X-ray photoelectron spectroscopy analysis of GaN/(0001)AIN and AIN/(0001)GaN growth mechanisms

The mechanisms of growth of GaN on AlN and AlN on GaN via gas source-molecular beam epitaxy with NH₃ as the nitrogen source have been investigated using x-ray photoelectron spectroscopy, low energy electron diffraction, and Auger electron spectroscopy. The growth of GaN on AlN at low temperatures (650-750°C) occurs via a Stranski-Krastanov 2D→3D type mechanism with the transition to 3D growth occurring at ≈10-15 Å. The mechanism changes to Frank van der Merwe (FM)/layer-by-layer growth above 800°C. The growth of AlN on GaN occurred via a FM layer-by-layer mechanism within the 750-900°C temperature range investigated. We propose a model based on the interaction of ammonia and atomic hydrogen with the GaN/AlN surfaces which indicates that the surface kinetics of hydrogen desorption and ammonia decomposition are the factors that determine the GaN growth mechanism.