A complementary-I-MOS technology featuring SiGe channel and i-region for enhancement of impact-ionization, breakdown voltage, and performance

We report the first demonstration of silicon-germanium (SiGe) impact-ionization MOS (I-MOS) transistors that feature a SiGe channel and a SiGe impact-ionization region. The lower bandgap of SiGe as compared to Si contributes to higher electron and hole impact-ionization rates, leading to avalanche breakdown at a much reduced source voltage and enhanced device performance. Both n-and p-channel I-MOS devices were fabricated on Si0.7sGe0.25-on-insulator substrates using a CMOS-compatible process flow. Compared to Si I-MOS, the breakdown voltage of SiGe I-MOS is reduced by ~1 V along with the doubling of the drive current and transconductance. The subthreshold swing is also improved. Excellent subthreshold swings of 2.88 mV/decade and 3.24 mV/decade are achieved for the n-and p-channel SiGe I-MOS devices, respectively.