Colour-tunable light-emitting diodes based on InP/GaP nanostructures

We describe a novel colour-tunable light-emitting diode whose operation is based on direct band-gap emission from coupled configurations of InP quantum dots and quantum wells embedded in GaP. The control of the emission colour stems from a marked difference in the current dependence of intensities of two different emission processes. At lower currents, the emission is dominated by the 720 nm luminescence from the quantum dots and appears red; at higher currents, the emission is dominated by the 550 nm quantum-well luminescence and the perceived colour is green. Thus, we are able to tune the colour of such diodes from red to green by means of drive current. A multi-colour pixel can be realized by a single diode, with rapid switching between colour states to provide a range of colour mix.