Measurement of semiconductor local carrier concentration from displacementcurrent-voltage curves with a scanning vibrating probe

A theoretical equation has been fitted to displacement current-voltage curv es of semiconductor in order to obtain the local carrier concentration of t he semiconductor. The distance between a semiconductor surface and a scanni ng probe is changed sinusoidally and is adjusted as small as a few nm at wh ich tunneling current flows. Displacement current due to the change in elec tric flux from the semiconductor surface to the scanning probe flows period ically in accordance with the vibration of the scanning probe, and it is se parated from tunneling current using a two-phase lock-in amplifier. The dis placement current-probe voltage curve is analyzed by taking into account tw o-dimensional electric flux profile from the semiconductor surface. It is r ealized that the lateral resolution of the displacement current depends on the probe voltage and that it is between one-eighth and one-fifteenth small er than the top radius of the probe since the depletion-layer width of the semiconductor is determined by the probe voltage, the distance, and the car rier concentration. The theoretical displacement current-voltage curves are in good agreement with the measurement in both voltage regions where the m ajority carriers are accumulated and depleted. The local carrier concentrat ion can be determined by fitting the theoretical displacement current-volta ge curve with the experimental results.