Dark current and trailing-edge suppression in ultrafast photoconductive switches and terahertz spiral antennas fabricated on multienergy arsenic-ion-implanted GaAs

We report ultrafast (similar to 2.7 ps, instrument limited) switching responses of a multienergy- implanted GaAs:As' photoconductive switches (PCSs) with suppressed trailing edge and reduced dark. current. This material is highly resistive with dark current as low as 0.94 mu A at a bias of 40 V. The carrier mobility of the former is similar to 590 cm(2)/V s, resulting in a small-signal optical responsivity of similar to 2 mA/W. Pumped at 100 mW and biased at 80 V, the multienergy-implanted GaAs: As+ PCS exhibits peak response (0.35 V) comparable to the best result of single-energy-implanted ones. The improvement on photoconductive response is crucial for the generation of shorter terahertz emission pulses from spiral antennas fabricated on multienergy-implanted GaAs:As+ (0.8 ps) than single-energy-implanted GaAs (1.2 ps), with the central frequency blueshifted to 0.2 THz (from 0.15 THz) and the spectral bandwidth broadened to 0.18 THz (from 0.11 THz). (c) 2005 American Institute of Physics.