High-efficiency InGaN -based light-emitting diodes with nanoporous GaN:Mg structure

In this research nanoporous structures on p -type GaN:Mg and n -type GaN:Si surfaces were fabricated through a photoelectrochemical (PEC) oxidation and an oxide-removing process. The photoluminescence (PL) intensities of GaN and InGaNGaN multi-quantum-well (MQW) structures were enhanced by forming this nanoporous structure to increase light extraction efficiency. The PL emission peaks of an MQW active layer have a blueshift phenomenon from 465.5 nm (standard) to 456.0 nm (nanoporous) measured at 300 K which was caused by partially releasing the compressive strain from the top GaN:Mg layers. The internal quantum efficiency could be increased by a partial strain release that induces a lower piezoelectric field in the active layer. The thermal activation energy of a nanoporous structure (85 meV) is higher than the standard one (33 meV) from a temperature dependent PL measurement. The internal quantum efficiency and light extraction efficiency of an InGaNGaN MQW active layer are significantly enhanced by this nanoporous GaN:Mg surface, and this PEC treated nanoporous structure is suitable for high-power lighting applications.