4H-silicon carbide power bipolar junction transistors

Silicon Carbide (SiC) has generated a lot of interest and research work in recent years because of its superior material properties suitable for high power and high temperature applications. Among the high power devices, bipolar junction transistors (BJTs) have been a subject of more and more study, since power BJTs based on 4H-SiC could eliminate the fatal drawbacks of Si based power BJT and are capable of handling high power with much greater current gain.; In this study, the design, fabrication and testing of 4H-SiC power BJT has been investigated. The first 4H-SiC power BJT has been demonstrated. Since BJT is a current-control device, it is very important to achieve high current gain at high blocking voltage in order to simplify the base drive circuit. The device design, processing procedure were optimized to achieve 4H-SiC power BJT capable of handling high power and having high current gain. The effects of the spacing between the emitter mesa edge and the base contact implantation edge, base contact implantation doses and energies, base contact metal schemes, and thermal oxidation annealing schemes on current gain and blocking voltage were investigated. Optimized 4H-SiC power BJT capable of blocking more than 1000V with a common emitter current gain of 32 was fabricated and tested, which was the state-of-the-art performance in power 4H-SiC BJTs. A packaged power BJT at 588V-31A rating with a common emitter current gain of 29 was achieved.; Darlington transistor is a configuration that can boost current gain tremendously in conventional Si power BJT. Hybrid 4H-SiC Darlington transistors were investigated by connecting optimized power BJTs into Darlington transistors. The effect of the area ratio of the output transistor to the driving transistor was studied and optimum area ratio in the range of 1--8 was found. Darlington transistor at power rating of 500V-22A with a current gain of 430 was demonstrated.