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 (ϕϕBo) and ideality factor (n) assuming the thermionic emission (TE) mechanism show strong temperature dependence. While n   decreases, ϕϕBo   increases with increasing temperature. Such temperature dependence of ϕϕBo is an obvious disagreement with the reported negative temperature coefficient (αtemp) of barrier height. Therefore, we have reported a modification which includes the n and electron-tunneling parameter (αχ1/2δ) in the expression of reverse-saturation current (I0). After this modification, the value of αtemp obtained as −4 × 10−4 eV/K which is very close to αtemp of GaAs band-gap (−5.4 × 10−4 eV/K). Richardson plot of the ln(I0/T2) 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 (Ea) and Richardson constant were obtained from this plot and the values of Ea 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 (ϕ¯Bo) of 1.20 and 0.68 eV and standard deviation (σs) of 0.1503 and 0.0755 V, respectively. Thus the modified ln (I0/T2)-q2σs2/2k2T2 versus q/kT for two different temperature ranges (200–400 K and 80–150 K) plot then gives mean barrier heights ϕ¯Bo and A*, 1.18 and 0.66 eV and 7.08 and 3.81 A/cm2 K2, respectively. This value of the A* 7.08 A/cm2 K2 is very close to the theoretical value of 8.16 A/cm2 K2 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.