Impact of surface morphology on the electrical properties of Al/Ti Ohmic contacts on Al-implanted 4H-SiC

This paper reports on the impact of the surface morphology on the properties of Ti/Al Ohmic contacts fabricated on AI-implanted 4H-SiC. In particular, the surface roughness of the Al-implanted regions after annealing at 1700 degrees C was strongly reduced by the using a protective carbon capping layer during annealing (the surface roughness decreased from 9.0 nm to 1.3 nm). In this way, also the morphology and the specific contact resistance of Ti/Al Ohmic contacts formed on the implanted regions could be improved. The electrical and morphological data were correlated with the structural properties of the reacted metal layer and of the metal/SiC interfacial region.