Langmuir-Type Expressions for In-Situ Co-Doping of C with B or P in Si1–xGex Epitaxial Growth by Chemical Vapor Deposition

Abstract

In-situ co-doping process of C with B or P in Si1−xGex (100) epitaxial growth by chemical vapor deposition (CVD) is investigated using SiH4–GeH4–SiH3CH3–B2H6 or PH3–H2 mixture. The in-situ doping of only C is explained quantitatively by the Langmuir-type adsorption and reaction at Si-Si, Si-Ge or Ge-Ge pair sites on the (100) surface. For in-situ co-doping of C with B, it is concluded that SiH4, GeH4, SiH3CH3 and B2H6 molecules are adsorbed and react at the pair sites and react at the B-occupied sites where B2H6 molecules have been adsorbed at the pair sites and additionally B2H6 molecules react at the C-occupied sites where SiH3CH3 molecules have been adsorbed at the pair sites. For in-situ co-doping of C with P, it is concluded that SiH4, GeH4, SiH3CH3 and PH3 molecules are adsorbed and react at the pair sites and only GeH4 molecules decompose at the P-occupied sites where PH3 molecules have been adsorbed self-limitedly on the (100) surface without the reactions at the C-occupied sites. From these results, Langmuir-type quantitative expressions of the experimental results are confirmed for in-situ co-doping of C with B or P in Si1–xGex (100) epitaxial growth by CVD.