Analysis of Reflection High Energy Electron Diffraction Pattern of Silicon Carbide Grown on Silicon

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RESULTS AND DISCUSSION Epitaxial alinment and twinning in the system 3C-SiC on Si The cubic form of silicon carbide (3C-SiC) crystallize in the zincblende structure with a lattice constant of 0.436 rn. The space group is FV43m. Corresponding to the crystal structures of 3C-SiC and Si and the types of bonding the following relationships were found [3]: 3C-SiC{ 100}//Si{ 100} with 3C-SiC//Si and 3C-SiC{ 111 }//Si{ 111 } with 3C-SiC

  • //Si. In our growth experiments these alignments were characteristic for medium C3H 8 concentrations and independent on temperature. In the case of higher saturation thicknesses, i.e. CC3H < 0.1%, we found more complicated diffraction pattern. A characteristic set of diffraction pattern obtained from SiC layers on (11 )Si and their indexing is shown in Fig.1 and Fig.2. The diffraction pattern shown in Fig.la and 2a can be explained by the existence of3C-SiC//Si twin orientation. In the case of Fig.lb and 2b additional 3C-SiC//Si twins are evident. The AFM analysis of the samples with reflection twins shows triangular crystallites, which were rotated around 600 or 1800 typical for twinning (Fig.3). The density of the rotated crystallites is smaller than for the nonrotated ones. This agrees with the smaller intensity of the twinning spots in the corresponding diffraction pattern (Fig. Ia).

    Fig.1 RHEED pattern obtained from carbonized (11 )Si: (a) (11 1)SiC twin, twinning plane (111); (b) twin planes (111) and (111); (c) twinned (11 )SiC and (110) oriented crystals < I I>,

    c

    b

    a

    ,tw, tw

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    0 0 0 a 0 o

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    •,twin reflection

    double reflectlon

    * (III)SIC 0

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    ((111)SIC

    11 0 (110)SIC

    twin reflectlon

    Fig.2 Corresponding schematical indexed RHEED pattern: (a) (11 )SiC twin, twin plane (111); (b) twin planes (111) and (1 iT); (c) twinned (11 1)SiC and (110) oriented crystals

    18

    At high heating-up ramps and CC3H8 < 0.02% we observed a polycrystalline fraction and the occur-

    600 "M23

    rence of additional orientations. The most pronounced was the growth direction of the up to now not observed on (111I)Si (Fig. Ic and

    300 ,mSiC

    2c). In the case of carbonized (100)Si substrates additionally to the expected (100)SiC//(100)Si relationship three characteristic diffraction pattern 0,nm 0Onm were observed and indexed (Fig.4 and 5). The first 3a0 am 600 nm Q type corresponds to SiC//SiC twins Fig.3 AFM picture of a surface with reflec- (Fig.4a and 5a). Double reflection was also observed (Fig.5a). On the second type of RHEED pattion twins tern diffraction spots appear which indicates an unusual SiC crystallite orientation (Fig4b and 5b). The evidence of the SiC orientation but not the expected SiC one was confirmed by x-ray diffraction. It can be shown that the relationship (31 1)SiC//(100)Si with SiC//Si gives a better lattice match (18%).

    Fig.4 RHEED pattern obtained from carbonized (100)Si: (a) (100)SiC with twins SiC// Si with a weak amoun