JP2017005092A - Light emitting diode and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light emitting diode which is excellent in chemical stability and long term durability by achieving a p-type semiconductor thin film comprising an oxide.SOLUTION: In a light emitting diode including a p-type semiconductor layer, a light emitting layer and an n-type semiconductor layer, the p-type semiconductor layer comprises an oxide semiconductor thin film that has a perovskite-type related structure and contains one or two or more elements among Co, Rh, Ru, Mn and Ir, a rare earth element, and an alkali earth metal element. A specific composition of the oxide semiconductor thin film is represented by chemical formula: (REAE)M1Oor (AERE)M2O(where, RE represents one or two or more elements among rare earth elements, AE represents one or two or more elements among alkali earth metal elements of Ca, Sr, and Ba, M1, M2 represent one or two or more elements among Co, Rh, Ru, Mn and Ir, and 0<x≤1 and 0<y≤1 are satisfied).SELECTED DRAWING: Figure 10

Description

  The present invention relates to a light emitting diode using an oxide semiconductor thin film realizing p-type semiconductor characteristics and a method for manufacturing the same.

  In recent years, a light emitting diode (LED) is a useful technology as an energy saving device. LEDs are attracting attention as an alternative to conventional incandescent bulbs such as traffic lights and lighting. “LED illumination”, which combines GaN blue light emission and yellow phosphor, has a problem in that it is a point light source with a limited viewing angle. Development of materials other than GaN is desired.

  By the way, an oxide having both chemical stability and long-term durability has various performances excellent in electrical and optical properties.

  In recent years, research on the development of transparent p-type semiconductors using oxides has been actively conducted, and development of materials and devices for wide-gap semiconductors has progressed centering on delafossite-type oxides and zinc oxide.

The present inventors have conducted research and development on oxide perovskite phosphors. A perovskite oxide phosphor epitaxial thin film Pr- (Ca, Sr) TiO ₃ was epitaxially grown on a single-side polished SrTiO ₃ single crystal substrate by a pulse laser deposition method, and the fluorescence characteristics were examined. As a result, the epitaxial thin film obtained red fluorescence characteristics as ultraviolet-excited light emission (see Non-Patent Document 1).

When a prior literature search related to the present application was conducted, the following literature was found. Patent Document 1 describes a variable resistance element using a semiconductor material exhibiting p-type Mn-based perovskite oxide. Patent Document 2 discloses a resistor in which a Schottky barrier is arranged between a perovskite oxide p-type semiconductor Pr _0.5 Ca _0.5 MnO ₃ and an n-type semiconductor and the three members are joined to form an oxide pn junction. A variable nonvolatile memory is described. In Patent Document 3, in a Pr _1-x Ca _x MnO ₃ perovskite type oxide, oxygen moves at the interface between the oxide and the electrode, and the resistance change in which the oxygen concentration uniformly changes and changes in resistance throughout the electrode interface. The device is described. Patent Document 4 describes that a pn junction is formed with a p-type semiconductor layer and an n-type perovskite oxide layer formed of a perovskite oxide BiFeO ₃ in relation to a photoelectric conversion element. Non-Patent Document _{2, (La 1-x Sr} x) CoO 3 polycrystal (La3 + site of the perovskite type LaCoO ₃ is substituted partially by _{Sr2 + (La 1-x Sr} x) CoO 3 polycrystals) The thermoelectric properties of are described. Further, it is described that the conductivity is increased by Sr doping. In addition, studies on p-type semiconductors of (Sr _1-x La _x ) ₂ RhO ₄ and La _1-x Sr _x RhO ₃ bulk powder have been reported (Non-patent Document 3, Non-patent Document 4, Non-patent Document). 5). Regarding bulk and powder of SrRuO ₃ , non-patent document 6 reports research on p-type semiconductors.

International Publication No. 2007-026509 JP 2008-34641 A JP 2012-15211 A JP 2014-175554 A

H. Takashima, K. Ueda, M. Itoh, Applied Physics Letters. Vol 89, 261915 (2006) Journal of Solid State Chemistry 181, 3145 (2008) Journal of Solid State Chemistry 103, 523 (1993) Journal of Solid State Chemistry 98, 198 (1992) Physical Review B 49, 5591 (1994) Physical Review B 51, 16432 (1995)

  Conventionally, a transparent oxide has been studied as an oxide for realizing a p-type semiconductor, but it is still rare. A p-type semiconductor means a carrier whose holes are holes. As a factor that makes it difficult to develop a p-type semiconductor using a transparent oxide, in the band structure, the upper end of the valence band that conducts holes consists of a highly localized O2p band, and thus the carrier mobility is lowered. It is done.

“Non-transparent” materials with relatively narrow band gaps have a much wider range of selectivity, and there is plenty of room for breaking the above-noted theory. In fact, it has been reported that a p-type semiconductor characteristic can be obtained by adding an alkaline earth metal to the A site of the perovskite oxide (chemical formula ABO ₃ ) (see Non-Patent Document 2 and Non-Patent Document 5). .)

Conventionally, in oxides having a perovskite structure, p-type semiconductors in which carriers are holes are reported, except for BiFeO ₃ films (Patent Document 4), which are both bulk and powder polycrystals. There is no thin film (see each patent document and each non-patent document). Therefore, a semiconductor element having a p-type semiconductor thin film of a perovskite oxide and a pn junction using the p-type semiconductor thin film other than BiFeO ₃ has not been realized so far.

  Since the current light emitting diode is a point light source, its viewing angle is limited and its application is limited. Therefore, development of a surface emitting light emitting diode is eagerly desired. A light emitting diode using an oxide thin film having a perovskite structure has not been reported yet.

  The present invention is intended to solve these problems. The present invention provides a novel p-type semiconductor thin film using an oxide having a perovskite-related structure, and a light-emitting diode including the p-type oxide semiconductor thin film. The purpose is to provide. It is another object of the present invention to provide a method of manufacturing a light emitting diode including the p-type semiconductor oxide semiconductor thin film.

  The present invention has the following features in order to achieve the above object.

The light-emitting diode of the present invention is a light-emitting diode comprising a p-type semiconductor layer, a light-emitting layer, and an n-type semiconductor layer, and the p-type semiconductor layer has a perovskite-type related structure, and Co, Rh, Ru, Mn, It is an oxide semiconductor thin film containing one or more elements of Ir, a rare earth element, and an alkaline earth metal element. The p-type semiconductor layer has a perovskite-type related structure, and the composition is represented by the chemical formula: (RE _1-x AE _x ) M ₁ O ₃ or (AE _1-y RE _y ) ₂ M ₂ O ₄ One or more elements among the elements (Sc, Y, lanthanoid (La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu)) AE is one or more of the alkaline earth metal elements Ca, Sr and Ba, M1 and M2 are one or more of Co, Rh, Ru, Mn and Ir. It is an oxide semiconductor thin film represented by an element, 0 <x ≦ 1, 0 <y ≦ 1). The mobility of the oxide semiconductor thin film is preferably 0.02 cm ² / Vs or higher. Preferably, the rare earth element is La and the alkaline earth metal element is Sr. The n-type semiconductor layer is preferably an oxide semiconductor thin film. The light emitting layer is preferably an oxide thin film.

  The method for producing a light-emitting diode according to the present invention is characterized in that the p-type semiconductor layer in the light-emitting diode is produced by depositing an oxide thin film having a perovskite-type related structure in an oxygen atmosphere. The method for producing a light-emitting diode according to the present invention is characterized in that the p-type semiconductor layer in the light-emitting diode is manufactured by depositing an oxide thin film having a perovskite structure and then heat-treating it in an oxygen atmosphere.

  According to the present invention, a light-emitting diode in which the p-type semiconductor layer is made of an oxide thin film having a perovskite-type related structure can be realized. Since the p-type semiconductor layer of the present invention is made of an oxide material, it is excellent in chemical stability and long-term durability. Further, according to the present invention, the pn junction structure using the p-type semiconductor thin film can be made of an oxide material, so that the lifetime can be extended.

According to the present invention, an oxide thin film having a perovskite-type related structure that constitutes a light-emitting diode, realizes a carrier mobility of a p-type semiconductor thin film exceeding 0.02 cm ² / Vs, and further 1.05 cm ^2. / Vs or more is also possible. In addition, a pn junction structure using a p-type semiconductor thin film made of an oxide thin film having a perovskite related structure was realized.

  The oxide semiconductor thin film in the light-emitting diode of the present invention is very suitable for use as a lower layer film when forming a laminated structure such as a pn junction because the surface of the thin film is flat.

  The oxide semiconductor thin film in the light-emitting diode of the present invention can have a band gap value of 0.9 to 2.5 eV by controlling the combination and composition of elements in the perovskite-related structure. As a result, a light-emitting diode can be manufactured using an oxide material, so that it is easy to realize desired semiconductor characteristics such as carrier concentration and resistivity.

2 is an X-ray crystal diffraction measurement diagram of an oxide semiconductor thin film according to the first embodiment. FIG. It is a figure which shows the in-plane orientation of the oxide semiconductor thin film in 1st Embodiment. It is a figure showing the mode of the surface of the oxide semiconductor thin film in 1st Embodiment. It is a circuit diagram used for the current-voltage measurement of the pn junction in 6th Embodiment. It is a figure which shows the current-voltage characteristic of the pn junction in 6th Embodiment. It is a figure which shows the current-voltage characteristic of the pn junction in 6th Embodiment. It is a figure which shows the current-voltage characteristic of the pn junction in 6th Embodiment. It is a figure which shows the current-voltage characteristic of the pn junction in 6th Embodiment. It is a figure which shows the current-voltage characteristic of the pn junction in 6th Embodiment. It is a figure which shows the direct current light emission characteristic (a) and laminated structure (b) of the light emitting diode in 7th Embodiment. It is a figure which shows the wavelength spectrum at the time of light emission of the light emitting diode in 7th Embodiment.

  Embodiments of the present invention will be described below.

In La _1-x Sr _x CoO ₃ known as a p-type semiconductor in a bulk state, it is holes and oxygen that are responsible for electrical conduction. When oxygen defects occur, it is estimated that n-type semiconductor characteristics are exhibited. Therefore, a manufacturing process that does not cause oxygen defects is essential. Preliminary experiments by the present inventors have revealed that stable p-type semiconductor characteristics can be obtained by sufficiently introducing oxygen in La _1-x Sr _x CoO ₃ powder and bulk materials. By thinning the film by a pulse laser deposition method described later, a single-phase thin film was obtained under film forming conditions of a certain oxygen pressure or higher, and a film that clearly showed p-type semiconductor characteristics at room temperature was obtained.

The inventors of the present invention performed thinning by vapor phase growth of, for example, Co-based and Rh-based perovskite oxides among the B sites of perovskite-type oxides (chemical formula ABO ₃ ), and investigated their band gaps. As a result, a p-type semiconductor single crystal thin film having a band gap of 1.0 eV to 2.5 eV was obtained with a plurality of compositions, and the present invention was reached.

This embodiment is a perovskite oxide _{(RE 1-x AE x)} BO 3 oxide structure (Co-based oxide, Rh-based oxide, Mn-based oxide, Ru based oxide, Ir-based oxide ) And (AE _1-y RE _y ) ₂ BO ₄ structure oxide (Co-based oxide, Rh-based oxide, Mn-based oxide, Ru-based oxide, Ir-based oxide). Including both, the oxide has a perovskite related structure.

  In an embodiment of the present invention, a p-type semiconductor layer is realized for the first time in an oxide semiconductor thin film having a perovskite-type related structure having the following composition, and a light-emitting diode including the p-type semiconductor layer is realized.

The oxide thin film according to an embodiment of the present invention has a composition represented by the chemical formula: (RE _1-x AE _x ) M ₁ O ₃ or (AE _1-y RE _y ) ₂ M ₂ O ₄ (where RE is a rare earth element (Sc) , Y, lanthanoid (La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu)), AE is , One or more elements of alkaline earth metal elements Ca, Sr, Ba, M1, M2 are one or more elements of Co, Rh, Ru, Mn, Ir, 0 <X ≦ 1, 0 <y ≦ 1).

  A typical composition is La for RE and AE for Sr.

The chemical formula: (RE _1-x AE _x ) M ₁ O ₃ is a system in which a 3+ valent rare earth element is replaced with a 2+ valent alkaline earth metal element.
Chemical formula: (RE _1-x AE _x ) M ₁ O ₃ (RE is a rare earth element (Sc, Y, lanthanoid (La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er) , Tm, Yb, Lu)), AE is one or more of the alkaline earth metal elements Ca, Sr, Ba, M1 is Co, One or more elements of Rh, Ru, Mn, and Ir, represented by 0 <x ≦ 1). For example, it includes a composition in which La is replaced with Sr and all La is replaced with Sr. SrRuO ₃ is included, but LaCoO ₃ is not included.
A particularly preferable range of x depending on the type of the metal element M1 is, for example, as follows.
When M1 is Co, 0 <x ≦ 0.5. This is because when x exceeds 0.5, oxygen becomes less than 3.0, not 3.0, and the electrical neutral condition is not satisfied.
Also when M1 is Rh, 0 <x ≦ 0.5. This is because when x exceeds 0.5, oxygen becomes less than 3.0 instead of 3.0, and the electrical neutral condition is not satisfied.
The same applies when M1 is Ir.
When M1 is Mn, 0 <x <0.33. This is because when x is 0.4 or more, oxygen is less than 3.0 instead of 3.0 and the electrical neutral condition is not satisfied, and when it exceeds 0.5, it is difficult to synthesize a single phase. This is because the p-type was not realized at 0.33.
When M1 is Ru, 0.9 <x ≦ 1. This is because it is difficult to synthesize a single phase when x is 0.9 or less.

Chemical _{formula: (AE 1-y RE y} ) 2 M2O 4 is a system to replace the 2 + valence of an alkaline earth metal element in 3+ valence of rare earth elements.
Chemical formula: (AE _1-y RE _y ) ₂ M ₂ O ₄ (where RE is a rare earth element (Sc, Y, lanthanoid (La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu)), one or more elements, AE is one or more of the alkaline earth metal elements Ca, Sr, Ba, and M2 is Co , Rh, Ru, Mn, and Ir, represented by one or more elements, 0 <y ≦ 1).
A particularly preferable range of y depending on the type of the metal element M2 is, for example, as follows.
When M2 is Rh, 0 <y ≦ 0.5. This is because it is difficult to synthesize a single phase when x exceeds 0.5.
The same applies when M2 is Ir.

  Depending on the types of the metal elements M1 and M2, the preferable ranges of x and y slightly vary depending on whether or not a single phase can be synthesized, electrical neutral conditions, and the amount of oxygen. Further, the band gap value can be set by changing and controlling the combination and composition of elements.

  In the present invention, the composition may contain a slight amount (about 1% or less) of a metal element. Elements that can be expected to obtain p-type characteristics even when a small amount of element is substituted include Cr, Fe, Ni, Cu, Mo, W, and Ir.

  The oxide semiconductor thin film in the present invention is a single crystal thin film or a polycrystalline thin film. A single crystal thin film is more preferable. Moreover, it is preferable that it is an epitaxial layer.

As the substrate on which the oxide semiconductor thin film is formed in the present invention, for example, a perovskite oxide substrate (LaAlO ₃ , Nb-added SrTiO _3, etc.) or another oxide substrate (MgO, etc.) can be used. The substrate may be single crystal or polycrystalline. When the oxide semiconductor thin film is an epitaxial layer, the substrate is preferably a perovskite oxide, and a single crystal substrate is used.

The mobility of the p-type semiconductor oxide semiconductor thin film in the present invention at room temperature is 0.02 cm ² / Vs or more. In a LaSr-based perovskite-type Co oxide, it is 0.1 cm ² / Vs or more. Furthermore, 1.0 cm ² / Vs or more could be realized.

  The light-emitting diode of the present invention is a semiconductor element including a p-type semiconductor oxide semiconductor thin film having a perovskite-type related structure. By using the oxide semiconductor thin film of the p-type semiconductor, a semiconductor element having a pn junction structure, a rectifying semiconductor element, a photoelectric conversion element, a solar cell, and the like can be realized. In the semiconductor element including the p-type semiconductor layer of the oxide semiconductor thin film and the n-type semiconductor layer that pn-joins with the p-type semiconductor layer, the pn junction preferably includes an insulating layer at the junction interface. Rectification characteristics can be obtained by a pin stack structure of a p-type semiconductor layer, an i-type insulating layer, and an n-type semiconductor layer. Since the oxide semiconductor thin film of the p-type semiconductor of the present invention has a flat thin film surface, it is suitable for forming another layer on the surface, and an excellent semiconductor multilayer structure can be realized.

The composition of the n-type semiconductor thin film used for the light emitting diode of the present invention is not particularly limited. An oxide semiconductor layer can be used. For example, an oxide semiconductor thin film having a perovskite related structure or a non-perovskite related structure, which is already known as an n-type semiconductor, can be used. InGaZnO ₄ (hereinafter also referred to as IGZO) and La—SrTiO ₃ can be given. Since the n-type semiconductor thin film has a laminated structure including the p-type semiconductor thin film, it is preferable that the p-type and the manufacturing method are common or the chemical formula is similar.

The light emitting layer in the light emitting diode of the present invention is not limited to its composition. Perovskite oxide phosphors can be used. For example, ((Ca _1−x Sr _x ) _1−y ) P r _y TiO ₃ (0 ≦ x ≦ 0.6, 0 <y ≦ 0.2) ((Ca _0.6 Sr _0.4 ) _{0. 997} ) Pr _0.002 TiO ₃ is preferred.

  The light-emitting diode of this embodiment can be manufactured by applying a p-type semiconductor oxide semiconductor thin film to a known structure of a light-emitting diode. The light-emitting diode of the present embodiment includes at least a p-type layer made of the p-type semiconductor oxide semiconductor thin film of the present invention, a light-emitting layer, and a stacked structure in which an n-type semiconductor layer is stacked in this order, and an electrode structure. When an oxide thin film is used as the light emitting layer or the n-type semiconductor layer, it is chemically stable and more durable. An already known buffer layer or the like may be appropriately provided.

The oxide semiconductor thin film in the embodiment of the present invention is non-transparent. Since the band gap value is 2.5 eV or less, it is not transparent but black. The element structure of the light emitting diode is typically lower solid substrate / lower conductive film / p-type semiconductor thin film / light emitting layer / n-type semiconductor thin film / upper transparent conductive film. The transparent conductive film can be used as long as it is a transparent and conductive material. For example, ATO (Sb substitution-SnO ₂ ), ITO (indium tin oxide), zinc oxide and the like are preferable.

  The p-type semiconductor thin film in this embodiment can be manufactured by a pulse deposition method that is a vapor phase growth method, CVD, sputtering, a spin coating method that is a liquid phase growth method, or the like. By using the pulse deposition method, the crystallinity is excellent and high luminance can be obtained. In particular, in order to obtain a p-type semiconductor, it is preferable to deposit in an oxygen atmosphere. Examples of the oxygen atmosphere include air (atmospheric pressure) and the like, and the oxygen partial pressure is preferably 10% or more.

  In addition, when the thin film obtained by depositing the oxide thin film having a perovskite related structure is not p-type, it can be converted into a p-type semiconductor thin film by heat treatment in an oxygen atmosphere. Examples of the oxygen atmosphere in the heat treatment step include air (atmospheric pressure), and the oxygen partial pressure is preferably 10% or more.

  The thickness of the p-type semiconductor thin film of the perovskite oxide in the present invention is not particularly limited. When used as a p-type semiconductor layer of a light emitting diode, it preferably has a thickness of 50 nm or more.

(First embodiment)
This embodiment relates to a case where the composition of the p-type semiconductor layer of the light-emitting diode is represented by the chemical formula: (RE _1-x AE _x ) M ₁ O ₃ .

[Preparation of target]
A method for manufacturing a target for manufacturing an oxide thin film will be described using Sr-added LaCoO ₃ as an example.
In Sr-added LaCoO ₃ , lanthanum oxide (La ₂ O ₃ ), strontium carbonate (SrCO ₃ ), and cobalt oxide (Co ₃ O ₄ ) are used as raw materials and become La _1-x Sr _x CoO ₃ in a stoichiometric composition. And weighed uniformly in an agate mortar by dry mixing. After mixing, calcination is performed in the air at a temperature of 800 ° C. for 24 hours. Then, it grind | pulverizes and mixes, shape | molds into a cylindrical pellet of diameter 20mm and thickness about 5mm with a press, and baking is performed in air | atmosphere for 24 hours at the temperature of 900 to 1200 degreeC. This is a pulse laser target.

[Preparation of thin film]
Next, a method for manufacturing an oxide thin film will be described. In this embodiment, a pulsed laser deposition method (PLD) is used. In the pulsed laser deposition method, an excimer laser such as ArF (wavelength 193 nm) is irradiated to form a target material into a plasma to form a plume, and a thin film is deposited on a heated solid substrate disposed facing the target material. It is a technique to make it. A SrTiO ₃ (001) single-side polished single crystal substrate was used as the solid substrate.
As the target material, a La _0.67 Sr _0.33 CoO ₃ polycrystal having a stoichiometric composition was used. The distance between the target and the solid substrate was 28-35 mm, and the solid substrate was heated to 400-700 ° C. by a lamp heater. The laser irradiation frequency is 4-16 Hz, and the laser energy is about 20-50 mJ. A typical film formation time was 15 to 60 minutes, and a film thickness was 100 to 400 nm. More preferably, the distance between the solid substrates is 30-34 mm, the substrate heating temperature is 400-500 ° C., the laser irradiation frequency is 8-16 Hz, and the laser energy is about 30-40 mJ. These numerical ranges are typical numerical values, and it does not mean that there is no effect unless they are within this range. In the production of the perovskite type oxide thin film according to the present invention, since the film formation is performed under the condition of 1000 ° C. or less, the cluster growth is dominant, and the target material is deposited as a thin film with the stoichiometric composition. Can be made. Further, the target material is made of an oxide, and by forming a film in an oxygen atmosphere, oxygen vacancies and the like can be controlled, whereby the electrical characteristics can be controlled.

[Analysis of thin film]
FIG. 1 shows the result of crystal diffraction measurement by X-ray of a La _0.67 Sr _0.33 CoO ₃ thin film formed by a pulse laser deposition method. From FIG. 1, it can be seen that the thin film is oriented in the (001) direction, and it can be confirmed that the single-phase target composition can be produced as a thin film. FIG. 2 shows the results of φ scan measurement using X-rays. FIG. 2 confirms the four-fold symmetry diffraction peak and shows that the in-plane orientation is achieved. Further, as a result of reflection high energy electron diffraction (RHEED) observation, a streak-like diffraction pattern was observed, and it was found that the outermost surface of the thin film had crystallinity. As a result, it was clarified that the produced thin film was single crystal.
FIG. 3 is a morphology (uneven structure) of the surface of the La _0.67 Sr _0.33 CoO ₃ thin film observed with an atomic force microscope (AFM). From FIG. 3, it was confirmed that the surface roughness was 50 nm or less. FIG. 3 shows that a thin film having a very flat surface structure was obtained. When a laminated device is used, the thin film used for the lower layer causes an electrical micro short if the surface structure is not flat. Since a flat thin film is formed as shown in FIG. 3, when the pn junction is formed, the thin film of this embodiment can be used as a lower layer film, and is a surface type (plane type) pn. Useful for bonding.

[Hall coefficient of thin film]
The Hall coefficient of the prepared thin film was measured at room temperature.
The measurement of the Hall coefficient of the thin film will be described in detail. In a p-type or n-type semiconductor sample, a current is applied in the x direction and a magnetic field is applied in the z direction. At this time, charged particles (carriers) flowing through the sample are accelerated in the y direction under the Lorentz force by the magnetic field. As a result, carriers accumulate on the surface of the sample, an electric field is generated in a direction orthogonal to both the current and the magnetic field, and an electromotive force is generated. The analysis can measure the type and density of semiconductor carriers. A specific resistance / hall measurement system was used to measure the Hall coefficient. The frequency during AC measurement was measured in the range of 50 to 200 mHz. When the S / N ratio was sufficient with direct current, measurement was performed with direct current. A typical applied magnetic flux density is 0.4T. In addition, a cryopump was used to realize a low temperature environment from room temperature to about 20K, and the Hall coefficient was measured.
From the Hall coefficient measurement measured at room temperature, the specific resistance, carrier concentration, and mobility of an La _0.67 Sr _0.33 CoO ₃ thin film prepared at an oxygen atmosphere of 400 mTorr and a substrate temperature of 540 ° C. were 4.20 × 10 ^−3. Ωcm, 1.29 × 10 ²² cm ⁻³ , 1.10 cm ² / Vs, and it was found that the carrier was a hole and a p-type semiconductor.

  The main cause of the p-type semiconductor of the material of the present embodiment is oxygen. It is presumed that oxygen vacancies are likely to occur when the oxygen pressure during film formation is low, while oxygen vacancies are less likely to occur when the oxygen pressure during film formation is high. For this reason, the film was formed with the substrate temperature kept constant and the oxygen pressure during film formation being selected from 10 mTorr, 20 mTorr, 40 mTorr, 10 mTorr, 100 mTorr, 200 mTorr, 400 mTorr, and 1000 mTorr. The Hall coefficient of the deposited thin film was measured at room temperature. As a result, it became clear that the carrier was a hole in the region where the oxygen pressure was 40 mTorr or more, and it was found to be a p-type semiconductor. In the region where the oxygen pressure is 20 mTorr or less, it is impossible to determine whether the carrier is a hole or an electron by measuring the Hall coefficient. Cluster growth is dominant under film forming conditions where the substrate holding temperature is 1000 ° C. or lower. Since the target material is sufficiently heat-treated in oxygen, there is no oxygen deficiency and p-type semiconductor characteristics are exhibited. From this result, it can be presumed that, when the film is formed at an oxygen pressure of 20 mTorr or less, oxygen vacancies are easily generated in the cluster, and sufficient oxygen does not remain in the thin film, so that p-type semiconductor characteristics are not exhibited.

Next, thin films were prepared for La _0.9 Sr _0.1 CoO ₃ having different composition ratios, and Hall coefficient measurement was performed. As typical film formation conditions, film formation was performed at an oxygen pressure of 100 mTorr and a substrate temperature of 540 ° C. As a result of measuring the Hall coefficient, the carrier concentration and the mobility were 5.27 × 10 ²⁰ cm ⁻³ and 0.13 cm ² / Vs, respectively, and it was found that the carrier was a hole and a p-type semiconductor. When the oxygen pressure is 10 mTorr, the carrier coefficient and the mobility are 5.84 × 10 ²⁰ cm ⁻³ and 0.1 cm ² / Vs, respectively, as a result of the Hall coefficient measurement, and the carriers are holes and are p-type semiconductors. I understood. In a sample formed with an oxygen pressure of less than 10 mTorr, it was difficult to identify carriers by measuring the Hall coefficient.

[Comparative Example 1]
A thin film was prepared for LaCoO ₃ to which Sr was not added, and the Hall coefficient was measured. As typical film formation conditions, film formation was performed at an oxygen pressure of 100 mTorr and a substrate temperature of 540 ° C. As a result of measuring the Hall coefficient, it was difficult to identify the carrier.

[Comparative Example 2]
The case where M1 in the chemical formula: (RE _1-x AE _x ) M1O ₃ is Ti was examined.
Nb-added SrTiO ₃ is shown as a comparative example. SrTi _0.99 Nb _0.01 O ₃ was formed under typical film formation conditions at an oxygen pressure of 100 mTorr and a substrate temperature of 540 ° C. _{Incidentally,} the SrTi _{0.99 Nb 0.01} O ₃ Applying the chemical formula _{(RE 1-x AE x)} M1O 3, can also be expressed as Nb 0.01 _{SrTi 0.99} O _3. As a result of measuring the Hall coefficient, the specific resistance, the carrier concentration, and the mobility are 2.59 × 10 ⁻² Ωcm, 1.90 × 10 ²⁰ cm ⁻³ , and 1.26 cm ² / Vs, respectively, and the carriers are electrons and n It was found to be a type semiconductor. Even when the film was formed at an oxygen pressure of 10 mTorr to 400 mTorr, the carriers were electrons and an n-type semiconductor.
La-added SrTiO ₃ is shown as a comparative example. Even in Sr _0.995 La _0.005 TiO ₃ , the same oxygen vacancies as in SrTi _0.99 Nb _0.01 O ₃ described above are generated, so that it can be inferred that the carriers are electrons and an n-type semiconductor.

As a result of examination including comparative examples and the like, the reason for becoming p-type or n-type depending on the ratio of AE (Sr etc.) is considered as follows. In RE _1-x AE _x CoO _3-δ , a + 3-valent site of RE (La, etc.) is replaced with an AE (Sr, etc.) 2 + -valent atom, and oxygen diffusion in the crystal is sufficient when the substitution amount is small. Therefore, δ = 0. However, when the substitution amount x of AE (Sr, etc.) increases, oxygen diffusion in the crystal becomes insufficient, resulting in oxygen deficiency (δ> 0). This oxygen deficiency means that electrons are introduced into the crystal, resulting in an n-type semiconductor.
When M1 is Co, it is preferable that 0 <x ≦ 0.5.

(Second Embodiment)
The present embodiment relates to the case where the composition of the p-type semiconductor layer of the light-emitting diode is represented by the chemical formula: (AE _1-y RE _y ) ₂ M ₂ O ₄ . In this embodiment, (Sr _1-y La _y ) ₂ RhO ₄ will be described as an example.

[Preparation of target]
As in the first embodiment, a target for producing an oxide thin film was produced.
In the (Sr _1-y La _y ) ₂ RhO ₄ system, La ₂ O ₃ , SrCO ₃ , Rh ₂ O ₃ are used as raw materials, and the stoichiometric composition is (Sr _1-y La _y ) ₂ RhO _4. And uniformly mixed by wet mixing using alcohol or dry mixing in an agate mortar. After mixing, calcination is performed in the atmosphere at 900 ° C. for 8 to 12 hours. Then, it grind | pulverizes and mixes, It shape | molds by a press at 20 mm in diameter and a cylindrical shape with a thickness of about 5 mm, and baking is performed in oxygen atmosphere for 8 to 10 hours between the temperature of 1000 to 1200 degree | times. This is a pulse laser target.

[Preparation of thin film]
In the present embodiment, as in the first embodiment, an SrTiO ₃ (001) single-side polished single crystal substrate was used as the solid substrate.
The target material was a (Sr _0.75 La _0.25 ) ₂ RhO ₄ polycrystal having a stoichiometric composition. This corresponds to y = 0.25. The distance between the target and the solid substrate was 28-35 mm, and the solid substrate was heated to 400-700 ° C. by a lamp heater. The laser irradiation frequency is 4-16 Hz, and the laser energy is about 20-50 mJ. A typical film formation time is 15 to 60 minutes, and a film thickness is 100 to 400 nm.

[Analysis of thin film]
As a result of the X-ray crystal diffraction experiment, it was found that the crystals were oriented in the (001) direction, and it was confirmed that the single-phase target composition could be produced as a thin film. Furthermore, as a result of reflection high-energy electron diffraction RHEED observation, a streak-like diffraction pattern was observed, and it was found that the outermost surface of the thin film had crystallinity. As a result, it was found that the produced thin film was an epitaxial thin film.
When a laminated device is used, the thin film used for the lower layer causes an electrical micro short if the surface structure is not flat. As a result of observing the surface morphology (irregular structure) with an atomic force microscope (AFM), it was confirmed that the surface roughness was 10 nm or less, and a thin film having a very flat surface structure was obtained. It was.

[Hall coefficient of thin film]
The (Sr _0.75 La _0.25 ) ₂ RhO ₄ thin film prepared at an oxygen atmosphere of 400 mTorr, 100 mTorr, 40 mTorr, and 10 mTorr at a substrate temperature of 540 ° C. was subjected to the Hall coefficient at room temperature in the same manner as in the first embodiment. It was measured. As a result, in the case of an oxide thin film produced at any oxygen pressure, it was impossible to determine whether the carrier was a hole or an electron. The oxygen content of the target material is presumed that there is no oxygen deficiency because sufficient heat treatment is performed. Therefore, it is assumed that oxygen vacancies occur during the film formation process, and electrons and holes are mixed, making it difficult to discriminate carriers.

[Heat treatment]
The sample in which the carrier could not be discriminated was subjected to a heat treatment, and an attempt was made to introduce oxygen into the thin film crystal. The conditions for the heat treatment are a temperature of 500 ° C. to 1000 ° C., a constant temperature, and a holding time of 2 hours or more in the atmosphere. The results of Hall coefficient measurement of samples performed in the atmosphere at a heat treatment temperature of 800 ° C. and a holding time of 2 hours are 2.71 Ωcm, 1.02 × 10 ²⁰ cm ⁻³ ,. It was found to be 02 cm ² / Vs, and the carrier was a hole and a p-type semiconductor.

In (AE _1-y RE _y ) ₂ RhO ₄ , when y = 0, AE (Sr, etc.) is 2 + -valent, Rh is 4 + -valent, and oxygen 2-valence satisfies the electrical neutral condition. When y = 0.5, AE (Sr, etc.) 2+ valence, RE (La, etc.) is 3+ valence, oxygen 2-valence, and Rh is 3+ valence to satisfy the electrical neutral condition. . When Rh has a valence of 4+, Rh does not exhibit p-type due to its electron configuration, and 3+ valence appears to some extent, thus exhibiting p-type semiconductor characteristics.
Since it is difficult to synthesize a single phase when y exceeds 0.5, 0 <y ≦ 0.5 is preferable when M2 is Rh.

(Third embodiment)
This embodiment relates to a case where the composition of the p-type semiconductor layer of the light-emitting diode is represented by the chemical formula: (RE _1-x AE _x ) M ₁ O ₃ . In the present embodiment, La _1-x Sr _x RhO ₃ will be described as an example.

[Preparation of target]
As in the first embodiment, a target for producing an oxide thin film was produced.
In La _1-x Sr _x RhO ₃ , SrCO ₃ , La ₂ O ₃ , and Rh ₂ O ₃ are used as raw materials, and they are weighed so as to become La _1-x Sr _x RhO ₃ in a stoichiometric composition, and then in an agate mortar. And uniformly mixing by wet mixing using alcohol or dry mixing. After mixing is completed, calcination is performed in the atmosphere at a temperature of 900 degrees for 8 to 12 hours. Then, it grind | pulverizes and mixes, It shape | molds with a press at 20 mm in diameter and a cylindrical shape about 5 mm in thickness, and this baking is performed in oxygen atmosphere at the temperature of 1000 to 1200 degree | times for 8 to 10 hours. This is a pulse laser target.

[Preparation of thin film]
In the present embodiment, as in the first embodiment, an SrTiO ₃ (001) single-side polished single crystal substrate was used as the solid substrate.
As the target material, a La _0.8 Sr _0.2 RhO ₃ polycrystal having a stoichiometric composition was used. La _0.8 Sr _0.2 RhO _{3 was} also formed as a typical film forming condition under an oxygen pressure of 10 mTorr to 400 mTorr. However, as a result of measuring the Hall coefficient for the thin film under any oxygen pressure condition, p-type semiconductor characteristics were not shown.

[Heat treatment]
A sample thin film that did not exhibit p-type semiconductor characteristics was subjected to a heat treatment in the same manner as in the second embodiment to try to introduce oxygen. The conditions for the heat treatment are a temperature of 500 ° C. to 1000 ° C. and a constant temperature holding time of 2 hours or more in the atmosphere. As a result of measuring the Hall coefficient of the sample conducted in the air at a heat treatment temperature of 800 ° C. and a holding time of 2 hours, the resistivity, carrier concentration, and mobility were 4.76 × 10 ¹ Ωcm and 3.42 × 10 ¹⁹ cm ⁻ , respectively. ³ and 0.04 cm ² / Vs, and it was found that the carrier was a hole and a p-type semiconductor.

  Also in the present embodiment, as in the first embodiment, when M1 is Rh, it is more preferable that 0 <x ≦ 0.5.

(Fourth embodiment)
This embodiment relates to a case where the composition of the p-type semiconductor layer of the light-emitting diode is represented by the chemical formula: (RE _1-x AE _x ) M ₁ O ₃ . In the present embodiment, Sr-added LaMnO ₃ will be described as an example.
As in the first embodiment, La _0.85 Sr _0.15 MnO ₃ was formed by pulse laser deposition. With La _0.85 Sr _0.15 MnO ₃ , film formation was performed under typical film formation conditions at an oxygen pressure of 100 mTorr and a substrate temperature of 540 ° C. As a result of measuring the Hall coefficient, the specific resistance, carrier concentration, and mobility are 2.62 × 10 ⁻¹ Ωcm, 4.61 × 10 ²⁰ cm ⁻³ , and 0.05 cm ² / Vs, respectively. It was found to be a type semiconductor.

With respect to Sr-added LaMnO ₃ , the amount of Sr added was examined.
La _0.67 Sr _0.33 MnO ₃ having a relatively large Sr addition amount is shown as a comparative example. La _0.67 Sr _0.33 MnO ₃ was used as a typical film forming condition, and was formed at the same oxygen pressure of 100 mTorr and substrate temperature of 540 ° C. as La _0.85 Sr _0.15 MnO ₃ described above. It was. As a result of measuring the Hall coefficient, the specific resistance, carrier concentration, and mobility are 5.77 × 10 ⁻³ Ωcm, 9.00 × 10 ²⁰ cm ⁻³ , and 1.20 cm ² / Vs, respectively, and the carriers are electrons and n It was found to be a type semiconductor. Even when the film was formed at an oxygen pressure of 10 mTorr to 400 mTorr, the carriers were electrons and an n-type semiconductor. Since oxygen deficiency has occurred, it was assumed that it was dominated by n-type, and heat treatment was performed. The conditions for the heat treatment are a temperature of 800 ° C., a holding time of 2 hours, and in the air. Then, as a result of performing Hall coefficient measurement, the specific resistance, the carrier concentration, and the mobility are 4.90 × 10 ⁻³ Ωcm, 5.41 × 10 ²⁰ cm ⁻³ , 2.35 cm ² / Vs, respectively, Was an electron and was found to be an n-type semiconductor. It was found that the La _0.67 Sr _0.33 MnO ₃ thin film with a relatively large amount of Sr addition could not be expected to introduce oxygen into the crystal by heat treatment, indicating an n-type semiconductor.

From these results, in the chemical formula: (RE _1-x AE _x ) M ₁ O ₃ , the n-type and the p-type can be made different by changing the substitution amount of AE, that is, by setting x. By setting x to a predetermined threshold value or less, a p-type can be manufactured.
Therefore, when M1 is Mn, a p-type semiconductor can be manufactured with x being less than 0.33, preferably 0.24 or less.

  The reason for becoming p-type or n-type depending on the ratio of AE (Sr, etc.) can be considered as in the case of Co described in the first embodiment. This is not limited to the elements of La, Sr, Co, Rh, and Mn, but is the same in the perovskite related oxide of the present invention.

(Fifth embodiment)
This embodiment relates to a case where the composition of the p-type semiconductor layer of the light-emitting diode is represented by the chemical formula: (RE _1-x AE _x ) M ₁ O ₃ . In the present embodiment, SrRuO ₃ will be described below as an example. This is an example in the case of x = 1.
Similar to the first embodiment, SrRuO ₃ was formed by pulse laser deposition. In SrRuO ₃ , film formation was performed at an oxygen pressure of 100 mTorr and a substrate temperature of 540 ° C. as typical film formation conditions. As a result of measuring the Hall coefficient, the specific resistance, carrier concentration, and mobility are 1.56 × 10 ³ Ωcm, 3.35 × 10 ²² cm ⁻³ , and 0.19 cm ² / Vs, respectively, and the carrier is a p-type hole. It turned out to be a semiconductor. Similar results were obtained even when the film was formed at an oxygen pressure of 10 mTorr to 400 mTorr.
In the present embodiment, when M1 is Ru, 0.9 <x ≦ 1 is more preferable.

(Sixth embodiment)
In this embodiment, a semiconductor element using the oxide semiconductor thin film which is a p-type semiconductor described in the above embodiment, which is a premise of a light-emitting diode, will be described. The oxide semiconductor thin film that is a p-type semiconductor has a perovskite-type related structure, and the composition is chemical formula: (RE _1-x AE _x ) M ₁ O ₃ or chemical formula: (AE _1-y RE _y ) ₂ M ₂ O ₄ , And an oxide represented by A semiconductor element including an oxide semiconductor thin film that is the p-type semiconductor and an n-type semiconductor thin film that is pn-junction to the thin film is manufactured as follows.

[Preparation of pn junction]
Fabrication of the pn junction used a pulsed laser deposition method that can have a multi-source target. A plurality of target materials can be continuously formed in one vacuum process. As the substrate material, an Nb1% substituted SrTiO ₃ (SrTi _0.99 Nb _0.01 O ₃ ) (001) single-side polished substrate having electrical conductivity was used. A p-La _0.67 Sr composed of a p-type semiconductor La _0.67 Sr _0.33 CoO ₃ , an insulating layer CeO ₂ , and an n-type semiconductor SrTi _0.99 Nb _0.01 O ₃ on the substrate. A junction structure of _0.33 CoO ₃ / CeO ₂ / n-SrTi _0.99 Nb _0.01 O ₃ was produced as follows.
First, evacuation and substrate heating are performed, the substrate is heated to a predetermined temperature of 400 to 700 ° C. and held for a predetermined time, and then oxygen is introduced into the vacuum chamber. The p-La _0.67 Sr _0.33 CoO ₃ target was irradiated with a laser to make the target material into plasma and deposited on a substrate held at a high temperature. Thereafter, similarly, an insulating layer CeO ₂ was continuously formed. Thereafter, n-SrTi _0.99 Nb _0.01 O ₃ was continuously formed on the insulating layer. As the SrTi _0.99 Nb _0.01 O ₃ target, a single crystal was used.
The produced Nb1% substituted SrTiO ₃ (SrTi _0.99 Nb _0.01 O ₃ ) (001) single-side polished substrate having electrical conductivity, p-La _0.67 Sr _0.33 CoO ₃ / CeO ₂ / the _{n-SrTi 0.99 Nb 0.01} O ₃ consisting of the pn junction multilayer structure was provided upper electrode. For the upper electrode, an Sb-substituted SnO ₂ film (ATO) or ITO film was used as the transparent conductive film. In addition, the above-mentioned film formation was performed using a mask material, and a surface type pn junction having a size of 0.5 mm to 1 mm square was manufactured.

[Current-voltage characteristics of pn junction]
A method for measuring the current-voltage of the pn junction will be described. FIG. 4 is a circuit diagram used for current-voltage measurement of a pn junction. An AC power supply having a resistance R _L (R _L = 200Ω in the figure), a resistance R (R = 600Ω), and a frequency f = 2.2 Hz is connected in series with the sample pn junction semiconductor element. A voltage applied to the sample is set to V _x through a buffer circuit having a predetermined input impedance Z _in (Z _in = about 10 ¹⁰ Ω). The sample voltage V _sample is (V _x −V _y ), which is input to the x axis of the current-voltage characteristic diagram. In addition, the current flowing through the sample is expressed as a current-voltage characteristic diagram _in which the voltage at both ends of the resistor R _L (R _L = 200Ω) is expressed as V _y through a buffer circuit having an input impedance Z _in (Z _in = about 10 ¹⁰ Ω). Input to the y-axis. The actual current value I _sample flowing through the _sample is I = V _y / _RL . During the measurement, a two-terminal prober was used. One terminal is electrically contacted with a Nb 1% substituted SrTiO ₃ (SrTi _0.99 Nb _0.01 O ₃ ) (001) single-side polished substrate having electrical conductivity, and the other terminal is connected to 0% on the substrate. Contact was made with a transparent conductive film having a size of 5 mm × 0.5 mm or 1 mm × 1 mm.

[P-La _0.67 Sr _0.33 CoO ₃ / CeO ₂ / n-SrTi _0.99 Nb _0.01 O ₃ / ATO]
FIG. 5 shows p-La _0.67 Sr _0.33 CoO ₃ / CeO ₂ / Nb 1% -substituted SrTiO ₃ (SrTi _0.99 Nb _0.01 O ₃ ) (001) fabricated on a single-side polished substrate. The current-voltage characteristic of a typical pn junction obtained with n-SrTi _0.99 Nb _0.01 O ₃ / ATO is shown. According to the figure, a rise in current was observed with a forward bias slightly lower than 1.0V. In reverse bias, no current breakdown was observed up to -2.5V, and an ideal rectifying action was obtained. The thickness of the insulating layer was made in the range of 10 nm to 300 nm and the characteristics were investigated, but no significant change was observed.

Similar current-voltage characteristics were obtained even when an insulating layer of a perovskite oxide such as CaSrTiO ₃ was used instead of CeO ₂ as the insulating layer. From this, it can be considered that the same current-voltage characteristics can be obtained without depending on the material used for the insulating layer.

Moreover, it can be expected that the same result can be obtained even when Sr _0.995 La _0.005 TiO ₃ is used instead of the n-SrTi _0.99 Nb _0.01 O ₃ as the n-type semiconductor.

[P-La _0.67 Sr _0.33 CoO ₃ / CaSrTiO ₃ / n-IGZO]
As the substrate material, an Nb1% substituted SrTiO ₃ (SrTi _0.99 Nb _0.01 O ₃ ) (001) single-side polished substrate having electrical conductivity was used. On top of the substrate, p-La _0.67 Sr _0.33 CoO ₃ / CaSrTiO ₃ / Ca composed of p-type semiconductor La _0.67 Sr _0.33 CoO ₃ , insulating layer CaSrTiO ₃ , and n-type semiconductor IGZO. A junction structure of n-IGZO was produced. The electrode structure and the like are the same as described above.

Here, n-IGZO will be described. InGaZnO ₄ was formed under typical film formation conditions with an oxygen pressure of 50 mTorr and a substrate temperature of 400 ° C. When the Hall coefficient of n-IGZO deposited on the substrate was measured, the specific resistance, carrier concentration, and mobility were 4.43 × 10 ⁻¹ Ωcm, 1.31 × 10 ¹⁸ cm ⁻³ , and 10. It was 8 cm ² / Vs, and the carrier was an electron and was found to be an n-type semiconductor. Even if the film is formed at an oxygen pressure of 10 mTorr to 400 mTorr, the same result is obtained.

FIG. 6 shows the current-voltage characteristics of a typical pn junction obtained in the case of p-La _0.67 Sr _0.33 CoO ₃ / CaSrTiO ₃ / n-IGZO. According to the figure, a rise in current was observed with a forward bias slightly lower than 1.0V. In addition, it was found that with reverse bias, no current breakdown was observed up to −2.5 V, and an ideal rectifying action was obtained. The thickness of the insulating layer was made in the range of 10 nm to 300 nm and the characteristics were investigated, but no significant change was observed.

Similar current-voltage characteristics were obtained even when an insulating layer of a non-perovskite oxide such as CeO ₂ was used as the insulating layer. From this, it can be considered that the same current-voltage characteristics can be obtained without depending on the material used for the insulating layer.

[P-La _0.9 Sr _0.1 CoO ₃ / CeO ₂ / n-IGZO]
As the substrate material, an Nb1% substituted SrTiO ₃ (SrTi _0.99 Nb _0.01 O ₃ ) (001) single-side polished substrate having electrical conductivity was used. On top of the substrate, p-La _0.9 Sr _0.1 CoO ₃ / CeO ₂ / P-type semiconductor La _0.9 Sr _0.1 CoO ₃ , insulating layer CeO ₂ , and n-type semiconductor IGZO is formed. A junction structure of n-IGZO was produced. The electrode structure and the like are the same as described above.
FIG. 7 shows the current-voltage characteristics of a typical pn junction obtained. According to the figure, a rise in current was observed with a forward bias in the vicinity of about 1.0V. In addition, with reverse bias, no current breakdown was observed up to -4.0V, indicating that an ideal rectifying action was obtained. The thickness of the insulating layer was made in the range of 25 nm to 300 nm and the characteristics were investigated, but no significant change was observed.

Similar current-voltage characteristics were obtained when an insulating layer of a perovskite oxide such as CaSrTiO ₃ was used instead of CeO ₂ as the insulating layer. From this, it can be considered that the same current-voltage characteristics can be obtained without depending on the material used for the insulating layer.

[P-La _0.8 Sr _0.2 RhO ₃ / CeO ₂ / n-IGZO]
As the substrate material, an Nb1% substituted SrTiO ₃ (SrTi _0.99 Nb _0.01 O ₃ ) (001) single-side polished substrate having electrical conductivity was used. On the top of the substrate, p-La _0.8 Sr _0.2 RhO ₃ / CeO ₂ / P-type semiconductor La _0.8 Sr _0.2 RhO ₃ , insulating layer CeO ₂ , and n-type semiconductor IGZO is formed. An n-IGZO junction structure was fabricated by the following method.
First, after La _0.8 Sr _0.2 RhO ₃ is formed by the above-described method by a pulse laser deposition method, heat treatment in the atmosphere is performed at 500 ° C. to 1000 ° C. As a result, oxygen deficient during film formation is supplied to form a p-type semiconductor whose main carriers are holes. Then, by the pulse laser deposition method, _similarly, forming a CeO 2 / n-IGZO. Thereafter, as the transparent conductive film, an Sb-substituted SnO ₂ film (ATO) or ITO film was formed as an upper electrode.
FIG. 8 shows current-voltage characteristics of a typical pn junction obtained. According to the figure, a rise in current was observed with a forward bias slightly lower than 1.0V. In addition, it was found that with reverse bias, no current breakdown was observed up to −2.5 V, and an ideal rectifying action was obtained. The thickness of the insulating layer was made in the range of 10 nm to 300 nm and the characteristics were investigated, but no significant change was observed.

Similar current-voltage characteristics were obtained even when an insulating layer of a perovskite oxide such as CaSrTiO ₃ was used as the insulating layer. From this, it can be considered that the same current-voltage characteristics can be obtained without depending on the material used for the insulating layer.

[P- (Sr _0.75 La _0.25 ) ₂ RhO ₄ / CeO ₂ / n-IGZO]
As the substrate material, an Nb1% substituted SrTiO ₃ (SrTi _0.99 Nb _0.01 O ₃ ) (001) single-side polished substrate having electrical conductivity was used. P- (Sr _0.75 La _0.25 ) ₂ made of p-type semiconductor (Sr _0.75 La _0.25 ) ₂ RhO ₄ , insulating layer CeO ₂ , and n-type semiconductor IGZO is formed on the substrate. A junction structure of RhO ₄ / CeO ₂ / n-IGZO was produced by the following method.
First, (Sr _0.75 La _0.25 ) ₂ RhO ₄ is formed into a film by the above-described method by a pulse laser deposition method, and then heat treatment in the atmosphere is performed at 500 ° C. to 1000 ° C. As a result, oxygen deficient during film formation is supplied to form a p-type semiconductor whose main carriers are holes. Then, by the pulse laser deposition method, _similarly, forming a CeO 2 / n-IGZO. Thereafter, an Sb-substituted SnO ₂ film (ATO) or ITO film was formed as a transparent conductive film to form an upper electrode.
FIG. 9 shows the current-voltage characteristics of a typical pn junction obtained. According to the figure, a rise in current was observed with a forward bias slightly lower than 1.0V. In addition, it was found that with reverse bias, no current breakdown was observed up to −2.5 V, and an ideal rectifying action was obtained. The thickness of the insulating layer was made in the range of 10 nm to 300 nm and the characteristics were investigated, but no significant change was observed.

Similar current-voltage characteristics were obtained even when an insulating layer of a perovskite oxide such as CaSrTiO ₃ was used as the insulating layer. From this, it can be considered that the same current-voltage characteristics can be obtained without depending on the material used for the insulating layer.

In this embodiment mode, an example has been described in which an Nb1% -substituted SrTiO ₃ (SrTi _0.99 Nb _0.01 O ₃ ) (001) single-side polished substrate having electrical conductivity is used as a substrate material, but SrTiO ₃ Even if an electrically conductive SrRuO ₃ thin film is formed on a (001) single crystal substrate and a p-type semiconductor thin film / insulating layer / n-type semiconductor thin film is formed thereon, p-type semiconductor characteristics can be obtained. The effect is obtained.

(Seventh embodiment)
This embodiment relates to a light-emitting diode using the oxide semiconductor thin film that is a p-type semiconductor described in the above-described embodiments. The p-type oxide semiconductor thin film in the light-emitting diode of this embodiment has a perovskite-type related structure, and the composition is represented by the chemical formula: (RE _1-x AE _x ) M ₁ O ₃ or the chemical formula: (AE _1-y RE _{y) 2} M2O _4, in an oxide represented. The light-emitting diode of this embodiment has a junction structure of a p-type oxide semiconductor thin film, a light-emitting layer (i-type), and an n-type semiconductor thin film. The light emission characteristics of the light emitting element having the junction structure were examined in the following structure examples.

[P-La _0.67 Sr _0.33 CoO ₃ / light emitting layer / n-IGZO]
As shown in FIG. 10B, a Nb1% substituted SrTiO ₃ (SrTi _0.99 Nb _0.01 O ₃ ) (001) single-side polished substrate having electrical conductivity is used as a substrate material, and an upper portion thereof is used. Pn junction composed of p-La _0.67 Sr _0.33 CoO ₃ / light-emitting layer (Pr—CaSrTiO ₃ ) / n-IGZO structure composed of a p-type semiconductor, an i-type light emitting layer, and an n-type semiconductor did. Thereafter, as a transparent conductive film, an Sb-substituted SnO ₂ film (ATO) or an ITO film was formed as an upper electrode. The obtained current-voltage characteristics were the same as in FIG. Remarkable rectification can be confirmed, the reverse withstand voltage is 2.5V or more, and the forward rising voltage is about 0.9V. That is, it was found that the band gap of p-La _0.67 Sr _0.33 CoO _{3 having} a small band gap was about 0.9 eV. The band gap value can be tuned in the range of about 0.8 eV to 2.4 eV by changing the Sr concentration of the p-type semiconductor material La _0.67 Sr _0.33 CoO ₃ (see Non-Patent Document 2). ).

A light-emitting characteristic was investigated by applying a DC voltage to the element shown in FIG. At this time, Pr _0.002 added (Ca _0.6 Sr _0.4 ) TiO ₃ was used for the light emitting layer. Since visual confirmation of light emission was not obtained with respect to voltage application, the applied voltage and the current value of the photomultiplier tube were plotted using a photomultiplier tube. The results are shown in FIG. When the applied voltage is around 6.5 V, the current value of the photomultiplier tube changes remarkably, and light emission occurs. Further, it can be seen that when the DC voltage is continuously applied, the current value of the photomultiplier tube increases and the emission intensity increases.
FIG. 11 shows a wavelength spectrum obtained when a direct current of 7 V is applied to the same element as in FIG. According to FIG. 11, the appearance of a remarkable peak can be confirmed at a wavelength of 612 nm. A wavelength of 612 nm is a wavelength corresponding to an energy transition from ¹ D ₂ to ³ H _{4 of} Pr ³⁺ ions contained in the crystal of the light emitting layer as an emission center, and this emission is red.

These results are experimental evidence of the world's first oxide thin film LED device emission. That is, the following can be understood. It is clear that the light emitting device of this embodiment is not a light emission process described by AC electroluminescence hot electrons in which light emission occurs when the applied voltage is displaced with respect to time. In the light emitting process in the device of this embodiment, energy is generated by recombination of electrons and holes, and the energy is transmitted to the light emission center (Pr ³⁺ ions in the crystal) of the light emitting layer, and the electrons are excited in an energy level. The This is because the energy released when stabilizing to the ground state thereafter is emitted as light emission.

  The light emission principle of the light emitting diode is as follows. When a forward voltage is applied to the p-type semiconductor layer / light-emitting layer / n-type semiconductor layer, electrons and holes move and current flows. When electrons and holes collide in the light emitting layer, they recombine. Generates energy when recombined. This energy excites the emission center of the light emitting layer in an energy level. That is, since recombination of carriers can be caused in the light emitting layer by sandwiching the light emitting layer between the p-type semiconductor and the n-type semiconductor, other p-type semiconductor layers, n-type semiconductor layers, and light-emitting layers can be used. Similar light emitting diode results can be obtained.

As described above, it is apparent that the semiconductor element having the junction structure of the p-type oxide semiconductor thin film, the light emitting layer, and the n-type semiconductor thin film of the present invention has excellent light emission characteristics and functions as a light emitting diode. The light-emitting diode of the present invention is also a result of realizing an oxide semiconductor thin film having a perovskite-type related structure having a mobility of 0.02 cm ² / Vs or more as a p-type semiconductor layer. -The characteristics can be improved by using an n-type semiconductor thin film.

  In addition, the example shown by the said embodiment etc. was described in order to make invention easy to understand, and is not limited to this form.

  The light-emitting diode of the present invention is industrially useful as a chemically stable and durable semiconductor device because an oxide semiconductor thin film having a perovskite-type related structure exhibits excellent mobility as a p-type semiconductor.

Claims (8)

a light-emitting diode comprising a p-type semiconductor layer, a light-emitting layer, and an n-type semiconductor layer;
The p-type semiconductor layer is
An oxide semiconductor thin film having a perovskite-type related structure and containing one or more elements of Co, Rh, Ru, Mn, and Ir, a rare earth element, and an alkaline earth metal element A light emitting diode. The p-type semiconductor layer is
It has a perovskite type related structure and the composition is
Chemical _{formula: (RE 1-x AE x} ) M1O 3, or _{(AE 1-y RE y)} 2 M2O 4
(However, RE is one of the rare earth elements (Sc, Y, lanthanoid (La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu)). AE is one or more of the alkaline earth metal elements Ca, Sr, Ba, M1, M2 are Co, Rh, Ru, Mn, Ir 1 or 2 or more elements, 0 <x ≦ 1, 0 <y ≦ 1)
The light emitting diode according to claim 1, wherein the light emitting diode is an oxide semiconductor thin film represented by the formula: 3. The light emitting diode according to claim 1, wherein mobility of the oxide semiconductor thin film is 0.02 cm ² / Vs or more.   3. The light emitting diode according to claim 1, wherein the rare earth element is La and the alkaline earth metal element is Sr.   The light emitting diode according to claim 1, wherein the n-type semiconductor layer is an oxide semiconductor thin film.   The light emitting diode according to claim 1, wherein the light emitting layer is an oxide thin film.   A method for manufacturing a light-emitting diode, comprising: forming a p-type semiconductor layer in a light-emitting diode by depositing an oxide thin film having a perovskite-type related structure in an oxygen atmosphere.   A method for manufacturing a light-emitting diode, comprising: forming a p-type semiconductor layer in a light-emitting diode by depositing an oxide thin film having a perovskite structure and then performing heat treatment in an oxygen atmosphere.

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