Abstract
This paper describes the operating characteristics of NPN 4H-SiC (a polytype of silicon carbide) bipolar junction transistor (BJT) and 4H-SiC Darlington Pairs. A large amount of experimental data was collected. The wafer BJTs were able to block over the rated 600 V in the common-emitter configuration and the TO-220 BJTs were able to block over the 1200 V rated voltage. In the thermal analysis, it is found out that at higher temperatures the forward and reverse (blocking) characteristics were stable at 100°C and 200°C. The transistors show positive temperature coefficients of forward voltage (Vf). In general the current gain (β) characteristics obtained (with VCE = 6 V) were approximately as expected for the BJTs. The β‘s were very low (2 to 5 for wafer BJTs, 5 to 20 for the wafer Darlington Pairs, and 5 to 30 for TO-220 BJTs). The large amount of experimental data collected confirms some of the superior properties of the Silicon carbide material when used to fabricate power semiconductor devices, namely high thermal conductivity and high temperature operability. The data presented here will establish the trends and the performance of silicon carbide devices. The silicon carbide BJT has fast switching and recovery characteristics. From the analysis, silicon carbide power devices will be smaller (about 20 times) than a similar silicon power device and with reduced power losses. Silicon carbide will also be very useful for device integration in high densities, as found in integrated chips for current handling capabilities, for applications in instrumentation and measurements. Presently, most of the research is on improving the basic silicon carbide material quality, power device optimization, and applications engineering using devices that have been developed to date.
Highlights
Today’s efforts to replace conventional mechanical, hydraulic, and pneumatic power transfer systems with electric drives and their power electronics converters have taken off at an increasingly rapid rate (e.g., automobile electric brakes, traction control and electronic stability-control systems, electronic power-assisted steering (EPAS), etc.)
Even though large amount of data was collected for these studies, results are presented for typical Darlington Pair and typical bipolar junction transistor (BJT) devices from the wafer Reticles, and the TO-220 BJTs
Low emitter doping, 2) low minority carrier life-times in the base layer, and 3) poor ohmic contact resistance of the p + layer contact [9,10,11,12]
Summary
Today’s efforts to replace conventional mechanical, hydraulic, and pneumatic power transfer systems with electric drives and their power electronics converters have taken off at an increasingly rapid rate (e.g., automobile electric brakes, traction control and electronic stability-control systems, electronic power-assisted steering (EPAS), etc.). If silicon carbide (SiC) devices (power transistors, integrated chips (ICs), etc.) are developed and commercialized, they will replace silicon (Si) devices, since SiC devices will offer improvements to system weight, volume, losses, efficiency, and temperature capability. These improvements are needed over the few years to realize the full potential of more-electric system paradigms and reduced power consumption goals. The results of forward and reverse V-I characteristics, current gain characteristics, and dynamic measurements on 4H-SiC Darlington Pairs and BJTs in the common-emitter configuration are presented. Device data presented in this paper represent the measured performance characteristics observed from numerous devices of each type, enabling reasonable statistical inferences
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