Al0.18Ga0.82N/GaN Two-Dimensional Electron Gas-Based Ultraviolet Photodetectors With Symmetrical Interdigitated Structure

The fabrication and comprehensive characterizations of Al<inline-formula> <tex-math notation="LaTeX">$_{{0.18}}$ </tex-math></inline-formula>Ga<inline-formula> <tex-math notation="LaTeX">$_{{0.82}}\text{N}$ </tex-math></inline-formula>/GaN two-dimensional electron gas (2DEG)-based ultraviolet (UV) photodetector (PD) with symmetrical interdigitated structure are reported. The results reveal a good performance for the device with a responsivity of 800 A/W at 10 V corresponding to a high external quantum efficiency (EQE) of <inline-formula> <tex-math notation="LaTeX">$3.33\times 10^{{5}}$ </tex-math></inline-formula>% and a dark current of <inline-formula> <tex-math notation="LaTeX">$3\times 10^{-{8}}$ </tex-math></inline-formula> A at −8 V. Nevertheless, the rise time of 25 ms and the fall time of 21 ms are obtained by improving the transient response characteristic. Moreover, the fabricated 2DEG-based UV PD exhibits a broadband nature with response spectrum from 300 to 360 nm and a cutoff wavelength of 365 nm in agreement with the GaN bandgap. In addition, the performances of our devices are also optimized by varying the width and spacing of the interdigitated 2DEG structure. Furthermore, several physical models have been applied to convincingly explain the gain mechanism and high-temperature dark current transport mechanism of the proposed devices. This investigation paves the way for further improving the device detection capabilities.