Extremely low dark current and detection range extension of Ga ₂ O ₃ UV photodetector using Sn alloyed nanostructures

Abstract

Abstract A unique metal–semiconductor–metal (MSM) photodetector has been fabricated using Sn incorporation in Ga 2 O 3 forming Sn x Ga 1- x O nanostructures (Ns) with platinum (Pt) metal as contacts. The mixed nanostructures (MNs) has been attributed to an increment in the detection range of UV (254–302 nm) with ultra-low dark current, hence a potential device in the field of long range deep-UV detector. Sn x Ga 1- x O Ns are deposited on c-plane sapphire using low-pressure chemical vapour deposition. From the x-ray diffraction (XRD) results, existence of both Sn x Ga 1- x O and tetragonal SnO 2 MNs are confirmed. The XRD peak shifts in Sn x Ga 1- x O are attributed to the integration of Sn with Ga forming a Sn x Ga 1- x O alloy with x to be ∼7.3% determined from the Vegard’s law. The field effect scanning eletron microscope images show the thick diameter wire-shaped nanostructures. The absorption spectra show a trace of two absorption edges corresponding to both Sn x Ga 1- x O and SnO 2 Ns. Photo to dark current ratio (PDCR) of the fabricated photodetector is large (10 3 ) at 2 V bias with fast fall time of 0.18 s. The detector reveals self-powered behaviour also with PDCR >10 4 at 0 V bias. The dark current is ultra-low (13 pA at 5 V) due to high barrier height of Pt and the UV detection range has been extended from 254–302 nm with a very small drop in PDCR owing to incorporation of Sn.