The influence of substitutional carbon on the Si Ge interdiffusion studied by x-ray diffractometry at superlattice structures

Si/Ge interdiffusion in SiGe(C)/Si(C) superlattice (SL) structures with different positions and concentrations of substitutional carbon was studied under atmospheric and high hydrostatic pressure in the temperature range 700-950 degrees C for Ge (about 20%) and carbon (0-0.5%) concentrations, which are relevant for modem SiGe(C) device applications. The coefficient of the Si/Ge interdiffusion increases linearly with the carbon concentration and the total amount of carbon in the SL structure. With increasing hydrostatic pressure a further increase of the diffusion was observed. Both effects could be interpreted by a modification of the point defect spectrum with an undersaturation of Si self-interstitials and a supersaturation of vacancies.