High-detectivity nanowire photodetectors governed by bulk photocurrent dynamics with thermally stable carbide contacts

Photodetectors fabricated from one-dimensional semiconductors are always dominated by the surface states due to their large surface-to-volume ratio. Therefore, the basic 5S requirements (high sensitivity, high signal-to-noise ratio, high spectral selectivity, high speed, and high stability) for practical photodetectors are difficult to satisfy. We report on high-temperature and high-detectivity solar-blind deep-ultraviolet (DUV) photodetectors based on β-Ga₂O₃ nanowires, in which the photoresponse behavior is dominated by the bulk instead of the surface states. Ohmic contact to the β-Ga₂O₃ nanowires was achieved by using a thermally stable tungsten carbide electrode. As a result, the DUV responsivity at 250 nm shows the highest values - 4492 A W^-1 at room temperature (RT) and 3000 A W^-1 at 553 K (280 ° C) - among the DUV photodetectors. The detectivity is as high as 1.26×10¹⁶ cm Hz^1/2 W^-1 at RT, and still remains 4.1×10 ¹⁴ cm Hz^1/2 W^-1 at as high a temperature as 553 K. The photocurrent dynamics from the β-Ga₂O₃ nanowire is discussed in terms of the bulk dominated photoresponse behavior. Other wide bandgap DUV detectors based on nanostructures could also be developed for high-temperature applications based on this work. © 2013 IOP Publishing Ltd.