用固态杂质源在GaAs衬底上实现的连续波CO_2激光诱导Zn扩散

用含Ｚｎ的固态杂质源，在化合物半导体ＧａＡｓ基片上进行了连续波（ＣＷ）１０．６μｍ激光诱导扩散，做出了Ｐ－Ｎ结。分别利用扫描电子显微镜和二次离子质谱仪对扩散样品进行扩散区形貌分析和杂质分布研究，给出了结深ｘｊ、杂质浓度分布Ｃ（ｘ，ｔ，Ｔ）等性能参数和扩散时间ｔ、温度Ｔ等工艺参数之间的关系，获得了亚微米的扩散结结深及１０２０ｃｍ－３量级的表面掺杂浓度     

SIMS测量激光诱导扩散Zn的浓度分布

通过SIMS对激光诱导扩散杂质浓度分布的研究,提出了一个测量扩散区只在μm量级或10μm量级范围内的杂质浓度分布的方法.首先利用光刻的方法在基片表面标识出扩散窗口,然后进行激光诱导处理.用SIMS对制成的扩散样品定量分析,通过扫描探针显微镜测量刻蚀深度,由此实现了微小扩散区掺杂浓度-深度分布的研究.     

GaAs中Si扩散机制的研究

本文报道采用选择性掺杂的多晶硅热退火掩膜作扩散源进行的ＧａＡｓ中Ｓｉ扩散机制的研究结果．发现共Ｐ扩散时，样品表层的电学性能明显提高．Ｓｉ杂质的内扩散小；共Ａｌ扩散时，Ｓｉ杂质内扩散很深．用ＧａＡｓ中化学配比平衡观点讨论了扩散层中杂质分布与电学性能关系，认为Ｓｉ杂质在ＧａＡｓ中的热扩散主要由Ａｓ空位浓度决定．     

Yb∶YAG表层增益陶瓷板条波前畸变数值模拟

Yb∶YAG表层增益陶瓷板条在烧结过程中存在离子扩散行为,导致扩散区域折射率变化,引起波前畸变。本文结合扩散理论,建立表层增益陶瓷板条离子浓度分布、折射率空间分布模型,利用数值模拟的方法分析了扩散行为对静态波前畸变的影响。与传统晶体板条相比,陶瓷板条的离子扩散行为,对于静态波前畸变有一定影响,畸变在λ/10量级。     

激光作用下多量子阱混迭的热动力学分析

对ＩｎＧａＡｓ／ＩｎＧａＡｓＰ多量子阱材料,根据温度场方程计算了两种激光作用下多量子阱混迭技术（ＰＡＩＤ及ＰＬＤ）的横向空间选择性,得到ＰＡＩＤ在一般情况下的横向空间选择性为１００μｍ量级,而ＰＬＤ的理论极限为１００μｍ。同时分析了混迭多量子阱材料的能带结构与组分扩散长度的关系,从理论上提出了低温量子阱材料与扩散长度之间的关系曲线。     

高温注入离子的扩散和激活行为的研究

本文应用二次离子质谱（ＳＩＭＳ），微分霍尔效应和透射电镜（ＴＥＭ）研究了硅中高温注入砷离子的扩散和激活行为．将１８０ＫｅＶ，１×１０１５ｃｍ－２砷离子在５００℃至１０００℃的温度范围内注入硅．研究结果表明：在５００℃至８５０℃注入时所发生的异常扩散和载流子浓度及迁移率深度分布与剩余缺陷的分布密切相关；而且随着注入温度的增高，砷的增强扩散亦增强，同时所形成的剩余缺陷减少．在注入温度高于８５０℃时，随着注入温度的增高，砷的增强扩散效应减弱．在５００℃至１０００℃的注入温度，与热扩散相比，砷的增强扩散效应显著；     

p－GaAs／n－GaAs MOCVD外延层少子扩散长度的液结光伏谱测量和分析

用液结光伏谱方法首次在ＰＮ４３５０光伏谱仪上对用国产ＭＯＣＶＤ设备生长的九个ｐ－ＧａＡｓ／ｎ－ＧａＡｓ外延样品ｐ型外延层的少于扩散长度Ｌｎ和掺杂浓度ＮＡ的关系作了测量和分析．结果表明，Ｌｎ－ＮＡ关系对反应管的清洁度非常敏感．如果反应管经严格清洗，并仅生长ＧａＡｓ材料，那么Ｌｎ－ＮＡ关系同前人报道的无沾污生长的样品基本一致；否则Ｌｎ值就明显偏小．用本方法测定ＧａＡｓ外延层的Ｌｎ值具有简便、准确的优点，可作为检测ＧａＡｓ外延层质量的重要手段．     

多次扩散后杂质分布的简单表达式

在现代半导体工艺中有多次不同温度的扩散过程。文章分析了经历这些扩散过程后的杂质分布并且给出了一个简单的表达式。文章指出多次扩散后的杂质分布可以用一个有效扩散长度来表征并且给出了有效扩散长度和各次扩散过程的扩散长度的关系。表达式的结果同工艺仿真软件SUPREM 4符合的很好。文章还给出了如何应用表达式的例子。     

时间分辨扩散拟合方法提取生物组织散射特性

大多数生物组织是一种混浊介质，在０．６～１．３μｍ的红光与近红外光波段具有高的前向散射和低吸收的特点。超短脉冲光在组织中传输时，将因漫散射合脉冲展宽。脉冲形状与散射吸收特性有关。本文提出一种基于扩散近似理论的扩散似合方法，用于提取不同位置的散射特性。     

闭管扩散Zn对InP表面性质的影响

利用闭管扩散方法以Zn3P2为扩散源,在不同扩散温度和扩散时间下对非故意掺杂InP(100)晶片进行扩散.用电化学C-V法(ECV)和二次离子质谱法(SIMS)分别测出了空穴浓度和Zn的浓度随深度的分布曲线.结果表明扩散后InP表面空穴和Zn的浓度在扩散结附近突然下降,InP表面空穴浓度主要取决于扩散温度,扩散深度随着扩散时间的增长而变大,InP表面Zn浓度一般比空穴浓度高一个数量级.另外对扩散后的样品进行光致发光(PL)测试,表明在保证表面载流子浓度的同时,适当降低扩散温度和增加扩散时间能减小对InP表面性质的影响.     

非故意掺杂吸收层InP/InGaAs异质结探测器研究

为了获得低噪声铟镓砷（InGaAs）焦平面,需要采用高质量的非故意掺杂InGaAs（u-InGaAs）吸收层进行探测器的制备。采用闭管扩散方式,实现了Zn元素在u-InGaAs吸收层晶格匹配InP/In_0.53Ga_0.47As异质结构材料中的P型掺杂,利用扫描电容显微技术(SCM)对Zn在材料中的扩散过程进行了研究,结果表明,随着扩散温度和时间增加,p-n结结深显著增加,u-InGaAs吸收层材料的扩散界面相比较高吸收层浓度材料（5×1016 cm?3）趋于缓变。根据实验结果计算了530 ℃下Zn在InP中的扩散系数为1.27×10?12 cm2/s。采用微波光电导衰退法(μ-PCD)提取了InGaAs吸收层的少子寿命为5.2 μs。采用激光诱导电流技术(LBIC)研究了室温下u-InGaAs吸收层器件的光响应分布,结果表明:有效光敏面积显著增大,对实验数据的拟合求出了少子扩散长度L_D为63 μm,与理论计算基本一致。采用u-InGaAs吸收层研制的器件在室温(296 K)下暗电流密度为7.9 nA/cm2,变温测试得到激活能E_a为0.66 eV,通过拟合器件的暗电流成分,得到器件的吸收层少子寿命τ_p约为5.11 μs,与微波光电导衰退法测得的少子寿命基本一致。     

Grown junction GaAs solar cell

Using multiple layer liquid phase epitaxial (LPE) growth techniques, p(AlxGa1-xAs:Ge)-p(GaAs:Ge)-n⁺(GaAs:Te) solar cells were fabricated. Germanium was used as the p-type dopant to eliminate impurity diffusion and to maximize minority carrier diffusion lengths. These procedures provide precise control of the thickness and carrier concentration of each individual layer.     

Measurement of minority carrier lifetime and diffusion length in silicon epitaxial layers by means of the photocurrent technique

A new method for the determination of minority carrier lifetime and diffusion length in thin silicon epitaxial layers was developed. Using a transparent MIS structure the surface recombination velocity was reduced below 25 cm/s. This method makes possible to determine minority carrier lifetime and also diffusion length much greater than the thickness of the epitaxial layer.     

Minoritätsträger-diffusionslängen in GaAs-epitaxieschichten—gegenüberstellung verschiedener messverfahren

Minority carrier diffusion lengths are measured in lightly $\text{n-}\text{doped}$ GaAs epitaxial layers. Three different measuring methods are applied. They use photoluminescence, surface photovoltage, and pulsed MIS-capacitors. For photoluminescence measurements the influence of a surface depletion layer is considered. The measured values of the diffusion length do not reveal any dependence on the majority carrier concentration, but they depend on the applied measuring method.     

Determination of diffusion length from within a confined regionwith the use of EBIC

A new method of extracting minority carrier diffusion length from within a confined region of material is presented in this paper. This technique uses the finite difference method and can be used on samples where the diffusion lengths are longer than the width of the region. This cannot be achieved using the conventional method, which evaluates the negative reciprocal of the slope of the EBIC signals line scan plotted on a semi-logarithmic scale. A limitation of this method is that the beam entrance surface of the sample is assumed to have negligible surface recombination     

Experimental investigation of the excess charge

The open-circuit voltage of about 600 mV developed by 0.1 ohm-cm silicon solar cells under air mass zero illumination is about 100 mV less than voltages predicted from simple diffusion theory. The lower measured voltages appear to be controlled by junction current transport processes associated with the thin top diffused layer. Mechanisms such as low n⁺ layer minority carrier lifetime and bandgap narrowing due to heavy doping effects (HDE) have been suggested to explain these results. Experimental determinations of the properties of the diffused layer are required to assess which of these mechanisms predominate. While direct measurement is difficult, an indirect measurement methodology exists by which the lifetime or transit time in the diffused layer can be obtained. Nine p-type, 1×2 cm, 〈111〉 orientation silicon wafers were phosphorus diffused at 880°C for 45 minutes using P0Cl₃. Open-circuit voltages of 595-612 mV, typical of all 0.1 ohm-cm cell voltages, were obtained. From the open-circuit voltage and short-circuit current, the diffusion controlled I₀ was obtained. In addition to illuminated I-V characteristics, the time constants from the Open-Circuit Voltage Decay method, and the minority carrier diffusion lengths in the base region were measured. The base region charge was determined using the base region diffusion length measured by an X-ray method. The data from these experiments combined with simple theory can imply the minority carrier time constant and the excess charge in the diffused layer. From this, certain conclusions are drawn about the relative roles of bandgap shrinkage and recombination rates in the diffused layer.     

Determination of material parameters from regions close to the collector using electron beam-induced current

The conventional method of extracting the minority carrier diffusion length using the electron beam-induced current (EBIC) technique requires that the electron beam be placed at region more than two diffusion lengths away from the collector. The EBIC signals obtained under this condition usually has low signal to noise ratio. In addition, the true diffusion length of the sample is initially unknown and hence it is difficult to estimate how close the beam can be placed from the collector. To overcome all these difficulties, a new method of extracting minority carrier diffusion length from the EBIC signal is proposed. It is shown that this method can be applied to EBIC signals obtained from regions close to the collector. It is also shown that the surface recombination velocity of the sample can also be obtained using this method. This theory is verified using EBIC data generated from a device simulation software.     

A critical evaluation of the effective diffusion lengthdetermination in crystalline silicon solar cells from an extendedspectral analysis

This note draws attention to possible errors when characterizing silicon solar cells by means of the effective minority carrier diffusion length L_b as defined in the paper on “Numerical modeling of textured silicon solar cells using PC1D” by Basore (1990). The approximations underlying the analytical expression for L _eff are critically reviewed. Their impact on the determination of the minority carrier bulk diffusion length L_b from L_eff is discussed for a 250-μm thick Si solar cell. It is found that considerable errors occur in the case of diffusion lengths larger than the cell thickness even when neglecting any measurement uncertainty     

A simple single-step diffusion and emitter etching process for high-efficiency gallium-antimonide thermophotovoltaic devices

A single-step diffusion followed by precise etching of the diffused layer has been developed to obtain a diffusion profile appropriate for high-efficiency GaSb thermophotovoltaic (TPV) cells. The junction depth was controlled through monitoring of light current-voltage (I–V) curves (photovoltaic response) during the post-diffusion emitter-etching process. The measured photoresponses (prior to device fabrication) have been correlated with the quantum efficiencies (QEs) and the open-circuit voltages in the fabricated devices. An optimum junction depth for obtaining the highest QE and open-circuit voltage is presented based on diffusion lengths (or minority carrier lifetimes), carrier mobility, and the typical diffused impurity profile in GaSb.     

Minority carrier diffusion lengths in liquid phase epitaxial InGaAsP and InGaAs

Minority carrier diffusion lengths were determined for InGaAsP and InGaAs layers grown by liquid phase epitaxy on (100)-InP substrates by measuring the variation of the short circuit photocurrent as a focussed laser beam was scanned along a beveled (~1°) p-n junction. The effect of lattice-mismatch on the hole diffusion length (λ_p) for n-type unintentionally doped InGaAsP layers (λg=1.15 μm) was investigated for mismatch values from -0.25% to +0.31%, with the longest diffusion length (L_p = 1.5 μm) occurring when the epitaxial layer was lattice-matched to the substrate. As the amount of mismatch increased, L_p decreased. Electron diffusion lengths, L_n, were determined for lattice-matched quaternary and ternary layers grown from Zn doped melts over a wide range of hole concentrations. At the lowest hole concentrations, p = 3 × l0¹⁵ and 1.4 × 10¹⁶ cm⁻³, the electron diffusion lengths were 3.5 and 2.5 μm for the quaternary and ternary, respectively. As the hole concentration increased, L_n decreased and at the highest concentration (p = 5 × 10su18,cn⁻³) L_n was 0.13 μm for InGaAsP and 0.83 un for InGaAs.