Importance of velocity modulation: analysis and experimental verification

Abstract

Velocity modulation, i.e. current dependent electron mobility, is claimed to be essential for the HF-potential of InP-HBTs in that it significantly reduces charge storage effects of the collector. The reduction is related to operation in base pushout, and high-speed InP-HBTs are regularly operated in this mode to obtain optimum performance. As a consequence, dynamic effects of base pushout may cause a resonance in the unilateral power gain for advanced devices, by that obstructing estimation of the maximum frequency of oscillation.