MSM Solar-Blind Ultraviolet Detector Incorporating Asymmetric Contact Electrodes Fabricated on AlₓGa₁–ₓN Hetero-Epilayers

In this work, we investigate the ability of a newly fabricated metal–semiconductor–metal (MSM) solar-blind ultraviolet (UV) photodetector (PD). Three Al $_{\textit{X}}$ Ga $_{\text{1}-\textit{X}}$ N films with different Al content were used to form heterostructures, and different metal stacks were deposited on their two sides to achieve asymmetric contact electrodes. The device exhibited a dark current of 2.53 $\times$ 10 $^{-\text{8}}$ A and a peak responsivity of 2.86 at $-$ 9 V, while corresponding dark current and peak responsivity at 9 V are 4.90 $\times$ 10 $^{-\text{7}}$ A and 20.19 A/W, respectively. Furthermore, its response speed was faster under reverse bias than forward bias. Two-dimensional device simulations were used to obtain the bias-dependent energy bands, electric fields, and carrier concentrations to explain the discrepancy of detection performances between different bias polarities.