Investigation of barrier inhomogeneities and interface state density in Au/MgZnO: Ga Schottky contact

Abstract

The electrical characteristics of Au/MgZnO:Ga (GMZO) Schottky contact, which is fabricated using a dual ion beam sputtering system, have been investigated using current–voltage (I–V) and capacitance–voltage (C–V) measurements over a wide temperature range of 80 to 300 K. The apparent Schottky barrier height (SBH) and ideality factor obtained from the I–V measurements are observed to increase and reduce, respectively, with increasing measurement temperature. This anomalous observation in the behaviour of the SBH is in good agreement with the predictions of a double Gaussian distribution (DGD) of the inhomogeneous SBH at a metal–semiconductor (MS) interface. The values of the SBH as determined from C–V measurements are expectedly higher than those extracted from I–V measurements. The DGD model is observed to fit with experimentally obtained data for the temperature-dependent SBH with mean values of the SBH of 0.95 and 0.54 eV and standard deviations of 0.131 and 0.072 eV in the temperature range of 160–300 K and 80–160 K, respectively. The larger value of the SBH standard deviation confirms more SBH inhomogeneity at the MS interface, and these inhomogeneities are attributed to the presence of deep level or surface level interface states. The calculated interface states density is seen to vary from 6.46 × 1014 eV−1 cm−2 at EC-0.27 eV to 1.58 × 1014 eV−1 cm−2 at EC-0.74 eV, where EC is the bottom of a conduction band at 300 K.