A Method of Measuring Differential Photovoltage Spectrum at Schottky Barrier

We report a differential photovoltage method for observing fine band-edge structure of semiconducting materials. By the use of a wavelength-modulation technique, the method provides improvement in resolution and accuracy in the determination of band-edge energies as compared to previous photovoltage measurements. The theoretical background and experimental techniques of the Schottky-barrier differential photovoltage method are described. As a result of the application to Ge and Si, it has become clear that the indirect edges can be clearly resolved with the same degree of accuracy as a highly sensitive wavelength-modulated absorption technique. In addition, we have applied this method to GaAs 1- x P x epitaxially-grown on Gesubstrate, the results showing that this method can be used as a new means of investigating the band edge of a thin semiconducting material grown on a substrate.