ELECTRON-DIFFUSION LENGTH AND ESCAPE PROBABILITY MEASUREMENTS FOR P-TYPE GAAS(100) EPITAXIES

According to the two-minima electron diffusion model of Spicer, James, and Moll [ W. E. Spicer, Quant. Rep. 9, April (1968); L. W. James and Z. L. Moll, Phys. Rev. 183, 740 (1969) ] for near threshold photoemission, minority-carrier diffusion length L and escape probability P for a variety of Beryllium doped GaAs(100) epitaxies grown by molecular beam epitaxy, have been obtained. These epitaxies, before being activated with cesium and oxygen by using the two-stages method described by Stocker and Goldstein [B. J. Stocker, Surf. Sci. 47, 501 (1975); B. Goldstein, ibid. 47, 143 (1975) ], were passivated in two different ways, (i) Chemically, with a 5:1:1 H2O:H2O2:H2SO4solution and (ii) by the deposition of a 700–800 Å thick antimony layer. A better performance of the samples using this last type of passivation is shown. In order to evaluate L and P from the electron diffusion model, it is necessary to know the dispersion relation of the absorption coefficient for each sample. They have been obtained from normal-incidence reflectance measurements by means of a Kramers-Krönig analysis. The electronic diffusion length values obtained ranged from 4.5 to 2.1 fim and the escape probabilities between 8.1 % and 20.2% for Be concentrations of 1X 1018and 1X1019cm~, respectively. © 1990, American Vacuum Society. All rights reserved.