Dislocation-specific dielectric mask deposition and lateral epitaxial overgrowth to reduce dislocation density of nitride films

A method for reducing dislocation density of a nitride semiconductor structure comprising an epitaxial layer, the method comprising:

• providing a substrate to a reaction chamber;
• forming a first epitaxial nitride layer on the substrate, wherein the first epitaxial nitride layer comprises lattice mismatch dislocations with the substrate;
• preferentially etching the lattice mismatch dislocations of the first epitaxial nitride layer such that etch pits are formed at the locations of the lattice mismatch dislocations to thereby prohibit threading of the lattice mismatch dislocations through the first epitaxial nitride layer;
• stopping etching of the first epitaxial nitride layer once the lattice mismatch dislocations are preferentially etched with etch pits;
• depositing dielectric over the etched nitride epitaxial layer;
• spinning a layer of blanket photoresist over the dielectric surface;
• exposing and developing the blanket photoresist to leave photoresist in the etch pits only;
• selectively etching the dielectric to leave photoresist covered dielectric masks in the etch pits;
• stripping the photoresist from the etch pits to leave dielectric masks covering the etch pits;
• and
• forming a subsequent epitaxial nitride layer over the etched epitaxial nitride layer, wherein the subsequent epitaxial nitride layer has a reducing dislocation density compared to the first epitaxial nitride layer.