The Temperature-Dependent Interface States and the Reverse Current Conduction Mechanism of Single-Crystal ZnO Schottky Diodes

The various current conduction mechanisms of Ag/ZnO Schottky diodes were explored by measuring the current–voltage characteristics from 100 to 300 K. In terms of thermionic emission, a comparison of the Schottky barrier height (SBH) to the ideality factor revealed two linear regions within 100–160 K and 200–300 K. Thus, the forward current characteristics feature two SBH sets with Gaussian distributions. The experimental ideality factor was approximated using the tunneling-related characteristic energy (E₀₀) (31 meV). Locally enhanced electric fields were associated with local low-barrier regions that enhanced the tunneling probability. The reverse current characteristics revealed that Poole–Frenkel (not Schottky) emission predominated, attributable to Zn_i-associated defects. Localized electric fields affected both the forward and reverse current characteristics and enhanced the internal electric field about five-fold.