Schottky barrier inhomogeneity in (Pd / Au) Al0.22 Ga0.78N/ GaN/SiC HEMT: Triple Gaussian distributions

The temperature dependence of electrical properties of (Au/Pd)/Al0.22 Ga0.78N/ GaN Schottky barrier diodes (SBDs) have been deeply analyzed by means of forward Igs (Vgs) measurements over the temperature range of 60-320 K. First results indicate that the barrier height (phi b), ideality factor (n) and series resistance (Rs) have demonstrated a strongly temperature dependence which suggesting the presence of barrier inhomogeneities at the interface. The effect of spatial inhomogeneity causes fluctuations in the barrier height around an average value. The series resistances obtained from Cheung's function are increasing with increasing temperature. Werner's model consisted in the Schottky contact modeling through inhomogeneities of the barrier which induces the presence of three different average barrier heights each associated with a standard deviation sigma. Such abnormal behavior is indeed due to the lateral inhomogeneity of the Schottky barrier, assuming three Gaussian distributions of the barrier height (BH) in three different temperature ranges of 220-320K, 120-200K, and 60-100K, respectively. The (Au/Pd)/ GaN Schottky barrier diode have been shown a Gaussian distribution giving mean s (phi b) of 0.83, 0.43 and 0.20 eV and standard deviation sigma of 139, 74.18 and 35.15 mV for the three temperature regions, respectively. A modified Richardson plot ln (I0/T2) - q2 sigma 2/2k2T2 vs. 1/kT have given phi b and A* as 0.95 eV and 10.56 A/cm2K2, 0.45 eV and 24.45A/cm2 K2, 0.20 eV and 28.18 A/cm2 K2, respectively. Moreover, the determination of the energy characteristic relating to the transmission probability by tunneling effect E00 made it possible to highlight two conduction modes: conduction by tunnel effect (FE) and a thermionic conduction assisted by field effect (TFE).