GaN membrane MSM ultraviolet photodetectors

A. Muller; G. Konstantinidis; A. Kostopoulos; M. Dragoman; D. Neculoiu; M. Androulidaki; M. Kayambaki; D. Vasilache; C. Buiculescu; I. Petrini

doi:10.1117/12.695086

20 December 2006 GaN membrane MSM ultraviolet photodetectors

A. Muller, G. Konstantinidis, A. Kostopoulos, M. Dragoman, D. Neculoiu, M. Androulidaki, M. Kayambaki, D. Vasilache, C. Buiculescu, I. Petrini

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Proceedings Volume 6415, Micro- and Nanotechnology: Materials, Processes, Packaging, and Systems III; 641509 (2006) https://doi.org/10.1117/12.695086
Event: SPIE Smart Materials, Nano- and Micro-Smart Systems, 2006, Adelaide, Australia

Abstract

GaN exhibits unique physical properties, which make this material very attractive for wide range of applications and among them ultraviolet detection. For the first time a MSM type UV photodetector structure was manufactured on a 2.2 μm. thick GaN membrane obtained using micromachining techniques. The low unintentionally doped GaN layer structure was grown by MOCVD on high resistivity (ρ<10kΩcm) <111< oriented silicon wafers, 500μm thick. The epitaxially grown layers include a thin AlN layer in order to reduce the stress in the GaN layer and avoid cracking. Conventional contact lithography, e-gun Ni/Au (10nm /200nm) evaporation and lift-off techniques were used to define the interdigitated Schottky metalization on the top of the wafer. Ten digits with a width of 1μm and a length of 100μm were defined for each electrode. The distance between the digits was also 1μm. After the backside lapping of the wafer to a thickness of approximately 150μm, a 400nm thick Al layer was patterned and deposited on the backside, to be used as mask for the selective reactive ion etching of silicon. The backside mask, for the membrane formation, was patterned using double side alignment techniques and silicon was etched down to the 2.2μm thin GaN layer using SF₆ plasma. A very low dark current (30ρA at 3V) was obtained. Optical responsivity measurements were performed at 1.5V. A maximum responsivity of 18mA/W was obtained at a wavelength of 370nm. This value is very good and can be further improved using transparent contacts for the interdigitated structure.

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A. Muller, G. Konstantinidis, A. Kostopoulos, M. Dragoman, D. Neculoiu, M. Androulidaki, M. Kayambaki, D. Vasilache, C. Buiculescu, and I. Petrini "GaN membrane MSM ultraviolet photodetectors", Proc. SPIE 6415, Micro- and Nanotechnology: Materials, Processes, Packaging, and Systems III, 641509 (20 December 2006); https://doi.org/10.1117/12.695086

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