Materials Science Forum Vols. 740-742

Abstract: We use three dimensional kinetic Monte Carlo simulations on super-lattices to study the hetero-polytypical growth of cubic silicon carbide polytype (3C-SiC) on misoriented hexagonal (4H and 6H) substrates finding that the growth on misoriented (4°-10° degree off) 6H substrates, with step bunched surfaces, can strongly improve the quality of the cubic epitaxial film promoting 3C single domain growths

Abstract: In this paper we study the influence two different post-growth processes on hetero-epitaxial 3C-SiC on Si substrate for 6 and 8 inches wafers. We studied the influence of wafer cutting process and the substrate partially etching. We find an increase of wafer curvature after each cut processes and every etching processes and a correspondent variation of the Raman shift. These result, confirmed by FEM, can be explained in term of the wafer symmetry breaking and the related relaxation under modified constrains due to the cutting and etching. The FEM analysis of the deformation state reveals a modification of the residual stress tensor which changes from a pure biaxial form to a more complicated one.

Abstract: Silicon nanowires obtained by a top-down approach have been carburized at high temperature and atmospheric pressure with two different gaseous precursors: CH4 and C3H8. These processes reveal core silicon / shell 3C-SiC nanowires. After being characterized by SEM, FIB-SEM and TEM microscopies, the 3C-SiC layer has been used as seed layer for the growth of epitaxial 3C-SiC on the nanowires. Preferential growth of 3C-SiC on the sidewalls of nanowires has been observed. Thanks to the biocompatibility of SiC compared to Si, this layer could act as a protective shell for biosensors based on Si nanowires transistor.

Abstract: In this paper, we review our researches on the high-quality 3C-SiC bulk crystal growth. The polytype control and the suppression of defects are essential in the growth 3C-SiC on hexagonal SiC seed crystals. The growth polytype of SiC is usually controlled by the inheritance of the seed crystal. In contrast, we established kinetic polytype control in which the preferential growth of 3C-SiC can be achieved by the difference in the growth rates depending on supersaturation for the polytypes. In the growth of 3C-SiC, double positioning boundaries (DPBs) are often formed by the existence of twinned domain. The elimination of DPBs can be achieved utilizing the anisotropy of the step advance velocity.

Abstract: High quality bulk-like 3C-SiC were grown on on-axis (0001) 6H-SiC substrate by sublimation epitaxy. The microwave photoconductivity decay mapping measurements revealed that this material shows considerable long carrier lifetimes varied from 3.519 to 7.834 μs under the injection level of 3.5×1012 cm-2, which are comparable with the best carrier lifetimes in 4H-SiC layers. The mapping of high resolution x-ray diffraction obtained from the same region shows that smaller carrier lifetimes seem to correspond to the larger FWHM values and vice versa. This shows that long carrier lifetime obtained in 3C-SiC is due to the improvement of the crystal quality.

Abstract: 3C-SiC epilayers grown on Si-face nominally on-axis 4H-SiC substrate are characterized with X-ray diffraction techniques. The aim was to investigate if these 3C-SiC epilayers were grown by single domain growth. The results show that all samples start by having several nucleation centers all over the substrate surface and the growth continues with two domain formations. As the growth proceeds one domain overtakes the growth and single domain crystal growth occurs. This single domain was further investigated and the results show that it seems to contain many sub-domains with same lattice constant but slightly tilted.

Abstract: Abstract. In this paper, conditions for obtaining high growth rate during epitaxial growth of SiC by vapor-liquid-solid mechanism are investigated. The alloys studied were Ge-Si, Al-Si and Al-Ge-Si with various compositions. Temperature was varied between 1100 and 1300°C and the carbon precursor was either propane or methane. The variation of layers thickness was studied at low and high precursor partial pressure. It was found that growth rates obtained with both methane and propane are rather similar at low precursor partial pressures. However, when using Ge based melts, the use of high propane flux leads to the formation of a SiC crust on top of the liquid, which limits the growth by VLS. But when methane is used, even at extremely high flux (up to 100 sccm), no crust could be detected on top of the liquid while the deposit thickness was still rather small (between 1.12 μm and 1.30 μm). When using Al-Si alloys, no crust was also observed under 100 sccm methane but the thickness was as high as 11.5 µm after 30 min growth. It is proposed that the upper limitation of VLS growth rate depends mainly on C solubility of the liquid phase.

Abstract: In the formation of epitaxial graphene on Si substrates, the growth of high-quality 3C-SiC thin films on Si substrates is a key to success. As a solution to the large mismatch between the Si substrate and the 3C-SiC film, rotated epitaxy in which 3C-SiC(111) films are grown on Si(110) substrates is quite attractive. In some applications, on the other hand, a certatin thickness (~100 nm or more) is required for this 3C-SiC films as well. A two-step growth method has been thus developed to realize a high-rate, qualified rotated epitaxy. A qualified graphene is found to be formed on this rotated epi-film, as typified by the increase of the grain size by a factor of 1.6 from the non-rotated epitaxy.

Abstract: This work deals with the study of the Selective Epitaxial Growth (SEG) of SiC using the Vapour-Liquid-Solid (VLS) transport on diamond (100) substrate with Al-Si as the liquid phase fed by propane. Morphology, structure and doping type of the SiC deposit were determined. Polycrystalline p-doped 3C-SiC was obtained during the growth. Study of the initial step of growth showed that SiC nucleation occurs without any propane addition but just through the interaction of liquid Al-Si and diamond via a dissolution/precipitation process. This explains the random nucleation and the polycrystalline growth. Despite this, preliminary electrical measurements show encouraging results.

Abstract: The 3C-SiC layers on nominally on-axis 6H-SiC substrates were grown using sublimation epitaxy. More than 90% coverage by 3C-SiC is typically achieved at growth temperature of 1775°C. The main reason for the polytype inclusions to appear is local supersaturation non-uniformities over the sample surface which appear due to the temperature gradient and spiral growth nature of 6H-SiC. On the 6H-SiC spirals with small steps supersaturation is smaller and 3C-SiC nucleation and growth is diminished. Due to surface free energy and surface diffusion differences, polytype inclusions appear differently when 3C-SiC is grown on the Si- and C-faces. The 6H-SiC inclusions as well as twin boundaries act as neutral scattering centers and lower charge carrier mobility.