Electrical Characterization of Inhomogeneous Ni<sub>2</sub>/Si/SiC Schottky Contacts

Abstract

Abstract. The electrical characterization of nickel silicide (Ni 2 Si) Schottky contacts on 4H-SiC is reported in this work. In spite of the nearly ideal behaviour observed at room temperature ( n =1.05), a deviation from the ideality was observed at lower temperatures, thus suggesting that an inhomogeneous Schottky barrier has actually formed. The experimental results were described by the Tung’s model on inhomogeneous Schottky barriers, which considers low barrier regions embedded in a uniform high barrier Ni 2 Si contact. The inhomogeneity of the barrier is responsible of the commonly observed discrepancy between the experimental values of the Richardson’s constant A ** (i.e. 2.6 A/cm 2 K 2 in our contacts) from its theoretical value of 146 A/cm 2 K 2 in 4H-SiC. Introduction Silicon carbide Schottky diodes are very attractive devices because of their capability to reach high switching frequencies under high voltage operation and with a low on-resistance when compared to analogous silicon devices [1]. In spite of the progresses already achieved in the technology of SiC Schottky diodes, obtaining a barrier with nearly ideal electrical behaviour may represent an outstanding problem. In fact, the control of the surface preparation before metal deposition affects the uniformity of the Schottky barrier height Φ