Electrical properties of a B doped layer in diamond formed by hot B implantation and high-temperature annealing

The influence of hot B implantation into diamond and postimplantation high-temperature annealing at 1600 °C on doping properties has been investigated. B multiple ion implantation was performed at 30–360 keV into high-pressure, high-temperature synthetic type-IIa diamond or high-quality homoepitaxially grown diamond films at 400 °C, followed by 1450 °C and higher temperature (1600 °C) annealing. Optical transmission spectra indicated that radiation damage was almost removed with an increase in annealing temperatures up to 1600 °C. In the sample of 5 × 1018 cm− 3 using a type-IIa substrate, the hole concentration and the Hall mobility were 2 × 1013 cm− 3 and 55 cm2/Vs after 1450 °C annealing, respectively. After 1600 °C annealing, their values increased to 6.5 × 1013 cm− 3 and 82 cm2/Vs, respectively. The doping efficiency of the sample after 1600 °C annealing ~ 50% is the highest ever reported for B implanted diamond. By contrast, in the sample of 5 × 1019 cm− 3 using a type-IIa substrate, high-temperature annealing at 1600 °C resulted in the appearance of hopping conduction in the low-temperature region below 400 K. In the case of a homoepitaxial film B doped at 5 × 1019 cm− 3, band conduction is still dominant even after such 1600 °C annealing, giving an increase in the hole concentration in the valence band. The resultant resistivity of the film became much lower than that of annealing at 1450 °C.