| 4H silicon carbide (4H-SiC) bipolar junction transistor (BJT) is a very promising wide band gap semiconductor switching device for high temperature and high power applications. The superior material properties of 4H-SiC, including wide band gap, high breakdown electric field, high thermal conductivity make 4H-SiC ideal for power electronics applications. 4H-SiC power BJT is an intrinsically normally-off switching device, has higher current handling capabilities due to its bipolar character, and is free of the gate oxide problems as in 4H-SiC metal-oxide-semiconductor field effect transistor (MOSFET). Moreover, 4H-SiC BJT easily surpasses silicon BJT with higher current gain, much larger safe-operating-area (SOA) and free of thermal breakdown problem. 4H-SiC power BJT has been gaining more and more attentions since it was first reported in 2000.; In this thesis, investigations have been focused on (i) increasing blocking voltage, (ii) increasing current gain, (iii) decreasing specific on-resistance (RSP_ON), (iv) increasing the handling power of 4H-SiC power BJTs, based on various design and implementation of (a) BJT wafer epi-layer structure, (b) junction edge termination, (c) surface passivation, (d) base Ohmic contact and overlay metal process, (e) device essential dimensions. The study has resulted in the demonstration of the world's highest blocking voltage (9.2 kV) 4H-SIC BJT, the world's lowest Rsp,on (2.9 O.cm2) 4H-SiC BJT, the world's largest size (3 mm x 5 mm) 4H-SiC BJT, and among the highest current gain (beta=47) 4H-SiC BJT. An implantation-free 4H-SiC power BJT based on a novel structure (double epi-base) has also been demonstrated for the first time, showing high gain (beta=31) and high blocking voltage (1336 V). |
