GaN Quantum-Dot Formation by a Temperature Increase in an Ammonia Flow

Abstract—: The transformation of a two-dimensional GaN layer into three-dimensional islands (2D–3D transition) under increasing temperature in a flow of ammonia is investigated experimentally by reflection high-energy electron diffraction (RHEED). The results are explained in the framework of the previously developed kinetic model and the Mariette equilibrium model. It is shown that the surface energy increases with increasing temperature due to the desorption processes of NH particles, the 3D surface state becomes energetically favorable, and 3D islands are formed. With a further increase in temperature, the surface energy decreases due to the dissociation processes of NH and NH particles, and the 2D surface state becomes energetically favorable again resulting in the 3D islands transforming back to a 2D layer.