Materials Science Forum Vols. 645-648

Abstract: We investigated the crystalline quality and electrical properties of the channel regions in 4H-SiC buried gate static induction transistors (SiC-BGSITs). To accurately determine the characteristics of the channel regions, we performed transmission electron microscopy and scanning spreading resistance microscopy. It was found that the channel regions have high crystalline quality and no significant fluctuations in doping concentration.

Abstract: In this article, using Kinetic Monte simulations on super-lattices, we study the evolution of extended defects during epitaxial growth. Specifically we show that, in the case of misoriented, close-packed substrates, a single-layer stacking fault can either extend throughout the entire epilayer (i.e. extended from the substrate up to the surface) or close in a dislocation loop depending on the deposition conditions and the crystallographic structure of the exposed surface containing the defect. We explain this behaviour in terms of a surface kinetic competition between the defect and the surrounding, perfect crystal: if the growth rate of the defect is higher compared to the growth rate of the surrounding crystal the defect will expand, otherwise it will close. This physical mechanism allows us to explain several experimental results of homo- and heteroepitaxy.

Abstract: In this study, we investigated the cluster effect on the occurrence of giant step bunching. We generated carbon clusters on 4H-SiC (0001) surfaces by thermal decomposition of SiC in an Ar atmosphere and controlled the surface concentrations of the clusters by adding H2 gas. We found the boundaries between surfaces with and without giant steps to show Arrhenius-type behavior. This behavior agreed with our predictions deduced from a chemical reaction model that takes the cluster effect into account, suggesting that giant step bunching is attributable to the formation of clusters on SiC.

Abstract: To observe the direction of the surface polariton wave excited by the external radiation on the semi-infinite crystal surface, the opaque mask was placed onto the sample surface. The penetration of the surface polariton wave from the open surface in beneath the metal mask was observed via small openings in the mask. It was shown that despite the k-vector mismatch between the surface polariton states and the light in the environmental media (vacuum), non-zero efficiency of the surface wave excitation is still present and that the k-vector of the excited wave corresponds to the k-vector projection of the driving light.

Abstract: Raman spectroscopic study is carried on the Vickers indented area on the surface of a single crystal silicon carbide (4H- and 6H-SiC) as a nondestructive structure probe to investigate a residual stress and crystal structure. LO phonon frequency shifts and the broad and weak bands around LO phonon band were observed. The residual strain field around the indentation is discussed.

Abstract: Single Shockley faults have been studied in 4H-SiC epitaxial layers by using a spatial resolved micro-photoluminescence technique. In particular the Effect of the UV pumping laser has been investigated. We demonstrated that high power density exposition at 325 nm affects drastically the structural properties of the epitaxial layers leading to a growth of this defect. We also demonstrated that by opportunely tuning the power density of the UV laser on the sample it is possible to analyze a wide area without producing any negative effect.

Abstract: We have detected defects micro-pipes and a cluster of impurities in semi-insulating 6H-SiC substrates using long-wavelength infrared thermal imaging camera (IR-camera) with 8 ~ 14 µm in non-destructive and non-contact. Also we have evaluated the thermal influence of defects on the entire substrates from the observation results of scanning laser microscope (SLM) and light scattering tomography (LST). Through the process, it was certificated that the defects in the substrates could be detected with relatively macroscopic scale (8  6 mm2). Moreover, through a temperature profile processing by a 0.1 K thermal resolution, we estimated thermal behavior of the defect areas in the 6H-SiC precisely. The IR-camera is considered as effective technique for evaluating the defects in the intermediate range between micro and macro scale.

Abstract: We are aiming at understanding the graphene formation mechanism on different SiC polytypes (6H, 4H and 3C) and orientations with the ultimate goal to fabricate large area graphene (up to 2 inch) with controlled number of monolayers and spatial uniformity. To reach the objectives we are using high-temperature atmospheric pressure sublimation process in an inductively heated furnace. The epitaxial graphene is characterized by ARPES, LEEM and Raman spectroscopy. Theoretical studies are employed to get better insight of graphene patterns and stability. Reproducible results of single layer graphene on the Si-face of 6H and 4H-SiC polytypes have been attained. It is demonstrated that thickness uniformity of graphene is very sensitive to the substrate miscut.

Abstract: The paper provides a deeper understanding of key-parameters of epitaxial graphene growth techniques on SiC. At 16000C, the graphene layer is continuous and covers a large area of the substrate. Significant differences in the growth rate could be observed for different reactor pressures and the polarity of SiC substrates as well as for the substrate miscut and surface quality. In addition, graphene thickness uniformity and mechanism of ridges creation was examined.

Abstract: Graphene growth on SiC in atmospheric pressure argon exhibits large terrace sizes and coverage over the entire substrate surface. Graphene growth and the resulting morphology are correlated with the characteristics of the growth chamber and the surface quality of the starting SiC substrate. Without in-situ surface preparation prior to growth, we observe “wrinkles” in the graphene surface. Graphitic-like disordered structures are formed at 1500°C while atomically flat graphene terraces are formed above 1600°C.