A high-frequency conductor having improved conductivity comprises at least one electrically conductive base material. The ratio of the outer and inner surfaces of the base material permeable by a current to the total volume of the base material is increased by a) dividing the base material perpendicularly to the direction of current into at least two segments, which are spaced from each other by an electrically conductive intermediate piece and connected both electrically and mechanically to each other, and/or b) topographical structures in or on the surface of the base material and/or c) inner porosity of at least a portion of the base material compared to a design of the base material in which the respective feature was omitted. It was found that, as a result of these measures concerning the design, it is possible to physically arrange the same amount abase material so that a larger fraction of the base material is located at a distance of no more than skin depth from an outer or inner surface and is thus involved in current transport. As a result, a lesser fraction remains unused as a function of the skin effect.

Gate structures for semiconductor devices include a silicon nitride layer, an electron beam evaporated tantalum nitride layer disposed on the silicon nitride layer, a first electron beam evaporated titanium layer disposed on the tantalum nitride layer, an electron beam evaporated gold layer deposited on the first titanium layer, and a second electron beam evaporated titanium layer deposited on the gold layer.

A method for forming a HEMT is disclosed. A substrate is provided. A buffer layer, a channel layer on the buffer layer, a barrier layer on the channel layer, and a semiconductor gate layer on the barrier layer are formed on the substrate. A metal gate layer is formed on the semiconductor gate layer. A spacer is formed on sidewalls of the metal gate layer. The semiconductor gate layer is then etched by using the spacer and the metal gate layer as an etching mask. A passivation layer is then formed to cover the barrier layer, the semiconductor gate layer and the metal gate layer. An opening is formed in the passivation layer to expose the metal gate layer. A gate electrode is formed on the passivation layer and in direct contact with the metal gate layer.

An improved gate metal structure for compound semiconductor devices comprises sequentially a compound semiconductor substrate, a Schottky barrier layer, an insulating layer and a gate metal. The insulating layer has a gate recess. The surrounding and the bottom of the gate recess are defined by the insulating layer and the Schottky barrier layer respectively. The gate metal includes a contact layer formed on the insulating layer, covering the gate recess and contacted with the Schottky barrier layer at the bottom of the gate recess; a first diffusion barrier layer formed on the contact layer; a second diffusion barrier layer formed on the first diffusion barrier layer; and a conduct layer formed on the second diffusion barrier layer. Thereby the reliability of the compound semiconductor devices is enhanced.

In a semiconductor device in the present disclosure, a first nitride semiconductor layer has a two-dimensional electron gas channel in a vicinity of an interface with a second nitride semiconductor layer. In plan view, an electrode portion is provided between a first electrode and a second electrode with a space between the first electrode and the second electrode, and a space between the second electrode and the electrode portion is smaller than the space between the first electrode and the electrode portion. An energy barrier is provided in a junction surface between the electrode portion and the second nitride semiconductor layer, the energy barrier indicating a rectifying action in a forward direction from the electrode portion to the second nitride semiconductor layer, and a bandgap of the second nitride semiconductor layer is wider than a bandgap of the first nitride semiconductor layer.

A field effect transistor according to the present invention includes a semiconductor layer including a groove, an insulating film formed on an upper surface of the semiconductor layer and having an opening above the groove and a gate electrode buried in the opening to be in contact with side surfaces and a bottom surface of the groove and having parts being in contact with an upper surface of the insulating film on both sides of the opening, wherein the gate electrode has a T-shaped sectional shape in which a width of an upper end is larger than a width of the upper surface of the insulating film.

A heterojunction device, includes a substrate; a III-nitride semiconductor region located longitudinally above or over the substrate and including a heterojunction having a two-dimensional carrier gas; first and second laterally spaced terminals operatively connected to the semiconductor; a gate structure of first conductivity type located above or longitudinally over the semiconductor region and laterally spaced between the first and second terminals; a control gate terminal operatively connected to the gate structure, a potential applied to the control gate terminal modulates and controls a current flow through the carrier gas between the terminals, the carrier gas being a second conductivity type; an injector of carriers of the first conductivity type laterally spaced away from the second terminal; and a floating contact layer located over the carrier gas and laterally spaced away from the second terminal and operatively connected to the injector and the semiconductor region.

A method of forming a bipolar transistor with a vertical collector contact requires providing a transistor comprising a plurality of epitaxial semiconductor layers on a first substrate, and providing a host substrate. A metal collector contact is patterned on the top surface of the host substrate, and the plurality of epitaxial semiconductor layers is transferred from the first substrate onto the metal collector contact on the host substrate. The first substrate is suitably the growth substrate for the plurality of epitaxial semiconductor layers. The host substrate preferably has a higher thermal conductivity than does the first substrate, which improves the heat dissipation characteristics of the transistor and allows it to operate at higher power densities. A plurality of transistors may be transferred onto a common host substrate to form a multi-finger transistor.

A Schottky barrier diode includes a substrate, a first semiconductor layer formed on the substrate, a second semiconductor layer formed on the first semiconductor layer, and a metal layer formed on the second semiconductor layer to form a Schottky barrier, wherein the first semiconductor layer and the second semiconductor layer are formed of different materials, and a conduction band offset between the first semiconductor layer and the second semiconductor layer is less than a set value.

A high-electron mobility transistor (HEMT) includes a substrate, a group III-V channel layer, a group III-V barrier layer, a group III-V cap layer, a source electrode, a first drain electrode, a second drain electrode, and a connecting portion. The group III-V channel layer, the group III-V barrier layer, and the group III-V cap layer are sequentially disposed on the substrate. The source electrode is disposed at one side of the group III-V cap layer, and the first and second drain electrodes are disposed at another side of the group III-V cap layer. The bottom surface of the first drain electrode is separated from the bottom surface of the second drain electrode, and the composition of the first drain electrode is different from the composition of the second drain electrode. The connecting portion is electrically coupled to the first drain electrode and the second drain electrode.