Incorporation of Ga metalorganic precursors during transients at the startof GaAs growth in CBE

We have used normal incidence reflectivity and reflection anisotropy spectr oscopy (RAS) to study the initial period of chemical beam epitaxy (CBE) gro wth of GaAs using either triethylgallium (TEGa) or trimethylgallium (TMGa) as group III precursors. With TEGa as the precursor, a transitory period, w hich can last for tens of seconds depending on the III/V ratio, is observed in both R and RAS before normal growth is established. With TMGa there is no transitory period evident in the R measurements for any III/V ratio and only a short transitory period exists in the RA measurements. These results are discussed in terms of the formation of a metallic-like surface addlaye r, which subsequently becomes incorporated when using TEGa, in marked contr ast to the self-limiting behaviour when using TMGa. (C) Published by Elsevi er Science S.A. All rights reserved.