Reduction of etched AlGaAs sidewall roughness by oxygen-enhanced wet thermal oxidation

The authors demonstrate that the oxidation smoothing of sidewall roughness of dry-etched Al0.3Ga0.7As ridge structures is enabled through a modified wet thermal oxidation process which involves the addition of dilute amounts of O-2 to the water vapor ambient. High magnification cross-section and top-view scanning electron microscope imagings both before and after oxide removal clearly show a substantial reduction of photolithography- and dry-etching-induced sidewall roughness (from sigma similar to 100 nm down to sigma similar to 1-2 nm), occurring only with the participation of added O-2. The smoothing process provides means to realize high-index-contrast GaAs-based optical waveguides with both low bend and scattering losses. (c) 2007 American Institute of Physics.