Electron mobility in dilute GaAs bismide and nitride alloys measured by time-resolved terahertz spectroscopy

We report time-resolved terahertz spectroscopy measurements of the electronic transport properties of dilute GaAs bismide and nitride alloys. The electron mobility for GaAs1−yBiy (y=0.84%) extracted from Drude fits to the transient complex conductivity was ∼2800cm2∕Vs at a carrier density of 2.7×1018cm−3, close to the mobility of 3300cm2∕Vs measured for GaAs at a similar carrier density. The electron mobility did not decrease significantly for Bi concentrations up to 1.4%. In contrast, the GaNxAs1−x (x=0.84%) and GaNxAs1−x−yBiy (x=0.85%, y=1.4%) films exhibited non-Drude behavior with a highly reduced electron mobility and suppressed conductivity at low frequencies indicative of carrier localization.