Influence of low-energy electron beam irradiation on defects in activated Mg-doped GaN

Abstract

The effect of low-energy electron beam irradiation (LEEBI) on residual hydrogen impurities and native defects in activated metalorganic vapor phase epitaxy-grown Mg-doped (p-type) GaN layers was studied by cathodoluminescence (CL) microanalysis and spectroscopy at temperatures between 80 and 300 K. The LEEBI treatment dissociates (Mg–H)0 complexes producing (i) at 300 K, a significant increase in a free-to-bound transition (e,Mg0) centered at 3.26 eV and (ii) at 80 K, a substantial decrease in a H–Mg donor–acceptor pair emission at 3.27 eV. In-plane and depth-resolved CL imaging reveals a direct correlation between the spatial distribution of the injected carriers and the depth and lateral distribution of activated Mg acceptors. This finding strongly suggests that hydrogen dissociation results from electron-hole recombination at hydrogen defect complexes rather than heating by the electron beam. The results at 80 K indicate that the process of dissociation of hydrogen from (Mg–H)0 complexes is accompanied by a generation of additional defect centers. It is proposed that following LEEBI hydrogen does not leave the specimen, but instead associates with nitrogen vacancies, generating additional recombination channels.