Photoresponse Characteristics of a Graphene Quantum Dot/GaN Metal–Semiconductor–Metal Ultraviolet Photodetector

In this study, the contact characteristics of graphene quantum dots (GQDs) formed on n-type GaN semiconductors are investigated. Blue-luminescent GQDs prepared using a hydrothermal method are sprayed onto a GaN wafer, and the electrical and optical properties of the fabricated contacts are investigated. The GQD/GaN contacts exhibit rectifying behavior with a typical Schottky barrier height of 0.64 eV. A metal–semiconductor–metal (MSM) photodiode with interdigitated GQD contacts on n-type GaN is fabricated and provides an extremely low dark current. The spectral photoresponse of the GQD/GaN MSM photodiode includes a sharp increase in responsivity at wavelengths shorter than 375 nm. The responsivity of the MSM photodiode is remarkably improved with increasing the GQD reduction temperature (up to 800 °C), showing a good photoresponse in the ultraviolet region.