Ultraviolet, blue, and green InGaN-based light-emitting diodes functionalized with ZnO nanorods

We investigated the augmentation in the light-output power of InGaN light-emitting diodes (LEDs) functionalized with ZnO nanorods (NRs) according to the emission wavelength of the LEDs and the volume fraction of the ZnO NRs. The ZnO NRs were fabricated on top of the ultraviolet, blue, and green InGaN LEDs using the hydrothermal method. The optical properties of the LEDs and ZnO NRs were examined by electroluminescence, photoluminescence, and Raman scattering at room temperature. The measurements of light-output power versus current and current as a function of voltage showed that there were considerably different enhancements in the light-output power of InGaN LEDs functionalized with ZnO NRs at different emission wavelengths of the LEDs, while no changes were observed in the electrical properties. Three-dimensional finite-difference time-domain simulations were conducted to support the experimental results. Both experimental and theoretical results indicated that the light-extraction efficiency of InGaN LEDs functionalized with ZnO NRs was significantly affected by the differences between the refractive indices of the GaN layers, indium-tin oxide layer, and ZnO NRs, which could be changed by the emission wavelength of the LEDs and volume fraction of the ZnO NRs.