High-speed, low-noise metal–semiconductor–metal ultraviolet photodetectors based on GaN

Abstract

We present the fabrication and characterization of nonintentionally doped GaN and GaN:Mg Schottky metal–semiconductor–metal (MSM) photodetectors, grown on sapphire by metalorganic chemical vapor deposition. Low-leakage, Schottky contacts were made with Pt/Au. The devices are visible blind, with an ultraviolet/green contrast of about five orders of magnitude. The response times of the MSM devices were <10 ns and about 200 ns for GaN and GaN:Mg, respectively. The noise power spectral density remains below the background level of the system ${\text{(10}}^{\text{−24}} {\mathrm{A}}^{\mathrm{2}}\mathrm{/Hz})$ up to 5 V, for the undoped GaN MSM detector.