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.

I. Introduction

III-nitride wide bandgap semiconductor materials are promising candidates for high power and high frequency applications. Gallium nitride (GaN) and its sister materials are being continuously improving on behalf of its material as well as device quality [1], [2]. Comparative high electronic band-gap makes them suitable for high temperature applications. GaN family due to their higher polarization field coefficients and ability to form heterostructures are able to form a very thin conducting channel at the hetero-interface known as two dimensional electron or hole gas where the mobility of carriers is very high [3], [4]. Application wise GaN possess enormous potential ranging from optical to electronic and sensing applications [5]–[8].