Electrical properties and the double Gaussian distribution of inhomogeneous barrier heights in Se/n-GaN Schottky barrier diode

Abstract

The temperature dependent electrical characteristics of Se/n-GaN Schottky barrier diode have been investigated in the temperature range of 130–400K in the steps of 30K. The estimated barrier height (ϕbo) and ideality factor n are found to be 0.46eV and 3.83 at 130K, 0.92eV and 1.29 at 400K. The ϕbo and n are found to be strongly temperature dependent and while the ϕbo decreases and the n increase with decreasing temperature. Such behavior of ϕbo and n is attributed to Schottky barrier inhomogeneities, explained by the assumption of Gaussian distribution of barrier heights at the metal/semiconductor interface. Experimental results revealed the existence of a double Gaussian distribution with mean barrier height values of 1.33 and 0.90eV and standard deviations (σo) of 0.0289 and 0.010V, respectively. The modified ln(Io/T2)−(q2σo2/2k2T2) versus 103/T plot gives ϕbo and Richardson constant (A∗) values as 1.30 and 0.88eV, 23.6 and 19.2 A/cm2 K2 at 400 and 130K, respectively without using the temperature coefficient of the barrier height. Further, the barrier height obtained from C–V method decreases with an increase in temperature. It is also noted that the barrier height value estimated from the C–V method is higher than that estimated from the I–V method at various temperatures. Possible explanations for this discrepancy are presented. The interface state density (Nss) is found to be decreased with an increasing temperature. The reverse-bias leakage current mechanism of Se/n-GaN Schottky diode is investigated. Both Poole–Frenkel and Schottky emissions are described and discussed.