Techniques are disclosed for forming transistor devices having reduced parasitic contact resistance relative to conventional devices. The techniques can be implemented, for example, using a standard contact stack such as a series of metals on, for example, silicon or silicon germanium (SiGe) source/drain regions. In accordance with one example such embodiment, an intermediate boron doped germanium layer is provided between the source/drain and contact metals to significantly reduce contact resistance. Numerous transistor configurations and suitable fabrication processes will be apparent in light of this disclosure, including both planar and non-planar transistor structures (e.g., FinFETs), as well as strained and unstrained channel structures. Graded buffering can be used to reduce misfit dislocation. The techniques are particularly well-suited for implementing p-type devices, but can be used for n-type devices if so desired.

A transistor device is provided that comprises a base structure, and a superlattice structure overlying the base structure and comprising a multichannel ridge having sloping sidewalls. The multichannel ridge comprises a plurality of heterostructures that each form a channel of the multichannel ridge, wherein a parameter of at least one of the heterostructures is varied relative to other heterostructures of the plurality of heterostructures. The transistor device further comprises a three-sided gate contact that wraps around and substantially surrounds the top and sides of the multichannel ridge along at least a portion of its depth.

A semiconductor device includes a buffer layer formed with a semiconductor adapted to produce piezoelectric polarization, and a channel layer stacked on the buffer layer, wherein a two-dimensional hole gas, generated in the channel layer by piezoelectric polarization of the buffer layer, is used as a carrier of the channel layer. On a complementary semiconductor device, the semiconductor device described above and an n-type field effect transistor are formed on the same compound semiconductor substrate. Also, a level shift circuit is manufactured by using the semiconductor device. Further, a semiconductor device manufacturing method includes forming a compound semiconductor base portion, forming a buffer layer on the base portion, forming a channel layer on the buffer layer, forming a gate on the channel layer, and forming a drain and source with the gate therebetween on the channel layer.

A high bandgap Schottky contact layer device and methods for producing same are provided herein. According to one aspect, a high bandgap Schottky contact layer device comprises a substrate, a first Schottky layer over the substrate, the first Schottky layer having a first bandgap, and a second Schottky layer over the first Schottky layer, the second Schottky layer having a second bandgap. The device further comprises a first metal contact over the second Schottky layer and at least one ohmic contact, a portion of which being in direct contact with the substrate. The first bandgap is greater than 1.7 electronvolts (eV). In one embodiment, the second bandgap is also greater than 1.7 eV.

A field effect transistor includes a substrate; a first semiconductor layer, disposed over the substrate; a second semiconductor layer, disposed over the first semiconductor layer, wherein an interface between the first semiconductor layer and the second semiconductor layer has a two-dimensional electron gas; a p+ III-V semiconductor layer, disposed over the second semiconductor layer; and a depolarization layer, disposed between the second semiconductor layer and the p+ III-V semiconductor layer, wherein the depolarization layer includes a metal oxide layer.

Embodiments include high electron mobility transistors (HEMTs) comprising a substrate and a barrier layer including a doped component. The doped component may be a germanium doped layer or a germanium doped pulse. Other embodiments may include methods for fabricating such a HEMT.

A layer structure and method of fabrication of a semiconductor heterostructure containing a two-dimensional electron gas (2DEG), two-dimensional hole gas (2DHG), or a two-dimensional electron/hole gas (2DEHG). The heterostructure contains a quantum well layer with 2DEG, 2DHG, or 2DEHG embedded between two doped charge reservoir layers and at least two remote charge reservoir layers. Such scheme allows reducing the number of scattering ions in the proximity of the quantum well as well a possibility for a symmetric potential for the electron or hole wavefunction in the quantum well, leading to significant improvement in carrier mobility in a broad range of 2DEG or 2DHG concentration in the quantum well. Embodiments of the invention may be applied to the fabrication of galvano-magnetic sensors, HEMT, pHEMT, and MESFET devices.

Techniques are disclosed for forming transistor devices having source and drain regions with high concentrations of boron doped germanium. In some embodiments, an in situ boron doped germanium, or alternatively, boron doped silicon germanium capped with a heavily boron doped germanium layer, are provided using selective epitaxial deposition in the source and drain regions and their corresponding tip regions. In some such cases, germanium concentration can be, for example, in excess of 50 atomic % and up to 100 atomic %, and the boron concentration can be, for instance, in excess of 1E20 cm.sup.3. A buffer providing graded germanium and/or boron concentrations can be used to better interface disparate layers. The concentration of boron doped in the germanium at the epi-metal interface effectively lowers parasitic resistance without degrading tip abruptness. The techniques can be embodied, for instance, in planar or non-planar transistor devices.

A heterostructure field effect transistor (HFET) gallium nitride (GaN) semiconductor power device comprises a hetero-junction structure comprises a first semiconductor layer interfacing a second semiconductor layer of two different band gaps thus generating an interface layer as a two-dimensional electron gas (2DEG) layer. The power device further comprises a source electrode and a drain electrode disposed on two opposite sides of a gate electrode disposed on top of the hetero-junction structure for controlling a current flow between the source and drain electrodes in the 2DEG layer. The power device further includes a floating gate located between the gate electrode and hetero-junction structure, wherein the gate electrode is insulated from the floating gate with an insulation layer and wherein the floating gate is disposed above and padded with a thin insulation layer from the hetero-junction structure and wherein the floating gate is charged for continuously applying a voltage to the 2DEG layer to pinch off the current flowing in the 2DEG layer between the source and drain electrodes whereby the HFET semiconductor power device is a normally off device.

The present application provides a semiconductor structure. The semiconductor structure includes a channel layer and a barrier layer provided on the channel layer. The barrier layer includes multiple barrier layers arranged in a stack, the multiple barrier sub-layers include at least three barrier sub-layers, and Al component proportions of the multiple barrier sub-layers vary along a growth direction of the barrier layer for at least one up-and-down fluctuation.