Sharp boron doping within thin SiGe layer by rapid thermal chemical vapour deposition

Abstract

Boron δ doping of Si and SiGe has been investigated using rapid thermal chemical vapour deposition from the SiH₄–GeH₄−H₂ system with B₂H₆ as the B source gas. By incorporation of B into the growing Si film, B peaks with an exponential decay length of 1·7 nm/ decade were prepared. The B peak concentration was found to be dependent on Ge concentration, doping time, and doping temperature. An explanation of the results obtained is proposed based on a transitional behaviour between equilibrium and kinetic control of the process. If the B δ doping is carried out by interrupting the epitaxy, the process is controlled by the surface adsorption equilibrium. Hence B δ layers of about one monolayer thickness were prepared in Si and SiGe with an exponential decay length of 1·4 nm/decade at a temperature of 350°C.

MST/3293