**1. Introduction**

Power electronics is a key enabling technology for energy generation, transmission, distribution and motion. The importance of this technology is emphasised by the fact that a 40% increase in energy consumption within 20 years is expected [1]. Moreover, 80% of electrical energy will be processed by a power electronic converter by 2030 [2]. Recently, power electronic converter and device technology has been driven by the huge demand seen within the electric vehicle (EV) sector. EV sales are set to reach 18 million by 2023, representing 16.2% of total global vehicle sales [3]. Together, these circumstances project the ever-increasing demand for power electronics on a global scale. In order to meet this required capacity and while still safeguarding our environment, power converters with near-100% energy-efficiency that are lightweight and compact need to be delivered.

**Citation:** Li, F.; Roccaforte, F.; Greco, G.; Fiorenza, P.; La Via, F.; Pérez-Tomas, A.; Evans, J.E.; Fisher, C.A.; Monaghan, F.A.; Mawby, P.A.; et al. Status and Prospects of Cubic Silicon Carbide Power Electronics Device Technology. *Materials* **2021**, *14*, 5831. https://doi.org/10.3390/ ma14195831

Academic Editor: Alexander A. Lebedev

Received: 20 July 2021 Accepted: 25 September 2021 Published: 5 October 2021

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Furthermore, attention must be paid to the lifetime (or longevity) of these systems, meaning increased reliability within the field.

Such a step-change intervention within the world of power electronics requires advancements within the fundamental semiconductor materials that serve to underpin our energy landscape. The underpinning technologies with respect to power electronics are its constituent high-voltage semiconductor devices. Consequently, these devices represent the largest cost associated with the overall power converter (40% of the total bill of materials for a typical 50 kW EV inverter). Traditionally for the last 50 years, silicon (Si) has dominated the power electronics industry as the semiconductor material of choice. However, the demand for increased energy-efficiency and power density together with higher voltage and current operation mean that a new era in semiconductor materials has dawned. Wide bandgap (WBG) semiconductor materials come with the promise to overcome the inherent material limits imposed by Si. 4H-silicon carbide (4H-SiC) and gallium nitride (2H-GaN or GaN) have emerged as the WBG materials of choice that have replaced Si in many power electronic applications.

For the moment, GaN devices that are based mainly on the high electron mobility transistor (HEMT) architecture are limited commercially to a maximum of 650 V. From the reliability perspective, GaN HEMTs have traditionally suffered from a poor thermal conductivity and the "current collapse" phenomenon, degrading their ability to function within harsh environments and high reliability electronics [4]. 4H-SiC, on the other hand, suffers from numerous reliability issues that are hampering its widespread uptake within the automotive sector. In particular, although SiC Trench MOSFETs exhibit superior onstate resistance compared to both GaN and silicon, the ruggedness of the gate oxide is the limiting factor. Gonzalez et al. [5] note that the competing WBG material technologies centre around the 650 V mark.

Early stage research devices are based on so-called ultrawide bandgap oxide materials such as gallium oxide (Ga2O3, with β-Ga2O<sup>3</sup> being the most stable). Thus far, β-Ga2O<sup>3</sup> suffers from a poor thermal conductivity, a modest bulk mobility and lack of p-type conductivity. Other ultrawide bandgap materials, including diamond and aluminium nitride (AlN), suffer from a lack of n-type conductivity and a poor bulk electron mobility, respectively. It should be noted that GaN, β-Ga2O3, and AlN are direct bandgap materials, which severely limits bipolar operation, which is required for higher voltages [6].

This review will place the cubic SiC (3C-SiC) material into the context of power electronic devices; however, it should be noted that other application areas such as biomedical sensors and micro-electromechanical systems (MEMS) are also appropriate and more popular for this SiC polytype. The authors will endeavour to provide a brief insight into some of the advantages of 3C-SiC from the scientific materials perspective in addition to some of the technological issues that must be overcome to realise competitive power MOSFETs and diodes. In particular, the focus will be placed on fundamental semiconductor fabrication technologies; the 3C-SiC/SiO<sup>2</sup> metal-oxide-semiconductor (MOS) interface, ion implantation, ohmic and Schottky contacts.
