Electrical and optical properties of non-uniform semiconducting synthetic diamond with deep impurity levels

Synthetic boron-doped p-type single crystals of diamond possess a low-resistance surface layer. The photoconductivity of the bulk high-ohmic region exponentially increases with the increase of temperature. The activation energy of this dependence is 0.4 eV at low electric field and 0.3 eV at high field. The change of activation energy is explained on the basis of the hydrogen-like model of the boron acceptor center. In high electric field the electric current instability is observed connected with the deep levels recharging and thermal breakdown phenomena.