Enhanced coupling to vertical radiation is obtained from a light-emitting diode using a two-dimensional photonic crystal that lies entirely inside the upper cladding layer of an asymmetric quantum well structure. A sixfold enhancement in light extraction in the vertical direction is obtained without the photonic crystal penetrating the active material. The photonic crystal is also used to couple pump light at normal incidence into the structure, providing strong optical excitation.

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The wet oxidation of AlAs and AlGaAs has been limited to relatively small lateral dimensions and relatively thin layers. Approaches are described to extend the oxide dimensions both horizontally and vertically, creating largearea and thick buried oxides. Two types of large-area structures are examined: dielectric stacks with thin buried oxides and semiconductor-on-insulator structures with thick buried oxides. Low Al-content AlGaAs layers with low oxidation rates are used as the high-index layers in large-area dielectric-stack structures. High Al-content AlGaAs layers with low volume contraction are used to create stable, thick buried oxides with millimeter-scale areas.

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