Photothermal microscopy of silicon epitaxial layer on silicon substrate with depletion region at the interface

Abstract

Photothermal microscopy has been used for investigating semiconductor materials to evaluate carrier diffusivity, lifetime, and surface recombination velocity. The effects of the depletion region between epitaxial and substrate Si with different conduction types are studied. Although the observed curves are well explained by the theoretical predictions for surface reflectivity, no drastic change is observed for the different structures. This may be due to the fact that the thickness of the epitaxial layer is too large to reveal clearly the effect of the depletion region at the PN junction. However, the result for low-frequency modulation at 10 kHz may indicate this effect.