Short-period gratings for long-wavelength optical devices

The reactive ion etching in InGaAsP and InP have been characterized in methane-based plasma. The role of H2, He, and Ar as diluents have been investigated. Highly anisotropic short-period gratings with periods as small as 0.2 μm and with smooth etched surfaces are presented. Auger electron spectroscopy has been used to delineate a proper processing sequence to obtain etched surfaces as clean as the surface of control samples. The CH4/He gas mixture is suggested for the fabrication of gratings as a compromise for achieving good etched profiles as well as to minimize hydrogen passivation of donors in etched samples.