κ为整数),填充因子为偶数;当两个子带分裂能为朗道分裂能的半奇数倍时,即⊿E21=(2κ 1*ω/2,填充因子出现奇数.     

Momentum conservation in the luminescence of modulation-doped Ga x In1−x As−Al y In1−y As quantum wells

Summary Thek-conserving selection rule in the electron-hole recombination is investigated by intensity-dependent photoluminescence measurements inn-type modulation-doped Ga _x In_1−x As−Al _y In_1−y As single quantum wells intentionally doped with Be acceptors in the well centre. Thek-non-conserving recombination process involves electrons with momentum up to the Fermi edge and holes localized on the Be acceptors. The transition from a one-component electron plasma to a two-component electron-hole plasma is studied by comparing the experimental results with theoretical line shape models. The density-dependent band gap renormalization is determined for the one-component and the two-component electron-hole plasma. The obtained results are found to agree well with recent theoretical calculations.     

The electronic structure of modulation-doped In0.53Ga0.47As/n-In0.52Al0.48As heterostructure

Summary The subband structure of modulation-doped InGaAs/InAlAs heterostructures is calculated in a variational self-consistent manner. The dependence on various device parameters is examined. The many-body exchange correlation effects are taken into account.     

Weak localization in Al0.25Ga0.75As/In0.2Ga0.8As/GaAs wires

The phase coherence length L_Ø, its temperature dependence and the spin-orbit scattering length L_SO in Al_0.25Ga_0.75As/In_0.2Ga_0.8As/GaAs wires fabricated by electron-beam lithography and CH₄/H₂ Reactive Ion Etching (RIE), were extracted by fitting a 1-dimensional weak localization theory to two-terminal measurements in the temperature range between 2 K and 50 K. The scattering mechanism was found to be Nyquist (electron-electron collisions with small energy transfer).     

Nonparabolic tendency of electron effective mass estimated by confined states in In0.53Ga0.47As/In0.52Al0.48As multi-quantum-well structures

We observed that a series of peaks, which were clearly extracted from a photocurrent difference spectrum, corresponded to interband optical transitions of an In_0.53Ga_0.47As /In_0.52Al_0.48As multi-quantum wells structure. The nonparabolic tendency of the electron effective mass was suggested from eigenenergies of conduction subbands. The effective mass estimated in a direction normal to the InGaAs quantum well plane was heavier than the effective mass of the bulk band edge and was 0.07 m₀at the top of a quantum potential well.     

Design of strain-compensated In x Ga1-x As/In y Al1-y As quantum cascade laser structures towards the shorter wavelengths

We design the In _x Ga_1-x As/In_yAl_1-yAs quantum cascade laser (QCL) structures, based on the four-quantum well active region with vertical transition with strain compensation towards the shorter wavelengths, operating at λ ~2.93–6.6μm. Considering the objective function related to the optical gain, i.e., ${z_{43}^2 (1-\tau_3 /\tau_{43})\tau_4}$ , and the escape energy related to the carrier leakage to continuum, the design of QCLs is carried out in double infinite feedback loops. Each barrier/well layer in the active region is optimized towards the lasing wavelength as short as possible under a properly designed injector. For efficient short wavelength emission, the larger conduction band discontinuity (ΔE _c ) is achieved by changing the indium mole fractions of strain-compensated In _x Ga_1-x As/In_yAl_1-y As layers. The experimentally verified injectors are properly modified for the stronger coupling between the wavefunctions of the ground state in injector and the upper state in active region. Thus the use of strain-compensated In_0.72Ga_0.28As/In_0.3Al_0.7As structure (i.e., ΔE _c = 857 meV) leads to the shortest wavelength up to λ ~2.93μm with τ ₄₃ = 2.13 ps, τ ₄ = 0.87 ps, τ ₃ = 1.43 ps and z ₄₃ = 1.03 nm under an electric field of 96 kV/cm.