The behavior of the $I‐V‐T$ characteristics of inhomogeneous $(Ni∕Au)–Al0.3Ga0.7N∕AlN∕GaN$ heterostructures at high temperatures

We investigated the behavior of the forward bias current-voltage-temperature $(I‐V‐T)$ characteristics of inhomogeneous $(Ni∕Au)–Al0.3Ga0.7N∕AlN∕GaN$ heterostructures in the temperature range of $295–415K$⁠. The experimental results show that all forward bias semilogarithmic $I‐V$ curves for the different temperatures have a nearly common cross point at a certain bias voltage, even with finite series resistance. At this cross point, the sample current is temperature independent. We also found that the values of series resistance $(Rs)$ that were obtained from Cheung’s method are strongly dependent on temperature and the values abnormally increased with increasing temperature. Moreover, the ideality factor $(n)$⁠, zero-bias barrier height $(ΦB0)$ obtained from $I‐V$ curves, and $Rs$ were found to be strongly temperature dependent and while $ΦB0$ increases, $n$ decreases with increasing temperature. Such behavior of $ΦB0$ and $n$ is attributed to Schottky barrier inhomogeneities by assuming a Gaussian distribution (GD) of the barrier heights (BHs) at the metal∕semiconductor interface. We attempted to draw a $ΦB0$ versus $q∕2kT$ plot in order to obtain evidence of the GD of BHs, and the values of $Φ¯B0=1.63eV$ and $σ0=0.217V$ for the mean barrier height and standard deviation at a zero bias, respectively, were obtained from this plot. Therefore, a modified $ln(I0∕T2)−q2σ02∕2(kT)2$ versus $q∕kT$ plot gives $ΦB0$ and Richardson constant $A*$ as $1.64eV$ and $34.25A∕cm2K2$⁠, respectively, without using the temperature coefficient of the barrier height. The Richardson constant value of $34.25A∕cm2K2$ is very close to the theoretical value of $33.74A∕cm2K2$ for undoped $Al0,3Ga0,7N$⁠. Therefore, it has been concluded that the temperature dependence of the forward $I‐V$ characteristics of the $(Ni∕Au)–Al0.3Ga0.7∕AlN∕GaN$ heterostructures can be successfully explained based on the thermionic emission mechanism with the GD of BHs.