The distribution of barrier heights in MIS type Schottky diodes from current–voltage–temperature ( I– V– T) measurements

Abstract

The forward bias current–voltage–temperature ( I– V– T) characteristics of the Au/SiO 2/n-Si (MIS) type Schottky diodes (SDs) have been investigated in the temperature range of 300–400 K. The estimated zero-bias barrier height ( Φ B0) and the ideality factor ( n) assuming thermionic emission (TE) theory show strong temperature dependence. An abnormal decrease in the Φ B0 and an increase in the n with decreasing temperature have been explained on the basis of the TE theory with a Gaussian distribution (GD) of the barrier heights (BHs) due to BH inhomogeneities. The conventional Richardson plot should be a straight line especially at intermediate temperatures ( T ≤ 325). The values of activation energy ( E a) and Richardson constant ( A *) were determined as 0.167 eV and 1.385 × 10 −6 A cm −2 K −2 from the slope and the intercept at ordinate of the linear region of this plot, respectively. Also, we attempted to draw a Φ B0 versus q/2 kT plot in order to obtain evidence of the GD of BHs, and the values of Φ ¯ B0 = 1.301 eV and σ s = 0.187 V for the mean barrier height and zero-bias standard deviation have been obtained from this plot, respectively; then, a modified ln ( I 0 / T 2 ) − q 2 σ s 2 / 2 k 2 T 2 versus q/ kT plot gives Φ ¯ B0 and A * as 1.298 eV and 109.481 A cm −2 K −2, respectively. This value of the A * (=109.481 A cm −2 K −2) is very close to the theoretical value of 112 A cm −2 K −2 for n-type Si. Therefore, it has been concluded that the temperature dependence of the forward bias I– V characteristics of the MIS type Schottky diodes can be successfully explained on the basis of TE mechanism with a GD of the BHs.