DETERMINATION OF THE EXCESS SURFACE ARSENIC CONCENTRATION IN THE METALORGANIC MOLECULAR-BEAM EPITAXIAL-GROWTH OF GAAS USING TMGA AND AS-2

We report an in situ dynamic method for the determination of the surfa ce concentration of adsorbed arsenic in the metalorganic molecular bea m epitaxial growth of GaAs from trimethylgallium (TMGa) and As-2. Chan ges in the reflection high electron energy diffraction intensity oscil lation period are observed under arsenic limited conditions, in which the decomposition of TMGa is strongly mediated by adsorbed arsenic. Th e period of the oscillations at the onset of growth indicates a time d ependence in which the period gradually increases from the first oscil lation to a steady state value after the growth of several monolayers. The results are interpreted as being due to an initial excess arsenic coverage which acts as a secondary source in this growth regime. (C) 1995 American Institute of Physics.