Determination of the diffusion length and the optical self absorption coefficient using EBIC model
作者:S. Guermazi、H. Guermazi、Y. Mlik、B. El Jani、C. Grill、A. Toureille
DOI:10.1051/epjap:2001192
日期:2001.10
We have developed a model of calculation of the induced current due to an electron beam. The expression for the electron beam induced current (EBIC) with an extended generation profile is obtained via the resolution of a steady state continuity equation by the Green function method, satisfying appropriated boundary conditions to the physical model. The generation profile takes into account the lateral diffusion, the effect of defects, dislocations and recombination surfaces besides the number of absorbed electrons and that of diffuse electrons as a function of the depth. In the case of a Schottky diode Au/GaAs obtained by metalorganic vapour phase epitaxy (MOVPE) method, the theoretical induced current profile is compared to the experimental one and to theoretical profiles whose analytical expressions are given by van Roosbroeck and Bresse. The minority carriers diffusion length Ln = 2 µm and the optical self-absorption coefficient a = 0.034 µm−1 can be deduced from the experimental current profile, measured by scanning electron microscopy. The theoretical curve, obtained from the proposed model is in a good agreement with the experimental one for surface recombination velocity 106 cm s−1 except for distances far from the depletion layer (x0 > 2.3 µm) where the photocurrent produced by the multiple process of the reabsorbed recombination radiation is preponderant. Our results are in agreement with those obtained by other experimental techniques on the same samples.
我们开发了一种电子束感应电流计算模型。电子束感应电流(EBIC)的表达式是通过格林函数法解决稳态连续性方程,并满足物理模型的适当边界条件而得到的。生成曲线考虑了横向扩散、缺陷、位错和重组面的影响,以及作为深度函数的吸收电子数和扩散电子数。以通过金属有机物气相外延(MOVPE)方法获得的肖特基二极管 Au/GaAs 为例,将理论感应电流曲线与实验曲线以及 van Roosbroeck 和 Bresse 所给出的分析表达式的理论曲线进行了比较。少数载流子扩散长度 Ln = 2 µm 和光学自吸收系数 a = 0.034 µm-1 可以通过扫描电子显微镜测量的实验电流曲线推导出来。在表面重组速度为 106 cm s-1 的情况下,根据所提出的模型得到的理论曲线与实验曲线非常吻合,但在远离耗尽层的距离(x0 > 2.3 µm)处除外,在那里,由再吸收重组辐射的多重过程产生的光电流占主导地位。我们的结果与其他实验技术在相同样品上获得的结果一致。