Determination of the diffusion length and the optical self absorption coefficient using EBIC model

We have developed a model of calculation of the induced current due to an e lectron beam. The expression for the electron beam induced current (EBIC) w ith an extended generation profile is obtained via the resolution of a stea dy state continuity equation by the Green function method, satisfying appro priated boundary conditions to the physical model. The generation profile t akes into account the lateral diffusion, the effect of defects, dislocation s and recombination surfaces besides the number of absorbed electrons and t hat of diffuse electrons as a function of the depth. In the case of a Schot tky diode Au/GaAs obtained by metalorganic vapour phase epitaxy (MOVPE) met hod, the theoretical induced current profile is compared to the experimenta l one and to theoretical profiles whose analytical expressions are given by van Roosbroeck and Bresse. The minority carriers diffusion length L-n = 2 mum and the optical self-absorption coefficient a = 0.034 mum(-1) can be de duced 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 velocit y 10(6) cm s(-1) except for distances far from the depletion layer (x(0) > 2.3 mum) where the photocurrent produced by the multiple process of the rea bsorbed recombination radiation is preponderant. Our results are in agreeme nt with those obtained by other experimental techniques on the same samples .