The p-type doping efficiency of 4H silicon carbide (4H-SiC) is rather low due to the large ionization energies of p-type dopants. Such an issue impedes the exploration of the full advantage of 4H-SiC for semiconductor devices. In this study, we show that co-doping group-IVB elements effectively decreases the ionization energy of the most widely used p-type dopant, i.e., aluminum (Al), through the defect-level repulsion between the energy levels of group-IVB elements and that of Al in 4H-SiC. Among group-IVB elements Ti has the most prominent effectiveness. Ti decreases the ionization energy of Al by nearly 50%, leading to a value as low as ∼ 0.13 eV. As a result, the ionization rate of Al with Ti co-doping is up to ∼ 5 times larger than that without co-doping at room temperature when the doping concentration is up to 1018 cm−3. This work may encourage the experimental co-doping of group-IVB elements such as Ti and Al to significantly improve the p-type doping efficiency of 4H-SiC.

One of the major challenges of 4H-silicon carbide (4H-SiC) is that the preparation of low resistivity p-type 4H-SiC single crystals lags seriously behind that of low resistivity n-type 4H-SiC single crystals, hindering the development of important 4H-SiC power devices such as n-channel insulated gate bipolar transistors. In particular, the resistivity of p-type 4H-SiC single crystals prepared through the physical vapor transport technique can only be lowered to around 100 mΩ cm. One of the key causes is the incomplete ionization of the p-type dopant Al with an ionization energy ∼0.23 eV. Another factor is the compensating effect. It cannot simply assume nitrogen (N) is the sole compensatory center, since the number of the compensating center is larger than the concentration of N doping. In this work, we systematically investigate the compensation of native defects and self-compensation in Al-doped 4H-SiC. It is found that the positively charged carbon vacancies [Formula: see text] are also the dominant compensating centers in Al-doped 4H-SiC. When the Al concentration is in the range of 1016–1019 cm−3, the concentration of holes is lower by one order of magnitude than the Al concentration because of the compensation of [Formula: see text]. As the Al concentration exceeds 1020 cm−3, the concentration of holes is only in the order of magnitude of 1019 cm−3 owing to the dominant compensation of [Formula: see text] and supplementary self-compensation of interstitial Al [Formula: see text]. We propose that the passivation of [Formula: see text] as well as quenching is effective to enhance the hole concentration of Al-doped 4H-SiC.

SiC crystal is an excellent substrate material for high power electronic devices and high-frequency electronic devices. Being cost-effective and defect-free are the two biggest challenges at present. For the physical vapor transport (PVT) growth of a SiC single crystal, SiC powder is used as the source material, which determines the cost and the quality of the crystal. In this paper, we propose a new design in which graphite blocks are substituted for the non-sublimated SiC powder. Temperature distribution in the SiC powder, the evolution of the SiC powder, and the vapor transport are investigated by using finite element calculations. With the addition of graphite blocks, the utilization and sublimation rate of SiC powder is higher. In addition, the reverse vapor transport above the SiC powder is eliminated. This design provides a new idea to reduce the cost of SiC crystals in industrialization.

As a common impurity in 4H-silicon carbide (4H-SiC), hydrogen (H) may play a role in the tuning of the electronic properties of 4H-SiC. In this work, we systemically explore the effect of H on the electronic properties of both n-type and p-type 4H-SiC. The passivation of H for intrinsic defects such as carbon vacancies (VC) and silicon vacancies (VSi) in 4H-SiC is also evaluated. We find that interstitial H at the bonding center of the Si-C bond (Hi bc) and interstitial H at the tetrahedral center of Si (Hi Si-te) dominate the defect configurations of H in p-type and n-type 4H-SiC, respectively. For n-type 4H-SiC, the compensation of Hi Si-te is found to pin the Fermi energy and hinder the increase of electron concentration for highly N-doped 4H-SiC. The compensation of Hi bc is negligible compared to that of VC on the p-type doping of Al-doped 4H-SiC. We have further examined whether H can passivate VC and improve carrier lifetime in 4H-SiC. It turns out that nonequilibrium passivation of VC by H is effective to eliminate the defect states of VC, which enhances the carrier lifetime of moderately doped 4H-SiC. Regarding the quantum-qubit applications of 4H-SiC, we find that H can readily passivate VSi during the creation of VSi centers. Thermal annealing is needed to decompose the resulting VSi-nH (n=1~4) complexes and promote the uniformity of the photoluminescence of VSi arrays in 4H-SiC. The current work may inspire the further development of the impurity engineering of H in 4H-SiC.

The widespread use of 4H silicon carbide (4H-SiC) is just around the corner since high-power electronics based on 4H-SiC are increasingly fabricated to enable the low-carbon development of the world. Quantum technologies are also intensively explored by scrutinizing 4H-SiC as a platform for wafer-scale integration of semiconductor and quantum technologies. Given the importance of impurities and defects for any semiconductor, comprehensive and insightful understanding of impurities and defects in 4H-SiC is imperative. In this Perspective, we summarize recent experimental and theoretical advances in researches on impurities and defects in 4H-SiC after briefly reviewing the history of 4H-SiC. Impurity engineering and defect engineering for the realization of the full potential of 4H-SiC are also discussed. Challenges for the study on impurities and defects in 4H-SiC are finally outlined.