A proposed structure for collector transit-time reduction in AlGaAs/GaAs bipolar transistors

The impact of velocity overshoot in the collector space-charge region on carrier transport is explored. The effects of overshoot on transit time for conventional collector structures are found to be minor. A new collector structure which exhibits extended velocity overshoot is proposed. This structure promises both simple fabrication and significant improvements (≃ 25 percent) in carrier transit time over conventional collector structures as demonstrated by Monte Carlo simulation.