The Heterojunction-emitter

bipolar transistor A bipolar junction transistor (BJT) is a type of transistor that uses both electrons and electron holes as charge carriers. In contrast, a unipolar transistor, such as a field-effect transistor, uses only one kind of charge carrier. A bipola ...

(HEBT), is a somewhat unusual arrangement with respect to emitter blocking of minority carriers. This is accomplished by using heterostructure confinement 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 Analog or analogue may refer to: Computing and electronics * Analog signal, in which information is encoded in a continuous variable ** Analog device, an apparatus that operates on analog signals *** Analog electronics, circuits which use analo ...

performance. The main difference of the HEBT from the

Heterojunction bipolar transistor The heterojunction bipolar transistor (HBT) is a type of bipolar junction transistor (BJT) which uses differing semiconductor materials for the emitter and base regions, creating a heterojunction. The HBT improves on the BJT in that it can handle s ...

(HBT) is that the emitter–base interface is the same as in a

bipolar junction transistor A bipolar junction transistor (BJT) is a type of transistor that uses both electrons and electron holes as charge carriers. In contrast, a unipolar transistor, such as a field-effect transistor, uses only one kind of charge carrier. A bipola ...

(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 Epitaxy refers to a type of crystal growth or material deposition in which new crystalline layers are formed with one or more well-defined orientations with respect to the crystalline seed layer. The deposited crystalline film is called an epi ...

, 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 Diffusion is the net movement of anything (for example, atoms, ions, molecules, energy) generally from a region of higher concentration to a region of lower concentration. Diffusion is driven by a gradient in Gibbs free energy or chemical p ...

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

. Also of importance for optoelectronic hybrids is that HEBT can be constructed in any semiconductor system that permits the use of band-gap–altering alloys in the emitter.

References

* * {{cite journal , doi = 10.1088/0268-1242/17/5/301 , title = Theoretical investigation of an InGaP/GaAs heterostructure-emitter bipolar transistor with a wide-gap collector , year = 2002 , last1 = Cheng , first1 = Shiou-Ying , journal = Semiconductor Science and Technology , volume = 17 , issue = 5 , pages = 405 Transistor types Microwave technology