Sapphire Substrate Liftoff With Photoelectrochemical Etching for Vertical Light-Emitting Diode Fabrication

The method of sapphire substrate liftoff for the fabrication of vertical nitride light-emitting diode (LED), based on the combination of the photoelectrochemical (PEC) etching and epitaxial lateral overgrowth (ELOG) techniques, is demonstrated. This method relies on the formation of connected voids during the ELOG process on a GaN template such that PEC electrolyte can approach the GaN portions above the SiO₂ masks. Also, the GaN template must be thin enough for the illuminating ultraviolet light to reach the GaN portions above the SiO₂ masks. It is shown that PEC etching starts from a very thin layer of GaN right above a SiO₂ mask. It then extends into the window regions of ELOG to completely separate GaN from sapphire. The performances of a vertical LED are illustrated.