There is provided a nitride crystal substrate having a main surface and formed of group-III nitride crystal, wherein N.sub.IR/N.sub.Elec, satisfies formula (1) below, which is a ratio of a carrier concentration N.sub.IR at a center of the main surface relative to a carrier concentration N.sub.Elec: 0.5≤N.sub.IR/N.sub.Elec≤1.5 . . . (1) where N.sub.IR is the carrier concentration on the main surface side of the nitride crystal substrate obtained based on a reflectance of the main surface measured by a reflection type Fourier transform infrared spectroscopy, and N.sub.Elec is the carrier concentration in the nitride crystal substrate obtained based on a specific resistance of the nitride crystal substrate and a mobility of the nitride crystal substrate measured by an eddy current method.

It is provided a method of growing a group 13 nitride crystal layer, on an underlying substrate including a seed crystal layer composed of a group 13 nitride. The underlying substrate is immersed in a melt containing a flux to grow a group 13 nitride crystal layer two-dimensionally on a nitrogen polar surface of the seed crystal layer by flux method.

It is provided a method of growing a group 13 nitride crystal layer, on an underlying substrate including a seed crystal layer composed of a group 13 nitride. The underlying substrate is immersed in a melt containing a flux to grow a group 13 nitride crystal layer two-dimensionally on a nitrogen polar surface of the seed crystal layer by flux method.

MOCVD systems can be used to form single crystal piezoelectric Sc.sub.xAl.sub.1−xN layers having a concentration of Sc in a range between about 4% and about 18% at temperatures in a range, for example, between about 800 degrees Centigrade and about 950 degrees Centigrade. The single crystal piezoelectric Sc.sub.xAl.sub.1−xN layers can have a crystalline structure characterized by an XRD ω-rocking curve FWHM value in a range between about less than 1.0 degrees to about 0.001 degrees as measured about the omega angle as of the Sc.sub.xAl.sub.1−xN (0002) film reflection.

MOCVD systems can be used to form single crystal piezoelectric Sc.sub.xAl.sub.1−xN layers having a concentration of Sc in a range between about 4% and about 18% at temperatures in a range, for example, between about 800 degrees Centigrade and about 950 degrees Centigrade. The single crystal piezoelectric Sc.sub.xAl.sub.1−xN layers can have a crystalline structure characterized by an XRD ω-rocking curve FWHM value in a range between about less than 1.0 degrees to about 0.001 degrees as measured about the omega angle as of the Sc.sub.xAl.sub.1−xN (0002) film reflection.

Fabrication of doped AlN crystals and/or AlGaN epitaxial layers with high conductivity and mobility is accomplished by, for example, forming mixed crystals including a plurality of impurity species and electrically activating at least a portion of the crystal.

A surface-coated cutting tool includes a base material and a coating formed on a surface of the base material. The coating includes a first hard coating layer including crystal grains having a sodium chloride-type crystal structure. The crystal grain has a layered structure in which a first layer composed of nitride or carbonitride of Al.sub.xTi.sub.1-x and a second layer composed of nitride or carbonitride of Al.sub.yTi.sub.1-y are stacked alternately into one or more layers. The first layer each has an atomic ratio x of Al varying in a range of 0.6 or more to less than 1. The second layer each has an atomic ratio y of Al varying in a range of 0.45 or more to less than 0.6. The largest value of difference between the atomic ratio x and the atomic ratio y is 0.05≤x−y≤0.5.

A surface-coated cutting tool includes a base material and a coating formed on a surface of the base material. The coating includes a first hard coating layer including crystal grains having a sodium chloride-type crystal structure. The crystal grain has a layered structure in which a first layer composed of nitride or carbonitride of Al.sub.xTi.sub.1-x and a second layer composed of nitride or carbonitride of Al.sub.yTi.sub.1-y are stacked alternately into one or more layers. The first layer each has an atomic ratio x of Al varying in a range of 0.6 or more to less than 1. The second layer each has an atomic ratio y of Al varying in a range of 0.45 or more to less than 0.6. The largest value of difference between the atomic ratio x and the atomic ratio y is 0.05≤x−y≤0.5.

A process of preparing a wafer having a diameter of two inches or more, at least a surface of the wafer being formed from a group III nitride crystal, including preparing an alkaline or acidic etching liquid containing a peroxodisulfate ion as an oxidizing agent that accepts an electron, accommodating the wafer such that the surface of the wafer is immersed in the etching liquid such that the surface of the wafer is parallel with a surface of the etching liquid; and radiating light from the surface side of the etching liquid onto the surface of the wafer without agitating the etching liquid. First and second etching areas disposed at an interval from each other are defined on the surface of the wafer. In the process of radiating the light onto the surface of the wafer, the light is radiated perpendicularly onto surfaces of the first and second etching areas.

Provided is a piezoelectric film including an AlN crystal, and a first element and a second element doped to the AlN crystal. The first element is an element having an ionic radius larger than an ionic radius of Al. The second element is an element having an ionic radius smaller than the ionic radius of Al. Also provided are piezoelectric film laminated body including an underlayer and a piezoelectric film including ScAlN, and a method of manufacturing the same. The underlayer has a crystal lattice having six-fold symmetry or three-fold symmetry. Also provided are a piezoelectric film including ScAlN having a laminated structure of a hexagonal crystal and a cubic crystal, and a method of manufacturing the same. The cubic crystal is doped with an element other than trivalent element.