Measurement of Interface State Density on Pn-paterned Si Surface Using High- and Low-frequency Kelvin Probe Force Spectroscopy

We propose high-low frequency Kelvin probe force spectroscopy using high- and low-frequency AC bias voltages to measure the interface state density inside semiconductors. We derive an analytical expression for the electrostatic force between the tip and the sample that takes into account the charge transfer between the bulk and interface states in the semiconductor. We show that the electrostatic force between the tip and the semiconductor sample strongly depends on the capacitance of the charge depletion region on the surface and that the analysis of the electrostatic force at low- and high-frequency AC bias voltages can provide information on the interface state density in the semiconductor band gap. We also demonstrate using a pn-patterned silicon substrate that the interface state density can be measured.