Study On Grade Base Of 4H-SiC BJT Characteristics

In this thesis, the characteristics of 4H-SiC Bipolar Junctiom Transistor(BJT) with different structure are studied by the device simulation. A physical model that can well describe the experiment results was developed. With Gaussian-doped base region AC and DC simulation results are improved and current gain is increased from 16.65 to 44.49 comparing with base constant-doped, and also some parameters such as turn-on voltage, output resistance and Early voltage have a certain degree improved. The 4H-SiC BJT with epitaxial three-layer base is analyzed and it is found that multi-base epitaxial structure can effectively improve the current and frequency characteristics. The process for the device is free of ion implantation and high-temperature annealing process, so that it will greatly reduce the SiC crystal lattice damage of the surface and improve the quality of passivation layer between base and emitter, thereby enhance the current gain.The main work of this thesis is to simulate characteristics of grade base 4H-SiC BJT's, and it has the important significance for the development of SiC power devices..