Influence of quantum confined Stark effect and carrier localization effect on modulation bandwidth for GaN-based LEDs

We have fabricated GaN-based light-emitting diodes (LEDs) with different quantum well (QW) thicknesses to investigate the influence of the quantum confined Stark effect (QCSE) and carrier localization effect on the carrier recombination processes under both direct current (DC) and alternating current (AC) biases. At low current density, QCSE dominates the carrier recombination and decreases the radiative recombination rate. With increasing the current density, QCSE will be screened by injected carriers, and both optical power and modulation bandwidth can be increased. When the polarization field is completely compensated, the carrier localization effect starts to dominate. By reducing the influence of the QCSE and carrier localization effect, a high modulation bandwidth of ∼700 MHz was achieved at a low current density of 425 A/cm2 for the LED with 5 nm QW. Our findings will pave an alternative solution for co-optimization of the modulation bandwidth and efficiency for LEDs at a relatively low current density for visible light communications.