Emission Mechanism of Mixed-Color InGaN/GaN Multi-Quantum-Well Light-Emitting Diodes

Abstract

In this study, GaN-based light-emitting diodes (LEDs) were designed with a multi-quantum-well active region, including a yellow-green and a blue quantum well in each period. Photoluminescence (PL) and electroluminescence (EL) measurements revealed two emission bands (at λ∼450 and 560 nm) originating from the two well regions. The ratio of blue to yellow-green emission intensities changes with the excitation intensity. In EL, the intensity of the blue emission peak exceeds that of the yellow-green emission peak when a low DC current (I≦40 mA) is applied. However, when a high pulsed current is applied (I≧100 mA) to the LEDs, the intensity of the yellow-green band exceeds that of the blue band, because of the competition between carrier tunneling and band-to-band recombination.