Sublimation Growth and Performance of Cubic Silicon Carbide

Current advancement in electronic devices is so rapid that silicon, the semiconductor material most widely used today, needs to be replaced in some of the fields. Silicon carbide (SiC) is a wide band gap semiconductor satisfying requirements to replace silicon in devices operating at high power and high frequency at elevated temperature, and in harsh environments. Hexagonal polytypes of SiC, such as 6H-SiC and 4H-SiC are already available on the market of power devices. However, cubic SiC (3C-SiC) polytype is still not used in the industry. The essential issue here is the lack of commercial 3C-SiC substrates. This is mostly due to a high density of defects in the crystals, what renders the material not appropriate for device production. The most common defects are inclusions of other polytypes, twinned domains and stacking faults. Thus, to introduce the 3C-SiC into the electronics industry it is mandatory to understand material growth and defect formation, learn to control their appearance and on that basis to propose a growth method capable of large scale industrial production. The aim of this work was to develop operation conditions for fabrication of 3C-SiC crystals via understanding fundamentals of the growth process and to explore structural and electrical properties of the grown material, including its suitability for substrate applications. The physical vapor transport or sublimation process has already shown a capability to produce substantial quantities of large area and high quality hexagonal SiC substrates. For growth of 3C-SiC the same technique has not been successful because the cubic phase is metastable and therefore difficult to control in bulk growth geometry. In the present study similar growth principle, but in a different geometry, called sublimation epitaxy, was applied. Using this method very high growth rates (up to 1 mm/h) can be achieved for hexagonal SiC while maintaining high material quality. Additionally, the growth process does not require expensive or hazardous materials, thus making the method very attractive for the use in industry. In the present work 3C-SiC (111) was grown on 6H-SiC (0001) substrates. When growing 3C-SiC directly on 6H-SiC it was noticed that the substrate roughness does not have significant influence on the yield and quality of 3C-SiC. This was mostly due to the growth of homoepitaxial 6H-SiC appearing before 3C-SiC. Structural characterization showed that 3C-SiC grown directly on 6H-SiC substrate exhibited the highest quality as compared with other substrate preparation, such as annealing or deposition of a 3C-SiC buffer layer. Thus, further investigation was devoted to the growth of 3C-SiC on 6H-SiC substrates.