Electrical properties and conduction mechanisms of heavily B+-ion-implanted type IIa diamond: effects of temperatures during the ion implantation and postannealing upon electrical conduction

We investigated the electrical properties and conduction mechanism of heavily B+-implanted type IIa diamond with respect to the implantation and postannealing temperatures. The B atoms were shallowly implanted with a flat concentration of 3.5 × 1019 cm−3 at RT and 900 °C; these samples were finally annealed at 1150 °C, 1300 °C and 1450 °C. We consequently confirmed p-type conductivity and typical ionization energy of acceptor B in a wide measured temperature range. The doping efficiency progressed remarkably well and attained 78% and the Hall mobility at RT was realized to be 108 cm2V−1s−1 for the RT-implanted sample followed by annealing at 1300 °C. On the other hand, hot B+ implantation at 900 °C slightly degraded the electrical properties. The higher-temperature annealing at 1450 °C after B+ ion implantation promoted hopping conduction fairly well at a lower measured temperature range below around RT. We systematically investigated the hopping conduction mechanism based on theoretical relations.