| 摘要 |
PURPOSE:To obtain a high current amplification factor and to obtain excellent frequency characteristics, by providing a layer having higher impurity concentration in comparison with a part, which is in contact with an outer base layer, in a part of an emitter layer, which is not in contact with the outer base layer. CONSTITUTION:A first emitter layer has an impurity concentration of 5X10<18>/cm<3> and a thickness of 5,000Angstrom . A transition layer 14 has impurity concentration of 5X10<18>/cm<3> and a thickness of 500Angstrom . A second emitter layer 13 has an impurity concentration of 5X10<17>/cm<3> and a thickness of 2,500Angstrom . A base layer 15 has an impurity concentration of 3X10<18>/cm<3> and a thickness of 1,000Angstrom . A collector layer 16 has an impurity concentration of 5X10<16>/cm<3> and a thickness of 4,000Angstrom . Thus the layers up to the layer 16 are epitaxially grown on an n<+>-GaAs substrate 11. For example, Mg ions are implanted in the substrate 11 by a dose amount of 2X10<14>/cm<3> at an accelerating voltage of 200keV. Quick heating is performed by infrared rays for 2 seconds at 850 deg.C. Thus a p<+> type outer base layer 17 is formed.
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