Barrier-layer-thickness control of selective wet oxidation of AlGaAs for embedded optical elements

Selective wet oxidation of AlGaAs layers can be used to form embedded optical elements, such as buried lenses and current control apertures in vertical cavity structures. Oxidation rates of buried Al0.94Ga0.06As layers were controlled by varying the thickness of GaAs barrier layers between layers of Al0.94Ga0.06As and Al0.98Ga0.02As. This phenomenon can be attributed to the superposition of a vertical oxidation component due to species diffusing through the barrier layer and a constant lateral oxidation component. The magnitude of the vertical component is controlled by the GaAs barrier thickness, which determines the concentration of additional oxidizing species in the Al0.94Ga0.06As layer.