Optimization of InGaN/GaN superlattice structures for high-efficiency vertical blue light-emitting diodes

We investigate carrier distribution and efficiency characteristics of GaN-based vertical blue light-emitting diodes (LEDs) having InGaN/GaN short-period superlattice (SL) structures by using numerical simulations. The SL structures exist between multiple-quantum-well active layers and an n-GaN layer. The In composition and doping concentration of SL layers are found to have strong influence on the electron concentration distribution in the plane of QWs, internal quantum efficiency, and forward voltage of vertical LEDs. The electron distribution becomes homogenous as the In composition increases or doping concentration decreases, which results in the reduction of efficiency droop and the increase of forward voltage. Based on the simulation results, optimum SL structures for obtaining the maximum wall-plug efficiency are found.