How to Avoid Plastic Deformation in GaAs Wafers during Molecular Beam Epitaxial Growth

Plastic deformation in two‐inch diameter GaAs wafers resulted from standard thermal treatments which accompanied epitaxial growth in molecular beam epitaxy (MBE) machines of three different makes. Synchrotron based X‐ray transmission topography was used to distinguish between thermal treatment induced dislocation bundles and misfit dislocations. Eradication of the wafer slip related dislocation bundles has been achieved by modifications to the sample holder of a user built MBE machine. These modifications are discussed, the extent of the problem is briefly outlined, and an extrapolation of the susceptibility of GaAs wafers of higher diameters to this type of plastic deformation is given.     

On the Analysis of Hydrogen in as grown and Ion Implanted GaAs Single Crystals

Hydrogen detection and analysis was carried out on the undoped semi‐insulating (S.I.) gallium arsenide (GaAs) single crystal using conventional elastic recoil detection analysis (ERDA) technique with high energy, heavy ion beam. Presence of hydrogen (nearly 3 x 1020 atoms/cc) has been observed on the as‐grown samples and further high concentration of atomic hydrogen (total concentration of 7 x 1020 atoms/cc) was found at the surface and was found to be decreasing with depth after 100 nm. Further the low energy hydrogen and oxygen ions implanted separately in GaAs at room temperature were also analysed by ERDA technique. From the analysis, the projected range (Rp) of 100 keV hydrogen and oxygen ions in GaAs was determined to be 891 nm (with Δ Rp equal to 320 nm), 170 nm (with Δ Rp equal to 120 nm) respectively. The experimentally determined values of both Rp and Δ Rp are more as compared with the values obtained using the TRIM theoretical program. Low temperature (4K) photoluminescence (PL) measurements of un‐implanted and H⁺ implanted samples show the passivation of intrinsic deep level defect EL2 and shallow acceptor impurity carbon by the low energy implanted hydrogen ions. The low energy hydrogen implantation may be used as a method of hydrogenation for passivation.     

基于碳纳米薄膜/砷化镓范德华异质结的高性能自驱动光电探测器研究

基于碳纳米材料/体半导体范德华(vdW)异质结的光电器件可以同时实现碳纳米材料的超高载流子迁移率以及体半导体的优异光电性能,且具有结构简单、工艺简便、易于调控界面等优点.尤其是通过调控单壁碳纳米管(SWCNT)的直径/手性、费米能级等可以与体半导体形成能带匹配、具有原子级界面的新型混合维度vdW异质结.本文报道了一种基...     

DX-center energy calculation with quantitative mobility spectrum analysis in n-AlGaAs/GaAs structures with low Al content

Experimental Hall data that were carried out as a function of temperature (60–350 K) and magnetic field (0–1.4 T) were presented for Si-doped low Al content (x=0.14) n–Al_xGa_1−xAs/GaAs heterostructures that were grown by molecular beam epitaxy (MBE). A 2-dimensional electron gas (2DEG) conduction channel and a bulk conduction channel were founded after implementing quantitative mobility spectrum analysis (QMSA) on the magnetic field dependent Hall data. An important decrease in 2DEG carrier density was observed with increasing temperature. The relationship between the bulk carriers and 2DEG carriers was investigated with 1D self consistent Schrödinger–Poisson simulations. The decrement in the 2DEG carrier density was related to the DX-center carrier trapping. With the simulation data that are not included in the effects of DX-centers, 17 meV of effective barrier height between AlGaAs/GaAs layers was found for high temperatures (T>300 K). With the QMSA extracted values that are influenced by DX-centers, 166 meV of the DX-center activation energy value were founded at the same temperatures.     

Impurity photovoltaic effect in <Emphasis Type="Italic">p-i-n</Emphasis> structures of undoped GaAs

Photo-emf in the range hv = 0.76 ? 1.35 eV was found in p-i-n structures produced from undoped GaAs crystals with known parameters; the current sensitivities in the impurity and intrinsic (hv > 1.35 eV) regions were comparable. It was proven that the impurity photovoltaic effect results from EL2 and EL3 structural defects creating deep donor levels in the forbidden zone. Calculations were performed that justified the possibility of observing this effect on the investigated structures.     

激活台内透射式GaAs光电阴极的光谱响应特性研究

利用在线光谱响应技术,对透射式GaAs光电阴极在高温激活和低温激活后的光谱响应特性进行了测试,计算并比较了高温激活和低温激活后阴极的积分灵敏度和光谱响应特性参数.结果发现,与高温激活相比,低温激活后GaAs光电阴极的积分灵敏度提高了13％,低温激活后阴极的截止波长和峰值波长均向长波有微小偏移.将已获得的测试曲线与铟封后的三代像增强器的光谱响应曲线进行了比较,结果发现铟封前后的光谱响应曲线存在明显差异.     

Spin–orbit coupling effects on the in-plane optical anisotropy of semiconductor quantum wells

We theoretically study the influence of the spin–orbit coupling(SOC) on the in-plane optical anisotropy(IPOA) induced by in-plane uniaxial strain and interface asymmetry in(001) GaAs/AlGaAs quantum wells(QWs) with different well width. It is found that the SOC has more significant impact on the IPOA for the transition of the first valence subband of heavy hole to the first conduction band(1H1E) than that of 1L1E. The reason has been discussed. The IPOA of(001) InGaAs/InP QWs has been measured by reflectance difference spectroscopy, whose amplitude is about one order larger than that of GaAs/AlGaAs QWs. The anisotropic interface potential parameters of InGaAs/InP QWs are also determined. The influence of the SOC effect on the IPOA of InGaAs/InP QWs when the QWs are under tensile, compressive or zero biaxial strain are also investigated in theory. Our results demonstrate that the SOC has significant effect on the IPOA especially for semiconductor QWs with small well width, and therefore cannot be ignored.     

二维缺陷GaAs电子结构和光学性质第一性原理研究

采用基于密度泛函理论的第一性原理方法计算了存在Ga空位缺陷和掺杂B原子的二维GaAs的能带结构、态密度和光学性质.计算结果表明空位缺陷二维GaAs显示出金属特性,B原子的引入使体系变为间接带隙半导体,禁带宽度为0.35 eV.态密度计算发现体系低能带主要由Ga的s态、p态、d态和As的s态、p态构成;高能带主要由Ga和As的s态、p态构成.掺杂B原子与存在空位缺陷的二维GaAs相比,静态介电常数相对较低,变为8.42,且易于吸收紫外光,在3.90～8.63 eV能量范围具有金属反射特性,反射率达到52%.     

砷化镓光电阴极光谱响应与吸收率关系分析

为了研究砷化镓(GaAs)光电阴极光谱响应与吸收率曲线间的关系,采用分子束外延法(MBE)和金属有机化合物化学气相沉积法(MOCVD)制备了两类GaAs光电阴极,并测试得到了样品吸收率和光谱响应实验曲线.对每个样品的这两条曲线在同一坐标系中做最大值归一化处理,将归一的光谱响应曲线与归一的吸收率曲线做除法,得到了类似光电阴极表面势垒的形状.结果表明,两种方法制备的光电阴极光谱响应曲线相比吸收率曲线都发生了红移,MBE样品偏移量稍大于MOCVD样品.短波吸收率不截止,光谱响应截止于500 nm左右;可见光波段上,光谱响应曲线的峰值位置相比吸收率曲线红移了几百meV;近红外区域,光谱响应曲线的截止位置相比吸收率曲线红移了几个meV.MOCVD样品中杂质对带隙的影响更小,光谱响应相比吸收率发生的能量偏移更小.这些结论对提高GaAs光电阴极光电发射性能有指导意义.     

薄膜砷化镓太阳能电池晶圆片金-金键合热应力影响因素分析

针对砷化镓太阳能电池键合过程中键合界面位错密度过大、部分区域解键合等问题,通过金-金热压键合技术结合有限元方法,提出了一系列降低结构热应力的有效途径.以砷化镓薄膜电池GaAs/Au/PI晶圆片为研究对象,建立三维电池模型,观察和分析了在热和压力同时作用下键合界面的热应力分布及结构变形情况,并探究了金层厚度与热压曲线对结构热应力的影响.分析结果表明,所提出的改进方法使结构热应力大大减少,提高了电池的键合率.