Fabrication and subpicosecond optical response of low-temperature-grown GaAs freestanding photoconductive devices

We have fabricated and tested freestanding low-temperature-grown GaAs photoconducting devices exhibiting subpicosecond photoresponse. The epitaxially grown thin-film microswitches were transferred on top of sapphire and Si/SiO(2) substrates and integrated with Ti/Au coplanar strip transmission lines. Our devices exhibited above 200 V breakdown voltages and dark currents at 100 V below 3 x 10(-7) A. The photoresponse of our microswitches was measured using electro-optic sampling technique with 100-fs-wide laser pulses at wavelengths of 810 nm and 405 nm as the excitation sources. For 810-nm excitation, we measured 0.55-ps-wide electrical transients with voltage amplitudes of up to 1.3 V. The ultraviolet excitation resulted in 1.35-ps-wide transients due to the hot carriers generation and intraband relaxation. (C) 2002 American Institute of Physics.