SURFACE-MORPHOLOGY AND QUALITY OF STRAINED INGAAS GROWN BY MOLECULAR-BEAM EPITAXY ON GAAS

InGaAs layers of varying epilayer thickness grown at different temperatures on GaAs substrates by molecular-beam epitaxy are analyzed by atomic force microscopy. The surface roughness and morphology of InGaAs grown at substrate temperatures ranging from 450 to 530-degrees-C are analyzed as the epilayer thickness is increased from 100 to 800 angstrom. Over an area of 100 mum2, an abrupt increase in the surface roughness probably indicates an acceleration of surface roughening mechanisms related to the process of strain relaxation. At higher InGaAs thicknesses, surface corrugations were observed. The results indicate that thicker pseudomorphic InGaAs films on GaAs substrates can be grown at lower temperatures. Raman spectroscopy data of strain-induced shifts in the GaAs-like mode longitudinal optic phonon indicate that the GaAs has tensile strain along the interface. The strain calculated from the observed frequency shift agrees with the lattice-mismatch strain given by the elasticity theory.