Abstract: A III-V semiconductor device is disclosed, which includes an emitter region, an emitter barrier region having such a barrier height as to substantially restrict a thermionic emission current as compared with a tunneling current and such a barrier width as to permit the tunneling current, a base region containing indium and having higher electron affinity than said emitter region and a collector barrier region having such a barrier height as to substantially prohibit a thermally distributed electron from overflowing and such a barrier width as to substantially prohibit the tunneling current.