Defects carbide substrate

This general scheme of surface nucleation processes, as described above, may be adequate only for nucleation on a perfect substrate. It is well known that in many important practical situations, nucleation occurs at defect sites on the substrate surface. In addition, the interactions of gas-phase species with the substrate surfece in diamond CVD may lead to surface carbon atoms of different chemical bonding states and structures, for example, sp, sp, or sp bonded carbon, amorphous carbon, diamond-like carbon or carbon in carbides. These factors further increase the difficulty in understanding surface nucleation processes of diamond in CVD. 

Nonetheless, owing to its temperature stability, dopabUity and widely tunable optical behavior, amorphous SiC doped with hydrogen (a-SiC H) has been investigated for its application in photovoltaic devices. One of several structural renderings of amorphous SiC is shown in Figure 11.9. In this case, the refractive index can be varied from 2.3 to 3.7, and the band gap from 2.4 to 2.0eV, simply by altering a few parameters of the plasma-enhanced CVD technique that is used to deposit an amorphous silicon carbide layer with low defect density onto, for example, a substrate of RSiC. Attention has also been focused on the surface passivation performance of layers deposited on crystalline siUcon. Indeed,... 

Sihcon carbide crystals are important substrates for gallium nitride epilayer for blue-hght optoemission. Defect images of both substrate and epilayer are shown Fig. 13.12. Such images can be used to optimize the growth process and significantly reduce defect densities. 

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