High-temperature structural behavior of Ni/Au contact on GaN (0001)

Abstract

We investigated the structural evolution of the Ni/Au contact on GaN (0001) during annealing in N(2), using in-situ x-ray diffraction, anomalous x-ray scattering, and high resolution electron microscopy. GaN decomposition occurred mostly along GaN dislocations at temperature higher than 500 degreesC. The decomposed Ga diffused into Au and Ni substitutional positions, and the decomposed nitrogen reacted with Ni, forming Ni(4)N. Interestingly, Ni(4)N was grown epitaxially. The epitaxial relationship of the Ni(4)N, Au, and Ni was identified as M (111)//GaN (0002) and M[1 -1 0]//GaN[1 1 -20] (M= Ni(4)N, Au, and Ni). At dislocation free regions, however, the atomically smooth interface remained intact up to 700 degreesC. Remarkable improvement of device reliability is expected in the contact on dislocation free regions compared with the contact on dislocations.