Surface reconstruction and surface morphology of GaN grown by MBE on GaAs (001)

Abstract

RF-plasma assisted molecular beam epitaxy growth was used to study surface reconstruction and surface morphology as a function of Ga-flux and the plasma excitation power for growth of GaN on GaAs (001) at 580°C. In the initial growth stage a (3 × 3) surface reconstruction was observed. This surface periodicity only lasted up to a maximum thickness of 2.5ML, which was followed by a new transition to the unreconstructed surface. We found that the smoothest surfaces were provided by the N/Ga-ratio giving the thickest layer at the (3 × 3) ⇒ (1 × 1) transition. The growth rate providing optimum growth conditions was shown to increase with the activation power of the RF-source, i.e. the amount of active nitrogen. Using this information, a series of samples were grown at maximum RF-source power in order to find the optimum N/Ga-flux ratio at highest possible growth rate. Characterisation by SEM indicted that the best surface morphology was obtained at a growth rate of approximately 0.3 µm/h.