Disorder and the Urbach edge in dilute bismide GaAsBi

The characteristic emission from tail states below the bandgap of GaAsBi/GaAs quantum wells is studied using photoluminescence spectroscopy over a 10–300 K temperature range and a 0.1–1000 mW pump power range. The tail states exhibit two characteristic energies: A deeper one that is temperature independent at 29 meV and one nearer to bandgap that is temperature dependent, broadening from 17 meV at 10 K–29 meV at room temperature. The tail states are thought to originate from localization of the Bi states and disorder effects due to alloy fluctuations and clustering on the group-V sublattice.