Integration of low-temperature GaAs on Si substrates

GaAs was grown on Si substrates by molecular-beam epitaxy at low substrate temperatures. Femtosecond time-resolved reflectivity investigations revealed a significant reduction of carrier lifetime in GaAs epilayers from 14 ps to <0.5 ps as the growth temperature was reduced from 400 to 150 °C. Photoconductors were fabricated on the epilayers, and electro-optic sampling was used to confirm the electrical response times of <1 ps. The responsivity is comparable to that for low-substrate-temperature GaAs grown on GaAs substrates, with a photogenerated carrier mobility of ∼100–300 cm2/V s. The low growth temperatures allow ultrafast GaAs-based photodetector incorporation into Si-based integrated circuits for novel optoelectronic applications.