A SEM-EBIC minority-carrier diffusion-length measurement technique

A SEM-EBIC minority-carrier diffusion-length measurement technique is described, whereby an arrangement is used such that the electron beam is incident normal to the charge-collecting barrier; the barrier may be either that of a Schottky diode or of a shallow p-n junction. The beam is slowly moved away from the barrier and the diffusion length is found by analyzing the resulting EBIC decay. It is shown that in many practical cases this decay is given byI(d) propto exp (-d/L)/d^{3/2}whereLis the diffusion length and d the beam-to-diode distance. Some experimental details concerning the application of the technique are discussed, and finally the technique is used to measure the diffusion length of a number of Si and GaP samples.     

Differential photocurrent method for measurement of the optical-absorption coefficient and the minority-carrier diffusion length in a semiconductor

A new method, named DPC (differential-photocurrent), is proposed for measuring the optical-absorption coefficient and the minority-carrier diffusion length in a semiconductor. In the DPC method, a sample photodiode under a reverse bias, which is modulated at a frequency f2, is illuminated by an incident light chopped at a frequency f1, where f1and f2are close, and the DPC of the diode is measured. The method is free from limitations due to effects of surface recombination, surface reflectivity, and photon-transmission coefficient of surface layer. The optical-absorption coefficient for an n-type     

On the theoretical basis of the surface photovoltage technique

A complete theory for the constant-magnitude steady-state surface photovoltage (SPV) technique is developed. Emphasis is placed on the determination of the minority-carrier diffusion length. The theory is derived from the basic transport mechanisms in semiconductors with minimal assumptions. The recombination of electron-hole pairs in the surface depletion region is incorporated explicitly.     

Quantitative surface photovoltage spectroscopy of semiconductor interfaces

A comprehensive and quantitative method for extracting the important parameters of interface states is presented. The method is based on wavelength-, intensity-, and time-resolved surface photovoltage spectroscopy, as well as on measurements as a function of the thickness of an overlayer. Data analysis provides detailed information about interface state properties, including their energy position and distribution, density, and the transition probabilities, i.e. their thermal and optical cross sections. It is also possible to distinguish between surface and bulk states, and determine the spatial site of the states in the case of a heterostructure. Experimental examples for various III-V and II-VI compound semiconductors are given.     

A simple method of calculating the minority-carrier current in heavily doped silicon

It is shown that the calculation of the one-dimensional minority-carrier current density in heavily doped silicon can be described by two coupled differential equations of the first order. These equations are derived with a minimum of assumptions and approximations and without the explicit use of an electric field. The relevant input parameters to these equations are the product of the equilibrium hole density with the diffusion coefficient and the product of the equilibrium hole density with the reciprocal value of the lifetime. These equations can very easily be solved numerically and the solution gives the minority-carrier density and the current density as a function of space coordinate. It is shown that values of the band gap narrowing cannot be derived from current measurements alone.     

Determination of minority-carrier lifetime and surface recombination velocity with high spacial resolution

Quantitative analysis of the electron beam induced current in conjunction with high-resolution scanning makes it possible to evaluate the minority-carrier lifetime three dimensionally in the bulk and the surface recombination velocity two dimensionally, with a high spacial resolution. The analysis is based on the concept of the effective excitation strength of the carriers which takes into consideration all possible recombination sources. Two-dimensional mapping of the surface recombination velocity of phosphorus-diffused silicon diodes is presented as well as a three-dimensional mapping of the changes in the minority-carrier lifetime in ion-implanted silicon.     

Microwave transmission method for measuring minority-carrier lifetime in silicon slices

A microstrip transmission method is described for measuring minority-carrier lifetime in thin silicon slices. This method is used to correct results published earlier by Makios and Thomas, using the HP 8410 network analyser as a microwave interferometer. Measured results for high-resistivity samples are shown to extend the earlier curves of Ross and Madigan.     

Microwave measurement of surface resistance by the parallel-platedielectric resonator method

Analysis and experimental results are presented for a parallel-plate dielectric resonator method to measure the surface resistance of conducting or superconducting plates. In the present paper, three main questions are considered in detail: the influence of the relative sizes of the conducting or superconducting plates on the measured value of the surface resistance R_s; the influence of the shape of the plates on the R_s measurement; and how to interpret obtained results. Measurements were made at resonant frequencies of 14.1-14.5 GHz in a temperature range between 77 and 300 K     

Theory of surface photovoltage in a semiconductor with a Schottky contact

An analytical theory of surface photovoltage is developed for a semiconductor with a Schottky contact. The theory is able to predict, for light with small to large absorption coefficients, the photon flux required to yield a specified photovoltage, taking into account the three current components that describe the internal behaviour of the semiconductor, namely, the surface current, the space-charge recombination current and the bulk diffusion current. Detailed modelling of these current components is done with the help of exact numerical solutions of the drift-diffusion transport equations. The validity of the theory is confirmed by comparison with exact numerical solutions over a wide range of doping concentrations and minority-carrier lifetimes.     

基于组合面型基准件的多参数测量方法

针对运动物体空间多维位姿检测过程繁琐、设备笨重及昂贵等问题,提出了一种可以完成运动体4个参数同时测量的光学非接触测量方法。该系统由旋转抛物面与平面构成的组合面型基准件和光学测头两部分组成。基于平面镜反射原理和组合面型基准件的面型特征,分别建立了运动轴的俯仰角、偏摆角和二维位移的角度测量模型,并完成了系统的精度评价与重复性实验。实验结果表明:该系统的测角精度为1.5,位移精度为1 m,为机床误差辨识打下了基础。     

Determination of the oxygen precipitate-free zone width in silicon wafers from surface photovoltage measurements

A procedure has been developed for applying the surface photovoltage technique to the measurement of the width of the oxygen precipitate-free zone present at the surface of a thermally processed, Czochralski-grown silicon wafer. This procedure was developed through the use of a numerical simulation program which models the experimental determination of an effective diffusion lenght, L₀, from surface photovoltage measurements on silicon wafers. The program predicts L₀ for a given precipitate-free zone diffusion length and thickness and bulk diffusion length. Results of the simulations show that for bulk diffusion lengths of 2 μ or less and a precipitate-free zone diffusion length greater than the thickness of the zone, W, the W ≡ 2.5L₀. Experimental results are presented which support the numerical findings.     

Investigation of the photovoltage in por-Si/p-Si structures by the pulsed-photovoltage method

Photovoltaic phenomena in the structures por-Si/p-Si were investigated by the pulsed photovoltage method in the time interval 100 ns-10 ms using irradiation with nanosecond laser pulses with photon energies 1.4, 2.0, 2.8, and 3.7 eV. The data obtained show that besides the barrier photovoltage, due to the separation of nonequilibrium charge carriers in the space-charge region of p-Si at the por-Si/p-Si interface, there also exists an efficient mechanism of photovoltage formation due to charging of the surface of the por-Si nanostructure. This mechanism is explained as “optical doping” of a semiconductor and develops in a manner peculiar to semiconductor nanostructures. Fiz. Tekh. Poluprovodn. 32, 613–619 (May 1998)     

Determination of the diffusion length of charge minority carriers using digital oscillography of surface photovoltage

A procedure for determining the diffusion length of charge minority carriers (CMCs), which uses digital oscillography to detect surface photovoltage (SPV), is considered. It is shown by experiments that the shape of pulses of SPV, excited by rectangular IR pulses, depends significantly on both their intensity and wavelength. It is shown that it is not valid to use a synchronous detector to measure the quasi-stationary SPV when determining the diffusion length of CMCs in semiconductors, because, in a number of cases, it results in an uncontrollable error that reaches 100% and more. A technique is developed for determining the diffusion length in silicon wafers and epitaxial structures with the specific resistance range 0.01–12 Ω cm, the diffusion length range 5–500 μm, and an error of not more than 8%.     

一种无触点快速测量表面粗糙度的方法

提出一种使用激光束快速测量表面粗糙度的无触点光学方法。一束照射在样品表面的激光束随着表面粗糙度的增大反射光的密度分布将被扩展,可用PCD测出从铝制样品表面反射光的密度分布。被反射光的密度曲线可通过高斯函数近似地求出。密度分布曲线的宽度由高斯曲线系数的标准差计算出来,此标准差近似等于密度曲线的高斯函数的标准差,密度曲线的中线平均粗糙度随着高斯曲线系数的增加而增加。粗糙度Ra在0.1～0.5μm的范围内,可利用实验公式Ra=0.088GCP+0.032通过测量GCP得到。     

Interface studies of the m.i.s. structure by surface photovoltage measurements

A method is described whereby the surface-state density of an m.i.s. structure can be measured over a fairly wide range of energies in the band gap. The method involves measurements of the surface photovoltage at moderate light intensities. Results obtained by this method are shown to be in good agreement with those obtained by other methods.     

On the error associated with the MIS method of capacitance measurement of surface state density

The inherent error associated with the deduction of surface capacitance from measured MIS capacitance is considered. It is shown that the systematic component of the experimental error does not restrict the range of applications of the technique whereas any random contribution can invalidate the measurement in certain cases.     

Analysis of minority-carrier transport in polysilicon devices

Key assumptions are made, with justification, to simplify the three-dimensional, nonlinear boundary-value problem that defines minority-carrier transport, including recombination, in polysilicon devices. These assumptions enable the separation of the grain-boundary recombination analysis, which is based on quasi-equilibrium in the space-charge region, from the intragrain transport analysis, which is done by partitioning the grain into subregions in which the minority-carrier flow is predominantly one-dimensional. The analyses are coupled through the effective minority-carrier recombination velocity at the grain boundary, which generally is dependent on the minority-carrier density in the quasi-neutral grain. Limitations of the model implied by the quasi-equilibrium assumption are effectively removed by recognizing that when conditions obtain that negate quasi-equilibrium, the effective recombination velocity is fixed at the minority-carrier kinetic-limit velocity. The model development is facilitated by computer-aided numerical analysis of the grain-boundary recombination and is supported by qualitative discussion of the underlying physics.     

Measurement of the minority-carrier lifetime using an MOS capacitor

A simple technique is described for the measurement of the minority-carrier recombination lifetime using an MOS capacitor operating as a charge injection device. Device lag resulting from the incompleteness of the charge injection process is measured as a function of the injection pulse width. An approximate diffusion model consisting of only one adjustable parameter, the recombination lifetime, is able to explain the observed lag data. The values of the recombination lifetime thus obtained are in good agreement with those measured by photoconductive decay for a variety of Si samples. This technique permits a more definitive measurement of the minority-carder lifetime in fabricated devices than presently used procedures, without requiring high-quality devices. This technique should be particularly useful for evaluating III-V and II-VI compound semiconductors because MOS capacitors with a low density of interface states often are not available.     

一种加热炉炉管表面红外检测温度的修正方法

加热炉炉管表面温度检测的准确性直接关系到加热炉的运行状态和生产安全,利用红外热像仪测量炉管温度时易受到火焰和烟气、邻近炉管、炉墙辐射等因素的强烈干扰。为了实时准确获取炉管表面的真实温度,以某炼油厂加热炉为例,首先给出了炉管表面热红外检测温度的干扰分析,进而提出一种基于现场参数的实时温度校正模型,并结合该模型给出一套判别某厂加热炉炉管状态的专家规则,最后将这套软件应用于实际工程检验。研究结果表明,该方法有效实现了炉管表面的温度修正。