Monolithic high performance InGaN/GaN white LEDs with a tunnel junction cascaded yellow and blue light-emitting structures

Abstract

We propose a phosphor-free dual wavelength monolithic white LED comprising a tunnel junction that separates a yellow light-emitting InGaN/GaN multiple quantum well (MQW) structure without an electron blocking layer (EBL) from a blue light-emitting MQW structure. Using a well-calibrated APSYS simulation software we investigate its performance in terms of output power, wall plug efficiency, and CIE plot of the emitted light and analyze its operation on the basis of band diagram, carrier distribution, EL spectra and radiative recombination rate taking into account the carrier confinement and carrier reuse effects due to removal of an EBL and incorporation of a tunnel junction, respectively. At the injection current density of 250 A/cm2, our proposed white LED exhibits 232% improvement in output power as compared to a conventional blue LED and only 40% droop reduction of wall plug efficiency as opposed to 56% in a reported white LED. The Commission Internationale de l'Eclairage (CIE) coordinates of the emitted light from the proposed white LED structure are found to be (0.310, 0.309) at 100 A/cm2 which signify a good quality white light emission.