Separating InGaN membranes from GaN/sapphire templates through a crystallographic-etch-limited process

Abstract

InGaN membranes with light-emitting diode (LED) structures were separated from an undoped GaN nanorod structure on sapphire substrates through a chemical lift-off (CLO) process. The CLO processes consisted of a reducing diameter process on the GaN nanorods structure and a crystallographic wet-etching process on an N-face GaN surface. The N-face crystallographic-etching process was limited by the boundary of the GaN nanorods, where a InGaN active layer can prevent etching damage in a hot potassium hydroxide solution. The light output power of the lift-off LED membrane had a 2.28 times enhancement compared with a non-treated LED. A pyramidal-roughened structure was formed on the lift-off GaN surface to increase the light extraction efficiency. The free-standing InGaN LED membranes were realized through a crystallographic-etch-limited CLO process, which has the potential to replace the traditional laser lift-off process for vertical LEDs and be applied to flexible optoelectronic membrane applications.