| 摘要 |
PURPOSE:To obtain excellent high speed feature and to obtain a high current amplification factor, by setting the maximum value of majority carriers in a base region at the density of state or less, where majority carriers are present, by built-in voltages between an emitter region and a base region and between the base region and a collector region. CONSTITUTION:On an n<+> GaAs substrate 11, the following regions are sequentially laminated by an MBE method: an n-type GaAs collector region 12; a p<+> type GaAs region 13; an n-type AlxGa1-xAs transient region 14, in which the composition is controlled so that the band gap is gradually changed; an n-type Al0.3Ga0.7As emitter region 15; and n<+> type GaAs cap layer 16, which facilitates ohmic contact with the emitter region. The impurity density of the collector region 12 is 5X10<16>cm<-3>, and Si is used as n-type dopant. Be is used as dopant in the base region 13. Its impurity density is 5X10<19>cm<-3> and its thickness is set at 10Angstrom . Both the transition region 14 and the emitter region 15 have the impurity density of 3X10<17>cm<-3>. The cap layer 16 is doped to the high concentration of 5X10<18>cm<-3>. |
