Nec Compound Semiconductor Devices, Ltd.

Koji Azuma

Hidenori Shimawaki

Takaki Niwa

Naoto Kurosawa

A heterojunction bipolar transistor has a raised breakdown voltage and restrains the rising characteristic of I-Vcharacteristic from degrading. The collector region includes first, second, and third collector layers of semiconductor. The first collector layer is made of a doped or undoped semiconductor in such a way as to contact the sub-collector region. The second collector layer is made of a doped or undoped semiconductor having a narrower band gap than the first collector layer in such a way as to contact the base region. The third collector layer has a higher doping concentration than the second collector layer in such a way as to be located between or sandwiched by the first collector layer and the second collector layer.

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Kawasaki, Japan

Koji Azuma