Investigation of Light Extraction Efficiency and Internal Quantum Efficiency in High-Power Vertical Blue Light-Emitting Diode with 3.3 W Output Power

Light extraction efficiency (LEE) and internal quantum efficiency (IQE) of InGaN-based vertical blue light-emitting diode (LED) structures are investigated by numerical simulations and experiments. LEE of vertical LEDs is calculated for various structural and material parameters by using three-dimensional finite-difference time-domain (FDTD) simulations, and the optimum textured patterns on the n-GaN surface is found from the FDTD simulation. High-power vertical LED structures are fabricated based on the simulation results. The output power at 3 A injection current is measured to be 3.3 W, and the peak value of the external quantum efficiency (EQE) is found to be 64%. In addition, LEE of the fabricated vertical LED is expected to be 70--80% from the FDTD simulations. Combining the results of EQE and LEE, the peak IQE of the experimented vertical LED can be estimated to be 80--90%.