Correlation between defect concentration and carrier lifetime of GaAs grown by molecular beam epitaxy at different temperatures

Abstract

A pump-probe study of GaAs grown by molecular beam epitaxy at low temperatures (LT-GaAs) is performed. Ultrashort carrier lifetimes of the as-grown LT-GaAs increase from <0.13 ps (measurement limitation) to 1.8 +/-0.2 ps as the growth temperature is increased from 200 degreesC to 320 degreesC. The carrier lifetime was found to be approximately inversely proportional to the antisite defect concentration. This trend is found to be in reasonably good agreement with the Schokley-Read-Hall model. The decreasing trend in the amplitudes of continuous-wave and transient reflectivities (DeltaR/R) as a function of the growth temperature for the LT-GaAs is explained as an induced absorption caused by dense arsenic antisite defects. The sign of the transient DeltaR/R reversed for LT-GaAs grown at 200 degreesC. This is tentatively attributed to the band gap renormalization effect.