Subpicosecond carrier dynamics in low-temperature grown GaAs on Si substrates

This letter describes time-resolved differential reflection measurements on low-temperature grown GaAs on (100) Si substrates. The carrier recombination depends sensitively on growth and anneal conditions. The differential reflectance signals of samples annealed at 600 °C are dominated by an exponential subpicosecond transient, which can be as short as 370 fs. Optical microscopy and atomic force microscopy show that the films are comparably smooth or smoother than other GaAs material grown on Si. X-ray diffraction indicates tensile strain in the films, which is explained by the different thermal expansion coefficients of GaAs and Si.