GaAs/InP低温晶片键合的研究

将硫脲溶液用于GaAs/InP基材料低温晶片键合的表面处理工艺,实现了GaAs/InP基材料间简单、无毒性的低温(380 ℃)晶片键合.并通过界面形貌,解理后断裂面,键合强度及键合界面I-V特性对键合晶片进行了分析.     

键合方法制备长波长面发射的实验和分析

通过疏水键合方法实现了InGaAsP/InP有源区与GaAs/AlAs DBR的单面和双面键合,并通过SEM,I-V曲线和反射谱、光致发光谱等手段研究了GaAs/InP键合界面的机械、光学和电学性质,良好的界面性质为使用键合技术制备长波长面发射激光器提供了可能性.     

键合方法制备长波长面发射的实验和分析

通过疏水键合方法实现了InGaAsP/InP有源区与GaAs/AlAs DBR的单面和双面键合,并通过SEM,I-V曲线和反射谱、光致发光谱等手段研究了GaAs/InP键合界面的机械、光学和电学性质,良好的界面性质为使用键合技术制备长波长面发射激光器提供了可能性.     

基于硫化物表面处理的InP/GaAs低温晶片键合

提出一种新的基于硫化物表面处理的InP/GaAs低温晶片键合技术.在360℃的退火温度下,获得了1.2MPa的键合强度.基于这种低温键合技术,可将外延生长在InP衬底上的In0.53Ga0.47As/InP多量子阱(MQW)键合并转移到GaAs衬底上.X射线衍射表明量子阱的结构未受键合过程的影响.光致发光谱分析表明键合后量子阱的晶体质量略有改善.电流电压特性的测试表明n-InP/n-InP的键合界面具有良好的导电特性;在n-InP/n-GaAs 的键合界面存在着电荷势垒,这主要是由于键合界面存在GaAs氧化物薄层所致.     

基于硫化物表面处理的InP/GaAs低温晶片键合

提出一种新的基于硫化物表面处理的InP/GaAs低温晶片键合技术．在360℃的退火温度下，获得了1.2MPa的键合强度．基于这种低温键合技术，可将外延生长在InP衬底上的In0.53Ga0.47As/InP多量子阱（MQW）键合并转移到GaAs衬底上．X射线衍射表明量子阱的结构未受键合过程的影响．光致发光谱分析表明键合后量子阱的晶体质量略有改善．电流电压特性的测试表明n-InP/n-InP的键合界面具有良好的导电特性；在n-InP/n-GaAs的键合界面存在着电荷势垒，这主要是由于键合界面存在GaAs氧化物薄层所致．     

基于硼酸溶液处理的GaAs/InP低温晶片键合技术

提出了一种基于硼酸溶液的GaAs/InP低温晶片键合技术,实现了GaAs/InP基材料间简单、无毒性的高质量、低温(290℃)晶片键合。GaAs/InP键合晶片解理截面的扫描电子显微镜(SEM)图显示,键合界面整齐,没有裂缝和气泡。通过键合过程,InP上的In0.53Ga0.47As/InP多量子阱结构转移到了GaAs基底上。X射线衍射及荧光谱显示,键合后的多量子阱晶体质量未变。二次离子质谱(SIMS)和Raman光谱图显示,GaAs/InP键合晶片的中间层厚度约为17 nm,界面处B元素有较高的浓度,键合晶片的中间层很薄,因此可以得到较好的电学、光学特性。     

GaAs/Si直接键合用GaAs表面化学活化技术

研究了GaAs/Si疏水性直接键合技术中GaAs表面化学活化关键工艺,对比分析了不同体积分数的HF和HCl溶液作为表面活性处理剂时对GaAs表面进行活化处理的结果。发现用HCl和H2O溶液处理GaAs晶片得到的表面均方根粗糙度要优于用HF处理得到的结果,并且将处理过的GaAs晶片与Si片进行直接键合,发现用HCl进行表面活化的GaAs晶片与Si片键合的成功率要高于用HF进行表面活化的GaAs和Si键合。在200,300和400℃条件下,采用HCl和H2O体积比为1∶10的溶液处理的GaAs晶片与Si片都成功键合,并且200℃条件下键合后的界面质量较好。     

InP/GaAs材料和器件的直接键合

采用三步法在GaAs衬底上实现InP材料的键合,通过X-射线光电子谱(XPS)对样品键合界面进行化学价态和深度分布分析.结果表明,键合温度小于450℃时,样品界面主要由三维氢键网络组成;大于450℃时界面处发生互扩散,Ⅴ族元素主要在界面处富集,而Ⅲ族元素具有较深的扩散.因此提出界面层以InGaAs、InGaP为主,这种界面化学态的变化对样品的Ⅰ-Ⅴ特性和键合强度都具有实质意义的影响,同时由于异质结带阶的存在,要获得良好的电学性质和强度,键合温度并不是越高越好,而是存在一个最佳温度.最后,在GaAs衬底上成功地键合了InGaAs/InP光电探测器.     

光路可调的红外透射方法检测键合质量

基于红外透射原理,采用调节光路的冷光源方法搭建了晶片键合界面的质量检测系统。利用该系统可以很好的实现GaAs,InP材料的键合界面检测和刀片分离时的在线监测,同时本文以GaAs基分布布拉格反射镜(DBR)和InP基有源区键合为例,结合红外透视图像和薄膜转移照片分析,对键合表面处理方法进行了优化选择。试验表明该检测系统数据可靠,使用方便,为晶片键合条件及参数优化提供了实用平台。     

直接键合四结GaAs太阳电池研究

晶圆直接键合技术由于能将表面洁净的两个晶圆集成到一起,从而可以用来制备晶格失配 III-V族多结太阳电池。为了制备GaInP/GaAs/InGaAsP/InGaAs四结太阳电池,需采用具有低电阻率的GaAs/InP键合界面,从而实现GaInP/GaAs和InGaAsP/InGaA上下两个子电池的电学导通。我们设计并研究了具有不同掺杂元素和掺杂浓度的三种键合界面,并采用IV曲线对其电学性质进行表征。此外,对影响键合界面质量的关键工艺过程进行了研究,主要包括表面清洗技术和键合参数优化,例如键合温度、键合压力和键合时间等。最终制备出的键合四结GaInP/GaAs/InGaAsP/InGaAs太阳电池在AM0条件下效率最高达33.2%。     

On the interpretation of electrical measurements on the GaAs-MOS system

Detailed evidence is presented which shows that previously published analyses of various investigations regarding the electrical characteristics of the GaAs MOS system lead to incorrect conclusions. Primarily the results were interpreted in terms of models which were developed to fit the Si-SiO₂ interface properties. However, detailed I–V and admittance measurements show that there are basic differences between the two systems, as the one with GaAs exhibits a charge injection phenomenon across the interface barrier, oxide conduction and a complicated (up to now insufficiently understood) interface behaviour. All these effects prevent the determination of interface state densities by conventional methods. The conclusion, that simply because of a high density of interface states neither accumulation nor inversion are possible, is not justified.     

Quantum-chemical study of adsorption of 2-propanol molecule on a GaAs (100) surface

Quantum-chemical cluster calculations employing density functional theory are used to study the adsorption mechanism of 2-propanol molecules on a Ga-rich GaAs (100) surface. It is shown that 2-propanol molecules can be adsorbed either molecularly or dissociatively. Dissociation of 2-propanol molecules at the GaAs(100) surface can proceed with the rupture of an O-H or C-OH bond. The state with the rupture of the C-OH bond has the lowest energy among all possible adsorption states. However, for transition into this state, a very high barrier should be overcome, which is possible only at the semiconductor/liquid interface. The calculated adsorption path agrees well with the available experimental data on the interaction of 2-propanol with the GaAs (100) surface.     

Determination of energetic distribution of interface states betweengate metal and semiconductor in sub-micron devices from current-voltagecharacteristics

Density and energetic distributions of interface states between metal-semiconductor rectifying contacts in sub-micron GaAs MESFET and AlGaAs/InGaAs pseudomorphic high electron mobility transistors (HEMT's) have been studied. Electrical properties of the interface states between gate metal and semiconductor in sub-micron devices depend on growth technique, associated processing parameters and surface states on III-V semiconductors. Correlation between nonideal current-voltage (I-V) characteristics and interface states has been established through the bias dependence of ideality factor. Ideality factor determined from I-V characteristics of MESFET and HEMT increases with bias and then decreases after reaching a maximum. A theoretical model based on nonequilibrium approach has been used to determine the density of interface states and their energetic distribution from ideality factor. Essentially, Fermi level shifts with applied bias and Schottky barrier height changes due to trapping and detrapping of electrons by the interface states, and from these changes, density of interface states and their energetic distributions have been determined     

Interface state density in Au-nGaAs Schottky diodes

A method for determining the surface state density in Schottky diodes taking into account both I–V and C–V data while considering the presence of a deep donor level is presented. The model assumes that the barrier height is controlled by the energy distribution of surface states in equilibrium with the metal and the applied potential and does not include, explicitly, an interfacial layer. The model was applied to extract interface state densities of Au-nGaAs guarded Schottky diodes fabricated from bulk and VPE (100) GaAs with carrier conentrations between 3 × 10¹⁵ and 8 × 10¹⁶ cm^?3. These diodes exhibited ideality (n) factors of approximately 1.02 and room temperature saturation current densities ～10^?8 A/cm². This model is in substantial agreement with forward bias measurements over the 77–360°K temperature range investigated, in that a temperature-independent energy distribution of interface states was obtained. In reverse bias the interface state model is most valid with the higher carrier concentration material and at high temperature and low bias voltage. Typical interface state densities from 0.07 eV above the zero bias Fermi level to 0.01 eV below the Fermi level were 2 × 10¹³ cm^?2 eV^?1. The validity of the model under reverse bias is restricted by a non-thermionic reverse current, thought to be enhance field emission from traps.     

Electrical characteristics of the SiO2Si interface near midgap and in weak inversion

The electrical characteristics of the SiO₂Si interface in depletion are well understood, but very little information is available on the behavior of surface states in the midgap and weak inversion regions. In this work we develop a general numerical model for the surface state branch which is valid in all bias regions. The model is compared to experimental results in detail, and the surface state density and electron capture cross-section are deduced in the lower half of the bandgap (weak inversion) for two thick oxide samples. The electron capture cross-section was found to be relatively independent of energy through midgap and into weak inversion, in contrast to the exponential dependence on energy reported by others in depletion. The ratio of electron capture cross-section to hole capture cross-section is measured at midgap and found to have a systematic dependence on midgap surface state density, independent of substrate orientation or sample annealing. It is possible that this observation arises because of inadequacies in the model.     

Processing and reconstruction effects on Al-GaAs(100) barrier heights

We have used low-energy electron diffraction, soft x-ray photoemission, and cathodoluminescence (CLS) spectroscopies to investigate the effects of the GaAs(100) surface geometry and composition on the formation of electrically active interface states at Al-GaAs(100) contacts. Clean GaAs(100) surfaces in the 350 to 620°C annealing temperature range undergo large compositional, structural, and electronic changes with temperature. Aluminum thin film deposition induces new discrete deep level CLS features between ∼0.80 and 1.20 eV photon energy, whose properties depend sensitively and systematically on surface annealing temperature and/or reconstruction. Fermi level (E_F) stabilization energies at these interfaces span the range from 0.58 eV above the valence band maximum (E_v) for an arsenic-rich starting surface to 0.46 eV above E_v for a gallium-rich starting surface. Correlation between the aluminum-induced deep level energies and the interface E_F position suggests an important role of localized bandgap states in determining the interface barrier height. The sensitivity of these states to starting surface composition and reconstruction may open new possibilities for tailoring Schottky barrier properties.     

Current-voltage characteristics of Schottky barrier diodes withdynamic interfacial defect state occupancy

Schottky barrier diode theory conventionally assumes that the barrier height remains constant with the applied bias. However, high ideality factors and certain anomalous capacitance-voltage characteristics can only be explained by letting the barrier height vary with the applied voltage. Changes in the occupation of surface states have been inferred to be the cause of this change in barrier height, although the precise nature of these surface states has not yet been determined. This article examines the role of monoenergetic interfacial defect states whose occupancy is dynamically controlled by the local carrier densities, rather than by equilibrium conditions. Certain types of surface donor and acceptor states are shown to have a strong influence on the resulting current-voltage characteristics. The Al/GaAs(100) system is discussed in detail and experimental results are compared to this analytic model     

Metal-germanium Schottky barriers

A systematic study has been made of the electrical characteristics of Schottky barriers fabricated by evaporating various metal films on n-type chemically cleaned germanium substrates. The diodes, with the exception of Al---Ge contacts, exhibit near-ideal electrical characteristics and age only slightly towards lower barrier height values. Al---Ge contacts exhibit very pronounced ageing towards higher barrier height values, due to formation of an extra aluminium oxide interfacial layer. Because of this, the barrier height values of aged Al---Ge contacts derived from I-V and C-V characteristics differ significantly. The dependence of the barrier height, (φ_b) on the metal work function, φ_m, for different metal-germanium contacts shows that surface states play an important role in the formation of the barrier. The density of germanium surface states is estimated to be D_s = 2 × 10¹³ eV⁻¹ cm⁻².     

The application of optimization techniques in the study of Schottky-barrier devices

In this paper, we discuss a numerical optimization technique which may be used to study the effect of interface states on the terminal characteristics of Schottky-barrier devices. The numerical technique is based on the minimization of the sum of residuals obtained by comparing accurate experimental data with a generalized theoretical model. The analysis used in the present study is based on Heine's model and takes the interfacial charges into account. The terminal characteristics of Au-Si Schottky-barrier devices are studied and analyzed. Information regarding interface state density, barrier height, etc., is obtained by using the optimization procedure in conjunction with the current-voltage and capacitance-voltage characteristics of these devices. Consistent values for the device parameters have been obtained through the utilization of the optimization technique.