Oxidation of AlGaAs layers for tapered apertures in vertical-cavity lasers

By using step-graded Al compositions of epitaxial AlGaAs, we can form a tapered oxidation front due to the combination of rapid lateral oxidation in a higher AI content layer and slow transverse oxidation into adjacent lower Al content layers. A study of the oxidation behaviour of this epitaxial aperture layer demonstrates the feasibility of tapered dielectric apertures which have been predicted to provide much lower losses in vertical cavity lasers