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Proceedings Paper

Ultrafast photoresponse and fabrication of freestanding LT-GaAs photoconductive devices
Author(s): Xuemei Zheng; S. Wu; R. Adam; M. Mikulics; A. Foerster; J. Schelten; M. Siegel; P. Kordos; Roman Sobolewski
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Paper Abstract

We report on fabrication and ultrafast photoresponse of novel, freestanding low-temperature-grown GaAs (LT-GaAs) photoconductive (PC) devices. 1-μm-thick, LT-GaAs single-crystal films were grown by molecular beam epitaxy at the temperature range of 200°C to 250°C. Next, the films were patterned to the desired device sizes, lifted-off from their host substrates, and placed on predetermiend places on either SiO2/Si or MgO wafers. Our freestnding LT-GaAs devices consisted of either approximately 20-μm by 20-μm PC switches, or 150-μm by 150-μm metal-semiconductor-metal (MSM) interdigitated structures with Ti/Au fingers patterned directly on top of the LT-GaAs film. For testing purposes, our devices were integrated with Ti/Au coplanar striplines, fabricated directly on SiO2/Si and MgO substrates. The test structures were illuminated with 100-fs-wide optical pulses and their time-resolved photoresponse was measured with an electro-optic sampling system, characterized by 200-fs time resolution and sub-millivolt sensitivity. Using 810-nm optical excitation, we recorded as narrow as 360-fs-wide electrical signals (1.25 THz, 3-dB bandwidth) for PC switches, resulting in 155 fs carrier lifetime in our freestanding LT-GaAs. For both types of devices, the photoresponse amplitude was a linear function of the applied voltage bias, as well as a linear function of the laser excitation power, below well-defined saturation thresholds. Our freestanding photo-switches are robust and very reproducible. They are best suited for applications in hybrid optoelectronic and ultrafast electronic systems, since they can be placed at virtually any point on a test circuit.

Paper Details

Date Published: 8 August 2003
PDF: 11 pages
Proc. SPIE 5123, Advanced Optical Devices, Technologies, and Medical Applications, (8 August 2003); doi: 10.1117/12.517006
Show Author Affiliations
Xuemei Zheng, Univ. of Rochester (United States)
S. Wu, Univ. of Rochester (United States)
R. Adam, Research Ctr. Julich (Germany)
M. Mikulics, Research Ctr. Julich (Germany)
A. Foerster, Research Ctr. Julich (Germany)
J. Schelten, Research Ctr. Julich (Germany)
M. Siegel, Research Ctr. Julich (Germany)
P. Kordos, Research Ctr. Julich (Germany)
Roman Sobolewski, Univ. of Rochester (United States)

Published in SPIE Proceedings Vol. 5123:
Advanced Optical Devices, Technologies, and Medical Applications
Janis Spigulis; Janis Teteris; Maris Ozolinsh; Andrejs Lusis, Editor(s)

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