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

We report ultrafast (∼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 μA at a bias of 40 V. The carrier mobility of the former is ∼590 cm²/V s, resulting in a small-signal optical responsivity of ∼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). [ABSTRACT FROM AUTHOR]