We extended the theory by Henry  to accurately treat the coupling of spontaneous emission noise with microcavity modes. The Green's function method is employed to solve the inhomogeneous wave equation including a Langevin force fω which accounts for spontaneous emission by carriers at angular frequency ω. The optical wave equation is coupled with the self-consistent calculations of the material spontaneous emission rate of quantum well/dot using envelope wavefunction method. Finally the carrier transport equations are solved within the framework of 2D/3D drift-diffusion model implemented in the Crosslight Software package APSYS . The simulation results of a GaN based resonant-cavity light-emitting diode (RC-LED) showed that our models can be used to predict the characteristics of RC-LED.