Subpicosecond luminescence studies of carrier dynamics in nitride semiconductors grown homoepitaxially by MBE on GaN templates

摘要

A new technique is presented that employs luminescence downconversion using an ultrashort gating pulse to enable the characterization of UV light emission from III-nitride semiconductors with subpicosecond temporal resolution.This technique also allows one to measure PL rise times and fast comonents of multiple decays in the subsequent time evolution of the PL intensity.Comparison of luminescence emission intensity and lifetime in GaN and AlGaN with approx0.1 Al content grown homoepitaxially on GaN templates with the same quantities measured in heteroepitaxial layers grown on sapphire indicate significant improvement in the homoepitaial layers due to reduction in dislocation density.Fast (<15 ps) initial decays in the AlGaN are attributed to localization associated with alloy fluctuations and subsequent recombination through gap states.