The study of impurity levels in LEC semi-insulating GaAs:Cr samples by two-source photoconductivity measurements

Abstract

Spectral photoconductivity curves of SI GaAs:Cr crystals are measured in the extrinsic region using the two light sources method; high intensity monochromatic illumination ensures steady‐state population of levels; and probe light of low intensity serves to measure corresponding photoconductivity curves. The set of obtained curves is decomposed into elementary contributions using the minimization program MINUIT. The obtained photoionization cross‐sections are compared with those from absorption measurements and interpreted as transitions involving Cr2+, Cr3+, and Cr4+ ions. The influence of interaction among impurities and of internal electric field on the photoionization cross‐section is discussed.