Carrier masses and band-gap temperature sensitivity in Ga(AsBi) alloys

The effects of external perturbations-such as temperature, photo-excited carrier density, and magnetic field-on the electronic properties of Ga(AsBi) alloys are investigated in a large range of Bi-concentration (x up to similar to 11%). These studies allow us to disclose the existence of Bi-induced localized states that largely contribute to the recombination spectra up to relatively-high temperature (T similar to 150 K). The sensitivity of the band-gap energy to temperature variation is found to diminish strongly with Bi-concentration and to result in a reduction of about a factor of two at the highest concentrations. Magneto-photoluminescence studies have also revealed the role exerted by the Bi-induced levels on the host band states and have disclosed an unexpectedly strong carrier-carrier scattering, which hampers the observation of Landau-level quantization at low magnetic fields. An unusual compositional dependence of the exciton reduced mass, as well as an unexpected increase of the electron effective mass at relatively-low Bi-concentration (x < 6%), are reported and related to the presence of Bi-induced states.