OBSERVATION OF LOW-T GAAS GROWTH REGIMES BY REAL-TIME ELLIPSOMETRY

The molecular beam epitaxial growth of low temperature (LT) GaAs films has been studied by real-time ellipsometry. A modification in a GaAs( 001) surface by cooling under a specific As-2 flux caused a change in the ellipsometry data. The thermocouple reading of this change was use d as a signature to indicate the reproducible substrate temperature fo r the growth of LT-GaAs layers. The origin of this surface modificatio n was studied by reflection high energy electron diffraction. The grow th regimes of LT-GaAs layers were studied by real-time ellipsometry. T he dielectric properties of the epitaxial layer and the critical thick ness for epitaxial growth were extracted for various growth conditions . The microstructure beyond the critical point was found to be compose d of amorphous as well as crystalline forms of GaAs.