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Alloys of scandium with AlN exhibit an enhanced piezoelectric coefficient that can boost the performance of nitride‐based electronic and optoelectronic devices such as high electron mobility transistors (HEMTs). Consequently, there is increasing interest in the epitaxial growth of high‐quality AlScN/GaN heterostructures. So far, only very recent reports on AlScN HEMT structures grown by molecular beam epitaxy (MBE) have been published. Herein, the motivation for depositing AlScN epitaxial layers by metal‐organic chemical vapor deposition (MOCVD) as well as the challenges associated with this approach are explained. For the first time, the successful deposition of epitaxial layers with a Sc content up to 30% (Al0.7Sc0.3N) is reported. It is shown that the deposited films consist of wurtzite‐type AlScN with high crystalline quality, demonstrating that MOCVD is suitable for the growth of HEMT structures with Sc‐based ternary nitrides.

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The growth rate of a 4H-SiC epitaxial layer has been increased by a factor of 19 (up to 112 lm h -1 ) with respect to the standard process, with the introduction of HCl in the deposition chamber. The epitaxial layers grown with the addition of HCl has been characterized by electrical, optical, and structural characterization methods. The effects of various deposition parameters on the epitaxial growth process have been described, and an explanation of this behavior in terms of the diffusion coefficient on the surface, D s , and the ratio between the characteristic times, s D :s G , has been provided. The diodes, manufactured on the epitaxial layer grown with the addition of HCl at 1600°C, have electrical characteristics comparable with the standard epitaxial process. This process is very promising for high-power devices with a breakdown voltage of 10 kV.

The results of a new epitaxial process using an industrial 6x2” wafer reactor with the introduction of HCl during the growth have been reported. A complete reduction of silicon nucleation in the gas phase has been observed even for high silicon dilution parameters (Si/H2>0.05) and an increase of the growth rate until about 20 µm/h has been measured. No difference has been observed in terms of defects, doping uniformity (average maximum variation 8%) and thickness uniformity (average maximum variation 1.2 %) with respect to the standard process without HCl.

The epitaxial growth of 4H-SiC on on-axis substrates is a very important process to meliorate in order to accelerate the development and improve the performance of bipolar SiC-based power devices, but until now, only relatively low growth rate processes have been achieved. The aim of this study is to demonstrate a high growth rate deposition process of high-quality 4H-SiC epilayers on on-axis substrates, free of 3C-SiC inclusions. Previous studies showed that silicon-rich gas-phase conditions, high Cl/Si ratios, or both were vital in order to avoid 3C-SiC inclusions in the epitaxial layers when grown on on-axis substrates. This study combines the knowledge of surface pretreatment with the chloride-based chemistry developed for off-axis growth. Two different precursor approaches were used, one adopting silane and ethylene with addition of hydrogen chloride and the other based on methyltrichlorosilane (MTS). In this study, we show that using a MTS-based chemical vapor deposition (CVD) process in combination with proper in situ silane etching and accurate optimization of the other process parameters results in homoepitaxial growth of high-purity and high-quality 4H-SiC layers on on-axis Si-face substrates at a growth rate of 100 μm/h. A higher efficiency of the MTS precursor chemistry was found and discussed.

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