Heterostructure-emitter bipolar transistor
The Heterojunction-emitter bipolar transistor (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.
Source: Wikipedia — Heterostructure-emitter bipolar transistor (CC BY-SA 4.0)