Optical properties of metal-semiconductor-metal ZnO UV photodetectors

Linghui Li; Yungryel Ryu; Henry W. White; Ping Yu

doi:10.1117/12.843019

16 February 2010 Optical properties of metal-semiconductor-metal ZnO UV photodetectors

Linghui Li, Yungryel Ryu, Henry W. White, Ping Yu

Proceedings Volume 7603, Oxide-based Materials and Devices; 76031A (2010) https://doi.org/10.1117/12.843019
Event: SPIE OPTO, 2010, San Francisco, California, United States

Abstract

Among wide bandgap materials that are sensitive to photons in the ultraviolet (UV) region, ZnO is a promising photonic material because of its unique optoelectronic properties. Based on the lateral interdigitated back-to-back Schottky contact structure on ZnO film, metal-semiconductor-metal (MSM) photodetectors have substantially lower parasitic capacitance compared with vertical p-i-n photodetectors, which leads to a very high speed photodetection. In this paper, we report optical characteristics of MSM ZnO UV photodetectors for which ZnO films were fabricated by hybrid beam deposition. An annealing process was used in oxygen ambient. The MSM ZnO photodetector consists of two interdigitated electrodes both with Ti/Au metals on an n-type ZnO thin film. The electrodes on the photodetector are finger-shaped. We found that the annealing process decreases contact resistance and photoresponse time. The possible mechanism of annealing process is the removal of surface defects created in the fabrication process. A sublinear power dependence of photocurrent reveals the existence of a light induced space charge region inside the ZnO film. The device displays fast pulse response with a very short rise time and a relatively long relaxation time with applied bias. The exponential decay tail indicates an RC type time response.

Citation Download Citation

Linghui Li, Yungryel Ryu, Henry W. White, and Ping Yu "Optical properties of metal-semiconductor-metal ZnO UV photodetectors", Proc. SPIE 7603, Oxide-based Materials and Devices, 76031A (16 February 2010); https://doi.org/10.1117/12.843019

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