Activation energy in low compensated homoepitaxial boron-doped diamond films

High-quality homoepitaxial diamond films have been grown on 100-type Ib synthetic diamond, and boron doped by diborane from 5 x 10(16) to 8 x 10(20) cm(-3). The current-temperature characteristics from 300 to 1000 K have been measured and fitted by the general expression of the conductivity in a compensated semiconductor in the ionisation regime. The saturation of the conductivity is observed between 680 and 1000 K for the samples doped below 2 x 10(17) cm-3. In the range 10(18)-10(19) cm(-3). an activation energy of 185 meV is observed between 500 and 1000 K and around 368 meV between 300 and 500 K. The activation energy of 185 meV corresponds to half the boron ionisation energy, and is related to the conduction regime in an uncompensated semiconductor. The evolution of these activation energies and of the room-temperature resistivity with the boron doping are presented. (C) 1998 Elsevier Science S.A.