Patent ID: 7893463

Claim:
An integrated pair of HBT and FET transistors sharing a common compound semiconductor III-V epitaxial layer, the integrated pair of transistors comprising: a semi-insulating substrate of a compound semiconductor III-V material; a first epitaxial structure disposed on top of the substrate, the first epitaxial structure forming a portion of the FET transistor; a second epitaxial structure on top of the first epitaxial structure, the second epitaxial structure serving as the shared common compound semiconductor III-V epitaxial layer; a third epitaxial structure disposed on top of the second epitaxial structure, the third epitaxial structure forming a portion of the HBT transistor; and an interface between the semi-insulating substrate and the first epitaxial structure wherein a concentration profile of a first contaminant across the interface decreases substantially smoothly, wherein the first contaminant contributes electrical charge.