n-Si/p-Si1−xGex/n-Si double-heterojunction bipolar transistors

Two different structures of n-Si/p-Si1−xGex/n-Si double-heterojunction bipolar transistors have been fabricated by molecular beam epitaxy. A common emitter current gain β of about 15 was demonstrated in one kind of structure and the β-IC curve has been investigated. In the other structure, a novel multistep collector current IC vs collector-emitter voltage VCE characteristic together with a strong negative resistance behavior was observed at room temperature. In this letter the basic experiments are described; a comparison and a discussion of the two kinds of devices are presented.