KR20070099591A - Functional device and method for forming oxide material - Google Patents

Abstract

There have been demands on transparent electrode materials and magnetic materials having a wide range of applications. Disclosed are a novel functional device and a method for forming an oxide material for meeting such demands. Specifically disclosed is a functional device comprising an AlxGayInzN base (wherein 0 <= x <= 1, 0 <= y <= 1, 0 <= z <= 1) and an oxide material composed of a metal oxide which is formed on the Alx GayInzN base. This functional device is characterized in that the metal oxide is TiO2 or the like. In this functional device, a film which hardly reflects at the interface and has both chemical resistance and durability is integrally formed on a group III nitride having excellent physical and chemical properties.

Description

FUNCTIONAL DEVICE AND METHOD FOR FORMING OXIDE MATERIAL}

The present invention relates to an oxide material.

In recent years, the necessity for making a display panel large and small portable is increasing. In order to realize this, it is necessary to lower the power consumption of the display element, and application of a transparent electrode having a high visible light transmittance and a low resistance value is essential.

For this reason, in order to further lower the resistance of the transparent conductive thin film, an indium tin oxide film (hereinafter referred to as an ITO film) made of indium oxide doped with tin by several percent on a surface of a transparent substrate such as a glass plate is used. What was formed is proposed (for example, refer patent document 1).

However, this ITO film is excellent in transparency and has high conductivity, but has a drawback that the crust content of In is low at 50 ppb, and the cost of the raw material increases with the depletion of resources.

In particular, zinc oxide-based materials have recently been proposed as materials having high plasma resistance and being inexpensive.

However, zinc oxide-based materials are vulnerable to acids and alkalis and gradually erode even in a carbon dioxide atmosphere. It is also conceivable to cope by coating the zinc oxide surface in order to improve such chemical resistance, but there is also a problem that the coating process must be increased once and the manufacturing cost increases.

That is, in order to expand the application range of a transparent conductor, it is necessary to comprise this with the material which can be supplied stably, and to comprise this material also having chemical resistance and durability.

Therefore, titanium dioxide (TiO ₂ ) having both chemical resistance and durability is attracting attention (see, for example, Non Patent Literature 1), and the TiO ₂ film is epitaxially grown on a sapphire substrate or the like (for example, non-patent). See Documents 2, 3 and 4).

However, with the use of a sapphire substrate, the function by bonding (heterobonding) the heterogeneous material between the substrate material and the thin film material cannot be used, and it is difficult to function the sapphire substrate as more than a simple structural material.

Patent Document 1: Japanese Patent Application Publication No. 2004-95240

Non-Patent Document 1: Applied Physics Vol. 73, No. 5 (2004) 587 to 592

Non Patent Literature 2: Jpn. J. Appl. Phys. Vol. 40 (2001) pp. L 1204 to L 1206

Non-Patent Document 3: Nature Materials 3, 221-224 (2004)

Non-Patent Document 4: APPLIED PHYSICS LETTERS VOLUME 78, NUMBER 18, 2664-2666 (2001)

Accordingly, the present invention has been made in view of the above circumstances, and an object thereof is to provide a functional element and an oxide material forming method having new characteristics.

According to the present invention, in order to achieve the above object, a configuration as described in the claims is employed. EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

A first aspect of the present invention is Al _x Ga _y In _z N (where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1),

It is formed on the said Al _x Ga _y In _z N, and has an oxide material which consists of a metal oxide,

The metal oxide is a functional element, characterized in that the TiO ₂ .

According to this configuration, on the group III nitride having excellent physical and chemical properties, low reflection at the interface, to obtain a functional device that is configured to form integrally TiO ₂ film, and chemical resistance combined with durability.

According to a second aspect of the present invention, an oxide material made of a metal oxide is applied to a pulse laser deposition method on Al _x Ga _y In _z N (where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, and 0 ≦ z ≦ 1). Is formed by

The metal oxide is TiO ₂ in the method of forming an oxide material.

According to this configuration, a high quality TiO ₂ epitaxial film having a small contact resistance and small scattering at an interface can be formed on the Group III nitride having excellent physical and chemical properties.

According to a third aspect of the present invention, Al _x Ga _y In _z N (where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1),

It is formed on the said Al _x Ga _y In _z N, and has an oxide material which consists of a metal oxide,

The metal oxide is in the functional element, characterized in that SnO ₂ .

According to this configuration, the excellent physical and chemical properties of the functional device is configured to form integrally on the Group III nitride, a low reflection at the interface, SnO ₂ films that combine the chemical resistance and durability, having obtained.

According to a fourth aspect of the present invention, an oxide material made of a metal oxide is coated on a pulse laser deposition method on Al _x Ga _y In _z N (where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, and 0 ≦ z ≦ 1). Is formed by

The metal oxide is an oxide material forming method, characterized in that SnO ₂ .

According to this configuration, a high-quality SnO ₂ epitaxial film having a small contact resistance and small scattering at the interface can be formed on the group III nitride having excellent physical and chemical properties.

In addition, Al _x Ga _y In _z N (where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, and 0 ≦ z ≦ 1) as used in the present specification and claims are to be x + y + z = 1. In this case, the case where all are not doped, the case where the transition metal, Si, Mg, Zn, etc. are doped, the case of p-type semiconductor, n-type semiconductor, etc. are included.

According to the present invention, a functional element formed by integrally forming a film having little reflection at the interface and having chemical resistance and durability on a Group III nitride having excellent physical and chemical properties is obtained.

Other objects, features or advantages of the present invention will become apparent from the following detailed description based on the embodiments of the present invention and the accompanying drawings.

1 is a view showing an oxide material film formed on a substrate.

Fig. 2 is a view showing the RHEED pattern of the substrate before the pretreatment and the RHEED pattern of the substrate after the pretreatment.

3 is a diagram for explaining the configuration of a PLD device.

Fig. 4 is a diagram showing a crystal structure of GaN (wurtzite (wurtzite type) Al _x Ga _y In _z N).

5 shows four levels according to the crystal quality [(A) Level 1: polyphase polycrystalline film, (B) Level 2: single-phase polycrystalline film, (C) level 3: single-phase oriented epitaxial film, and (D) level 4 : Single crystal epitaxial film].

Fig. 6 is a diagram showing an electron beam diffraction image (RHEED pattern) between a TiO ₂ surface formed by the PVD method described above on a GaN substrate subjected to hydrochloric acid treatment and a GaN substrate surface before film formation.

Fig. 7 is a diagram showing an electron beam diffraction image (RHEED pattern) between a TiO ₂ surface formed by PVD on a GaN substrate not subjected to hydrochloric acid treatment and a GaN substrate surface before film formation.

8 shows an atomic force microscope (AFM) image of the TiO ₂ surface formed by PVD on a GaN substrate subjected to hydrochloric acid treatment.

9 shows the results of measuring the internal transmittance of the metal oxide layer.

10 is a diagram showing temperature dependence in resistivity of a metal oxide layer.

Fig. 11 is a diagram showing the applied magnetic field dependence of the Faraday rotation coefficient at room temperature of Ti _{1 -x- y} Co _x Nb _y O ₂ .

Fig. 12 is a graph showing the wavelength dependence of the Faraday rotation coefficient at room temperature of Ti _{1 -x- y} Co _x Nb _y O ₂ .

Fig. 13 shows the external transmittance at room temperature of a TiO ₂ thin film co-added with Co 5% and Nb 10%.

Fig. 14 shows the compositional dependence of resistivity when a TiO ₂ film is formed while varying the amount of Nb doping.

Fig. 15 is a diagram showing the substrate temperature dependence of resistivity in the case where a TiO ₂ film having an Nb doping amount of 6% is formed while changing the substrate temperature during film formation.

Fig. 16 is a diagram showing wavelength dependence of transmittance when a TiO ₂ film having an Nb doping amount of 6% is formed.

Fig. 17 is a diagram showing substrate temperature dependence and oxygen partial pressure dependence of transmittance in the case where a TiO ₂ film having an Nb doping amount of 6% is formed.

18 is a diagram showing various measurement results using the film formation temperature gradient film.

Fig. 19 shows the results of X-ray diffraction (XRD) measurement of the SnO ₂ film formed by the PLD method.

Fig. 20 is a diagram showing an electron beam diffraction image (RHEED pattern) of a SnO ₂ film formed by a PLD method.

[Description of the code]

11: substrate

12: oxide material film

30: PLD device

31: chamber

32: optical oscillator

33: reflector

34: Lens

36: infrared lamp

39: target

40: oil rotary pump

41: non-return valve

42: Turbomolecular Pump

43: pressure valve

45: oxygen gas flow adjustment valve

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described in detail, referring drawings.

As shown in FIG. 1, an oxide material film 12 is formed on the substrate 11.

The substrate 11 is made of, for example, a GaN template (Si-doped n-type GaN manufactured by TDI, Inc.), whose substrate surface 11a is a (0001) plane.

In addition, the substrate 11 may be composed of Al _x Ga _y In _z N (where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, and 0 ≦ z ≦ 1).

The oxide material film 12 formed on the substrate 11 is made of metal oxide TiO ₂ .

In addition, TiO ₂ is not only doped with all, but M: TiO ₂ (M is any one of Nb, Ta, Mo, As, Sb, Al, W, Co, Fe, Cr, Sn, Ni, Mn or V). One or a combination thereof). As will be described later, if M doped is Nb, Ta, Mo, As, Sb, Al or W, the electrical conductivity can be improved while maintaining transparency. On the other hand, when M doped is Co, Fe, Cr, Sn, Ni, Mn or V, the magneto-optical effect can be expected.

Next, the manufacturing method of this oxide material film 12 is demonstrated.

First, a GaN substrate is processed. The procedure of this process is as follows, for example. The substrate is cleaned with acetone, ethanol or the like. Next, the substrate is immersed in high purity hydrochloric acid (EL grade, concentration 36%, manufactured by Kanto Chemical Co., Ltd.) for 2 minutes. Next, the substrate is transferred to pure water to rinse hydrochloric acid and the like. Next, the substrate is transferred to fresh pure water, and ultrasonic cleaning is performed here for 5 minutes. Next, the substrate is taken out from the pure water, nitrogen gas is blown off the surface of the substrate to remove moisture from the surface of the substrate. These treatments are performed at room temperature, for example.

By these treatments, oxides, organic substances, and the like are removed from the substrate surface, and it is considered that the Ga terminal, not the N terminal, appears on the substrate surface. Although the example which used hydrochloric acid was demonstrated here, you may use acids, such as aqua regia and hydrofluoric acid. In addition, the process may be room temperature, and you may use the heated acid.

In addition, after these processes, the board | substrate was introduce | transduced into the chamber 31 demonstrated below, and the state of the sample surface was evaluated by the reflection electron beam diffraction method (RHEED), and was heated at 400 degreeC. For comparison, the RHEED pattern of the substrate before the treatment and the RHEED pattern of the substrate after the treatment are shown in FIG. It turns out that the flat substrate surface is obtained from the streak pattern of the RHEED image of a board | substrate after a process.

Next, for example, Ta: TiO ₂ is deposited on the (0001) surface of the substrate 11 based on the physical vapor deposition (PVD) method. In the following embodiment, the case where such deposition is performed based on the pulsed laser deposition method (PLD method) is demonstrated.

In this PLD method, the oxide material film 12 is deposited on the substrate 11 using, for example, the PLD device 30 as shown in FIG. The PLD device 30 is configured by arranging the substrate 11 and the target 39 in the chamber 31, and is arranged on the side opposite to the target 39 surface outside the chamber 31. It is provided with the optical oscillator 32, the reflector 33 for adjusting the position of the pulse laser beam oscillated by the optical oscillator 32, the lens 34 for controlling the spot diameter of a laser beam, and also the chamber 31 It is comprised including the gas supply part 44 for injecting oxygen gas in the inside.

The chamber 31 is provided for producing a high quality thin film by maintaining an appropriate degree of vacuum and preventing the incorporation of impurities from the outside. In the chamber 31, an infrared lamp 36 for heating the substrate is provided. The substrate temperature is monitored by the radiation thermometer 37 provided outside the chamber 31 through the window 31b, and is controlled to always be a constant temperature. Moreover, the valve 45 for adjusting the flow volume of oxygen gas is attached to the chamber. In order to realize the film formation under reduced pressure, the turbomolecular pump 42 and the pressure valve 43 are connected to the chamber 31. The pressure of the chamber 31 is controlled to be 1 × 10 ⁻⁷ torr to 1 × 10 ⁻⁴ torr in, for example, an oxygen atmosphere using the oxygen gas flow rate adjusting valve 45 and the pressure valve 43. In addition, the oil rotary pump 40 and the non-return valve 41 are connected to the turbo molecular pump 42, and the pressure on the exhaust side of the turbo molecular pump 42 is always maintained at 1 × 10 ⁻³ torr or less. have.

The window 31a is further arrange | positioned at the surface which opposes the target 39 in this chamber 31, and the pulse laser beam from the light oscillator 32 enters through the window 31a. The optical oscillator 32 oscillates KrF excimer laser having a pulse frequency of 1 to 10 Hz, a laser power of 100 mJ / pulse, and a wavelength of 248 nm as the pulse laser light. The oscillated pulse laser light is spot-adjusted by the reflector 33 and the lens 34 so that the focal position is near the target 39, and the target 39 disposed in the chamber 31 through the window 31a. ) Is incident at an angle of about 45 ° to the surface.

The target 39 is composed of, for example, Ta: TiO ₂ sintered body. Although the metal to substitute takes Ta as an example here, any one of Nb, Mo, As, Sb, and W may be used, or you may use multiple types of metal together. The Ta: TiO ₂ sintered body is manufactured with the mixing the TiO ₂ and Ta ₂ O ₅ were weighed so that the atomic ratio of any powder, and further by heat molding this mixed powder. This target 39 is arrange | positioned so that it may become substantially parallel with respect to the (0001) surface in the board | substrate 11. As shown in FIG.

Further, the target 39 is Nb: the case consisting of a TiO ₂ sintered body, Nb: TiO ₂ sintered body, mixing the powder with a weighing TiO ₂ and Nb ₂ O ₅ so that the ratio of a desired atom, and further the mixed powder It is produced by heat molding. In the case where the target 39 is made of Co, Nb: TiO ₂ sintered body, the Co, Nb: TiO ₂ sintered body mixes each powder of TiO ₂ , Nb ₂ O _5, and CoO weighed so as to have a desired atomic ratio, It manufactures by heat-molding this mixed powder.

In addition, the film forming process based on this PLD method is as follows.

First, the preprocessed substrate 11 is installed in the chamber 31.

Next, for example, the pulse frequency is 2 kHz, the laser power is 100 mJ / pulse, the oxygen partial pressure is 1 × 10 ^-5 torr and the substrate temperature is set at 400 ° C., respectively, and the substrate is driven to rotate by the motor 35. The film formation is carried out for 40 minutes while making it. In addition, by intermittently irradiating the pulsed laser light while driving the target 39 through the rotation shaft 38, the temperature of the surface of the target 39 is raised rapidly to generate an ablation plasma. Ti, Ta, and O atoms contained in the ablation plasma move to the substrate 11 by gradually changing their states while repeating a collision reaction with oxygen gas in the chamber 31. Particles containing Ti, Ta, and O atoms that have reached the substrate 11 are diffused to the (0001) plane on the substrate 11 as they are, so that the lattice matching is thinned in the most stable state. Thereafter, the substrate is quenched to room temperature under an oxygen partial pressure of 1 × 10 ⁻⁵ torr. As a result, the oxide material film 12 is produced.

In general, in heteroepitaxial growth, it is known that lattice mismatch between a thin film and a substrate has a great influence on the generation of crystal defects in the thin film. Lattice mismatch,

Lattice mismatch = (afilm-asub) / asub

(afilm: lattice constant of thin film, asub: lattice constant of substrate crystal)

It is represented by The larger this value, the larger the lattice mismatch, and the more difficult the epitaxial growth. As shown in Table 1 and Fig. 4, the crystal structure of GaN and the crystal structure of TiO ₂ are completely different.

Table 1

(* Non-Patent Document 5)

(** Non-Patent Documents 6, 7 and 8)

Non-Patent Document 5: The Blue Laser Diode, S. Nakamura et al., Springer

[Non-Patent Document 6] Noguchi Chuojiro: Titanium Oxide, Glazes, and Ceramics Titanium N0.44P.11-13 (1956)

[Non-Patent Document 7] Katao Kazuo: Titanium Oxide, Gogyo Titanium Zirconium, vol. 12 N0.12 P. 8, 9 (1964)

Non-Patent Document 8: Shin-Kosa Co., Ltd. Homepage

Therefore, it was expected that it would be difficult to form a TiO ₂ film on a GaN substrate. However, as a result of attempting to grow a TiO ₂ film on a GaN substrate at this time, it was found that the TiO ₂ film was epitaxially grown on GaN as expected.

As described above, it has been found that the oxide material film 12 can be formed by the PLD method. However, the present invention is not limited to the above-described PLD method. For example, other physical vapor deposition (PVD) methods such as molecular beam epitaxial (MBE) method or sputtering method, or methods other than PLD method, for example, using MOCVD method The oxide material film 12 may be formed on the basis of chemical vapor deposition (CVD).

As shown in Figs. 5A to 5D, in general, when a film is produced by a crystal growth technique, four levels ((A) level 1: polyphase polycrystalline film, (B) level 2: single phase polycrystalline film, (C) level 3: single phase oriented epitaxial film, and (D) level 4: single crystal epitaxial film]. In addition, in this specification and a claim, a single phase film refers to level 2 or more, and an epitaxial film refers to level 3 or more.

For example, other physical vapor deposition (PVD) methods such as molecular beam epitaxial (MBE) method or sputtering method, or a method other than PLD method, for example, chemical vapor deposition (CVD) method using MOCVD method, level 2 or more It is thought that a film will be formed.

6 shows an electron beam diffraction image (RHEED pattern) between the TiO ₂ surface formed by the PVD method described above on the GaN substrate subjected to the hydrochloric acid treatment described above and the GaN substrate surface before film formation. 7 shows an electron beam diffraction image (RHEED pattern) between the TiO ₂ surface formed by the PVD method on the GaN substrate not subjected to hydrochloric acid treatment and the surface of the GaN substrate before film formation.

A clear streak pattern was observed on the TiO ₂ surface, indicating that it is epitaxially growing. By using this result together with X-ray diffraction (XRD), it was confirmed by the PLD method that a film of level 3 or higher was formed.

In addition, when the GaN substrate is processed, it can be seen that a flat and crystallinity TiO ₂ film is obtained from the streak pattern on the RHEED.

8 shows an atomic force microscope (AFM) image of the TiO ₂ surface formed by PVD on a GaN substrate subjected to hydrochloric acid treatment. The average value of the surface roughness was 0.2 nm. From these, it can be seen that very high flatness TiO ₂ film is obtained.

6, 7 and 8, the substrate temperature at the time of film formation was 400 deg. C, and Ta was doped to 1% in the TiO ₂ film. In addition, the same clear streak pattern was observed even when no other element was doped in the TiO ₂ film.

Next, the characteristics of M: TiO ₂ created by the above-described method will be described.

Table 2 shows the properties of Ta: TiO ₂ prepared on GaN substrates.

[Table 2]

In addition, the tester was used for the measurement of the resistance value at this time.

As can be seen from this table, in order to reduce the resistance value, the substrate temperature at the time of film formation is preferably set to 320 ° C or higher and 550 ° C or lower. In addition, in order to make resistance smaller, it is preferable to make the substrate temperature at the time of film-forming into 320 degreeC or more and 450 degrees C or less. The temperature of 320 ° C or higher and 550 ° C is lower than the general growth temperature (700 ° C or higher) required by the organometallic vapor phase growth method (MOCVD method) or the molecular beam epitaxy method (MBE method) which is the mainstream as the crystal growth method of nitride. Therefore, it is preferable that a board | substrate temperature is 320 degreeC or more and 550 degrees C or less also in the point which has an influence on a board | substrate. Moreover, the film formation at low temperature can also prevent the problem of the thermal deformation in a sample cooling process. In addition, low-temperature growth with low reactivity is desired even in combination with other materials. Therefore, from these viewpoints, it is more preferable that the substrate temperature at the time of film formation is 320 degreeC or more and 400 degrees C or less. Moreover, there is a high possibility that the film can be formed even between room temperature and 320 degrees.

Al _x Ga _y In _z N is often used as a semiconductor material of an electronic device such as an optical semiconductor such as a light emitting diode or a semiconductor laser, a power device, or a light emitting element. In order to raise luminous efficiency without changing these internal structures, application of the oxide material film 12 of this invention as a transparent electrode can be considered. Here, the refractive indices of GaN, TiO ₂ , and ZnO are about 2.5, about 2.5, and about 2.0, respectively, and the combination of GaN and transparent electrode TiO ₂ has less reflection at the interface than the combination of GaN and transparent electrode ZnO. Therefore, in order to increase the efficiency of light emission it can be seen that advantageous to use a transparent electrode consisting of TiO _2. It is also possible to adjust the amount of doping of other elements to TiO _{2 in} order to reduce the refractive index difference.

It is also conceivable to apply the oxide material film 12 of the present invention as a transparent electrode of a surface emitting laser. In this case, since the transparent electrode can be disposed even in the light emitting area, the area of the electrode can be large, and there is an advantage also from the viewpoint of efficient injection of current into the active layer.

In the light emitting element or the like, it is generally conceivable to provide a transparent electrode on the p-type semiconductor layer, but the transparent electrode may be in contact with the n-type semiconductor layer as necessary.

Next, Nb: TiO _{2 -} and describes the collection of internal transmittance of the (formula _{Ti 1 x Nb x O 2)} .

Nb: TiO ₂ (formula _{Ti 1 - x Nb x O 2} ) an oxide prepared by the substitution amount (x) of Nb to the x = 0, 0.01, 0.02, 0.03, 0.06, 0.1, 0.15, 0.2 in the material film ( The internal transmittance of 12) (transmittance in the original sense should be regarded as a deficiency, so that the transmittance which becomes 100% when subtracting the amount of reflection in the oxide material film 12 is referred to as internal transmittance hereinafter). When measured, as shown in FIG. 9, in a visible light region (wavelength 400-800 nm), it turns out that a favorable result is obtained by 80% or more. In particular, the sample whose Nb substitution amount x <0.06 is shown that 95% or more of internal transmittance | permeability can be implement | achieved in visible region. Because it might cause the internal transmittance decreases as the higher the degree of substitution of Nb, hayeotgi increase in the amount of Ti ^{+ 3} with Nb substitution amount, and the transition probabilities between _2g t -e _g band having an absorption edge in the visible light region increases I think. In addition, this Nb: TiO ₂ is made on a strontium titanate (SrTiO ₃ ) substrate whose surface is finished to be a (100) plane, but Ti _{1 -xy} Co _x Nb _y O ₂ is equivalent on other substrates such as a GaN substrate. It is thought to exhibit physical properties (resistance, etc.).

However, in the case of application to an actual device, the thickness of the oxide material film 12 is often set to 100 nm or more. Particularly, the specifications required for the current ITO are 80 to 100 nm or more in internal transmittance. It is more than%. In order to satisfy this specification, an internal transmittance of 95% or more is required for a film thickness of 50 nm. As shown in Fig. 9, the above specification can be satisfied by suppressing the Nb substitution amount to x? 0.06, so that it is also possible to produce a transparent conductor thin film that exceeds the internal transmittance of the conventional ITO thin film.

10 shows the temperature dependence of the resistivity of the oxide material film 12 produced by the substitution amount of Nb described above. As shown in Fig. 10, the oxide material film 12 having a substitution amount x of Nb of 0.01? X? 0.2 has good conductivity at room temperature of about 10 ^-4 cm &lt; cm &gt; at room temperature as compared with the case where Nb is not substituted. It can be seen that the characteristic is obtained. In addition, this Nb: TiO _{2 is} also made on a strontium titanate (SrTiO ₃ ) substrate having a surface of (100) plane, but Ti _{1 -xy} Co _x Nb _y O ₂ is formed on another substrate such as a GaN substrate. It is thought to exhibit equivalent basic physical properties (resistance, etc.).

Not only does the substitution amount x of Nb in the oxide material film 12 be 0.01? X? 0.2, but the resistivity of 10 ⁻⁴ Ωcm band is achieved by setting the substitution amount x of Nb to 0.001? X? It is possible to obtain.

In the case where the substitution amount x of Nb in the oxide material film 12 is set to 0.01? X? 0.06, the internal transmittance is set to 95% to 98% (film thickness of 100 nm) at a film thickness of 50 nm. Even if it is 80% or more), it will become possible to improve.

In the case where the substitution amount x of Nb in the oxide material film 12 is set to 0.02 ≦ x ≦ 0.06, the internal resistivity is further improved while the resistivity is 5 × at room temperature (280K to 300K). It becomes possible to lower it to about 10 ^-4 ohm ^- cm, and to 1 * 10 <^-4> ohm ^- cm at cryogenic temperature (5K-20K).

That is, the anatase (TiO _2), the result obtained Nb replaced the Ti site by Nb of: by the TiO ₂ with an oxide material film 12, in addition to improve the opacity also low resistivity comparable to ITO (10 ^{- 4} Ωcm conductivity) can be obtained.

In addition, the resistivity of the oxide material film 12 is 2 x 10 ^-4 to 5 x 10 ^-4 Ωcm at room temperature, or Nb so as to be 8 x 10 ^-5 to 2 x 10 ^-4 Ωcm at cryogenic temperatures. By substituting, it is possible to dramatically expand the applicability to various devices including display panels.

In addition, the oxide material film 12 can be made large in size and mass-produced by utilizing the film forming technology of TiO ₂ which has already been utilized as a photocatalyst. By applying the low-resistance oxide material film 12 to the display panel, it is possible to reduce the power consumption of these display elements, and to further promote the enlargement and the miniaturization of the display panel. In addition, the oxide material film 12 can significantly reduce the labor associated with manufacturing in addition to being able to reduce the costs associated with facilitating the procurement of raw materials and simplifying the manufacturing process. Become.

In other words, by applying the oxide material film 12 to which the present invention is applied as an electrode, a transparent electrode having conventional performance can be produced at a lower cost, and thus the application range can be widened. As the oxide material film 12, when M: Ti0 ₂ which is less corrosive to acids or alkalis is used, the application range can be expanded without being influenced by the surrounding environment.

In addition, the transparent metal 1 to which this invention is applied is not limited to the use as an electrode, Of course, you may apply to parts, a thin film, a device, etc. which are transparent and require high conductivity as another use.

Next, the magneto-optical characteristics of Ti _{1 -x- y} Co _x Nb _y O ₂ produced by the above-described method will be described.

Fig. 11 is a diagram showing the applied magnetic field dependence of the Faraday rotation coefficient at room temperature of Ti _{1 -x- y} Co _x Nb _y O ₂ (thickness of film: 50 nm). The horizontal axis represents the applied magnetic field, and the vertical axis represents the Faraday rotation coefficient. In addition, the _{Ti 1 -x- y Co x Nb y} O 2 is _{(La x Sr 1 -x) (} Al x Ta 1 -x) O 3 (LSAT) substrate: but written over (board thickness 0.5 mm), GaN It is thought that Ti _{1 -x- y} Co _x Nb _y O ₂ will exhibit equivalent properties even on other substrates such as a substrate.

For the 5% and Nb 20% ball added (共添加) a TiO ₂ thin film of Co, the case of 5% and Nb 10% ball a TiO ₂ thin film was added to Co, and the TiO ₂ thin film was added to 5% Co In the case, the value satisfies 0.1 × 10 ⁴ degrees / cm or more, which is sufficiently at the practical level.

The Faraday rotation coefficient was shown in the vicinity of 400 nm without a magnetic field. In the case of the TiO ₂ thin film co-added with 5% Co and 10% Nb, the Faraday rotation coefficient showed a value of about 0.45 × 10 ⁴ degrees / cm. Even when compared to the Nb-free thin film, it can be seen that in the case of the TiO ₂ thin film co-added with 5% of Co and 10% of Nb, the Faraday rotation coefficient near 400 nm is improved by about 2 times.

Fig. 12 is a graph showing the wavelength dependence of the Faraday rotation coefficient at room temperature of Ti _{1 -x- y} Co _x Nb _y O ₂ (thickness of film: 50 nm). The horizontal axis represents wavelength, and the vertical axis represents Faraday rotation coefficient. The Ti _{1 -x- y} Co _x Nb _y O _{2 is} also made on the LSAT substrate (substrate thickness: 0.5 mm), but the Ti _{1 -x- y} Co _x Nb _y O ₂ is formed on another substrate such as a GaN substrate. It is thought to represent equivalent characteristics.

For the 5% and Nb 20% ball a TiO ₂ thin film was added to Co, in the case of the case of the 5% and 10% ball a TiO ₂ thin film was added Nb to Co, and a TiO ₂ thin film was added to 5% Co, The Faraday rotation coefficient which satisfy | fills the value of 0.1x10 <^4> / cm or more which is fully practical level in 600 nm or less was shown. In addition, in the case of the TiO ₂ thin film co-added with 5% of Co and 10% of Nb, it can be seen that the Faraday rotation coefficient is particularly improved at 600 nm or less.

Fig. 13 shows the external transmittance at room temperature of a TiO ₂ thin film co-added with Co 5% and Nb 10%. The horizontal axis represents wavelength and the vertical axis represents transmittance.

According to this, it turns out that the thin film can permeate | transmit the light of wavelength 260 nm or more. In addition, it is understood that 70% or more transmittance can be obtained with light of 350 nm or more, and 80% or more transmittance can be obtained with light of 500 nm or more. That is, it turns out that this thin film can ensure the transmittance | permeability about 70 to 80% in visible range.

As mentioned above, according to the oxide material shown in this embodiment, the magneto-optical material useful in the short wavelength region can be obtained.

Moreover, it is also possible to control the magnitude | size of a Faraday rotation angle by changing the addition amount of Nb.

Also, x in the _{Ti 1 -x- y Co x Nb y} O 2 , it is preferred that 0 <x. It is because there exists a problem that ferromagneticity does not express when it is zero. In order to obtain larger spontaneous volatilization, x is more preferably 0.03 ≦ x.

Y of the _{Ti 1 -x- y Co x Nb y} O 2 , it is preferable that 0.1 ≤ y ≤ 0.2. In the case of 0.1, there is a problem that the Faraday rotation coefficient may be small, and in the case of larger than 0.2, there is a problem that the Faraday rotation coefficient may be small again.

Y of the _{Ti 1 -x- y Co x Nb y} O 2 (x = 0.05) , it is preferable that 0 <y ≤ 0.2. When Nb is not included, there exists a problem that a Faraday rotation coefficient is small compared with the addition of Nb, and when it is larger than 0.2, there exists a problem that a Faraday rotation coefficient may become small again. In order to obtain a large Faraday rotation coefficient, it is more preferable that y be a value of 0.1 ≦ y ≦ 0.2.

Next, on the i-GaN substrate or above the p-GaN substrate, Ti _{1 -} describes the various physical properties in the case of forming a film _x Nb _x O _2.

FIG. 14A is a diagram showing the composition dependence of resistivity in the case where a TiO ₂ film is formed on the i-GaN substrate while the Nb doping amount is changed on the p-GaN substrate. The oxygen partial pressure when the TiO ₂ film was formed was 1 × 10 ⁻⁶ Torr even in any substrate.

From these drawings, from the viewpoint of decreasing the resistivity, in any substrate, the amount of Nb dope is 1% or more and 15% or less, preferably the amount of Nb dope is 3% or more and 15% or less, and more preferably the amount of Nb dope is 6 It is understood that it is good to set the amount of Nb dope to 6% or more and 10% or less, more preferably 15% or less.

Fig. 15A is a resistivity when a TiO ₂ film is formed on an i-GaN substrate and Fig. 15B is a p-GaN substrate with a Nb doping amount of 6% while varying the substrate temperature during film formation. It is a figure which shows the substrate temperature dependency of the. The oxygen partial pressure when the TiO ₂ film was formed was 1 × 10 ⁻⁷ Torr even with any substrate. In addition, the temperature at the time of resistance measurement was 300K.

From these drawings, from the viewpoint of reducing the resistivity, the substrate temperature at the time of film formation is 350 ° C or more and 500 ° C or less, preferably the substrate temperature is 400 ° C or more and 500 ° C or less, and more preferably the substrate temperature is 450 ° C in any case. It can understand that it is good to set it as above 500 degreeC.

In the case where the oxygen partial pressure is set to 1 × 10 ⁻⁶ Torr and 1 × 10 ⁻⁷ Torr under the conditions of the substrate temperature of 350 ° C. or more and 500 ° C. or less, the oxygen partial pressure is 1 × 10 ⁻⁷ even when the substrate is any substrate. In the case of using Torr, the resistivity was lower. Moreover, the sheet resistance when the TiO ₂ film which made the substrate temperature 450 degreeC, oxygen partial pressure 1 * ^10-7 Torr, and made N% dope amount 6% on the i-GaN substrate was 234 ohms / square.

Fig. 16A shows the wavelength dependence of transmittance when a TiO ₂ film having an Nb doping amount of 6% is formed on an i-GaN substrate and Fig. 16B on a p-GaN substrate. The oxygen partial pressure in the case of forming a TiO ₂ film was 1 × 10 ⁻⁶ Torr even in any substrate.

From these figures, it is understood that the transmittance hardly depends on the film formation temperature and the type of substrate, and that the transmittance of 90% or more can be ensured over a wide wavelength.

FIG. 17A shows the substrate temperature dependence of the transmittance and the oxygen partial pressure in the case where a TiO ₂ film having an Nb doping amount of 6% is formed on the i-GaN substrate and FIG. 17B shows a p-GaN substrate. It is a figure which shows dependency. The oxygen partial pressure when the TiO ₂ film was formed was 1 × 10 ⁻⁶ Torr or 1 × 10 ⁻⁷ Torr in any substrate.

From these figures, in the case of any substrate, when the oxygen partial pressure is 1 × 10 ^-6 Torr, the transmittance is ensured to 93% or more, and when the oxygen partial pressure is 1 × 10 ^-7 Torr, the transmittance is 75% to 80%. You can see what you can do.

Next, the measurement by film-forming temperature gradient film is demonstrated.

The film formation temperature gradient film is formed by applying a temperature gradient to one substrate. For example, it is possible to simultaneously realize that the film is formed on the substrate at a low temperature at one end of the substrate while the film is formed on the substrate at a high temperature at the other end of the substrate. At this time, the film-forming temperature gradient film was used to investigate the optimum film-forming temperature in detail.

18 is a diagram showing various measurement results using the film formation temperature gradient film.

Fig. 18A is a diagram showing the relationship between the substrate position and the temperature distribution. As shown in Fig. 18A, the film formation temperature is changed along the longitudinal direction of the substrate. Thereby, the position and the film-forming temperature of the longitudinal direction of a board | substrate correspond one to one.

Fig. 18B is a diagram showing the relationship between the substrate position and the diffraction intensity distribution by X-ray diffraction (XRD). The mapping measurement of this XRD has shown the relationship between the board | substrate position and the relationship of 2 (theta). According to Figs. 18A and 18B, the position where the diffraction intensity is high is about 450 deg. That is, it turns out that the film formation temperature is about 450 degreeC with the best crystallinity.

Fig. 18C is a diagram showing the relationship between the substrate position and the distribution of resistance values. According to Figs. 18A and 18C, the minimum value of resistance is when the substrate temperature is 450 deg. In particular, when the film is formed at 450 ° C. compared with 500 ° C., there is a possibility that the resistance value can be reduced by 25%. In addition, the resistance measurement by the 2-terminal method was performed at the time of this measurement.

Next, a SnO ₂ film formed by the PLD method will be described.

Fig. 19 shows the results of X-ray diffraction (XRD) measurement of a SnO ₂ film formed by a PLD method on a p-GaN substrate. According to this XRD spectrum, it can be confirmed that SnO ₂ is stably generated on the p-GaN substrate.

Fig. 20 is a diagram showing an electron beam diffraction image (RHEED pattern) of a SnO ₂ film formed by a PLD method on a p-GaN substrate. A clear streak pattern is observed on the SnO ₂ surface, and it can be seen that it is epitaxially growing. In addition, the host is a good crystallinity leak from the SnO ₂ film pattern on RHEED it can be seen that is obtained.

The oxygen partial pressure at the time when SnO ₂ film is formed is 1 × 10 ^-5 Torr, the film thickness is 50 nm, the resistivity was 5 × 10 ^-2 Ωcm ^- and ^1.

In addition, SnO ₂ is not only doped with all, but M: SnO ₂ (M is P, As, Sb, S, Se, Te, Al, Ga, In, Co, Fe, Cr, Mn, V, and Ni). Any one or a combination thereof). If M to be doped is P, As, Sb, S, Se, Te, Al, Ga, In, an improvement in electrical conductivity can be expected while maintaining transparency. On the other hand, when M doped is Co, Fe, Cr, Mn, V, Ni, magneto-optical effects can be expected.

In the near future, the wavelength of light expected to be used in optical communication is expected to shift to shorter wavelengths such as blue and ultraviolet light. In such a situation, this oxide material can be used also as a magneto-optical device which shows a large Faraday rotation coefficient in the vicinity of wavelength 400nm. In particular, obtaining a large Faraday rotation coefficient like a magnetic garnet film currently in use indicates that the production of an optical isolator suitable for the next generation of short-wavelength communication is possible according to this oxide material.

The use of the oxide material shown in this embodiment is not limited to use as an optical isolator, magneto-optical devices such as optical circulators, variable optical attenuators, optical communication devices, magneto-optical devices, optical circuits, and emergency devices. It can also be used for semi-optical components, non-reflective optical elements, semiconductor lasers equipped with isolators, current magnetic field sensors, magnetic domain observation, magneto-optical measurements, and the like.

Examples of the optical isolator include a module in which an LD and an isolator are integrated, an optical isolator for fiber insertion, an optical isolator for an optical amplifier, a deflection dependent optical isolator, a deflection independent optical isolator, and a waveguide optical isolator. As the waveguide optical isolator, for example, one using a Mach-zhender type branch waveguide or one using a rib waveguide is used.

The optical circulator may be a deflection dependent light circulator or a deflection independent circulator.

When TiO ₂ doped with Co or the like is applied to a light emitting device composed of a GaN compound semiconductor, an optical isolator corresponding to a short wavelength band such as blue or ultraviolet light can be realized. When realized by addition, epitaxial growth of the optical isolator on the TiO ₂ layer, TiO ₂ film not only functions as a buffer for the crystal growth, it is possible to obtain a monolithic (monolithic) functional device. That is, not only a high-efficiency light emitting device, a low-cost, large-area display, but also a monolithic functional device can be developed, for example, a fusion of a transparent electrode and an optical device and a fusion of a light emitting device and a magneto-optical device can be realized. . Moreover, you may use the oxide material shown by this embodiment for a light receiving element, high frequency devices, such as a HEMT (High Electron Mobility Transistor), and an electronic device.

For the above matters, a SnO ₂ film doped with Al, Sb or the like may be used.

So far, oxide materials such as various TiO ₂ films and various SnO ₂ films have been described, but these may be rutile type or anatase type. From the viewpoint of lowering the resistivity, the anatase type is preferable, and the rutile type is preferable from the viewpoint of ease of preparation. In addition, these may be amorphous.

The present invention has been described above with reference to specific embodiments. However, it will be apparent to those skilled in the art that modifications or substitutions of the above embodiments can be made without departing from the spirit of the invention. That is, this invention has been disclosed by the form of illustration, and description of this specification should not be interpreted limitedly. In order to judge the summary of this invention, the column of the claim as described in this application should be taken into consideration.

Moreover, although it is clear that embodiment for description of this invention achieves the objective mentioned above, it is also understood that many changes and other Examples can be performed by a person skilled in the art. You may employ | adopt the element or component of each embodiment for a claim, specification, drawing, and description with another or a combination. The scope of a claim is intended to include such a change and other embodiment in the range, and these are included in the technical thought and technical scope of this invention.

It is applicable to various functional elements by forming a metal oxide having excellent characteristics.

Claims (22)

Al _x Ga _y In _z N (where 0 ≤ x ≤ 1, 0 ≤ y ≤ 1, 0 ≤ z ≤ 1), It is formed on the said Al _x Ga _y In _z N, and has an oxide material which consists of a metal oxide, The metal oxide is TiO ₂ , characterized in that the functional device. The functional element according to claim 1, wherein one or two or more selected from the group consisting of Nb, Ta, Mo, As, Sb, Al, and W are doped into the metal oxide. The functional element according to claim 1 or 2, wherein one or two or more selected from the group consisting of Co, Fe, Cr, Sn, Ni, Mn and V is doped into the metal oxide. . The functional element according to claim 1, wherein the oxide material is a single phase film. The functional element according to claim 1, wherein the oxide material is an epitaxial film. The functional element according to claim 1 or 2, which is a transparent electrode. The functional element according to claim 1, which is a light emitting element. The functional element according to claim 1, which is a high frequency device. The functional element according to claim 3, which functions as a magneto-optical device. The functional element according to claim 3, which functions as an isolator. On the Al _x Ga _y In _z N (where 0 ≤ x ≤ 1, 0 ≤ y ≤ 1, 0 ≤ z ≤ 1), an oxide material made of a metal oxide is formed by a pulse laser deposition method, And the metal oxide is TiO ₂ . 12. The method of claim 11 wherein the metal oxide is doped with Ta, The substrate temperature at the time of deposition is 320 degreeC or more and 550 degrees C or less, The oxide material formation method characterized by the above-mentioned. 12. The method of claim 11 wherein the metal oxide is doped with Ta, The substrate temperature at the time of deposition is 320 to 450 degreeC, The oxide material formation method characterized by the above-mentioned. 12. The method of claim 11 wherein the metal oxide is doped with Ta, The substrate temperature at the time of deposition is 320 to 400 degreeC, The oxide material formation method characterized by the above-mentioned. 12. The method of forming an oxide material according to claim 11, further comprising a step of performing a treatment of bringing out the Ga end to the substrate surface before deposition. The method of forming an oxide material according to claim 11, further comprising a step of performing an acid treatment on the surface of the substrate before deposition. The method of claim 11, wherein the metal oxide is doped with Nb, The substrate temperature at the time of deposition is made into 350 degreeC or more and 500 degrees C or less, The oxide material formation method characterized by the above-mentioned. Al _x Ga _y In _z N (where 0 ≤ x ≤ 1, 0 ≤ y ≤ 1, 0 ≤ z ≤ 1), It is formed on the said Al _x Ga _y In _z N, and has an oxide material which consists of a metal oxide, And the metal oxide is Ti _{1 -α} Nb _α O ₂ , wherein 0.01 ≦ α ≦ 0.15. Al _x Ga _y In _z N (where 0 ≤ x ≤ 1, 0 ≤ y ≤ 1, 0 ≤ z ≤ 1), It is formed on the said Al _x Ga _y In _z N, and has an oxide material which consists of a metal oxide, The metal oxide is SnO ₂ , characterized in that the functional device. 20. The functional element according to claim 19, wherein one or two or more selected from the group consisting of P, As, Sb, S, Se, Te, Al, Ga, and In is doped into the metal oxide. . The functional element according to claim 19, wherein one or two or more selected from the group consisting of Co, Fe, Cr, Mn, V, and Ni are doped into the metal oxide. On the Al _x Ga _y In _z N (where 0 ≤ x ≤ 1, 0 ≤ y ≤ 1, 0 ≤ z ≤ 1), an oxide material made of a metal oxide is formed by a pulse laser deposition method, And the metal oxide is SnO ₂ .

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