Comparison and Investigation of Ohmic Characteristics in the Ni/AuZn and Cr/AuZn Metal Schemes

Abstract

The Ni/AuZn and Cr/AuZn contacts for achieving a low resistance ohmic contact to moderately doped p-GaN(4.4×1017/cm3) have been reported. In order to determine the reasons for the difference in ohmic characteristics of both metals, we have compared the ohmic contact characteristics and investigated the interfacial reaction mechanism between metal and GaN. The specific contact resistance was measured to be ρc=3.6×10-3 Ωcm2 in Ni/AuZn and 2.3×10-2 Ωcm2 in Cr/AuZn. The interfacial reaction mechanism during annealing has been studied by secondary ion mass spectrometry (SIMS) measurement. From this measurement, it was observed that Ni and Cr interact with the p-GaN surface and these interfacial reactions promote the Zn diffusion upon thermal treatment. The electrical properties were studied using current–voltage (I–V) measurements at room temperature. The microstructure between the metal and p-GaN interface was investigated using transmission electron microscopy (TEM) before and after heat treatment.