A model of ionization equilibrium and Mott transition in boron doped crystalline diamond

Abstract

The screening of an impurity ion in diamond by both the holes hopping via boron atoms in charge states (0) and(-1) and the holes of the valence band is calculated in the Debye-Hilckel approximation. It is shown that a decrease of me ionized boron atom affinity to valence band hole is determined by its screening. An expression for the dependence of differential thermal ionization energy E1 of boron atoms on their concentration N is obtained in the quasiclassical approximation. Calculated dependence of valence band hole concentration p on N agrees with known experimental data, when the contribution of hopping conductivity to Hall effect may be neglected. A probability density function of the impurity ions and the valence band holes distribution over the crystal is assumed to be Poisson-like, while their electrostatic potential energy distribution is taken to be normal. The calculations of E1(N) and the critical concentrations of boron atoms N = NM for me insulator-metal phase transition (Mott transition) at different compensation ratios are compared with experimental data. © 2009 WlLEY-VCH Verlag GmbH & Co. KGaA.