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

Abstract

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 °C form Ohmic contacts on moderately n-type doped 3C-SiC (ND ~1 × 1017 cm−3), with a specific contact resistance of 3.7 × 10−3 Ω cm2. 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 (NA ~5 × 1019 cm−3), Ti/Al/Ni contacts were preferable to Ni ones, as they gave much lower values of the specific contact resistance (1.8 × 10−5 Ω cm2). 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.