Temperature Dependence of Conductivity Modulation in SiC Bipolar Junction Transistors

Temperature dependence of conductivity modulation in SiC bipolar junction transistors (BJTs) from 300 to 573 K was experimentally investigated by evaluating current-voltage characteristics in the SiC BJTs, which exhibit the clear conductivity modulation at room temperature. The ON-resistance increased with elevating the temperature because the current gain was degraded and the resistance in the collector layer (unipolar resistance) increased due to reduced mobility. However, since the carrier lifetime in the collector layer was lengthened and the base spreading resistance decreased with an increase in the temperature due to the enhanced ionization of aluminum acceptors, stronger conductivity modulation was caused than that evoked at 300 K. Thus, the ratio of the ON-resistance to the unipolar resistance was reduced with the increase in the temperature and reached only 40% at 573 K. In addition, the expansion of the conductivity-modulated region was experimentally demonstrated, which was predicted in our previous simulation work.