Provided are a metal nitride material for a thermistor, which exhibits high reliability and high heat resistance and can be directly deposited on a film or the like without firing, a method for producing the metal nitride material for a thermistor, and a film type thermistor sensor. The metal nitride material for a thermistor consists of a metal nitride represented by the general formula: Ti.sub.xAl.sub.y(N.sub.1-wO.sub.w).sub.z (where 0.70≦y/(x+y)≦0.95, 0.45≦z≦0.55, 0<w≦0.35, and x+y+z=1), and the crystal structure thereof is a hexagonal wurtzite-type single phase.

A vapor phase epitaxial growth device comprises a reactor vessel and a wafer holder arranged within the reactor vessel. The wafer holder includes a wafer holding surface configured to hold a wafer with a wafer surface oriented substantially vertically downward. The device comprises a first material gas supply pipe configured to supply a first material gas and arranged below the wafer holding surface. The device comprises a second material gas supply pipe configured to supply a second material gas and arranged below the wafer holding surface. The device comprises a gas exhaust pipe configured to exhaust gases and arranged below the wafer holding surface. A distance between the gas exhaust pipe and an axis line passing through a center of the wafer holding surface is greater than distances between the axis line and each of the first material gas supply pipe and the second material gas supply pipe.

A vapor phase epitaxial growth device comprises a reactor vessel and a wafer holder arranged within the reactor vessel. The wafer holder includes a wafer holding surface configured to hold a wafer with a wafer surface oriented substantially vertically downward. The device comprises a first material gas supply pipe configured to supply a first material gas and arranged below the wafer holding surface. The device comprises a second material gas supply pipe configured to supply a second material gas and arranged below the wafer holding surface. The device comprises a gas exhaust pipe configured to exhaust gases and arranged below the wafer holding surface. A distance between the gas exhaust pipe and an axis line passing through a center of the wafer holding surface is greater than distances between the axis line and each of the first material gas supply pipe and the second material gas supply pipe.

Provided are a metal nitride material for a thermistor, which has a high heat resistance and a high reliability and can be directly deposited on a film or the like without firing, a method for producing the same, and a film type thermistor sensor. The metal nitride material for a thermistor consists of a metal nitride represented by the general formula: V.sub.xAl.sub.y(N.sub.1-wO.sub.w).sub.z (where 0.70≦y/(x+y)≦0.98, 0.45≦z≦0.55, 0<w≦0.35, and x+y+z=1), wherein the crystal structure thereof is a hexagonal wurtzite-type single phase. The method for producing the metal nitride material for a thermistor includes a deposition step of performing film deposition by reactive sputtering in a nitrogen and oxygen-containing atmosphere using a V—Al alloy sputtering target.

A semiconductor device includes: a substrate; and an n-type layer including a nitride semiconductor formed on the surface of the substrate. In the n-type layer, the concentration of donor impurities (excluding O) is 1×10.sup.15 cm.sup.−3 or more and 1×10.sup.20 cm.sup.−3 or less, the concentration of C impurities is 1×10.sup.16 cm.sup.−3 or less, the concentration of O impurities is 1×10.sup.16 cm.sup.−3 or less, the concentration of Ca impurities is 1×10.sup.16 cm.sup.−3 or less, and the sum total of the concentrations of the C impurities, the O impurities, and the Ca impurities is lower than the concentration of the donor impurities. Such a semiconductor device can be fabricated by using a halogen-free vapor phase epitaxy (HF-VPE) device.

A method for producing a crystal substrate includes preparing, measuring, holding, and machining. The preparing prepares a crystal substrate body including a curved crystal lattice plane. The measuring measures a shape feature of the crystal lattice plane. The holding holds the crystal substrate body in a warped state in accordance with the shape feature measured by the measuring, to more flatten the crystal lattice plane than the crystal lattice plane at the preparing. The machining machines a surface of the crystal substrate body held in the warped state, to flatten the surface.

Provided are a metal nitride material for a thermistor, which has a high reliability and a high heat resistance and can be directly deposited on a film or the like without firing, a method for producing the same, and a film type thermistor sensor. The metal nitride material for a thermistor consists of a metal nitride represented by the general formula: Cr.sub.xAl.sub.y(N.sub.1-wO.sub.w).sub.z (where 0.70≦y/(x+y)≦0.95, 0.45≦z≦0.55, 0<w≦0.35, and x+y+z=1), wherein the crystal structure thereof is a hexagonal wurtzite-type single phase.

Provided are a metal nitride material for a thermistor, which has a high reliability and a high heat resistance and can be directly deposited on a film or the like without firing, a method for producing the same, and a film type thermistor sensor. The metal nitride material for a thermistor consists of a metal nitride represented by the general formula: Cr.sub.xAl.sub.y(N.sub.1-wO.sub.w).sub.z (where 0.70≦y/(x+y)≦0.95, 0.45≦z≦0.55, 0<w≦0.35, and x+y+z=1), wherein the crystal structure thereof is a hexagonal wurtzite-type single phase.

Provides is a C-plane GaN substrate which, although formed from a GaN crystal grown so that surface pits are generated, is free from any inversion domain, and moreover, has a low spiral dislocation density in a gallium polar surface. Provides is a C-plane GaN substrate wherein: the substrate comprises a plurality of facet growth areas each having a closed ring outline-shape on a gallium polar surface; the spiral dislocation density is less than 1×10.sup.6 cm.sup.−2 anywhere on the gallium polar surface; and the substrate is free from any inversion domain. The C-plane GaN substrate may comprise a high dislocation density part having a dislocation density of more than 1×10.sup.7 cm.sup.−2 and a low dislocation density part having a dislocation density of less than 1×10.sup.6 cm.sup.−2 on the gallium polar surface.

A new GaN single crystal is provided. A GaN single crystal according to the present embodiment comprises a gallium polar surface which is a main surface on one side and a nitrogen polar surface which is a main surface on the opposite side, wherein on the gallium polar surface is found at least one square area, an outer periphery of which is constituted by four sides each with a length of 2 mm or more, and, when the at least one square are is divided into a plurality of sub-areas each of which is a square of 100 μm×100 μm, pit-free areas account for 80% or more of the sub-areas.