Ultrahigh Detectivity Broad Spectrum UV Photodetector with Rapid Response Speed Based on p‐β Ga<sub>2</sub>O<sub>3</sub>/n‐GaN Heterojunction Fabricated by a Reversed Substitution Doping Method
Yurui Han, Yuefei Wang, Shihao Fu, Jiangang Ma, Haiyang Xu, Bingsheng Li, Yichun Liu
Abstract
Abstract An excellent broad‐spectrum (220–380 nm) UV photodetector, covering the UVA‐UVC wavelength range, with an ultrahigh detectivity of ≈10 15 cm Hz 1/2 W −1 , is reported. It is based on a p‐β Ga 2 O 3 /n‐GaN heterojunction, in which p‐β Ga 2 O 3 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 β‐phase Ga 2 O 3 films. SIMS and XPS indicate that the residual N atoms as dopants remain in β Ga 2 O 3 . 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 β Ga 2 O 3 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 × 10 15 cm Hz 1/2 W −1 (255 nm) and 1.1 × 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‐β Ga 2 O 3 /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.