TOWARD DEVICE-QUALITY GAAS GROWTH BY MOLECULAR-BEAM EPITAXY ON OFFCUTGE SI1-XGEX/SI SUBSTRATES/

The epitaxial growth of GaAs on Si substrates through the use of a Ge/ graded Si1-xGex/Si buffer layer would allow monolithic integration of GaAs-based opto-electronics with Si microelectronics. As an initial st ep toward this goal, this study examines factors which influence the q uality of GaAs growth by molecular beam epitaxy (MBE) on bulk Ge subst rates. Key findings include the need for an epitaxial Ge smoothing cap deposited in the MBE chamber, the significant detrimental effect of A s overpressure on the resultant GaAs crystalline quality, and the effi ciency of a very thin (similar to 3 nm) migration enhanced epitaxy (ME E) nucleation layer at suppressing both anti-phase domain (APD) format ion and interdiffusion across the GaAs/Ge heterointerface. Using this developed optimized growth process, APD-free GaAs on Ge is obtained wh ich has undetectable Ga and Fe cross-diffusion, and As diffusion into the substrate at less than or equal to 1 x 10(18) cm(-3). Preliminary results for growths on Ge/Si1-xGex/Si substrates are also presented. ( C) 1998 American Vacuum Society.