SiGe profile optimization for low noise using microscopic noise simulation

This paper explores the RF noise physics and SiGe profile optimization for low noise using microscopic noise simulation. A higher Ge gradient in a noise critical region near the EB junction reduces impedance field and hence minimum noise figure. A higher Ge gradient near the EB junction, together with an unconventional Ge retrograding in the base to keep total Ge content below stability, when optimized, can lead to significant noise improvement without sacrificing peak f_T and without any significant high injection f_T rolloff degradation.