Heterojunction Bipolar Transistors (HBT) with a-Si:H or μc-Si Emitter

Abstract

AbstractIn this paper phosphorous doped amorphous and microcrystalline silicon are used as emitter material for npn bipolar transistors. A heterojunction is formed between emitter and base, resulting in a higher current gain β for the same base parameters in comparison with conventional transistors. Because the amorphous silicon results in a too high emitterresistance, a compromise solution is microcrystalline silicon (μc-Si). HREM-micrographs give credit to the true heterojunction concept and show epitaxial reorganization, especially after annealing of the amorphous silicon.