[en] Graphene growth from a propane flow in a hydrogen environment (propane-hydrogen chemical vapor deposition (CVD)) on SiC differentiates from other growth methods in that it offers the possibility to obtain various graphene structures on the Si-face depending on growth conditions. The different structures include the (6√3 × 6√3)-R30° reconstruction of the graphene/SiC interface, which is commonly observed on the Si-face, but also the rotational disorder which is generally observed on the C-face. In this work, growth mechanisms leading to the formation of the different structures are studied and discussed. For that purpose, we have grown graphene on SiC(0001) (Si-face) using propane-hydrogen CVD at various pressure and temperature and studied these samples extensively by means of low energy electron diffraction and atomic force microscopy. Pressure and temperature conditions leading to the formation of the different structures are identified and plotted in a pressure-temperature diagram. This diagram, together with other characterizations (X-ray photoemission and scanning tunneling microscopy), is the basis of further discussions on the carbon supply mechanisms and on the kinetics effects. The entire work underlines the important role of hydrogen during growth and its effects on the final graphene structure.

[en] We propose to grow graphene on SiC by a direct carbon feeding through propane flow in a chemical vapor deposition reactor. X-ray photoemission and low energy electron diffraction show that propane allows to grow few-layer graphene (FLG) on 6H-SiC(0001). Surprisingly, FLG grown on (0001) face presents a rotational disorder similar to that observed for FLG obtained by annealing on (000-1) face. Thanks to a reduced growth temperature with respect to the classical SiC annealing method, we have also grown FLG/3C-SiC/Si(111) in a single growth sequence. This opens the way for large-scale production of graphene-based devices on silicon substrate.

[en] In this study we determine by means of Fourier transform infrared spectroscopy the doping level of n-type doped 3C-SiC and GaN epilayers grown, respectively, on silicon and sapphire substrates. We show that a doping level can be established for both cases with a high accuracy by identifying relevant spectral features and by performing a simple analytical simulation. We discuss in what extent the spectral features which are used to determine the doping level can be attributed to the LO phonon-plasmon modes (LPP modes) for both cases. The influence of the substrate is also discussed. Complementary measurements performed by secondary ion mass spectroscopy (SIMS) attest the reliability of the method.

[en] Graphical abstract: - Highlights: • Processing and electrical characterization of MOS capacitors fabricated on 4H-SiC epilayers grown on 2°-off axis heavily doped substrates. • Excellent characteristics of the SiO_2/4H-SiC interface in terms of flatness, interface state density and oxide reliability. • Electrical behavior of the MOS devices comparable with that obtained for the state-of-the-art of 4°-off axis 4H-SiC material. • Demonstration of the maturity of the 2°-off axis material for application in 4H-SiC MOSFET device technology. - Abstract: In this paper, the electrical properties of the SiO_2/SiC interface on silicon carbide (4H-SiC) epilayers grown on 2°-off axis substrates were studied. After epilayer growth, chemical mechanical polishing (CMP) allowed to obtain an atomically flat surface with a roughness of 0.14 nm. Metal-oxide-semiconductor (MOS) capacitors, fabricated on this surface, showed an interface state density of ∼1 × 10"1"2 eV"−"1 cm"−"2 below the conduction band, a value which is comparable to the standard 4°-off-axis material commonly used for 4H-SiC MOS-based device fabrication. Moreover, the Fowler–Nordheim and time-zero-dielectric breakdown analyses confirmed an almost ideal behavior of the interface. The results demonstrate the maturity of the 2°-off axis material for 4H-SiC MOSFET device fabrication.

[en] Various aspects of the elaboration of (1 1 1) oriented 3C-SiC films on silicon are discussed within a comparative study of different layer characteristics for (1 1 1) and (1 0 0) orientations. The dissimilarities between both orientations are pointed out. This includes the growth mode during the nucleation, the efficacy of defect healing during the growth, the dopant incorporation and the warping of the epiwafer. The results of 3C-SiC surface preparation by chemical mechanical polishing are also demonstrated. All the characteristics of (1 1 1) oriented layers are discussed from the point of view of the application of 3C-SiC/Si epiwafers as templates for nitride growth. The characteristics of AlGaN/GaN based high electron mobility transistor elaborated on 3C-SiC/Si template are presented to validate the template's concept.

[en] The value of the full width at half maximum of the rocking curve of symmetric 3C SiC reflection, often considered as the ''quality indicator'' of the epitaxial film, is in fact a convolution of several contributions, among which the curvature related part may play a dominant role. Thus, a precise determination of the curvature related broadening is necessary to extract the information on the film quality from the rocking curve. In this paper we demonstrate experimentally the coexistence of two independent curvature related broadening effects. We also propose an analytical model that describes quantitatively both effects.

[en] In this work we investigated the influence of the Si substrate misorientation and 3C-SiC film thickness on the density of Anti-Phase Boundaries, in order to better understand the mechanism of antiphase domain annihilation. The two highlights in our work are the utilization of [001] orientated Si on-axis wafer with spherical dimples, which gave us access to a continuum of off-cut angles (0 deg. to ∼11 deg.) and directions, and the deposition of elongated silicon islands on the surface of 3C-SiC epilayers, which improved the detection of APDs by analysis of Scanning Electron Microscopy images. We found that for a given layer thickness the relative surface occupation of one domain increases with the off-cut angle value, leading to single domain film up to a certain angle. This critical value is reduced as the film is thickened.

[en] Cantilevers with resonance frequency ranging from 1 MHz to 100 MHz have been developed for dynamic atomic force microscopy. These sensors are fabricated from 3C-SiC epilayers grown on Si(100) substrates by low pressure chemical vapor deposition. They use an on-chip method both for driving and sensing the displacement of the cantilever. A first gold metallic loop deposited on top of the cantilever is used to drive its oscillation by electrothermal actuation. The sensing of this oscillation is performed by monitoring the resistance of a second Au loop. This metallic piezoresistive detection method has distinct advantages relative to more common semiconductor-based schemes. The optimization, design, fabrication, and characteristics of these cantilevers are discussed

[en] Highlights: → N, P and N and P co-implantation in 3C-SiC. → Closed to 100% of activation for N implanted/annealed sample at 1400 ^oC. → Low surface roughness (<5 nm) after annealing by using carbon protective layer. → Ultra-low SCR (2.6 x 10^-6 Ω cm²) with Ti/Ni contact on N implanted/annealed sample. - Abstract: In this work, non-intentionally doped cubic silicon carbide (3C-SiC) epilayers grown on (1 0 0) silicon substrates were implanted using nitrogen (N), phosphorus (P) implantations or their co-implantation (N and P). After annealing from 1150 to 1400 ^oC, Secondary Ion Mass Spectroscopy (SIMS), Atomic Force Microscopy (AFM), Fourier Transformed InfraRed spectroscopy (FTIR), Scanning Spreading Resistance Microscopy (SSRM) and Scanning Transmission Electron Microscopy (STEM) analysis were performed. Specific contact resistances (ρ_c) of Ti/Ni ohmic contacts were determined using Circular Transfer Length Method (c-TLM) patterns. Our work shows that co-implantation, experimentally investigated for the first time in 3C-SiC, is not beneficial for the doping efficiency. According to the silicon substrate, the post-implantation annealing is limited to 1400 ^oC. Consecutively to this limit, the total recovering of the lattice does not seem to be possible, whatever are the implanted species. Moreover, as the crystal damages increase when increasing the atomic mass of the implanted species, a comparative study using SSRM measurements proved that, for the same post-implantation annealing treatment, the resistivity of implanted layers depend on the doping species. As a consequence, the lowest ρ_c value (2.8 x 10^-6 Ω cm²) has been obtained (using Ti/Ni 25/100 nm pattern) for a 1400 ^oC-30 min annealing consecutively to the nitrogen implantation. This value is among the best values obtained on implanted 3C-SiC layers in the literature. Furthermore, for this annealing temperature, a doping activation close to 100% has been evaluated by quantitative SSRM technique which evidences that an efficient dopant activation could be done. The high activation rate obtained on n-type implanted 3C-SiC and the low specific contact resistance achieved with Ti/Ni are very promising for electronic device fabrication.

[en] For electronic devices, good ohmic contacts are required. To achieve such contacts, the semiconductor layer has to be highly doped. The only method available to locally dope the SiC is to implant dopants in the epilayer through a mask. In this work, non-intentionally doped 3C-SiC epilayers were implanted using nitrogen or phosphorus at different energies and subsequently annealed at temperatures between 1150 deg. C and 1350 deg. C in order to form n⁺ implanted layers. Different techniques such as Fourier Transformed InfraRed spectroscopy (FTIR), Secondary Ion Mass Spectroscopy (SIMS) and Transmission Electron Microscopy (TEM) were used to characterize implanted 3C-SiC epilayers subsequently to the different annealing steps. Then, Ti-Ni contacts were carried out and the specific contact resistance (ρ_C) was determined by using circular Transfer Length Method (c-TLM) patterns. ρ_C values were investigated as a function of implanted species and contact annealing conditions, and compared to those obtained for highly doped 3C-SiC epilayers. As expected, ρ_C value is highly sensitive to post-implantation annealing. This work demonstrates that low resistance values can be achieved using nitrogen or phosphorus implantation at room temperature hence enabling device processing.