Optical properties of InGaN layers

Optical absorption spectroscopy provides important properties of a material including fundamental absorption edge and defect structures. We use it to investigate the band gap of In$_{x}$Ga$_{(1-x)}$N with different Gallium contents grown by HPCVD. The results have shown that a bowing parameter of b = 2.5 eV allows one to reconcile our results and the literature data for the band gap of In$_{x}$Ga$_{(1-x)}$N alloys over the whole composition range. In addition, we calculate the thicknesses of the In$_{x}$Ga$_{(1-x)}$N thin films through simulation of the transmission using a multilayer stack model. The free electron concentration in the In$_{x}$Ga$_{(1-x)}$N thin film determined here is also found to be in good agreement with that obtained from simulations of infrared reflection measurements we carried out.