Optical and frequency degradation behavior of GaN-based micro-LEDs for visible light communication.

In this study, optical power and frequency response degradation behavior of GaN-based micro-LEDs with bandwidth up to 800MHz were investigated under different modes, including direct current (DC) mode, alternating current (AC) mode and DC plus AC small signal mode at room temperature. The electroluminescence (EL), current-voltage (I-V) characteristics and small signal frequency response were measured during the stress. The results show that micro-LEDs under AC mode have better reliability because of the decreased junction temperature, but the high current density would still generate some defects within or around the active region, which can increase the trap-assisted tunneling (TAT) current and non-radiative recombination. The electrical stress-related defects not only reduce the effective carrier concentration injected into QWs but also increase the carrier lifetime for radiative recombination and Auger recombination and decrease the modulation bandwidth. These results will help to understand and improve the reliability of micro-LEDs operated under high current density and promote the application of micro-LEDs for visible light communication.