| 摘要 |
PURPOSE:To reduce the leak current at a gate, by forming a P<+> type AlGaAs layer on an n-type AlGaAs layer and an n-type GaAs layer, and utilizing a hetero junction of P<+> type AlGaAs and n-type GaAs as a gate. CONSTITUTION:A P<+> type AlGaAs layer 5 is formed on an n-type AlGaAs layer 2 and an n-type GaAs layer 3. As the result of this, a gate is formed as a hetero junction of the layers 5 and 3. A current component (1) flowing from the n-type GaAs to the P<+> type AlGaAs has a higher energy gap corre sponding to the energy level difference of both conduction bands as compared with the case shown by a dotted line, and is reduced as compared with the case of homo junction shown by the dotted line. A current component (2) flowing from the P<+> type AlGaAs to the n-type GaAs is reduced as compared with the case shown by the dotted line, because the electron density in the conduction band of the P<+> type AlGaAs is lower in the case of nearly equal density of impurity by the amont of a wider forbidden bandwidth. Positive hole currents (3) and (4) are reduced by the effect of a barrier, as compared with the case shown by the dotted line. Thus the leak current is reduced. |
