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Microstructural and electrical investigation of Ni/Au ohmic contact on p-type GaN

Research paper by Jong Kyu Kim, Jung Ho Je, Jae Won Lee, Yong Jo Park, Taeil Kim, In-Ok Jung, Byung-Teak Lee, Jong-Lam Lee

Indexed on: 01 Feb '01Published on: 01 Feb '01Published in: Journal of Electronic Materials



Abstract

Electrical properties of Ni/Au ohmic contacts on p-type GaN were interpreted with the change of microstructure observed under transmission electron microscopy. The contact resistivity was decreased from 1.3×10−2 to 6.1×10−4 Ωcm2 after annealing at 600°C. The reduction is due to the dissolution of Ga atoms into Au−Ni solid solution formed during annealing, via the generation of Ga vacancies. Thus, net concentration of holes increased below the contact, resulting in the reduction of contact resistivity. At 800°C, N atoms decomposed; reacted with Ni, and forming cubic Ni4N. Consequently, N vacancies, acting as donors in GaN, were generated below the contact, leading to the increase of contact resistivity to 3.8×10−2 Ωcm2.