Enhanced Responsivity of GaN Metal–Semiconductor–Metal (MSM) Photodetectors on GaN Substrate

High spectra response of metal-semiconductor-metal (MSM) ultraviolet photodetectors (UV PDs) based on GaN epitaxial wafers with different diameters of Al nanodots on the surface were realized on free-standing GaN substrates. The UV PDs exhibit low dark current and high spectral response both at room temperature and 150 °C, demonstrating the thermal stability of the fabricated devices. The peak responsivities for the PDs with Al nanodot diameters of 60, 80, and 120 nm are 1.079, 2.420, and 3.096 A/W, showing an enhancement ratio of 32%, 196%, and 280%, respectively, compared to the referential PD without Al nanodots. Numerical investigations reveal that the significant enhancement performance is due to the localized surface plasmon effect, which enhances the localized electric field and produces more electron-hole pairs in the optoelectronic devices, leading to a higher responsivity. The results presented in this paper can promote the development and application for high performance GaN UV PDs.