FABRICATION OF THREE-DIMENSIONAL PHOTONIC CRYSTALS IN GALLIUM ARSENIDE-BASED MATERIAL

摘要

The present invention is an efficient method for the fabrication of three-dimensional structures in GaAs-based materials. The method is particularly suitable for the realization of 3D photonic crystals. The method relies on the observation that the oxidation rate of Ga_1-xA1_xAs in water-vapor atmosphere is a strong function of the aluminum content in the alloy. Thus, a stack of Ga_1-xA1_xAs layers with varying concentration of A1 is grown on GaAs substrate. The top surface is patterned with an array of holes, which are then transferred to the underlying layers by dry etching. Subjecting the so-prepared structure to oxidation in water vapor atmosphere at an elevated temperature results in lateral oxidation of the material exposed by the etched holes. The lateral oxidation depth depends on aluminum content in a particular layer. The oxide is then removed by an aqueous solution of hydrofluoric acid and a three-dimensional array of voids ensues. The shape of the voids depends on the variation of aluminum content in the layers of the stack. Depending on the 2D pattern on top surface of the structure, various arrays of voids can be realized.