Embodiments are directed to high electron mobility transistor (HEMT) devices and methods. One such HEMT device includes a substrate having a first surface, and first and second heterostructures on the substrate and facing each other. Each of the first and second heterostructures includes a first semiconductor layer on the first surface of the substrate, a second semiconductor layer on the first surface of the substrate, and a two-dimensional electrode gas (2DEG) layer between the first and second semiconductor layers. A doped semiconductor layer is disposed between the first and second heterostructures, and a source contact is disposed on the first heterostructure and the second heterostructure.

A method for fabricating high electron mobility transistor (HEMT) includes the steps of: forming a buffer layer on a substrate; forming a patterned mask on the buffer layer; using the patterned mask to remove the buffer layer for forming ridges and a damaged layer on the ridges; removing the damaged layer; forming a barrier layer on the ridges; and forming a p-type semiconductor layer on the barrier layer.

A semiconductor device includes a first nitride-based semiconductor layer, a second nitride-based semiconductor layer, a group of negatively-charged ions, and a field plate. The gate electrode and the drain electrode disposed above the second nitride-based semiconductor layer to define a drift region therebetween. The group of negatively-charged ions are implanted into the drift region and spaced apart from an area directly beneath the gate and drain electrodes to form at least one high resistivity zone in the second nitride-based semiconductor layer. The field plate is disposed over the gate electrode and extends in a region between the gate electrode and the high resistivity zone.

A semiconductor device is provided and includes a substrate and a stack on the substrate. The stack includes plural active layers that are vertically stacked and spaced apart from each other, and plural gate electrodes that are on the active layers, respectively, and vertically stacked. Each active layer includes a channel layer under a corresponding one of the gate electrodes, and a source/drain layer disposed at a side of the channel layer and electrically connected to the channel layer. The channel layer is made of a two-dimensional atomic layer of a first material.

Embodiments herein describe techniques, systems, and method for a semiconductor device. A semiconductor device may include isolation areas above a substrate to form a trench between the isolation areas. A first buffer layer is over the substrate, in contact with the substrate, and within the trench. A second buffer layer is within the trench over the first buffer layer, and in contact with the first buffer layer. A channel area is above the first buffer layer, above a portion of the second buffer layer that are below a source area or a drain area, and without being vertically above a portion of the second buffer layer. In addition, the source area or the drain area is above the second buffer layer, in contact with the second buffer layer, and adjacent to the channel area. Other embodiments may be described and/or claimed.

There is provided a semiconductor layer structure (100) comprising: a Si substrate (102) having a top surface (104); a first semiconductor layer (110) arranged on said substrate, the first semiconductor layer comprising a plurality of vertical nanowire structures (112) arranged perpendicularly to said top surface of said substrate, the first semiconductor layer comprising AlN; a second semiconductor layer (120) arranged on said first semiconductor layer laterally and vertically enclosing said nanowire structures, the second semiconductor layer comprising Al.sub.xGa.sub.1-xN, wherein 0≤x≤0.95; a third semiconductor layer (130) arranged on said second semiconductor layer, the third semiconductor layer comprising Al.sub.yGa.sub.1-yN, wherein 0≤y≤0.95; and a fourth semiconductor layer (140) arranged on said third semiconductor layer, the fourth semiconductor layer comprising GaN. There is also provided a high-electron-mobility transistor device and methods of producing such structures and devices.

A high electron mobility transistor (HEMT) and method for forming the same are disclosed. The high electron mobility transistor includes a substrate, a mesa structure disposed on the substrate, a passivation layer disposed on the mesa structure, and at least a contact structure disposed in the passivation and the mesa structure. The mesa structure includes a channel layer and a barrier layer disposed on the channel layer. The contact structure includes a body portion and a plurality of protruding portions. The body portion is through the passivation layer. The protruding portions connect to a bottom surface of the body portion and through the barrier layer and a portion of the channel layer.

This disclosure relates to bipolar transistors, such as heterojunction bipolar transistors, having increased collector thickness for improved ruggedness. In some embodiments, the collector thickness can be above 1.1 microns. The collector can have at least one doping concentration grading. The collector can have a high doping concentration at a junction between the collector and the sub-collector, such as at the high end of the grading. In some embodiments, the high doping concentration can be above about 9×10.sup.16 cm.sup.−3. The collector can include a region with high doping concentration adjacent the base. The collector can include a discontinuity in the doping concentration, such as at the low end of the grading. Such bipolar transistors can be implemented, for example, in power amplifiers.

This disclosure relates to bipolar transistors, such as heterojunction bipolar transistors, having increased collector thickness for improved ruggedness. In some embodiments, the collector thickness can be above 1.1 microns. The collector can have at least one doping concentration grading. The collector can have a high doping concentration at a junction between the collector and the sub-collector, such as at the high end of the grading. In some embodiments, the high doping concentration can be above about 9×10.sup.16 cm.sup.−3. The collector can include a region with high doping concentration adjacent the base. The collector can include a discontinuity in the doping concentration, such as at the low end of the grading. Such bipolar transistors can be implemented, for example, in power amplifiers.

According to one embodiment, a semiconductor device includes first to third electrodes, a semiconductor member, and a first insulating member. The third electrode is between the first and second electrodes. The semiconductor member includes first and second semiconductor regions. The first semiconductor region includes first to fifth partial regions. The fourth partial region is between the first and third partial regions. The fifth partial region is between the third and second partial regions. The second semiconductor region includes first and second semiconductor portions. The first insulating member includes first to third insulating regions. The fourth partial region includes a first facing region. The fifth partial region includes a second facing region. The first facing region includes a first element. The second facing region does not include the first element, or a concentration of the first element in the second facing region is lower than in the first facing region.