| 摘要 |
PURPOSE:To enhance electron concentration, by adding impurities into a part or all of a GaAs layer of an FET having a GaAs-AlGaAs heterostructure. CONSTITUTION:On a semi-insulating GaAs substrate 5, a GaAs layer 6, in which impurities are doped in at least a part 6a is provided. An AlGaAs layer 7 is provided on the layer 6. Then, in addition to electrons, which react the GaAs layer from an N-type AlGaAs layer through a heterogeneous interface, electrons are supplied to an undoped GaAs layer 6b from the N-type GaAs layer 6a. Therefore, high concentration of 10<17>cm<-3> or higher can be obtained. When electron-gas existing region is limited to only the undoped layer 6a, high electron mobility can be maintained. When impurities are doped in the entire GaAs layer 6, the electron mobility is decreased, but the higher electron concentration can be obtained. In the present invention, the high electron concentration and the high electron mobility can be simultaneously implemented. Therefore, excellent switching characteristics can be obtained. |
