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

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 (10(-24) A(2)/Hz) up to 5 V, for the undoped GaN MSM detector. (C) 1999 American Institute of Physics. [S0003-6951(99)03005-3].