SILICON HETEROJUNCTION BIPOLAR POWER TRANSISTOR WITH AN AMORPHOUS SI-B ALLOY EMITTER

A pnp Si heterojunction bipolar power transistor has been fabricated using an amorphous Si0.7B0.3 alloy as a wide band-gap emitter. The amorphous alloy is formed by co-deposition of B and Si: it has a low resistivity of 2.5 X 10(-3) OMEGA cm at room temperature after annealing at 1000-degrees-C for 30 min and a band gap of 1.70 eV when annealed at 1100-degrees-C for 20 min. In order to make a direct comparison, a conventional transistor with a diffused emitter and a polycrystalline silicon (poly-Si) emitter transistor have also been fabricated. It is shown that an amorphous Si0.7B0.3 alloy emitter transistor can have an electrical current gain 2-5 times higher than a poly-Si emitter transistor and 20 times higher than a conventional transistor.