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

The temperature dependent electrical characteristics of Se/n-GaN Schottky barrier diode have been investigated in the temperature range of 130-400 K in the steps of 30 K. The estimated barrier height (_bo) and ideality factor n are found to be 0.46 eV and 3.83 at 130 K, 0.92 eV and 1.29 at 400 K. The _bo and n are found to be strongly temperature dependent and while the _bo decreases and the n increase with decreasing temperature. Such behavior of _bo 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 0.90 eV and standard deviations (σ_o) of 0.0289 and 0.010 V, respectively. The modified ln(I_o/T²) - (q²σo2/2k²T²) versus 10³/T plot gives _bo and Richardson constant (A^{â̂ -}) values as 1.30 and 0.88 eV, 23.6 and 19.2 A/cm² K² at 400 and 130 K, 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 (N_ss) 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.