Unraveling Band-Tail Effects on Temperature-Dependent Emission in GaAsBi via Photoluminescence

The effect of Bi on the emission temperature sensitivity of GaAsBi remains a topic of debate, which hinders the design of optoelectronic devices. Band-tail states, which are critical for GaAsBi performance, are suspected to drive the discrepancy, but their effect remains unclear. This work resolves the key debate using an innovative dual-spectroscopy approach that combines temperature-dependent photoluminescence (PL) and transmission spectroscopy to decouple the contributions of band-tail states from intrinsic band-edge behavior. For GaAs_{1- x}Bi_x (x = 0.033, 0.048), the energy-temperature coefficients derived from transmission are composition-independent, while those derived from PL decrease by ≈40% with higher Bi content. This apparent contradiction originates from the thermalized carrier redistribution between the valence band and band-tail states at elevated temperatures and the intrinsic band-edge thermal sensitivity in the transmission spectra. The dual-spectroscopy approach is proven to be an effective method for clarifying the effects of band-tail states on the thermal sensitivity, and provides valuable guidance for the design of stable GaAsBi optoelectronic devices.