A wavelength conversion device of the present disclosure includes a substrate, a phosphor layer that has a matrix containing zinc oxide and phosphor particles embedded in the matrix and that is supported by the substrate, a dielectric layer disposed between the substrate and the phosphor layer, and a protective layer that is disposed between the phosphor layer and the dielectric layer and that has an isoelectric point equal to or larger than 7. A main surface of the substrate includes, for example, first and second regions. The phosphor layer covers, for example, only the first region out of the first and second regions.

A wavelength conversion device of the present disclosure includes a substrate, a phosphor layer that has a matrix containing zinc oxide and phosphor particles embedded in the matrix and that is supported by the substrate, a dielectric layer disposed between the substrate and the phosphor layer, and a protective layer that is disposed between the phosphor layer and the dielectric layer and that has an isoelectric point equal to or larger than 7. A main surface of the substrate includes, for example, first and second regions. The phosphor layer covers, for example, only the first region out of the first and second regions.

A group 13 nitride layer is composed of a polycrystalline group 13 nitride and is constituted by a plurality of monocrystalline particles having a particular crystal orientation approximately in a normal direction. The group 13 nitride comprises gallium nitride, aluminum nitride, indium nitride or the mixed crystal thereof. The group 13 nitride layer includes an upper surface and a bottom surface, and a full width at half maximum of a (1000) plane reflection of X-ray rocking curve on the upper surface is 20000 seconds or less and 1500 seconds or more.

A group 13 nitride layer is composed of a polycrystalline group 13 nitride and is constituted by a plurality of monocrystalline particles having a particular crystal orientation approximately in a normal direction. The group 13 nitride comprises gallium nitride, aluminum nitride, indium nitride or the mixed crystal thereof. The group 13 nitride layer includes an upper surface and a bottom surface, and a full width at half maximum of a (1000) plane reflection of X-ray rocking curve on the upper surface is 20000 seconds or less and 1500 seconds or more.

A semiconductor wafer forms on a mold containing a dopant. The dopant dopes a melt region adjacent the mold. There, dopant concentration is higher than in the melt bulk. A wafer starts solidifying. Dopant diffuses poorly in solid semiconductor. After a wafer starts solidifying, dopant can not enter the melt. Afterwards, the concentration of dopant in the melt adjacent the wafer surface is less than what was present where the wafer began to form. New wafer regions grow from a melt region whose dopant concentration lessens over time. This establishes a dopant gradient in the wafer, with higher concentration adjacent the mold. The gradient can be tailored. A gradient gives rise to a field that can function as a drift or back surface field. Solar collectors can have open grid conductors and better optical reflectors on the back surface, made possible by the intrinsic back surface field.

A semiconductor wafer forms on a mold containing a dopant. The dopant dopes a melt region adjacent the mold. There, dopant concentration is higher than in the melt bulk. A wafer starts solidifying. Dopant diffuses poorly in solid semiconductor. After a wafer starts solidifying, dopant can not enter the melt. Afterwards, the concentration of dopant in the melt adjacent the wafer surface is less than what was present where the wafer began to form. New wafer regions grow from a melt region whose dopant concentration lessens over time. This establishes a dopant gradient in the wafer, with higher concentration adjacent the mold. The gradient can be tailored. A gradient gives rise to a field that can function as a drift or back surface field. Solar collectors can have open grid conductors and better optical reflectors on the back surface, made possible by the intrinsic back surface field.

There is provided a self-supporting polycrystalline gallium nitride substrate having excellent characteristics such as high luminous efficiency and high conversion efficiency when used for devices, such as light emitting devices and solar cells. The self-supporting polycrystalline gallium nitride substrate is composed of gallium nitride-based single crystal grains having a specific crystal orientation in a direction approximately normal to the substrate, and has a top surface and a bottom surface. The crystal orientations of individual gallium nitride-based single crystal grains as determined from inverse pole figure mapping by electron backscatter diffraction (EBSD) analysis on the top surface are distributed at various tilt angles from the specific crystal orientation, in which the average tilt angle thereof is 0.1 or more and less than 1 and the cross-sectional average diameter D.sub.T of the gallium nitride-based single crystal grains at the outermost surface exposed on the top surface is 10 m or more.

There is provided a self-supporting polycrystalline gallium nitride substrate having excellent characteristics such as high luminous efficiency and high conversion efficiency when used for devices, such as light emitting devices and solar cells. The self-supporting polycrystalline gallium nitride substrate is composed of gallium nitride-based single crystal grains having a specific crystal orientation in a direction approximately normal to the substrate, and has a top surface and a bottom surface. The crystal orientations of individual gallium nitride-based single crystal grains as determined from inverse pole figure mapping by electron backscatter diffraction (EBSD) analysis on the top surface are distributed at various tilt angles from the specific crystal orientation, in which the average tilt angle thereof is 0.1 or more and less than 1 and the cross-sectional average diameter D.sub.T of the gallium nitride-based single crystal grains at the outermost surface exposed on the top surface is 10 m or more.

An electroplating copper layer includes bamboo-like copper crystal particles having a highly preferred orientation. The bamboo-like copper crystal particles have a long axis direction and a short axis direction, and the bamboo-like copper crystal particles have a length of 20 nm to 5 m in the long axis direction and a length of 20 nm to 2 m in the short axis direction. The bamboo-like copper crystal particles have a uniform particle size, and the electroplating copper layer has a major diffraction peak at a 2 angle of about 44.

An electroplating copper layer includes bamboo-like copper crystal particles having a highly preferred orientation. The bamboo-like copper crystal particles have a long axis direction and a short axis direction, and the bamboo-like copper crystal particles have a length of 20 nm to 5 m in the long axis direction and a length of 20 nm to 2 m in the short axis direction. The bamboo-like copper crystal particles have a uniform particle size, and the electroplating copper layer has a major diffraction peak at a 2 angle of about 44.