Extremely low dark current and detection range extension of Ga2O3 UV photodetector using Sn alloyed nanostructures

Abstract

A unique metal–semiconductor–metal (MSM) photodetector has been fabricated using Sn incorporation in Ga2O3 forming SnxGa1-xO 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. SnxGa1-xO Ns are deposited on c-plane sapphire using low-pressure chemical vapour deposition. From the x-ray diffraction (XRD) results, existence of both SnxGa1-xO and tetragonal SnO2 MNs are confirmed. The XRD peak shifts in SnxGa1-xO are attributed to the integration of Sn with Ga forming a SnxGa1-xO 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 SnxGa1-xO and SnO2 Ns. Photo to dark current ratio (PDCR) of the fabricated photodetector is large (103) at 2 V bias with fast fall time of 0.18 s. The detector reveals self-powered behaviour also with PDCR >104 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.