Unidirectional luminescence from InGaN/GaN quantum-well metasurfaces

III-nitride light-emitting diodes (LEDs) are the backbone of ubiquitous lighting and display applications. Imparting directional emission is an essential requirement for many LED implementations. Although optical packaging(1), nanopatterning(2,3) and surface roughening(4) techniques can enhance LED extraction, directing the emitted light requires bulky optical components. Optical metasurfaces provide precise control over transmitted and reflected waveforms, suggesting a new route for directing light emission. However, it is difficult to adapt metasurface concepts for incoherent light emission, due to the lack of a phase-locking incident wave. Here, we demonstrate a metasurface-based design of InGaN/GaN quantum-well structures that generate narrow, unidirectional transmission and emission lobes at arbitrary engineered angles. We further demonstrate 7-fold and 100-fold enhancements of total and air-coupled external quantum efficiencies, respectively. The results present a new strategy for exploiting metasurface functionality in light-emitting devices. Exploiting two-dimensional metamaterials, the direction of emission from InGaN/GaN quantum wells is engineered while simultaneously improving quantum efficiency.