CHARACTERIZATION OF GAAS BUFFER LAYERS 0.1 MU-M THICK GROWN ON SI(100)

We present Raman scattering measurements for GaAs buffer layers 0.1 μm thick grown on off-axis Si(100) substrates by molecular beam epitaxy. Using the scattering configuration X(YZ)X, only the longitudinal optic (LO) phonon mode is "allowed" and the observation of the "forbidden" transverse optic (TO) phonon reflects the degree of disorder present in the GaAs layer. We have measured the variation of TO:LO intensity as a function of substrate preparation and growth temperature. Our results indicate that buffer layers grown at T≈300 °C give the lowest TO:LO ratio. Ramping the substrate temperature from T≈300 °C to T≈580 °C (the active layer growth temperature) gives rise to a reflection high energy electron diffraction pattern indicative of a (2 × 4) single-domain surface reconstruction and a corresponding decrease in the TO:LO ratio. A comparison is also made of layers of GaAs 4.1 μm thick grown on Si(100) and Si(111) respectively, for identical substrate preparation and buffer layer deposition. © 1990.