TRANSPORT STUDIES IN BORON-ION IMPLANTED TYPE IIA DIAMOND

We have investigated low-temperature electrical transport mechanisms i n the surface layer of a type IIa diamond which has been heavily impla nted with boron-ions at low temperatures and then annealed at high tem peratures. The boron atoms occupy substitutional sites giving nse to a heavily doped wide-bandgap semiconductor. The de-conductivity results suggest that for the maximum boron doping that has been achieved, the diamond sample is close to the insulator-metal transition. A model to account for the observed increase in activated boron centres with ion dose is presented. On the insulating side of the transition,the data are interpreted in terms of variable-range hopping laws.