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°C to 320°C. 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 (ΔR/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 ΔR/R reversed for LT-GaAs grown at 200°C. This is tentatively attributed to the band gap renormalization effect.