REFLECTANCE-DIFFERENCE SPECTROSCOPY OF ADSORBATE-COVERED GAAS(100) SURFACES - A COMBINED SURFACE SCIENCE AND IN-SITU OMVPE STUDY

Using two experimental approaches, we have examined the role of adsorb ates during organometallic vapor phase epitaxy (OMVPE) and atomic laye r epitaxy (ALE). One set of experiments extended the RDS database to i nclude well-defined CaAs(100) reconstructions involving CHx adsorbates , whereas the other experiments examined the RD spectra over a wide ra nge of OMVPE conditions. We have found that the Type III OMVPE conditi on present at lower temperatures and higher TMGa concentration is due to a newly discovered As-rich (1 x 2)-CH3 reconstruction. The ALE cond ition following the trimethylgallium exposure cycle is due to the pres ence of a Ga-rich (1 x 4)-CH2 reconstruction. (C) 1998 Elsevier Scienc e B.V. All rights reserved.