Insight into the Epitaxial Growth of High Optical Quality GaAs1-xBix

The ternary alloy GaAs_1-xBi_x is a potentially important material for infrared light emitting devices, but its use has been limited by poor optical quality. We report on the synthesis of GaAs_1-xBi_x epi-layers that exhibit narrow, band edge photoluminescence similar to other ternary GaAs based alloys, e.g., In_yGa_1-yAs. The measured spectral linewidths are as low as 14 meV and 37 meV at low temperature (6 K) and room temperature, respectively, and are less than half of previously reported values. The improved optical quality is attributed to the use of incident UV irradiation of the epitaxial surface and the presence of a partial surface coverage of bismuth in a surfactant layer during epitaxy. Comparisons of samples grown under illuminated and dark conditions provide insight into possible surface processes that may be altered by the incident UV light. The improved optical quality now opens up possibilities for the practical use of GaAs_1-xBi_x in optoelectronic devices.