Gaussian Distribution of Inhomogeneous Barrier Height of Al/ZnS/ITO Schottky Barrier Diodes

Abstract

The current–voltage (I–V) measurements on Al/ZnS Schottky barrier diodes in the temperature range 303 –423 K by the step of 15 K were carried out. The forward I–V characteristics were analyzed on the basis of the thermionic emission theory. The temperature dependence I-V parameters such as ideality factor (n) and barrier height (ϕb0) have been explained on the basis of inhomogeneity. An abnormal increase of apparent barrier height and decrease of ideality factor with increasing temperature have been explained due to the barrier height inhomogeneities on the basis of the thermionic emission theory with Gaussian distribution. Experimental results reveal the existence of a single Gaussian distribution with apparent barrier height value (ϕb0‾) of 1.091 eV and standard deviations (σs) of 0.18 V. Richardson constant (A*) was obtained as 8.49 x 10-2 A.m-2K-2 from the ln(I0/T2) vs. q/kT plot, which is far from the calculated value of 5.6 x 105 A.m-2K-2. The modified Richardson plotof ln(I0/T2) – (q2σs2/2k2T2) gives ϕb0‾ and A* values as 1.093 eV and 6.07 x 105 A.m-2K-2, without using the temperature coefficient of the barrier height. This obtained value of A* is extremely close to the previously calculated value. So, the temperature dependence of the forward bias I-V characteristics of the Schottky device can be successfully explained on the basis of the thermionic emission mechanism with a single Gaussian distribution of the barrier heights.