Exceptional Responsivity (>6 kA/W) and Dark Current (<70 fA) Tradeoff of n-Ga2O3/p-CuO Quasi-Heterojunction-Based Deep UV Photodetector

Reduction of high dark current has been a challenge for high responsivity photodetector (PD). In this context, the present article demonstrates an ultralow dark current of Ga ₂ O ₃ -based deep ultraviolet (UV)photodetectors (UV-PDs) with enhanced photoresponses by tailoring a p/n heterojunction. An n-Ga ₂ O ₃ /p-CuO quasi-heterostructure-based deep UV-PDs has been fabricated on a sapphire (0001) substrate using an inexpensive electrospraying technique. After Ga ₂ O ₃ deposition, platinum (Pt) electrodes (~50 nm) are fabricated as a metal-semiconductor-metal (MSM) device using sputtering. The device exhibits a very low dark current in the order of few fA (6.94 × 10 ^-14 A) at 5 V because of the enhanced depletion width at p/n heterojunction and Pt/Ga ₂ O ₃ metal-semiconductor contacts, which provides a narrow path for free carriers to travel from one metal contact to other under dark condition. The depletion layers get thinner due to the absorption of UV-photons in the UV-illumination condition. Hence, the photogenerated carriers get a wider channel to get collected at Pt-electrodes. Thus, in addition to ultralow dark current, the device exhibits an extraordinary photodetection characteristics, such as a high responsivity (~6.33 × 10 ³ AW ^-1 ), remarkable phototo-dark current ratio (~2.99 × 10 ⁶ ), very high detectivity (~4.44 × 10 ¹⁴ mHz ^0.5 W ^-1 ), and exceptional external quantum efficiency of ~3.1 × 10 ⁶ % at 5 V.