Fabrication of InP vertical facets by reactive ion etching and sidewall roughness evaluation for semiconductor microcavities

A dry etching technique is important for microfabrication of photonic devices, including semiconductor microcavities. Smooth etched sidewalls are needed to form low loss semiconductor microcavities and optical waveguides, because rough surfaces cause noticeable scattering losses. So far, scattering losses in etched reflectors or waveguides caused by interface roughness have been theoretically studied. Scattering losses should be dependent on not only the amplitude of roughness but also its correlation length; however the spatial frequency of the roughness of etched surfaces has not been discussed yet. In this paper, we present a spatial frequency analysis of the measured sidewall roughness of dry etched InP facets, and the correlation length of the sidewall roughness is estimated from the power spectrum to discuss its effect on reflectivities of the etched facet.