Conductivity of Heavily Boron-Doped Diamond: Modeling and Manifestations in Admittance Spectroscopy Measurements

Results of admittance spectroscopy measurements of heavily boron-doped diamond characteristics are analyzed. The following observed features are explained by calculating changes in positions and widths of dopant zones: a different value of the dopant activation energy and a characteristic breakpoint on the conductivity temperature dependence. The calculation reveals a countermovement of the ground state zone and the group of highly excited states inside the diamond bandgap. As a result, the Fermi level at high dopant concentrations crosses the first excitation potential with temperature decreasing to a certain value. Consequently, there is a jump in the dopant′s effective activation energy, and the hopping conductivity mechanism is initiated. This behavior is naturally realized in high-frequency admittance spectroscopy measurements.