Impact of the band–band tunneling in silicon on electrical characteristics of Al/SiO 2/p +-Si structures with the sub-3 nm oxide under positive bias

Abstract

Measurements of current–voltage and capacitance–voltage characteristics were performed for metal––tunnel oxide––silicon structures on p +-silicon wafers doped to 2×10 18–2×10 19 cm −3. Obtained results show at least two striking points. First, the forward (metal “+”) current is amazingly high and comparable in value with the reverse-bias current (metal “−”). Second, capacitance–voltage curves exhibit a distortion in the depletion regime and a hump indicating the onset of inversion. The hump is accentuated with decreasing frequency. These features are suggested to appear due to a tunneling of the valence band electrons within the forbidden gap of silicon and further into metal. Eventually, such electrons may enter the conduction band of silicon where a fraction of them can be temporarily captured at the interface and impurity defects forming thereby an inversion layer.