Ultrafast photoresponse and fabrication of freestanding LT-GaAs photoconductive devices

Xuemei Zheng; S. Wu; R. Adam; M. Mikulics; A. Foerster; J. Schelten; M. Siegel; P. Kordos; Roman Sobolewski

doi:10.1117/12.517006

8 August 2003 Ultrafast photoresponse and fabrication of freestanding LT-GaAs photoconductive devices

Xuemei Zheng, S. Wu, R. Adam, M. Mikulics, A. Foerster, J. Schelten, M. Siegel, P. Kordos, Roman Sobolewski

Proceedings Volume 5123, Advanced Optical Devices, Technologies, and Medical Applications; (2003) https://doi.org/10.1117/12.517006
Event: 2003 Chapter books, 2003, Bellingham, WA, United States

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.

Citation Download Citation

Xuemei Zheng, S. Wu, R. Adam, M. Mikulics, A. Foerster, J. Schelten, M. Siegel, P. Kordos, and Roman Sobolewski "Ultrafast photoresponse and fabrication of freestanding LT-GaAs photoconductive devices", Proc. SPIE 5123, Advanced Optical Devices, Technologies, and Medical Applications, (8 August 2003); https://doi.org/10.1117/12.517006

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