THE EFFECT OF BORON DOPING ON THE LATTICE-PARAMETER OF HOMOEPITAXIAL DIAMOND FILMS

The (004) X-ray rocking curves of undoped and boron doped homoepitaxia l diamond films have been recorded up to 8 x 10(20) [B] cm(-3). Up to this concentration the films grew coherently, i.e. the in-plane lattic e constant of the doped film is the same as that of the substrate. The lattice constants of the boron doped diamond films in their relaxed s tate have been determined. Boron incorporation induces a large expansi on of the lattice constants, especially above the semiconductor-metal transition. We suggest a contribution of both the different size of bo ron and carbon atoms (Vegard's law) and of hole concentration in the i mpurity band of boron [with a positive deformation potential of the im purity band of boron of 16 (+/-0.3) eV] to describe the experimental r esults. (C) 1998 Elsevier Science S.A.