Patent ID: 7763904

Claim:
A semiconductor structure ( 1 ) formed of nitrides of group III metals having wurtzite crystal structure and grown in vapor phase on a (0001) oriented semiconductor substrate ( 2 , 3 ), the structure comprising: a bottom cladding layer ( 4 ); a top cladding layer ( 5 ) having a flat upper surface ( 9 ) grown above the bottom cladding layer, the lattice constant of the top cladding layer being the same as that of the bottom cladding layer; and a diffusion region ( 6 , 7 ) positioned between the bottom cladding layer ( 4 ) and the top cladding layer ( 5 ) for diffusing light propagating within the semiconductor structure ( 1 ), the diffuse region having refractive index different from those of the cladding layers and non-flat surface for providing light diffusing interfaces between the diffusion region and the cladding layers, characterized in that the diffusion region comprises a plurality of diffusion layers ( 6 , 7 ), compositions and thicknesses of said diffusion layers having been chosen to avoid formation of strain-induced dislocations in the diffusion region, and adjacent diffusion layers ( 6 , 7 ) having different refractive indices in order to further enhance the diffusion efficiency.