Self-limiting segregation and incorporation during boron doping of Si and SiGe

We have studied the experimental conditions to obtain highly boron-doped th in layers (delta-doping) in Si and SiGe during gas source molecular beam ep itaxy (GSMBE). Pre-deposition and the co-deposition of boron have been comp ared by secondary ion mass spectroscopy (SIMS) and electrochemical capacita nce-voltage profiling eC(V). We have shown that provided a pre-deposition s tep is used before co-deposition, higher doping levels are obtained without degrading the abruptness of the interfaces. This is explained by a coverag e limit of boron during the pre-deposition step, above which islanding occu rs and degrades the crystalline quality of the film. In addition, a reflect ion high-energy electron diffraction (RHEED) oscillation study shows that t here exists a virtually constant boron coverage of the surface during the S i and SiGe overgrowth, which produces a decrease of the growth rate.