Abstract: A water softening system includes a water feed channel through which water to be treated flows, and a crystallization unit that causes a metal ion contained in the water to be treated to precipitate. Further, the water softening system includes a separation unit that separates the water to be treated having passed through the crystallization unit into a crystal obtained through precipitation by the crystallization unit and soft water. Further, the water feed channel is configured so that at least a part thereof functions as a feed channel being a pressure application system in a substantially sealed state, and the crystallization unit and the separation unit are connected to parts corresponding to the feed channel being a pressure application system in a substantially sealed state in the water feed channel.

Abstract: An ultraviolet light-emitting element includes: a multilayer stack in which an n-type AlGaN layer, a light-emitting layer, a first p-type AlGaN layer, and a second p-type AlGaN layer are arranged in this order; a negative electrode; and a positive electrode. The first p-type AlGaN layer has a larger Al composition ratio than first AlGaN layers serving as well layers. The second p-type AlGaN layer has a larger Al composition ratio than the first AlGaN layers. The first p-type AlGaN layer and the second p-type AlGaN layer both contain Mg. The second p-type AlGaN layer has a higher maximum Mg concentration than the first p-type AlGaN layer. The second p-type AlGaN layer includes a region where an Mg concentration increases in a thickness direction thereof as a distance from the first p-type AlGaN layer increases in the thickness direction.

Abstract: An epitaxial substrate includes: a single crystal substrate including projections arranged in an array on a plane. Each projection has a conical or pyramidal shape tapered in a normal direction to the plane. The AlN layer includes: a first AlN crystal covering the plane and the projections with tips of the projections being exposed; second AlN crystals protruding from the tips of the projections along the normal direction and each having a shape of a column whose cross-sectional area increases as a distance from a tip of a corresponding projection increases; and a third AlN crystal as a layer interconnecting ends of the second AlN crystals, opposite the single crystal substrate.

Abstract: A UV LED element, which is an exemplary ultraviolet light-emitting diode according to the present invention, includes an n-type conductive layer, a light-emitting layer, an electron block layer, and a p-type contact layer, all of which are arranged in this order. Bandgap energy of the electron block layer satisfies Econtact?EEBL, where Econtact designates bandgap energy of the p-type contact layer and EEBL designates the bandgap energy of the electron block layer. The electric apparatus includes the UV LED element as a light source for emitting an ultraviolet ray.

Abstract: An ultraviolet light-emitting element includes: a multilayer stack in which an n-type AlGaN layer, a light-emitting layer, a first p-type AlGaN layer, and a second p-type AlGaN layer are arranged in this order; a negative electrode; and a positive electrode. The first p-type AlGaN layer has a larger Al composition ratio than first AlGaN layers serving as well layers. The second p-type AlGaN layer has a larger Al composition ratio than the first AlGaN layers. The first p-type AlGaN layer and the second p-type AlGaN layer both contain Mg. The second p-type AlGaN layer has a higher maximum Mg concentration than the first p-type AlGaN layer. The second p-type AlGaN layer includes a region where an Mg concentration increases in a thickness direction thereof as a distance from the first p-type AlGaN layer increases in the thickness direction.

Abstract: An epitaxial substrate includes: a single crystal substrate including projections arranged in an array on a plane. Each projection has a conical or pyramidal shape tapered in a normal direction to the plane. The AlN layer includes: a first AlN crystal covering the plane and the projections with tips of the projections being exposed; second AlN crystals protruding from the tips of the projections along the normal direction and each having a shape of a column whose cross-sectional area increases as a distance from a tip of a corresponding projection increases; and a third AlN crystal as a layer interconnecting ends of the second AlN crystals, opposite the single crystal substrate.

Abstract: A UV LED element, which is an exemplary ultraviolet light-emitting diode according to the present invention, includes an n-type conductive layer, a light-emitting layer, an electron block layer, and a p-type contact layer, all of which are arranged in this order. Bandgap energy of the electron block layer satisfies Econtact?EEBL, where Econtact designates bandgap energy of the p-type contact layer and EEBL designates the bandgap energy of the electron block layer. The electric apparatus includes the UV LED element as a light source for emitting an ultraviolet ray.

Abstract: An ultraviolet light emitting element includes a light emitting layer, a cap layer, an electron barrier layer. The light emitting layer has a multi-quantum well structure including barrier layers each including a first AlGaN layer and well layers each including a second AlGaN layer. The electron barrier layer includes at least one first p-type AlGaN layer and at least one second p-type AlGaN layer. The cap layer is located between the first p-type AlGaN layer and one of the well layers closest to the first p-type AlGaN layer. The cap layer is a third AlGaN layer having an Al composition ratio greater than an Al composition ratio of each of the well layers and less than an Al composition ratio of the first p-type AlGaN layer. The cap layer has a thickness of greater than or equal to 1 nm and less than or equal to 7 nm.

Abstract: An ultraviolet light emitting element includes a light emitting layer, a cap layer, an electron barrier layer. The light emitting layer has a multi-quantum well structure including barrier layers each including a first AlGaN layer and well layers each including a second AlGaN layer. The electron barrier layer includes at least one first p-type AlGaN layer and at least one second p-type AlGaN layer. The cap layer is located between the first p-type AlGaN layer and one of the well layers closest to the first p-type AlGaN layer. The cap layer is a third AlGaN layer having an Al composition ratio greater than an Al composition ratio of each of the well layers and less than an Al composition ratio of the first p-type AlGaN layer. The cap layer has a thickness of greater than or equal to 1 nm and less than or equal to 7 nm.

Abstract: In a method of manufacture for a nitride semiconductor light emitting element including: a monocrystalline substrate; and an AlN layer; and a first nitride semiconductor layer of a first electrical conductivity type; and a light emitting layer made of an AlGaN-based material; and a second nitride semiconductor layer of a second electrical conductivity type, a step of forming the AlN layer includes: a first step of supplying an Al source gas and a N source gas into the reactor to generate a group of AlN crystal nuclei having Al-polarity to be a part of the AlN layer on the surface of the monocrystalline substrate; and a second step of supplying the Al source gas and the N source gas into the reactor to form the AlN layer, after the first step.

Abstract: The epitaxial wafer includes a silicon substrate, an aluminum nitride thin film feeing a main surface of the silicon substrate, and an aluminum deposit between the silicon substrate and the aluminum nitride thin film so as to inhibit formation of silicon nitride. In the method for producing the epitaxial wafer, to form the aluminum deposit on the main surface of the silicon substrate, trimethyl aluminum is supplied into a reactor after a substrate temperature defined as a temperature of the silicon substrate is adjusted to a first predetermined temperature equal to or mare than. 300° C. and less than 1200° C. Thereafter, to form the aluminum nitride thin film facing the main surface of the silicon substrate, trimethyl aluminum and ammonia are supplied into the reactor after the substrate temperature is adjusted to a second predetermined temperature equal to or more than 1200° C. and equal to or less than 1400° C.

Abstract: An ultraviolet semiconductor light-emitting element comprises a light-emitting layer which is arranged between an n-type nitride semiconductor layer and a p-type nitride semiconductor layer, an n-electrode that is in contact with the n-type nitride semiconductor layer, and a p-electrode that is in contact with the p-type nitride semiconductor layer. The p-type nitride semiconductor layer is provided with a p-type contact layer that has a band gap smaller than that of the light-emitting layer and is in ohmic contact with the p-electrode. A depressed part is formed in a reverse side surface of a surface of the p-type nitride semiconductor layer that faces the light-emitting layer so as to avoid a formation region on which the p-electrode is formed. A reflective film that reflects ultraviolet light emitted from the light-emitting layer is formed on an inner bottom surface of the depressed part.

Abstract: The nitride semiconductor light-emitting element of the invention has a stacked structure of a buffer layer, an n-type nitride semiconductor layer, a light-emitting layer, and a p-type nitride semiconductor layer, on one surface side of a single crystal substrate of a sapphire substrate. A nitride semiconductor multilayer structure as the buffer layer includes: a plurality of island-like nuclei formed of AlN and formed on the one surface of the single crystal substrate; a first nitride semiconductor layer formed of an AlN layer and formed on the one surface side of the single crystal substrate so as to fill gaps between adjacent nuclei and to cover all the nuclei; and a second nitride semiconductor layer formed of an AlN layer and formed on the first nitride semiconductor layer. The nitride semiconductor multilayer structure is characterized in that the density of the nuclei is less than 6×109 nuclei cm?2.

Abstract: In a method of manufacture for a nitride semiconductor light emitting element including: a monocrystalline substrate; and an AlN layer; and a first nitride semiconductor layer of a first electrical conductivity type; and a light emitting layer made of an AlGaN-based material; and a second nitride semiconductor layer of a second electrical conductivity type, a step of forming the AlN layer includes: a first step of supplying an Al source gas and a N source gas into the reactor to generate a group of MN crystal nuclei having Al-polarity to be a part of the AlN layer on the surface of the monocrystalline substrate; and a second step of supplying the Al source gas and the N source gas into the reactor to form the AlN layer, after the first step.

Abstract: The nitride semi-conductive light emitting layer in this invention comprises a single crystal substrate 1 for epitaxial growth, a first buffer layer 2, an n-type nitride semi-conductive layer 3, a second buffer layer 4, a third buffer layer 5, a light emitting layer 6, and a p-type nitride semi-conductive layer 7. The first buffer layer 2 is laminated to a top side of the single crystal substrate 1. The n-type nitride semi-conductive layer 3 is laminated to a top side of the first buffer layer 2. The third buffer layer 5 is laminated to a top side of the n-type nitride semi-conductive layer 3 with the second buffer layer 4 being interposed therebetween. The light emitting layer 6 is laminated to a top side of the third buffer layer 5. The p-type nitride semi-conductive layer 7 is laminated to a top side of the light emitting layer 6.

Abstract: An ultraviolet semiconductor light-emitting element comprises a light-emitting layer which is arranged between an n-type nitride semiconductor layer and a p-type nitride semiconductor layer, an n-electrode that is in contact with the n-type nitride semiconductor layer, and a p-electrode that is in contact with the p-type nitride semiconductor layer. The p-type nitride semiconductor layer is provided with a p-type contact layer that has a band gap smaller than that of the light-emitting layer and is in ohmic contact with the p-electrode. A depressed part is formed in a reverse side surface of a surface of the p-type nitride semiconductor layer that faces the light-emitting layer so as to avoid a formation region on which the p-electrode is formed. A reflective film that reflects ultraviolet light emitted from the light-emitting layer is formed on an inner bottom surface of the depressed part.

Abstract: The nitride semiconductor light-emitting element of the invention has a stacked structure of a buffer layer, an n-type nitride semiconductor layer, a light-emitting layer, and a p-type nitride semiconductor layer, on one surface side of a single crystal substrate of a sapphire substrate. A nitride semiconductor multilayer structure as the buffer layer includes: a plurality of island-like nuclei formed of AlN and formed on the one surface of the single crystal substrate; a first nitride semiconductor layer formed of an AlN layer and formed on the one surface side of the single crystal substrate so as to fill gaps between adjacent nuclei and to cover all the nuclei; and a second nitride semiconductor layer formed of an AlN layer and formed on the first nitride semiconductor layer.

Abstract: In a process of fabricating a nitride nitride semi-conductor layer of AlaGabIn(1-a-b)N(0<a<1, 0<b<1, 1?a?b>0), the AlGaInN layer is grown at a growth rate less than 0.09 ?m/h according to the metal organic vapor phase epitaxy (MOPVE) method. The AlGaInN layer fabricated by the process in the present invention exhibits a high quality with low defect, and increases internal quantum yield.

Abstract: A nitride semi-conductor light emitting device has a p-type nitride semi-conductor layer 7, an n-type nitride semi-conductor layer 3, and a light emission layer 6 which is interposed between the p-type nitride semi-conductor layer 7 and the n-type nitride semi-conductor layer 3. The light emission layer 6 has a quantum well structure with a barrier layer 6b and a well layer 6a. The barrier layer 6b is formed of AlaGabIn(1-a-b)N (0<a<1, 0<b<1, 1?a?b>0), and contains a first impurity at a concentration of A greater than zero. The well layer 6a is formed of AlcGadIn(1-c-d)N (0<c<1, c<a, 0<d<1, 1?c?d>0), and contains a second impurity at a concentration of B equal to or greater than zero. In the nitride semi-conductor light emitting device of the present invention, the concentration of A is larger than that of B, in order that the barrier layer 6b has a concentration of oxygen smaller than that in the well layer 6a.

Abstract: The nitride semi-conductive light emitting layer in this invention comprises a single crystal substrate 1 for epitaxial growth, a first buffer layer 2, an n-type nitride semi-conductive layer 3, a second buffer layer 4, a third buffer layer 5, a light emitting layer 6, and a p-type nitride semi-conductive layer 7. The first buffer layer 2 is laminated to a top side of the single crystal substrate 1. The n-type nitride semi-conductive layer 3 is laminated to a top side of the first buffer layer 2. The third buffer layer 5 is laminated to a top side of the n-type nitride semi-conductive layer 3 with the second buffer layer 4 being interposed therebetween. The light emitting layer 6 is laminated to a top side of the third buffer layer 5. The p-type nitride semi-conductive layer 7 is laminated to a top side of the light emitting layer 6.