Highly Reflective Ag/La Bilayer Ohmic Contacts to p-Type GaN

Abstract

A new Ag/La bilayer metal contact scheme has been developed for producing high reflectance and low contact resistivity ohmic contacts to p-GaN. An excellent reflectance of over 91% at 460 nm wavelength and low specific contact resistivity of 1.6 x 10(-4) Omega cm(2) were obtained from Ag/La (150/20 nm) contact annealed at 450 degrees C for 1 min. The La overlayer was oxidized to form La(2)O(3) when exposed to air, which effectively suppresses exposure of the Ag layer to oxygen atmosphere during annealing, leading to a good ohmic contact with smooth surface morphology and high reflectance. Additionally, Ag/La contacts show excellent thermal stability after a long thermal annealing at 300 degrees C in air ambient. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3533673] All rights reserved.