Photoluminescence of chromium doped and chromium diffused GaAs

Photoluminescence (PL) measurements on the 0.84 eV Cr-related PL line have been made on both Cr diffused and Cr doped GaAs. In the former case, no luminescence is observed below a diffusion temperature of 800°C. The form of the PL spectrum is found to be the same, independent of whether the majority donor species is group IV(Si) or group VI(Te). PL profiling experiments are used to show that the PL intensity is proportional to the concentration of chromium. Although it is possible that a group VI donor is involved, the insensitivity of the spectrum to different donor species and its linear dependence on chromium concentration suggest that the luminescent centre is a Cr_Ga-V_As] complex.Measurements on growth doped material are typified by the low intensity near the seed and the scatter in PL intensity in samples where the measured Cr] is nearly constant. By comparison with the results on the diffused material, the anomalously low PL intensity near the seed end is deduced to be indicative of the high crystal stoichiometry in this region.