Possible current-transport mechanisms in the (Ni/Au)/Al0.22Ga0.78N/AlN/GaN Schottky barrier diodes at the wide temperature range

The current-transport mechanisms of (Ni/Au)/Al0.22Ga0.78N/AlN/GaN Schottky barrier diodes (SBDs) have been investigated in the wide temperature range of 80-400 K. The analysis of the main electrical characteristics such as zero-bias barrier height (Phi(B0)), ideality factor (n) and series resistance (R-s) were found strongly temperature dependent. The conventional Richardson plot of ln (I-0/T-2) vs. 10(3)/T show two linear regions in the temperature range of 80-200 K and 240-400 K. The value of Richardson constant (A*) obtained from these two linear regions were found to be 3.25 x 10 (12) and 1.28 x 10 (9) A/cm(2) K-2, respectively, which are much lower than the theoretical value of 27.64A/cm(2) K-2. While Phi(B0) increases, n decreases with increasing temperature. Such temperature dependent of Richardson plot and main electrical parameters can be explained on the basis of the thermionic emission (TE) theory with double Gaussian distribution (GD) of the barrier heights (BHs) due to the barrier height (BH) inhomogeneities at the metal/semiconductor (M/S) interface. Therefore, the modified (ln(I-0/T-2) - q(2)sigma(2)(0)/2k(2)T(2)) vs. q/kT gives the mean BHs ((Phi) over bar (B0)) of 1.40 and 0.68 eV and standard deviation sigma(s) of 0.184 and 0.082 V, respectively. We also found that the values of R-s obtained from Cheung's method depend strongly on temperature and abnormally increased with increasing temperature. (C) 2010 Elsevier B.V. All rights reserved.