A large range of boron doping with low compensation ratio for homoepitaxial diamond films Original Research Article

A large range ([B] from 5×1016 to 8×1020 cm−3) of boron concentration has been obtained for homoepitaxial diamond films. From the variation of the conductivity versus temperature between 300 and 1000 K, a simpler method is used to derive the activation energy(ies) Ea and the compensation ratio than from the variation of the hole concentration and mobility with temperature. For [B]<2×1017 cm−3, a saturation of the conductivity is observed between 680 and 1000 K, Ea=Ei (ionisation energy of the boron), and compensation ratio around 10% is deduced. Then, up to 1019 cm−3, an additional Ea=Ei/2=185 meV is observed between 500 and 1000 K, with compensation ratio <10%. At higher [B], an additional nearest neighbour hopping contribution to the conduction is obtained from the formation of the boron impurity band. It dominates and gives metallic conductivity when [B]=3×1020 cm−3.