Hall measurements on nitrogen-doped Ib-type synthetic single crystal diamonds at temperatures 550–1143 K

Synthetic nitrogen-doped diamond single crystals have various high-tech applications, but their electronic properties have not been sufficiently studied. In this research, we investigated temperature dependencies in the range T = (550–1143) K of the electrical resistivity and Hall mobility in synthetic single-crystal Ib-type diamonds doped with nitrogen during growth. A series of experimental samples were cut from diamond crystals grown by temperature gradient high-pressure high-temperature (TG-HPHT) and chemical vapor deposition (CVD) methods. They contain (0.085–6.5) × 1019 cm−3 single substitutional nitrogen atoms (C-centers) as measured by optical spectrometry methods. The Hall mobility of free electrons decreases from 600 to 150 cm2 V−1 s−1 in the CVD grown sample with the lowest N content and from 300 to 100 cm2 V−1 s−1 in highly doped HPHT grown samples in the temperature range of 550–900 K. At T = (900–1100) K, the mobility decreases to 50 cm2 V−1 s−1 in highly doped samples. The activation energies of electrical conductivity Ea and impurity-to-band energies of nitrogen donors ED decrease with increasing N concentration in the ranges (1.55–1.32) and (1.63–1.33) eV, respectively. The lowest compensation ratio k ∼ 1% in the moderately doped CVD diamond is unique for n-type diamonds. Typical values of k in highly N-doped crystals are in the range of 10%–20%, facilitating the use of N-doped diamonds in durable high-temperature electronic devices.