Lifetime studies of self-activated photoluminescence in heavily silicon-doped GaAs

We report results of a detailed temperature dependence study of photoluminescence lifetime and continuous emission properties in silicon-doped GaAs. The primary focus is on a defect-related emission at 1.269 eV ($T=20$ K). GaAs crystals were grown using molecular-beam epitaxy with most of the experiments conducted on a sample having a carrier concentration of 4.9×{}10¹⁸ cm^-3. The intensity is seen to decrease above 100 K, with no corresponding decrease in the measured lifetime of 9.63±{}0.25 ns. The intensity decrease implies an activation energy of 19±{}2 meV, which is approximately one order of magnitude smaller than what was previously obtained for similar defects in Czochralski-grown GaAs with other dopants. We interpret our results in terms of a configuration coordinate model and obtain a more complete picture of the energy-level structure. The experiments indicate that the upper level in the recombination process is about 20 meV below the conduction-band continuum, with the lower state approximately 300 meV above the valence band. Our results are consistent with the identification of the corresponding defect complex microstructure as being a siliconat-gallium substitution, weakly interacting with a gallium vacancy second-nearest neighbor, known as the Si-Y defect complex.