Electromodulation spectroscopy of In0.53Ga0.47As/In0.53Ga0.23Al0.24As quantum wells

In_0.53Ga_0.47As/In_0.53Ga_0.23Al_0.24As quantum wells (QWs) of various widths have been grown by molecular beam epitaxy on the InP substrate and investigated by electromodulation spectroscopy, i.e. photoreflectance (PR) and contactless electroreflectance (CER). The optical transitions related to the QW barrier and the QW ground and excited states have been clearly observed in PR and CER spectra. The experimental QW transition energies have been compared with theoretical predictions based on an effective mass formalism model. A good agreement between experimental data and theoretical calculations has been observed when the conduction band offset for the In_0.53Ga_0.47As/In_0.53Ga_0.23Al_0.24As interface equals 60%. In addition, it has been concluded that the conduction band offset for the In_0.53Ga_0.23Al_0.24As/InP interface is close to zero. The obtained results show that InGa(Al)As alloys are very promising materials in the band gap engineering for structures grown on InP substrate.     

Hot electron relaxation in In0.53Ga0.47As

We have determined the hot carrier energy loss rate to the lattice by measuring the cooling curve of a photoexcited hot plasma in In_0.53Ga_0.47As. These measurements were made by using a sensitive upconversion technique to measure the infrared (1.2−1.6 μm) luminescence with 10 ps time resolution. We find the carrier energy loss rate to be about an order of magnitude smaller than predicted by a simple model, and surprisingly insensitive to carrier density at high densities.     

Spatial variation of bandgap energy in In0.53Ga0.47As

We report the observation of spatial variation of the bandgap energy of In_0.53Ga_0.47As in high quality epitaxial samples grown lattice matched to InP. Nine samples grown by three different techniques (LPE, VPE and MBE) were investigated and they all showed this apparently random spatial variation. A bandgap variation as large as 15 meV was observed over distances of the order of 1 mm, an effect corresponding to two percent of bandgap energy.     

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     

Submillimeter wave photoconductivity observation of shallow donors in In0.53Ga0.47As

The hydrogen like 1s 2p (m=–1,0,+1) transitions of two donors have been observed in high intensity magnetic fields up to 8.5T. The m=–1 transitions ocurred between 2 cm^–1 and 25 cm^–1. The signature curves for donors in ternary semiconductor In_0.53Ga_0.47As have now been established.Work supported by the U.s. Air Force Office of Scientific Research under Contract # AFOSR-78-3708-DSupported by the National Science Foundation     

Numerical analysis of In0.53Ga0.47As/InP single photon avalanche diodes

A rigorous theoretical model for In 0.53 Ga 0.47 As/InP single photon avalanche diode is utilized to investigate the dependences of single photon quantum efficiency and dark count probability on structure and operation condition.In the model,low field impact ionizations in charge and absorption layers are allowed,while avalanche breakdown can occur only in the multiplication layer.The origin of dark counts is discussed and the results indicate that the dominant mechanism that gives rise to dark counts depends on both device structure and operating condition.When the multiplication layer is thicker than a critical thickness or the temperature is higher than a critical value,generation-recombination in the absorption layer is the dominative mechanism;otherwise band-to-band tunneling in the multiplication layer dominates the dark counts.The thicknesses of charge and multiplication layers greatly affect the dark count and the peak single photon quantum efficiency and increasing the multiplication layer width may reduce the dark count probability and increase the peak single photon quantum efficiency.However,when the multiplication layer width exceeds 1 μm,the peak single photon quantum efficiency increases slowly and it is finally saturated at the quantum efficiency of the single photon avalanche diodes.     

Electron g-factor in a gated InAs-inserted-channel In0.53Ga0.47As/In0.52Al0.48As heterostructure

We report on electron g-factor in an InAs-inserted In_0.53Ga_0.47As/In_0.52Al_0.48As heterostructure. The gate voltage dependence of g-factor is obtained from the coincidence method. The obtained g-factor values are surprisingly smaller than the g-factor value of bulk InAs, and it is close to the bare g-factor value of In_0.53Ga_0.47As. The large change in g-factor is observed by applying the gate voltage. The obtained gate voltage dependence is not simply explained by the energy dependence of g-factor.     

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     

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In_053Ga_047As/In_052Al_0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ΔE₂₁=kω_c(其中k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ΔE₂₁=(2k+1)ω_c/2,填充因子出现奇数. 关键词： 053Ga_047As/In_052Al_048As量子阱')" href="#">In_053Ga_047As/In_052Al_048As量子阱 填充因子 磁输运     

Current-voltage characteristics and terahertz emission peculiarities of an In0.53Ga0.47As/In0.52Al0.48As HEMT with 2D electron gas

The characteristics of an In_0.53Ga_0.47As/In_0.52Al_0.48As HEMT with 2D electrons in the channel have been studied. The output characteristics of the transistor exhibit negative differential resistance. The emission spectrum of the system contains two narrow resonance lines at frequencies of 0.87 and 1.36 THz. Original Russian Text ? M.L. Orlov, 2009, published in Izvestiya Rossiiskoi Akademii Nauk. Seriya Fizicheskaya, 2009, Vol. 73, No. 1, pp. 115–118.     

In0.53Ga0.47As/InP量子阱与体材料的1 MeV电子束辐照光致发光谱研究

为获得对In_0.53Ga_0.47As/InP材料在电子束辐照下的光致发光谱变化规律, 开展了1 MeV电子束辐照试验, 注量为 5×10¹²-9×10¹⁴ cm^-2. 样品选取量子阱材料和体材料, 在辐照前后, 进行了光致发光谱测试, 得到了不同结构In_0.53Ga_0.47As/InP材料在1 MeV电子束辐照下的不同变化规律; 对比分析了参数退化的物理机理. 结果显示: 试验样品的光致发光峰强度随着辐照剂量增大而显著退化. 体材料最先出现快速退化, 而五层量子阱在注量达到6×10¹⁴ cm^-2时, 就已经退化至辐照前的9%. 经分析认为原因有: 1)电子束进入样品后, 与材料晶格发生能量传递, 破坏晶格完整性, 致使产生的激子数量减少, 光致发光强度降低; 电子束辐照在材料中引入缺陷, 增加了非辐射复合中心密度, 导致载流子迁移率降低. 2)量子阱的二维限制作用使载流子运动受限, 从而能够降低载流子与非辐射复合中心的复合概率; 敏感区域截面积相同条件下, 体材料比量子阱材料辐射损伤更为严重. 3)量子阱的层数越多, 则异质结界面数越多, 相应的产生的界面缺陷数量也随之增多, 辐射损伤越严重.     

Modulated cyclotron resonance in multi-quantum well structure of In0.53Ga0.47As/InP induced by interband and exciton excitation

We report for the first time the modulated cyclotron resonance of electrons in the lattice-matched multi-quantum well structures of In_0.53Ga_0.47As/InP induced by monochromatic light beam of excitation. The resonant enhancement and modulation of the cyclotron resonance of electron due to interband and exciton excitation in the structures have been observed experimentally, which shows the possible prospect of the method for the observation of cyclotron resonances in semiconductors.October 26, 1993     

High Performance (fT~500GHZ) In0.52Al0.48As/In0.53Ga0.47As/InP Quantum Wire MODFETs Employing Asymmetric Coupled-Well Channels

A coupled-well InAlAs/InGaAs quantum wire MODFET structure is proposed, for which simulations predict improved frequency performance (>500 GHz), over a wider range of V_g, as compared to well/wire devices with a standard MODFET heterointerface. A comparison of several transverse potential well profiles, obtained by varying the placement of a thin barrier within a 100 Å finite well, is presented. In all cases, the quantum wires consist of a 0.1 m long channel and a 150 Å finite-square-well lateral profile. It has been found that the peak of the electron distribution for the first confined state, as measured from the heterointerface, changes dramatically depending on the location of the thin barrier. For quantum wire structures, realized in the lattice matched system of In_0.52Al_0.48As/In_0.53Ga_0.47As/InP, a change in the barrier location of 25 Å is accompanied by a shift in the carrier peak of more than 40 Å (~20 Å closer to or farther from the spacer-well interface than in the standard MODFET profile). Implications of this are reflected in the current-voltage characteristics (I_d-V_d) and frequency responses (f_T-V_g) of the proposed structures.     

Femtosecond laser spectroscopy of In0.53Ga0.47As/InP multiple quantum wells: interfacial roughness and photoexcited carrier relaxation

Interfacial properties and relaxation dynamics of photoexcited carriers in In_0.53Ga_0.47As/InP multiple quantum wells (MQWs) have been investigated by means of cross-sectional scanning tunneling spectroscopy and optical spectroscopy methods (luminescence, absorption and pump–probe experiments). The MQW structure consists of 125 periods of 10-nm-wide well layers and 40-nm-wide barrier layers on an InP(0 0 1) substrate. The observed interfacial roughness of the InGaAs-on-InP is 1–2 monolayers (ML), while that of the InP-on-InGaAs is 3–4 ML. The Stokes shift observed in luminescence and absorption spectra at 77 K corresponds well to the well-width distribution observed by the cross-sectional STM. Differential absorption spectra measured by pump–probe spectroscopy show that relaxation of hot carriers in conduction and valence bands followed by exciton formation takes place in 17–30 ps depending on the excitation photon energy. The excitons formed at the band bottom are localized at thicker areas within a quantum well in 500 ps.     

Growth mode and effect of carrier gas on In0.53Ga0.47As/InP surface morphology grown with trimethylarsine and arsine

Different growth mode have been observed for InGaAs/InP grown with trimethylarsine and arsine by Metalorganic Vapor Phase Epitaxy (MOVPE) when changing the carrier gas. The surface has been investigated by Atomic Force Microscope (AFM) for epilayers grown at 600°C under pure hydrogen or a mixture of hydrogen and nitrogen as carrier gas. The step/terrace surface morphology was observed for InP/InP and InGaAs/InP (001) using 0.2° off substrates. InP epilayers grown under nitrogen flow show step-bunched terraces as large as 170 nm. The effect of the group V source for InGaAs/InP has been studied. It is shown that the step edge characteristic of step flow growth appears for lattice-matched InGaAs/InP grown with arsine. When using TMAs and hydrogen as a carrier gas, the growth mode and surface roughness depends greatly on V/III ratio and growth temperature. Under nitrogen flow with the combination of TMI+TMG+TMAs, pit-like defects (5–8 nm deep) are visible at high surface concentration (10⁹–10¹⁰/cm²). When increasing V/III ratio, 3D growth occurs simultaneously with pit-like defects, recovering the whole surface of the sample. Various surface morphology characteristics of InGaAs epilayers assessed by AFM characterisation will be presented and discussed.     

Optimisation of the ammonium sulphide (NH4)2S passivation process on In0.53Ga0.47As

The passivation of III-V semiconductor materials with sulphur is widely reported to reduce interface state defects and improve semiconductor device performance. The most common approach utilises ammonium sulphide ((NH₄)₂S), however there are wide variations in the reported processing parameters involved in this procedure. This study provides a comprehensive review of the various parameters used as well as determining the optimal processing conditions in terms of sample pre-treatments, temperature of the (NH₄)₂S solution, length of time the sample is in the solution and (NH₄)₂S concentration, by measuring the level of residual native oxides and surface roughness by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM), respectively.     

Influence of spacer layer thickness on the current-voltage characteristics of pseudomorphic AlAs/In0.53Ga0.47As/InAs resonant tunnelling diodes

This paper investigates the dependence of current voltage characteristics of AlAs/In0.53Ga0.47As/InAs resonant tunnelling diodes （RTDs） on spacer layer thickness. It finds that the peak and the valley current density J in the negative differential resistance （NDR） region depends strongly on the thickness of the spacer layer. The measured peak to valley current ratio of RTDs studied here is shown to improve while the current density through RTDs decreases with increasing spacer layer thickness below a critical value.     

Experimental confirmation by galvanomagnetic methods of a complex transport model in In0.53Ga0.47As layers deposited by MBE on SI-InP

At low temperatures In_0.53Ga_0.47As samples show an increase of carrier concentration, which can be explained in terms of a two carriers transport model. This type of problem exists since the beginning of the semiconductor era, dating back to monocrystalline germanium.We propose that in all the investigated layers, there are X atoms or charged dislocations in the region of the first monolayers, which are built in during epitaxial growth. The layers were intentionally undoped. They form an impurity band in which low mobility carriers dominate over the localised electron scattering due to the s-d exchange interaction. These carriers do not freeze out at liquid helium temperature and give rise to two transport media for electrons; a conduction band at higher temperatures and an impurity band at lower temperatures. The electron which fall down onto the previously ionised X atoms, then move by thermally activated hopping. We show that the two carriers model for In_0.53Ga_0.47As epitaxial layers are confirmed by the carrier concentration-temperature, carrier concentration-magnetic field, resistivity-magnetic field behaviour, and also by YKA theory also. The differences between the two transport models are so distinctive that observed phenomena may exist. This paper presents experimental results, which constitute comprehensive evidence for the complicated structure of the semiconductor epitaxial layers on the sample of n-type In_0.53Ga_0.47As/InP layer with n=2.2×10¹⁵/cm³.     

Band offsets in In0.15Ga0.85As/ GaAs and In0.15Ga0.85As/Al0.15Ga0.85As studied by photoluminescence and cathodoluminescence

Photoluminescence and cathodoluminescence measurements of strained undoped In_0.15Ga_0.85As/GaAs and In_0.15Ga_0.85As/Al_0.15Ga_0.85As quantum well structures with emission lines attributed to the first electron–first heavy hole and first electron–first light hole excitonic transitions have been analysed theoretically within the eight-band effective mass approximation. For In_0.15Ga_0.85As/GaAs the results are consistent with either type I or type II alignment of the light hole band. In the case of In_0.15Ga_0.85As/Al_0.15Ga_0.85As our results indicate type II alignment for the light hole band and offset ratio ofQ = 0.83.     

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In_0.15Ga_0.85As/GaAs量子阱生长了两个InAs/In_0.15Ga_0.85As量子点(DWELL)样品.通过改变其中一个InAs DWELL样品中的In_0.15Ga_0.85As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 关键词： 合金分解效应 0.15Ga_0.85As量子点')" href="#">InAs/In_0.15Ga_0.85As量子点 光致发光光谱 压电调制光谱