Abstract: There is provided a nitride crystal substrate made of a nitride crystal with a diameter of 100 mm or more, having on its main surface: a continuous high dislocation density region and a plurality of low dislocation density regions divided by the high dislocation density region, with the main surface not including a polarity inversion domain.

Abstract: An object of the present invention is to improve quality of a group-III nitride crystal, and also improve performance and manufacturing yield of a semiconductor device manufactured using the crystal. Provided is a nitride crystal represented by the composition formula of InxAlyGa1-x-yN (satisfying 0?x?1, 0?y?1, 0?x+y?1), with a hardness exceeding 22.0 GPa as measured by a nanoindentation method using an indenter with a maximum load applied thereto being within a range of 1 mN or more and 50 mN or less.

Abstract: An object of the present invention is to improve quality of a nitride crystal, and also improve performance and manufacturing yield of a semiconductor device manufactured using the crystal. Provided is a nitride crystal in which a composition formula is represented by InxAlyGa1-x-yN (satisfying 0?x?1, 0?y?1, 0?x+y?1), and the concentration of B in the crystal is less than 1×1015 at/cm3, and each of the concentrations of O and C in the crystal is less than 1×1015 at/cm3 in a region of 60% or more of a main surface.

Abstract: A nitride semiconductor substrate is manufactured by a method which includes growing nitride semiconductor crystal along a c-axis direction on a +C-plane of a seed crystal substrate formed of nitride semiconductor crystal to form an n?-type first nitride semiconductor layer; growing the nitride semiconductor crystal along the c-axis direction on the +C-plane of the first nitride semiconductor layer to form a second nitride semiconductor layer; and removing the seed crystal substrate and exposing a ?C-plane of the first nitride semiconductor layer to obtain as a semiconductor substrate a laminate of the first nitride semiconductor layer and the second nitride semiconductor layer, with the ?C plane as a main surface.

Abstract: A clock generation circuit, which generates an output clock using an external clock as a target clock, includes a circuit arranged to change the output clock to high level in synchronization with an up edge of the target clock, circuits arranged to generate first and second ramp voltages with a period of interval between neighboring up edges of the target clock, and a circuit arranged to hold a comparison voltage corresponding to a second ramp voltage when an up edge of the target clock occurs. The level of the output clock is changed from high level to low level based on a comparison result between the first ramp voltage and the comparison voltage.

Abstract: There is provided a method of manufacturing a crystal substrate, including: preparing a first crystal body which is a substrate comprising a single crystal of group III nitride produced by a vapor phase method and having a first main surface, and in which c-plane of the single crystal is curved in a concave spherical shape with a predetermined curvature; and growing a second crystal body comprising a single crystal of group III nitride on the first main surface, in a mixed melt containing an alkali metal and a group III element.

Abstract: To provide a technique of increasing a radius of curvature of (0001) plane, and narrowing an off-angle distribution, there is provided a nitride semiconductor substrate containing a group III nitride semiconductor crystal and having a main surface in which a nearest low index crystal plane is (0001) plane, wherein (0001) plane in one of a direction along <1-100> axis and a direction along <11-20> axis orthogonal to the <1-100> axis, is curved in a concave spherical shape with respect to the main surface, and a radius of curvature of the (0001) plane in one of the direction along the <1-100> axis and the direction along the <11-20> axis orthogonal to the <1-100> axis is different from a radius of curvature of at least a part of the (0001) plane in the other direction.

Abstract: A method for manufacturing a group III nitride semiconductor crystal substrate includes providing, as a seed crystal substrate, a group III nitride single crystal grown by a liquid phase growth method, and homoepitaxially growing a group III nitride single crystal by a vapor phase growth method on a principal surface of the seed crystal substrate. The principal surface of the seed crystal substrate is a +c-plane, and the seed crystal substrate has an atomic oxygen concentration of not more than 1×1017 cm?3 in a crystal near the principal surface over an entire in-plane region thereof.

Abstract: There is provided a method for manufacturing a group-III nitride substrate, including: (a) preparing a substrate which is made of a group III-nitride crystal and which has a high oxygen concentration domain where an oxygen concentration is higher than that of a matrix of the crystal; (b) irradiating the substrate with laser beam aiming at the high oxygen concentration domain, forming a through-hole penetrating the substrate in a thickness direction, and removing at least a part of the high oxygen concentration domain from the substrate; and (c) embedding at least a part of an inside of the through-hole by growing the group-III nitride crystal in the through-hole.

Abstract: There is provided a nitride crystal substrate made of a nitride crystal with a diameter of 100 mm or more, having on its main surface: a continuous high dislocation density region and a plurality of low dislocation density regions divided by the high dislocation density region, with the main surface not including a polarity inversion domain.

Abstract: A large Group III nitride crystal of high quality with few defects such as a distortion, a dislocation, and warping is produced by vapor phase epitaxy. A method for producing a Group III nitride crystal includes: a first Group III nitride crystal production process of producing a first Group III nitride crystal 1003 by liquid phase epitaxy; and a second Group III nitride crystal production process of producing a second Group III nitride crystal 1004 on the first crystal 1003 by vapor phase epitaxy. In the first Group III nitride crystal production process, the surfaces of seed crystals 1003a (preliminarily provided Group III nitride) are brought into contact with an alkali metal melt, a Group III element and nitrogen are cause to react with each other in a nitrogen-containing atmosphere in the alkali metal melt, and the Group III nitride crystals are bound together by growth of the Group III nitride crystals grown from the seed crystals 1003a to produce a first crystal 1003.

Abstract: There is provided a method for manufacturing a nitride crystal substrate, including: arranging a plurality of seed crystal substrates made of a nitride crystal in a planar appearance, so that their main surfaces are parallel to each other and their lateral surfaces are in contact with each other; growing a first crystal film using a vapor-phase growth method on a surface of the plurality of seed crystal substrates arranged in the planar appearance, and preparing a combined substrate formed by combining the adjacent seed crystal substrates each other by the first crystal film; growing a second crystal film using a liquid-phase growth method on a main surface of the combined substrate so as to be embedded in a groove that exists at a combined part of the seed crystal substrates, and preparing a substrate for crystal growth having a smoothened main surface; and growing a third crystal film using the vapor-phase growth method, on the smoothed main surface of the substrate for crystal growth.

Abstract: A semiconductor substrate manufacturing method includes: epitaxially growing a columnar III nitride semiconductor single crystal on a principal place of a circular substrate; removing a hollow cylindrical region at an outer peripheral edge side of the III nitride semiconductor single crystal to leave a solid columnar region at an inside of the hollow cylindrical region of the III nitride semiconductor single crystal; and slicing the solid columnar region after removing the hollow cylindrical region. The hollow cylindrical region is removed such that the shape of the III nitride semiconductor single crystal is always keeps an axial symmetry that a center axis of the III nitride semiconductor single crystal is defined as a symmetric axis.

Abstract: A nitride semiconductor single crystal substrate manufacturing method includes providing a template that a first nitride semiconductor single crystal layer is hetero-epitaxially grown on a heterogeneous substrate, forming a plurality of linear grooves on a surface of the template that have a depth reaching an inside of the heterogeneous substrate, wherein a pattern of the plurality of the linear grooves has three-fold or six-fold rotational symmetry with respect to a central axis of the template, epitaxially growing a second nitride semiconductor single crystal layer on the template with the plurality of the linear grooves formed thereon, and cutting a nitride semiconductor single crystal substrate from the second nitride semiconductor single crystal layer.

Abstract: A DC/DC converter has: a soft-start circuit, a variable output current generator, a constant current source, an oscillator, a slope circuit, a PWM comparator, and a control circuit operable to turn ON and OFF first and second transistors alternately based on a pulse width modulation signal. Through the switching operation of the first and second transistors, an input voltage is converted into a output voltage.

Abstract: There is provided a method for manufacturing a group III nitride substrate, including: preparing a plurality of seed crystal substrates formed into shapes that can be arranged with side surfaces opposed to each other; bonding the plurality of seed crystal substrates on a base material by an adhesive agent in an appearance that the seed crystal substrates are arranged with the side surfaces opposed to each other; growing a group III nitride crystals above main surfaces of the plurality of seed crystal substrates, so that crystals grown on each main surface are integrally combined each other; and obtaining a group III nitride substrate formed of the group III nitride crystal.

Abstract: There is provided a method for manufacturing a group-III nitride substrate, including: (a) preparing a substrate which is made of a group III-nitride crystal and which has a high oxygen concentration domain where an oxygen concentration is higher than that of a matrix of the crystal; (b) irradiating the substrate with laser beam aiming at the high oxygen concentration domain, forming a through-hole penetrating the substrate in a thickness direction, and removing at least a part of the high oxygen concentration domain from the substrate; and (c) embedding at least a part of an inside of the through-hole by growing the group-III nitride crystal in the through-hole.

Abstract: There is provided a method for manufacturing a nitride crystal substrate including: a first step of constituting a seed crystal substrate assembly by arranging and placing a plurality of seed crystal substrates which are made of nitride crystal and whose principal surfaces are c-planes, on a base plate so that side surfaces of the adjacent seed crystal substrates are in contact with each other; and a second step of growing a crystal film on the seed crystal substrate assembly, wherein in the first step, the seed crystal substrates are placed on the base plate in a state of regulating a position of the seed crystal substrates in an in-plane direction by a position regulating unit to regulate the position of the seed crystal substrates in the in-plane direction, and at least one of the seed crystal substrates is placed non-adhesively to the base plate.

Abstract: A method for manufacturing a group III nitride semiconductor crystal substrate includes providing, as a seed crystal substrate, a group III nitride single crystal grown by a liquid phase growth method, and homoepitaxially growing a group III nitride single crystal by a vapor phase growth method on a principal surface of the seed crystal substrate. The principal surface of the seed crystal substrate is a +c-plane, and the seed crystal substrate has an atomic oxygen concentration of not more than 1×1017 cm?3 in a crystal near the principal surface over an entire in-plane region thereof.

Abstract: A high-quality nitride crystal substrate is manufactured, using a substrate for crystal growth with its diameter enlarged, the nitride crystal substrate including: a first step of preparing a substrate for crystal growth having a plurality of seed crystal substrates made of nitride crystals, arranged in a planar appearance, so that their main surfaces are parallel to each other and their lateral surfaces are in contact with each other, and a difference of a lattice constant between adjacent seed crystal substrates arbitrarily selected from a plurality of the seed crystal substrates is within 7×10?5 ?; and a second step of growing a crystal film on a ground surface belonging to the substrate for crystal growth.