Research Of Threading Edge Dislocations (TED) In 4H-SiC Materials

Silicon Carbide (SiC) which has outstanding properties such as wide bandgap, high critical breakdown field, higher thermal conductivity and high electron saturation drift velocity is particularly suitable for fabrication of devices operated in high temperature, high voltage, high power and high radiation environment. With excellent figure of merits, 4H-SiC is received more attention than other SiC materials. However,there are still lots of defects in 4H-SiC which can affect the performance of devices.The research of basic characteristics about defects is helpful to understand the mechanism of its impact on devices and make theoretical preparation for high-quality 4H-SiC epitaxial growth and devices'performance improvement.First principle which is based on density funtional theory is one important way to obtain electronic properties of materials. It has been often applied on research of point defects while less on dislocations.In this paper, the electronic sturctrue of threading edge dislocations(TED)is studied by first principle.The main contributions are as follows:First, TED'model in 4H-SiC is established by drawing out selected atoms and then reconstucting lattice in perfect lattice,based on the generation characteristics of TED. Secondly,the distortion of lattice caused by dislocations is discussed to get dislocation width which means the size of serious distortion area.In view of the calculation time,dislocation width and some other factors,the size of model is detemined.Finally,the properties of TED is analyzed in CASTEP.It is found that the bottom of conduction band and the top of valence band are both changed and new defect levels are present which make thinly states distribution in band gap which due to the existence of dangling bonds and lattice distortion.In addition,the fermi level moves to conduction band which indicates that TED dislocation perform as donor.