A detailed study of current–voltage characteristics in Au/SiO 2/n-GaAs in wide temperature range

Abstract

The forward and reverse-bias current–voltage ( I– V) characteristics of Au/SiO 2/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 ( ϕ Bo ) and ideality factor ( n) assuming the thermionic emission (TE) mechanism show strong temperature dependence. While n decreases, ϕ Bo increases with increasing temperature. Such temperature dependence of ϕ Bo is an obvious disagreement with the reported negative temperature coefficient ( α temp ) of barrier height. Therefore, we have reported a modification which includes the n and electron-tunneling parameter (αχ 1/2δ) in the expression of reverse-saturation current ( I 0). After this modification, the value of α temp obtained as −4 × 10 −4 eV/K which is very close to α temp of GaAs band-gap (−5.4 × 10 −4 eV/K). Richardson plot of the ln( I 0 /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 a and Richardson constants ( A *) are much lower than the known values. These behaviors of the Au/SiO 2/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 ( σ s ) of 0.1503 and 0.0755 V, respectively. Thus the modified ln ( I 0 / T 2 ) - q 2 σ s 2 / 2 k 2 T 2 versus q/k T 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/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/SiO 2/n-GaAs (MIS) type SBDs can be successfully explained on the basis of a TE mechanism with a double-Gaussian distribution of the BHs.