Highly reflective MgAl alloy/Ag/Ru Ohmic contact with low contact resistivity on p-type GaN

Abstract

We report a metallization scheme of high-reflectance low-resistance Ohmic contact on p-type GaN. The high reflectance of 84% at 460 nm wavelength and the specific contact resistivity as low as 8.59x10(-6) Omega cm(2) were obtained from MgAl-alloy(50 A)/Ag(3000 A)/Ru(500 A) annealed at 450 degrees C in air. The formation of Ag-Ga solid solution due to the outdiffusion of Ga after annealing leads to an Ohmic behavior of the contact. Employing highly reflective MgAl as a contact layer and Ru as an overlayer that suppress the agglomeration and the oxidation of the Ag result in the high reflectance of the contact. (C) 2007 American Institute of Physics.