Research On 4H-SiC Power BJT Simulation And Characteristics

As the representative of the third generation semiconductor material, Silicon Carbide (SiC) is the promising candidate in application of high temperature, high power, high frequency, anti-radiation fields because of its excellent properties such as wide-band gap, high breakdown field, high thermal conductivity. Among the commercially available SiC types,4H-SiC is the most attractive one due to its higher bulk mobility, lower anisotropy. Continuous research has been done through past decades. High power 4H-SiC BJT is very competitive in power device family, which is widely applied in both military and civilian use such as aerospace, traction, HVDC facility, HEV. However, the low blocking voltage, low current gain, low frequency response and weak reliability of 4H-SiC BJT restrict its application in power system.Firstly, the physics models of new materials in simulator Silvaco-TCAD were improved in the paper, including mobility model, band-gap narrowing model, doping incomplete ionization model, impact ionization model, SRH and Auger generation-recombination model; the simulation can be done successfully under the accurate physics models. Then, the key factors of blocking voltages, current gain, frequency response and power loss were analyzed by combining semiconductor physics and semiconductor device physics, together with Junction Termination Technology (JTT), device design principles. A new device structure was designed with new JTE and buffer layer, highly doped p base region. Then, new structure was simulated and analyzed, compared with traditional structure. At the end, the process flow was discussed, critical processes such as Ohmic contact, pattern etch process and ion implantation are also been discussed.Research results indicate that the simulator is accurate to simulate the SiC material characteristics, the new structure proposed is with blocking voltages 1450V, current gain 52, higher 45% and 30% than traditional structure 1000V and 40 respectively. And the peak electrical field decreases from 3MV/cm to 2.3MV/cm. At the same time, the novel structure is with lower power loss and reverse leakage current, can be applied better in high power system. Finally, the frequency response and power loss are discussed in detail according to physics analvsis.