Annealing and Arsenic Overpressure Experiments on Defects in Gallium Arsenide

Previous experiments reported by the authors revealed a measurable expansion in the lattice constant of GaAs single crystals quenched from temperatures above 1000°C. These results led to the conclusion that a defect structure consisting of both Frenkel pairs and Schottky vacancies was produced in these crystals. In this paper we report experiments in which an arsenic overpressure, obtained by including metallic arsenic along with the GaAs crystal, depresses the defect concentration. These results are used to identify the primary defect species as arsenic monovacancies. Subsequent heat treatments at both room temperature and high temperature show that annealing proceeds in two stages. The first stage is quite rapid but does not have a well-defined activation energy. The second stage is slower and has an activation energy of 1.0 eV. These results are interpreted to include the presence of arsenic interstitial atoms. A physical model is proposed to describe the defect structure as well as the annealing behavior and the effect of excess arsenic pressure.