EFFECTS OF DOPING ON GROWTH IN THE DICHLOROSILANE GERMANE SYSTEM

The effects of diborane and arsine on GexSi1-x growth rate and doping were studied in this paper. Dilute flows of diborane increased the growth rate, but had little effect on the activation energy. The growth rate of undoped films was increased linearly with germane flow then saturated, in good agreement with the literature. Under a dilute arsine flow we have observed for the first time that this description is no longer valid. The growth rate for As-doped films increases sublinearly with the germane flow, and saturates in a manner consistent with a reaction that is second order in GeH4. The activation energy also changes from 22 (undoped) to 42 kcal/mol (doped). Possible mechanisms are discussed. The active carrier concentrations have also been measured for these doped films. Dopant incorporation in the B2H6/GeH4/SiH2Cl2 is well described by a simple kinetic model, as in silicon epitaxy. For arsenic doping with arsine, a simple kinetic model cannot be used to describe the incorporation. We believe instead that a site competition mechanism is operative.