Multiple Shapes Micro-LEDs with Defect Free Sidewalls and Simple Liftoff and Transfer Using Selective Area Growth on Hexagonal Boron Nitride Template

Several technological challenges have prevented GaN-based micro-LEDs from finding application in mass market displays, despite their unique properties such as very high brightness and the very fast response time of GaN-based materials. The primary challenges are the cost and complexity of lift-off and transfer of LEDs from sapphire substrates to suitable supports as well as the lowered performance of tiny micro-LEDs caused by chemical etching that defines individual LEDs. Herein, this work reports demonstration of a complete process that solves these challenges with epitaxy and cleanroom technologies that are commercially available. The process begins with van der Waals epitaxy of 2D h-BN on silica masks with square, triangular and hexagonal patterns on sapphire substrates which define the micro-LED regions. Then selective area growth of MQW LED heterostructures, with ultra smooth crystalline sidewalls, down to ultra tiny size of 1.4 mu m is performed. Because of the lack of vertical chemical bonds in the h-BN layer, simple mechanical lift-off and transfer is performed on an array of LEDs heterostructures down to size of 8 mu m. Finally, transparent ITO p-contacts are deposited on LEDs with uniform lift-off, resulting in high brightness LEDs.