Terahertz-Wave Characterization of LTG-GaAs Thin-Film Photoconductive Antenna

Low temperature grown (LTG) Gallium Arsenide (GaAs) thin-film based photoconductive antennas (PCAs) are fabricated and their terahertz (THz) performance is compared with conventional bulk LTG-GaAs PCAs. To fabricate the LTG-GaAs thin-film based PCAs, LTG-GaAs thin-films are separated from their semi-insulating (SI)-GaAs substrate and integrated onto bow-tie PCA electrode tips patterned on a silicon dioxide (SiO
₂
) layer thermally grown on a silicon (Si) substrate. Conventional bulk LTG-GaAs PCAs are fabricated by direct photolithography and metallization on the surface of a conventional bulk LTG-GaAs material. THz waves radiated from each of the excited PCA emitters are characterized by a variation of applied bias voltages maintaining the incident optical pump power constant at 10 mW. It was observed that the peak THz radiation signal from the LTG-GaAs thin-film based PCA is higher than the one obtained from the conventional bulk LTG-GaAs PCA structure with the same bias voltage and optical pump laser beam conditions. The performance difference was analyzed using numerical simulations. Based on the unique integration structure, the LTG-GaAs thin-film based PCAs have a potential to improve the THz radiation and enable heterogeneously integrated THz systems.