Carrier lifetime versus anneal in low temperature growth GaAs

Abstract

The photoexcited carrier lifetimes in ex situ‐annealed low temperature growth GaAs are measured with a femtosecond transient absorption experiment. The study encompassed two low temperature growth GaAs films with approximately 0.3% and 0.9% excess arsenic incorporated during growth. The observed lifetimes are found to be a function of the spacing of arsenic precipitates formed during the 30 s anneals to temperatures between 650 and 1000 °C. The carrier lifetime for unannealed films was found to be less than ∼200 fs. The carrier lifetimes increased from ∼2 to ∼10 ps as the average precipitate spacing was increased from ∼400 to ∼900 Å. These results are in sharp contrast to recent reports of subpicosecond lifetimes in similar GaAs annealed at 600 °C.