X-ray photoelectron spectroscopy analysis of GaN/(0001)AlN and AlN/(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 degrees C) occurs via a Stranski-Krastanov 2D --> 3D type mechanism with the transition to 3D growth occurring at approximate to 10-15 Angstrom. The mechanism changes to Frank van der Merwe (FM)/layer-by-layer growth above 800 degrees C. The growth of AlN on GaN occurred via a FM layer-by-layer mechanism within the 750-900 degrees 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. (C) 1999 American Institute of Physics. [S0021-8979(99)08521-7].