ULTRAFAST PHOTOCONDUCTIVE DETECTORS BASED ON SEMIINSULATING GAAS AND INP

Photoconductive dipole antennas fabricated on semi-insulating (SI) GaA s and SI-InP were used to detect terahertz (THz) pulses. The responses of these long-carrier-lifetime photoconductive detectors were compare d to that of the photoconductive antenna fabricated on a low-temperatu re grown GaAs (LT-GaAs) with a subpicosecond carrier lifetime. The SI- InP-based photoconductive detector showed a higher responsivity and a better signal-to-noise ratio (SNR) than the LT-GaAs-based photoconduct ive detector at low gating laser powers. The SI-GaAs-based detector, h owever, showed a responsivity comparable to that of the LT-GaAs photoc onductive detector only at very weak gating laser power, and the SNR o f the SI-GaAs-based detector was poor for overall gating laser powers due to the high background noise originating from a large amount of st ray photocurrent.