Photoelectrical characteristics of as-grown highresistance GaAs single crystals

Abstract

UDC 621.315.592 and А. V. TyazhevThe electrophysical and photoelectrical properties of high-resistance GaAs produced by single crystal growth are studied and analyzed. The electron (τ n ) and hole (τ p ) lifetimes are estimated. The charge-carrier lifetimes are compared in as-grown and diffusion high-resistance GaAs. The conclusion is made that in high-resistance GaAs produced by chromium diffusion, the charge-carrier recombination mechanism qualitatively differs from that in as-grown GaAs. The charge-carrier recombination in diffusion GaAs is determined by the occurrence of recombination barriers due to chromium diffusion.The use of high-resistance (HR) GaAs compensated with chromium during diffusion for the fabrication of ionizing radiation detectors [1,2] showed obvious advantages of this material as compared to high-resistance GaAs obtained by doping with chromium or EL2-centers during crystal growth. It is of physical and practical interest to find the reasons for the differences between the properties of diffusion and as-grown high-resistance GaAs. The results of studying the properties of the diffusion high-resistance material are reported in [3]. In this work, the electrophysical properties, photoconductivity, and photo-Hall effect are studied and the stationary charge-carrier lifetimes are calculated for as-grown HR GaAs.The electrophysical characteristics of the materials under study are summarized in Table 1. The characteristics are determined by measurements of conductivity and Hall-effect using the Van-der-Pouw technique. The electron and hole components are found from the solution of a system of equations (1), where σ* and R* are the dark conductivity and Hall constant, respectively. The solutions are obtained for the following conditions: μ n = 15μ p and (n i ) 2 = 2·10 12 cm -6 . The electron and hole Hall factors were taken to be equal to 1. Therefore, the