Direct band gap white light emission from charge carrier diffusion induced nanowire light-emitting diodes

Light-emitting diodes (LEDs) have been investigated during the past decades, for which a major challenge is total internal reflection that limits the light extraction efficiency. 'Nanotree' LEDs elegantly solve this bottleneck. Lower band gap nanowire branches are grown on higher band gap core wires. Charge carriers diffuse into the branches and recombine there. Total internal reflection is impeded since the branch diameter is much smaller than the wavelength of light emitted from the material. Our 'nanotree' LEDs show direct band gap emission with color corresponding to the semiconductor materials composition. By stronger biasing of the core wires, we provoke white light emission without down-converting phosphors. The concept of nanoscale-enhanced charge carrier diffusion LEDs may be a game changer for industrial LED design.