Surface ripples in laser-photochemical wet etching of gallium arsenide

Surface ripples of submicrometer spatial period are observed in laser enhanced etching with liquid etchants. The surface ripple formation in the laser-photochemical wet etching is not explained by the surface polariton model which needs melting of the semiconductor surface. To explain this ripple formation, we have to consider other mechanisms for ripple formation which does not need melting of the semiconductor surface, such as Raman excitation of surface polariton, polarization charge model, and bulk-selvedge coupling model. We suggest that this low power and high speed laser-photochemical etching provides a valuable one-step process for producing the fine diffraction gratings required by integrated optics.