Novel Epitaxial Nanostructures for the Improvement of InGaN LEDs Efficiency

Abstract

We demonstrated that the efficiency of an InGaN LED can be improved by using a novel epitaxial nanostructure, namely, the nanostructured semipolar (NSSP) gallium nitride (GaN). The NSSP GaN template was fabricated on a c-plane GaN surface using a standard GaN metal-organic chemical vapor deposition tool on c-plane sapphire substrates. We showed that the surface of NSSP GaN consisted of two semipolar orientations: (10-11) and (11-22). InGaN/GaN multiple quantum wells (MQWs) fabricated on NSSP GaN exhibited negligible quantum-confined Stark effect (QCSE) and a 30% improvement in internal quantum efficiency as compared to planar c-plane InGaN/GaN MQWs. Using time-resolved photoluminescence (PL), a considerable improvement in radiative recombination lifetime was also observed. We fabricated and characterized semipolar InGaN LEDs on NSSP GaN that emitted at 543 nm and showed negligible QCSE. The NSSP GaN structure can also be applied to improve the photon extraction efficiency of InGaN-based LEDs. The surface texturing was performed in situ together with the LED epitaxy without additional ex situ etching processes. The in situ surface texturing improved the PL intensity by a factor of two. An electrical injection LED structure employing in situ surface texturing was also demonstrated.