NOVELTY - The method involves growing III-nitride heterostructure (11) on a substrate (12) at a growth temperature chosen to prevent layer disordering, where heterostructure layers are doped with an impurity during growth. A dielectric capping layer (15) is deposited on a capped portion (16) of a surface of the heterostructure that provides the capped portion and an uncapped portion (17) and anneals the heterostructure at an annealing temperature and induces disordering of heterostructure layer interfaces under the uncapped portion and suppress disordering of the interfaces under the portion.    USE - Method for facilitating selective layer disordering in III-nitrides with a capping layer. Can also be used for creating a device e.g. optical waveguide, LED, photodetector, solar cell, modulator, laser and amplifier.    ADVANTAGE - The method enables annealing the heterostructure at the annealing temperature and time sufficient to induce disordering of the heterostructure layer interfaces under the uncapped portion and suppress disordering of the interfaces under the capped portion such that higher bandgap region of a laser diode is created near the output faces, thus preventing optical damage.    DETAILED DESCRIPTION - The annealing occurs in a carrier gas that is selected from a group consisting of nitrogen gas, ammonia gas, hydrogen gas and helium gas. The substrate comprises sapphire, silicon carbide, aluminum nitride, gallium nitride and alloy. The dielectric capping layer comprises silicon nitride, silicon oxynitride and silicon dioxide. The substrate includes an intervening template layer that is selected from a group consisting of aluminum nitride, gallium nitride, indium gallium nitride and aluminum gallium nitride.    DESCRIPTION OF DRAWING(S) - The drawing shows a cross-sectional view of a superlattice comprising an uncapped portion and a portion capped with a dielectric layer.    III-nitride heterostructure (11)    Substrate (12)    Dielectric capping layer (15)    Capped portion (16)    Uncapped portion (17)