A III-N device includes a III-N layer structure including a III-N channel layer, a III-N barrier layer over the III-N channel layer, and a graded III-N layer over the III-N barrier layer having a first side adjacent to the III-N barrier layer and a second side opposite the first side; a first power electrode and a second power electrode; and a gate between the first and second power electrodes, the gate being over the III-N layer structure. A composition of the graded III-N layer is graded so the bandgap of the graded III-N layer adjacent to the first side is greater than the bandgap of the graded III-N layer adjacent to the second side. A region of the graded III-N layer is (i) between the gate and the second power electrode, and (ii) electrically connected to the first power electrode and electrically isolated from the second power electrode.

A semiconductor structure (100) comprising: a substrate (102), a first layer (106) of Al.sub.xGa.sub.yIn.sub.(1-x-y)N disposed on the substrate, stacks (107, 109) of several second and third layers (108, 110) alternating against each other, between the substrate and the first layer, a fourth layer (112) of Al.sub.xGa.sub.yIn.sub.(1-x-y)N, between the stacks, a relaxation layer of AIN disposed between the fourth layer and one of the stacks, and, in each of the stacks: the level of Ga of the second layers increases from one layer to the next in a direction from the substrate to the first layer, the level of Ga of the third layers is constant or decreasing from one layer to the next in said direction, the average mesh parameter of each group of adjacent second and third layers increasing from one group to the next in said direction, the thickness of the second and third layers is less than 5 nm.

A high electron mobility transistor (HEMT) includes a substrate, a P-type III-V composition layer, a gate electrode and a carbon containing layer. The P-type III-V composition layer is disposed on the substrate, and the gate electrode is disposed on the P-type III-V composition layer. The carbon containing layer is disposed under the P-type III-V composition layer to function like an out diffusion barrier for preventing from the dopant within the P-type III-V composition layer diffusing into the stacked layers underneath during the annealing process.

A semiconductor device including: a substrate in which a first transistor region and a second transistor region are provided; a first channel layer in which a carrier of a first conductivity type travels, the first channel layer being provided over the substrate in the first transistor region and including a compound semiconductor; a first impurity epitaxial layer of a second conductivity type that is provided over the substrate with the first channel layer interposed therebetween, is disposed in a first gate region in a central portion and outside the first gate region, and has a low concentration region in which an electric charge amount per unit length is small as compared to the first gate region; and a second channel layer in which a carrier of the second conductivity type travels, the second channel layer being provided over the substrate in the second transistor region and including a compound semiconductor.

The disclosure provides a high ruggedness HBT structure, including: a sub-collector layer on a substrate and formed of an N-type III-V semiconductor material; a collector layer on the sub-collector layer and formed of a III-V semiconductor material; a base layer on the collector layer and formed of a P-type III-V semiconductor material; an emitter layer on the base layer and formed of one of N-type semiconductor materials of InGaP, InGaAsP and InAlGaP; a first emitter cap layer on the emitter layer and formed of one of undoped or N-type semiconductor materials of Al.sub.xGa.sub.1-xAs, Al.sub.xGa.sub.1-xAs.sub.1-yN.sub.y, Al.sub.xGa.sub.1-xAs.sub.1-zP.sub.z, Al.sub.xGa.sub.1-xAs.sub.1-wSb.sub.w, and In.sub.rAl.sub.xGa.sub.1-x-rAs, x having a highest value between 0.05≤x≤0.4, and y, z, r, w≤0.1; a second emitter cap layer on the first emitter cap layer and formed of an N-type III-V semiconductor material; and an ohmic contact layer on the second emitter cap layer and formed of an N-type III-V semiconductor material.

Structures including a buffer layer and methods of forming a structure including a buffer layer. A layer stack is formed on a semiconductor substrate. The layer stack includes a buffer layer and a charge-trapping layer. The buffer layer is composed of a III-V compound semiconductor material, and the charge-trapping layer is positioned between the semiconductor substrate and the buffer layer.

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. In a complementary semiconductor device, the semiconductor device described above and an n-type field effect transistor are formed on the same compound semiconductor substrate. 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 date on the channel layer, and forming a drain and source with the gate therebetween on the channel layer.

A process of forming a field effect transistor (FET) of a type of high electron mobility transistor (HEMT) reducing damages caused in a semiconductor layer is disclosed. The process carries out steps of: (a) depositing an insulating film on a semiconductor stack; (b) depositing a conductive film on the insulating film; (c) forming an opening in the conductive film and the insulating film by a dry-etching using ions of reactive gas to expose a surface of the semiconductor stack; and (d) forming a gate electrode to be in contact with the surface of the semiconductor stack through the opening, the gate electrode filling the opening in the conductive film and the insulating film.

A semiconductor crystal substrate includes a crystal substrate that is formed of a material including GaSb or InAs, a first buffer layer that is formed on the crystal substrate and formed of a material including GaSb, the first buffer layer having n-type conductivity, and a second buffer layer that is formed on the first buffer layer and formed of a material including GaSb, the second buffer layer having p-type conductivity.

A semiconductor crystal substrate includes a crystal substrate that is formed of a material including GaSb or InAs, a first buffer layer that is formed on the crystal substrate and formed of a material including GaSb, the first buffer layer having n-type conductivity, and a second buffer layer that is formed on the first buffer layer and formed of a material including GaSb, the second buffer layer having p-type conductivity.