Simulation Design of Asymmetric Schottky Electrodes and their Influence on the Self-powered Photodetection Performance of GaN-based MSM Photodetector

Asymmetric GaN-based metal-semiconductor-metal photodetectors were designed, and the influence of asymmetric electrodes on the working principle and self-powered photodetection performance of device were numerically studied. Due to the different work functions of the two electrodes, the asymmetric Pt-GaN-Al structure shows the largest difference in the Schottky barrier height of 0.5 eV, and exhibits the most obvious asymmetry of dark I-V curve. Without applied bias, it also performs the highest IL/ID ratio of 7.57x1010 and strong response at the wavelength of 280-360 nm with the peak responsivity of 0.27A/W, while the symmetric Pt-GaN-Pt structure has extremely low response of about 6.0x10-5A/W, proving the excellent self-powered detection performance of the asymmetric MSM photodetector. The built-in potential gradient in the asymmetric MSM structure caused by the different Schottky barrier heights at both contacts is the key for the self-powered characteristic. It results in different carrier separation and transport efficiency, and then drives the photogenerated electrons and holes to flow into different contacts, thus realizing the self-powered photodetection performance.