Optical monitoring of deposition and decomposition processes in MOCVD and MBE using reflectance anisotropy

A series of experiments have been performed in order to assess the ability of reflection anisotropy (RA) to follow the MBE growth of GaAs and AlAs on (001) GaAs, combined RA/RHEED measurements reveal a layer-by-layer growth mechanism as indicated by periodic RA oscillations. For the growth of the lattice mismatched GaAs/InAs heterostructure large RA transients are observed which are found to reach their maximum during the growth of the first monolayer and before the onset of 3D growth. RA studies have also been carried out during the MOCVD decomposition of triethylgallium (TEGa) on (001) GaAs at several temperatures ranging from 300 to 425°C. Results obtained suggest that TEGa begins to fully decompose at 350°C which is found to correlate with the formation of TEGa gas phase decomposition products. Results are also presented which may indicate a change in surface reconstruction under MOCVD conditions on moving from a Ga-rich to an As-rich surface state.