Computational Evaluation of Electrical Conductivity on SiC and the Influence of Crystal Defects

Abstract

The main electronic characteristics of silicon carbide (SiC) are its wide energy gap, high thermal conductivity, and high break down electric field which make of it of one of the most appropriate materials for power electronic devices. Previously we reported on a new electrical conductivity evaluation method for nano-scale complex systems based on our original tight-binding quantum chemical molecular dynamics method. In this work, we report on the application of our methodology to various SiC polytypes. The electrical conductivity obtained for perfect crystal models of 3C-, 6H- and 4H-SiC, were equal to 10-20-10-25 S/cm. For the defect including model an extremely large electrical conductivity (of the order of 102 S/cm) was obtained. Consequently these results lead to the conclusion that the 3C-, 6H-, and 4H-SiC polytypes with perfect crystals have insulator properties while the electrical conductivity of the crystal with defect, increases significantly. This result infers that crystals containing defects easily undergo electric breakdown.

Effect of mono vacancy on electron and positron properties of 3C SiC

“…This model corresponds to 1/128 ≈ 0.75% concentration of vacancies per unit volume. Similar 10, 17 or even higher 8, 9 concentration of point defects has been considered by other authors as well. Tests made in Ref.…”

“…In the upper subband, deep below the Fermi level, the localised occupied electron state can be seen in the DOS 9. As can be well seen in the density of states shown in Figure 3, this is the common feature of the perfect 8–10, 12, 17 and containing vacancy crystal 8–10. Presence of point Si or C vacancy gives rise to second, unoccupied, electron resonance state occurring in the DOS above the Fermi level 8, 9.…”

“…This is rather surprising result, nevertheless it can be justified by calculation and conclusions of Ref. 17. Liu et al show that if the C atom is subtracted from the 3C SiC polytype, the band gap transforms from the indirect to the direct one, the gap shifting arises and the crystal presents metallic.…”

“…The value obtained in the present work, E gap = 2.15 eV, is slightly lower than the reported experimental data, 2.36 eV 6. It should be mentioned here that application of the LDA or GGA to the electron–electron exchange and correlations leads to underestimation of the energy band gap 8, 9, 12, 17, while errors due to ASA increase E gap close to experimental value. Application of LDA + U 8 or self‐energy correction 9 improves the results.…”

When epitaxy meets plasma: a path to ordered nanosheets arrays

“…In the present study, both, the 3C-SiC “seeding layer” as well as the 3C-SiC NSs should show a good conductivity as they feature a large number of planar defects. The latter, according to Tsuboi et al's calculation, results in an extremely high electrical conductivity (of the order of 10 2  S/cm)43. This assumption is confirmed by Song et al's experimental observation.…”