Dynamics and surface segregation during GSMBE of Si/sub 1-y/C/sub y/ and Si/sub 1-x-y/Ge/sub x/C/sub y/ on the Si[001] surface

Incorporation of carbon in the base region of Si/sub 1-x/Ge/sub x/ heterojunction bipolar transistors has been shown to have the benefit of strain compensation and more importantly, the suppression of transient enhanced diffusion of boron. However, the required carbon concentration exceeds its solubility limit in silicon and a growth process occurring far from thermodynamic equilibrium is necessary in order to avoid carbon clustering. GSMBE, like its CVD counterpart is ideally suited to this requirement and its low operating temperature also favours substitutional incorporation of carbon, necessary for the suppression of TED of boron. In the work reported here, Si and Si/sub 1-x/Ge/sub x/ films containing small amounts of substitutional carbon (< 1.5%) were grown using GSMBE with disilane, germane and methylsilane (MS) precursors. The growth processes are investigated by in-situ techniques including RHEED intensity oscillations, temperature programmed desorption and ex-situ characterisation by X-ray diffraction and SIMS measurements.