Controlling interface oxygen for forming Ag ohmic contact to semi-polar (11-22) plane p-type GaN

Abstract

Low-resistance Ag ohmic contacts to semi-polar (11-22) p-GaN were developed by controlling interfacial oxide using a Zn layer. The 300 degrees C-annealed Zn/Ag samples showed ohmic behavior with a contact resistivity of 6.0 x 10(-4) Omega cm(2) better than that of Ag-only contacts (1.0 x 10(-3) Omega cm(2)). The X-ray photoemission spectroscopy (XPS) results showed that annealing caused the indiffusion of oxygen at the contact/GaN interface, resulting in the formation of different types of interfacial oxides, viz. Ga-oxide and Ga-doped ZnO. Based on the XPS and electrical results, the possible mechanisms underlying the improved electrical properties of the Zn/Ag samples are discussed. (C) 2014 Elsevier Ltd. All rights reserved.