Confocal electroluminescence investigations of highly efficient green InGaN LED via ZnO nanorods

The light emission mechanism of green InGaN-based light-emitting diodes (LEDs) coated with ZnO nanorods (ZnO-nanorods/InGaN LEDs) was investigated by confocal scanning electroluminescence (EL) spectroscopy (CSEM). The ZnO nanorods were grown by a hydrothermal method on the surface of fully fabricated InGaN LEDs. The vertical alignment and high crystallinity of the ZnO nanorods were confirmed by scanning electron microscopy, X-ray diffraction, photoluminescence spectroscopy, micro-Raman spectroscopy, and high-resolution transmission electron microscopy. Measurement of the light output as a function of the injection current, far-field radiation pattern, and current versus voltage curves revealed that the light output power of the green InGaN LEDs with ZnO nanorods was enhanced by approximately 60% compared to that of conventional green InGaN LEDs without ZnO nanorods. However, the electrical properties of the ZnO-nanorods-coated device were not appreciably affected by the nanorods. To analyse the light emission mechanism of the ZnO-nanorods/InGaN LEDs, CSEM was used to observe the EL intensity distributions at different focal planes.