赝形InGaAs/InAlAs渐变异质结中的零磁场自旋分裂

在赝形渐变InGaAs/In_0.52Al_0.48As异质结的二维电子气中,发现了自旋方向向上的电子和自旋向下的电子在零磁场下存在着自旋分裂.利用Shubnikov-de Haas振荡研究了异质结中的自旋分裂行为,通过振荡中的拍频现象,发现了零磁场下的自旋分裂量为8.76meV. 关键词：     

赝配InGaAs/InAlAs调制掺杂异质结构的Shubnikov-de Haas振荡

赝配InGaAs/InAlAs调制掺杂异质结构可以获得很高的电子气面密度和电子迁移率，从而可以制成具有优越高频和低噪声特性的高电子迁移率晶体管(HEMT).文中报道InGaAs/InAlAs调制掺杂异质结构低温下纵向和横向磁阻随磁场强度变化的Shubnikov-de Haas(SdH)振荡和量子Hall效应.对SdH振荡曲线作了快速傅里叶变换，获得了二维电子气的能带结构和各能带上的电子气面密度.分析比较了顶层InGaAs不同掺杂情况对SdH振荡的影响，结果发现顶层InGaAs重掺杂，会对表面态起屏蔽作用， 关键词：     

InGaAs/GaAs应变异质结中的反常离子沟道效应

用5.8,3.0和1.2MeV的Li离子对用MBE制备的In_0.25Ga_0.75As/GaAs(100)异质结在(100)面中沿[100]及[110]轴进行角扫描。5.8MeV时,[110]轴外延层与衬底沟道对准角的差值为0.90°,从而计算出其晶格失配度为1.62％。3.0MeV时,背散射角扫描谱出现了严重的不对称现象。若离子以1.2MeV入射,沟道对准角的差值及衬底沟道的半角宽大大地偏离实际值。本文对以上反常现象从物理机理上进行了分析,给出了这些反常离子沟道 关键词：     

InAlAs/InGaAs/InAlAs量子阱高迁移率二维电子气系统中的反弱局域效应研究

研究了Si 重δ 掺杂In_0.52Al_0.48As/In_0.53Ga_0.47As/In_0.52Al_0.48As单量子阱内高迁移率二维电子气系统中的反弱局域效应. 研究表明，强的Rashba自旋轨道相互作用来源于量子阱高的结构反演不对称. 高迁移率系统中，粒子的运动基于弹道输运而非扩散输运. 因此，旧的理论模型不能用于拟合实验结果. 由于最新的模型在实际拟合中过于复杂，一种简单可行的近似用于处理实验结果，并获得了自旋分裂能Δ₀和自旋轨道耦合常数α两个重要的物理参数. 该结果与对纵向电阻的Shubnikov-de Haas—SdH振荡分析获得的结果一致. 高迁移率系统中的反弱局域效应研究表明，发展有效的反弱局域理论模型，对于利用Rashba自旋轨道相互作用来设计自旋器件尤为重要.     

Self-consistent analysis of double-δ-doped InAlAs/InGaAs/InP HEMTs

We have carried out a theoretical study of double-5-doped InAlAs/InGaAs/InP high electron mobility transistor （HEMT） by means of the finite differential method. The electronic states in the quantum well of the HEMT are calculated self-consistently. Instead of boundary conditions, initial conditions are used to solve the Poisson equation. The concentration of two-dimensional electron gas （2DEG） and its distribution in the HEMT have been obtained. By changing the doping density of upper and lower impurity layers we find that the 2DEG concentration confined in the channel is greatly affected by these two doping layers. But the electrons depleted by the Schottky contact are hardly affected by the lower impurity layer. It is only related to the doping density of upper impurity layer. This means that we can deal with the doping concentrations of the two impurity layers and optimize them separately. Considering the sheet concentration and the mobility of the electrons in the channel, the optimized doping densities are found to be 5 × 10^12 and 3× 10^12 cm^-2 for the upper and lower impurity layers, respectively, in the double-5-doped InAlAs/InGaAs/InP HEMTs.     

自旋—自旋相互作用对红宝石基态零场分裂的贡献

在弱场(LГ表象)中,考虑了d³组态内自旋-自旋相互作用对红宝石基态零场分裂的影响。结果表明它对零场分裂的贡献为0.12厘米^-1。     

异质结界面电荷对突变InP/InGaAs异质结双极晶体管热场发射影响研究

异质结界面电荷的存在改变了异质结的内建势, 这引起了界面势垒尖峰高度和形状的扰动, 从而使异质结界面载流子的输运产生相应的变化, 最终导致异质结双极晶体管 (HBT) 性能的改变. 基于热场发射-扩散模型, 对异质结界面电荷对InP/InGaAs HBT性能的改变做了研究, 得到结论是正极性的界面电荷有利于InP/InGaAs HBT的直流和高频特性的改善, 而负极性的界面电荷则使器件的直流和高频特性变差. 关键词： InP/InGaAs异质结双极晶体管 界面电荷 内建势 热场发射     

δ掺杂的赝形高电子迁移率晶体管AIGaAs/InGaAs/GaAs结构中的费密边奇异性研究

报道了δ掺杂赝形高电子迁移率晶体管结构Al_(0.30)Ga_(0.70)As/In_(0.15)Ga_(0.85)As/GaAs的光致发光光谱研究的实验结果,除了观察到n=1电子子带到n=1重空穴子带,n=2电子子带到n=1重空穴子带间的强发光峰,还观察到了n=1电子子带到n=1轻空穴子带的弱发光峰,通过变化掺杂浓度来改变费密能级的位置,在这种δ掺杂的HEMTs系统中观察到了费密边奇异性,并把它归结为费密海与费密边附近未占据的第二电子子带之间的近共振散射作用所致。     

钙钛矿氧化物异质结自旋极化输运机制研究

文章介绍了一个基于弱Hund耦合规则以及载流子漂移扩散机制所提出的关于钙钛矿氧化物p-n异质结构的自旋极化输运机制的物理模型．该理论不仅可以很好地解释由具有负磁阻效应的La0.9Sr0．1MnO3（LSMO）与非磁性的SrNb0.01Ti0.99O3（SNTO）所组成的异质结中所存在的正磁电阻效应，同时揭示了该体系中LSMO在界面区域的载流子与远离界面区域的载流子具有不同的自旋极化方向．这一结果将为理解钙钛矿氧化物异质结及多层膜的自旋极化输运机制开辟了一条新的途径．     

NUMERICAL STUDY ON TUNNELING SPLITTING IN BIAIXAL SPIN SYSTEMS

Numerical study on tunneling splitting in biaxial spin systems is done by performing diagonalization of the Hamilton operator. It is found that the calculated energy splitting agrees quantitatively with theoretical prediction of instanton method. Our result shows that both the instanton method and the large spin limit work well for the total spin around 10. By including the fourth-order term in Hamiltonian, experimental observation can be re-covered quantitatively.     

A 10.7 μm InGaAs/InAlAs Quantum Cascade Detector

A 10.7μm quantum cascade detector based on lattice matched InGaAs/InAlAs/InP is demonstrated and characterized in terms of responsivity, resistivity and detectivity. The device operates in the 8 14μm atmospheric window up to 140 K and shows a peak reponsivity of 14.4mA/W at 78K. With a resistance-area product value of 159Ωcm^2, the Johnson noise limited detectivity D^＊J is 2.8 × 10^9 Jones （cmHz^1/2W^-1） at 78K.     

High-Power Microwave Photodiodes Based on MBE-Grown InAlAs/InGaAs Heterostructures

Technical Physics - The design and fabrication technology of high-power Schottky-barrier microwave mesa photodiodes from 10 to 40 μm in diameter back-illuminated through the substrate are...     

Structural and Photoluminescence Properties for Highly Strain-Compensated InGaAs/InAlAs Superlattice

The effects of strain compensation are investigated by using twenty periods of highly strain-compensated InGaAs/InAlAs superlattice. The lattice mismatches of individual layers are as high as about 1%, and the thicknesses are close to critical thicknesses. X-ray diffraction measurements show that lattice imperfectness is not serious but still present, though the structural parameters are within the range of theoretical design criteria for structural stability. Rough interfaces and composition fluctuations are the primary causes for lattice imperfectness. Photoluminescence measurements show the large thermally activated nonradiative recombination in the sample. In addition, the recombination process gradually evolves from excitonic recombination at lower temperatures to band-to-band recombination at higher temperatures, which should be considered in device applications.     

High-gain and oscillatory transconductance by InGaAs/InAlAs multiple-quantum-well emitter bipolar transistor

We report an InGaAs/InAlAs multiple-quantum-well (MQW) emitter bipolar transistor prepared by molecular beam epitaxy. There are three distinct operating regimes to be observed in the studied structure. At small input base currents, low field band-type conduction provides the output current. The device exhibits a small gain and works as a normal transistor. With further increase in the base current, the high field starts appearing in the MQW superlattice. We observe that both the output current and transconductance exhibit an oscillatory behaviour in terms of sequential resonant-tunnelling through an expanding high field MQW domain. Beyond the condition of expansion of high field domain, the electron current increases rapidly by tunnelling through the triangular barrier and emitting over the base layer. The MQW superlattice now works as a barrier to hole minority carriers within this region. We obtain a common-emitter current gain as high as 240 with a small offset voltage of about 80 mV.     

Classical Effects in the Weak-Field Magnetoresistance of InGaAs/InAlAs Quantum Wells

We observe an unusual behavior of the low-temperature magnetoresistance of the high-mobility two-dimensional electron gas in InGaAs/InAlAs quantum wells in weak perpendicular magnetic fields. The observed magnetoresistance is qualitatively similar to that expected for the weak localization and antilocalization but its quantity exceeds significantly the scale of the quantum corrections. The calculations show that the obtained data can be explained by the classical effects in electron motion along the open orbits in a quasiperiodic potential relief manifested by the presence of ridges on the quantum well surface.     

High-resolution X-ray diffractometry and transmission electron microscopy as applied to the structural study of InAlAs/InGaAs/InAlAs multilayer transistor nanoheterostructures

InAlAs/InGaAs/InAlAs nanoheterostructures with different structures of metamorphic buffer layer and quantum well, which were grown by means of molecular-beam epitaxy on GaAs and InP substrates, are investigated. The laboratory technology of the growth of the given nanoheterostructures with predicted properties is perfected. The potential of an approach based on the comprehensive analysis of experimental data obtained via different techniques, namely, X-ray diffractometry, electron diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, and atomic-force microscopy is studied. The metamorphic buffer layer design is improved on the basis of the results of the performed investigations. A method whereby balanced-mismatched superlattices are introduced directly inside the metamorphic buffer layer is proposed. It is established that the technological parameters of the growth of nanoheterostructures affect their structural perfection and electrophysical properties.