**5. Conclusions**

This paper gave an overview of the processing technology associated with heteroepitaxial 3C-SiC-on-silicon, including the more recently available bulk 3C-SiC studies. This topic is highly relevant today since this material presents some clear advantages over its commercial WBG competitors in terms of MOS channel resistance and reliability. These factors are of the utmost importance when considering that it is the automotive sector that is driving the widespread uptake of WBG technologies. Schottky contact processing on 3C-SiC has mainly been conducted on heteroepitaxy (on-silicon) utilising high work function metals such as Au or Pt. These rectifying contacts are typically characterised by high leakage currents arising from SFs and APBs and it is clear that a step-change in material quality is needed for power device applications. To the best of the authors' knowledge, there remains no semiconductor device grade wafer supplier of bulk 3C-SiC. However, heteroepitaxial 3C-SiC-on-silicon is available up to a wafer diameter of 4 inch. The main obstacle to large diameter 3C-SiC commercialisation remains the SF density that ranges from 200–5000 cm−<sup>1</sup> . Hence, the future prospects for 3C-SiC are incumbent upon reducing SFs and APBs, which remains key to realising large diameter 3C-SiC bulk wafer production. 3C-SiC-on-silicon demonstrates serious limitations when the ion implantation process is taken into consideration. Therefore, the majority of studies to date have used conventional PIA annealing up to 1400 ◦C (melting temperature of silicon substrate) and pulsed laser annealing. Generally, dopant activation rates are low in 3C-SiC heteroepitaxy structures, although recently more promising behaviour has been described on free standing (bulk) 3C-SiC. Most recently p-type aluminium doped 3C-SiC has been demonstrated with weak p-type behaviour. N-type ohmic contacts have been consistently achieved using metals such as Ni, Al, Ti, Au and W demonstrating specific contact resistivities as low as <sup>5</sup> <sup>×</sup> <sup>10</sup>−<sup>7</sup> <sup>Ω</sup>cm<sup>2</sup> . The success is related to the high n-type ion implantation activation/ionisation rates accompanied by the low donor levels relative to 4H-SiC. P-type ohmicity based on metals including Al, Ni, Ti and poly-silicon have produced resistances in the region of ~10−<sup>5</sup> Ωcm<sup>2</sup> . Compared to n-type donor levels in 3C-SiC, p-type acceptor energy levels are closer to the midgap, resulting in a lower degree of acceptor ionization. Diodes based on Schottky and PiN designs have been demonstrated on 3C-SiC. The state of the art with respect to diodes are bulk PiN structures with a built-in voltage of 2V and current density of 1000 Acm−<sup>2</sup> observed. The 3C-SiC MOS interface is relatively untroubled by near interface traps when compared to its 4H-SiC counterpart. This can be inferred from experimental results based on nitrogen anneals where channel mobilities approaching 100 cm2/Vs have been observed. Again nitrogen-based thermal oxidation produced interface trap densities in the region of 10<sup>11</sup> cm−<sup>2</sup> eV−<sup>1</sup> . A reliability analysis of the 3C-SiC MOS interface revealed high breakdown fields in the region of 8MV/cm including cumulative device failure arising primarily from 3C-SiC crystal defects (TDDB). Actual MOSFET demonstrators are plagued by high leakage currents resulting from crystal defects. Thus, 600V 3C-SiC MOSFETs that approach the theoretical unipolar limit have been demonstrated.

**Author Contributions:** Conceptualization, writing, review and editing, F.L., M.J., F.R.; experimental investigation, F.L., M.J., F.R., G.G., P.F.; data analysis and discussion, J.E.E., F.A.M., F.L., C.A.F., A.P.-T., P.A.M., P.F., M.J., F.R.; funding acquisition, F.L.V. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the European Union within the framework of the project CHALLENGE, grant number 720827.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** The data underlying this article will be shared on reasonable request from the corresponding author.

**Conflicts of Interest:** The authors declare no conflict of interest.
