JP5229919B2 - Photoelectric conversion element and photodetection element using oxide transparent conductive film - Google Patents

Description

  The present invention relates to an oxide transparent conductive film having high transparency in the visible region and near infrared region, a photoelectric conversion element using the same, and a light detection element.

  As the oxide transparent conductive film, an indium oxide thin film to which tin is added, a tin oxide thin film to which fluorine or antimony is added, a zinc oxide thin film to which boron, aluminum, or gallium is added are widely used. In particular, a tin-added indium oxide thin film is widely used because a low-resistance thin film excellent in transparency in the visible region can be easily obtained. Oxide transparent conductive films are used as electrode materials for not only flat panel displays but also photoelectric conversion elements and various light receiving elements because of their high transmittance in the visible region and conductivity.

  The photoelectric conversion element is a laminate of p-type and n-type semiconductors. As the photoelectric conversion element using the oxide transparent conductive film, a heterojunction solar cell in which a silicon-based thin film is laminated on single crystal or polycrystalline silicon. Examples thereof include silicon-based thin-film solar cells such as amorphous, microcrystalline, and polycrystalline, and chalcopyrite-based thin-film solar cells.

  Conventionally, as a transparent electrode of a heterojunction solar cell, tin-added indium oxide, and as a transparent electrode of a silicon-based thin film solar cell, fluorine-added tin oxide, boron or aluminum or gallium-added zinc oxide or tin-added indium oxide, chalcone As a transparent electrode of a pyrite thin film solar cell, zinc oxide or tin-added indium oxide added with aluminum or gallium is used (for example, see Patent Document 1).

  However, reflection / absorption loss due to free carriers of the transparent electrode cannot be ignored due to the high quality of the photoelectric conversion layer of the solar cell, the development of a stacked thin film solar cell having a wide spectral sensitivity, and the development of optical confinement technology. It has become like this. Mainly, silicon-based and chalcopyrite-based photoelectric conversion layers are sensitive to light in the range of 400 nm to 1200 nm. Therefore, in order to reduce the absorption loss in the transparent electrode, the transparent electrode needs to have a high transmittance in the range of 400 nm to 1200 nm.

  Next, a photodetecting element having wavelengths in the visible and near infrared regions will be described. Wavelengths used in optical fiber communication are in the near infrared region, and 1.3 micron band and 1.55 micron band near infrared sources are mainly used, and at the same time, a light detection element for detecting light of these wavelengths Is required. In general, a light detection element has a structure in which a light detection material layer is sandwiched between a pair of electrodes. The light detection material layer is made of germanium, indium gallium arsenide based semiconductor, or an alkaline earth metal element sulfide. And those using selenide. A light-transmitting electrode is used for the light incident side electrode of the light detection element, and tin-added indium oxide is used (for example, see Patent Documents 2 to 4). For this reason, the transparent electrode used in the high-sensitivity light detection element is required to have a low resistance and a high transmittance with respect to light in the wavelength range of 400 nm to 1600 nm, which is detection light.

However, a commonly used tin-doped indium oxide thin film or gallium-doped zinc oxide thin film has a low resistivity of 2 × 10 ⁻⁴ Ωcm, but has a large carrier concentration of about 1 × 10 ²¹ cm ⁻³ and a mobility of 30 cm ² / Vs. Therefore, for example, as shown in Non-Patent Document 1, near-infrared rays of 1000 nm or more absorb or reflect and have low transmittance.

  It is possible to reduce oxygen vacancies and improve near-infrared transmittance by increasing the amount of oxygen introduced during the formation of tin-added indium oxide. However, this method increases neutral impurities, resulting in a decrease in mobility and an increase in resistivity.

  Patent Documents 5 to 11 show that the introduction of water vapor when forming tin-added indium oxide at a temperature of room temperature to 200 ° C. or lower can prevent crystallization of the transparent conductive film during film formation. It has been shown that a transparent conductive film excellent in workability as compared with a crystalline transparent conductive film can be obtained. Here, good workability means that when a tin-added indium oxide thin film formed on a substrate is patterned by etching, the tin-added indium oxide thin film depends on the etching rate of the crystalline and amorphous parts. This means that there is no problem of a tin-added indium oxide film residue on the substrate to be removed. This excellent workability is a technique necessary for forming a transparent electrode pattern used for a liquid crystal display unit, for example.

  In addition, the amorphous tin-added indium oxide film produced in this way has higher resistance and lower transmittance than the crystalline tin-added indium oxide film directly produced on the heating substrate, and is inferior in characteristics as a transparent electrode. However, Patent Documents 9 and 11 report that by annealing an amorphous tin-added indium oxide film, characteristics equivalent to those of a conventional tin-added indium oxide transparent electrode can be obtained. However, the optical characteristics of the conventional tin-doped indium oxide film have a high absorption coefficient in the near-infrared wavelength range of 800 nm to 1600 nm because of the high carrier concentration as described above.

  Also, in Examples of Patent Documents 5 to 11, transparency and resistivity in the visible region are shown, but transparency in the near-infrared wavelength range from 800 nm to 1600 nm or a carrier indicating that the transparency can be realized. There is no information on the concentration, and there is no report that a thin film having excellent transparency in the near infrared region has been produced.

  On the other hand, an indium oxide material containing molybdenum (for example, see Non-Patent Document 2), an indium oxide material containing titanium (for example, see Non-Patent Document 3), and an indium oxide material containing tungsten (for example, Non-Patent Document 4). It is reported that an indium oxide material containing zirconium (see, for example, Non-Patent Document 5) has a lower absorption coefficient in the near-infrared wavelength range of 800 nm to 1600 nm than that of tin-added indium oxide. In either case, information on carrier concentration and mobility that can produce or predict an oxide transparent electrode with low resistance and high near-infrared transmittance is described. However, in all cases, the film forming temperature is as high as 350 ° C. or higher. Therefore, there remains a problem in the development and manufacturing method of a transparent conductive material capable of manufacturing a transparent conductive film having high transmittance and low resistivity mainly in a wide wavelength region from 400 nm to 1600 nm by a low temperature process of 350 ° C. or less.

Japanese Patent No. 3133449 Japanese Patent No. 2624410 JP-A-11-214737 JP 2001-127336 A Japanese Laid-Open Patent Publication No. 2-54755 Hei 2-112112 Japanese Laid-Open Patent Publication No. 2-163363 Hei 2-251990 Hei 3-64450 Japanese Patent Laid-Open No. 9-50712 Japanese Patent Laid-Open No. 2003-16858 H. Fujiwara and M.F. Kondo, Phys. Rev. B 71, 075109 (2005). Y. Meng, X.M. Yang, H .; Chen, J.A. Shen, Y .; Jiang, Z. Zhang, and Z.M. Hua, Thin Solid Films 394, 219 (2001). M.M. F. A. van Hest, M.M. S. Dabney, J .; D. Perkins, D.D. S. Ginley, and M.M. P. Taylor, Appl. Phys. Lett. 87, 031111 (2005). P. F. Newhouse, C.I. -H. Park, D.D. A. Keszler, J.A. Tate, and P.M. S. Nyholm, Appl. Phys. Lett. 87, 112108 (2005). T.A. Koida and M.K. Kondo, J .; Appl. Phys. 101, 063705 (2007). M.M. Chen, Z. L. Pei, X. Wang, Y.W. H. Liu, C.I. Sun, and L.L. S. Wen, J.M. Phys. D: Appl. Phys. 33, 2538 (2000). Swanson et al. Natl. Bur. Stand. (US), Circ. 539, 5 (1955), 26. (JCPDS: 06-0416)

  A tin-added indium oxide thin film, a zinc oxide thin film to which boron or aluminum or gallium is added, and a tin oxide thin film to which fluorine is generally used as a transparent conductive film generally have low resistance and high transmittance in the visible light region. However, for example, as reported in Non-Patent Document 1, the transmittance in the near infrared region is low.

  The transparent conductive film is used as a window electrode of a photoelectric conversion element. However, the absorption and reflection caused by free carriers from the visible region to the near infrared region of the transparent electrode due to the development of high-quality photoelectric conversion layers, the development of laminated thin-film solar cells with wide spectral sensitivity, and the development of optical confinement technology Loss cannot be ignored. Mainly, silicon-based and chalcopyrite-based photoelectric conversion layers are sensitive to light in the range of 400 nm to 1200 nm. Therefore, in order to reduce the absorption loss in the transparent electrode, the transparent electrode needs to have a high transmittance in the range of 400 nm to 1200 nm. Further, in order to reduce the reflection loss due to the difference in refractive index between the transparent electrode and the photoelectric conversion layer adjacent thereto, the transparent electrode needs to have a high refractive index in the range of 400 nm to 1200 nm. However, as reported in Non-Patent Document 1, for example, the refractive index in the near-infrared region of the transparent conductive film decreases with an increase in wavelength, and is significantly lower than about 3.5 for silicon. Considering the amplitude condition for antireflection, it is desirable that the refractive index in the near infrared region of the transparent conductive film is 1.5 or more.

  Moreover, the said transparent conductive film is used as a window electrode of a near-infrared photodetector. As the wavelength used in optical fiber communication, a near-infrared source of 1.3 micron band or 1.55 micron band is mainly used. Therefore, the window electrode of the photodetecting element for detecting light of these wavelengths is required to have high transparency with little free carrier absorption in the range of 1300 nm to 1600 nm.

There is a close relationship between optical characteristics and electrical characteristics in the near infrared region of the transparent conductive film. When electrons moving in the transparent conductive film are scattered by defects or the like, light is absorbed by free carriers. The wavelength at which free carrier absorption occurs is defined by the plasma frequency and is a function of the carrier concentration. In order to make the wavelength 1600 nm or more, the carrier concentration needs to be 5 × 10 ²⁰ cm ⁻³ or less.

In addition, the absorption coefficient due to free carriers decreases as the mobility increases and the carrier concentration decreases. On the other hand, the resistivity of the transparent conductive film is expressed as a function of carrier concentration and mobility. Therefore, in order to reduce free carrier absorption without increasing the resistivity, and to improve the transmittance in the near infrared region and the reflectance, it is necessary to reduce the carrier concentration and improve the mobility. Here, when the carrier concentration is 5 × 10 ²⁰ cm ⁻³ , the mobility is 40 cm ² / Vs or more in order to obtain high transmittance and low reflectance in the near infrared region without increasing the resistivity. It is desirable. Further, when the transparent conductive film is used for the window electrode of the photoelectric conversion element or the light detection element, the resistivity of the transparent conductive film is 1 × 10 ⁻³ Ωcm or less, preferably 5 × 10 ⁻⁴ Ωcm, in order not to increase the series resistance of the element. The following is desirable.

In general, the mobility of a thin film having a carrier concentration of 1 × 10 ¹⁹ cm ⁻³ or more is mainly dominated by ionized impurities rather than grain boundaries and lattice vibrations. Therefore, the mobility depends on the amount of impurities added as a dopant and its valence. Determined by However, the mobility of a transparent conductive film generally produced by a low-temperature process is significantly smaller than the mobility dominated by ionized impurity scattering by the above-mentioned dopant, as shown in Non-Patent Document 5, for example. For example, in the case of tin-added indium oxide, in addition to tin ions as additives, ionization such as point defects such as oxygen vacancies, interstitial oxygen, interstitial indium, and indium vacancies, or complex defects involving them It is thought that many impurities and neutral impurities are contained and these contribute to carrier scattering.

  Indium oxide thin films containing molybdenum, titanium, tungsten or zirconium are higher than tin-doped indium oxide thin films, zinc oxide thin films doped with boron, aluminum or gallium, or tin oxide thin films doped with fluorine without impairing conductivity. Although properties excellent in mobility and transparency in the near-infrared region have been reported, there is a problem that the film forming temperature is as high as 350 ° C. or higher.

In view of the above problems, the present invention uses a low-temperature process of 200 ° C. or lower to suppress scattering caused by impurities other than dopants for a thin film having a carrier concentration in a specific range. An object of the present invention is to provide an oxide transparent conductive film having a wavelength of 400 nm to 1600 nm and excellent transparency in the visible and near-infrared region, which is close to mobility controlled only by impurity scattering by the dopant shown.
Another object of the present invention is to provide a photoelectric conversion element and a light detection element using the oxide transparent conductive film as a main part.
In addition, the present invention uses the oxide transparent conductive film as a main part for a transparent electrode of a photoelectric conversion element, so that a high-efficiency solar cell having high spectral sensitivity in the near-infrared region, which has been impossible in the past, or weak An object is to realize a high-performance photodetector that can detect near infrared rays.

In order to solve the above problems, the present invention employs the following problem solving means.
1. The oxide transparent conductive film contains hydrogen atoms, and the hydrogen atom content is 1% or more and 10% or less.
2. The amorphous oxide conductive film containing hydrogen atoms has an electron mobility measured by Hall effect measurement of 40 cm ² / Vs or more, a carrier concentration of 5 × 10 ²⁰ cm ⁻³ or less, and a specific resistance of 1 × 10 ⁻³ Ωcm or less. To do.
3. The amorphous oxide conductive film containing hydrogen atoms has a refractive index of a wavelength of 400 nm to 1200 nm of 1.5 or more and a specific resistance of 5 × 10 ⁻⁴ Ωcm or less.
4). The amorphous oxide transparent conductive film containing hydrogen atoms may be any one of indium oxide, gallium oxide, zinc oxide, magnesium oxide, tin oxide, germanium oxide, titanium dioxide film, or two or more of these. A thin film containing a compound is used.
5. The crystalline oxide conductive film containing hydrogen atoms makes the crystal orientation non-oriented.
6). The crystalline oxide conductive film containing a hydrogen atom has a lattice constant of 0.3% or less with respect to an unstrained bulk lattice constant.
7). In the crystalline oxide conductive film containing hydrogen atoms, the crystallite size obtained from the diffraction peak width by x-ray diffraction measurement is set to 1/5 or more of the film thickness.
8). The crystalline oxide conductive film containing hydrogen atoms has an electron mobility of 70 cm ² / Vs or higher, a carrier concentration of 5 × 10 ²⁰ cm ⁻³ or lower, and a specific resistance of 1 × 10 ⁻³ Ωcm or lower. .
9. The crystalline oxide conductive film containing hydrogen atoms has a refractive index of a wavelength of 400 nm to 1200 nm of 1.5 or more and a specific resistance of 5 × 10 ⁻⁴ Ωcm or less.
10. The crystalline oxide transparent conductive film containing a hydrogen atom is any one of indium oxide, gallium oxide, zinc oxide, magnesium oxide, tin oxide, germanium oxide, titanium dioxide film, or two or more of these compounds A thin film containing
11. The crystalline oxide transparent conductive film containing hydrogen atoms is formed by annealing an amorphous oxide transparent conductive film containing hydrogen atoms.
12 A photoelectric conversion element is formed using the oxide transparent conductive film having excellent transparency in the near infrared region as well as the visible region as an electrode. The photoelectric conversion element here is a heterojunction solar cell in which a silicon-based thin film is laminated on bulk single crystal silicon, a silicon-based thin film solar cell, a chalcopyrite-based thin film solar cell, a solar cell using a compound semiconductor such as GaAs, CdTe, Or the organic solar cell using an organic material etc. are included, However, It is not limited to these.
13. A photodetecting element is constituted by using, as an electrode, the oxide transparent conductive film that is excellent not only in the visible region but also in the near infrared region. The photodetecting element here has a pair of electrodes and a photodetecting material layer sandwiched between the electrodes, and the oxide transparent conductive film is used for at least one of the electrodes. Note that the light detection element can be used for near infrared detection by providing a light detection material layer as a near infrared detection material layer.
14 A photoelectric conversion element or a light detection element using the oxide transparent conductive film as an electrode is formed by annealing the element.

The problem solving means of the present invention is specifically as follows.
(1) The oxide transparent conductive film is characterized in that the hydrogen atom content of the oxide conductive film containing hydrogen atoms is set to an arbitrary value within a range of 1% to 10%.
(2) In the amorphous oxide transparent conductive film, the oxide conductive film according to (1) is an amorphous oxide conductive film containing hydrogen atoms, and the hydrogen atom content is 1% or more and 10%. The electron mobility by Hall effect measurement is 40 cm ² / Vs or more, the carrier concentration is 5 × 10 ²⁰ cm ⁻³ or less, and the specific resistance is 1 × 10 ⁻³ Ωcm or less.
(3) The amorphous oxide transparent conductive film is an amorphous oxide conductive film containing hydrogen atoms as the oxide conductive film described in (1) above, and has an arbitrary wavelength within a wavelength range of 400 nm to 1200 nm. The refractive index is 1.5 or more and the specific resistance is an arbitrary value of 5 × 10 ⁻⁴ Ωcm or less.
(4) In the crystalline oxide transparent conductive film, the oxide conductive film according to (1) is a crystalline oxide conductive film containing hydrogen atoms, and the hydrogen atom content is in the range of 1% to 10%. The lattice constant is 0.3% or less with respect to the lattice constant of the unstrained bulk.
(5) The crystalline oxide transparent conductive film is obtained by using the oxide conductive film described in (1) above as a crystalline oxide conductive film containing hydrogen atoms, and the crystallite size obtained from the diffraction peak width by x-ray diffraction measurement Is set to 1/5 or more of the film thickness.
(6) In the crystalline oxide transparent conductive film, the oxide conductive film described in (1) above is a crystalline oxide conductive film containing hydrogen atoms, and the electron mobility by Hall effect measurement is 70 cm ² / Vs or more. The carrier concentration is 5 × 10 ²⁰ cm ⁻³ or less, and the specific resistance is 1 × 10 ⁻³ Ωcm or less.
(7) The crystalline oxide transparent conductive film uses the oxide conductive film described in (1) above as a crystalline oxide conductive film containing hydrogen atoms, and has a refractive index in the wavelength range of 400 nm to 1200 nm of 1.5. The specific resistance is 5 × 10 ⁻⁴ Ωcm or less.
(8) The crystalline oxide transparent conductive film is a non-oxide-containing conductive film according to any one of (4) to (7) above, which contains a hydrogen atom as described in (2) or (3) above. A crystalline oxide transparent conductive film is formed by annealing.
(9) The oxide transparent conductive film is the oxide transparent conductive film according to any one of (1) to (8) above, wherein indium oxide, gallium oxide, zinc oxide, magnesium oxide, tin oxide, germanium oxide, Any one of the titanium dioxide films, or a thin film containing two or more of these compounds may be used.
(10) An oxide transparent conductive film is characterized in that the oxide transparent conductive film according to any one of (1) to (8) is a thin film containing elements of indium and oxygen.
(11) The photoelectric conversion element is characterized in that the transparent oxide conductive film according to any one of (1) to (10) above is used as a transparent electrode.
(12) The photoelectric conversion element includes a first electrode layer, a conductive oxide layer, an n-type thin film semiconductor layer, an i-type thin film semiconductor layer, a p-type thin film semiconductor layer, and a second electrode arranged in order from the substrate side. A photoelectric conversion element having a layer and generating a photovoltaic force by light incident from the second electrode layer side, wherein the second electrode layer or the conductive oxide layer is the above (1) to (10 The oxide conductive film according to any one of the above items.
(13) The photoelectric conversion element is formed on the light incident side by a heterojunction in which a reverse conductivity type thin film semiconductor layer or an i type thin film semiconductor layer and a reverse conductivity type thin film semiconductor layer are formed on a single conductivity type crystalline semiconductor. A photoelectric conversion element in which a transparent electrode is formed, wherein the oxide transparent conductive film according to any one of (1) to (10) is used as a transparent electrode.
(14) The photoelectric conversion element includes a first electrode layer, a p-type semiconductor layer, an n-type semiconductor layer, and a second electrode layer in order from the substrate side, and enters from the first or second electrode layer side. A photoelectric conversion element that generates photovoltaic power by light, wherein the first or second electrode layer is the oxide transparent conductive film according to any one of (1) to (10) above. And
(15) In the light detection element having a pair of electrodes and a light detection material layer sandwiched between the electrodes, at least one of the pair of electrodes may be the light detection element according to (1) to (10). The oxide transparent conductive film according to any one of the above items is used.

The amorphous or crystalline oxide conductive film using hydrogen atoms as the dopant of the present invention is superior in transparency in the visible region and near infrared region as compared with the conventional tin-added indium oxide (ITO) thin film. . Further, since the thin film can be produced by a low temperature process at room temperature or 200 ° C. or less, it can be said that the invention is extremely useful in industry.
The inventor of the present invention selects indium oxide as an example of the substrate material of the oxide conductive film, changes the hydrogen atom content as a dopant, and anneals the amorphous indium oxide thin film formed on the glass substrate and the thin film. The structure, optical properties, and electrical properties of the crystalline indium oxide thin films grown by solid phase were investigated. In order to investigate the superiority of optical properties and electrical properties over tin-added indium oxide (ITO), which is a conventional material, it was compared with an indium oxide (ITO) thin film containing 10% by weight of tin oxide formed at the same process temperature.

As a result, on an unheated substrate, crystallization is hindered as the hydrogen atom content increases, and an amorphous film can be obtained within a range that can be understood by general x-ray diffraction measurement. The resistivity of the thin film is reduced from 1 × 10 ⁻² Ωcm or more to 1 × 10 ⁻³ Ωcm or less by increasing the hydrogen atom content from 1 to 10% from the non-addition, and the ITO produced on the non-heated substrate Resistivity equivalent to or lower than that of a thin film can be realized. An indium oxide thin film having a hydrogen atom content of 1 to 10% is superior to the ITO thin film in the visible region, and has an average light transmission at an arbitrary wavelength within a wavelength range of 500 nm to 1600 nm at a film thickness of about 240 nm. A rate of 70% or more can be realized.

  On the other hand, when these thin films were annealed in a vacuum atmosphere at 200 ° C., the thin films that were amorphous by the addition of hydrogen atoms before annealing were polycrystallized by solid phase growth and were determined from the x-ray diffraction peak width. The crystallite size is larger than that of an indium oxide thin film or ITO thin film to which hydrogen atoms are not intentionally added, and a crystallite size of 50 nm or more can be realized. Further, the indium oxide thin film having a hydrogen atom content of 1 to 10% has a resistivity equivalent to that of the ITO thin film, but the mobility is 3 times or more and the carrier concentration can be suppressed to 1/3 or less. Free carrier absorption in the near infrared region can be suppressed, and as a result, an average light transmittance of 70% or more at an arbitrary wavelength within a wavelength range of 400 nm to 2000 nm can be realized at a film thickness of about 240 nm.

Indium oxide or other oxide conductive films are generally n-type degenerate semiconductors, and electrons serving as carriers contribute to electrical conduction. The electrons that are carriers reflect and absorb light having a wavelength longer than that. The wavelength of the light depends on the carrier concentration, but generally exists in the near infrared region. For example, the tin-added indium oxide thin film or zinc oxide thin film, which has been generally used in the past, has a carrier concentration of about 1 × 10 ²¹ cm ⁻³ and a resistivity of about 2 × 10 ⁻⁴ Ωcm, which is very low. The permeability is poor because of its high absorption coefficient.

The carrier concentration is preferably 5 × 10 ²⁰ cm ⁻³ or less in order not to impair the transmittance in the near infrared region with a wavelength of 1600 nm or less without reducing the film thickness.
Since the indium oxide thin film using hydrogen atoms as the dopant of the present invention can have a carrier concentration as low as 5 × 10 ²⁰ cm ⁻³ or less depending on the production conditions, it has high transparency to near infrared rays having a wavelength of 1600 nm or less.

In addition, the indium oxide thin film using hydrogen atoms as the dopant of the present invention has a carrier concentration lower than that of a conventional indium oxide-based or zinc oxide-based oxide conductive material, but the carrier mobility is amorphous produced by non-heating. in quality thin film 40 cm ² / Vs or more, 50 cm ² / Vs or more, depending on production conditions, the thin film is a crystalline thin film annealed and a 70cm ² / Vs or more, 90cm ² / Vs or more, depending on manufacturing conditions, or 130 cm ² / Vs The above thin film can also be realized, and the specific resistance is about the same because the mobility of the conventional transparent conductive film is extremely large compared to the mobility of a tin-added indium oxide film or a gallium-added zinc oxide thin film (about 20 to 30 cm ² / Vs). Can be realized. As a result, the near-infrared transmittance can be increased without impairing conductivity.

Also, the carrier scattering mechanism in the carrier concentration range of about 1 × 10 ¹⁹ cm ^{−3 to} 5 × 10 ²⁰ cm ⁻³ is due to point defects such as ionized impurity scattering or neutral impurity scattering rather than scattering due to macro defects such as grain boundaries and dislocations. Scattering dominates. In the present invention, the mobility value relative to the carrier concentration suggests that ionized impurities that are monovalently charged by hydrogen atoms are formed and carriers are generated. From this, it is expected that one carrier is generated per one hydrogen atom by forming a hydrogen atom at or near the oxygen O site. Therefore, the present invention can be applied not only to indium oxide but also to gallium oxide, zinc oxide, magnesium oxide, tin oxide, germanium oxide, titanium dioxide thin film alone, or a thin film containing two or more of these compounds. it can.

Moreover, the photoelectric conversion element or photodetection element of the present invention using an amorphous or crystalline oxide transparent conductive film added with hydrogen atoms as an electrode is a tin-added indium oxide (ITO) which is a conventional transparent conductive film material. Compared with a photoelectric conversion element or a light detection element using a thin film as an electrode, the sensitivity characteristics in the visible region and the near infrared region are excellent. Therefore, it can be said that the invention is extremely useful in industry.
As an example of the photoelectric conversion element, the inventor of the present invention produces a photoelectric conversion element having a heterojunction formed of crystalline silicon and amorphous silicon using an indium oxide thin film to which hydrogen atoms are added, and with respect to the annealing temperature. The current-voltage characteristics and spectral sensitivity characteristics of the device were investigated. Further, the current-voltage characteristics and spectral sensitivity characteristics were compared with a photoelectric conversion element having the same structure using tin-doped indium oxide (ITO) as a window electrode.

  As a result, regardless of the presence or absence of annealing treatment, the element using hydrogenated indium oxide as the window electrode has improved spectral sensitivity characteristics from the visible region to the near infrared region compared with the device using ITO as the window electrode. The current density increases. Therefore, conversion efficiency can be remarkably improved.

  Further, in a photoelectric conversion element using hydrogen atom-added indium oxide as a window electrode, the element is annealed at 140 ° C. or more, and the hydrogen atom-added indium oxide thin film is solid-phase crystallized before annealing or at 140 ° C. The spectral sensitivity characteristics from the visible region to the near-infrared region are improved and the current density can be remarkably increased as compared with a device that is annealed at a lower temperature.

  As described above, the hydrogen atom-added indium oxide thin film has a carrier concentration lower than that of the conventional ITO thin film, but since the carrier mobility is large, the specific resistance can be approximately the same. Further, since the carrier concentration is low and the mobility is large, the hydrogen atom-added indium oxide thin film has a high refractive index and a low absorption coefficient from the visible region to the near infrared region, as compared with the ITO thin film. Therefore, when this thin film is used as a window electrode of a photoelectric conversion element, it is possible to reduce reflection loss and absorption loss in the transparent conductive film due to a difference in refractive index between the transparent conductive film and the photoelectric conversion layer. As a result, the spectral sensitivity characteristics can be improved without deteriorating the electrical characteristics of the photoelectric conversion element. In addition, since the present invention reduces the optical loss due to the window electrode and improves the device sensitivity from the visible region to the near infrared region, it has a heterojunction formed of crystalline silicon and amorphous silicon. The present invention can be applied not only to a photoelectric conversion element but also to a photoelectric conversion element / photodetection element having element sensitivity from the visible region to the near infrared region.

It is a diagram showing data x-ray diffraction pattern and the bulk of the indium oxide powder of the indium oxide thin films at room temperature film formation in different H _{2 O} partial pressure (P _{H2 O)} under on the glass substrate shown in Embodiment 1 of the present invention. X-ray diffraction pattern and bulk of indium oxide thin film formed at room temperature under different H ₂ O partial pressure (P _H2O ) on glass substrate shown in Example 1 of the present invention after vacuum annealing at 200 ° C. It is a figure which shows the data of an indium oxide powder. Is a diagram showing the electric characteristics at room temperature after vacuum annealing at a film and after the temperature of the indium oxide thin films at room temperature film formation in different H _{2 O} partial pressure on the glass substrate shown in Embodiment 1 of the present invention. A thin film before annealing produced on the glass substrate shown in Example 1 of the present invention in a range where the H ₂ O partial pressure is 5 × 10 ⁻⁵ Pa or more and 1 × 10 ⁻³ Pa or less, the thin film is 200 ° C. or 240 ° C. It is a figure which shows the electrical property of the thin film after annealing at 200 degreeC, the ITO thin film before annealing produced as a comparative sample, and the ITO thin film which annealed the thin film at 200 degreeC. The indium oxide thin film formed at room temperature under different H ₂ O partial pressures (P _H2O ) on the glass substrate shown in Example 1 of the present invention, the ITO thin film formed at room temperature as a comparative sample, and the glass substrate transmission at room temperature It is a figure which shows a reflection spectrum. After vacuum annealing the indium oxide thin film formed at room temperature under different H ₂ O partial pressure (P _H2O ) and the ITO thin film formed at room temperature as a comparative sample on a glass substrate shown in Example 1 of the present invention at 200 ° C. It is a figure which shows the transmission and reflection spectrum in room temperature of a thin film and a glass substrate of Is a diagram showing the hydrogen atoms H _{2 O} content partial pressure and the film shown in Table 11 of the present invention. It is a figure which shows the element structure of the photoelectric conversion element shown in Example 2 of this invention. It is a figure which shows the current-voltage characteristic of the photoelectric conversion element after annealing at 150 degreeC shown in Example 2 of this invention. It is a figure which shows the spectral sensitivity characteristic of the photoelectric conversion element after annealing at 150 degreeC shown in Example 2 of this invention. It is a figure which shows the element structure of the photoelectric conversion element shown in the Example of this invention. It is a figure which shows the element structure of the photoelectric conversion element shown in the Example of this invention. It is a figure which shows the element structure of the photoelectric conversion element shown in the Example of this invention. It is a figure which shows the element structure of the photon detection element shown in the Example of this invention.

Explanation of symbols

1, 22, 32, 44 Metal electrode 2 n-type silicon 3 i-type amorphous silicon 4 p-type amorphous silicon 5, 23 transparent conductive films 6, 11, 19, 37 comb-shaped electrode 13 n-type silicon thin film 14, 16 i-type silicon Thin film 15 Silicon substrate 17 P-type silicon thin film 21 Substrate 24 n-type microcrystalline silicon 25 i-type microcrystalline silicon 26 p-type microcrystalline silicon 12, 18, 27, 36, 42 Oxide conductive film 31 to which hydrogen atoms are added 41 Glass substrate 33 CuInSe ₂
34 Cadmium sulfide 35 Zinc oxide 43 Europium and samarium-added calcium sulfide

  Embodiments of the present invention will be described below in detail with reference to the drawings.

An embodiment in which hydrogen atom-added indium oxide thin films having different hydrogen atom contents are produced on a glass substrate by RF magnetron sputtering as an example of a transparent conductive film containing hydrogen atoms as the dopant of the present invention will be described. Indium oxide was used as a raw material target. The substrate temperature was room temperature, a mixed atmosphere of Ar, O ₂ and H ₂ O (total pressure of about 0.5 Pa, Ar partial pressure of 4.98 × 10 ⁻¹ Pa, O ₂ partial pressure of 1.9 × 10 ⁻⁴ Pa, H _2. O partial pressure less than 5 × 10 ⁻⁶ , 1 × 10 ⁻⁵ , 5 × 10 ⁻⁵ , 1 × 10 ⁻⁴ , 5 × 10 ⁻⁴ , 1 × 10 ⁻³ , 5 × 10 ⁻³ , 1 × 10 ^{− 2} Pa). The back pressure of the used RF magnetron sputtering apparatus is less than 5 × 10 ⁻⁶ Pa. After forming the thin film, annealing was performed in vacuum at 100 ° C., 150 ° C., 200 ° C., and 240 ° C. for 2 hours. The film thickness is about 240 nm. The content of hydrogen, indium, and oxygen atoms in some thin films was determined using hydrogen forward scattering analysis and Rutherford backscattering analysis. In addition, the hydrogen atom content of some thin films was determined by an ascending / desorbing gas analysis method. Here, quantification of hydrogen atoms was performed by using a sample whose hydrogen atom amount was determined by hydrogen forward scattering analysis as a standard sample. Determination of the amorphous and crystalline properties of the thin film and the crystallite size and lattice constant of the crystalline thin film were determined using the x-ray diffraction method. Optical properties were evaluated by measuring transmission / reflection spectra using a spectrophotometer. The electrical characteristics were evaluated using the Hall measurement method at room temperature, and the resistivity, carrier concentration, and hole mobility were determined.

Different _{H 2} O partial pressure in the glass substrate which is an embodiment of the present invention in FIG. 1 _{(P H2O) (in} this case, as the sample _{H 2} O partial pressure, less than ^{5 × 10 -6, 1 × 10} -5, 5 ^{X10 −5} , 1 × 10 ⁻⁴ , 5 × 10 ⁻⁴ , 1 × 10 ⁻³ , 5 × 10 ⁻³ , and 1 × 10 ⁻² Pa) The previous x-ray diffraction pattern and the bulk indium oxide powder data shown in Non-Patent Document 7 (the vertical axis in FIG. 1 is XRD intensity (x-ray diffraction intensity), and the horizontal axis is 2θ (x-ray diffraction angle) ( 2), FIG. 2 shows the x-ray diffraction pattern after the vacuum annealing of the indium oxide thin film used in FIG. 1 at 200 ° C. and the data of the bulk indium oxide powder shown in Non-Patent Document 7 (FIG. 2). The vertical axis of XRD is the XRD intensity (x-ray diffraction intensity), and the horizontal axis is 2θ (x-ray rotation (Fold angle) (°)). From FIG. 1, the thin film prepared at a H ₂ O partial pressure of 1 × 10 ⁻⁵ Pa or less is a (111) preferentially oriented polycrystalline thin film, whereas the H ₂ O partial pressure is 5 × 10 5. ^The thin film prepared in the range of ⁻⁵ Pa to 5 × 10 ⁻³ Pa is amorphous, and the thin film having a H ₂ O partial pressure of 1 × 10 ⁻² Pa is amorphous with a slight (222) diffraction peak. It can be seen that a polycrystalline thin film having a dominant quality was obtained. When these thin films are annealed in a vacuum, all thin films are crystallized as shown in FIG. 2 at 200 ° C. or higher. It can be seen that a thin film is formed. Here, the definition of non-orientation is that the diffraction intensity ratio of the thin film is similar even if it does not completely match the diffraction peak intensity ratio of the bulk indium oxide powder. In fact, the diffraction peak intensity ratios of the thin films prepared in the range where the H ₂ O partial pressure shown in FIG. 2 is in the range of 5 × 10 ⁻⁵ Pa to 5 × 10 ⁻³ Pa are similar but different from each other. It is also slightly different from the bulk value.

Table 1 shows changes in the annealing temperature of the crystallite size in the hydrogen atom-added indium oxide thin film for each sample H ₂ O partial pressure value.
Table 1 shows the crystallite size in the <222> direction calculated from the half-width of the (222) diffraction peak of the x-ray diffraction pattern, and Table 2 shows the (111) preferentially oriented polycrystalline thin film based on the (444) diffraction peak angle. The calculated lattice constant and the non-oriented polycrystalline thin film are shown in Table 2 in Table 3, which are calculated from (222), (332), (431), (440), and (622) diffraction peak angles. Ratio of difference of lattice constant to lattice constant (1.0118 nm) of bulk indium oxide powder [(lattice constant of hydrogen atom-added indium oxide thin film−lattice constant of bulk indium oxide powder) / lattice constant of bulk indium oxide × 100].

From Table 1, the thin film produced when the H ₂ O partial pressure is 1 × 10 ⁻⁵ Pa or less or 1 × 10 ⁻² Pa or more hardly changes the crystallite size by annealing, whereas the H ₂ O partial pressure is It can be seen that the thin film produced in the range of 5 × 10 ⁻⁵ Pa or more and 5 × 10 ⁻³ Pa or less significantly increases the crystallite size to 50 nm or more by annealing and is as large as 1/5 or more of the film thickness. This size is significantly larger than the crystallite size (16.3 nm and 20.4 nm, respectively) of indium oxide having the same film thickness produced on a heated substrate at 200 ° C. or 450 ° C. Further, as shown in Table 1, it can be seen from the change in crystallite size that the degree of crystallization relative to the annealing temperature differs depending on the H ₂ O partial pressure produced.

Table 2 shows the annealing temperature change of the lattice constant in the hydrogen atom-added indium oxide thin film for each sample H ₂ O partial pressure value.
Table 3 shows the annealing temperature change of the lattice constant difference in the hydrogen atom-added indium oxide thin film for each sample H ₂ O partial pressure value.
From Table 2 or Table 3, it can be seen that the lattice constant of a thin film manufactured at an H ₂ O partial pressure of 1 × 10 ⁻⁵ Pa or less is larger than that of bulk indium oxide and stress is applied. On the other hand, the lattice constant of the thin film produced in the range where the H ₂ O partial pressure is 5 × 10 ⁻⁵ Pa or more and 1 × 10 ⁻² Pa or less is close to the value of bulk indium oxide, and the lattice constant difference is 0.3%. It turns out that it is the following.

FIG. 3 and Table 4-8 show the electrical characteristics at room temperature of each thin film after annealing at room temperature and after annealing at room temperature. In FIG. 3, the vertical axis represents resistivity (Ωcm), carrier concentration (cm ⁻³ ), and mobility (cm ² / Vs) in the order of the upper, middle, and lower stages, and the horizontal axis represents the H ₂ O partial pressure (Pa). is there.
In FIG. 3, □ indicates the characteristic value before annealing, ◇ that is crushed from above and below indicates the characteristic value at the annealing temperature of 100 ° C., and ◇ that is crushed from the left and right indicates the characteristic value at the annealing temperature of 150 ° C. The symbol “特性” represents a characteristic value at an annealing temperature of 200 ° C., and the symbol “◯” represents a characteristic value at an annealing temperature of 240 ° C.
Table 4 shows a hydrogen atom-added indium oxide thin film for each sample partial pressure value before annealing after room temperature deposition and an ITO thin film before annealing after room temperature deposition as a comparative sample (In ₂ O ₃ thin film containing 10% by weight of SnO ₂ ). It is a table | surface which shows the resistivity, carrier concentration, and mobility in room temperature.
Table 5 shows the resistivity, carrier concentration and mobility at room temperature of the hydrogen atom-added indium oxide thin film for each sample partial pressure value after annealing at 100 ° C. in vacuum after room temperature film formation.

Table 6 shows the resistivity, carrier concentration, and mobility of the hydrogen atom-added indium oxide thin film for each sample partial pressure value after annealing at 150 ° C. in vacuum after film formation at room temperature.
Table 7 shows a hydrogen atom-added indium oxide thin film for each sample partial pressure value after annealing at room temperature in vacuum after film formation at room temperature and an ITO thin film after annealing at room temperature in vacuum after film formation at room temperature as a comparative sample. It is a table | surface which shows the resistivity, carrier concentration, and mobility in room temperature.
Table 8 shows the resistivity, carrier concentration, and mobility at room temperature of each of the above thin films after annealing at 240 ° C. in vacuum after film formation at room temperature.

As shown in FIG. 3 and Table 4, in the sample before annealing after room temperature film formation, the carrier concentration increases by increasing the H ₂ O partial pressure from less than 5 × 10 ⁻⁶ Pa to 1 × 10 ⁻⁴ Pa. It can be seen that carriers are generated by the addition of hydrogen atoms. At the same time, the mobility increases, and the thin film before annealing produced in the range where the H ₂ O partial pressure is greater than 1 × 10 ⁻⁵ Pa and less than or equal to 5 × 10 ⁻³ Pa is greater than 40 cm ² / Vs. It can be seen that it is significantly larger than 20.4 cm ² / Vs of the ITO thin film before annealing produced as a sample. Therefore, a thin film before annealing produced in a range where the H ₂ O partial pressure is larger than 1 × 10 ⁻⁵ Pa and smaller than 5 × 10 ⁻³ Pa is a thin film having a lower resistance than that of ITO, although the carrier concentration is lower than that of ITO. Can be realized.

On the other hand, regarding the thin film after annealing, the resistivity of the thin film produced in the range where the H ₂ O partial pressure is greater than 1 × 10 ⁻⁵ Pa and smaller than 5 × 10 ⁻³ Pa is the ITO thin film after annealing of the comparative sample. It can be seen from Table 7 that it is almost the same. When changes in carrier concentration and mobility due to annealing are examined, as shown in FIG. 3 or Table 4-8, the carrier concentration increases from about 3 × 10 ²⁰ to about 1.5 × 10 ²⁰ cm ⁻³ as the annealing temperature increases. The value of the ITO thin film of the comparative sample is significantly smaller than the value of 9.47 × 10 ²⁰ cm ⁻³ , the mobility is remarkably improved from about 55 to about 100 to about 140, and the value of the ITO thin film is 28.5 cm ^2. It can be seen that the resistivity is significantly larger than / Vs, and the resistivity equivalent to that of the ITO thin film can be realized by the effects of both.

FIG. 4 is a log-log graph showing the carrier concentration (cm ⁻³ ) variation characteristics of the hole mobility (cm ² / Vs) for each resistivity based on the data in Tables 4, 7, and 8.
In FIG.
○ represents the characteristics of the thin film of the present invention after annealing,
● represents the characteristics of the thin film of the present invention before annealing,
□ indicates the characteristics of the conventional ITO thin film after annealing,
■ mark represents the characteristics of the conventional ITO thin film before annealing,
A represents resistivity 1 × 10 ⁻⁴ Ωcm characteristic,
B represents resistivity 2 × 10 ⁻⁴ Ωcm characteristics,
C represents a resistivity 1 × 10 ⁻³ Ωcm characteristic.
FIG. 4 shows the characteristic value of the thin film before annealing of the present invention produced in the above-mentioned H ₂ O partial pressure in the range of 5 × 10 ⁻⁵ Pa to 1 × 10 ⁻³ Pa by “●”. The characteristic value of the thin film of the present invention after annealing the thin film at 200 ° C. or 240 ° C. is indicated by “◯”, and the characteristic value of the conventional ITO thin film before annealing prepared as a comparative sample is indicated by “■”. The characteristic value of the conventional thin film annealed at 200 ° C. is indicated by “□”, and the electrical characteristics are plotted in the horizontal axis carrier concentration (cm ⁻³ ) and vertical axis hole mobility (cm ² / Vs). Is. The resistivity can be expressed as a function of the carrier concentration and the hole mobility. The resistivity is a characteristic of 1 × 10 ⁻³ Ωcm (“C” characteristic line in FIG. 4), and the characteristic is 2 × 10 ⁻⁴ Ωcm. (“B” characteristic line in FIG. 4) A line having a characteristic of 1 × 10 ⁻⁴ Ωcm (“A” characteristic line in FIG. 4) is also shown.

The A characteristic line, the B characteristic line, and the C characteristic line have the same slope, which is about −10 ¹⁹ cm ² / Vs / (cm ⁻³ ).
In both before and after annealing, the resistivity of the indium oxide thin film to which hydrogen atoms are added as the dopant of the present invention is not much different from that of the conventional ITO thin film, but the carrier concentration is remarkably decreased and the mobility is remarkably increased. The effects of the present invention are clearly exceptional.

5 and Table 9 transmission and reflection spectra and transmittance (see Table 9 (a)) and reflectance (see Table 9 (b)) for each H ₂ O partial pressure of the glass substrate and the sample prepared at room temperature. FIG. 6 and Table 10 show the transmission / reflection spectrum and transmittance (see Table 10 (a)) / reflectance (Table 10 (b) after annealing the glass substrate and the sample prepared at room temperature at 200 ° C. in vacuum. ))). 5 and 6, the vertical axis represents transmittance (%) and reflectance (%), and the horizontal axis represents wavelength (nm).
5 and 6,
The dotted line indicates the characteristics of the glass substrate, the solid line indicates the characteristics of the ITO of the comparative example,
○ mark represents a characteristic of H ₂ O partial pressure of 5 × 10 ⁻⁶ Pa or less,
● represents the characteristic that the H ₂ O partial pressure is 1 × 10 ⁻⁵ Pa.
The □ mark represents the characteristic that the H ₂ O partial pressure is 5 × 10 ⁻⁵ Pa.
The mark ■ represents the characteristic that the H ₂ O partial pressure is 1 × 10 ⁻⁴ Pa.
The Δ mark represents the characteristic that the H ₂ O partial pressure value is 5 × 10 ⁻⁴ Pa,
The ▲ mark indicates the characteristic of H ₂ O partial pressure of 1 × 10 ⁻³ Pa,
The mark ◇ represents the characteristic of H ₂ O partial pressure of 5 × 10 ⁻³ Pa,
The asterisk represents the characteristic that the H ₂ O partial pressure is 1 × 10 ⁻² Pa.
Tables 9 and 10 show the transmittance (see Table 9 (a)) and the reflectance (see Table 9 (b)) at room temperature of the glass substrate and each thin film shown in the examples of the present invention and 200 ° C. in vacuum. It is the table | surface which shows the transmittance | permeability (refer Table 10 (a)) and reflectivity (refer Table 10 (b)) after annealing.

The glass substrate has almost no absorption in the wavelength range from 400 nm to 2600 nm. In a hydrogen atom-added thin film prepared at room temperature, in particular, in a thin film prepared in a range where the H ₂ O partial pressure is larger than 1 × 10 ⁻⁵ Pa and smaller than 5 × 10 ⁻³ Pa, the transmittance is at a wavelength of 1600 nm or more. It can be seen that the reflectance is increased at a wavelength of 1800 nm or more. This can be explained by absorption by free carriers and plasma reflection corresponding to the carrier concentration values shown in FIG. On the other hand, in the wavelength range of 500 nm or more and 1600 nm or less, interference vibration due to the refractive index difference between the thin film surface and the thin film and the glass substrate is seen as shown in FIG. Since the value of the valley portion of the interference vibration of the reflection spectrum matches that of the substrate, it can be understood that the reflection spectrum is almost transparent.

On the other hand, a thin film annealed at 200 ° C. in vacuum is a thin film prepared and annealed in a range where the H ₂ O partial pressure is larger than 1 × 10 ⁻⁵ Pa and smaller than 5 × 10 ⁻³ Pa. It can be seen that although the rate has decreased, no significant increase in reflectivity has been observed. This corresponds to the decrease in the carrier concentration value shown in FIG. 3 or Table 7 compared to the value before annealing, and the wavelength at which absorption by free carriers and plasma reflection are observed changes to the longer wavelength side. I can explain that. On the other hand, in the wavelength range of 400 nm to 1600 nm, interference vibration due to the refractive index difference between the thin film surface and the thin film and the glass substrate is seen as shown in FIG. In addition, since the value of the valley portion of the interference vibration in the reflection spectrum matches that of the substrate, it can be seen that it is almost transparent.

Table 11 shows a thin film prepared with an H ₂ O partial pressure of 1 × 10 ⁻⁴ Pa, less than 5.0 × 10 ⁻⁶ Pa, 1 × 10 ⁻⁴ Pa, and 5 × 10 ⁻³ Pa among the samples. The contents of indium, oxygen, and hydrogen atoms obtained from Rutherford backscattering analysis and hydrogen forward scattering analysis of a thin film prepared by annealing at 200 ° C. in vacuum, and temperature-programmed desorption gas analysis using the sample as a reference sample A thin film before annealing and a thin film annealed at 200 ° C. in a vacuum in which the H ₂ O partial pressure estimated by the method is in the range of less than 5.0 × 10 ⁻⁶ Pa to 1.0 × 10 ⁻² Pa. The hydrogen atom content of is shown. FIG. 7 is a graph showing the relationship between the hydrogen atom content and the H ₂ O partial pressure in Table 11.
In FIG. 7, ◯ indicates the characteristics before annealing, and ● indicates the characteristics after annealing.
From Table 11, it can be seen that as the H ₂ O partial pressure increases, the hydrogen atom content increases and the In / O ratio increases. Further, FIG. 7 shows that the amount of hydrogen atoms in the thin film can be controlled by the H ₂ O partial pressure at the time of forming the thin film.

  One of the factors that increase the mobility of hydrogen-added thin films compared to tin-added thin films is to suppress the generation of point defects that act as ionized impurities or neutral impurities other than dopant hydrogen atoms. It is possible. Since thin film growth is generally produced by a non-equilibrium process, it is difficult for all atoms to be located at the correct site of the crystal as compared to a bulk produced in a state close to an equilibrium state. Therefore, point defects such as interstitial tin due to oxygen vacancies, indium vacancies, interstitial oxygen, interstitial indium, or added impurities, or composite defects via them tend to occur inside the thin film.

In general, the carrier scattering mechanism in the carrier concentration range of about 1 × 10 ¹⁹ cm ⁻³ or more and about 5 × 10 ²⁰ cm ⁻³ or less includes ionized impurity scattering or neutral impurity scattering rather than scattering due to macro defects such as grain boundaries and dislocations. It is thought that scattering due to defects dominates. FIG. 3 and Table 7 or Table 8 show that the H ₂ O partial pressure is 1.0 × 10 ⁻⁴ Pa or more and 5.0 × 10 ⁻⁴ Pa or less and is annealed to the carrier concentration of the thin film. The mobility value is very similar to the mobility value governed by ionized impurity scattering, which is expected when all carriers reported in non-reference 6 etc. are generated by monovalently charged ionized impurities. close.

This is due to the fact that one carrier is generated per hydrogen atom due to the formation at or near the oxygen O site, and the amorphous layer is solid-phase grown by annealing. It can be considered that the density of micro defects such as point defects is reduced at the same time as macro defects such as grain boundaries as compared with the thin film formed. Therefore, the present invention is applied not only to indium oxide but also to an oxide thin film containing gallium oxide, zinc oxide, magnesium oxide, tin oxide, germanium oxide, titanium dioxide thin film alone, or two or more of these compounds. be able to. As described above, the doping mechanism of this thin film is not necessarily clear, but since it is considered that hydrogen atoms are related to oxygen sites, this thin film is also applied to thin films with other elements added to the cation sites. Can be applied.
In ₂ containing ZrO ₂ in _In 2 _{O 3} thin film (thickness: about 70 nm) and Table 13 including the SnO ₂ of Table 12 is _{H 2} O partial pressure was made at room temperature at 1 × ¹⁰ -4 Pa as an example The electrical characteristics of an O ₃ thin film (film thickness of about 70 nm) are shown. Table 12 (a) shows the electrical characteristics of the In ₂ O ₃ thin film containing SnO ₂ before annealing, and Table 12 (b) shows the electrical characteristics after annealing at 200 ° C. Table 13 (a) shows the electrical characteristics of the In ₂ O ₃ thin film containing ZrO ₂ before annealing, and Table 13 (b) shows the electrical characteristics after annealing at 200 ° C. Each thin film has an electron mobility of 40 cm ² / Vs or more before annealing, a carrier concentration of 5 × 10 ²⁰ cm ⁻³ or less, a specific resistance of 1 × 10 ⁻³ Ωcm or less, and an electron mobility of 70 cm ² / Vs or more after annealing. It can be seen that the carrier concentration is 5 × 10 ²⁰ cm ³ or less and the specific resistance is 1 × 10 ⁻³ Ωcm or less.

  In the present invention, a crystalline oxide is formed by annealing for 2 hours in a vacuum. However, since the annealing is to promote crystallization by solid phase growth, annealing is performed in a short time. Processing is also possible. As an example, similar results were obtained for a sample that was annealed in vacuum for 1 hour. Further, since the annealing treatment is for promoting crystallization by solid phase growth, it is not limited to a vacuum state, and can be applied to other non-oxidizing and oxidizing atmospheres.

In the present invention, the sputtering method is used as a film forming method. However, as described above, the increase in mobility is caused by the addition of a hydrogen atom as a dopant. The same non-equilibrium process can also be applied to a general thin film growth method (evaporation method, ion plating method, molecular beam epitaxy method, metal organic vapor phase epitaxy method, pulsed laser deposition method, etc.).
In this example, glass was used as a transparent substrate to produce an oxide conductive film to which hydrogen atoms, which are the dopants of the present invention, were added. However, even if the manufacturing temperature is room temperature or a low temperature of 200 ° C. or lower, the effect is brought about. Therefore, it can be applied to other transparent substrates and plastics.
As an example, Table 14 shows an In ₂ O ₃ thin film (thickness: about 70 nm) prepared on a film substrate at room temperature with a H ₂ O partial pressure of 1 × 10 ⁻⁴ Pa before annealing and at 150 ° C. and 170 ° C. The electrical characteristics after annealing at 200 ° C. are shown. Table 14 (a) shows the electrical characteristics of the thin film produced on the polyethylene naphthalate (PEN) film, and Table 14 (b) shows the electrical characteristics of the thin film produced on the polyimide (PI) film. In any thin film, electron mobility before annealing is 40 cm ² / Vs or more, carrier concentration is 5 × 10 ²⁰ cm ⁻³ or less, specific resistance is 1 × 10 ⁻³ Ωcm or less, and electron mobility is 170 ° C. or more in the annealed thin film. It can be seen that it is 70 cm ² / Vs or more, the carrier concentration is 5 × 10 ²⁰ cm ³ or less, and the specific resistance is 1 × 10 ⁻³ Ωcm or less.

An embodiment in which a photoelectric conversion element having a heterojunction formed of crystalline silicon and amorphous silicon is manufactured as an example of a photoelectric conversion element using the oxide conductive film added with hydrogen atoms of the present invention as a transparent electrode will be described. .
FIG. 8 is a schematic cross-sectional view showing the configuration of the photoelectric conversion element according to the embodiment of the present invention. As shown in FIG. 8, on the lower surface of the n-type single crystal silicon substrate (2) having a thickness of about 525 μm and a (111) plane, aluminum (1) having a thickness of about 100 nm produced by vacuum deposition is formed. Is formed. On the upper surface of the n-type single crystal silicon substrate (2), substantially intrinsic i-type amorphous silicon (3) having a thickness of about 4 nm produced by plasma CVD is formed. On the i-type amorphous silicon (3), p-type amorphous silicon (4) having a thickness of about 3 nm and formed by plasma CVD is formed. On the p-type amorphous silicon (4), an indium oxide thin film containing hydrogen atoms is formed as a transparent conductive film (5) having a thickness of about 70 nm. This hydrogenated indium oxide thin film is produced at a H ₂ O partial pressure of 1.0 × 10 ⁻⁴ Pa using the sputtering method described in Example 1. A comb-shaped electrode (6) made of silver (Ag) produced by a vacuum deposition method is formed on the transparent conductive film (5). The effective area of the photoelectric conversion element excluding the comb-shaped electrode portion is 0.21 cm ² , and this area was used for calculation of the short-circuit current density and the conversion efficiency of the photoelectric conversion element. Further, a photoelectric conversion element using an ITO thin film (In ₂ O ₃ thin film containing 10% by weight of SnO ₂ ) formed by using the sputtering method described in Example 1 as a transparent conductive film (5) is a comparative sample (conventional product). ). In addition, all the transparent conductive films (5) were produced without heating, and after the photoelectric conversion element was produced, annealing treatment was performed at 100, 120, 140, 150, 160, 180, and 200 ° C. in vacuum. Table 15 shows the result of comparing the current-voltage characteristics of these photoelectric conversion elements. Table 15 (a) shows the characteristics of a photoelectric conversion element using hydrogen atom-added indium oxide as a transparent electrode, and Table 15 (b) shows the characteristics of a comparative example: photoelectric conversion element using ITO as a transparent electrode. FIG. 9 shows current-voltage characteristics of the photoelectric conversion element after annealing at 150 ° C. In FIG. 9, the characteristic of the present invention is shown as characteristic a, and the characteristic of the conventional example is shown as characteristic b. In FIG. 9, the horizontal axis represents the voltage of the photoelectric conversion element, and the vertical axis represents the current density.
Table 16 shows the result of comparing the spectral sensitivity characteristics of these photoelectric conversion elements. Table 16 (a) shows the quantum efficiency characteristics of a photoelectric conversion element using hydrogen atom-added indium oxide as a transparent electrode, and Table 16 (b) shows a comparative example: quantum efficiency characteristics of a photoelectric conversion element using ITO as a transparent electrode. Indicates.
FIG. 10 shows the spectral sensitivity characteristics of the photoelectric conversion element after annealing at 150 ° C. In FIG. 10, the characteristic of the present invention is shown as characteristic a, and the characteristic of the conventional example is shown as characteristic b. In FIG. 10, the horizontal axis indicates the wavelength of incident light, and the vertical axis indicates the quantum efficiency.

  As is clear from Table 15 and FIG. 9, in the case of the product of the present invention using hydrogenated indium oxide as the transparent conductive film (5), the current density is greatly improved as compared with the conventional product using ITO. As a result, it has been found that the conversion efficiency is greatly improved. When the spectral sensitivity characteristics were examined, as shown in Table 16 and FIG. 10, it was found that the spectral sensitivity characteristics of the product of the present invention were superior to those of the conventional products in the visible region and near infrared region.

The improvement in the photoelectric conversion element performance of the product of the present invention can be explained as the effect of reducing the reflection loss and absorption loss due to the transparent conductive film. Table 17 shows the refractive index before and after annealing of the transparent conductive film, and Table 18 shows the change in extinction coefficient before and after annealing of the transparent conductive film. Table 17 (a) shows the refractive index characteristics of hydrogen atom-added indium oxide, and Table 17 (b) shows the refractive index characteristics of Comparative Example: ITO. Table 18 (a) shows the extinction coefficient characteristics of hydrogen atom-added indium oxide, and Table 18 (b) shows the extinction coefficient characteristics of Comparative Example: ITO. The refractive index and extinction coefficient are measured using spectroscopic ellipsometry for a sample having a structure in which aluminum (1) as a back electrode and silver (6) as a comb electrode are not formed in the structure of the photoelectric conversion element. evaluated. Table 19 shows changes in electrical characteristics before and after annealing of the transparent conductive film. Table 19 (a) shows the electrical measurement characteristics of hydrogen atom-added indium oxide, and Table 19 (b) shows the electrical characteristics of Comparative Example: ITO. The electrical characteristics were evaluated by measuring holes on the transparent conductive film on the glass substrate produced simultaneously with the production of the photoelectric conversion element.

  As is clear from Table 17 and Table 18, when comparing the hydrogenated indium oxide thin film and the ITO thin film treated with the same annealing temperature before annealing and hydrogenated indium oxide, the hydrogenated indium oxide is more effective in the visible region and near infrared region than ITO. It can be seen that the attenuation coefficient is small, and that the refractive index is high mainly in the wavelength region of 600 nm or more. From this result, the spectral sensitivity characteristics of the product of the present invention were superior to those of the conventional product. The reflection loss due to the reduction of absorption loss in the visible region and near infrared region and the difference in refractive index between the thin film silicon layer and the transparent conductive film. It was shown to be a reduction of

In the product of the present invention, the current density is greatly increased when the annealing temperature is about 140 ° C. or higher. This phenomenon is also due to a reduction in absorption / reflection loss. As is clear from Table 19, the carrier concentration of the transparent conductive film is decreased and the mobility is improved by annealing at about 140 ° C. or higher. Therefore, as apparent from Table 18 and Table 17, the extinction coefficient of the hydrogenated indium oxide thin film is reduced, the refractive index is improved, and the absorption / reflection loss due to the transparent conductive film is reduced. In addition, since both the hydrogenated indium oxide thin film before annealing and the annealing treatment exhibited a resistivity as low as 5 × 10 ⁻⁴ Ωcm or less, the electrical characteristics of the photoelectric conversion element of the present invention deteriorated. I understand that it is not.

  In this embodiment, as is clear from Table 15, both the present product and the conventional product cause a decrease in open circuit voltage and a decrease in fill factor at an annealing temperature of 150 ° C. or higher, and as a result, the conversion efficiency is greatly decreased. Therefore, at an annealing temperature of 150 ° C. or higher, conversion efficiency is not improved due to a significant improvement in current density in the product of the present invention. However, the manufacturing conditions and film characteristics of the i-type amorphous silicon (3) and p-type amorphous silicon (4) layers produced at a film forming temperature of 130 ° C., which is the dominant factor of deterioration of the open circuit voltage and the fill factor with respect to the annealing temperature, are improved. Thus, it goes without saying that the conversion efficiency can be improved by greatly increasing the current density.

  The present invention is not limited to the photoelectric conversion element having the structure described above, but can be applied to photoelectric conversion elements having other structures. For example, as shown in the schematic cross-sectional view of the photoelectric conversion element in FIG. 11, an i-type silicon-based thin film (14), an n-type silicon-based thin film (13) on the lower surface of n-type or p-type silicon (15), and the dopant of the present invention. An oxide conductive film (12) to which a certain hydrogen atom is added, a comb electrode (11), an i-type silicon thin film (16), and a p-type silicon thin film (17) on the upper surface of n-type or p-type silicon (15) The present invention can also be applied to a hetero pn-junction photoelectric conversion element such as a heterojunction photoelectric conversion element composed of an oxide conductive film (18) to which hydrogen atoms, which are dopants of the present invention, are added, and a comb-shaped electrode (19). is there. Furthermore, the present invention can be applied to the case where a group IV semiconductor such as silicon germanium, silicon carbide, germanium, or the like other than silicon is used as the semiconductor material.

FIG. 12 is a schematic cross-sectional view of a silicon-based thin film photoelectric conversion element using an oxide conductive film to which a hydrogen atom as a dopant of the present invention is added as a transparent electrode of the photoelectric conversion element.
Metal electrode (22), transparent conductive film (23), n-type microcrystalline silicon (24), i-type microcrystalline silicon (25), p-type microcrystalline silicon (26), dopant of the present invention on substrate (21) It is comprised from the oxide electrically conductive film (27) which added the hydrogen atom which is. Instead of the microcrystalline silicon film, amorphous silicon, amorphous silicon germanium, or microcrystalline silicon germanium whose spectral sensitivity region ranges from the ultraviolet region or the visible region to the near infrared region can be used instead of the microcrystalline silicon film.
FIG. 12 shows an example of application to a substrate type solar cell in which a back electrode is provided on the substrate side, but from the transparent substrate side, which is another general structure of a silicon-based thin film solar cell, to the photoelectric conversion layer. It can also be applied to a super straight type solar cell that takes in light.

FIG. 13 is a schematic cross-sectional view of a photoelectric conversion element using an oxide conductive film to which a hydrogen atom, which is a dopant of the present invention, is added as a transparent electrode of a compound-based thin film solar cell.
Add metal electrode (32), p-type semiconductor material CuInSe ₂ thin film (33), cadmium sulfide thin film (34), zinc oxide thin film (35), hydrogen atom as dopant of the present invention on glass substrate (31) It comprises an oxide conductive film (36) and a comb electrode (37). It may be to use a chalcopyrite semiconductor, such as the same chalcopyrite-based material as the light-absorbing layer _{Cu (In 1-x Ga x} ) Se 2-2y S 2y (0 ≦ x ≦ 1,0 ≦ y ≦ 1) .
In FIG. 13, a chalcopyrite thin film solar cell is shown as an example, but the oxide conductive film to which a hydrogen atom of the present invention is added is applied as a transparent electrode of another compound thin film solar cell such as a CdTe thin film solar cell. I can do it.

  FIG. 14 is a schematic cross-sectional view of a photodetecting element using an oxide conductive film added with hydrogen atoms, which is the dopant of the present invention, as a transparent electrode of the photodetecting element. An oxide conductive film (42) to which hydrogen atoms as dopants of the present invention are added on a glass substrate (41), a calcium sulfide photodetection layer (43) to which europium and samarium are added, and a metal electrode (44). Since the oxide conductive film to which a hydrogen atom, which is the dopant of the present invention, is added has high transparency in the visible region as well as in the near infrared region, a photodetector in the visible region can also be realized. Moreover, even in the case of a light detecting element using a light detecting material layer using an avalanche photodiode or a photo diode, the near infrared sensitivity is improved by using the transparent oxide electrode film of the present invention as an electrode on the near infrared incident side. it can.

  In view of the characteristics of FIG. 7, the oxide transparent conductive film has a hydrogen atom content of the oxide conductive film containing hydrogen atoms at an arbitrary value within a range of 1% to 10%. The reason for this is that the hydrogen atom content of the oxide conductive film containing hydrogen atoms from the viewpoint of the characteristics of FIG. Is less than 10%, and data below 1% is inaccurate, so the lower limit is 1% or more.

From these, the indispensable condition for realizing the performance required by the oxide transparent conductive film of the present invention, the photoelectric conversion element using the same, and the photodetection element are:
(1) The oxide film transparent conductive film is amorphous and contains an arbitrary value within the range of 1% or more and 10% or less of the hydrogen atom content.
Moreover,
(2) Annealing and crystallizing the amorphous oxide transparent conductive film of (1) above.
Furthermore, the temperature, water vapor partial pressure, water or hydrogen gas as the hydrogen atom source as production conditions when the oxide film transparent conductive film is produced by appropriately adjusting the total water vapor partial pressure in the film production chamber Depending on the situation, the individual conditions change. The annealing temperature after film formation is, for example, greater than 150 ° C.
In addition to the above description, the configuration and the manufacturing method can be arbitrarily changed as long as the intended configuration and functions are provided.

Claims (7)

A photoelectric conversion element comprising a transparent electrode as an oxide transparent conductive film and a photoelectric conversion layer adjacent to the transparent electrode ,
The oxide transparent conductive film is a thin film containing any one of indium oxide, gallium oxide, zinc oxide, magnesium oxide, tin oxide, germanium oxide, titanium dioxide film, or two or more compounds thereof.
The oxide transparent conductive film is an amorphous oxide conductive film containing hydrogen atoms, the hydrogen atom content is an arbitrary value within the range of 1% to 10%, and the electron mobility is measured by Hall effect measurement. Is an arbitrary value of 40 cm ² / Vs or more, a carrier concentration is an arbitrary value of 5 × 10 ²⁰ cm ⁻³ or less, a refractive index at an arbitrary wavelength within a wavelength range of 400 nm to 1200 nm is 1.5 or more, A photoelectric conversion element having a specific resistance of an arbitrary value of 5 × 10 ⁻⁴ Ωcm or less.   The photoelectric conversion element according to claim 1, wherein the transparent oxide conductive film is a thin film containing elements of indium and oxygen.   The photoelectric conversion element according to claim 2, wherein the oxide transparent conductive film is a hydrogen atom-added indium oxide thin film. It is a photoelectric conversion element of any one of Claims 1 thru | or 3, Comprising:
A first electrode layer, a conductive oxide layer, an n-type thin film semiconductor layer, an i-type thin film semiconductor layer, a p-type thin film semiconductor layer, and a second electrode layer disposed in order from the substrate side; A photoelectric conversion element for generating a photovoltaic force by light incident from the electrode layer side of the electrode, wherein the second electrode layer is the transparent electrode of the oxide transparent conductive film. It is a photoelectric conversion element of any one of Claims 1 thru | or 3, Comprising:
The oxide transparent conductive film is formed on the light incident side by a heterojunction in which a reverse conductivity type thin film semiconductor layer or an i type thin film semiconductor layer and a reverse conductivity type thin film semiconductor layer are formed on a single conductivity type crystalline semiconductor. A photoelectric conversion element characterized by forming a transparent electrode. It is a photoelectric conversion element of any one of Claims 1 thru | or 3, Comprising:
A first electrode layer, a p-type semiconductor layer, an n-type semiconductor layer, and a second electrode layer are provided in order from the substrate side, and photovoltaic power is generated by light incident from the first or second electrode layer side. A photoelectric conversion element, wherein the first or second electrode layer is the transparent electrode of the oxide transparent conductive film. The photoelectric conversion element according to claim 1 is a light detection element,
A photodetecting element comprising a pair of electrodes and a photodetecting material layer sandwiched between the electrodes, wherein at least one of the pair of electrodes is the transparent electrode of the oxide transparent conductive film .