Gaussian distribution in current-conduction mechanism of (Ni/Pt) Schottky contacts on wide bandgap AlInGaN quaternary alloy

The current-conduction mechanisms of the as-deposited and annealed at 450 °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) (ΦB 0) and ideality factor (n) of them were evaluated using thermionic emission (TE) theory. The ΦB 0 and n values calculated from the I-V characteristics show a strong temperature dependence. Such behavior of ΦB 0 and n is attributed to Schottky barrier inhomogeneities. Therefore, both the ΦB 0 vs n and ΦB 0 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 ΦB 0 and standard deviation (σ0) was calculated from the linear parts of the ΦB 0 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.