Question # 10 / 11

Hetero-Junction Bipolar Transistor by Adam Jacobs
Consider the band diagrams below:

Specify which band diagrams (Figure A or B) corresponds to the transistor specified.
Figure A B is a homojunction bipolar transistor: BJT (qVn equal to qVp)
Figure A B is an heterojunction bipolar transistor HBT (qVn smaller than qVp).
Match the proper label with the corresponding band edge discontinuity.
A B C D corresponds to qVn the electron barrier
A B C D corresponds to qVp the hole barrier
A B C D corresponds to qV_EB
A B C D corresponds to qV_CB

In a npn HBT the emitter injection efficiency and therefore the current gain is inceased by selecting an emitter with a bandgap such that electron barrier qVn is decreased increased and the hole barrier is decreased increased .

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