Epitaxial graphene/SiC Schottky ultraviolet photodiode with orders of magnitude adjustability in responsivity and response speed.

A simple optical-electronic device that possesses widescale adjustability in its performance is specially required for realizing multifunctional applications as in optical communication and weak signal detectors. Here, we demonstrate an epitaxial graphene (EG)/n-type SiC Schottky ultraviolet (UV) photodiode with extremely widescale adjustability in its responsivity and response speed. It is found that the response speed of the device can be modulated over seven orders of magnitude from tens of nanoseconds to milliseconds by changing its working bias from 0 to −5 V, while its responsivity can be varied by three orders of magnitude. A 2.18 A/W responsivity is observed at −5 V when a 325 nm laser is irradiated on, corresponding to an external quantum efficiency over 800% ascribed to the trap induced internal gain mechanism. These performances of the EG/SiC Schottky photodiode are far superior to those based on traditional metal/SiC and indicate that the EG/n-type SiC Schottky diode is a good candidate for application in UV photodetection. [ABSTRACT FROM AUTHOR]