Electrical characterization of inhomogeneous Ti/4H–SiC Schottky contacts

Forward I(V) measurements of Titanium/4H–SiC Schottky rectifiers are presented in a large temperature range. Significant dispersion is observed on the room temperature characteristics. Some of the rectifiers show good agreement with the thermionic model. Other samples present excess current at low voltage level. For these rectifiers we have been able to fit the experimental characteristics assuming the coexistence of low and high barrier height areas. In this model, the forward current results from the addition of the thermionic currents provided by the two parallel diodes. Forward I(V) measurements as a function of temperature have been performed from 100 to 600 K. On a given diode, a transition between one barrier and two barriers behaviours can be evidenced as temperature changes. Variations in the calculated barrier height and ideality factor are therefore evidenced. It is shown that the excess current at low voltage depends on the ratio of the low Schottky barrier region over the total diode area. Material inhomogeneity is one possible explanation for the existence of inhomogeneous barrier height on the Ti/4H–SiC contact.