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 295–415 K. 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 B0 obtained from I-V curves, and Rs were found to be strongly temperature dependent and while B0 increases, n decreases with increasing temperature. Such behavior of B0 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 B0 versus q /2kT plot in order to obtain evidence of the GD of BHs, and the values of ̄B0=1.63 eV and 0=0.217 V for the mean barrier height and standard deviation at a zero bias, respectively, were obtained from this plot. Therefore, a modified ln I0 /T2 −q2 0 2 /2 kT 2 versus q /kT plot gives B0 and Richardson constant A* as 1.64 eV and 34.25 A/cm2 K2, respectively, without using the temperature coefficient of the barrier height. The Richardson constant value of 34.25 A/cm2 K2 is very close to the theoretical value of 33.74 A/cm2 K2 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. © 2007 American Institute of Physics. DOI: 10.1063/1.2777881