Defects and arsenic distribution in low-temperature-grown GaAs

We have used X-ray photoelectron spectroscopy (XPS) and variable energy positron beam spectroscopy (VEPBS) to study the excess arsenic and related defects in GaAs grown by molecular beam epitaxy at low temperatures (LT-GaAs). XPS shows about 1.3% excess arsenic in as-grown LT-GaAs and a non-uniform depth profile of arsenic concentration in the annealed LT-GaAs. From the S parameter, we obtain a non-uniform depth profile of defects in annealed LT-GaAs. From similarity between depth profiles of the S parameter and As concentration, we conclude that the positrons are trapped in vacancy complexes associated with arsenic clusters in the annealed LT-GaAs.