Abstract: Provided is an epitaxial substrate capable of achieving a semiconductor device that has excellent ohmic contact characteristics as well as satisfactory device characteristics. On a base substrate, a channel layer formed of a first group III nitride that contains at least Al and Ga and has a composition of Inx1Aly1Gaz1N (x1+y1+z1=1) is formed. On the channel layer, a barrier layer formed of a second group III nitride that contains at least In and Al and has a composition of Inx2Aly2Gaz2N (x2+y2+z2=1) is formed such that an In composition ratio of a near-surface portion is larger than an In composition ratio of a portion other than the near-surface portion.

Abstract: An epitaxial substrate, in which a group of group-III nitride layers is formed on a single-crystal silicon substrate so that a crystal plane is approximately parallel to a substrate surface, comprises: a first group-III nitride layer formed of AlN on the base substrate; a second group-III nitride layer formed of InxxAlyyGazzN (xx+yy+zz=1, 0?xx?1, 0<yy?1 and 0<zz?1) on the first group-III nitride layer; and at least one third group-III nitride layer epitaxially-formed on the second group-III nitride layer, wherein: the first group-III nitride layer is a layer containing multiple defects including at least one type of a columnar crystal, a granular crystal, a columnar domain and a granular domain; and an interface between the first group-III nitride layer and the second group-III nitride layer is a three-dimensional asperity surface.

Abstract: A semiconductor device made of a group-III nitride semiconductor having excellent properties is provided. The semiconductor device has a horizontal diode structure of Schottky type or P-N junction type, or combined type thereof having a main conduction pathway in the horizontal direction in a conductive layer with unit anode portions and unit cathode electrodes being integrated adjacently to each other in the horizontal direction. The conductive layer is preferably formed by depositing a group-III nitride layer and generating a two-dimensional electron gas layer on the interface. Forming the conductive layer of the group-III nitride having high breakdown field allows the breakdown voltage to be kept high while the gap between electrodes is narrow, which achieves a semiconductor device having high output current per chip area.

Abstract: A buffer layer formed of Inx1Aly1Gaz1N formed on a base, with an upper part of the buffer layer containing columnar polycrystalline including a grain boundary existing in a direction substantially perpendicular to a surface of the base. The number of grain boundaries in the lower part of the buffer layer is greater than that in the upper part, and a full width at half maximum of an X-ray rocking curve of the upper part is 300-3000 seconds, RMS of the surface of the buffer layer is 0.2 nm-6 nm, and the ratio of the grain boundary width of the crystal grain of the upper part in a direction parallel to the base surface to the formation thickness of the buffer layer is 0.5-1.5.

Abstract: Provided is an epitaxial substrate for semiconductor device that is capable of achieving a semiconductor device having high reliability in reverse characteristics of schottky junction. An epitaxial substrate for semiconductor device obtained by forming, on a base substrate, a group of group III nitride layers by lamination such that a (0001) crystal plane of each layer is approximately parallel to a substrate surface includes: a channel layer formed of a first group III nitride having a composition of Inx1Aly1Gaz1N (x1+y1+z1=1, z1>0); and a barrier layer formed of a second group III nitride having a composition of Inx2Aly2N (x2+y2=1, x2>0, y2>0), wherein the second group III nitride is a short-range-ordered mixed crystal having a short-range order parameter ? satisfying a range where 0???1.

Abstract: Provided is an epitaxial substrate capable of achieving a semiconductor device that has excellent schottky contact characteristics as well as satisfactory device characteristics. On a base substrate, a channel layer formed of a first group III nitride that contains at least Al and Ga and has a composition of Inx1Aly1Gaz1N (x1+y1+z1=1) is formed. On the channel layer, a barrier layer formed of a second group III nitride that contains at least In and Al and has a composition of Inx2Aly2Gaz2N (x2+y2+z2=1) is formed such that an In composition ratio of a near-surface portion is smaller than an In composition ratio of a portion other than the near-surface portion.

Abstract: Provided is an epitaxial substrate capable of achieving a semiconductor device that has excellent ohmic contact characteristics as well as satisfactory device characteristics. On a base substrate, a channel layer formed of a first group III nitride that contains at least Al and Ga and has a composition of Inx1Aly1Gaz1N (x1+y1+z1=1) is formed. On the channel layer, a barrier layer formed of a second group III nitride that contains at least In and Al and has a composition of Inx2Aly2Gaz2N (x2+y2+z2=1) is formed such that an In composition ratio of a near-surface portion is larger than an In composition ratio of a portion other than the near-surface portion.

Abstract: Provided is an epitaxial substrate having excellent two-dimensional electron gas characteristics and reduced internal stress due to strains. A channel layer is formed of a first group III nitride represented by Inx1Aly1Gaz1N (x1+y1+z1=1) so as to have a composition in a range determined by x1=0 and 0?y1?0.3. A barrier layer is formed of a second group III nitride represented by Inx2Aly2Gaz2N (x2+y2+z2=1) so as to have a composition, in a ternary phase diagram with InN, AlN and GaN being vertices, in a range surrounded by five straight lines determined in accordance with the composition (AlN molar fraction) of the first group III nitride.

Abstract: Provided is an epitaxial substrate capable of manufacturing a HEMT device that has excellent two-dimensional electron gas characteristics and is capable of performing normally-off operation. A channel layer is formed of a first group III nitride represented by Inx1Aly1Gaz1N (x1+y1+z1=1) so as to have a composition in a range determined by x1=0 and 0?y1?0.3. A barrier layer is formed of a second group III nitride represented by Inx2Aly2Gaz2N (x2+y2+z2=1) so as to have a composition, in a ternary phase diagram with InN, AlN and GaN being vertices, in a range surrounded by four straight lines determined in accordance with the composition (AlN molar fraction) of the first group III nitride and to have a thickness of 5 nm or less.

Abstract: An underlying film 2 of a group III nitride is formed on a substrate 1 by vapor phase deposition. The substrate 1 and the underlying film 2 are subjected to heat treatment in the present of hydrogen to remove the underlying film 2 so that the surface of the substrate 1 is roughened. A seed crystal film 4 of a group III nitride single crystal is formed on a surface of a substrate 1A by vapor phase deposition. A group III nitride single crystal 5 is grown on the seed crystal film 4 by flux method.

Abstract: A buffer layer formed of Inx1Aly1Gaz1N formed on a base, with an upper part of the buffer layer containing columnar polycrystalline including a grain boundary existing in a direction substantially perpendicular to a surface of the base. The number of grain boundaries in the lower part of the buffer layer is greater than that in the upper part, and a full width at half maximum of an X-ray rocking curve of the upper part is 300-3000 seconds, RMS of the surface of the buffer layer is 0.2 nm-6 nm, and the ratio of the grain boundary width of the crystal grain of the upper part in a direction parallel to the base surface to the formation thickness of the buffer layer is 0.5-1.5.

Abstract: A semiconductor device made of a group-III nitride semiconductor having excellent properties is provided. The semiconductor device has a horizontal diode structure of Schottky type or P—N junction type, or combined type thereof having a main conduction pathway in the horizontal direction in a conductive layer with unit anode portions and unit cathode electrodes being integrated adjacently to each other in the horizontal direction. The conductive layer is preferably formed by depositing a group-III nitride layer and generating a two-dimensional electron gas layer on the interface. Forming the conductive layer of the group-III nitride having high breakdown field allows the breakdown voltage to be kept high while the gap between electrodes is narrow, which achieves a semiconductor device having high output current per chip area.

Abstract: A semiconductor device having small leakage current and high breakdown voltage during reverse blocking, small on-state resistance and large output current at forward conduction, short reverse recovery time at shutoff, and high peak surge current value is provided. An n-type layer is made of a group-III nitride, and a p-type layer is made of a group-IV semiconductor material having a smaller band gap than the group-III nitride. The energy level at the top of the valence band of the n-type layer is lower than the energy level at the top of the valence band of the p-type layer, so that a P—N junction semiconductor device satisfying the above requirements is obtained. Further, a combined structure of P—N junction and Schottky junction by additionally providing an anode electrode to be in Schottky contact with the n-type layer also achieves the effect of decreasing voltage at the rising edge of current resulting from the Schottky junction.