Free-standing GaN layer by combination of electrochemical and photo-electrochemical etching

A free-standing GaN layer was produced by combining electrochemical (EC) etching from the front surface, photo-electrochemical (PEC) etching from the back surface, and subsequent regrowth of GaN on the porous template thus produced. The EC etching resulted in the formation of etch channels on the surface portion of the starting film, whereas the back-side PEC etching gave rise to a columnar structure supporting the entire film. When the n-GaN layer was regrown on such template, the underlying columnar structure provided weak places for easy separation and transfer of the film by mechanical bonding.