Efficient performance enhancement of GaN-based vertical light-emitting diodes coated with N-doped graphene quantum dots

摘要

Novel vertical light-emitting diodes (VLEDs) decorated with N-doped graphene quantum dots (N-GQDs) have been fabricated, based on the metal organic chemical vapor deposition method (MOCVD), wafer bonding technique, laser lift-off (LLO) technique, inductively coupled plasma (ICP) etching and impregnation processing. There is an obvious luminescence enhancement and resistance reduction for VLEDs after coating N-GQDs. The results show an improvement of light output power (LOP), dependent on the improvement of optical extraction efficiency and current spreading. The improvement of external quantum efficiency (EQE) is mainly owing to the roughened surfaces. Meanwhile, an enhancement of electroluminescence (EL) intensity and photoluminescence (PL) intensity has been achieved when the VLEDs were immersed in 0.9 mg/mL of N-GQDs solution, 4 times that of bare VLEDs. After coating N-GQDs, the performance of VLEDs is greatly improved, which could be attributed to the photons recovered by extracting light from waveguide modes.