Abstract: A modulation-doped field effect transistor comprises a gate recess through a top insulating layer, having a cross-section in a semiconductor layer increasing down to an interface with a further semiconductor layer and thereafter having a cross-section in the further semiconductor layer decreasing down to the bottom of the recess in the further semiconductor layer. A gate electrode is formed in the recess.

Abstract: The invention relates to a variable capacitance element operating in the ultra-high frequency range. In order to integrate this element on to an integrated circuit chip, the element is designed so that the control voltage does not interfere with the ultra-high frequency signal and has neither filters nor shock chokes which are not integrable. The element according to the invention utilizes the junction capacitances variation of at least one diode, reverse-biased by a voltage across a resistor, the high frequency signal being at the diode anode. The element construction comprises an active zone in a semiinsulating substrate. Two metallizations partly cover the active zone and form therewith at least one diode. A projection to the active zone forms the resistor, to which is applied the control voltage. The diodes are p-n junctions of schottky diodes. The semiconductor material is Si or from the III-V group. Application to oscillators, filters, phase shifters, etc. in ultra-high frequency equipment.

Abstract: The invention relates to a vertical field effect transistor operating under ballistic conditions at very high frequencies (100-200 GHz). In order to increase the output impedance of this transistor, as well as its power, the field effect of the first gate is decoupled from the drain by the field effect of a second gate. The two gates are carried by two opposite sides of a mesa etched in the active layer beneath the drain. The second gate is displaced with respect to the first gate and is closer to the drain. The displacement is obtained by an insulating layer beneath the second gate. The two gates are successively deposited by lateral projections. Application to ultra-high frequency systems.

Abstract: A filter tip for a smoking product comprised of a filter rod attached at one end to the smoking product. The filter rod is surrounded by a tip wrapping layer which terminates at a distance from the mouth end of the filter rod. The projecting end of the rod is tapered toward the mouth end. The taper causes smoke drawn through the filter tip to flow out obliquely with respect to the longitudinal axis of the smoking product.

Abstract: The invention relates to a field effect transistor for ultra-high frequencies, whose gate has a metal-insulator structure with a metal leak. This transistor has a substrate, an active layer, a source electrode and a drain electrode. Thus, its gate comprise a first metal coating forming a Schottky junction with the active layer, a dielectric layer having a controlled leak and a second control gate metal coating. The leak in the dielectric is adjusted in such a way that the Schottky interface and the control gate are in electrical balance at high frequencies. The dielectric is a metal-rich, non-stoichiometric oxide or nitride. Application to high-speed integrated circuits on GaAs.

Abstract: A varactor or mixer diode comprises a mesa shaped semiconductor element having a p-n junction barrier layer or retifying junction on its upper face and a substrate contact on its opposite face, the substrate contact extending over the side faces of the semiconductor element and ending at a small spacing from the barrier layer or junction.

Abstract: In a method for the manufacture of a field-effect transistor comprising a substrate and an epitaxial layer located thereon, a V-shaped trench extending from the surface of the epitaxial layer through the epitaxial layer into the substrate is made and a zone is created by implantation in an area located in front of the V-shaped trench.

Abstract: An opto-electronic switch component which comprises two regions of good conductivity separated by a gap on a normally non-conductive substrate. When the gap is irradiated, the conductivity of the substrate increases and a connection is formed between the two regions.

Abstract: A variable capacitance diode comprises a low resistance semi-conductor substrate on which is epitaxially deposited three layers, a first layer adjacent the substrate having an impurity concentration which decreases towards the substrate, a very thin intermediate region and a relatively thin surface region of lower doping than the intermediate region, a barrier being formed on or in the outer surface of the relativey thin surface region.The invention also includes a method of making such a diode.