A detailed study of current-voltage characteristics in Au/SiO2/n-GaAs in wide temperature range

The forward and reverse-bias current-voltage (I-V) characteristics of Au/SiO2/n-GaAs (MIS) type Schottky barrier diode (SBDs) have been investigated in the wide temperature range of 80-400 K. The zero-bias barrier height (phi(Bo)) and ideality factor (n) assuming the thermionic emission (TE) mechanism show strong temperature dependence. While n decreases. OB, increases with increasing temperature. Such temperature dependence of phi(Bo) is an obvious disagreement with the reported negative temperature coefficient (alpha(temp)) of barrier height. Therefore, we have reported a modification which includes the n and electron-tunneling parameter (alpha chi(1/2)delta) in the expression of reverse-saturation current (I-o). After this modification, the value of at,,p obtained as -4 x 10(-4) eV/K which is very close to alpha(temp) of GaAs bandgap (-5.4 x 10(-4) eV/K). Richardson plot of the In(I-o/T-2) versus 1/T has two linear region; the first region is (200-400 K) and the second region (80-150 K). The values of the activation energy (E-a) and Richardson constant were obtained from this plot and the values of E alpha and Richardson constants (A*) are much lower than the known values. These behaviors of the Au/SiO2/n-GaAs (MIS) type (SBDs) have been interpreted by the assumption of a double-Gaussian distribution of barrier heights (BHs) at the metal-semiconductor interface giving a mean BHs ((phi) over bar (Bo)) of 1.20 and 0.68 eV and standard deviation (sigma(s)) of 0.1503 and 0.0755 V, respectively. Thus the modified In (I-o/T-2) - q(2)sigma(2)(s)/2k(2)T(2) versus q/kT for two different temperature ranges (200-400 K and 80-150 K) plot then gives mean barrier heights (phi) over bar (Bo) and A*, 1.18 and 0.66 eV and 7.08 and 3.81 A/cm(2) K-2, respectively. This value of the A* 7.08 A/cm(2) K-2 is very close to the theoretical value of 8.16 A/cm(2) K-2 for n-type GaAs. Hence, all these behaviours of the forward-bias I-V characteristics of the Au/SiO2/n-GaAs (MIS) type SBDs can be successfully explained on the basis of a TE mechanism with a double-Gaussian distribution of the BHs. (C) 2009 Elsevier Ltd. All rights reserved.