  Longer wavelength emitters such as green LEDs display a pronounced efficiency
drop at higher current densities, resulting in relatively low wall-plug
efficiency. Multi-active region approach can improve the wall-plug efficiency
significantly and tackle the green gap challenge. This work reports
multi-active region p-down LEDs with high external efficiency operating
entirely in the green wavelength. Devices were developed using p-down topology,
where the PN junction is oriented such that electric fields from depletion and
built-in polarization dipoles are aligned. Ga-polar multi-active region green
LEDs with excellent voltage and EQE scaling, and significantly higher wall-plug
efficiency is demonstrated in this work.
