Electrical transport characteristics of Ni/Pd/n-GaN Schottky barrier diodes as a function of temperature

The electrical transport properties of Ni/Pd/n-GaN Schottky barrier diodes (SBDs) have been investigated in the wide temperature range of 100–425 K. An abnormal decrease in the experimental barrier height (ϕb) and an increase in the ideality factor (n) with a decrease in the temperature have been observed. The observed variation in ϕbo and n is attributed to the spatial barrier inhomogeneities in Schottky barrier height by assuming a Gaussian distribution (GD) of barrier heights (BHs) at 100–175 K and 175–425 K. The temperature-dependent current–voltage characteristics of the SBDs has shown a double Gaussian distribution giving mean barrier heights of 0.65 eV and 1.21 eV and standard deviations of 0.085 and 0.159 V, respectively. A modified ln (Io/T2)–q2σo2/2k2T2 versus 103/T   plot for the two temperature regions gives ϕbo¯ and A⁎ as 0.713 eV and 13.56 A cm− 2 K− 2, and 1.34 eV and 28.645 A cm− 2 K− 2 respectively. Such temperature dependence of modified Richardson plot and electrical parameters of Ni/Pd/n-GaN SBD can be explained based on the thermionic emission theory with double GD of BHs due to the barrier height inhomogeneities at the metal/semiconductor interface. The themionic field emission is considered as the phenomena responsible for the excess currents observed in both forward and reverse direction of Schottky barriers.