Electrical activity of defects in molecular beam epitaxially grown GaAs on Si and its reduction by rapid thermal annealing

Abstract

The electrical activity of defects in GaAs grown on Si by molecular beam epitaxy (MBE) has been examined by studying the diode characteristics and deep level transient spectroscopy (DLTS) of Schottky barriers. The defects are not apparent from the forward bias diode characteristics but they are indicated by large leakage current and early breakdown under reverse-biased conditions. Post-growth rapid thermal annealing (RTA) has been found to significantly improve the diode behavior making it almost comparable to GaAs-on-GaAs. The reverse current in the as-grown material shows a very weak temperature dependence, indicating that its origin is not thermionic emission or carrier generation. It is speculated that a large part of this current is due to defect-assisted tunneling, which is reduced by RTA. DLTS indicated only a modest increase in the concentrations of the well-known electron traps typical of MBE GaAs with no evidence for new levels in the upper half of the band gap.