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

A unique metal-semiconductor-metal (MSM) photodetector has been fabricated using Sn incorporation in Ga₂O₃ 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 SnO₂ 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 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.