Temperature variation of current–voltage characteristics of Au/Ni/n-GaN Schottky diodes

Current–voltage (I–V) characteristics of Au/Ni/n-GaN Schottky diodes have been measured in 40–320 K temperature range, and analyzed in terms of thermionic emission theory by incorporating the concept of barrier inhomogeneity at the metal/semiconductor interface through a Gaussian distribution function. The basic diode parameters such as ideality factor and barrier height were consequently extracted from electrical measurements. It was seen that ideality factors increased and barrier heights decreased with the decreasing temperature. Both the barrier height (Φ¯b) and the ideality factor (n) exhibit abnormal temperature dependence and are explained by invoking three sets of Gaussian distributions of barrier heights at 320–160 K, 160–80 K, and 80–40 K. An experimental barrier height (BH) Φap value of about 0.963 eV was obtained for the Au/Ni/n-GaN Schottky diode at the room temperature (300 K). From the temperature-dependent I–V   characteristics of the Ni/Au/n-GaN contact, that is, Φ¯bo and A* as 1.38±0.02, 0.87±0.02 and 0.51±0.02 eV; 47.91±2, 12.44±0.5 and 46.72±2 A/cm2 K2, respectively, have been calculated from a modified ln(I0/T2)−q2σs2/2k2T2 vs. 1/T plot for the three temperature regions.