Abstract: A novel structure of ideal ohmic contact p+(SiGeC)-n--n+ diodes with three-step graded doping concentration in the base region is presented,and the changing doping concentration gradient is also optimized.Using MEDICI,the physical parameter models applicable for SiGeC/Si heterojunction power diodes are given.The simulation results indicate that the diodes with graded doping concentration in the base region not only have the merit of fast and soft reverse recovery but also double reverse blocking voltage,and their forward conducting voltage has dropped to some extent,compared to the diodes with constant doping concentration in the base region.The new structure achieves a good trade-off in Qs-Vf-Ir,and its combination of properties is superior to ideal ohmic contact diodes and conventional diodes.

Key words: SiGeC/Si heterojunction,  power diodes,  reverse blocking voltage,  ohmic contact