Electrical properties of the high quality boron-doped synthetic single-crystal diamonds grown by the temperature gradient method

• We investigated high-quality boron-doped HPHT single crystal diamonds.
• Uniformly doped samples free of extended structure defects were cut.
• Electrical conductivity and Hall coefficient were measured at T = 150–800 K.
• The lattice phonon scattering of charge carriers dominates.
• Diamonds with (3 ÷ 7) × 1015 cm–3 boron content may serve as reference semiconductors.

Temperature dependencies of the resistivity and the Hall coefficient in high-quality boron-doped synthetic single crystal diamonds grown by the high-pressure-high-temperature (HPHT) method with different boron contents have been investigated. The concentration of acceptors was varied in the range of 2 × 1015 to 3 × 1017 cm–3 in (001) cut plates by a change of boron content in a growth mixture in a range from 0.0004 to 0.04 atomic percent. A special sample preparation has been used for precise measurements. Thin rectangular plates with uniform boron content and without linear and planar structure defects have been laser cut after X-ray topography and UV-luminescence mapping. The donor and acceptor concentrations in each sample have been calculated from the Hall effect data and capacitance–voltage characteristics. The concentrations correlate with the boron content in a growth mixture. Minimum donor to acceptor compensation ratio slightly below 1% was observed at 0.002 at.% boron content in a growth mixture, while it increased at an increase and decrease of boron amount. Samples grown at such boron concentration had maximum carrier mobility. It was 2200 cm2 / (V × s) at T = 300 K and 7200 cm2 / (V × s) at T = 180 K. The phonon scattering of holes dominates in the entire temperature range of 180–800 K, while the scattering by point defects such as neutral and ionized impurity atoms is insignificant. Due to a perfect crystal quality and lattice scattering mechanism bulk diamond crystals grown from the mixture containing 0.0005 to 0.002 at.% of boron may serve as reference semiconductor materials.