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An analysis of space-charge-region recombination in HBT's

Publication Type:

Journal Article


IEEE Trans. Electron Devices (USA), Volume 41, Number 4, p.476 - 83 (1994)



aluminium compounds;Auger effect;electron-hole recombination;gallium arsenide;heterojunction bipolar transistors;III-V semiconductors;semiconductor device models;space charge;tunnelling;


The importance of including recombination in the base side of the emitter-base space-charge-region (SCR) in the computation of the current gain in AlGaAs/GaAs HBT's is investigated. Recombination due to Shockley-Read-Hall, Auger and radiative processes is considered. The interaction of the base-side SCR recombination currents with the neutral-base current and the collector current, which occurs via their dependence on the quasi-Fermi level splitting (ΔEfn) at the base-emitter junction, is not found to be a significant factor in the computation of ΔEfn. However, it is confirmed that the quasi-Fermi level splitting, as calculated from a balancing of the thermionic/tunnel current with the neutral base and collector currents, must subsequently be included in the computation of the base-side SCR currents if the current gain is not to be severely underestimated. A discussion of why the ideality factor is ≈1 for the base-side SCR currents is given. Finally, simple analytical expressions for ΔEfn and the SCR recombination currents are presented and should prove useful for HBT device- and circuit-simulation purposes


space-charge-region recombination;HBT;emitter-base space-charge-region;current gain;Shockley-Read-Hall processes;Auger processes;radiative processes;neutral-base current;collector current;quasi-Fermi level splitting;thermionic/tunnel current balancing;ideality factor;AlGaAs-GaAs;