title: Femtosecond response of a free-standing LT-GaAs photoconductive switch.
abstract: We present a novel, free-standing low-temperature GaAs (LT-GaAs) photoconductive switch and demonstrate its femtosecond performance. A 1-microm-thick layer of a single-crystal LT-GaAs was patterned into 5-10-microm-wide and 15-30-microm-long bars, separated from their GaAs substrate and, subsequently, placed across gold coplanar transmission lines deposited on a Si substrate, forming a photoconductive switch. The switch was excited with 110-fs-wide optical pulses, and its photoresponse was measured with an electro-optic sampling system. Using 810-nm optical radiation, we recorded an electrical transient as short as 360 fs (1.25 THz, 3-dB bandwidth) and established that the photo-carrier lifetime in our LT-GaAs was 150 fs. Our free-standing devices exhibited quantum efficiency of the order of approximately 7%, and their photoresponse amplitude was a linear function of the applied voltage bias, as well as a linear function of the excitation power, below a well-defined saturation threshold.
authors.affiliation: Department of Electrical and Computer Engineering and the Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14627-0231, USA. xuzheng@ece.rochester.edu
authors.forename: Xuemei
authors.initials: X
authors.lastname: Zheng
authors.forename: Ying
authors.initials: Y
authors.lastname: Xu
authors.forename: Roman
authors.initials: R
authors.lastname: Sobolewski
authors.forename: Roman
authors.initials: R
authors.lastname: Adam
authors.forename: Martin
authors.initials: M
authors.lastname: Mikulics
authors.forename: Michael
authors.initials: M
authors.lastname: Siegel
authors.forename: Peter
authors.initials: P
authors.lastname: Kordos