Distributed Bragg reflectors may be formed in fewer layers by the method, which is capable of producing greater differences in indexes of refraction. Group III-V alternating layers are deposited. The microstructure of alternating layers is controlled to be different. A combination of alternating polycrystalline layers or amorphous and polycrystalline layers results. Alternate ones of the layers oxidize more quickly than the others. A lateral wet oxidation of the alternate ones of the layers produces a structure with large differences in indexes of refraction between adjacent layers. The microstructure between alternating layers may be controlled by controlling Group V overpressure alone or in combination with growth temperature.