Linear and nonlinear optical properties of InxGa1-xN/GaN heterostructures

We have systematically studied both the spontaneous and stimulated emission properties in blue-light-emitting InxGa1-xN/GaN multiple quantum well stru ctures using various linear and nonlinear optical techniques. Our experimen tal observations are consistently understandable in the context of localiza tion of carriers associated with, large potential fluctuations in the InxGa 1-xN active regions and at heterointerfaces. The studies have been done as a function of excitation power density, excitation photon energy, excitatio n length, and temperature. The results show carrier localization features f or spontaneous emission and demonstrate the presence of potential fluctuati ons in the InxGa1-xN active region of the InxGa1-xN/GaN structures and its predominant role in spontaneous emission. In addition, the experimental obs ervations strongly indicate that the stimulated emission has the same micro scopic origin as spontaneous emission, i.e., radiative recombination of loc alized states. Therefore, we conclude that carriers localized at potential fluctuations in InxGa1-xN active layers and interfaces can play a key role in not only spontaneous but also stimulated emission of state-of-the-art bl ue-light-emitting InxGa1-xN/GaN quantum structures.