Scanning impedance microscopy of an active Schottky barrier diode

Abstract

Electrostatic force sensitive scanning probe microscopy is used to quantify dc and ac transport properties of an active Schottky barrier diode. Scanning surface potential microscopy (SSPM) of the laterally biased device is used to quantify the potential drop at the metal–semiconductor interface. Ramping the lateral bias allows the local voltage and I–V characteristics of the diode to be reconstructed. Scanning impedance microscopy (SIM) demonstrates the phase and amplitude change of voltage oscillations across the interface. The frequency dependence of voltage phase shifts across the interface defines the appropriate equivalent circuit for the reverse biased junction. Excellent agreement between junction capacitance obtained from SIM measurements and impedance spectroscopy is demonstrated. Variation of the dc component of lateral bias in SIM yields the local capacitance–voltage characteristics of the junction. SIM contrast of grain boundaries in p-doped silicon was interpreted in terms of minority carrier generation in the interface region. The combination of SSPM and SIM provides an approach for the quantitative analysis of local dc and ac transport properties which were demonstrated for a Schottky diode but can be applied to any semiconductor device.