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

Interface state densities, DIT, in metal–oxide–semiconductor (MOS) capacitors are rarely reported in the accumulation energy range. It is recognized that the determination of DIT in accumulation is fundamentally obscured by small inaccuracies in the user-defined oxide capacitance, COX. This source of error prevents the High-Low frequency technique from reporting accumulation DIT, even for sufficiently fast high-frequency measurements. To resolve this, an electrostatic constraint that is uniquely satisfied by a physically consistent COX is derived from energy conservation principles, 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 DIT near the band edge, overcoming a fundamental limitation in MOS capacitor characterization.