Comparative study of the current transport mechanisms in Ni2Si Ohmic contacts on n- and p-type implanted 4H-SiC

The knowledge of the temperature behavior of Ohmic contacts is an important issue to understand the device operation. This work reports on an electrical characterization as a function of the temperature carried out on nickel suicide (Ni2Si) Ohmic contacts, used both for n-type and p-type implanted 4H-SiC layers. The temperature dependence of the specific contact resistance suggested that a thermionic field emission mechanism dominates the current transport for contacts on p-type material, whereas a current transport by tunneling is likely occurring for the contacts on n-type implanted SiC. Furthermore, from the temperature dependence of the electrical characteristics, the activation energies for Al and P dopants were determined, resulting of similar to 145 meV and similar to 35 meV, respectively. The thermal stability of the electrical parameters has been demonstrated upon a long-term (up to similar to 100 hours) cycling in the temperature range 200-400 degrees C.