Reduction of impact-ionization threshold energies for performance enhancement of complementary impact-ionization metal-oxide-semiconductor transistors

Abstract

We explore the improvement of electrical performance of impact-ionization metal-oxide-semiconductor (I-MOS) transistors by the reduction of impact-ionization threshold energy through incorporation of materials with smaller bandgaps. Silicon-germanium (SiGe) I-MOS transistors were demonstrated. The lower bandgap of SiGe, as compared to Si, contributes to lower electron and hole impact-ionization threshold energies, 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 Si0.60Ge0.40-on-insulator substrates using a complementary metal-oxide-semiconductor compatible process flow. Excellent subthreshold swings as low as 5mV/decade were achieved for the SiGe I-MOS devices. Reduction in breakdown voltage VBD was as large as 1.3 and 1.6V, respectively, for the n- and p-channel Si0.60Ge0.40 I-MOS devices.