And this agrees with the results of the diffraction contrast study.Ĭross-sectional low magnification TEM image and the SAED patterns of Si films grown on 6H-SiC (0001) at 900☌. Furthermore, the faint diffused streaks along the orientation indicate that there exist a large number of SFs. A superposition of two FCC zone diffraction patterns, which are symmetrical to each other with respect to the (111) mirror plane, indicating that the lamellar structure observed in the film consists of alternate stacks of twins, as shown in Figure 2(b). It should be pointed out that the extinction diffraction spots of (10-10) SiC and (10-16) SiC can be observed in the SAED patterns because of the multiple diffraction. Alignment of the diffraction spots indicates that FFC-on-HCP epitaxial orientation, i.e., (111) Si//(0001) 6H-SiC is maintained at a growth temperature of 900☌. It is confirmed that the Si film has epitaxial connection with the 6H-SiC substrate and the orientation relationship of Si/6H-SiC heterostructure is (111) Si//(0001) 6H-SiC. The selected area electron diffraction (SAED) patterns of the Si/6H-SiC heterostructure corresponding to SiSiC zone axes are shown in Figure 2(b). The Si film with a thickness of about 0.55 μm shows irregular heterogeneous diffraction contrast, which suggests the existence of some structural defects such as stacking faults (SF) and twins in the film, as labeled in Figure 2(a). In this image, the lower part belongs to the 6H-SiC substrate, while the upper part represents the Si thin film. The low magnification cross-sectional transmission electron microscopy (TEM) bright-field image of the Si thin film grown on 6H-SiC(0001) at 900☌ is shown in Figure 2(a). Interface micro-structure of the Si/SiC heterostructure During domain matching system, the domain size nɑ sic of the SiC substrate does not match perfectly with mɑ Si of the Si film and thus a residual domain mismatch strain is present in the film in the x direction, given byĢ.2. In the Si/6H-SiC system, domains consisting of m lattice constants of the Si film match with n of the SiC substrate. And this matching mode is applicable for the heterostructures with similar crystal symmetry on the film and the substrate. A schematic illustration of mechanisms for accommodation of lattice mismatch strain in large-mismatch systems with domain epitaxial growth is shown in Figure 1. However, the Si/SiC heterostructure has a large lattice mismatch, the epitaxial growth is still followed except that domain matching (DM) mode in order to reduce the mismatch, and therefore an interfacial MD array is present at the interface that determines the domain’s size. If the lattice mismatch of the heterostructure is sufficiently low, the mismatch strain can be released by interfacial atomic relaxation of the heterostructure, and the strained-layer heterostructure with no interfacial misfit dislocations (MD) will be attained. Where ɑ sic(0001) and ɑ Si(111) are the lattice constants of the SiC(0001) and Si(111) crystalline planes, respectively. At present, the studies of the SiC-based Si/SiC heterostructure just focused on the electrical performance of the heterostructures in SiC SBD and SiC MOSFET, the growth mode and interface-structure of the Si/SiC heterostructure is rarely reported. By observation of the Si/SiC interface-structure with different growth temperatures, the growth mode of the Si/SiC heterostructure can be revealed, and the accurate control of the growth orientation may be achieved. The interface-structure of the heterostructure determines some important parameters such as the preferential orientation, the interface state density and the carrier mobility, which have significant impact on the heterostructure device performance. In our previous work, it was found that the Si films on SiC substrates always have a polycrystalline structure with multiple orientations, while the preferential growth of the Si films with different orientations can be obtained at different growth temperature. Si/SiC heterostructure is suggested to make SiC-based devices to be light-activated by non-UV light, in which Si is used as a non-UV light absorption layer. However, due to the wide bandgap, SiC-based photoelectric devices can be only driven by ultraviolet (UV) light, which essentially limits the application of visible and infrared light detection. With advantageous material properties such as a wide bandgap and high thermal conductivity, silicon carbide (SiC) has attracted much attention for its wide applications in the photoelectric devices of high temperature and high power.
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