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In this study, the electrical properties of Ti3SiC2 based ohmic contacts formed on p-type 4H-SiC(0001) 4°-off substrates were studied. The Ti3SiC2 thin films were grown by thermal annealing (from 900°C to 1200°C) of Ti50Al50 layer deposited by magnetron sputtering. XRD analyzes were performed on the samples to further investigate the compounds formed after annealing. Using TLM structures, the Specific Contact Resistance (SCR) at room temperature of all contacts was measured. The temperature dependence (up to 600°C) of the SCR was studied to understand the current mechanisms at the interface and to determine the barrier height value by fitting the experimental results using the thermionic field emission theory. Aging tests showed that Ti3SiC2 based contacts were stable up to 200h at 600°C under Ar.

In order to form Ti3SiC2 on 4H-SiC(0001) 8°-off, 200 nm of Ti30Al70 was deposited onto SiC substrates by magnetron sputtering from pure Ti30Al70 targets. The samples were then annealed at 1000°C for 10 min under Ar atmosphere in a Rapid Thermal Annealing (RTA) furnace. Structural analyses reveal the formation of epitaxial hexagonal Ti3SiC2 (0001) oriented. Elemental analyses show that high amount of Al and O elements are present inside the deposit. Obviously, the formation of Ti3SiC2 is accompanied by parasitic Al oxide, probably due to some unwanted oxygen residual in the RTA chamber. By using proper backing steps before the annealing, the deposit is not anymore composed of only Ti3SiC2 but accompanied with other compounds (Al3Ti, and Al). On the oxide-free sample, the specific contact resistance ρc of the Ti3SiC2 based contact on p-type 4H-SiC (having Na= 2×1019 cm-3) was measured to be as low as 6×10-5 Ω.cm2.

In this work the capability of the proton induced X-ray emission (PIXE) technique to monitor a rapid, non-destructive and accurate quantification of Al on and in Si-based matrix is discussed. Optimization of PIXE acquisition parameters was performed using as reference a thin Al film (2.5 nm) thermally evaporated onto silicon substrate. In order to improve the sensitivity for Al detection and quantitative determination, a systematic study was undertaken using proton ion beam at different energies (from 0.3 to 3 MeV) with a different tilting angle (0°, 60°, and 80°). The limit of detection (LOD) was found to be lower than 0.2 nm. The optimum PIXE conditions (energy, angle) were applied for determining the Al doping concentration in thin (1 µm) 4H-SiC homoepitaxial layer. The Al concentration as determined by PIXE was found to be 3.9x1020 at/cm3 in good agreement with SIMS measurements, and the LOD was estimated to be 6x1018 at/cm3.

This paper deals with the formation and propagation of twin boundaries (TBs) inside 3C-SiC layers grown heteroepitaxially on -SiC substrate. The equivalent probability of nucleating 60° rotated 3C islands on such substrate lead to the systematic formation of TB upon coalescence of these islands. Elimination of these defects should occur by bending of the propagation direction. Bending through incoherent TBs is usually encountered during both VLS and CVD growth and it generates crystalline defects due to high built-in energy. One would prefer coherent TBs, formed by two-by-two annihilation of neighbouring TBs, which do not form new defect except microtwin inclusion at the interface. Such TB annihilation seems to be a specificity of growth by VLS mechanism. The mechanism of such bending is discussed

International audience; Complementary lateral structures, N-JFETs. P-JFETS and bipolar diodes, have been implemented in p and n-type 4H-SiC wafers with epilayers. The device were optimized using finite element code MEDICI (TM) simulations, based oil ion implanted and etched Reduced-Surface-Field structures. Two Ti/Ni alloy composition are found to form ohmic contacts compatibles with high temperature device operation. 900 degrees C and respectively 1000 degrees C post-metallisation annealing during 2min are necessary. The presence of a graphite layer is determined by XPS (X-ray photon spectroscopy) analyses at the metal-semiconductor interface. Oil the fabricated p and n-type lateral JFETs in blocking state, breakdown voltage as high as 600V are obtained.

International audience; We report an optical study of 3C-SiC layers grown on 6H-SiC substrates by VLS mechanism using a Si-Ge melt. The photoluminescence and μ-Raman results show a clear and significant incorporation of germanium in the layers from the melt. A photoluminescence emission attributed to Ge related transitions is observed in the infrared region. μ-Raman spectra exhibit two peaks related to the Ge-Ge and Si-Ge bonds. From the characteristics of these Raman peaks, it was found that the amount of Ge incorporated inside the 3C layers increases with increasing Ge content of the melt. This has been verified by Particle-Induced X-rays Emission (PIXE) measurements which gave a Ge concentration varying from ~ 1x1019 to ~ 1x1020 at.cm-3. All these results suggest that Ge incorporates in the VLS grown 3C layers by forming Si-Ge-(C) nanoclusters.

The aim of the present work is to study the structural properties of 3C-SiC which is grown on (0001) 6H-SiC and on (100) 3C-SiC (Hoya) seeds using the Continuous Feed Physical Vapor Transport (CF-PVT) method. Transmission Electron Microscopy (TEM) observations confirm that the overgrown layer is of the 3C-SiC polytype. In the case of the 6H-SiC substrate, microtwins (MTs), stacking faults (SFs) and dislocations (D) are observed at the substrate-overgrown interface with most of the dislocations annihilating within the first few µm from the interface. In the case of 3C-SiC crystals grown on 3C seeds, repeated SFs are formed locally and also coherent (111) twins of 3C-SiC are frequently observed near the surface. The SF density is reduced at the uppermost part of the grown material.

Twin-free 3C-SiC layers were recently obtained by Vapour-Liquid-Solid mechanism on a a-SiC(0001) substrate using Si-Ge melt. The formation of cubic layers is rather unexpected since growth from the melt is known to promote lateral growth and should thus give homoepitaxial layers. The study of the early stage of such growth, after a simple contact between the melt and the substrate (without adding propane), reveals the precipitation of 3C-SiC elongated islands upon the substrate surface. The chemical interactions inside the Ge-Si-C ternary phase diagram suggest an initial dissolution of the SiC seed in contact with a Ge-rich melt (below 1200°C). When the Si content of the melt subsequently increases upon heating, the dissolved carbon atoms precipitate on the seed surface under the form of 3C-SiC islands. When propane is added, these islands enlarge and coalesce to form a complete 3C layer.

The growth kinetics of 3C-SiC heteroepitaxial layers on α-SiC substrates by Vapour-Liquid-Solid (VLS) mechanism in Ge-Si melts was investigated. Various parameters were studied such as temperature, melt composition, propane flux and substrate nature (polytype, polarity and misorientation). It was found that the growth rate increases with increasing temperature, propane flux, Si content of the melt and misorientation of the substrate. The calculated activation energy (from 4.7 to 6.6 kcal/mole depending on the substrate type) is very small suggesting that the limiting process is the diffusion of the dissolved carbon inside the melt. The carbon solubility inside the melt mainly affects the carbon dissolution kinetics from the gas phase. The results also suggest that surface effects are important through the layer polarity and crystalline quality.

We report on the heteroepitaxial growth of 3C-SiC layers by Vapor-Liquid-Solid (VLS) mechanism on various α-SiC substrates, namely on- and off-axis for both 4H and 6H-SiC(0001), Si and C faces. The Si-Ge melts, which Si content was varied from 25 to 50 at%, were fed by 3 sccm of propane. The growth temperature was varied from 1200 to 1600°C. It was found that singledomain 3C-SiC layers can be obtained on 6H-SiC off and on-axis and 4H-SiC on-axis, while the other types of substrate gave twinned 3C-SiC material. As a general rule, one has to increase temperature when decreasing the Si content of the melt in order to avoid DPB formation. It was also found that twinned 3C-SiC layers form at low temperature while homoepitaxy is achieved at high temperature.

We applied picosecond dynamic grating technique for studies of carrier dynamics in ntype DPB(double positioning boundary)-free 3C-SiC (111) epilayer grown by VLS (vapour-liquidsolid) mechanism on 6H-SiC (0001). The measurements of bipolar diffusion coefficient D and carrier lifetime τR in the samples at various pump energies (0.5 – 3.0 mJ/cm2) and temperatures (9 – 300 K) provided the values of bipolar mobility of ~ 80 cm2/Vs and τR = 1.5 - 2.0 ns at 300 K. The ionized impurity scattering, dominant at T < 100 K, and carrier-density dependent lifetimes in 10- 300 K range were attributed to contribution of trapping centers which electrical activity saturates at high carrier density.

Vapor-Liquid-Solid was used for growing boron doped homoepitaxial SiC layers on 4HSiC( 0001) 8°off substrates. Si-based melts were fed by propane (5 sccm) in the temperature range 1450-1500°C. Two main approaches were studied to incorporate boron during growth : 1) adding elemental B in the initial melt, with two different compositions : Si90B10 and Si27Ge68B5; the growth was performed at 1500°C; 2) adding B2H6 (1 to 5 sccm) to the gas phase during growth with a melt composition of Si25Ge75; the growth was performed at 1450°C. In most cases, the growth time was limited by liquid loss due to wetting on the crucible walls. The longer growth duration (1h) was obtained when adding B2H6 to the gas phase. In the case of Si90B10 melt, the surface morphology exhibits large and parallel terraces whereas the step front is more undulated when adding Ge. Raman and photoluminescence characterizations performed on these layers confirmed the 4H polytype of the layers in addition to the presence of B which results in a strong B-N donor-acceptor band. Particle induced γ-ray emission was also used to detect B incorporation inside the grown layers.

We report an optical investigation of cubic Silicon Carbide (3C-SiC) layers grown on 6H-SiC substrates by Chemical Vapour Deposition and Vapour-Liquid-Solid mechanism. Micro- Infrared reflectance ('-IR), micro-Raman ('-Raman) and low temperature photoluminescence spectroscopies were used for the characterisation of such layers. '-IR measurements showed unusual optical behaviour of 3C-SiC layers. The difference of refraction index between the 3C-SiC film and the 6H-SiC substrate cannot explain this result. The experimental '-IR reflectance spectrum was modelled by introducing a thin (thickness ≤ 0.5 'm) metallic-like (doping ≥ 1020 at.cm-3) interfacial film between the layer and the substrate. The photoluminescence spectra revealed the presence of a peak which may be attributed to recombination at the 3C/6H interface. All these results suggest the presence of a two dimensional electron gas at the interface.

Growing good quality SiC epitaxial layers at temperature lower than 1400°C is a challenging problem which could help reducing the costs, increasing the safety of the process or even give new perspectives. Toward this aim, liquid based growth techniques have been used. The Si-based melts should be carefully chosen considering several criteria. Furthermore, the implementation of a liquid phase for growing SiC epilayer can be performed in various manners (dipping or VLS mechanism) so that one has to choose the more appropriate technique. The discussion is illustrated with several results showing that the growth of SiC from a liquid phase at low temperature can address various important technological points such as experimental safety, ptype doping, on-axis or selective epitaxy. The recent demonstration of single-domain 3C-SiC heteroepitaxial layers on hexagonal SiC substrates confirms that liquid based growth has still unexpected qualities.

This paper studies the electronic properties of MOS capacitors fabricated on double positioning boundary free 3C-SiC/6H-SiC where the 3C-SiC films were grown using the Vapour- Liquid-Solid mechanism. The temperature- and frequency-dependent electrical properties of SiO2/3C-SiC/6H-SiC structures have been studied. Capacitance measurements indicate that the single-domain 3C-SiC film is doped near the surface with an average concentration of 8.3 × 1016 cm-3. The measured interface state density near the conduction band edge of 3C-SiC is below 1011cm-2⋅eV-1 and increases towards mid-gap as obtained from conductance and capacitance measurements. Our results are consistent with the assumption that the interfaces of SiO2/ n-type SiC consist of two different kinds of interface traps – the carbon clusters located at the interface and the intrinsic defects located within the oxide layer.

The vapour-Liquid-Solid mechanism was used for growing epitaxial SiC layers on onaxis 6H-SiC and 4H-SiC substrates. By feeding Al70Si30 melts with propane, homoepitaxial growth was demonstrated down to 1100°C on both polytypes. At this temperature, the surface morphology is rough and non uniform with spiral growth forming large hillocks at the places where screw dislocations emerge from the substrate. Raman spectroscopy confirms the absence of the 3C-SiC polytype and shows the high Al doping of the layers. This growth temperature of 1100°C is the lowest one ever reported for growing homoepitaxial layers on low tilt angle SiC substrates. Increasing the temperature to 1200°C eliminates these hillocks but creates other morphological features due to fast substrate etching at this high temperature before growth starts.