Abstract: A field-effect transistor includes a semi-insulating substrate, a semiconductor layer consisting of successive layers of GaAs compound semiconductor formed on the substrate, a gate electrode forming a Schottky contact with the semiconductor layer, and source and drain electrodes each forming an ohmic contact to the semiconductor layer. A semiconductor layer includes a buffer layer, an active layer, and a contact layer, where the impurity concentration in the contact layer is substantially equal to that in the active layer at the interface therewith. The impurity concentration in the contact layer increases continuously from the interface toward the upper surface of the contact layer. The field-effect transistor achieves a reduction in the ON resistance and an increase in the gate breakdown voltage at the same time, and to reduce power loss and increase efficiency.

Abstract: A hybrid element for phase shifting an input signal and providing a phase shifted output signal includes conductive plates which are capacitive coupled together. The hybrid element includes four terminals: an input terminal for receiving an input signal, an isolation terminal capacitive coupled with the input terminal and for providing an output signal, a through terminal connected directly with the input terminal, and a coupling terminal capacitive coupled with the input terminal. A distributed constant line and an FET are connected in pair with the through and coupling terminals, respectively, the other end of the distributed constant line being connected with earth. When the FET is turned on or off, the amount of phase shift in the phase shifter is controlled. Since the FET and distributed constant line are connected together in parallel, the amount of phase shift can be adjusted easily by turning the FET on or off.

Abstract: A compound semiconductor device comprises a substrate formed from a single crystal of silicon, a layer of an insulator formed on a portion of a surface of the substrate, at least one layer of a high resistance compound semiconductor formed on the insulator layer, and at least one layer of a single crystal of a compound semiconductor formed on a different portion of the substrate surface from the insulator layer. The device can be manufactured by forming an insulator layer on one portion of a surface of a single crystal silicon substrate, and growing a compound semiconductor by epitaxy on the insulator layer and on the different portion from the insulator layer. One of useful applications is a hybrid semiconductor device having a compound semiconductor formed from e.g. GaAs on a silicon substrate.