Light-emitting diodes (LEDs) have many applications such as display backlighting, communications, medical services, signage, and general illumination. In order to minimize the cost and time consumption of development, a three-dimensional numerical simulation will be developed to examine the electrical, thermal and optical characteristics of LED chip. The experimental apparatus will be established to confirm the reliability of the numerical model.The electronic characteristic is based on the semiconductor equation system. The semiconductor part is described by the Drift-Diffusion and Poisson equations that can explain the internal device physics, such as hole and electron current density distributions, current crowding, carrier leakage, self- heating, radiative and non-radiative recombination etc. The radiative and non-radiative recombination has been used to calculate the internal quantum efficiency and heat source. In addition, this project also analyzes the effect of n-electrode size on the current density distribution not only in the active layer but also the whole entire devices by the hole and electron current density distribution. The External Quantum Efficiency (EQE) is measured using electroluminescence measurements. Finally the optimization of LEDs structure to increase Internal Quantum Efficiency (IQE) and reduce droop efficiency is the main focus of thisproject.