Aluminum oxide provides, at a thickness of 5 mm, an internal transmittance of 90% or higher for light at a wavelength of 193 nm.

Aluminum oxide provides, at a thickness of 5 mm, an internal transmittance of 90% or higher for light at a wavelength of 193 nm.

Provided is a manufacturing method for manufacturing a SiC substrate having a flattened surface, including etching the surface of the SiC substrate by irradiating the surface of the SiC substrate with atomic hydrogen while the SiC substrate having an off angle is heated. In the etching, the SiC substrate may be heated within a range of 800° C. or higher and 1200° C. or lower.

A semiconductor wafer of single-crystal silicon has an oxygen concentration per new ASTM of not less than 5.0×10.sup.17 atoms/cm.sup.3 and not more than 6.5×10.sup.17 atoms/cm.sup.3; a nitrogen concentration per new ASTM of not less than 1.0×10.sup.13 atoms/cm.sup.3 and not more than 1.0×10.sup.14 atoms/cm.sup.3; a front side having a silicon epitaxial layer wherein the semiconductor wafer has BMDs whose mean size is not more than 10 nm determined by transmission electron microscopy and whose mean density adjacent to the epitaxial layer is not less than 1.0×10.sup.11 cm.sup.−3, determined by reactive ion etching after having subjected the wafer covered with the epitaxial layer to a heat treatment at a temperature of 780° C. for a period of 3 h and to a heat treatment at a temperature of 600° C. for a period of 10 h.

A semiconductor wafer of single-crystal silicon has an oxygen concentration per new ASTM of not less than 5.0×10.sup.17 atoms/cm.sup.3 and not more than 6.5×10.sup.17 atoms/cm.sup.3; a nitrogen concentration per new ASTM of not less than 1.0×10.sup.13 atoms/cm.sup.3 and not more than 1.0×10.sup.14 atoms/cm.sup.3; a front side having a silicon epitaxial layer wherein the semiconductor wafer has BMDs whose mean size is not more than 10 nm determined by transmission electron microscopy and whose mean density adjacent to the epitaxial layer is not less than 1.0×10.sup.11 cm.sup.−3, determined by reactive ion etching after having subjected the wafer covered with the epitaxial layer to a heat treatment at a temperature of 780° C. for a period of 3 h and to a heat treatment at a temperature of 600° C. for a period of 10 h.

A silicon single crystal substrate for vapor phase growth, having the silicon single crystal substrate being made of an FZ crystal having a resistivity of 1000 Ωcm or more, wherein the surface of the silicon single crystal substrate is provided with a high nitrogen concentration layer having a nitrogen concentration higher than that of other regions and a nitrogen concentration of 5×10.sup.15 atoms/cm.sup.3 or more and a thickness of 10 to 100 μm.

A silicon single crystal substrate for vapor phase growth, having the silicon single crystal substrate being made of an FZ crystal having a resistivity of 1000 Ωcm or more, wherein the surface of the silicon single crystal substrate is provided with a high nitrogen concentration layer having a nitrogen concentration higher than that of other regions and a nitrogen concentration of 5×10.sup.15 atoms/cm.sup.3 or more and a thickness of 10 to 100 μm.

The present disclosure provides a growth method of a high-temperature phase lanthanum borosilicate crystal, where the high-temperature phase lanthanum borosilicate crystal is a β-La.sub.1-yLn.sub.yBSiO.sub.5 crystal prepared by a high-temperature flux method; a composite flux system is (La.sub.1-yLn.sub.y)BO.sub.3—LiMoO.sub.4—SiO.sub.2—B.sub.2O.sub.3, and (La.sub.1-yLn.sub.y)BO.sub.3, LiMoO.sub.4, SiO.sub.2, and B.sub.2O.sub.3 in the system have molar percentages of x.sub.1, x.sub.2, x.sub.3, and x.sub.4, respectively; 0<x.sub.1<0.3, 0.7≤x.sub.2<1, 0<x.sub.3<0.3, x.sub.1+x.sub.2+x.sub.3=1, x.sub.1:x.sub.4=2:1 to 4:1. In the present disclosure, a difficulty is overcome in the crystal growth of β-LaBSiO.sub.5 due to phase transition. The crystal is an optical function material that does not undergo the phase transition during annealing and can exist stably at room temperature. The crystal is widely used in laser, terahertz, and other fields.

The present disclosure provides a growth method of a high-temperature phase lanthanum borosilicate crystal, where the high-temperature phase lanthanum borosilicate crystal is a β-La.sub.1-yLn.sub.yBSiO.sub.5 crystal prepared by a high-temperature flux method; a composite flux system is (La.sub.1-yLn.sub.y)BO.sub.3—LiMoO.sub.4—SiO.sub.2—B.sub.2O.sub.3, and (La.sub.1-yLn.sub.y)BO.sub.3, LiMoO.sub.4, SiO.sub.2, and B.sub.2O.sub.3 in the system have molar percentages of x.sub.1, x.sub.2, x.sub.3, and x.sub.4, respectively; 0<x.sub.1<0.3, 0.7≤x.sub.2<1, 0<x.sub.3<0.3, x.sub.1+x.sub.2+x.sub.3=1, x.sub.1:x.sub.4=2:1 to 4:1. In the present disclosure, a difficulty is overcome in the crystal growth of β-LaBSiO.sub.5 due to phase transition. The crystal is an optical function material that does not undergo the phase transition during annealing and can exist stably at room temperature. The crystal is widely used in laser, terahertz, and other fields.

A gallium arsenide single crystal substrate having a main surface, in which a ratio of the number of As atoms existing as diarsenic trioxide to the number of As atoms existing as diarsenic pentoxide is greater than or equal to 2 when the main surface is measured by X-ray photoelectron spectroscopy, in which an X-ray having energy of 150 eV is used and a take-off angle of a photoelectron is set to 5°. Arithmetic average roughness (Ra) of the main surface is less than or equal to 0.3 nm.