Schottky barrier height and s-parameter of Ti, Cu, Pd, and Pt contacts on p-Type GaN

The Schottky barrier height (SBH) of Ti, Cu, Pd, and Pt contacts on p-GaN and their work-function dependence, the S-parameter, were investigated. According to thermionic emission model, the SBH was obtained to be 0.85, 0.70, 0.61, and 0.59 eV for Ti, Cu, Pd, and Pt, respectively, yielding an S-parameter of 0.19. However, the ideality factor was as large as ∼4 and anomalous temperature dependences of the SBH and ideality factors were observed, indicating that the pure thermionic emission is not appropriate to explain carrier transport. Based on the barrier inhomogeneity and thermionic field emission models, S-parameters of 0.27 and 0.38 could be reasonably obtained.