Highly reproducible ideal SiC Schottky rectifiers: effects of surface preparation and thermal annealing on the Ni/6H-SiC barrier height

In this work, the effects of surface preparation and thermal annealing on the Ni/6H-SiC Schottky barrier height were studied by monitoring the forward I-V characteristics of Schottky diodes. The ideality factor n and the barrier height Phi(B) were found to be strongly dependent on the impurity species present at the metal/SiC interface. The physical mechanism which rules the Schottky barrier formation is discussed by considering the nature of the impurities left from the different surface preparation methods prior to metal deposition. In contrast, nickel silicide/SiC rectifiers (Ni2Si/6H-SiC), formed by thermal reaction of Ni/6H-SiC above 600 degreesC, have an almost ideal I-V curve, independent of the surface preparation. Further improvement in the barrier height distribution can be obtained by increasing the annealing temperature to 950 degreesC. This behaviour is discussed in terms of the silicide phases and the consumption of a SiC layer during the thermal reaction.