The current-conduction mechanisms of the as-deposited and annealed at 450 degrees C (Ni/Pt) Schottky contacts on AlInGaN quaternary alloy have been investigated in the temperature range of 80-320 K. The zero-bias barrier height (BH) (Phi(B0)) and ideality factor (n) of them were evaluated using thermionic emission (TE) theory. The Phi(B0) and n values calculated from the I-V characteristics show a strong temperature dependence. Such behavior of Phi(B0) and n is attributed to Schottky barrier inhomogeneities. Therefore, both the Phi(B0) vs n and Phi(B0) vs q/2kT plots were drawn to obtain evidence on the Gaussian distribution (GD) of the barrier height at the metal/semiconductor interface. These plots show two different linear parts at low and intermediate temperatures for as-deposited and annealed Schottky contacts. Thus, the mean value of Phi(B0) and standard deviation (sigma(0)) was calculated from the linear parts of the Phi(B0) vs q/kT plots for both samples. The values of the effective Richardson constant (A*) and mean BH were obtained from the modified Richardson plots which included the effect of barrier inhomogeneity. These values of Richardson constant and barrier height for as-deposited contacts were found to be 19.9 A cm(-2) K-2 and 0.59 eV, respectively, at low temperature, but 43.3 A cm(-2) K-2 and 1.32 eV, respectively, at intermediate temperatures. These values of Richardson constant and barrier height for annealed contacts were found to be 19.6 A cm(-2) K-2 and 0.37 eV, respectively, at low temperature, but 42.9 A cm(-2) K-2 and 1.54 eV, respectively, at intermediate temperatures. It is clear that the value of the Richardson constant obtained for as-deposited and annealed samples by using double-GD for intermediate temperatures is close to the theoretical value of AlInGaN (=44.7 A cm(-2) K-2). Therefore, I-V-T characteristics for the as-deposited and annealed Schottky contacts in the temperature range of 80-320 K can be successfully explained based on TE theory with double-GD of the BHs. Published by the AVS.