Effect of In-homogeneities on Schottky barrier height & Richardson constant of Ni-AlGaN/GaN Schottky contact

In this article, we present the variation in schottky barrier height (SBH) and ideality factor of Ni schottky contact (area $1.0\times 10^{-4}\ \ \text{cm}^{2}$) on AlGaN/GaN epitaxial layer with temperature (77 K to 350 K). The spread of SBH and ideality factor is in the range of 0.32 eV-1.05 eV and 7.16-1.48 respectively. The dependence of SBH and ideality factor points to the presence of in-homogeneities at Ni/AlGaN interface. Presence of these in-homogeneities at the metal/semiconductor interface leads to an inaccurate value of Richardson constant extracted using Richardson's plot. A Gaussian distribution of in-homogeneities at the interface is considered and included further in the standard schottky diode equation to obtain a modified Richardson's plot in order to extract a more precise value of Richardson constant for AlGaN epitaxial layer. The Schottky barrier height and Richardson constant obtained considering Gaussian distribution is 1.01 eV and 33.4 Acm−2K−2 respectively. Moreover the variation of diode series resistance with temperature is also determined using Cheung's method which is found to be increasing linearly with temperature.