Enhancement of Light Extraction Through the Wave-Guiding Effect of ZnO Sub-microrods in InGaN Blue Light-Emitting Diodes

The improvement of the light extraction efficiency (LEE) of a conventional InGaN blue light‐emitting diode (LED) by the incorporation of one‐dimensional ZnO sub‐microrods is reported. The LEE is improved by 31% through the wave‐guiding effect of ZnO sub‐microrods compared to LEDs without the sub‐microrods. Different types of ZnO microrods/sub‐microrods are produced using a simple non‐catalytic wet chemical growth method at a low temperature (90 °C) on an indium‐tin‐oxide (ITO) top contact layer with no seed layer. The crystal morphologies of needle‐like or flat‐top hexagonal structures, and the ZnO microrods/sub‐microrod density and size are easily modified by controlling the pH value and growth time. The wave‐guiding phenomenon within the ZnO rods is observed using confocal scanning electroluminescence microscopy and micro‐electroluminescence spectra. 1D ZnO rod structures as an optical wave‐guiding medium are proposed as a means of improving the light extraction efficiency of InGaN/GaN multiple quantum well blue LEDs. Different shapes of ZnO rod structures are produced using a simple non‐catalytic wet‐chemical growth method at low temperature on an ITO contact layer. Confocal scanning electroluminescence microscopy and micro‐electroluminescence spectra confirmed the wave‐guiding phenomenon within the ZnO sub‐microrods.