Hole transport and quasi-Fermi level splitting at the emitter-base junction in Pnp heterojunction bipolar transistors

Hole transport across the emitter-base heterojunction in Pnp heterojunction bipolar transistors is considered and the amount of hole quasi-Fermi level splitting at the interface is analyzed. Hole injection at the emitter is shown to significantly limit the emitter current to a level more than an order of magnitude less than that predicted by the hole-base diffusion model. Due to the low hole mobility, hole drift diffusion across the emitter-base space charge region is shown to be of comparable importance to thermionic-tunneling emission in controlling hole injection into the base. (C) 1999 American Institute of Physics. [S0021-8979(99)01203-7].