Polychromatic white LED using GaN nano pyramid structure

Abstract

We have developed monolithic white light emitting diodes (LEDs) with a hybrid structure of planar c-planes and nano size hexagonal pyramids. The white spectrum is composed of blue and yellow emissions from the InGaN multi quantum wells (MQWs) on the planar c-planes and on the nano pyramids, respectively. The yellow emission is originated from quantum wells, wires, and dots that are formed at the sides, edges, and tops of the nano-pyramids, respectively. As a result, the emission peaks are different and the entire yellow spectrum is broad enough to make a white in combination with a blue emission. The longer wavelength from the InGaN on nano-pyramids than the wavelength from the InGaN on c-planes is explained by excess In supply from the dielectric selective growth mask. The color temperature is tuned from 3600K to 6400K by controlling the relative area ratio of c-plane and nano-pyramids.