Multi-color light-emitting diodes based on GaN microstructures

Monolithic multi-color light-emitting diodes (LEDs) based on micro-structured InGaN/GaN quantum wells are demonstrated. The microstructure is created through regrowth on SiO2 mask stripes along the [1 (1) over bar 00] direction and consists of (0001) and {11 (2) over bar2} facets. The LEDs exhibit polychromatic emission, including white, due to the additive color mixture of facet-dependent emission colors. Altering the growth conditions and mask geometry easily controls the apparent emission color. Simulations predict high light extraction efficiencies due to their three-dimensional structures. Furthermore, we demonstrate that the apparent emission colors can externally be controlled over a wide spectral range that encompasses green to blue or white at a color temperature of 4000 K to blue along the Planckian locus. The controllability relies on the facet-dependent polychromatic emissions; the pulsed current operation with the appropriate duties varies their relative intensities and the consequent apparent colors without seriously affecting the total number of emitted photons, particularly for the blue to green variation. The proposed LEDs can be fabricated through a simple process and, therefore, may be a key device for advanced solid-state lighting.