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

Abstract

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.