Nonpolar and Semipolar GaN-Based Core-Shell Nanostructure LEDs on c-Plane Sapphire Using Selective-Area MOCVD

The lower polarization-related electric fields in GaN-based planar nonpolar and semipolar optoelectronic devices result in enhanced optical characteristics like higher radiative efficiencies and lower efficiency droop. This is attributed to the improved electron-hole spatial overlap due to a significant reduction in the magnitude of the internal electric fields at heterojunction interfaces. However, the high cost associated with free standing nonpolar and semipolar GaN substrates presents a significant bottleneck towards the commercialization of these optoelectronic devices. Alternately, nanostructures grown by selective-area (SA) epitaxy exhibit equilibrium nonpolar (10-10) and semipolar (10-11) facets and can potentially be engineered on low-cost conventional c-plane sapphire substrates to fabricate high-performance LEDs.  In this work, we demonstrate electrically injected nanowall LEDs, either exhibiting primarily (10-10) orientations, or triangular nanostripe core-shell semipolar GaN-based LEDs (TLEDs) exhibiting (10-11) orientations, fabricated using interferometric lithography and catalyst-free bottom-up SA metal organic chemical vapor deposition (MOCVD).