Abstract: Disclosed is an ultra high frequency radio communication apparatus having: a receiver antenna; a transmitter antenna; an IC chip being electrically connected to the receiver antenna and the transmitter antenna; a substrate on which the receiver antenna, the transmitter antenna and the IC chip are mounted; an input terminal for inputting to the IC chip a base band input signal; an output terminal for outputting a base band output signal from the IC chip; and a control signal terminal for inputting a control signal for controlling the IC chip to the IC chip. The IC chip is placed in a shielding space such that the cut-off frequency of the shielding space is higher than the frequency of a carrier signal for radio communication.

Abstract: A heterojunction bipolar transistor comprises n.sup.+ -type GaAs collector contact region, an n-type GaAs collector region, a p.sup.+ -type GaAs base region, an n-type AlGaAs emitter region, and an n.sup.+ -type InGaAs emitter contact region, all of which are formed on a semiinsulative GaAs substrate. A heterojunction is formed by the base region and the emitter region. The emitter region is formed in mesa shape by dry etching. Around this mesa, B.sup.+ ion-implanted high-resistance region is formed. The base-emitter Junction is isolated from the ion-implanted region. The heterojunction bipolar transistor therefore has little on-voltage changes.

Abstract: A class C power amplifier has a heterojunction bipolar transistor as an element for amplifying an input signal. A d.c. bias voltage source, such as a d.c. battery, is connected to the transistor, such that a d.c. bias voltage lower than the turn-on voltage of the transistor is applied between the base and emitter of the bipolar transistor. An inductance coil is connected in series between the emitter of the transistor and the d.c. bias voltage source. Since the d.c. bias voltage is applied to the heterojunction bipolar transistor, the external drive voltage for activating the transistor is reduced to increase the high-frequency power gain of the amplifier.

Abstract: A heterojunction bipolar integrated circuit is disclosed which uses a heterojunction bipolar transistor with a heterojunction between an emitter region and a base region. In this transistor, a pn junction between the base region and the emitter region has a greater area than a pn junction between the base region and a collector region. A plurality of such heterojunction bipolar transistors are isolated on a substrate to perform logic operations in an unsaturated region.

Abstract: A method for manufacturing power switching devices such as thyristors and power transistors comprising the steps of forming impurity diffused layers of one conductivity type and of the opposite conductivity type in a semiconductor substrate of one conductivity type; forming a film containing phosphorus on the substrate; diffusing lifetime killer atoms into the substrate; and forming electrodes on the substrate.