Abstract: Provided is a collagen sponge which has compressive strength (stress) equivalent to that of a tissue into which the collagen sponge is to be implanted, has no unevenness in structure and stress, and has a pore structure for allowing cells to infiltrate thereinto. The collagen sponge is obtained by subjecting a collagen dispersion, a collagen solution, or a mixture thereof having a collagen concentration of 50 mg/ml or more to freeze-drying and insolubilization treatment thereafter. The collagen sponge thus obtained has a stress of from 10 kPa to 30 kPa when loaded with 10% strain, has in its surface and inside a pore structure having a mean pore diameter ranging from 50 ?m to 400 ?m, and has a pore diameter standard deviation equal to or less than 80% of the mean pore diameter.

Abstract: A method of manufacturing a semiconductor device according to one aspect of the present invention includes a step of forming a first layer of InAlN, a step of forming a second layer of InAlGaN on the first layer under a growth temperature higher than that of the first layer, and a step of forming a third layer of GaN, AlGaN or InGaN under a growth temperature higher than that of the first layer.

Abstract: A GaN device suppressing the instantaneous current reduction after the shut-off of a high frequency signal is disclosed. The GaN device provides, on a SiC substrate, an AlN layer, a GaN layer, and an AlGaN layer, The SiC substrate has an energy difference greater than 0.67 eV but less than 1.43 eV; the AlN layer has a thickness less than 50 nm; and the GaN layer has a thickness less than 1.5 ?m.

Abstract: A method to produce a nitride semiconductor device is disclosed, The method includes a step to grow sequentially, on a substrate, an AlN layer, a AlGaN layer with the Al composition not less than 2.5% but not greater than 9%, a GaN layer with a thickness not less than 250 nm but not greater than 1400 nm. A feature of the process is that, after the growth of the AlGaN layer but before the growth of the GaN layer, at least the source gases for the group III elements are interrupted to be supplied for a period of not less than 80 seconds but not longer than 220 seconds.

Abstract: A process to obtain a nitride transistor containing a gallium nitride (GaN) is disclosed. The process first grows an AlN layer on a substrate, then crown the GaN layer cc the AlN layer. Between the growth of the AlN layer and the GaN layer, the process leaves the AlN layer grown art the substrate in a temperature higher than the growth temperature of the AlN layer for a preset period. This heat treatment of the AlN layer sublimates impurities accumulated on the surface of the AlN layer and enhances the crystal quality of the GaN layer grown thereon.

Abstract: A method of manufacturing a semiconductor device according to one aspect of the present invention includes a step of forming a first layer of InAlN, a step of forming a second layer of InAlGaN on the first layer under a growth temperature higher than that of the first layer, and a step of forming a third layer of GaN, AlGaN or InGaN under a growth temperature higher than that of the first layer.

Abstract: A semiconductor device is provided, which includes a barrier layer 14 formed on a substrate 10 and made of InxAlyGa1-x-yN, a channel layer 16 formed on the barrier layer and made of GaN or InGaN, an electron supplying layer 18 formed on the channel layer and made of AlGaN, InAlN, or InAlGaN, and a gate electrode and ohmic electrodes 24 and 26 formed on the electron supplying layer. Relations between x and y for the barrier layer of x>0, y>0, x+y?1, and 0.533x<y<4.20x are satisfied.

Abstract: The semiconductor device includes a SiC substrate; an aluminum nitride layer provided on the substrate and having an island-shaped pattern consisting of plural islands: a channel layer provided on the AlN layer and comprising a nitride semiconductor; an electron supplying layer provided on the channel layer and having a band gap larger than that of the channel layer; and a gate, source and drain electrodes on the electron supply layer. The AlN layer has an area-averaged circularity Y/X of greater than 0.2. Y is a sum of values obtained by multiplying circularities of the plural islands by areas of the plural islands respectively, X is a sum of the areas of the plural islands. The circularity are calculated by a formula of (4?×area)/(length of periphery)2 where the area and the length of periphery are an area and a length of periphery of each island.

Abstract: A method of manufacturing a semiconductor device includes growing a first GaN layer on a SiC substrate, and forming a second GaN layer on the first GaN layer, the second GaN layer being grown under such conditions that a ratio of a vertical growth rate to a horizontal growth rate is lower than that in the growth of the first GaN layer.

Abstract: A method for fabricating a semiconductor device includes performing thermal cleaning for a surface of a silicon substrate in an atmosphere including hydrogen under a condition that a thermal cleaning temperature is higher than or equal to 700° C. and is lower than or equal to 1060° C., and a thermal cleaning time is longer than or equal to 5 minutes and is shorter than or equal to 15 minutes; forming a first AlN layer on the substrate with a first V/III source ratio, the forming of the first AlN layer including supplying an Al source to the surface of the substrate without supplying a N source, and supplying both the Al source and the N source; forming a second AlN layer on the first AlN layer with a second V/III source ratio that is greater than the first ratio; and forming a GaN-based semiconductor layer on the second AlN layer.

Abstract: A method of manufacturing a semiconductor device according to one aspect of the present invention includes a step of forming a first layer of InAlN, a step of forming a second layer of InAlGaN on the first layer under a growth temperature higher than that of the first layer, and a step of forming a third layer of GaN, AlGaN or InGaN under a growth temperature higher than that of the first layer.

Abstract: A semiconductor device according to an embodiment of the present invention includes a SiC substrate, an AlN layer provided on the SiC substrate and having a maximum valley depth Rv of 5 nm or less in an upper surface, a channel layer provided on the AlN layer and composed of a nitride semiconductor, an electron supply layer provided on the channel layer and having a greater band gap than the channel layer, and a gate electrode, a source electrode and a drain electrode provided on the electron supply layer.

Abstract: The semiconductor device includes a SiC substrate; an aluminum nitride layer provided on the substrate and having an island-shaped pattern consisting of plural islands: a channel layer provided on the AlN layer and comprising a nitride semiconductor; an electron supplying layer provided on the channel layer and having a band gap larger than that of the channel layer; and a gate, source and drain electrodes on the electron supply layer. The AlN layer has an area-averaged circularity Y/X of greater than 0.2. Y is a sum of values obtained by multiplying circularities of the plural islands by areas of the plural islands respectively, X is a sum of the areas of the plural islands. The circularity are calculated by a formula of (4?×area)/(length of periphery)2 where the area and the length of periphery are an area and a length of periphery of each island.

Abstract: A GaN device suppressing the instantaneous current reduction after the shut-off of a high frequency signal is disclosed. The GaN device provides, on a SiC substrate, an AlN layer, a GaN layer, and an AlGaN layer. The SiC substrate has an energy difference greater than 0.67 eV but less than 1.43 eV; the AlN layer has a thickness less than 50 nm; and the GaN layer has a thickness less than 1.

Abstract: A semiconductor device includes a Si substrate having a principal plane that is a crystal surface inclined at an off angle of 0.1 degrees or less with respect to a (111) plane, an AlN layer that is provided so as to contact the principal plane of the Si substrate and is configured so that an FWHM of a rocking curve of a (002) plane by x-ray diffraction is not greater than 2000 seconds, and a GaN-based semiconductor layer formed on the AlN layer.

Abstract: A method for fabricating a semiconductor device includes: forming a GaN-based semiconductor layer on a substrate; forming a gate insulating film of aluminum oxide on the GaN-based semiconductor layer at a temperature equal to or lower than 450° C.; forming a protection film on an upper surface of the gate insulating film; performing a process with an alkaline solution in a state in which the upper surface of the gate insulating film is covered with the protection film; and forming a gate electrode on the gate insulating film.

Abstract: A semiconductor device includes an AlGaN layer that is provided on a SiC substrate and has an acceptor concentration equal to or higher than a donor concentration, a GaN layer provided on the AlGaN layer, and an electron supply layer that is provided on the GaN layer and has a band gap greater than that of GaN.

Abstract: A semiconductor device includes a first GaN layer provided on a SiC substrate, a second GaN layer provided on the first GaN layer, and an electron supply layer that is provided on the second GaN layer and has a band gap greater than that of GaN, the first GaN layer having an acceptor concentration higher than that of the second GaN layer.

Abstract: There are provided a semiconductor device that includes a bypass protection unit against surge voltage or the like, achieves good withstand voltage characteristics and low on-resistance (low On-state voltage), has a simple structure, and is used for large-current purpose and a method for producing the semiconductor device. In the present invention, the semiconductor device includes an n+-type GaN substrate 1 having a GaN layer that is in ohmic contact with a supporting substrate, a FET having an n?-type GaN drift layer 2 in a first region R1, and an SBD having an anode electrode in a second region R2, the anode electrode being in Schottky contact with the n?-type GaN drift layer 2. The FET and the SBD are arranged in parallel. A drain electrode D of the FET and a cathode electrode C of the SBD are formed on the back of the n+-type GaN substrate 1.

Abstract: A semiconductor substrate includes an AlN layer that is formed so as to contact a Si substrate and has an FWMH of a rocking curve of a (002) plane by x-ray diffraction, the FWMH being less than or equal to 1500 seconds, and a GaN-based semiconductor layer formed on the AlN layer.