Simulation Study Of 4H-SiC Metal-Semiconductor Bipolar Junction Transistors

Silicon Carbide(SiC)has wide applications in high temperature, high frequency and high radiation environment because of its superior properties, primarily its wide band gap, high critical breakdown field, excellent thermal conductivity and high electron saturation drift velocity. Recent years, bipolar devices based on SiC have received increasing attention. Based on the superior properties of 4H-SiC and the basic structure of NPN Bipolar Junction Transistors(BJTs),a new Metal-Semiconductor BJTs(MSBJTs)is proposed, and its basic characteristics are analyzed with numerical simulation.The current transport theory of p-type Schottky contact is analyzed, and the forward I-V characteristics of two different metal Schottky barrier diodes are simulated, which lay the foundation for the research of MSBJT.The structure and physical models applicable to the DC analysis of 4H-SiC MSBJT are established to simulate the DC characteristics. The model proposed above accurately describes the operational characteristics of the device. Simulation result shows that the device has excellent DC properties characteristics with the common-emitter current gainβup to 50. Based on the analysis above, the key factors to influence the current gain are investigated, including Metal-Semiconductor interface states and the width of base. From the simulation results in high temperature, its ability of operating above 300℃is proved. The degradation of performance with increased time is also introduced and a simple theory can be used to explain the effect of stacking defects on the gain.The AC small signal characteristics are analyzed by using two-port analyzer and parameters. The transit frequency and maximum oscillation frequency are also extracted.In this thesis, study of the 4H-SiC MSBJT characteristics with numerical simulation has been done, which provides the theoretical base for further works.