Chemical-mechanical lift-off process for InGaN epitaxial layers

An InGaN-based light-emitting diode (LED) structure was separated from a GaN/sapphire structure by inserting sacrificial Si-doped InGaN/GaN superlattice layers through a chemical-mechanical lift-off (CMLO) process. The CMLO process consisted of a band-gap-selective photoelectrochemical lateral wet etching process and a mechanical lift-off process. A lower elastic modulus and hardness of the lateral-etched LED structure were measured compared with the conventional LED structure, which indicated a weak mechanical property of the treated LED structure. The photoluminescence blue-shift phenomenon and the Raman redshift phenomenon indicated that the compressive strain from the bottom GaN/sapphire structure was released through the CMLO process.