Study On The Feasibility Of SiC Based Light-controlled Devices

Applications of SiC in optoelectronics are restricted in the range from visible to near-infrared due to its wide bandgap. However, it may come true via depositing semiconductor materials, which are sensitive to visible or near-infrared light, on SiC substrates to prepare SiC devices with a heterojunction structure.Epitaxial materials, being sensitive to the light, are analyzed for preparing SiC heterojunction on SiC substrates. Silicon, as an epitaxial material, is selected to form Si/SiC heterojunction optoelectronic diode. Then the effects of interface states and defects in the epilayer on the diode are presented in this paper. The main disadvantage for epitaxial materials on SiC is the large mismatch, which will introduce many defects such as mismatch dislocation. On the other hand, there will be a number of interface states in the heterojunction, which may restrict preparation of SiC light-controlled devices.Some conclusions are obtained as follows:1. Generally speaking, there exists a large lattice mismatch between SiC and its epitaxial materials, which are sensitive to visible or near-infrared light, instead of the little mismatch ones. So we should split the difference between light absorbability and lattice mismatch in materials.2. Both defects in epilayer and interface states in heterojunction have detrimental effects on heterojunction optoelectronic characteristic. When number of defects in epilayer is large enough to make reverse leakage current the same magnitude as photocurrent, the optoelectronic diodes will be unworkable.3. According to different applied fields of SiC light-controlled devices, it is needed to think over the characteristics of related epitaxial materials to realize reliable applications of these devices.The characteristics of materials and their corresponding devices are analyzed in this dissertation. It is believed that we can realize feasibility of making SiC light-controlled devices applied in the range from visible to near-infrared, only if the epilayer quality is high enough.