Influence of Pt in a Ti-Al-Pt-Au ohmic contact on n-type GaN

Abstract

A number of alternative metallization has been used to obtain low ohmic contact resistance to n-type GaN. Of these, the most common is the bi-metal alloy of Ti-Al. Typical alloying temperatures used for this process are in the vicinity of 900 °C. We report that the addition of Pt and Au to the ohmic metal provides specific contact resistivity of the order of 4×10-5 Ω cm2 at temperatures in the vicinity of 700 °C. This makes the alloying step less demanding on both the material and the processing equipment. The paper also presents the effects of alloying temperature and the influence of the formation of an Al-Pt phase on the quality of the ohmic contact.