Probing the surface potential of oxidized silicon by assessing terahertz emission

Abstract

Using laser terahertz emission microscopy, we measured laser-excited terahertz (THz) emission from silicon wafers with silicon-oxide passivation layers, revealing a strong correlation between the THz waveform and the surface potential. The surface potential was electrically tuned by a semitransparent top electrode disc and evaluated by measuring capacitance–voltage characteristics. The waveform changed with external bias and inverted near the flatband voltage, and changes appeared in the peak amplitude were similar to the capacitance–voltage characteristics. These results indicate that by analyzing the waveform of laser-excited THz emission generated by laser terahertz emission microscopy, we could quantitatively measure and map the internal field of surface band bending in semiconductors.