Extraction of the Average Collector Velocity in High-Speed "Type-II" InP–GaAsSb–InP DHBTs

H.G. Liu, N. Tao, S.P. Watkins, C.R. Bolognesi
2004 IEEE Electron Device Letters  
In "type-II" NpN InP-GaAsSb-InP double heterostructure bipolar transistors (DHBTs), the + GaAsSb base conduction band edge lies above the InP collector conduction band: a small ballistic injection energy is thus imparted to electrons as they are launched into the collector. The resulting high initial velocity should in principle reduce the collector signal delay time in comparison to the case where thermal electrons are accelerated by the collector electric field alone. In this letter, we
more » ... is letter, we extract the bias dependence of the average collector electron velocity in high-speed InP-GaAs 0 62 Sb 0 38 -InP DHBTs, and find a maximum average velocity reaching 4 10 7 cm/s across a 2000 A InP collector. This finding provides evidence of the performance advantage afforded by abrupt type-II base/collector (B/C) junctions for collector transport when compared to other B/C junctions.
doi:10.1109/led.2004.838553 fatcat:snmvag2eyjcjvo4f6xm7k6yfku