Ultrahigh Detectivity Broad Spectrum UV Photodetector with Rapid Response Speed Based on p-β Ga2O3/n-GaN Heterojunction Fabricated by a Reversed Substitution Doping Method

An excellent broad-spectrum (220-380 nm) UV photodetector, covering the UVA-UVC wavelength range, with an ultrahigh detectivity of approximate to 10(15) cm Hz(1/2) W-1, is reported. It is based on a p-beta Ga2O3/n-GaN heterojunction, in which p-beta Ga2O3 is synthesized by thermal oxidation of GaN and a heterostructure is constructed with the bottom n-GaN. XRD shows the oxide layer is (-201) preferred oriented beta-phase Ga2O3 films. SIMS and XPS indicate that the residual N atoms as dopants remain in beta Ga2O3. XPS also demonstrates that the Fermi level is 0.2 eV lower than the central level of the band gap, indicating that the dominant carriers are holes and the beta Ga2O3 is p-type conductive. Under a bias of -5 V, the photoresponsivity is 56 and 22 A W-1 for 255 and 360 nm, respectively. Correspondingly, the detectivities reach an ultrahigh value of 2.7 x 10(15) cm Hz(1/2) W-1 (255 nm) and 1.1 x 10(15) cm Hz(1/2) W-1 (360 nm). The high performance of this UV photodetector is attributed mainly to the continuous conduction band of the p-beta Ga2O3/n-GaN heterojunction without a potential energy barrier, which is more helpful for photogenerated electron transport from the space charge region to the n-type GaN layer.

Automated summary

This study reports an excellent broad-spectrum UV photodetector with a high detectivity. The device is based on a p-beta Ga2O3/n-GaN heterojunction and exhibits a continuous conduction band without a potential energy barrier, enabling efficient electron transport. The photodetector shows a high photoresponsivity and detectivity for different wavelengths ranging from 255 nm to 360 nm.