Heterostructure-emitter bipolar transistor
Overview
The Heterojunction emitter bipolar transistor (HEBT), is a somewhat unique arrangement, with respect to emitter blocking, of minority carriers. This is accomplished, by using a heterostructure diode, in the emitter, introducing an energy barrier, to minority carrier charge flow from the base. This is important as loss of minority carriers from the base to the emitter degrades analog performance. The main difference of the HEBT from the Heterostructure bipolar transistor (HBT) is that the emitter base interface is the same as in a bipolar junction transistor (BJT) with the blocking energy gap being moved back into the emitter bulk region.
Functional Architecture
The main advantage of HEBT architecture, compared to the HBT is a simplified fabrication process for the emitter base junction. In particular the HEBT does not require as tight parametric control during epitaxial growth, that equivalent, abrupt, or graded emitter, structures might. This is very important, as it is evident from scanning ion mass spectrometry data, that out diffusion base dopant into the emitter junction is difficult to control, as the base is, in general very highly doped, in order to enhance performance.
Application
The HEBT, is well positioned, as a potential candidate, for key roles, in high frequency optoelectronic markets, similar to the Heterostructure bipolar transistor. Also of importance for optoelectronic hybrids is that HEBT can be constructed, in any semiconductor system, that permits the use, of energy band gap altering alloys, in the emitter.
References
doi: 10.1016/0038-1101(94)90231-3
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