The effect of Er fraction on THz power generated by extrinsic-photoconductive ErAs:GaAs switches driven at 1550 nm

Two Er-doped-GaAs photoconductive (PC) switches have been studied in extrinsic mode with different Er fractions of 1% and 2%. The PC switches were driven with a 1550 nm ultrafast laser (hν = 0.56 U_G, U_G = 1.42 eV for GaAs) and exhibited different THz bandwidths and photoelectric responsivities. These experiments are aimed at optimizing the new extrinsic mode of generating THz radiation in ErAs:GaAs photoconductive devices. This is the first ever demonstration of generating THz power with extrinsic photoconductivity with a 2% Er ErAs:GaAs PC switch. We find that the PC switch with 2% Er concentration produced more THz power and the bandwidth was marginally better.