Double Gaussian Distribution of Inhomogeneous Barrier Height in (Ni-Au)/Al0.25Ga0.75N/GaN

The forward current-voltage (Ig-Vg) properties of the (Ni-Au)/Al0.25Ga0.75N/GaN/SiC structure were examined in the temperature range of 50-320K. Temperature has considerable influence on the zero-bias barrier height (phi(B0)), series resistance (Rs),and ideality factor (n).Furthermore, the standard Richardson plots of ln(I-0/T-2) vs. 10(3)/T for this sample revealed two linear zones (50-230 K and 230-320 K). For Al0.25Ga0.75N, the Richardson constant (A*) values in the linear zones were less than the predicted value (34.2 Acm(-2)K(-2)).This phenomenon is linked to the Schottky barrier inhomogeneities by adopting a double Gaussian distribution (GD) of the barrier heights (BHs) at the (Ni-Au)/Al0.25Ga0.75N interface. We attempted to establish an indication of the double GD of BHs for this sample by plotting phi(B0) vs. q/2kT. As a result, the Ig-Vg temperature dependency was satisfactorily described using the thermionic emission hypothesis with a double GD of the BHs at the (Ni-Au)/Al0.25Ga0.75N interface. These findings indicate that the inhomogeneous distribution of the surface and/or interface states is linked to the lateral inhomogeneity of the Schottky BH which is attributed to the defect existence confirming prior findings using the capacitance deep-level transient spectroscopy method.