Effects of Ta-oxide interlayer on the Schottky barrier parameters of Ni/n-type Ge Schottky barrier diode

The effect of Ta-oxide interlayer on the Schottky barrier parameters of Ni/n-type Ge Schottky barrier diode (SBD) was investigated. The introduction of the Ta-oxide interlayer in-between Ni film and Ge substrate resulted in an increase in the barrier height as against the conventional Ni/n-type Ge SBD. Furthermore, increase in the thickness of the Ta-oxide interlayer led to the increase in barrier height and decrease in ideality factor, which could be associated with the improvement of interface quality of Schottky junction. 5 nm-thick Ta-oxide interlayer was more stoichiometric than 3 nm-thick Ta-oxide one, which was effective in the reduction of interface state density and ideality factor. An investigation of the electric field dependence of the reverse current in the Ni/n-type Ge SBDs with and without Ta-oxide revealed that the Poole-Frenkel emission mechanism dominates the current conduction of both devices in the reverse bias region.