Effect of photoenhanced minority carriers in metal-oxide-semiconductor capacitor studied by scanning capacitance microscopy

A scanning capacitance microscope was used to study the photoenhanced minority-carrier contribution to the capacitance of the metal-oxide-semiconductor (MOS) capacitor at high frequencies. When a light is induced over the semiconductor surface, electron-hole pairs are generated and recombined. This steady-state generation-recombination process yields the temporary source of minority carriers, and the inversion layer underneath the oxide layer can respond to very fast-varying ac bias. We measured the differential capacitance (dC/dV) of the MOS capacitor under various light intensities, and observed a peak at the inversion region where the amplitude increased as the irradiation intensity increased. By integrating dC/dV with respect to V, we obtained C-V curves in which the capacitance of the depletion region recovered its value up to that of the accumulation region as the Light intensity increased. We also observed that the C-V curves shifted in one direction under irradiation which we believe is due to the surface photovoltaic effect. (C) 2000 American Vacuum Society. [S0734-211X(00)18306-4].