A high temperature vacuum annealing method for forming ohmic contacts to GaN and SiC

In this work we report on the high temperature annealing of Ti/Al and Cr/Al contacts on n-GaN by a vacuum annealing technique. This method consists of annealing the samples on a resistively heated tungsten strip, in vacuum, with an Ar background ambient of 5/spl times/10/sup -5/ Torr. Contact resistivities as low as 2.2/spl times/10/sup -5/ /spl Omega/-cm/sup 2/ and 4.1/spl times/10/sup -5/ /spl Omega/-cm/sup 2/ were obtained for Ti/Al and Cr/Al ohmic contact metallizations respectively. Auger profile analysis showed minimal oxidation of the Al surface in the vacuum annealed samples whereas high levels of O were observed in the furnace annealed case. A contact resistivity of 4.3/spl times/10/sup -4/ /spl Omega/-cm/sup 2/ was achieved for Si/Pt metallization on p-SiC.