Electrostatics of a spherical tunnel MIS structure

Abstract

Voltage distribution in a spherically symmetrical metal-insulator-semiconductor structure with a tunnel-thin insulating layer has been analyzed using the proposed analytic model and compared with that in a regular planar structure. In many electrostatic respects, the spherical system was shown to behave like a planar one with higher than specified semiconductor doping level. Special attention is paid to the reverse bias polarity. With a decrease of the insulator-semiconductor interface radius, for a fixed terminal bias, the insulator voltage becomes higher and the band bending smaller. The geometry effects are revealed for the radii below 100–200 nm, i.e., by far not in the extreme quantum limit. The elaborated model is useful for treatment of non-planar metal-insulator-semiconductor structures in the cases when the consideration of an exact topology is problematic or too speculative.