One of the most interesting wide-bandgap semiconductor is 4H-SiC that has an indirect wide-bandgap of 3.3 eV. This material holds great potential to develop power devices that find applications in the field of high-voltage and high-temperature electronics and harsh environments. In this study, we employed complementary noninvasive characterization techniques, including micro-Raman, optical absorption, steady-state, and time-resolved photoluminescence spectroscopy, to investigate the characteristics of a 12 μm thick epitaxial layer of 4H-SiC grown on 4H-SiC. Furthermore, we explored the impact of ionizing radiation on this material, utilizing β-rays and two x-ray sources. The doses are in the range of 1–100 kGy for electrons with energy of 2.5 MeV, 16 kGy for the first x-ray source (an x-ray tube with a W target operating at an anode bias voltage of 28 kV), and 100 kGy for the second x-ray source (an x-ray tube with a W target operating at an anode bias voltage of 100 kV). When exposed to the electron beam, the excitonic band at 3.2 eV exhibits a reduction in its lifetime as the deposited dose increases. In particular, in samples characterized by a greater amount of native defects, both extended and point defects, this effect becomes evident at lower deposited doses. Conversely, in the samples subjected to x-ray irradiation, these effects are not observed. These findings indicate that electron beam irradiation triggers the formation of defects associated with atomic displacement. Ultimately, we have examined the impact of thermal treatments in air, ranging from 100 to 900 °C, to investigate the recovery characteristics of 4H-SiC.

In this work, we conducted an analysis of 4H-SiC epitaxial layer grown on two distinct 4H-SiC substrates (both 6 inches in diameter) using non-invasive techniques such as micro-Raman spectroscopy, steady-state absorption spectroscopy and time-resolved photoluminescence spectroscopy. We have shown that despite the doping homogeneity, confirmed by micro-Raman and steady-state absorption spectroscopy, the carrier lifetime, assessed by monitoring the excitonic band at 3.2 eV by time-resolved photoluminescence spectroscopy, depends on the position on the wafer. This variability is attributed to the presence of defects, such as impurities or point defects, which are not uniformly distributed on the epitaxial layer and that, in addition to extended defects, affect the charge carrier recombination. Additionally, it is found that interactions with the underlying substrate could contribute to these effects as evidenced in regions of the substrate characterized by differences of doping.

Monolayer molybdenum disulfide is a semiconducting 2D material presenting very appealing characteristics for its incorporation into electronic flexible devices. At present, atomic vacancies in its structure are known to significantly affect its properties. Nonetheless, the effects of electron irradiation on it are still under investigation. In this work, the structural, electronic, and optical properties of monolayer molybdenum disulfide are studied before and after electron irradiation. By analyzing samples either obtained via a mechanical exfoliation process or grown via chemical vapor deposition, we show that following irradiation no significant change is present. This result indicates a strong resistance to the effect of electron irradiation at energies able to induce the formation of sulfur vacancies. By comparing our results to the current literature, we hypothesize that previously reported effects of electron irradiation are either due to the formation of molybdenum vacancies or to ionization of the electronic shell of this material. The presented results help to shed light on the role of atomic vacancies on the properties of this 2D material from a fundamental point of view and on its usage in extreme environment applications.

Silicon carbide is a wide-bandgap semiconductor useful in a new class of power devices in the emerging area of high-temperature and high-voltage electronics. The diffusion of SiC devices is strictly related to the growth of high-quality substrates and epitaxial layers involving high-temperature treatment processing. In this work, we studied the thermal stability of substrates of 4H-SiC in an inert atmosphere in the range 1600–2000 °C. Micro-Raman spectroscopy characterization revealed that the thermal treatments induced inhomogeneity in the wafer surface related to a graphitization process starting from 1650 °C. It was also found that the graphitization influences the epitaxial layer successively grown on the wafer substrate, and in particular, by time-resolved photoluminescence spectroscopy it was found that graphitization-induced defectiveness is responsible for the reduction of the carrier recombination lifetime.