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

Abstract

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 3×1017cm–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 0.002at.% 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 2200cm2 / (V×s) at T=300K and 7200cm2 / (V×s) at T=180K. The phonon scattering of holes dominates in the entire temperature range of 180–800K, 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 0.002at.% of boron may serve as reference semiconductor materials.