Oxide semiconductors and semiconductor devices

Abstract

The present invention provides an oxide semiconductor containing germanium oxide with excellent electrical properties, a semiconductor device using the oxide semiconductor, and a method for manufacturing the oxide semiconductor. [Solution] A method for forming an oxide semiconductor is used in which a raw material solution containing a dopant element is atomized or dropletized, a carrier gas is supplied to the resulting atomized droplet, the atomized droplet is transported to a substrate with the carrier gas, and then the atomized droplet is subjected to a thermal reaction on the substrate, thereby forming an oxide semiconductor containing germanium oxide with a carrier density of 1.0 × 10⁻⁶ 18 / cm 3 The above describes how to obtain an oxide semiconductor.

Description

[Technical Field]

[0001] The present invention relates to an oxide semiconductor useful for semiconductor devices and a semiconductor device using the oxide semiconductor. [Background technology]

[0002] Germanium oxide is attracting attention as a wide-bandgap semiconductor useful for power devices and other applications. Germanium oxide is said to have a bandgap of 4.44 eV to 4.68 eV (Non-Patent Literature 1), and according to first-principles calculations, its Hall mobility is 27 cm⁻¹. 2 / Vs (perpendicular to the c-axis) or 29cm 2 It is estimated to be / Vs (Non-Patent Document 2), and the realization of pn homojunctions is also expected.

[0003] Rather than relying on estimations based on calculations as described above, the actual fabrication of germanium oxide has also been considered. Non-patent document 3 discloses the deposition of germanium oxide on an R-face sapphire substrate via a (Sn,Ge)O2 buffer layer using the MBE method. However, there have been no successful examples of doping germanium oxide films, and doping technology for germanium oxide films, which is essential for applications in power devices and the like, has been eagerly awaited. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] STAPELBROEK, M.; EVANS, BD Exciton structure in the uv-absorption edge of tetragonal GeO2. Solid State Communications, 1978, 25.11: 959-962. [Non-Patent Document 2] BUSHICK, Kyle, et al. Electron and hole mobility of rutile GeO2 from first principles: An ultrawide-bandgap semiconductor for power electronics. Applied Physics Letters, 2020, 117.18: 182104. [Non-Patent Document 3] CHAE, Sieun, et al. Epitaxial stabilization of rutile germanium oxide thin film by molecular beam epitaxy. Applied Physics Letters, 2020, 117.7: 072105. [Overview of the project] [Problems that the invention aims to solve]

[0005] The present invention aims to provide an oxide semiconductor containing germanium oxide with excellent electrical properties. [Means for solving the problem]

[0006] The inventors, after diligent research to achieve the above objective, have found that by doping germanium oxide under specific conditions using the mist CVD method, a well-doped carrier density of 1.0 × 10⁻⁶ can be obtained. 18 / cm 3 We have succeeded in creating the germanium oxide-containing oxide semiconductor described above for the first time in the world. Furthermore, we have found that such an oxide semiconductor can solve the conventional problems mentioned above. Furthermore, after obtaining the above findings, the inventors conducted further studies and completed the present invention.

[0007] In other words, the present invention relates to the following invention. [1] An oxide semiconductor film containing germanium oxide, wherein the carrier density is 1.0 × 10⁻¹⁶ 18 / cm 3 An oxide semiconductor characterized by the above. [2] The oxide semiconductor according to [1], wherein the atomic ratio of germanium among the metal elements in the oxide semiconductor is greater than 0.5. [3] The oxide semiconductor according to [1] or [2] having an n-type conductivity. [4] The oxide semiconductor according to any one of [1] to [3] above, which contains a dopant. [5] The oxide semiconductor according to [4], wherein the dopant comprises a Group 15 metal of the periodic table. [6] The oxide semiconductor according to [4] or [5], wherein the dopant is antimony. [7] An oxide semiconductor according to any of [1] to [6] above, wherein the resistivity is 10 Ωcm or less. [8] An oxide semiconductor according to any one of [1] to [7], which is in the form of a film. [9] A semiconductor device comprising at least an oxide semiconductor film according to any of [1] to [8] above and an electrode.

[10] A power conversion device using the semiconductor device described in [9] above.

[11] A control system using the semiconductor device described in [9] above.

[12] A method for producing an oxide semiconductor containing a doped germanium oxide on a substrate, characterized by atomizing or dropletizing a raw material solution containing a dopant element and germanium, wherein the germanium content is greater than the dopant element content, supplying a carrier gas to the resulting atomized droplets, transporting the atomized droplets to the substrate with the carrier gas, and then thermally reacting the atomized droplets on the substrate. [Effects of the Invention]

[0008] The oxide semiconductor of the present invention exhibits excellent electrical properties. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic diagram of a film deposition apparatus preferably used in embodiments of the present invention. [Figure 2] It is a diagram showing the measurement results of electrical characteristics in the examples. The vertical axis represents the electrical resistivity, and the horizontal axis represents the atomic ratio (%) of Sb to Ge. [Figure 3] It is a diagram schematically showing a preferred example of a Schottky barrier diode (SBD). [Figure 4] It is a diagram schematically showing a preferred example of a junction barrier Schottky diode (JBS). [Figure 5] It is a diagram schematically showing a preferred example of a metal-oxide-semiconductor field-effect transistor (MOSFET). [Figure 6] It is a diagram schematically showing a preferred example of a metal-oxide-semiconductor field-effect transistor (MOSFET). [Figure 7] It is a diagram schematically showing a preferred example of an insulated-gate bipolar transistor (IGBT). [Figure 8] It is a diagram schematically showing a preferred example of a light-emitting element (LED). [Figure 9] It is a block configuration diagram showing an example of a control system employing a semiconductor device according to an embodiment of the present invention. [Figure 10] It is a circuit diagram showing an example of a control system employing a semiconductor device according to an embodiment of the present invention. [Figure 11] It is a block configuration diagram showing an example of a control system employing a semiconductor device according to an embodiment of the present invention. [Figure 12] It is a circuit diagram showing an example of a control system employing a semiconductor device according to an embodiment of the present invention. [Figure 13] It is a diagram schematically showing a preferred example of a high electron mobility transistor (HEMT). [Figure 14] It is a diagram schematically showing a preferred example of a gas sensor. [Figure 15] It is a diagram schematically showing a preferred example of a photoelectric conversion element. [Figure 16] It is a diagram schematically showing a preferred example of a light-receiving element. [Figure 17]It is a diagram schematically showing a preferred example of a photoelectrode.

Mode for Carrying Out the Invention

[0010] The oxide semiconductor of the present invention is an oxide semiconductor containing an oxide of germanium, and has a carrier density of 1.0×10 18 / cm 3 or more. The carrier density refers to the carrier density measured by Hall effect measurement. The upper limit of the carrier density is not particularly limited, but 1.0×10 23 / cm 3 or less is preferable, and 1.0×10 22 / cm 3 or less is more preferable. Further, the oxide semiconductor preferably has a specific resistance (electrical resistivity) of 100 Ωcm or less, and more preferably 10 Ωcm or less. By having the above-described preferable electrical characteristics, when the oxide semiconductor is applied to a semiconductor device, the semiconductor device can provide good semiconductor characteristics. The oxide semiconductor may be crystalline or amorphous. When the oxide semiconductor has crystallinity, the oxide semiconductor may be a single crystal or a polycrystal. The crystal structure when the oxide semiconductor has crystallinity is also not particularly limited. Examples of the crystal structure include a hexagonal crystal or a tetragonal crystal. Further, the shape of the oxide semiconductor is not particularly limited as long as it does not inhibit the object of the present invention. The oxide semiconductor may be in the form of a film, a plate, or a sheet. In an embodiment of the present invention, it is preferable that the oxide semiconductor is in the form of a film because it can be more suitably applied to a semiconductor device. The film thickness when the oxide semiconductor is in the form of a film is not particularly limited. In an embodiment of the present invention, the film thickness is preferably 100 nm or more. By setting such a preferable film thickness, when the oxide semiconductor is applied to a semiconductor device, it is possible to impart more excellent withstand voltage characteristics to the semiconductor device.

[0011] The germanium oxide contained in the oxide semiconductor is not particularly limited as long as it is a compound of oxygen and germanium. In embodiments of the present invention, it is more preferable that the germanium oxide is included as the main component. Here, "main component" means that the content of germanium oxide (germanium oxide) in the oxide semiconductor is 50% or more in terms of composition ratio in the oxide semiconductor. In embodiments of the present invention, it is preferable that the content of germanium oxide in the oxide semiconductor is 70% or more in terms of composition ratio in the oxide semiconductor, and more preferably 90% or more. The oxide semiconductor may also contain other metals other than germanium. Examples of other metals include other Group 14 metals of the periodic table (such as tin or silicon). The atomic ratio of germanium among the metal elements in the oxide semiconductor is not particularly limited. In embodiments of the present invention, it is preferable that the atomic ratio of germanium among the metal elements in the oxide semiconductor is greater than 0.5, and more preferably 0.7 or more. By setting the atomic ratio of germanium within such a favorable range, it is possible to realize oxide semiconductors with a higher band gap (e.g., 4.0 eV or higher).

[0012] The oxide semiconductor preferably contains a dopant. The dopant is not particularly limited as long as it does not hinder the objectives of the present invention. The dopant may be an n-type dopant or a p-type dopant. Examples of the n-type dopant include antimony (Sb), arsenic (As), bismuth (Bi), or fluorine (F). In this embodiment of the present invention, the n-type dopant is preferably antimony (Sb). Examples of the p-type dopant include aluminum (Al), gallium (Ga), or indium (In). The dopant content in the oxide semiconductor is not particularly limited as long as it does not hinder the objectives of the present invention. Specifically, the dopant content in the oxide semiconductor is, for example, about 1 × 10⁻⁶ 16 / cm 3 ~1 × 10 22 / cm 3Alternatively, according to the present invention, the dopant may be approximately 1 × 10 20 / cm 3 It may be included at the above high concentrations.

[0013] The aforementioned oxide semiconductor can be obtained, for example, by the following preferred manufacturing method. Such a method for manufacturing oxide semiconductors (hereinafter also referred to as "oxide crystals" or "crystalline oxide films") is novel and useful and is included as one of the present inventions.

[0014] The present invention provides a method for producing an oxide semiconductor, characterized by atomizing or dropletizing a raw material solution containing a dopant element and germanium, wherein the germanium content is greater than the dopant element content (atomization step), supplying a carrier gas to the resulting atomized droplets, transporting the atomized droplets onto the substrate using the carrier gas (transportation step), and then subjecting the atomized droplets to a thermal reaction on the substrate (film formation step).

[0015] <Base> The substrate is not particularly limited as long as it can support the oxide semiconductor. The material of the substrate is also not particularly limited as long as it does not hinder the objective of the present invention, and may be a known substrate. The substrate may be made of an organic compound or an inorganic compound. The shape of the substrate is also not particularly limited as long as it does not hinder the objective of the present invention. Examples of the shape of the substrate include plate-like shapes such as flat plates and discs, fibrous shapes, rod-like shapes, cylindrical shapes, prismatic shapes, tubular shapes, spiral shapes, spherical shapes, and ring shapes, but in the present invention, the substrate is preferably a substrate, and more preferably a crystalline substrate. The thickness of the substrate is not particularly limited.

[0016] <Crystal substrate> The crystalline substrate is not particularly limited as long as it does not hinder the objectives of the present invention, and may be a known substrate. It may be an insulating substrate, a conductive substrate, or a semiconductor substrate. It may be a single-crystal substrate or a polycrystalline substrate. The crystalline substrate may be a substrate having a metal film on its surface. If the crystalline substrate is a conductive substrate, a vertical device can be fabricated without removing the substrate. The crystal structure of the crystalline substrate is also not particularly limited as long as it does not hinder the objectives of the present invention. Examples of the crystal structure of the crystalline substrate include a hexagonal structure and a tetragonal structure. Examples of crystalline substrates having a corundum structure include a sapphire substrate (such as an R-plane sapphire substrate). Examples of crystalline substrates having a tetragonal structure include a SrTiO3 substrate, a TiO2 substrate, and a MgF2 substrate. In the embodiments of the present invention, it is preferable that the crystalline substrate has a tetragonal structure, and more preferably a rutile-type structure. Examples of crystalline substrates having a rutile-type structure include a rutile-type titanium oxide (r-TiO2) substrate. The r-TiO2 substrate is preferably a conductive substrate containing a dopant such as Nb. The crystalline substrate may also have an off-angle. Furthermore, in the embodiments of the present invention, it is also preferable to use a Ge substrate as the crystalline substrate.

[0017] (Atomization process) The atomization step atomizes the raw material solution. The atomization means is not particularly limited as long as it can atomize the raw material solution, and any known means may be used, but in the present invention, an atomization means using ultrasound is preferred. The mist obtained using ultrasound is preferred because it has zero initial velocity and floats in the air, and is very suitable because, for example, it is not sprayed like a spray, but rather a mist that can be transported as a gas while floating in space, so there is no damage due to collision energy. The size of the mist droplets is not particularly limited and may be around a few millimeters, but is preferably 50 μm or less, and more preferably 100 nm to 10 μm.

[0018] (Raw material solution) The raw material solution is not particularly limited as long as it contains a dopant element and germanium, and the germanium content is greater than the dopant element content. The raw material solution may contain inorganic materials or organic materials. In the embodiments of the present invention, it is preferable that the raw material solution contains germanium in the form of an organic germanium compound. Furthermore, in the embodiments of the present invention, it is preferable that the organic germanium compound has a carboxyl group. The blending ratio of the germanium raw material (e.g., the organic germanium compound, etc.) in the raw material solution is not particularly limited, but is preferably 0.0001 mol / L to 20 mol / L and more preferably 0.001 mol / L to 1.0 mol / L relative to the total raw material solution. Examples of the dopant element include antimony (Sb), arsenic (As), bismuth (Bi), fluorine (F), aluminum (Al), gallium (Ga), or indium (In). In the embodiments of the present invention, it is preferable that the dopant element is antimony (Sb). The dopant element may be contained in the raw material solution in the form of an inorganic compound, or in the form of an organic compound.

[0019] The solvent of the raw material solution is not particularly limited and may be an inorganic solvent such as water, an organic solvent such as alcohol, or a mixed solution of an inorganic solvent and an organic solvent. In the present invention, it is preferable that the solvent contains water, and it is also preferable that it is a mixed solvent of water and acid. More specifically, the water may include, for example, pure water, ultrapure water, tap water, well water, mineral water, mineral water, hot spring water, spring water, fresh water, and seawater, but in the present invention, ultrapure water is preferred. More specifically, the acid may include, for example, organic acids such as acetic acid, propionic acid, and butanoic acid; boron trifluoride, boron trifluoride etherate, boron trichloride, boron tribromide, trifluoroacetic acid, trifluoromethanesulfonic acid, and p-toluenesulfonic acid.

[0020] Furthermore, additives such as hydrohalic acid and oxidizing agents may be mixed into the raw material solution. Examples of hydrohalic acid include hydrobromic acid, hydrochloric acid, and hydroiodic acid. Examples of oxidizing agents include peroxides such as hydrogen peroxide (H2O2), sodium peroxide (Na2O2), barium peroxide (BaO2), and benzoyl peroxide (C6H5CO)2O2, as well as organic peroxides such as hypochlorous acid (HClO), perchloric acid, nitric acid, ozonated water, peracetic acid, and nitrobenzene.

[0021] (Conveying process) In the transport process, a carrier gas is supplied to the atomized droplets (hereinafter also simply referred to as "mist") obtained in the atomization process, and the mist is transported to the substrate by the carrier gas. The type of carrier gas is not particularly limited as long as it does not hinder the objective of the present invention, and examples include oxygen, ozone, inert gases such as nitrogen and argon, or reducing gases such as hydrogen gas and foaming gas, but in the present invention, it is preferable to use oxygen as the carrier gas. Examples of carrier gases using oxygen include air, oxygen gas, and ozone gas, but oxygen gas and / or ozone gas are particularly preferred. Furthermore, there may be one type of carrier gas, or there may be two or more types, and a dilution gas with a changed carrier gas concentration (for example, a 10-fold dilution gas) may be used as a second carrier gas. Also, there may be two or more locations for supplying the carrier gas, not just one. In the present invention, when using an atomization chamber, a supply pipe, and a film-forming chamber, it is preferable to provide a carrier gas supply point in the atomization chamber and the supply pipe, respectively, and more preferably to provide a carrier gas supply point in the atomization chamber and a dilution gas supply point in the supply pipe. The flow rate of the carrier gas is not particularly limited, but is preferably 0.01 to 20 L / min, and more preferably 1 to 10 L / min. In the case of a dilution gas, the flow rate of the dilution gas is preferably 0.001 to 2 L / min, and more preferably 0.1 to 1 L / min.

[0022] (Film forming process) In the film-forming process, the atomized droplets are subjected to a thermal reaction on the substrate to form a film on part or all of the substrate surface. The thermal reaction is not particularly limited as long as it is a thermal reaction that forms a film from the mist; it is sufficient that the mist reacts with heat, and the reaction conditions are not particularly limited as long as they do not hinder the objective of the present invention. In this process, the thermal reaction is usually carried out at a temperature above the evaporation temperature of the solvent, but it is preferable that the temperature is not too high. In the present invention, it is preferable to carry out the thermal reaction at a temperature of 700°C to 800°C. Furthermore, the thermal reaction may be carried out under any of the following atmospheres, as long as it does not hinder the objective of the present invention: under vacuum, under a non-oxygen atmosphere, under a reducing gas atmosphere, and under an oxidizing atmosphere, and may also be carried out under any of the following conditions: under atmospheric pressure, under pressure, and under reduced pressure. However, in the present invention, it is preferable to carry out the reaction under an oxidizing atmosphere, also under atmospheric pressure, and more preferably under both an oxidizing atmosphere and atmospheric pressure. Note that the "oxidizing atmosphere" is not particularly limited as long as it is an atmosphere in which the oxide semiconductor can be formed by the thermal reaction. For example, an oxidizing atmosphere can be created by using a carrier gas containing oxygen or a mist consisting of a raw material solution containing an oxidizing agent. Furthermore, the film thickness can be set by adjusting the film formation time.

[0023] In embodiments of the present invention, the film may be formed directly on the substrate, or other layers such as a layer different from the oxide semiconductor (for example, an n-type semiconductor layer, an n+-type semiconductor layer, an n--type semiconductor layer, etc.), an insulating layer (including a semi-insulating layer), or a buffer layer may be laminated on the substrate, and then the film may be formed on the substrate via the other layers. In particular, a buffer layer can be suitably used to mitigate the difference in lattice constants between the crystal substrate and the oxide semiconductor. Examples of constituent materials for the buffer layer include SnO2, TiO2, VO2, MnO2, RuO2, CsO2, IrO2, GeO2, CuO2, PbO2, AgO2, CrO2, SiO2, and mixed crystals thereof.

[0024] The oxide semiconductor obtained as described above is useful for semiconductor devices, particularly power devices, and is suitably used as a semiconductor device comprising at least the oxide semiconductor and an electrode. Examples of semiconductor devices formed using the oxide semiconductor include transistors such as MIS and HEMT, TFTs, Schottky barrier diodes utilizing semiconductor-metal junctions, JBS, PN or PIN diodes combined with other P layers, and light-receiving and light-emitting elements. In addition to the above, the oxide semiconductor can also be suitably used in photoelectric conversion elements, gas sensors, photoelectrodes, memories, etc. In embodiments of the present invention, the oxide semiconductor may be used in a semiconductor device as the oxide semiconductor after optionally removing the crystal substrate, or it may be used in a semiconductor device as a crystalline laminated structure with the crystal substrate. In particular, when the crystal substrate is a conductive substrate, it can be suitably applied as the crystalline laminated structure to a semiconductor device (vertical device).

[0025] Furthermore, the semiconductor device can be suitably used as either a horizontal element (horizontal device) in which electrodes are formed on one side of the semiconductor layer, or a vertical element (vertical device) in which electrodes are formed on both the front and back sides of the semiconductor layer, respectively. However, in the embodiments of the present invention, it is particularly preferable to use it as a vertical device. Suitable examples of the semiconductor device include, for example, Schottky barrier diodes (SBDs), junction barrier Schottky diodes (JBSs), metal-semiconductor field-effect transistors (MESFETs), high electron-mobility transistors (HEMTs), metal-oxide-semiconductor field-effect transistors (MOSFETs), electrostatic induction transistors (SITs), junction field-effect transistors (JFETs), insulated-gate bipolar transistors (IGBTs), or light-emitting diodes (LEDs).

[0026] The following describes preferred examples of semiconductor devices in which the oxide semiconductor of the present invention is applied to an n-type semiconductor layer (such as an n+-type semiconductor or an n-- semiconductor layer), using the drawings as a reference. However, the present invention is not limited to these examples.

[0027] (SBD) Figure 3 shows an example of a Schottky barrier diode (SBD) according to an embodiment of the present invention. The SBD in Figure 3 comprises an n-type semiconductor layer 101a, an n+-type semiconductor layer 101b, a Schottky electrode 105a, and an ohmic electrode 105b.

[0028] The materials for Schottky electrodes and ohmic electrodes may be known electrode materials, and examples of such electrode materials include metals or alloys thereof such as Al, Mo, Co, Zr, Sn, Nb, Fe, Cr, Ta, Ti, Au, Pt, V, Mn, Ni, Cu, Hf, W, Ir, Zn, In, Pd, Nd, or Ag; metal oxide conductive films such as tin oxide, zinc oxide, rhenium oxide, indium oxide, indium tin oxide (ITO), and zinc indium oxide (IZO); organic conductive compounds such as polyaniline, polythiophene, or polypyrrole; or mixtures thereof; and laminates.

[0029] Schottky electrodes and ohmic electrodes can be formed by known means, such as vacuum deposition or sputtering. More specifically, for example, when forming a Schottky electrode using two types of metals, a first metal and a second metal, a layer made of the first metal and a layer made of the second metal can be stacked, and the layers made of the first metal and the layers made of the second metal can be patterned using photolithography.

[0030] When a reverse bias is applied to the SBD in Figure 3, a depletion layer (not shown) spreads within the n-type semiconductor layer 101a, resulting in a high-voltage SBD. When a forward bias is applied, electrons flow from the ohmic electrode 105b to the Schottky electrode 105a. In this way, the SBD using the semiconductor structure is excellent for high-voltage and high-current applications, has a fast switching speed, and is also excellent in terms of voltage resistance and reliability.

[0031] (JBS) Figure 4 shows a junction barrier Schottky diode (JBS), which is one of the preferred embodiments of the present invention. The semiconductor device in Figure 4 includes an n+ type semiconductor layer 4, an n- type semiconductor layer 3 stacked on the n- type semiconductor layer, a Schottky electrode 2 provided on the n- type semiconductor layer and capable of forming a Schottky barrier between itself and the i-type semiconductor layer, and a p-type semiconductor layer 1 provided between the Schottky electrode 2 and the n- type semiconductor layer 3. The p-type semiconductor layer 1 is embedded in the n-type semiconductor layer 3. In the present invention, it is preferable that the p-type semiconductor layers are provided at regular intervals, and it is more preferable that the p-type semiconductor layers are provided between both ends of the Schottky electrode and the n-type semiconductor layer. In this preferred embodiment, the JBS is configured to have superior thermal stability and adhesion, reduced leakage current, and superior semiconductor characteristics such as breakdown voltage. The semiconductor device in Figure 4 includes an ohmic electrode 5 on the n+ type semiconductor layer 4.

[0032] The means for forming each layer of the semiconductor device shown in Figure 4 are not particularly limited as long as they do not hinder the objectives of the present invention, and may be known means. For example, means of forming a film by vacuum deposition, CVD, sputtering, various coating techniques, etc., followed by patterning by photolithography, or means of directly patterning using printing technology, etc.

[0033] (MOSFET) Figure 5 shows an example where the semiconductor device of the present invention is a MOSFET. The MOSFET in Figure 5 is a trench-type MOSFET and comprises an n-type semiconductor layer 131a, n+-type semiconductor layers 131b and 131c, a gate insulating film 134, a gate electrode 135a, a source electrode 135b, and a drain electrode 135c.

[0034] An n+ type semiconductor layer 131b with a thickness of, for example, 100 nm to 100 μm is formed on the drain electrode 135c, and an n- type semiconductor layer 131a with a thickness of, for example, 100 nm to 100 μm is formed on the n+ type semiconductor layer 131b. Furthermore, an n+ type semiconductor layer 131c is formed on the n- type semiconductor layer 131a, and a source electrode 135b is formed on the n+ type semiconductor layer 131c.

[0035] Furthermore, within the n-type semiconductor layer 131a and the n+-type semiconductor layer 131c, a plurality of trench grooves are formed, penetrating the n+-type semiconductor layer 131c and reaching partway through the n-type semiconductor layer 131a. Within these trench grooves, gate electrodes 135a are embedded and formed via gate insulating films 134 with a thickness of, for example, 10 nm to 1 μm.

[0036] In the ON state of the MOSFET in Figure 5, when a voltage is applied between the source electrode 135b and the drain electrode 135c, and a positive voltage is applied to the gate electrode 135a relative to the source electrode 135b, a channel layer is formed on the side surface of the n-type semiconductor layer 131a, electrons are injected into the n-type semiconductor layer 131a, and the MOSFET turns on. In the OFF state, the voltage of the gate electrode is set to 0V, which prevents the formation of the channel layer, filling the n-type semiconductor layer 131a with a depletion layer, and the MOSFET turns off.

[0037] (HEMT) Figure 13 shows an example of a high electron mobility transistor (HEMT) according to an embodiment of the present invention. The HEMT in Figure 13 comprises a wide-bandgap n-type semiconductor layer 121a, a narrow-bandgap n-type semiconductor layer 121b, an n+-type semiconductor layer 121c, a semi-insulating layer 124, a buffer layer 128, a gate electrode 125a, a source electrode 125b, and a drain electrode 125c. In this embodiment of the present invention, it is also preferable, for example, to use the oxide semiconductor for the wide-bandgap n-type semiconductor layer 121a and Ge for the narrow-bandgap n-type semiconductor layer 121b.

[0038] The above examples show cases where a p-type semiconductor is not used, but the embodiments of the present invention are not limited thereto, and a p-type semiconductor may be used. Examples using a p-type semiconductor are shown in Figures 6 to 8 and 14 to 17. These semiconductor devices can be manufactured in the same manner as the above examples. It is preferable that the p-type semiconductor is made of the same material as the n-type semiconductor and contains a p-type dopant.

[0039] (MOSFET) Figure 6 shows a preferred example of a metal-oxide-semiconductor field-effect transistor (MOSFET) comprising an n-type semiconductor layer 131a, a first n+-type semiconductor layer 131b, a second n+-type semiconductor layer 131c, a p-type semiconductor layer 132, a p+-type semiconductor layer 132a, a gate insulating film 134, a gate electrode 135a, a source electrode 135b, and a drain electrode 135c. Note that the p+-type semiconductor layer 132a may be a p-type semiconductor layer, or it may be the same as the p-type semiconductor layer 132.

[0040] (IGBT) Figure 7 shows a preferred example of an insulated-gate bipolar transistor (IGBT) comprising an n-type semiconductor layer 151, an n-type semiconductor layer 151a, an n+-type semiconductor layer 151b, a p-type semiconductor layer 152, a gate insulating film 154, a gate electrode 155a, an emitter electrode 155b, and a collector electrode 155c.

[0041] (LED) Figure 8 shows an example where the semiconductor device according to an embodiment of the present invention is a light-emitting diode (LED). The semiconductor light-emitting device in Figure 8 has an n-type semiconductor layer 161 on a second electrode 165b, and a light-emitting layer 163 is laminated on the n-type semiconductor layer 161. A p-type semiconductor layer 162 is laminated on the light-emitting layer 163. A translucent electrode 167 that transmits light generated by the light-emitting layer 163 is provided on the p-type semiconductor layer 162, and a first electrode 165a is laminated on the translucent electrode 167. Note that the semiconductor light-emitting device in Figure 8 may be covered with a protective layer except for the electrode portion.

[0042] Examples of materials for translucent electrodes include conductive materials such as oxides containing indium (In) or titanium (Ti). More specifically, examples include In2O3, ZnO, SnO2, Ga2O3, TiO2, CeO2, or mixed crystals of two or more of these, or doped materials thereof. Translucent electrodes can be formed by providing these materials by known means such as sputtering. Alternatively, after forming the translucent electrode, thermal annealing may be performed to make the translucent electrode transparent.

[0043] In the semiconductor light-emitting element shown in Figure 8, the first electrode 165a is the positive electrode and the second electrode 165b is the negative electrode. By passing current through these electrodes to the p-type semiconductor layer 162, the light-emitting layer 163, and the n-type semiconductor layer 161, the light-emitting layer 163 emits light.

[0044] Examples of materials for the first electrode 165a and the second electrode 165b include metals such as Al, Mo, Co, Zr, Sn, Nb, Fe, Cr, Ta, Ti, Au, Pt, V, Mn, Ni, Cu, Hf, W, Ir, Zn, In, Pd, Nd, or Ag, or alloys thereof; metal oxide conductive films such as tin oxide, zinc oxide, indium oxide, indium tin oxide (ITO), and zinc indium oxide (IZO); organic conductive compounds such as polyaniline, polythiophene, or polypyrrole; or mixtures thereof. The method for forming the electrodes is not particularly limited and can be formed on the substrate according to a method appropriately selected from wet methods such as printing, spraying, and coating; physical methods such as vacuum deposition, sputtering, and ion plating; and chemical methods such as CVD and plasma CVD, taking into consideration their suitability with the materials.

[0045] (Gas sensor) Figure 14 shows an example of a gas sensor according to an embodiment of the present invention. The gas sensor in Figure 14 comprises a first layer 11, a second layer 12, a first electrode 13, and a second electrode 14. The first and second layers may be n-type semiconductor layers or p-type semiconductor layers. The work function of the second layer is smaller than the work function of the first layer. Preferably, the second layer and the first electrode form a Schottky junction. Preferably, the first layer and the second electrode form a Schottky junction. The materials of the first and second electrodes are not particularly limited. Examples of materials for the first and second electrodes include gold, silver, platinum, etc. By using the oxide semiconductor of the present invention for the first layer and / or the second layer, a gas sensor with higher sensitivity can be realized.

[0046] (Photoelectric conversion element) Figure 15 shows an example of a photoelectric conversion element according to an embodiment of the present invention. The photoelectric conversion element in Figure 15(a) has a structure in which a conductive film 51 functioning as a lower electrode, an electron blocking layer 56a, a photoelectric conversion layer 52, and a transparent conductive film 55 functioning as an upper electrode are stacked in this order. The photoelectric conversion element in Figure 15(b) has a configuration in which an electron blocking layer 56a, a photoelectric conversion layer 52, a hole blocking layer 56b, and an upper electrode 55 are stacked on the lower electrode 51 in this order. The stacking order of the electron blocking layer 56(a), the photoelectric conversion layer 52, and the hole blocking layer 16b in Figure 15(b) may be appropriately changed depending on the application and characteristics. The oxide semiconductor of the present invention may be used, for example, in the photoelectric conversion layer 52, the electron blocking layer 56a, or the hole blocking layer 56b. In the photoelectric conversion element of Figure 15, it is preferable that light is incident on the photoelectric conversion layer 52 via the upper electrode 55. Such photoelectric conversion elements can be suitably applied to optical sensor and image sensor applications.

[0047] (Photodetector) Figure 16 shows an example of a photodetector according to an embodiment of the present invention. The photodetector in Figure 16 comprises a lower electrode 40, a high-density n-type layer 41, a low-density n-type layer 42, a high-density p-type layer 43, a Schottky electrode 44, an upper electrode 45, and a specific region 46. The materials of the lower electrode 40, the Schottky electrode 44, and the upper electrode 45 may be known electrode materials (for example, Au, Ni, Pb, Rh, Co, Re, Te, Ir, Pt, Se, etc.). The specific region 46 is, for example, a high-density n-type region. In the embodiment of the present invention, the oxide semiconductor can be suitably used for the high-density n-type layer 41, the low-density n-type layer 42, the high-density p-type layer 43, and the specific region 46, etc. According to the photodetector in Figure 16, when eye-safe light is incident through the window of the upper electrode 45 and the light is free-electron-absorbed by the Schottky electrode 44, electrons are emitted towards the low-concentration n-type layer 42, and these emitted electrons can be accelerated in the high-electric-field region near the tip of the specific region 46.

[0048] (Photoelectrode) Figure 17 shows an example of a photoelectrode according to an embodiment of the present invention. The photoelectrode in Figure 17 comprises a substrate 31, a conductive layer (electron conduction layer) 32 provided on the substrate 31, and a photocatalytic layer (light absorption layer) 33 provided on the conductive layer 32. For example, a glass substrate or a sapphire substrate can be used as the substrate 31. In the embodiment of the present invention, the above-mentioned crystalline substrate may be used as the substrate 31. The thickness of the conductive layer 32 is not particularly limited, but is preferably 10 nm to 150 nm. The thickness of the photocatalytic layer 33 is not particularly limited, but is preferably 100 nm or more. Furthermore, if the photocatalytic layer 33 is made of an n-type semiconductor, it is preferable to determine the combination of materials for the photocatalytic layer 33 and the conductive layer 32 such that the energy difference between the vacuum level and the Fermi level of the conductive layer 32 is smaller than the energy difference between the vacuum level and the Fermi level of the photocatalytic layer 33. Furthermore, when the photocatalytic layer 33 is made of a p-type semiconductor, it is preferable to determine the combination of materials for the photocatalytic layer 33 and the conductive layer 32 such that the energy difference between the vacuum level and the Fermi level of the conductive layer 32 is greater than the energy difference between the vacuum level and the Fermi level of the photocatalytic layer 33. In this embodiment of the present invention, the oxide semiconductor can be suitably used in the conductive layer 32 and / or the photocatalytic layer 31. The photoelectrode in Figure 17 can be suitably used, for example, in a photoelectrochemical cell.

[0049] The crystalline oxide film or semiconductor device of the present invention described above can be applied to power conversion devices such as inverters and converters in order to exhibit the functions described above. More specifically, it can be applied as a diode built into an inverter or converter, or as a switching element such as a thyristor, power transistor, IGBT (Insulated Gate Bipolar Transistor), or MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor). Figure 9 is a block diagram showing an example of a control system using a semiconductor device according to an embodiment of the present invention, and Figure 10 is a circuit diagram of the same control system, which is a control system particularly suitable for installation in electric vehicles.

[0050] As shown in Figure 9, the control system 500 includes a battery (power source) 501, a boost converter 502, a buck converter 503, an inverter 504, a motor (driven object) 505, and a drive control unit 506, all of which are mounted in an electric vehicle. The battery 501 is a storage battery such as a nickel-metal hydride battery or a lithium-ion battery, and stores power through charging at a power supply station or regenerative energy during deceleration, and can output a DC voltage necessary for the operation of the electric vehicle's drive system and electrical system. The boost converter 502 is a voltage converter equipped with a chopper circuit, for example, and can boost a DC voltage of, for example, 200V supplied from the battery 501 to, for example, 650V by the switching operation of the chopper circuit, and output it to the drive system such as a motor. Similarly, the step-down converter 503 is a voltage conversion device equipped with a chopper circuit, but it can step down a DC voltage of, for example, 200V supplied from the battery 501 to, for example, about 12V, and output it to the electrical system, including power windows, power steering, or on-board electrical equipment.

[0051] The inverter 504 converts the DC voltage supplied from the boost converter 502 into a three-phase AC voltage by switching operation and outputs it to the motor 505. The motor 505 is a three-phase AC motor that constitutes the traction system of the electric vehicle, and is rotationally driven by the three-phase AC voltage output from the inverter 504. This rotational driving force is transmitted to the wheels of the electric vehicle via a transmission (not shown) and the like.

[0052] Meanwhile, various sensors (not shown) are used to measure actual values ​​such as wheel rotation speed, torque, and accelerator pedal depression (accelerator amount) from the electric vehicle while it is in motion, and these measurement signals are input to the drive control unit 506. At the same time, the output voltage value of the inverter 504 is also input to the drive control unit 506. The drive control unit 506 functions as a controller equipped with a calculation unit such as a CPU (Central Processing Unit) and a data storage unit such as memory. It generates control signals using the input measurement signals and outputs them as feedback signals to the inverter 504, thereby controlling the switching operation of the switching elements. As a result, the AC voltage supplied by the inverter 504 to the motor 505 is corrected instantaneously, enabling accurate operation control of the electric vehicle and realizing safe and comfortable operation of the electric vehicle. It is also possible to control the output voltage to the inverter 504 by supplying the feedback signal from the drive control unit 506 to the boost converter 502.

[0053] Figure 10 shows the circuit configuration excluding the step-down converter 503 in Figure 9, i.e., the configuration for driving the motor 505. As shown in the figure, the semiconductor device of the present invention is used for switching control by being employed, for example, as a Schottky barrier diode in the step-up converter 502 and the inverter 504. In the step-up converter 502, it is incorporated into a chopper circuit to perform chopper control, and in the inverter 504, it is incorporated into a switching circuit including an IGBT to perform switching control. In addition, current stabilization is achieved by interposing an inductor (such as a coil) at the output of the battery 501, and voltage stabilization is achieved by interposing capacitors (such as electrolytic capacitors) between the battery 501, the step-up converter 502, and the inverter 504.

[0054] Furthermore, as shown by the dotted line in Figure 10, the drive control unit 506 is equipped with a calculation unit 507 consisting of a CPU (Central Processing Unit) and a storage unit 508 consisting of non-volatile memory. Signals input to the drive control unit 506 are provided to the calculation unit 507, which performs the necessary calculations to generate feedback signals for each semiconductor element. The storage unit 508 temporarily holds the calculation results from the calculation unit 507 and stores physical constants and functions necessary for drive control in the form of a table, outputting them to the calculation unit 507 as appropriate. The calculation unit 507 and the storage unit 508 can employ known configurations, and their processing capabilities can be arbitrarily selected.

[0055] As shown in Figures 9 and 10, in the control system 500, diodes and switching elements such as thyristors, power transistors, IGBTs, and MOSFETs are used for the switching operation of the boost converter 502, the buck converter 503, and the inverter 504. Furthermore, by applying the semiconductor device etc. according to the present invention, extremely good switching characteristics can be expected, and further miniaturization and cost reduction of the control system 500 can be achieved. In other words, the effects of the present invention can be expected for each of the boost converter 502, the buck converter 503, and the inverter 504, and the effects of the present invention can be expected for any one of them, any combination of two or more of them, or in any configuration including the drive control unit 506. Furthermore, the control system 500 described above can be applied not only to the control system of an electric vehicle using the semiconductor device of the present invention, but also to control systems for a wide range of applications, such as boosting or stepping down power from a DC power source, or converting DC to AC power. It is also possible to use a power source such as a solar cell as the battery.

[0056] Figure 11 is a block diagram showing another example of a control system employing a semiconductor device according to an embodiment of the present invention, and Figure 12 is a circuit diagram of the same control system. This control system is suitable for installation in infrastructure equipment and home appliances that operate on power from an AC power source.

[0057] As shown in Figure 11, the control system 600 receives power supplied from an external source, such as a three-phase AC power supply (power source) 601, and includes an AC / DC converter 602, an inverter 604, a motor (to be driven) 605, and a drive control unit 606, which can be mounted on various devices (described later). The three-phase AC power supply 601 is, for example, a power generation facility of a power company (thermal power plant, hydroelectric power plant, geothermal power plant, nuclear power plant, etc.), and its output is supplied as AC voltage after being stepped down via a substation. Alternatively, it may be installed in a building or nearby facility in the form of a private generator, for example, and supplied via power cables. The AC / DC converter 602 is a voltage converter that converts AC voltage to DC voltage, converting the 100V or 200V AC voltage supplied from the three-phase AC power supply 601 into a predetermined DC voltage. Specifically, the voltage conversion converts it to a commonly used desired DC voltage such as 3.3V, 5V, or 12V. If the to be driven is a motor, the conversion to 12V is performed. It is also possible to use a single-phase AC power supply instead of a three-phase AC power supply, and in that case, a similar system configuration can be achieved by using an AC / DC converter with a single-phase input.

[0058] The inverter 604 converts the DC voltage supplied from the AC / DC converter 602 into a three-phase AC voltage by switching operation and outputs it to the motor 605. The form of the motor 604 varies depending on the controlled object, but if the controlled object is a train, it drives the wheels; if it is factory equipment, it drives pumps and various power sources; and if it is home appliances, it drives compressors, etc. It is a three-phase AC motor that is rotationally driven by the three-phase AC voltage output from the inverter 604 and transmits that rotational driving force to the driven object (not shown).

[0059] In addition, many home appliances, for example, can be driven directly by the DC voltage output from the AC / DC converter 302 (e.g., personal computers, LED lighting equipment, video equipment, audio equipment, etc.). In such cases, the inverter 604 is not required for the control system 600, and the DC voltage is supplied to the driven object from the AC / DC converter 602, as shown in Figure 11. In this case, for example, a 3.3V DC voltage is supplied to personal computers, and a 5V DC voltage is supplied to LED lighting equipment, etc.

[0060] Meanwhile, various sensors (not shown) are used to measure actual values ​​such as the rotational speed and torque of the driven object, as well as the temperature and flow rate of the surrounding environment of the driven object. These measurement signals are input to the drive control unit 606. At the same time, the output voltage value of the inverter 604 is also input to the drive control unit 606. Based on these measurement signals, the drive control unit 606 provides a feedback signal to the inverter 604, controlling the switching operation of the switching element. This instantly corrects the AC voltage supplied by the inverter 604 to the motor 605, enabling accurate operation control of the driven object and achieving stable operation of the driven object. Furthermore, as described above, if the driven object can be driven with a DC voltage, it is also possible to use feedback control of the AC / DC converter 602 instead of feedback to the inverter.

[0061] Figure 12 shows the circuit configuration of Figure 11. As shown in the figure, the semiconductor device of the present invention is used for switching control by being employed, for example, as a Schottky barrier diode in the AC / DC converter 602 and inverter 604. The AC / DC converter 602 uses, for example, a Schottky barrier diode configured in a bridge circuit, and performs DC conversion by converting the negative voltage component of the input voltage to a positive voltage and rectifying it. The inverter 604 is incorporated into the switching circuit of the IGBT to perform switching control. In addition, current stabilization is achieved by interposing an inductor (such as a coil) between the three-phase AC power supply 601 and the AC / DC converter 602, and voltage stabilization is achieved by interposing a capacitor (such as an electrolytic capacitor) between the AC / DC converter 602 and inverter 604.

[0062] Furthermore, as shown by the dotted line in Figure 12, the drive control unit 606 is equipped with a calculation unit 607 consisting of a CPU and a storage unit 608 consisting of non-volatile memory. Signals input to the drive control unit 606 are provided to the calculation unit 607, which performs the necessary calculations to generate feedback signals for each semiconductor element. The storage unit 608 temporarily holds the calculation results from the calculation unit 607 and stores physical constants and functions necessary for drive control in the form of a table, outputting them to the calculation unit 607 as appropriate. The calculation unit 607 and the storage unit 608 can employ known configurations, and their processing capabilities can be arbitrarily selected.

[0063] In such a control system 600, as with the control system 500 shown in Figures 11 and 12, diodes and switching elements such as thyristors, power transistors, IGBTs, and MOSFETs are used for the rectification and switching operations of the AC / DC converter 602 and inverter 604. Furthermore, by applying the semiconductor film and semiconductor device according to the present invention, extremely good switching characteristics can be expected, and further miniaturization and cost reduction of the control system 600 can be achieved. In other words, the effects of the present invention can be expected in each of the AC / DC converter 602 and inverter 604, and the effects of the present invention can be expected in any one of them, a combination thereof, or in a configuration that includes the drive control unit 606.

[0064] Although Figures 11 and 12 illustrate the motor 605 as the target to be driven, the target to be driven is not necessarily limited to mechanically operating devices, and can be many devices that require AC voltage. The control system 600 is applicable as long as it drives the target to be driven by inputting power from an AC power source, and can be installed for drive control of infrastructure equipment (e.g., power equipment in buildings and factories, communication equipment, traffic control equipment, water and wastewater treatment equipment, system equipment, labor-saving equipment, trains, etc.) and home appliances (e.g., refrigerators, washing machines, personal computers, LED lighting equipment, video equipment, audio equipment, etc.).

[0065] (Example 1) 1. Film deposition equipment The mist CVD apparatus used in this embodiment will be explained with reference to Figure 1. The mist CVD apparatus 19 comprises a susceptor 21 on which a substrate 20 is placed, a carrier gas supply means 22a for supplying carrier gas, a flow control valve 23a for adjusting the flow rate of carrier gas discharged from the carrier gas supply means 22a, a carrier gas (dilution) supply means 22b for supplying carrier gas (dilution), a flow control valve 23b for adjusting the flow rate of carrier gas discharged from the carrier gas (dilution) supply means 22b, a mist source 24 containing a raw material solution 24a, a container 25 for holding water 25a, an ultrasonic transducer 26 attached to the bottom surface of the container 25, a supply pipe 27 made of a quartz tube with an inner diameter of 40 mm, and a heater 28 installed around the periphery of the supply pipe 27. The susceptor 21 is made of quartz, and the surface on which the substrate 20 is placed is inclined from the horizontal plane. By fabricating both the supply tube 27, which serves as the film deposition chamber, and the susceptor 21 from quartz, the contamination of the film formed on the substrate 20 with impurities originating from the apparatus is suppressed.

[0066] 2. Preparation of raw material solution Bis[2-carboxyethylgermanium(IV)]sesquioxide (C6H 10 To a 0.005 M aqueous solution of Ge2O7, 10% by volume of hydrochloric acid (HCl) was added, and then antimony acetate was mixed in such a way that the atomic ratio of antimony to germanium was 0.0005. This was used as the raw material solution.

[0067] 3. Film preparation The raw material solution 24a obtained in step 2 above was placed in the mist generating source 24. Next, a (001)-plane r-TiO2 substrate was placed on the susceptor 21 as the substrate 20, and the temperature of the heater 28 was raised to 750°C. Next, the flow control valves 23a and 23b were opened, and carrier gas was supplied into the supply pipe 27 from the carrier gas supply means 22a and 22b, which are the carrier gas sources. After the atmosphere inside the supply pipe 27 was sufficiently replaced with carrier gas, the flow rate of the carrier gas was adjusted to 3.0 L / min and the flow rate of the carrier gas (dilution) was adjusted to 0.5 L / min. Oxygen was used as the carrier gas.

[0068] 4. Film formation Next, the ultrasonic transducer 26 was vibrated at 2.4 MHz, and the vibrations were propagated through water 25a to the raw material solution 24a, thereby atomizing the raw material solution 24a and generating mist (atomized droplets) 24b. This mist 24b was introduced into the deposition chamber 30 through the supply pipe 27 by a carrier gas, and under atmospheric pressure and at 750°C, the mist underwent a thermal reaction on the substrate 20 to form a GeO2 film on the substrate 20.

[0069] (Example 2) Bis[2-carboxyethylgermanium(IV)] sesquioxide (C6H) in the raw material solution 10 A GeO2 film was fabricated in the same manner as in Example 1, except that the concentration of Ge2O7 was set to 0.01 M (mol / L).

[0070] (Example 3) A GeO2 film was fabricated in the same manner as in Example 1, except that the starting material solution was prepared so that the concentration of antimony acetate in the starting material solution was such that the atomic ratio of antimony to germanium was 1:0.001.

[0071] (Example 4) Bis[2-carboxyethylgermanium(IV)] sesquioxide (C6H) in the raw material solution 10 A GeO2 film was fabricated in the same manner as in Example 1, except that the concentration of Ge2O7 was set to 0.01 M (mol / L) and the concentration of antimony acetate was set to an atomic ratio of antimony to germanium of 1:0.001.

[0072] Hall effect measurements were performed on the GeO2 films obtained in Examples 1-4, and the carrier type was found to be "n". The carrier densities of the GeO2 films obtained in Examples 1-4 are shown in Table 1. As is clear from Table 1, the oxide semiconductor according to the embodiment of the present invention has good electrical properties. Furthermore, the resistivity of the GeO2 films obtained in Examples 1-4 is shown in Figure 2. As is clear from Figure 2, it can be seen that the resistivity can be reduced well by controlling the dopant concentration in the raw material solution. In Figure 2, the vertical axis represents electrical resistivity, and the horizontal axis represents the atomic ratio (%) of Sb to Ge.

[0073] [Table 1] [Industrial applicability]

[0074] The oxide semiconductor of the present invention can be used in a wide range of fields, including semiconductors (e.g., compound semiconductor electronic devices), electronic components, electrical equipment components, optical and electrophotographic equipment, and industrial materials, but is particularly useful for semiconductor devices and their components. [Explanation of symbols]

[0075] 1 p-type semiconductor layer 2 Schottky electrodes 3 n-type semiconductor layer 4 n+ type semiconductor layer 5 Ohmic electrodes 11. The first layer 12. Second Layer 13 First electrode 14. Second electrode 19. Mist CVD apparatus 20 Substrates (crystal substrates) 21 Susceptor 22a Carrier gas supply means 22b Carrier gas (dilution) supply means 23a Flow control valve 23b Flow control valve 24 Mist Sources 24a Raw material solution 25 Container 25a water 26. Ultrasonic transducer 27 Supply pipe 28 Heater 29 Exhaust vent 31 circuit boards 32 Conductive layer (electron conduction layer) 33. Photocatalytic layer (light-absorbing layer) 40 Lower electrode 41 Highly concentrated n-type layer 42 Low concentration n-type layer 43 High concentration p-type layer 44 Schottky electrodes 45 Upper electrode 46 Specific area 51 Conductive film 52 Photoelectric conversion layer 55 Transparent conductive film 56a Electron blocking layer 56b Hole blocking layer 101a n-type semiconductor layer 101b n+ type semiconductor layer 105b Ohmic electrode 105a Schottky electrode 121a N-type semiconductor layer with a wide bandgap 121b Narrow bandgap n-type semiconductor layer 121c n+ type semiconductor layer 123 p-type semiconductor layer 124 Semi-insulating layer 125a gate electrode 125b Source electrode 125c drain electrode 128 Buffer layer 131a n-type semiconductor layer 131b First n+ type semiconductor layer 131c Second n+ type semiconductor layer 132 p-type semiconductor layer 132a p+ type semiconductor layer 134 Gate insulating film 135a Token 135b Source electrode 135c drain electrode 151 n-type semiconductor layer 151a n-type semiconductor layer 151b n+ type semiconductor layer 152 p-type semiconductor layer 154 Gate Insulator 155a Terminal 155b Emitter electrode 155c collector electrode 161 n-type semiconductor layer 162 p-type semiconductor layer 163 Emitting layer 165a First electrode 165b Second electrode 167 Translucent electrode 500 Control Systems 501 Battery (Power Supply) 502 Boost Converter 503 Step-Down Converter 504 Inverter 505 Motor (Driven object) 506 Drive Control Unit 507 Arithmetic section 508 Storage section 600 Control System 601 Three-phase AC power supply (power supply) 602 AC / DC Converter 604 Inverter 605 Motor (Driven object) 606 Drive Control Unit 607 Arithmetic section 608 Storage section

Claims

1. An oxide semiconductor containing germanium oxide, Contains a dopant, The dopant content is approximately 1 × 10 １６ / cm ３ That's all. The atomic ratio of germanium among the metal elements in the oxide semiconductor is greater than 0.

5. An oxide semiconductor having an n-type conductivity.

2. An oxide semiconductor containing germanium oxide, Contains a dopant, The dopant content is approximately 1 × 10 １６ / cm ３ That's all. An oxide semiconductor in which the dopant comprises antimony, arsenic, or bismuth.

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