退火后无应变Ga1-xInxNyAs1-y/GaAs量子阱的带隙

针对快速热退火引起的N最近邻原子环境的变化,建立了热平衡态下Ga1-xInxNyAs1-y合金中各二元化合键的统计分布模型.并将理论计算得到的N周围平均In原子数r引入到BAC经验模型中,对退火后的Ga1-xInxNyAs1-y体材料带隙进行了计算.最后,利用讨论BAC模型中电子波函数边界条件的方法,计算了无应变Ga1-xInxNyAs1-y/GaAs量子阱的带隙.     

InN材料及其应用

由于具有独特的本征特性,InN材料已经成为最近两年国际上最热门的研究材料之一。本文介绍了InN材料的基本性质,探讨了材料的生长技术和应用方向。最后给出了InN材料今后发展急需解决的问题以及未来的发展应用前景。     

(Al_xGa_(1-x)As)_m/(GaAs)_m(001)超晶格的能带结构与合金组分x间的关系

采用紧束缚的重整化方法研究了(Al_xGa_(1-x)As)_m/(GaAs)_m(001)超晶格的电子能带结构与合金组分x及层厚间的变化关系。给出了临界组分x_o与层厚m间的变化关系图。并以二次函数形式给出了直接能隙和间接能隙与合金组分x间的变化关系。最后,也用Kronig—Penney模型对超晶格的电子能带结构进行了计算,并与紧束缚的计算结果进行了比较。     

退火后无应变Ga_(1-x)In_xN_yAs_(1-y)/GaAs量子阱的带隙

针对快速热退火引起的N最近邻原子环境的变化,建立了热平衡态下Ga1-xInxNyAs1-y合金中各二元化合键的统计分布模型.并将理论计算得到的N周围平均In原子数r引入到BAC经验模型中,对退火后的Ga1-xInxNyAs1-y体材料带隙进行了计算.最后,利用讨论BAC模型中电子波函数边界条件的方法,计算了无应变Ga1-xInxNyAs1-y/GaAs量子阱的带隙.     

基于MOCVD生长的高Al组分AlxGa1-xN的HRXRD研究

通过MOCVD设备,在c面蓝宝石衬底上异质外延了不同Al组分含量的Alx,Ga1-xN材料,生长过程中采用了低温缓冲层技术、脉冲原子外延技术(PALE)和多层超晶格缓冲技术,例如AlGaN/AlN SLs结构,成功得到了表面光滑无裂纹的AlxGa1-xN膜.并且通过HRXRD对材料进行了多个晶面方向上的摇摆曲线和20～ω表征测试,在此测试基础上时材料的Al组分、α轴和c轴的晶格常数以及位错密度进行了相应的计算,并定性的分析了材料的应变状态.     

Growth and Characterization of In x Ga1−x As/GaAs1−y P y Strained-Layer Superlattices with High Values of y (~80%)

Strained-layer superlattice (SLS) structures, such as InGaAs/GaAsP lattice matched to GaAs, have shown great potential in absorption devices such as photodetectors and triple-junction photovoltaic cells. However, until recently they have been somewhat hindered by their usage of low-phosphorus GaAsP barriers. High-P-composition GaAsP was developed as the barrier for InGaAs/GaAsP strained-layer superlattice (SLS) structures, and the merits of using such a high composition of phosphorus are discussed. It is believed that these barriers represent the highest phosphorus content to date in such a structure. By using high-composition GaAsP the carriers are collected via tunneling (for barriers ≤30 Å) as opposed to thermionic emission. Thus, by utilizing thin, high-content GaAsP barriers one can increase the percentage of the intrinsic in a p-i-n structure that is composed of InGaAs wells in addition to increasing the number of periods that can be grown for given depletion width. However, standard SLSs of this type inherently possess undesirable compressive strain and quantum size effects (QSEs) that cause the optical absorption of the thin InGaAs SLS wells to shift to higher energies relative to that of bulk InGaAs of the same composition. To circumvent these deleterious QSEs, stress-balanced, pseudomorphic InGaAs/GaAsP staggered SLSs were grown. Staggering was achieved by removing a portion of one well and adding it to an adjacent well. The spectral response obtained from device characterization indicated that staggering resulted in thicker InGaAs films with reduced cutoff energy. Additionally, these data confirm that tunneling is a very effective means for carrier transport in the SLS.     

Structural and spectral features of MOCVD Al x Ga y In1 ? x ? y As z P1 ? z /GaAs (100) alloys

The study is concerned with MOCVD epitaxial heterostructures grown on the basis of Al _x Ga _y In_{1 ? x ? y} As _z P_{1 ? z} quinary alloys in the region of alloy compositions isoperiodic to GaAs. By the X-ray diffraction technique and atomic force microscopy, it is shown that, on the surface of the heterostructures, there are nanometric objects capable of lining up along a certain direction. From calculations of the crystal lattice parameters with consideration for internal strains, it can be inferred that the new compound is a phase based on the Al _x Ga _y In_{1 ? x ? y} As _z P_{1 ? z} alloy.     

退火后无应变Ga1-xInxNyAs-y/GaAs量子阱的带隙

针对快速热退火引起的N最近邻原子环境的变化,建立了热平衡态下Ga1-xInxNyAs-y合金中各二元化合键的统计分布模型.并将理论计算得到的N周围平均In原子数r引入到BAC经验模型中,对退火后的Ga1-xInxNyAs-y体材料带隙进行了计算.最后,利用讨论BAC模型中电子波函数边界条件的方法,计算了无应变Ga1-xInxNyAs-y/GaAs量子阱的带隙.     

不同In组分及阱宽的InGaAs/GaAs应变量子阱的表面光伏谱

本文采用表面光伏谱方法，对不同组分及阱宽的ＩｎＧａＡｓ／ＧａＡｓ应变量子阱进行了变温表面光伏谱测量．利用形变势模型理论计算，对样品的表面光伏谱进行指认，理论与实验符合得很好．     

发射台站ERP、高度和台站间距约束关系研究

首先推导了单频网中两个相邻发射台站最高覆盖效率下,台站间距和覆盖半径的约束关系,然后以中国移动多媒体广播CMMB技术体制作为研究平台,根据国际电联推荐的电压推导法推算出其高速移动时的最小中值场强,最后根据地形地貌等因素确定电波传播模型,继而推算出单频网中两个发射台站在保护间隔内最高覆盖效率下发射台站ERP、高度和台站间距的约束关系.     

Electrical behavior of modulation-and delta-doped Al x Ga1 − x As/In y Ga1 − y As/GaAs PHEMT structures

Modulation-and delta-doped Al_xGa_{1 ? x} As/In_yGa_{1 ? y} As/GaAs PHEMT structures are grown by MBE. The effect is examined of changes in the technique and level of doping on the electrical behavior of the structures. Photoluminescence spectroscopy combined with Hall-effect measurements is shown to be an effective strategy for the purpose. The experimental results are interpreted on the basis of calculated conductionband diagrams.     

Molecular beam epitaxy and characterization of Al x Ga1-x As y Sb1-y (0.0 ≤x ≤ 1.0) lattice matched to InAs substrates

We report the molecular beam epitaxial growth of Al _x Ga_1-x As _y Sb_1-y (0.0 ≤ x ≤ 1.0) on undoped, liquid-encapsulated Czochralski, (100) oriented InAs substrates. The degree of lattice mismatch was determined by x-ray diffraction. The lattice matched materials (y ≈ 0.08 + 0.08x) were characterized by low temperature photoluminescence, electro-reflectance, and capacitance-voltage measurements. The experimental bandgap energies agree with earlier experimental results for Al _x Ga_1-x Sb, and also with a self-consistent first principles pseudopotential model. The capacitance-voltage measurements indicate background acceptor concentrations for the unintentionally-doped epitaxial layers of about 2 × 10¹⁵ cm^-3 atx = 1.0 to 5 × 10¹⁶ cm^-3 atx ≈ 0.0.     

Double heterojunction bipolar transistor in Al/sub x/Ga/sub 1-x/As/GaAs/sub 1-y/Sb/sub y/ system

Double heterojunction bipolar transistors based on the Al/sub x/Ga/sub 1-x/As/GaAs/sub 1-y/Sb/sub y/ system are examined. The base layer consists of narrow band gap GaAs/sub 1-y/Sb/sub y/ and the emitter and collector consist of wider band gap Al/sub x/Ga/sub 1-x/As. Preliminary experimental results show that AlGaAs/GaAsSb/GaAs DHBTs exhibit a current gain of five and a maximum collector current density of 5*10/sup 4/ A/cm/sup 2/.<>     

Growth of Ga x In1−x As y P1−y using ethyldimethylindium andt-butylphophine

The growth of GaInAsP lattice matched to GaAs using tertiary-butylphosphine and ethyldimethylindium to replace the more conventional phosphine and trimethylindium is described. The quaternary compound lattice matched to GaAs has received far less attention than related compositions that lattice match InP. Using the new sources, most of the growth problems experienced by previous workers have been avoided. Uniform compositions have been grown reproducibly without evidence of gas-phase, adduct-forming reactions. Bothn- andp-type films have been grown. Heteroepitaxy of high quality GalnAsP layers on Ge has also been achieved, and microstructural results are presented.     

Turn-on voltage investigation of GaAs-based bipolar transistors with Ga/sub 1-x/In/sub x/As/sub 1-y/N/sub y/ base layers

The fundamental lower limit on the turn on voltage of GaAs-based bipolar transistors is first established, then reduced with the use of a novel low energy-gap base material, Ga/sub 1-x/In/sub x/As/sub 1-y/N/sub y/. InGaP/GaInAsN DHBTs (x/spl sim/3y/spl sim/0.01) with high p-type doping levels (/spl sim/3/spl times/10/sup 19/ cm/sup -3/) and dc current gain (/spl beta//sub max//spl sim/68 at 234 /spl Omega///spl square/) are demonstrated. A reduction in the turn-on voltage over a wide range of practical base sheet resistance values (100 to 400 /spl Omega///spl square/) is established relative to both GaAs BJTs and conventional InGaP/GaAs HBTs with optimized base-emitter interfaces-over 25 mV in heavily doped, high dc current gain samples. The potential to engineer turn-on voltages comparable to Si- or InP-based bipolar devices on a GaAs platform is enabled by the use of lattice matched Ga/sub 1-x/In/sub x/As/sub 1-y/N/sub y/ alloys, which can simultaneously reduce the energy-gap and balance the lattice constant of the base layer when x/spl sim/3y.     

Weak-beam stereomicrography of defects in GaAs/In x Ga1−x As interfaces

Weak-beam stereomicrography was used to image dislocation arrays at the two interfaces in GaAs/In _x Ga_1−x As/GaAs sandwich structures. For samples with mismatch equal to 1.8%, separate dislocation arrays were found at each interface. The measured dislocation density at the upper interface was only 10% of the density found at the lower interface. This is attributed to reduced mismatch at the upper interface due to strain in the In_0.25Ga_0.75As layer. Also, the dislocation spacing asymmetry along the [01l] and [01l] directions is exhibited at each interface. In the upper interface, it is attributed to growth on asymmetrically strained In_0.25Ga_0.75As. Stereo-imaging of samples with higher mismatch (f = 2.9%) showed 3-dimensional details of dislocation half-loop nucleation that leads to a semiorthogonal array with increasing In_0.4Ga_0.6As layer thickness.     

(Al x Ga 1- x ) y In 1- y P Films and Its Optical Constants on the Surface

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Effect of different type intermediate layers on band structure and gain of Ga/sub 1-x/In/sub x/N/sub y/As/sub 1-y/-GaAs quantum well lasers

Based on the band-anticrossing model, the effect of the strain-compensated layer and the strain-mediated layer on the band structure, the gain, and the differential gain of GaInNAs-GaAs quantum well lasers have been investigated. Different band-filling mechanisms have been illustrated. Compared to the GaInNAs-GaAs single quantum well with the same wavelength, the introduction of the strain-compensated layer and the strain-mediated layer increases the transparency carrier density. However, these multilayer structures help to suppress the degradation of the differential gain.     

High frequency performance of Si/sub 1-x/Ge/sub x//Si/sub 1-y/Ge/sub y//Si/sub 1-x/Ge/sub x/ HBTs

The results of a theoretical study of the performance of high speed SiGe HBTs is presented. The study includes a group of SiGe HBTs in which the Ge concentration in the base is 20% higher than that in the emitter and collector (i.e. y=x+0.2). It is shown that the composition dependences of f/sub T/ and the F/sub max/ are non-monotonic. As the Ge composition in the emitter and collector layers is increased, f/sub T/ and f/sub max/ first decrease, then remain constant and finally increase to attain their highest values.<>     

GaxIn1?xAsyP1?y/Gax?,In1?x?,Asy?,P1?y?, DH visible LED grown on (100) GaAs by LPE in the range of 670?680 nm

GaxIn1?xAsyP1?y/Gax?,In1?x?,Asy?,P1?y? visible light emission diodes (LED) are reported. The double heterostructures were grown on (100) GaAs substrates by a liquid phase epitaxial (LPE) growth technique from a source melt rich in phosphorus. The wavelength of emitted light was 670?680 nm at room temperature.