Carrier Lifetime and Mobility in GaAsNBi Alloys*

III-V alloys incorporating Nitrogen and Bismuth are of significant interest for optoelectronic applications in the near- and mid-infrared. We report measurements of the photoconductivity lifetime and photocarrier mobility in a series of GaAs_1-x-yN_xBi_y samples grown on GaAs by MBE. We find short conductivity lifetimes of order 3ps to 5ps and carrier mobilities of order 30 to 80cm²/Vs. Time-resolved photoconductivity was obtained from optical pump, THz probe measurements, and steps were taken to avoid the influence of the GaAs substrate: A tunable optical pump permitted excitation below the GaAs bandgap, and transient THz reflection was used as a surface-specific probe of the conductivity. The short carrier lifetime and low carrier mobility likely arises due to rapid carrier trapping in these materials.