The current-voltage ( I-V) characteristics of metal-insulator-semiconductor (Al/GaN/p-GaAs) Schottky barrier diodes (SBDs) were investigated over a wide temperature range of 80-380 K. By using the thermionic emission (TE) theory, the zero bias barrier height Phi(B0) calculated from I-V characteristics was found to increase with increasing temperature as the ideality factor n decreases with increasing temperature, and especially the activation energy plot is nonlinear at low temperatures. The observed variation in the Phi(B0) and n is attributed to the spatial barrier inhomogeneities in SBD by assuming a Gaussian distribution (GD) of barrier heights (BHs). The experimental I-V-T characteristics of the SBDs have shown a double Gaussian distribution having mean barrier heights (Phi) over bar (B) of 0.854 eV and 0.395 eV and standard deviations sigma(s) for 0.142 V and 0.059 V, respectively. The modified ln( I-0/T-2)-q(2)sigma(2)(0)/2(kT)(2) vs q/kT plot gives Phi(B0) and Richardson constant A* as 0.858 eV and 0.364 eV, and 78.5 and 128 A/cm(2)K(2), respectively, without using the temperature coefficient of the barrier height. Hence, the results have shown that the I-V-T characteristics of the Al/GaN/p-GaAs SBDs can be successfully explained on the basis of TE mechanism with a double Gaussian distribution of the barrier heights.