Richardson’s constant in inhomogeneous silicon carbide Schottky contacts

The electrical characterization of nickel silicide Schottky contacts on silicon carbide (4H–SiC) is reported in this article. In spite of the nearly ideal behavior of the contact at room temperature $\text{(n=1.05),}$ the electrical behavior monitored in a wide temperature range exhibited a deviation from the ideality at lower temperatures, thus suggesting that an inhomogeneous barrier has actually formed. A description of the experimental results by the Tung’s model, i.e., considering an effective area of the inhomogeneous contact, provided a procedure for a correct determination of the Richardson’s constant $A^{\mathrm{**}}.$ An effective area lower than the geometric area of the diode is responsible for the commonly observed discrepancy in the experimental values of $A^{\mathrm{**}}$ from its theoretical value in silicon carbide. The same method was applied to Ti/4H–SiC contacts.