The growth and bonding chemistry at a gate dielectric Ga(2)O(3)/GaAs interface is investigated using in-situ photoemission techniques. A multi-chamber molecular beam epitaxy/analysis system allows for the controlled deposition of III-V and oxide layers and the probing of these layers without exposure to atmosphere. The growth of Ga(2)O(3) on a (2 x 4) reconstructed GaAs surface proceeds with molecules of Ga(2)O insertion into pairs of As-dimers with the surface void of As-O bonding. Subsequent growth involved the combination of Ga(2)O with oxygen to form Ga(2)O(3). However, for stoichiometric Ga(2)O(3), the substrate temperature >440 degrees C is required to provide the necessary energy for the reaction. This growth process is unique and represents a method for unpinning the Fermi level for GaAs with a low level of interface state density required for the fabrication of enhancement mode MOSFET devices. (C) 2010 Elsevier B.V. All rights reserved.