Ohmic contacts on n-type and p-type cubic silicon carbide (3C-SiC) grown on silicon

This paper is a report on Ohmic contacts on n-type and p-type type cubic silicon carbide (3C-SiC) layers grown on silicon substrates. In particular, the morphological, electrical and structural properties of annealed Ni and Ti/Al/Ni contacts has been studied employing several characterization techniques. Ni films annealed at 950 degrees C form Ohmic contacts on moderately n-type doped 3C-SiC (N-D similar to 1 x 10(17) cm(-3)), with a specific contact resistance of 3.7 x 10(-3) Omega cm(2). The main phase formed upon annealing in this contact was nickel silicide (Ni2Si), with randomly dispersed carbon in the reacted layer. In the case of a p-type 3C-SiC with a high doping level (N-A similar to 5 x 10(19) cm(-3)), Ti/Al/Ni contacts were preferable to Ni ones, as they gave much lower values of the specific contact resistance (1.8 x 10(-5 )Omega cm(2)). Here, an Al3Ni2 layer was formed in the uppermost part of the contact, while TiC was detected at the interface. For this system, a temperature dependent electrical characterization allowed to establish that the thermionic field emission rules the current transport at the interface. All these results can be useful for the further development of a device technology based on the 3C-SiC polytype.