The completed High-Low method for interface state density analysis in MOS capacitors

TL;DR

This paper completes the High-Low method for MOS capacitor interface state density analysis by deriving a constraint that ensures physically consistent oxide capacitance, enabling accurate $D_{IT}$ measurement in accumulation.

Contribution

It introduces a new electrostatic constraint that completes the High-Low framework, allowing for reliable $D_{IT}$ extraction in accumulation regions.

Findings

The completed framework is validated with simulated data.

The method overcomes previous limitations in $D_{IT}$ measurement.

Frequency limitations of the technique are demonstrated.

Abstract

Interface state densities, $D_{IT}$, in metal-oxide-semiconductor (MOS) capacitors are rarely reported in the accumulation energy range. It is recognized that the determination of $D_{IT}$ in accumulation is fundamentally obscured by small inaccuracies in the user-defined oxide capacitance, $C_{OX}$. This source of error prevents the High-Low frequency technique from reporting accumulation $D_{IT}$, even for sufficiently fast high-frequency measurements. To resolve this, an electrostatic constraint that is uniquely satisfied by a physically consistent $C_{OX}$ is derived from the established theory, thereby completing the High-Low framework. The "completed" framework's theoretical validity is confirmed using simulated capacitance data for an n-SiC MOS structure, and the method's frequency limitations are demonstrated. This analytical advancement ensures a physically consistent extraction of $D_{IT}$ near the band edge, overcoming a fundamental limitation in MOS capacitor characterization.