High-Performance Ultraviolet Photodetectors Based on Nanoporous GaN with a GaO Single-Crystal Layer.

The utilization of a nanoporous (NP) GaN fabricated by electrochemical etching has been demonstrated to be effective in the fabrication of a high-performance ultraviolet (UV) photodetector (PD). However, the NP-GaN PD typically exhibits a low light-dark current ratio and slow light response speed. In this study, we present three types of UV PDs based on an unetched GaN, NP-GaN distributed Bragg reflector (DBR), and NP-GaN-DBR with a GaO single-crystal film (GaO/NP-GaN-DBR). The unetched GaN PD does not exhibit a significant photoresponse. Compared to the NP-GaN-DBR PD device, the GaO/NP-GaN-DBR PD demonstrates a larger light-dark current ratio (6.14 × 10) and higher specific detectivity (8.9 × 10 Jones) under 365 nm at 5 V bias due to its lower dark current (3.0 × 10 A). This reduction in the dark current can be attributed to the insertion of the insulating GaO between the metal and the NP-GaN-DBR, which provides a thicker barrier thickness and higher barrier height. Additionally, the GaO/NP-GaN-DBR PD device exhibits shorter rise/decay times (0.33/0.23 s) than the NP-GaN-DBR PD, indicating that the growth of a GaO layer on the DBR effectively reduces the trap density within the NP-GaN DBR structure. Although the device with a GaO layer presents low photoresponsivity (0.1 A/W), it should be feasible to use GaO as a dielectric layer based on the above-mentioned reasons.