In accordance with the present invention, improved methods for reducing
the dislocation density of nitride epitaxial films are provided.
Specifically, an in-situ etch treatment is provided to preferentially
etch the dislocations of the nitride epitaxial layer to prevent threading
of the dislocations through the nitride epitaxial layer. Subsequent to
etching of the dislocations, an epitaxial layer overgrowth is performed.
In certain embodiments, the etching of the dislocations occurs
simultaneously with growth of the epitaxial layer. In other embodiments,
a dielectric mask is deposited within the etch pits formed at the
dislocations prior to the epitaxial layer overgrowth.