Electrical and Optical Properties of Type IIb Diamonds

Abstract

The d.c. Hall coefficient and resistivity of six semiconducting diamonds have been measured as a function of temperature from 200 to 800°K. All the diamonds were p-type semiconductors. From the measurements the effective mass of the charge carriers, the concentration of donor and acceptor centres, the activation energy of the acceptors (close to 0.34 eV) and the temperature dependence of the Hall mobility have been calculated. At high temperatures the mobility varies as T^-2.8. The relative strengths of certain peaks in the infra-red absorption spectrum are the same in different specimens. It is concluded that all these peaks are due to the same centre. These peaks are not detected in type I and type IIa diamonds. There is a strong correlation between the strength of the strongest peak at 0.346 eV and the number of vacant acceptor levels at room temperature, from which it is concluded that the centre giving rise to the peaks is also responsible for conduction.