Green emission from InP-GaP quantum-dot light-emitting diodes

The green electroluminescent emission from light-emitting diodes (LEDs) based on the InP-GaP quantum-dot (QD) system is investigated and discussed. The active region of the diode consists of stacked self-assembled Stranski-Krastanow indium phosphide QDs accompanied by thin quantum-well wetting layers (WLs) and embedded in a gallium phosphide matrix. LEDs based on this QD system exhibit both red and green emission. The red electroluminescence at about 720 nm originates from direct-band-gap recombination within the QDs themselves and dominates for low current. The green emission at about 550 nm appears to originate from the WL and dominates for higher current density. The marked difference in current-dependence of the green (WL) and red (QD) emission peaks enables the control of the color of the emitted light through the drive current and, thus, allows a realization of color-tunable LEDs.