Oxide semiconductor and semiconductor device

Abstract

A germanium oxide-containing oxide semiconductor with excellent electrical properties is provided. An oxide semiconductor film containing germanium oxide is achieved using an oxide semiconductor formation method characterized by atomizing or dropletizing a raw material solution that contains a dopant element, supplying a carrier gas to the obtained atomized droplets, conveying the atomized droplets onto the substrate by means of the carrier gas, and subsequently thermally reacting the atomized droplets on the substrate, wherein the carrier density is at least 1.0×1018 / cm3.

Description

Oxide semiconductor and semiconductor device

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

[0002] Germanium oxide has attracted attention as a wide bandgap semiconductor useful for power devices, etc. Germanium oxide is said to have a bandgap of 4.44 eV to 4.68 eV (Non-Patent Document 1), and according to first-principles calculations, the hole mobility is 27 cm ２ / Vs (direction perpendicular to the c-axis) or 29 cm ２ / Vs (Non-Patent Document 2), and the realization of a pn homojunction is also expected.

[0003] Rather than estimating by calculation as described above, the actual fabrication of germanium oxide has also been investigated. Non-Patent Document 3 describes the fabrication of (Sn, Ge)O on an R-plane sapphire substrate using MBE. ２ It has been disclosed that a germanium oxide film can be formed via a buffer layer. However, there have been no examples of successful doping of germanium oxide films, and a doping technique for germanium oxide films, which is essential for applications such as power devices, has been eagerly awaited.

[0004] STAPELBROEK, M.; EVANS, BD Exciton structure in the uv-absorption edge of tetragonal GeO2. Solid State Communications, 1978, 25.11: 959-962.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.CHAE, Sieun, et al. Epitaxial stabilization of rutile germanium oxide thin film by molecular beam epitaxy. Applied Physics Letters, 2020, 117.7: 072105.

[0005] An object of the present invention is to provide an oxide semiconductor containing germanium oxide that has excellent electrical properties.

[0006] As a result of extensive research to achieve the above object, the present inventors have discovered that by doping germanium oxide under specific conditions using a mist CVD method, a well-doped carrier density of 1.0×10 １８ / cm ３ The inventors of the present invention have succeeded in creating the above-mentioned oxide semiconductor containing germanium oxide for the first time in the world. Furthermore, they have found that such an oxide semiconductor can solve the above-mentioned problems of the conventional technology. After obtaining the above-mentioned findings, the inventors of the present invention have conducted further studies and have completed the present invention.

[0007] That is, the present invention relates to the following inventions: [1] An oxide semiconductor film containing an oxide of germanium, the oxide semiconductor film having a carrier density of 1.0×10 １８ / cm ３or more. [2] The oxide semiconductor according to [1] above, wherein the atomic ratio of germanium to the metal elements in the oxide semiconductor is greater than 0.5. [3] The oxide semiconductor according to [1] or [2] above, which has 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] above, wherein the dopant includes a metal of Group 15 of the periodic table. [6] The oxide semiconductor according to [4] or [5] above, wherein the dopant is antimony. [7] The oxide semiconductor according to any one of [1] to [6] above, which has a resistivity of 10 Ωcm or less. [8] The oxide semiconductor according to any one of [1] to [7] above, which is in the form of a film. [9] A semiconductor device comprising at least the oxide semiconductor film according to any one of [1] to [8] above and an electrode.

[10] A power conversion device using the semiconductor device according to [9] above.

[11] A control system using the semiconductor device according to [9] above.

[12] A method for producing an oxide semiconductor containing an oxide of germanium doped on a substrate, the method comprising: atomizing or forming droplets from a raw material solution containing a dopant element and germanium, the raw material solution having a higher germanium content than the dopant element; supplying a carrier gas to the obtained atomized droplets; transporting the atomized droplets onto the substrate by the carrier gas; and then thermally reacting the atomized droplets on the substrate.

[0008] The oxide semiconductor of the present invention has excellent electrical properties.

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

[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 The carrier density is a carrier density measured by Hall effect measurement. The upper limit of the carrier density is not particularly limited, but is preferably 1.0×10 ２３ / cm ３ Preferably, the value is 1.0 x 10 or less. ２２ / cm ３The following is more preferable. Furthermore, the oxide semiconductor preferably has a resistivity (electrical resistivity) of 100 Ωcm or less, more preferably 10 Ωcm or less. By having the above-mentioned preferable electrical properties, when the oxide semiconductor is applied to a semiconductor device, the semiconductor device can be provided with better semiconductor properties. The oxide semiconductor may be crystalline or amorphous. When the oxide semiconductor is crystalline, the oxide semiconductor may be single crystalline or polycrystalline. When the oxide semiconductor is crystalline, the crystal structure is not particularly limited. Examples of the crystal structure include a hexagonal crystal and a tetragonal crystal. Furthermore, the shape of the oxide semiconductor is not particularly limited as long as it does not impede 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, the oxide semiconductor is preferably in the form of a film, since this makes it more suitable for application to semiconductor devices. When the oxide semiconductor is in the form of a film, the film thickness is not particularly limited. In an embodiment of the present invention, the film thickness is preferably 100 nm or more. By setting the film thickness to such a preferable value, when the oxide semiconductor is applied to a semiconductor device, the semiconductor device can be endowed with superior breakdown voltage.

[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 an embodiment of the present invention, it is more preferable that the germanium oxide is contained as a 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 an embodiment of the present invention, the content of germanium oxide in the oxide semiconductor is preferably 70% or more, more preferably 90% or more in terms of composition ratio in the oxide semiconductor. Furthermore, the oxide semiconductor may contain another metal other than germanium. Examples of the other metal include metals of Group 14 of the periodic table other than germanium (such as tin or silicon). The atomic ratio of germanium among the metal elements in the oxide semiconductor is not particularly limited. In an embodiment of the present invention, the atomic ratio of germanium among the metal elements in the oxide semiconductor is preferably greater than 0.5, more preferably greater than 0.7. By setting the atomic ratio of germanium in such a preferred range, an oxide semiconductor having a higher band gap (for example, 4.0 eV or more) can be realized.

[0012] The oxide semiconductor preferably contains a dopant. The dopant is not particularly limited as long as it does not impede the object 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), and fluorine (F). In an embodiment of the present invention, the n-type dopant is preferably antimony (Sb). Examples of the p-type dopant include aluminum (Al), gallium (Ga), and indium (In). The content of the dopant in the oxide semiconductor is not particularly limited as long as it does not impede the object of the present invention. Specifically, the content of the dopant in the oxide semiconductor is, for example, about 1×10 １６ / cm ３ ~1 x 10 ２２ / cm ３In accordance with the present invention, the dopant may be about 1×10 ２０ / cm ３ It may be contained in a concentration higher than this.

[0013] The oxide semiconductor can be obtained, for example, by the following suitable production method. The production method of such an oxide semiconductor (hereinafter also referred to as "oxide crystal" or "crystalline oxide film") is also novel and useful, and is included in the present invention.

[0014] The method for producing an oxide semiconductor of the present invention is characterized by, for example, atomizing or forming droplets from a raw material solution containing a dopant element and germanium, the raw material solution having a higher germanium content than the dopant element (atomization step), supplying a carrier gas to the obtained atomized droplets, transporting the atomized droplets onto the substrate by the carrier gas (transport step), and then thermally reacting the atomized droplets on the substrate (film-forming step).

[0015] <Base> The base is not particularly limited as long as it can support the oxide semiconductor. The material of the base is also not particularly limited, and may be a known base, as long as it does not impede the object of the present invention. The base may be made of an organic compound or an inorganic compound. The shape of the base is also not particularly limited as long as it does not impede the object of the present invention. Examples of the shape of the base include a plate-like shape such as a flat plate or a disk, a fiber-like shape, a rod-like shape, a cylindrical shape, a prismatic shape, a cylindrical shape, a spiral shape, a spherical shape, and a ring-like shape. In the present invention, the base is preferably a substrate, and more preferably a crystalline substrate. The thickness of the substrate is not particularly limited.

[0016] <Crystalline Substrate> The crystalline substrate is not particularly limited as long as it does not impede the object 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. When 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 impede the object of the present invention. Examples of the crystal structure of the crystalline substrate include a hexagonal crystal structure and a tetragonal crystal structure. Examples of crystal substrates having a corundum structure include a sapphire substrate (e.g., an R-plane sapphire substrate). Examples of crystal substrates having a tetragonal crystal structure include SrTiO ３ Substrate, TiO ２ Substrate, MgF ２ In an embodiment of the present invention, the crystalline substrate preferably has a tetragonal structure, and more preferably a rutile structure. Examples of crystalline substrates having a rutile structure include rutile titanium oxide (r-TiO ２ ) substrates, etc. ２ The substrate is preferably a conductive substrate containing a dopant such as Nb. The crystalline substrate may have an off-axis angle. In an embodiment of the present invention, a Ge substrate is preferably used as the crystalline substrate.

[0017] (Atomization Step) In the atomization step, the raw material solution is atomized. 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 ultrasonic waves is preferred. The mist obtained using ultrasonic waves is preferable because it has an initial velocity of zero and floats in the air. For example, rather than being sprayed like a spray, it is a mist that floats in space and can be transported as a gas, and is therefore highly suitable because it is not damaged by collision energy. The size of the mist droplets is not particularly limited and may be on the order of several mm, 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, with the germanium content being greater than the dopant element. The raw material solution may contain an inorganic material or an organic material. In an embodiment of the present invention, the raw material solution preferably contains germanium in the form of an organogermanium compound. In an embodiment of the present invention, the organogermanium compound preferably has a carboxyl group. The blending ratio of the germanium raw material (e.g., the organogermanium compound) in the raw material solution is not particularly limited, but is preferably 0.0001 mol / L to 20 mol / L, 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), and indium (In). In an embodiment of the present invention, the dopant element is preferably antimony (Sb). The dopant element may be contained in the raw material solution in the form of an inorganic compound, or may be contained in the raw material solution in the form of an organic compound.

[0019] The solvent for 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, the solvent preferably contains water, and is also preferably a mixed solvent of water and an acid. More specific examples of the water include pure water, ultrapure water, tap water, well water, mineral water, hot spring water, spring water, fresh water, and seawater, with ultrapure water being preferred in the present invention. More specific examples of the acid include 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] The raw material solution may be mixed with additives such as hydrohalic acid and an oxidizing agent. Examples of the hydrohalic acid include hydrobromic acid, hydrochloric acid, and hydroiodic acid. Examples of the oxidizing agent include hydrogen peroxide (H ２ O ２ ), sodium peroxide (Na ２ O ２ ), barium peroxide (BaO ２ ), benzoyl peroxide (C ６ H ５ CO) ２ O ２ hypochlorous acid (HClO), perchloric acid, nitric acid, ozone water, peracetic acid, nitrobenzene, and other organic peroxides.

[0021] (Transportation Process) In the transport process, a carrier gas is supplied to the atomized droplets (hereinafter 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 impede the object of the present invention, and examples thereof include oxygen, ozone, inert gases such as nitrogen and argon, and reducing gases such as hydrogen gas and forming gas. However, in the present invention, oxygen is preferably used as the carrier gas. Examples of carrier gases using oxygen include air, oxygen gas, and ozone gas, with oxygen gas and / or ozone gas being particularly preferred. In addition, the type of carrier gas may be one type, or two or more types, and a dilution gas with a changed carrier gas concentration (e.g., a 10-fold dilution gas, etc.) may also be used as a second carrier gas. In addition, the number of carrier gas supply points may be not only one, but also two or more. In the present invention, when an atomization chamber, a supply pipe, and a film-forming chamber are used, it is preferable to provide a carrier gas supply point in each of the atomization chamber and the supply pipe, and it is more preferable 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, 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, more preferably 0.1 to 1 L / min.

[0022] (Film Formation Process) In the film formation process, the atomized droplets are thermally reacted 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 forms a film from the mist, and the mist is reacted with heat. The reaction conditions are also not particularly limited as long as they do not impede the objectives of the present invention. In this process, the thermal reaction is typically carried out at a temperature equal to or higher than the evaporation temperature of the solvent, but preferably at a temperature not too high. In the present invention, the thermal reaction is preferably carried out at a temperature of 700°C to 800°C. Furthermore, the thermal reaction may be carried out under any of the following atmospheres: vacuum, non-oxygen atmosphere, reducing gas atmosphere, and oxidizing atmosphere, as long as it does not impede the objectives of the present invention. It may also be carried out under atmospheric pressure, pressurized atmosphere, or reduced pressure. However, in the present invention, an oxidizing atmosphere is preferred, and atmospheric pressure is also preferred, with an oxidizing atmosphere and atmospheric pressure being more preferred. 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 of a raw material solution containing an oxidizing agent. The film thickness can be set by adjusting the film formation time.

[0023] In an embodiment of the present invention, a film may be formed directly on the substrate, or other layers such as a layer different from the oxide semiconductor (e.g., an n-type semiconductor layer, an n+-type semiconductor layer, an n--type semiconductor layer, etc.), an insulator layer (including a semi-insulator layer), or a buffer layer may be stacked 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 reduce the difference in lattice constant between the crystal substrate and the oxide semiconductor. Examples of materials constituting the buffer layer include SnO ２ , TiO ２ , V.O. ２ , MnO ２ , RuO ２ , CsO ２ , IrO ２ , GeO ２ , CuO ２ , PbO ２ , AgO ２ , CrO ２, SiO ２ and mixed crystals thereof.

[0024] The oxide semiconductor obtained as described above is useful for semiconductor devices, particularly power devices, and is preferably 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 and TFTs such as MIS and HEMT, Schottky barrier diodes using semiconductor-metal junctions, JBS, PN or PIN diodes combined with other P layers, and light-emitting / receiving elements. In addition to the above, the oxide semiconductor of the present invention can also be suitably used for photoelectric conversion elements, gas sensors, photoelectrodes, memories, and the like. In an embodiment of the present invention, the oxide semiconductor may be used as the oxide semiconductor in a semiconductor device, with the crystal substrate removed as desired, or may be used as a crystalline layered structure with the crystal substrate in a semiconductor device. In particular, when the crystal substrate is a conductive substrate, the crystalline layered structure can be suitably applied to semiconductor devices (vertical devices).

[0025] The semiconductor device can be suitably used as either a horizontal element (horizontal device) in which an electrode is formed on one side of a semiconductor layer, or a vertical element (vertical device) in which electrodes are formed on both the front and back sides of a semiconductor layer, but in the embodiments of the present invention, it is preferably used as a vertical device. Suitable examples of the semiconductor device include a Schottky barrier diode (SBD), a junction barrier Schottky diode (JBS), a metal semiconductor field effect transistor (MESFET), a high electron mobility transistor (HEMT), a metal oxide semiconductor field effect transistor (MOSFET), a static induction transistor (SIT), a junction field effect transistor (JFET), an insulated gate bipolar transistor (IGBT), and a light emitting diode (LED).

[0026] Hereinafter, preferred examples of the semiconductor device in which the oxide semiconductor of the present invention is applied to an n-type semiconductor layer (an n+ type semiconductor, an n- type semiconductor layer, or the like) will be described with reference to the drawings, but the present invention is not limited to these examples.

[0027] 3 shows an example of a Schottky barrier diode (SBD) according to an embodiment of the present invention. The SBD in FIG. 3 includes 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 the Schottky electrode and the ohmic electrode may be known electrode materials, and examples of the electrode materials 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, and Ag, or alloys thereof; conductive metal oxide films such as tin oxide, zinc oxide, rhenium oxide, indium oxide, indium tin oxide (ITO), and indium zinc oxide (IZO); organic conductive compounds such as polyaniline, polythiophene, and polypyrrole; and mixtures and laminates thereof.

[0029] The Schottky electrode and the ohmic electrode can be formed by known means such as, for example, vacuum deposition or sputtering. More specifically, for example, when a Schottky electrode is formed using two types of metals, a first metal and a second metal, the Schottky electrode can be formed by stacking a layer made of the first metal and a layer made of the second metal, and then patterning the layer made of the first metal and the layer made of the second metal using a photolithography technique.

[0030] 3, a depletion layer (not shown) expands into the n-type semiconductor layer 101a, resulting in a high breakdown voltage SBD. Furthermore, when a forward bias is applied, electrons flow from the ohmic electrode 105b to the Schottky electrode 105a. Thus, an SBD using this semiconductor structure is excellent for high breakdown voltage and large current applications, has fast switching speed, and excels in breakdown voltage and reliability.

[0031] (JBS) Figure 4 shows a junction barrier Schottky diode (JBS) according to a preferred embodiment of the present invention. The semiconductor device of 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 disposed on the n- type semiconductor layer and capable of forming a Schottky barrier between the i-type semiconductor layer and the Schottky electrode 2, and a p-type semiconductor layer 1 disposed 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, the p-type semiconductor layers are preferably disposed at regular intervals, and more preferably, the p-type semiconductor layers are disposed between both ends of the Schottky electrode and the n- type semiconductor layer. This preferred embodiment results in a JBS configured to have superior thermal stability and adhesion, reduced leakage current, and superior semiconductor properties such as breakdown voltage. The semiconductor device of Figure 4 also includes an ohmic electrode 5 on the n+ type semiconductor layer 4.

[0032] 4 may be formed by any known method without particular limitation as long as it does not impede the object of the present invention, such as forming a film by vacuum deposition, CVD, sputtering, or various coating techniques, followed by patterning by photolithography, or directly patterning by printing or the like.

[0033] (MOSFET) An example of a case where the semiconductor device of the present invention is a MOSFET is shown in Fig. 5. The MOSFET in Fig. 5 is a trench MOSFET, and includes 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 having a thickness of, for example, 100 nm to 100 μm is formed on the drain electrode 135c, and an n- type semiconductor layer 131a having 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, a plurality of trenches are formed in the n-type semiconductor layer 131a and the n+ type semiconductor layer 131c, each of which has a depth that penetrates the n+ semiconductor layer 131c and reaches partway through the n- type semiconductor layer 131a. A gate electrode 135a is embedded in the trenches via a gate insulating film 134 having a thickness of, for example, 10 nm to 1 μm.

[0036] 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 with respect 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 is turned on. When the voltage of the gate electrode is set to 0V, no channel layer is formed, and the n-type semiconductor layer 131a is filled with a depletion layer, resulting in the MOSFET being turned 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 includes an n-type semiconductor layer 121a with a wide bandgap, an n-type semiconductor layer 121b with a narrow bandgap, 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 an embodiment of the present invention, for example, it is also preferable to use the oxide semiconductor for the n-type semiconductor layer 121a with a wide bandgap and to use Ge for the n-type semiconductor layer 121b with a narrow bandgap.

[0038] In the above example, a p-type semiconductor is not used, but embodiments of the present invention are not limited to this and a p-type semiconductor may be used. Examples using a p-type semiconductor are shown in Figures 6 to 8 and Figures 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 be made of the same material as the n-type semiconductor and contain a p-type dopant.

[0039] 6 shows a preferred example of a metal oxide semiconductor field effect transistor (MOSFET) including 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 may be the same as the p-type semiconductor layer 132.

[0040] (IGBT) FIG. 7 shows a preferred example of an insulated gate bipolar transistor (IGBT) including 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) Fig. 8 shows an example of a semiconductor device according to an embodiment of the present invention that is a light-emitting diode (LED). The semiconductor light-emitting device of Fig. 8 includes an n-type semiconductor layer 161 on a second electrode 165b, and a light-emitting layer 163 is stacked on the n-type semiconductor layer 161. A p-type semiconductor layer 162 is stacked 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 stacked on the translucent electrode 167. The semiconductor light-emitting device of Fig. 8 may be covered with a protective layer except for the electrode portion.

[0042] Examples of materials for the translucent electrode include conductive oxide materials containing indium (In) or titanium (Ti). ２ O ３ , ZnO, SnO２ , Ga ２ O ３ , TiO ２ , CeO ２ Alternatively, a mixed crystal of two or more of these materials or a doped material thereof may be used. A translucent electrode can be formed by applying these materials by a known method such as sputtering. After the formation of the translucent electrode, thermal annealing may be performed to make the translucent electrode transparent.

[0043] In the semiconductor light-emitting device of FIG. 8, the first electrode 165a is a positive electrode and the second electrode 165b is a negative electrode, and current is passed through these electrodes to the p-type semiconductor layer 162, the light-emitting layer 163, and the n-type semiconductor layer 161, causing the light-emitting layer 163 to emit 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, and Ag, or alloys thereof; conductive metal oxide films such as tin oxide, zinc oxide, indium oxide, indium tin oxide (ITO), and indium zinc oxide (IZO); organic conductive compounds such as polyaniline, polythiophene, and polypyrrole; and mixtures thereof. The method for forming the electrodes is not particularly limited, and they can be formed on the substrate by 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 for the materials.

[0045] (Gas Sensor) FIG. 14 shows an example of a gas sensor according to an embodiment of the present invention. The gas sensor of FIG. 14 includes a first layer 11, a second layer 12, a first electrode 13, and a second electrode 14. The first layer and the second layer may be n-type or p-type semiconductor layers. The work function of the second layer is smaller than the work function of the first layer. The second layer and the first electrode preferably form a Schottky junction. The first layer and the second electrode preferably 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, and platinum. 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) FIG. 15 shows an example of a photoelectric conversion element according to an embodiment of the present invention. The photoelectric conversion element of FIG. 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 of FIG. 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 in this order on a lower electrode 51. The stacking order of the electron blocking layer 56a, the photoelectric conversion layer 52, and the hole blocking layer 56b in FIG. 15( b) may be changed as appropriate depending on the application and characteristics. The oxide semiconductor of the present invention may be used, for example, for the photoelectric conversion layer 52, the electron blocking layer 56a, or the hole blocking layer 56b. In the photoelectric conversion element of FIG. 15 , light is preferably incident on the photoelectric conversion layer 52 through the upper electrode 55. Such a photoelectric conversion element can be suitably used as an optical sensor and an imaging element.

[0047] (Photodetector) FIG. 16 shows an example of a photodetector according to an embodiment of the present invention. The photodetector of FIG. 16 includes a lower electrode 40, a high-concentration n-type layer 41, a low-concentration n-type layer 42, a high-concentration p-type layer 43, a Schottky electrode 44, an upper electrode 45, and a specific region 46. The materials for the lower electrode 40, the Schottky electrode 44, and the upper electrode 45 may be known electrode materials (e.g., Au, Ni, Pb, Rh, Co, Re, Te, Ir, Pt, Se, etc.). The specific region 46 is, for example, a high-concentration n-type region. In this embodiment of the present invention, the oxide semiconductor can be suitably used for the high-concentration n-type layer 41, the low-concentration n-type layer 42, the high-concentration p-type layer 43, the specific region 46, etc. In the light-receiving element of FIG. 16 , eye-safe band light is incident through the window portion of the upper electrode 45, and when the light is absorbed by free electrons in the Schottky electrode 44, electrons are emitted toward 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) FIG. 17 shows an example of a photoelectrode according to an embodiment of the present invention. The photoelectrode of FIG. 17 includes a substrate 31, a conductor layer (electron conduction layer) 32 provided on the substrate 31, and a photocatalytic layer (light absorption layer) 33 provided on the conductor layer 32. The substrate 31 may be, for example, a glass substrate or a sapphire substrate. In an embodiment of the present invention, the substrate 31 may be any of the above-mentioned crystal substrates. The thickness of the conductor 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, when 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 conductor layer 32 so that the energy difference between the vacuum level and the Fermi level of the conductor 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 between the photocatalytic layer 33 and the conductor layer 32 so that the energy difference between the vacuum level and the Fermi level of the conductor layer 32 is larger than the energy difference between the vacuum level and the Fermi level of the photocatalytic layer 33. In an embodiment of the present invention, the oxide semiconductor can be suitably used for the conductor layer 32 and / or the photocatalytic layer 31. The photoelectrode of Figure 17 is suitably used for, for example, a photoelectrochemical cell or the like.

[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 to exert the above-mentioned functions. 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). Fig. 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 Fig. 10 is a circuit diagram of the same control system, which is particularly suitable for installation in an electric vehicle.

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

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

[0052] Meanwhile, various sensors (not shown) measure actual values ​​such as wheel rotation speed, torque, and accelerator pedal depression (acceleration amount) from the electric vehicle while it is running, 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 a memory. It generates a control signal using the input measurement signal and outputs it as a feedback signal to the inverter 504, thereby controlling the switching operation of the switching elements. This instantly corrects the AC voltage provided by the inverter 504 to the motor 505, enabling accurate operation control of the electric vehicle and ensuring safe and comfortable operation of the electric vehicle. The output voltage to the inverter 504 can also be controlled by providing a feedback signal from the drive control unit 506 to the boost converter 502.

[0053] 10 shows the circuit configuration of FIG. 9 excluding the step-down converter 503, i.e., the circuit configuration showing only the configuration for driving the motor 505. As shown in the figure, the semiconductor device of the present invention is used, for example, as a Schottky barrier diode in a step-up converter 502 and an inverter 504 to provide switching control. 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. Note that current is stabilized by inserting an inductor (such as a coil) into the output of the battery 501, and voltage is stabilized by inserting capacitors (such as an electrolytic capacitor) between the battery 501, the step-up converter 502, and the inverter 504.

[0054] 10, the drive control unit 506 includes a calculation unit 507 consisting of a CPU (Central Processing Unit) and a storage unit 508 consisting of a non-volatile memory. Signals input to the drive control unit 506 are given to the calculation unit 507, which performs the necessary calculations to generate feedback signals for each semiconductor element. The storage unit 508 also temporarily stores the results of calculations performed by the calculation unit 507, and accumulates physical constants and functions required for drive control in the form of a table and outputs them to the calculation unit 507 as appropriate. The calculation unit 507 and storage unit 508 can be configured as known units, and their processing capabilities can also be selected as desired.

[0055] As shown in FIGS. 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 operations of the boost converter 502, the buck converter 503, and the inverter 504. Furthermore, by applying the semiconductor device according to the present invention, excellent switching characteristics can be expected, and further miniaturization and cost reduction of the control system 500 can be realized. That is, the effects of the present invention can be expected for each of the boost converter 502, the buck converter 503, and the inverter 504. The effects of the present invention can also be expected for any one of these, any combination of two or more of these, or any configuration including the drive control unit 506. The semiconductor device according to the present invention can be applied to the control system 500 described above not only in the control system for an electric vehicle, but also in control systems for various purposes, such as boosting and bucking power from a DC power source or converting DC to AC power. Furthermore, a power source such as a solar cell can be used as the battery.

[0056] FIG. 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 FIG. 12 is a circuit diagram of the same control system, which is suitable for installation in infrastructure equipment, home appliances, and the like that operate on power from an AC power source.

[0057] As shown in FIG. 11 , the control system 600 receives power from an external, e.g., three-phase AC power source (power source) 601. The control system 600 includes an AC / DC converter 602, an inverter 604, a motor (drive target) 605, and a drive control unit 606, which can be mounted on various devices (described later). The three-phase AC power source 601 is, for example, a power generation facility (such as a thermal power plant, a hydroelectric power plant, a geothermal power plant, or a nuclear power plant) operated by an electric power company. The output of the three-phase AC power source 601 is stepped down via a substation and supplied as AC voltage. Alternatively, the AC / DC converter 602 may be installed in a building or a nearby facility and supplied with power via a power cable in the form of a private generator. The AC / DC converter 602 is a voltage conversion device that converts AC voltage to DC voltage. It converts the 100V or 200V AC voltage supplied from the three-phase AC power source 601 to a predetermined DC voltage. Specifically, the voltage conversion converts the DC voltage to a commonly used desired voltage, such as 3.3V, 5V, or 12V. If the drive target is a motor, the voltage 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] Inverter 604 converts the DC voltage supplied from AC / DC converter 602 into a three-phase AC voltage by switching operation and outputs it to motor 605. Motor 604 has a different form depending on the controlled object, but is a three-phase AC motor for driving wheels if the controlled object is a train, pumps and various power sources if the controlled object is factory equipment, or compressors if the controlled object is a home appliance, and is rotationally driven by the three-phase AC voltage output from inverter 604, and transmits the rotational driving force to a driven object (not shown).

[0059] It should be noted that, for example, among home appliances, there are many devices to be driven that can be supplied with the DC voltage output from AC / DC converter 302 as is (for example, personal computers, LED lighting equipment, video equipment, audio equipment, etc.), in which case inverter 604 is not required in control system 600, and the DC voltage is supplied to the device to be driven from AC / DC converter 602, as shown in Fig. 11. In this case, for example, a personal computer or the like is supplied with a DC voltage of 3.3 V, and an LED lighting equipment or the like is supplied with a DC voltage of 5 V.

[0060] Meanwhile, various sensors (not shown) are used to measure actual values ​​such as the rotation speed and torque of the driven object, or the temperature and flow rate of the environment surrounding the driven object, and 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 to control the switching operation of the switching elements. This allows the AC voltage provided by the inverter 604 to be instantly corrected, thereby 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 by a DC voltage, it is also possible to feedback control the AC / DC converter 602 instead of feedback to the inverter.

[0061] FIG. 12 shows the circuit configuration of FIG. 11 . As shown in the figure, the semiconductor device of the present invention is employed as, for example, a Schottky barrier diode in an AC / DC converter 602 and an inverter 604 to provide switching control. The AC / DC converter 602 uses, for example, a bridge-shaped circuit configuration of Schottky barrier diodes, and performs DC conversion by converting the negative voltage component of the input voltage into a positive voltage and rectifying it. The inverter 604 is incorporated into a switching circuit of an IGBT to perform switching control. An inductor (e.g., a coil) is interposed between the three-phase AC power supply 601 and the AC / DC converter 602 to stabilize the current, and a capacitor (e.g., an electrolytic capacitor) is interposed between the AC / DC converter 602 and the inverter 604 to stabilize the voltage.

[0062] 12, the drive control unit 606 includes a calculation unit 607 consisting of a CPU and a storage unit 608 consisting of a non-volatile memory. Signals input to the drive control unit 606 are given to the calculation unit 607, which performs the necessary calculations to generate feedback signals for each semiconductor element. The storage unit 608 also temporarily stores the results of calculations performed by the calculation unit 607, and accumulates physical constants and functions required for drive control in the form of a table and outputs them to the calculation unit 607 as appropriate. The calculation unit 607 and storage unit 608 can be configured as known units, and their processing capabilities can be selected as desired.

[0063] 11 and 12 , in this control system 600, 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 realized. In other words, the effects of the present invention can be expected for each of the AC / DC converter 602 and the inverter 604, and the effects of the present invention can be expected in any one of them, or in a combination thereof, or in any form including the drive control unit 606.

[0064] 11 and 12 show a motor 605 as an example of a device to be driven, but the device is not necessarily limited to a mechanically operated device, and can be many devices that require AC voltage. The control system 600 can be applied as long as it inputs power from an AC power source to drive the device to be driven, and can be installed for drive control of devices such as infrastructure equipment (for example, power equipment in buildings and factories, communication equipment, traffic control equipment, water and sewage treatment equipment, system equipment, labor-saving equipment, trains, etc.) and home appliances (for example, refrigerators, washing machines, personal computers, LED lighting equipment, video equipment, audio equipment, etc.).

[0065] Example 1 1. Film Formation Apparatus The mist CVD apparatus used in this example will be described with reference to Figure 1. The mist CVD apparatus 19 includes a susceptor 21 on which a substrate 20 is placed, a carrier gas supply means 22a for supplying a carrier gas, a flow rate control valve 23a for adjusting the flow rate of the carrier gas delivered from the carrier gas supply means 22a, a carrier gas (dilution) supply means 22b for supplying a carrier gas (dilution), a flow rate control valve 23b for adjusting the flow rate of the carrier gas delivered from the carrier gas (dilution) supply means 22b, a mist generator 24 containing a raw material solution 24a, a container 25 containing water 25a, an ultrasonic vibrator 26 attached to the bottom 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 supply pipe 27. The susceptor 21 is made of quartz, and the surface on which the substrate 20 is placed is inclined relative to the horizontal. By fabricating both the supply pipe 27 and the susceptor 21 that form the film formation chamber from quartz, impurities originating from the apparatus are prevented from being mixed into the film formed on the substrate 20 .

[0066] 2. Preparation of raw material solution To a 0.005 M aqueous solution of bis[2-carboxyethylgermanium(IV)]sesquioxide (C6H10Ge2O7), 10% by volume of hydrochloric acid (HCl) was added, and antimony acetate was further mixed in such that the atomic ratio of antimony to germanium was 0.0005. This was used as a raw material solution.

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

[0068] Next, the ultrasonic vibrator 26 was vibrated at 2.4 MHz, and the vibration was propagated to the raw material solution 24a through the water 25a, thereby atomizing the raw material solution 24a and generating mist (atomized droplets) 24b. This mist 24b was introduced into the film-forming chamber 30 through the supply pipe 27 by the carrier gas, and the mist reacted thermally on the substrate 20 at 750°C under atmospheric pressure, forming GeO ２ A film was formed.

[0069] Example 2 Bis[2-carboxyethylgermanium(IV)]sesquioxide (C ６ H １０ Ge ２ O ７ The procedure of Example 1 was repeated except that the concentration of GeO ２ A film was formed.

[0070] Example 3 GeO was prepared in the same manner as in Example 1, except that the concentration of antimony acetate in the raw material solution was adjusted so that the atomic ratio of antimony to germanium was 1:0.001. ２ A film was formed.

[0071] Example 4 Bis[2-carboxyethylgermanium(IV)]sesquioxide (C) in the source solution ６ H １０ Ge ２ O ７ The GeO was prepared in the same manner as in Example 1, except that the concentration of antimony acetate was 0.01 M (mol / L) and the atomic ratio of antimony to germanium was 1:0.001. ２ A film was formed.

[0072] GeO obtained in Examples 1 to 4 ２ The Hall effect measurement of the film revealed that the carrier type was "n". ２ The carrier density of the film is 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. ２The resistivity of the film is shown in Figure 2. As is clear from Figure 2, the resistivity can be effectively reduced 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]

[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 and electrical equipment components, optical and electrophotographic related devices, and industrial materials, but is particularly useful for semiconductor devices and materials therefor.

[0075] REFERENCE SIGNS LIST 1 p-type semiconductor layer 2 Schottky electrode 3 n-type semiconductor layer 4 n+ type semiconductor layer 5 ohmic electrode 11 first layer 12 second layer 13 first electrode 14 second electrode 19 mist CVD apparatus 20 substrate (crystal substrate) 21 susceptor 22a carrier gas supply means 22b carrier gas (dilution) supply means 23a flow rate control valve 23b flow rate control valve 24 mist generating source 24a raw material solution 25 container 25a water 26 ultrasonic vibrator 27 supply pipe 28 heater 29 exhaust port 31 substrate 32 conductor layer (electron conduction layer) 33 photocatalytic layer (light absorption layer) 40 lower electrode 41 high concentration n-type layer 42 low concentration n-type layer 43 high concentration p-type layer 44 Schottky electrode 45 Upper electrode 46 Specific region 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 Wide band gap n-type semiconductor layer 121b Narrow band gap 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 Gate electrode 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 insulating film 155a Gate electrode 155b Emitter electrode 155c Collector electrode 161 n-type semiconductor layer 162 p-type semiconductor layer 163 Light-emitting layer 165a First electrode 165b Second electrode 167 Light-transmitting electrode500 Control system 501 Battery (power source) 502 Step-up converter 503 Step-down converter 504 Inverter 505 Motor (drive object) 506 Drive control unit 507 Calculation unit 508 Storage unit 600 Control system 601 Three-phase AC power supply (power source) 602 AC / DC converter 604 Inverter 605 Motor (drive object) 606 Drive control unit 607 Calculation unit 608 Storage unit

Claims

1. An oxide semiconductor containing an oxide of germanium, having a carrier density of 1.0×10 １８ / cm ３ or more, An oxide semiconductor in which the atomic ratio of germanium among the metal elements in the oxide semiconductor is greater than 0.5, having an n-type conductivity type.

2. An oxide semiconductor containing a germanium oxide, having a carrier density of 1.0×10 18 / cm 3 or more, containing a dopant, wherein the dopant includes a Group 15 metal in the periodic table.

3. The oxide semiconductor according to Claim 2, wherein the dopant is antimony.

4. The oxide semiconductor according to any one of Claims 1 to 3, having a resistivity of 10 Ωcm or less.

5. The oxide semiconductor according to any one of Claims 1 to 4, being in a film form.

6. A semiconductor device comprising at least the oxide semiconductor according to Claim 5 and an electrode.

7. A power conversion device using the semiconductor device according to Claim 6.

8. A control system using the semiconductor device according to Claim 6.

9. A method for manufacturing an oxide semiconductor according to any one of Claims 1 to 8, comprising: atomizing or dropletizing a raw material solution containing a dopant element and germanium, and having a higher content of germanium than the dopant element; supplying a carrier gas to the obtained atomized droplets; transporting the atomized droplets to the substrate with the carrier gas; and then thermally reacting the atomized droplets on the substrate.