Gallium Incorporation Kinetics During GSMBE of GaN

Abstract

ABSTRACTThe kinetics of Ga incorporation during gas-source molecular beam epitaxy of GaN are investigated for varying substrate temperature and incident ammonia flux. Incident Ga atoms eventually either: 1) react with NH3 to form GaN, 2) accumulate on the film surface, or 3) desorb. Low substrate temperatures lead to significant Ga surface accumulation due to the temperature-dependent reactivity of NH3 towards Ga. High substrate temperatures give rise to significant Ga desorption. Increasing NH3 flux retards both Ga surface accumulation and Ga desorption. The GaN formation rate variation with substrate temperature peaks near 750°C and increases with NH3 flux. The observation of two distinct and very low activation energies for Ga desorption suggests a relatively complex surface chemistry and a strong likelihood that hydrogen is playing an important role.