+SMALL +STRUCTURED +EFFICIENT
In recent years, phosphor-free III-nitride nanowire light-emitting diodes (LEDs) have been intensively studied as a promising candidate for future solid-state lighting and full-color display applications. Compared with the conventional quantum well based LEDs, nanowire devices offer several potential advantages, including drastically reduced dislocations and polarization fields, flexible emission wavelength tenability and negligible efficiency droop at high injection current. To date, however, such nanowire devices generally exhibit very low output power.
Professor Mi and his team have shown that the underlying cause for the low output power of nanowire LEDs is directly related to the poor carrier injection efficiency, due to the surface recombination. His team further developed phosphor-free InGaN/GaN/AlGaN dot-in-a-wire core-shell white LEDs grown by molecular beam epitaxy on Si substrate, which can break the carrier injection efficiency bottleneck, leading to a massive enhancement in the output power. At room-temperature, the devices can exhibit an output power of ∼1.5 mW, which is more than 2 orders of magnitude stronger than nanowire LEDs without shell coverage. Additionally, such phosphor-free nanowire white LEDs can deliver an unprecedentedly high color rendering index of ∼92−98 in both the warm and cool white regions, with the color rendering capability approaching that of an ideal light source, i.e. a blackbody.
 Hieu Pham Trung Nguyen , Shaofei Zhang , Ashfiqua T. Connie , Md Golam Kibria , Qi Wang , Ishiang Shih , and Zetian Mi, Nano Letter, 13 (11), 5437-5442 (2013)
Prof. Zetian Mi (McGill University)