Semiconductor device and hetero-junction bipolar transistor

摘要

In an npn-type HBT, each of an emitter layer and a collector layer is formed of AlGaN and a base layer is formed of GaN. The emitter layer is in contact with a nitrogen polarity surface of the base layer and the collector layer is in contact with a gallium polarity surface of the base layer. An electric charge is generated at each interface due to a spontaneous polarization and a piezo polarization generated in each of the layers. Because of the electric charge, an internal field is generated so as to accelerate electrons in the base layer.