Role of Oxygen in Reducing Silicon Contamination of GaAs during Crystal Growth

Abstract

GaAs grown in a horizontal Bridgman crystal growth apparatus to which oxygen has been added exhibits lower silicon content than that grown without oxygen. Material grown under oxygen additions of 10–20 Torr exhibits, at room temperature, carrier densities in the 2–4×1015 cm−3 range and mobilities between 7500–8650 cm2 V−1 sec−1. Silicon concentrations computed from the reaction 4Ga+SiO2 → 2Ga2O+Si are compared with electrical determinations of donor densities and spectroscopic determinations of silicon concentrations with reasonably good agreement. It is concluded that suppression of SiO2 dissociation at the walls of the silica reaction tube is the most important action of oxygen on GaAs properties although oxygen doping may play a role in the production of high resistivity GaAs.