One-flux analysis of current blocking in double-heterostructure bipolar transistors with composite collectors

Abstract

The flux method of McKelvey, Longini, and Brody [Phys. Rev. 123, 51 (1961)] is used to analyze current blocking in double-heterostructure bipolar transistors with composite collectors (CC). The effects of electron accumulation in the spacer layer are included; these are shown to impose an intrinsic limit on the simplest CC design. The analysis is extended to include compositional or band-gap grading, which can substantially reduce the current blocking at high currents, though it has less effect at lower currents.