A large range (B from 5-10~16 to 8*10~20 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) E_a and the compensation ratio from the variation of the hole concentration and mobility with temperature. For B<2*10~17 cm~(-3), a saturation of the conductivity is observed between 680 and 1000 K, E_a=E_i (ionisation energy of the boron) ,and compensation ratio around 10 is deduced. Then, up to 10~19cm~(-3), an additional E_a=E_i/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*10~20 cm~(-3).
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