Abstract: A high current density, low contact resistance contact for wide bandgap (WBG) or ultra-wide bandgap materials (UWBG) is disclosed. The contact is lithographically formed so that a total perimeter length of the contact structure is at least twice the length of the side of a contact pad closest to the gate in a high electron mobility transistor (HEMT). The contact structure may take the form of a plurality of columns having various cross-sectional shapes, or may take the form of a convoluted geometrical shape, such as a comb-like, serpentine, or spiral shape. The depth of the contact structure permits direct contact with the two-dimensional electron gas (2DEG) in the HEMT by the perimeter of the contact structure. The contact structure is formed of at least one metal layer, at least one doped material regrown layer, or at least one implanted region. The contact structure may be applied to other WBG and UWBG devices.

Abstract: A microwave structure having an input section for receiving both a common mode signal and a CPW differential mode signal; an output section; and a CPW transmission line, having a center conductor disposed between a pair of coplanar ground plane conductors, connected between the input section and the output section. The conductors of the CPW transmission line are configured to provide the common mode signal a different attenuation in passing to the output section than the CPW transmission line provides to the differential mode signal passing between the input section and the output section.

Abstract: A transmission line structure having a pair of separated coplanar waveguide transmissions line section. A coupling circuit is coupled between the pair of coplanar waveguide transmissions line sections, the coupling circuit suppresses common mode signals therein and passes, substantially unsuppressed, differential mode signal transmission between the pair of coplanar waveguide transmissions line sections.

Abstract: A semiconductor structure having a Group III-N buffer layer and a Group III-N barrier layer in direct contact to form a junction between the Group III-V buffer layer the Group III-N barrier layer producing a two dimensional electron gas (2DEG) channel, the Group III-N barrier layer having a varying dopant concentration. The lower region of the Group III-N barrier layer closest to the junction is void of intentionally introduced dopant and a region above the lower region having intentionally introduced, predetermined dopant with a predetermined doping concentration above 1×1017 atoms per cm3.

Abstract: A heterojunction semiconductor field effect transistor HFET having a pair of layers of different semiconductor materials forming a quantum well within the structure to support the 2DEG. Source, drain and gate electrodes are disposed above the channel. The HFET has a predetermined transconductance. A transconductance control electrode varies an electric field within the structure under the channel to vary the shape of the quantum well and thereby the transconductance of the FET in accordance with a variable control signal fed to the transconductance control electrode.

Abstract: A heterojunction semiconductor field effect transistor HFET having a pair of layers of different semiconductor materials forming a quantum well within the structure to support the 2DEG. Source, drain and gate electrodes are disposed above the channel. The HFET has a predetermined transconductance. A transconductance control electrode varies an electric field within the structure under the channel to vary the shape of the quantum well and thereby the transconductance of the FET in accordance with a variable control signal fed to the transconductance control electrode.

Abstract: A monolithic microwave integrated circuit structure having: a semiconductor substrate structure having a plurality of active devices and a microwave transmission line having an input section, an output section and a interconnecting section electrically interconnecting the active devices on one surface of the substrate; a thermally conductive, electrically non-conductive heat sink; and a thermally conductive bonding layer for bonding the heat sink to the substrate, the thermally conductive bonding layer having an electrically conductive portion and an electrically non-conductive portion, the electrically conductive portion being disposed between the heat sink and an opposite surface of a portion of the substrate having the active devices and the electrically non-conductive portion being disposed on the opposite surface portion overlaying portion of the microwave transmission line section.

Abstract: A semiconductor structure having: a Group III-N channel layer, a Group III-N top-barrier polarization-generating layer forming a heterojunction with an upper surface of the channel layer; and a Group III-N back-barrier polarization-generating layer forming a heterojunction with a lower surface of the channel layer. The channel layer has disposed therein a predetermined n-type conductive dopant.

Abstract: A transmission line structure having a pair of separated coplanar waveguide transmissions line section. A coupling circuit is coupled between the pair of coplanar waveguide transmissions line sections, the coupling circuit suppresses common mode signals therein and passes, substantially unsuppressed, differential mode signal transmission between the pair of coplanar waveguide transmissions line sections.

Abstract: A microwave structure having an input section for receiving both a common mode signal and a CPW differential mode signal; an output section; and a CPW transmission line, having a center conductor disposed between a pair of coplanar ground plane conductors, connected between the input section and the output section. The conductors of the CPW transmission line are configured to provide the common mode signal a different attenuation in passing to the output section than the CPW transmission line provides to the differential mode signal passing between the input section and the output section.

Abstract: A monolithic microwave integrated circuit structure having a semiconductor substrate structure with a plurality of active devices and a microwave transmission line having an input section, an output section and a interconnecting section electrically interconnecting the active devices on one surface and a metal layer on an opposite surface overlaying the interconnection section and absent from overlaying at least one of the input section and the output section.

Abstract: A monolithic microwave integrated circuit structure having a semiconductor substrate structure with a plurality of active devices and a microwave transmission line having an input section, an output section and a interconnecting section electrically interconnecting the active devices on one surface and a metal layer on an opposite surface overlaying the interconnection section and absent from overlaying at least one of the input section and the output section.