Solar-blind UV Schottky barrier photodetectors formed by Au/Ni on β-(AlxGa1-x)2O3/AlGaN heterostructures

In this study, (AlxGa1-x)(2)O-3 films are formed through thermal oxidation on AlxGa1-xN/n-GaN heteroepitaxial layers. The process temperature and duration time are controlled to leave a part of the AlxGa1-xN layer and form (AlxGa1-x)(2)O-3/AlxGa1-xN/n-GaN heterostructures. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses are performed on the thermally treated AlxGa1-xN to determine the presence of (AlxGa1-x)(2)O-3 films in the AlxGa1-xN/n-GaN heteroepitaxial layers. The oxidized AlxGa1-xN and GaN layers exhibit XRD peaks at 59.2 degrees and 59.4 degrees corresponding to the diffraction (603) planes of beta-Ga2O3 and beta-(AlxGa1-x)(2)O-3 phases, respectively. The XPS spectra of the Ga3d and O1s core levels peak at 20.5 and 531.1 eV, confirming the presence of Ga-O bonds, i.e., the formation of a Ga2O3 and/or (AlxGa1-x)(2)O-3 thin film. In particular, Ni/Au and Ti/Al bilayer metal contacts are deposited on the (AlxGa1-x)(2)O-3 and n-GaN layers, respectively, in the (AlxGa1-x)(2)O-3/AlxGa1-xN/n-GaN heterostructures to form Schottky barrier photodetectors (SB PDs). Under a reverse bias of 1 V, (AlxGa1-x)(2)O-3 SB PDs exhibit a typical responsivity of around 6 A W-1 with an incident light wavelength of 225 nm, and the rejection ratio (at 225 nm vs. at 370 nm) of responsivity is as high as similar to 104. In addition, two cut-off wavelengths at 225 and 330 nm correspond to the bandgaps of (AlxGa1-x)(2)O-3 and AlxGa1-xN layers, respectively, in the (AlxGa1-x)(2)O-3/AlxGa1-xN/n-GaN heterostructures, and the Al content in (AlxGa1-x)(2)O-3 is 16%.