Various Shaped Semiconductor Microlens Arrays Fabricated by Selective Oxidation of AlGaAs

Semiconductor microlens arrays with circular, cylindrical, square, and ring-type bases were fabricated by using selective oxidation of chirped short-period superlattice of GaAs-AlGaAs. Confocal microscopy and atomic force microscopy were used to evaluate the surface morphology of the fabricated microlenses, which revealed that they have cross-sectional profiles close to spherical in shape and an root-mean-square surface roughness of less than 10 nm for the scanned area of 5 mum times 5 mum. The optical parameters of the microlenses, evaluated by measuring the focused spot pattern and focal length, revealed strong focusing function of the microlenses that were very close to the calculated values, indicating high structural and optical quality of the fabricated microlenses.