Green InGaN Quantum Dots Breaking through Efficiency and Bandwidth Bottlenecks of Micro-LEDs

摘要

Micro-LEDs are regarded as ideal light sources for next-generation display and high-speed visible-light communication (VLC). However, the conventional micro-LEDs based on InGaN quantum well (QW) active region suffer from a low efficiency under small injection (below 1 A cm(-2)) due to the size-dependent effect and a limited 3 dB bandwidth (hundreds of MHz) due to quantum-confined Stark effect. Here, InGaN quantum dots (QDs) are proposed as the active region of micro-LEDs to address these challenges for their strong localization and low-strain features. Green InGaN QDs are self-assembled under Stranski-Krastanov (SK) and Volmer-Weber (VW) modes by using metal organic vapor phase epitaxy. The SK QDs can shift the peak efficiency of a micro-LED to an extremely low current density of 0.5 A cm(-2) (almost two orders of magnitude lower compared to QW ones) with an external quantum efficiency of 18.2% (nearly two times higher than present green micro-LEDs). Besides, green micro-LEDs based on VW QDs reach a 3 dB bandwidth of 1.3 GHz. These results indicate that InGaN QDs can provide an ultimate solution to micro-LEDs for display and VLC applications, especially since they are fully compatible with current light-emitting diode (LED) industrial technology.