Se/MoOx Hole-Selective Contact for β-Ga2O3 Heterojunction Diodes

Beta-gallium oxide β-Ga2O3 is a promising material for next-generation ultra-wide bandgap (UWBG) semiconductor power devices and deep UV photodetectors. Achieving reliable p-type conductivity remains a significant challenge. To overcome this difficulty, the well-developed approach in literature involves the formation of a p-n heterojunction by deposition of p-type NiOx. However, the intrinsic resistivity of NiOx is still too high >102 .cm and the doping control by Ni vacancies may cause reliability issue when operating in an oxygen environment. In this work, we propose an alternative device architecture that uses the deposition of selenium (Se) and molybdenum oxide (MoOx) for forming a heterojunction with Ga2O3 as a selective contact. The Se/MoOx stack acts as the hole-selective contact, and gold (Au) is used as the top anode. For this preliminary demonstration, silver paste was employed as the backside cathode contact on Ga2O3.Static I–V measurements exhibit strong rectifying behavior, with a barrier height of 1.09 eV and an ideality factor of 1.15 at room temperature. Under reverse bias, the device exhibits a low leakage current of 20 pA at −10 V.To evaluate band alignment, XPS valence band measurements will be combined with optical bandgap estimation to determine the band offsets at the Se/MoOx/β-Ga2O3 heterointerface. Deep-level characterization using capacitance transient spectroscopy is currently underway. These results, together with deep-ultraviolet photodetection measurements, will be presented at the conference.