Patent ID: 8183124

Claim:
A method of making a semi-insulating epitaxial layer, comprising: applying a mask material on a surface of a first epitaxial layer, wherein the first epitaxial layer is on a substrate; forming trenches in the first epitaxial layer; implanting the first epitaxial layer with boron ions to form a boron implanted region on a surface of the first epitaxial layer, wherein implanting the first epitaxial layer comprises implanting the first epitaxial layer after forming the trenches in the first epitaxial layer to form a boron implanted region in the trenches; and growing a second epitaxial layer on the boron implanted region of the first epitaxial layer to form a semi-insulating epitaxial layer; wherein boron in the boron implanted region diffuses into the second epitaxial layer grown on the boron implanted region to form the semi-insulating epitaxial layer.