Papers by Author: Xiao Hui Wang

Abstract: This paper reports our recent study on 4H-SiC power bipolar junction transistors (BJTs) with deep mesa edge termination. 1200 V – 10 A 4H-SiC power BJTs with an active area of 4.64 mm2 have been demonstrated using deep mesa for direct edge termination and device isolation. The BJT’s DC current gain () is about 37, and the specific on-resistance (RSP-ON) is ~ 3.0 m-cm2. The BJT fabrication is substantially simplified and an overall 10% reduction in the device area is achieved compared to the multi-step JTE-based SiC-BJTs.

Abstract: This work reports 4H-SiC bipolar junction transistor (BJT) results based upon our first intentionally graded base BJT wafer with both base and emitter epi-layers continuously grown in the same reactor. The 4H-SiC BJTs were designed to improve the common emitter current gain through the built-in electrical fields originating from the grading of the base doping. Continuously-grown epi-layers are also believed to be the key to increasing carrier lifetime and high current gains. The 4H-SiC BJT wafer was grown in an Aixtron/Epigress VP508, a horizontal hot-wall chemical vapor deposition reactor using standard silane/propane chemistry and nitrogen and aluminum dopants. High performance 4H-SiC BJTs based on this initial non-optimized graded base doping have been demonstrated, including a 4H-SiC BJT with a DC current gain of ~33, specific on-resistance of 2.9 mcm2, and blocking voltage VCEO of over 1000 V.

Abstract: 4H-SiC Junction Barrier Diodes (JBS) diodes were designed, fabricated and tested. The JBS diodes based on a 45μm thick, 1.4×1015cm-3 doped drift layer with multiple non-uniform spacing guard ring edge termination showed a blocking voltage of over 5kV. The 5kV JBS diode has a forward current density of 108A/cm2 at 3.5V and a specific on resistance (RSP_ON) of 25.2mW·cm2, which is very close to the theoretical RSP_ON of 23.3mΩ·cm2. DC I-V measurement of packaged JBS diodes showed a forward current of 100A at a voltage drop of 4.3V. A half-bridge inverter with a bus voltage up to 2.5kV was used to characterize the high power switching performance of SiC JBS diodes. A large inductance load of 1mH was used to simulate the load of a high power AC induction motor. Compared to a Si PIN diode module, the SiC JBS package reduces diode turn-off energy loss by 30% and Si IGBT turn-on energy loss by 21% at room temperature.