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Establishing a Two Step FACELO Process in HVPE

In order to reduce the effort needed to create self-separated, freestanding gallium nitride (GaN) layers by thick growth in hydride vapor phase epitaxy (HVPE), we established a two-step facet-controlled lateral overgrowth (FACELO) process in HVPE. Just as for the metalorganic vapor phase epitaxy (MOVPE) FACELO process, the template is produced by MOVPE growth directly on sapphire. This initial GaN layer is masked with 200 nm of silicon nitride (SiNx), hexagonally structured by optical lithography. Instead of a previously used second MOVPE growth step, the masked sample is directly overgrown in HVPE to create a network of inverse pyramidal structures, before being planarized in a second growth step within the same growth run. Separation of a full 2 inch wafer could be achieved by adding a third, long growth step in HVPE which produced the necessary GaN layer thickness.