JP2008252142A - Light emitting element, manufacturing method thereof, and visible light-emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light emitting element with little use amount of a rare metal at the time of configuring a light emitting layer part, to be grown at a relatively low temperature, capable of achieving high luminance light emission in a blue light region and an ultraviolet ray region. <P>SOLUTION: The light emitting element 1 comprises a light emitting layer part having a p type clad layer 2, and active layer 33 and a n type clad layer 34 laminated in this order. The p type clad layer 2 comprises a p type Mg<SB>x</SB>Zn<SB>1-x</SB>O (wherein 0<x≤1) layer. The layer formation is carried out with a MOVPE method so as to obtain a p type Mg<SB>x</SB>Zn<SB>1-x</SB>O layer with preferable characteristics by effectively restraining generation of oxygen deficiency in a formed film. The light emitting layer part comprises an InGaN layer for forming a type II band lineup with respect to the p type Mg<SB>x</SB>Zn<SB>1-x</SB>O layer or an Mg<SB>x</SB>Zn<SB>1-x</SB>O layer for forming a type I band lineup layer (wherein 0<y<1, x>y). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a light emitting element using a semiconductor, in particular, a light emitting element suitable for blue light or ultraviolet light emission, a method for manufacturing the same, and a visible light emitting device using the ultraviolet light emitting element.

  A high-intensity light-emitting element that emits short-wavelength light in the blue light region has been demanded for a long time. Recently, such a light-emitting element has been realized by using an AlGaInN-based material. In addition, by combining with red or green high-luminance light-emitting elements, application to full-color light-emitting devices and display devices is also rapidly progressing.

  However, since AlGaInN-based materials are mainly composed of relatively rare metals Ga and In, it is difficult to avoid an increase in cost. Another significant problem is that the growth temperature is as high as 700 to 1000 ° C. and a considerable amount of energy is consumed during production. This is not desirable not only from the viewpoint of cost reduction, but also in the sense of going against the currents in recent years when discussions on energy conservation and global warming suppression are frustrating.

  An object of the present invention is to provide a light emitting device that uses a rare metal in the light emitting layer portion, can be grown at a relatively low temperature, and can emit light with high brightness in a blue light region and an ultraviolet region. A manufacturing method and a visible light emitting device using a semiconductor ultraviolet light emitting element are provided.

Means for Solving the Problems and Effects of the Invention

In order to solve the above problems, a first light emitting device of the present invention has a light emitting layer portion in which an n-type cladding layer, an active layer, and a p-type cladding layer are laminated in this order, and a p-type cladding. InGaN having a p-type Mg _x Zn _1-x O (where 0 <x ≦ 1) layer and an active layer forming a type II band lineup with the p-type Mg _x Zn _1-x O layer It is characterized by comprising a layer. The second light emitting device of the present invention has a light emitting layer portion in which an n-type cladding layer, an active layer, and a p-type cladding layer are laminated in this order, and the p-type cladding layer is p-type Mg _x Zn. _1-x O (provided that, 0 <x ≦ 1) consist layer, active layer, _Mg forms a band lineup type I between the p-type _{Mg x Zn 1-x} O layer y _{Zn 1-y} O It consists of a layer (however, 0 <y <1, x> y).

The method for manufacturing a light emitting device of the present invention is characterized in that a p-type Mg _x Zn _1-x O layer is formed by metal organic vapor phase epitaxy to manufacture the light emitting device of the present invention. To do.

  In light emitting materials in the blue or ultraviolet region, ZnO is considered as an alternative material candidate for AlGaInN. However, since ZnO-based oxide semiconductor materials tend to generate oxygen vacancies, they are inherently easily n-type conductive, and it is considered difficult to manufacture a material exhibiting p-type conductivity that is indispensable for constituting a light-emitting element. It had been. Even if it is assumed that p-type ZnO is obtained, the energy level at the upper end of the valence band of ZnO is relatively high, so that a barrier against p-type carriers can be formed at a sufficiently high height with respect to the active layer. In some cases, the luminous efficiency may be reduced.

Therefore, in the present invention, a composite oxide obtained by substituting a part of Zn in ZnO with Mg, that is, Mg _x Zn _1-x O (0 <x ≦ 1: or less, the composite oxide is abbreviated as MgZnO). However, this does not mean that Mg: Zn: O = 1: 1: 1) is used as the constituent material of the p-type cladding layer. In MgZnO, the inclusion of Mg increases the band gap energy Eg of the oxide in a manner that decreases the energy level Ev at the upper end of the valence band. Thereby, the barrier height against the p-type carrier between the active layer and the luminous efficiency can be increased.

In order to reliably achieve the above effects, it is desirable to keep the oxygen deficiency concentration in the p-type Mg _x Zn _1-x O layer to 10 pieces / cm ³ or less. For this purpose, it is effective to employ a metal organic vapor phase epitaxy (MOVPE) method as a vapor phase growth method for forming the p-type Mg _x Zn _1-x O layer. is there. Other vapor phase growth methods such as high frequency sputtering and molecular beam epitaxy (MBE) can suppress the generation of oxygen vacancies because the pressure of the growth atmosphere is as low as 10 ⁻⁴ to 10 ⁻² torr. It is very difficult, and it is practically impossible to form a p-type Mg _x Zn _1-x O layer. However, since the vapor phase growth method using the MOVPE method can freely change the oxygen partial pressure during growth, it is possible to effectively suppress the generation of oxygen desorption and consequently oxygen deficiency by raising the atmospheric pressure to some extent. . As a result, it becomes possible to realize a p-type Mg _x Zn _1-x O layer that has been impossible in the past, particularly a p-type Mg _x Zn _1-x O layer having an oxygen deficiency concentration of 10 / cm ³ or less. . The lower the oxygen deficiency concentration, the better (that is, it does not prevent it from becoming 0 / cm ³ ).

Japanese Patent Laid-Open No. 11-168262 discloses a two-dimensional array surface light emitting device using a light emitting layer portion made of the AlGaInN-based material, or a light emitting layer portion made of an oxide of Zn and Mg or a mixed crystal thereof. Is disclosed. In addition to an embodiment in which the light-emitting layer portion is used as a visible light emission source, the publication also discloses a full-color display in which the light-emitting layer portion is configured as an ultraviolet light-emitting portion and each color phosphor layer is excited and emitted by ultraviolet light. However, JP-A-11-168262, oxides of Zn and Mg, or a light emitting layer portion composed of the mixed crystal, only been described as formed by epitaxial growth on a substrate, p-type Mg _x configuration of the light emitting layer portion including a Zn _1-x O layer, and not been described or suggested regarding specific method for forming the p-type _{Mg x Zn 1-x} O layer.

Formation of the p-type Mg _x Zn _1-x O layer by the MOVPE method in an atmosphere having a pressure of 10 torr or more can effectively suppress the generation of oxygen vacancies during film formation, and has good characteristics. P-type Mg _x Zn _1-x O layer can be obtained. In this case, it is more desirable that the oxygen partial pressure (oxygen-containing molecules other than O ₂ be incorporated by converting the contained oxygen into O ₂ ) is 10 torr or more.

By using such a p-type Mg _x Zn _1-x O layer as a p-type cladding layer, a light emitting element capable of emitting light with high brightness in a blue light region or an ultraviolet region can be easily formed. In addition, since the p-type cladding layer does not contain a rare metal such as Ga or In as a main component, the amount of the rare metal used in the entire light emitting layer portion is reduced, and as a result, the light emitting element can be manufactured at low cost. In addition, since the Mg _x Zn _1-x O layer can be vapor-phase grown at a relatively low temperature, it is effective for energy saving.

In the first aspect of the present invention, a semiconductor in which the active layer forms a type II band lineup with the p-type Mg _x Zn _1-x O layer, specifically, an InGaN layer (hereinafter referred to as an InGaN active layer). It is said. Here, “the type II band lineup is formed between the active layer and the p-type Mg _x Zn _1-x O layer” means that, as shown in FIG. 8, the p-type cladding layer (p-type Mg _x Between the energy levels Ecp, Evp at the bottom of the conductor and the top of the valence band of the Zn _1-x O layer) and the energy levels Eci, Evi at the bottom of the conductor of the active layer and the top of the valence band as follows: This refers to a joint structure in which a large and small relationship is established.
Eci> Ecp (1)
Evi> Evp (2)

  In this structure, there is no particular barrier for forward diffusion of electrons (n-type carriers) from the active layer to the p-type cladding layer, but the reverse of holes (p-type carriers) from the active layer to the p-type cladding layer. Since a relatively high potential barrier is formed for diffusion, carrier recombination in the active layer is promoted, and high luminous efficiency can be realized.

In the second aspect of the present invention, the active layer forms a type I band lineup with the p-type Mg _x Zn _1-x O layer, specifically, a Mg _y Zn _1-y O layer. (However, 0 <y <1, x> y). “A type I band lineup is formed between the active layer and the p-type Mg _x Zn _1-x O layer” means that a p-type cladding layer (p-type Mg _x Zn _{1− 1 − x O} layer) of the conductor base and the valence band each energy level Ecp the upper end, Evp and, each energy level Eci conductors bottom and top of the valence band of the active layer, the following magnitude relationship between Evi Refers to a joint structure where:
Eci <Ecp (5)
Evi> Evp (6)

  In this structure, unlike the type II type band lineup shown in FIG. 8, a potential barrier also occurs with respect to forward diffusion of electrons (n-type carriers) from the active layer to the p-type cladding layer. If the material of the n-type cladding layer is selected so that the same type I band lineup as shown in FIG. 8 is formed between the active layer and the n-type cladding layer, the position of the active band and Quantum wells are formed at both upper ends of the valence band, and the confinement effect is enhanced for both electrons and holes. As a result, the promotion of carrier recombination and thus the improvement of luminous efficiency become more remarkable.

In order for Mg _x Zn _1-x O to be p-type, it is necessary to add an appropriate p-type dopant. As such a p-type dopant, one or more of N, Ga, Al, In, Li, Si, C, and Se can be used. Of these, the use of N is particularly effective in obtaining good p-type characteristics. Further, it is effective to use one or more of Ga, Al, In and Li, particularly Ga, as the metal element dopant. By co-adding these with N, good p-type characteristics can be obtained more reliably. Even when Ga, In, or the like is used, the amount of use is very small, so there is no problem of cost increase.

In order to secure sufficient light emission characteristics, the p-type carrier concentration in the p _- type Mg _x Zn _1-x O layer is 1 × 10 ¹⁶ / cm ³ to 8 × 10 ¹⁸ / cm ³ . It is good. If the p-type carrier concentration is less than 1 × 10 ¹⁶ / cm ³ , it may be difficult to obtain sufficient light emission luminance. On the other hand, when the p-type carrier concentration exceeds 8 × 10 ¹⁸ / cm ³ , the amount of p-type carriers injected into the active layer becomes excessive, and back diffusion into the p-type Mg _x Zn _1-x O layer occurs. Alternatively, the number of p-type carriers that do not contribute to light emission due to overcoming barriers and flowing into the n-type cladding layer may increase, leading to a decrease in light emission efficiency.

Next, the visible light emitting device of the present invention is a light emitting device of the present invention configured as a semiconductor ultraviolet light emitting device, that is, light emission in which an n-type cladding layer, an active layer, and a p-type cladding layer are laminated in this order. A semiconductor ultraviolet light emitting element having a layer portion and the p-type cladding layer being a p-type Mg _x Zn _1-x O (where 0 <x ≦ 1) layer, and ultraviolet irradiation from the semiconductor ultraviolet light emitting element. And a phosphor that emits visible light when received.

Conventionally, fluorescent lamps have been widely used as visible light emitting devices. However, fluorescent lamps have the following drawbacks.
-Since ultraviolet rays are generated using cathode discharge, the life is likely to be relatively early due to evaporation of the electrodes.
・ High voltage is required and power consumption is large.
-Extra peripheral circuits such as ballasts and starters are required.
• Mercury encapsulated in glass tubes is released as an ultraviolet radiation source when the lamp is discarded, and it is expected that it will be avoided in the future from the viewpoint of environmental protection.

  However, according to the visible light emitting device of the present invention, since a semiconductor light emitting element is used as an ultraviolet ray source, the deterioration with time is small and the life is long. Basically, continuous light emission is possible as long as there is an energization circuit for the light emitting element. Therefore, the circuit configuration can be simplified. Furthermore, no high voltage is required and the resistance loss is small, so that the power consumption is small. In addition, since environmentally undesirable substances such as mercury are not used, an ecologically clean light emitting device can be realized. If the light-emitting element of the present invention is used as a semiconductor ultraviolet light-emitting element, the cost is low and the ultraviolet light emission efficiency is high, so that further energy saving can be achieved.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 schematically shows a laminated structure of a main part of a light emitting device according to the present invention, in which a light emitting layer in which an n-type cladding layer 34, an active layer 33, and a p-type cladding layer 2 are laminated in this order. Has a part. The p-type cladding layer 2 is formed as a p-type Mg _x Zn _1-x O layer (0 <x ≦ 1: below, sometimes abbreviated as p-type MgZnO layer 2). The p-type MgZnO layer 2 contains a trace amount of, for example, one or more of N, Ga, Al, In, and Li as a p-type dopant. Further, as described above, the p-type carrier concentration is adjusted in the range of 1 × 10 ¹⁶ pieces / cm ³ to 8 × 10 ¹⁸ pieces / cm ³ , for example, about 10 ¹⁷ pieces / cm ³ to 10 ¹⁸ / cm ³ .

  FIG. 2 shows the crystal structure of MgZnO, which has a so-called wurtzite structure. In this structure, oxygen ion-filled surfaces and metal ion (Zn ions or Mg ions) -filled surfaces are alternately stacked in the c-axis direction. As shown in FIG. The c-axis is formed along the layer thickness direction. When oxygen ions are lost and vacancies are generated, oxygen vacancies are generated and electrons that are n-type carriers are generated. Therefore, if too many oxygen vacancies are formed, n-type carriers are increased and p-type conductivity is not exhibited. Therefore, how to suppress the generation of oxygen vacancies is important when forming a p-type MgZnO layer.

  As already described, the p-type MgZnO layer 2 is formed by the MOVPE method. The growth principle of the MOVPE method itself is known. During the vapor phase growth, the above-described p-type dopant is added. Then, by performing the vapor phase growth under an atmospheric pressure of 10 torr or more, as shown in FIG. 4, the release of oxygen ions is suppressed, and a good p-type MgZnO layer 2 with few oxygen vacancies can be obtained.

  The p-type MgZnO layer 2 is ideally formed as a single crystal layer by epitaxial growth as shown in FIG. 5A, but a structure in which the c-axis is oriented in the layer thickness direction can be obtained. For example, a relatively good luminous efficiency can be obtained even with a polycrystalline layer as shown in FIG. In the case of MgZnO, it can be said that such a structure is relatively easy to obtain, for example, by providing a thermal gradient in the thickness direction of the substrate on which layer growth is performed.

  Returning to FIG. 1, the active layer 33 having an appropriate band gap according to the required emission wavelength is used. For example, what is used for visible light emission has the band gap energy Eg (about 3.10-2.18 eV) which can be light-emitted in wavelength 400-570 nm. This is an emission wavelength band covering from purple to green, but particularly when used for blue emission, a band gap energy Eg (about 2.76 to 2.48 eV) that can be emitted at a wavelength of 450 to 500 nm is obtained. Choose what you have. Moreover, what uses the band gap energy Eg (about 4.43-3.10 eV) which can be light-emitted in wavelength 280-400 nm is selected as what is used for ultraviolet light emission.

The active layer 33 can be formed of, for example, a semiconductor that forms a type II band lineup with the p-type Mg _x Zn _1-x O layer 2. Such an active layer can be an InGaN layer (hereinafter referred to as an InGaN active layer) 3 as in the light emitting device 1 shown in FIG. 6 or the light emitting device 100 shown in FIG. Corresponds to such an embodiment).

As described above, in this structure, there is no particular barrier for forward diffusion of electrons (n-type carriers) from the active layer to the p-type cladding layer, but holes from the active layer to the p-type cladding layer (p-type). Since a relatively high potential barrier is formed for the reverse diffusion of carriers), carrier recombination in the active layer is promoted, and high luminous efficiency can be realized. In addition, when the mixed crystal ratio of InN is expressed as In _α Ga _1-α N, _α should be 0.34 ≦ α ≦ 0.47 when aiming for blue visible light emission, and when aiming for ultraviolet light emission. Is preferably 0 ≦ α ≦ 0.19.

In this case, it is desirable to use a semiconductor that forms a type I band lineup with the active layer as the n-type cladding layer. Such an active layer, for example, as in the light emitting device 100 shown in the light emitting element 1 or 7 shown in FIG. 6 may be an n-type _{AlGaN (Al β Ga 1-β} N) layer 4. “A type I band lineup is formed between the n-type cladding layer and the active layer” means that the energy levels Eci and Evi at the bottom of the conductor and the top of the valence band are shown in FIG. And a junction structure in which the following magnitude relationship is established between the bottom of the n-type cladding layer (n-type AlGaN layer 4) and the energy levels Ecn and Evn at the top of the valence band:
Eci <Ecn (3)
Evi> Evn (4)

  This creates a relatively high barrier against back diffusion of electrons from the n-type cladding layer to the active layer, and a quantum well is formed at the active layer position at the upper end of the valence band, thus confining holes. The effect is enhanced. This all contributes to the promotion of carrier recombination in the active layer and thus to the improvement of the luminous efficiency.

In the structure of FIG. 8, the effect of suppressing the reverse diffusion of holes from the active layer to the p-type cladding layer can be enhanced by increasing the energy barrier height (Evi-Evp) at the upper end of the valence band. For this purpose, it is effective to increase the MgO mixed crystal ratio of the p-type Mg _x Zn _1-x O layer 2 constituting the p-type cladding layer, that is, the value of x). The mixed crystal ratio x is determined so as not to cause excessive overflow of carriers to the p-type cladding layer according to the required current density. For example, when the InGaN layer 3 is used as the active layer, the mixed crystal ratio x is preferably about 0.05 to 0.2 for a light emitting diode and about 0.1 to 0.4 for a semiconductor laser light source.

  On the other hand, since the bottom of the conduction band is stepped down from the active layer toward the p-type cladding layer, electrons that have not contributed to the light emission recombination in the active layer flow into the p-type cladding layer having a high carrier concentration. , Due to Auger recombination and the like, it no longer contributes to light emission. Therefore, in order to increase the luminous efficiency, it is necessary that as many electrons as possible recombine with holes before flowing into the p-type cladding layer. For this purpose, it is effective to increase the thickness t of the active layer to a certain value (for example, 30 nm or more). As shown in FIG. 8B, when the thickness t of the active layer is too small, electrons that flow into the p-type cladding layer and do not contribute to light emission increase, leading to a decrease in light emission efficiency. On the other hand, increasing the thickness t of the active layer more than necessary causes a decrease in the carrier density in the active layer, leading to a decrease in the light emission efficiency. For example, the value is set to 2 μm or less.

  Further, in FIG. 8, as in the case where the InGaN active layer is used, Ecp> Evi, that is, the forbidden band overlaps between the p-type cladding layer and the active layer. This is advantageous in suppressing non-radiative recombination at the bonding interface.

Next, as shown in FIG. 1, the surface of the p-type Mg _x Zn _1-x O layer 2 opposite to the active layer (InGaN layer) 3 is protected from a conductive material or a semiconductor material. It can be covered by layer 35. Since MgZnO has the property of being easily deteriorated in performance due to reaction with moisture, it is difficult to provide the protective layer 35 as described above for the p-type Mg _x Zn _1-x O layer 2. This is extremely effective in preventing such problems.

As shown in FIG. 3, the p-type Mg _x Zn _1-x O layer has a structure in which the c-axis is oriented in the layer thickness direction, that is, oxygen ion filled layers and metal ion filled layers are alternately stacked in the layer thickness direction. It has a structured. In this case, in consideration of electrical neutral conditions, when one side of the layer is an exposed surface of the metal ion filled layer (hereinafter referred to as a metal ion filled surface), the other side is always exposed of the oxygen ion filled layer. It is a surface (hereinafter referred to as oxygen ion-filled surface). And it is the exposed surface side of this oxygen ion filled layer that is likely to cause a reaction due to moisture adsorption.

For example, as shown in FIG. 1, if the contact side with the active layer 33 is a metal ion filled surface, the opposite side is an oxygen ion filled surface, so it is effective to cover this with the protective layer 35 described above. Become. In this case, the protective layer 35 comes into contact with the p-type Mg _x Zn _1-x O layer 2 on the oxygen ion filled surface. On the other hand, if the contact side with the active layer 33 is an oxygen ion-filled surface, the opposite side is a metal ion-filled surface that is relatively inert to the reaction with moisture. In this case, the protective layer 35 can be omitted, but if the protective layer 35 is provided, an element structure with better weather resistance can be obtained.

In the light emitting device 1 of FIG. 6, the protective layer is a transparent conductive material layer 12. Providing the transparent conductive material layer 12, that is, a transparent protective layer made of a material, contributes to improving the light extraction efficiency when the p-type Mg _x Zn _1-x O layer 2 side is the light extraction surface. In this case, the transparent conductive material layer 12 can also be used as an electrode for light emission energization. In this way, unlike the case where a metal electrode is provided, the electrode itself can transmit light, so it is not necessary to actively form an electrode non-formation region for light extraction around the electrode, and light extraction The area of the electrode can be increased without reducing the efficiency. In addition, since it is not necessary to form a current diffusion layer, the element can be simplified.

Specific materials of the transparent conductive material layer 12 include In ₂ O ₃ : Sn (commonly referred to as tin-doped indium oxide: ITO) and SnO ₂ : Sb (commonly referred to as antimony-doped tin oxide: Nesa). Can be preferably used. ITO is excellent in electrical conductivity and can contribute to a reduction in device driving voltage. On the other hand, Nesa has the advantage that it is cheaper than ITO but is cheaper. Moreover, since heat resistance is high, it is effective also in the case where a high-temperature treatment process is required after forming the transparent conductive material layer 12. The ITO film can be manufactured by sputtering or vacuum deposition, and the nesa film can be manufactured by a CVD method. Further, the transparent conductive material layer 12 may be formed by a sol-gel method.

  More specifically, the light-emitting element 1 of FIG. 6 has the following structure. That is, a buffer layer 11 made of GaN is formed on a sapphire (single crystal alumina) substrate 10, on which an n-type AlGaN layer 4 as an n-type cladding layer and an InGaN layer as an active layer (hereinafter referred to as an InGaN active layer). 3) and the p-type MgZnO layer 2 as the p-type cladding layer are epitaxially grown in this order, whereby a light emitting layer portion having a double hetero structure is formed. Further, the surface of the p-type MgZnO layer 2 is covered with a transparent conductive material layer 12 made of, for example, ITO, while the n-type AlGaN layer 4 and the InGaN active layer 3 are partially removed and exposed n-type AlGaN layer 4. A metal electrode 13 is formed on the surface. Then, by applying current between the transparent conductive material layer 12 side and the metal electrode 13, light (blue light or ultraviolet light) from the light emitting layer portion is transmitted from the transparent conductive material layer 12 side or from the sapphire substrate 10 side. It is taken out. The metal electrode 13 (or the metal reflective layer 22 or the metal electrode 21 described later) can be made of a metal containing one or more of Au, Ni, Ti, or Be, such as an Au—Be alloy.

  Next, in the light emitting device 100 of FIG. 7, the protective layer is the p-type compound semiconductor layer 20. The p-type compound semiconductor layer 20 can also be used as a current diffusion layer. In this case, by forming the metal electrode 21 having a smaller area than the p-type compound semiconductor layer 20, the current from the electrode 21 can be diffused over the entire surface of the p-type MgZnO layer 2 while enabling light extraction from the periphery. As a result, the light extraction efficiency can be improved. In this case, the p-type compound semiconductor layer 20 needs to have sufficient translucency for light extraction. In the present embodiment, the p-type compound semiconductor layer 20 is a p-type AlGaN layer, and the metal electrode 21 is formed thereon. The other parts are the same as those of the light-emitting element 1 in FIG. 6, and thus the same reference numerals are given to common elements and detailed description thereof is omitted. In addition, when the p-type compound semiconductor layer 20 has sufficient conductivity, the metal electrode 21 can be omitted.

An example of the manufacturing method of the light emitting device 1 of FIG. 7 will be described with reference to FIG.
First, as shown in FIG. 9A, a GaN buffer layer 11 is formed on one main surface of a sapphire substrate 10, and then an n-type AlGaN layer (n-type cladding) layer 4 is further formed with a layer thickness of, for example, 50 nm. The InGaN (non-doped) active layer 3 is epitaxially grown with a layer thickness of, for example, 30 nm. These layers can be formed by a known MOVPE method or MBE method. In addition, in this specification, MBE refers to MOMBE in which a metal element component source is an organic metal and a nonmetal element component source is a solid, in addition to MBE in a narrow sense that both a metal element component source and a nonmetal element component source are solid. (Metal Organic Molecular Beam Epitaxy), gas source MBE in which the metal element component source is solid and the nonmetal element component source is gas, chemical beam epitaxy (CBE) in which the metal element component source is organic metal and the nonmetal element component source is gas (Chemical Beam pitaxy)) as a concept.

  Next, as shown in FIG. 9B, a p-type MgZnO layer (p-type cladding layer) 2 is epitaxially grown, for example, with a layer thickness of 100 nm. When a metal element dopant is used as the p-type dopant, the metal element dopant can be supplied in the form of an organic metal containing at least one alkyl group.

When the p-type MgZnO layer 2 is formed by the MOVPE method, the following can be used as the main raw material:
・ Oxygen source: NO ₂ etc .;
Zn source: dimethyl zinc (DMZn), diethyl zinc (DEZn), etc .;
Mg source: biscyclopentadienyl magnesium (Cp ₂ Mg), etc.

Moreover, the following can be used as a p-type dopant source;
-Li source: normal butyl lithium, etc .;
-Si source: silicon hydride such as monosilane;
C source: hydrocarbon (for example, alkyl containing one or more C);
Se source: hydrogen selenide and the like.

One or more of Al, Ga, and In can function as a good p-type dopant by co-addition with N. The following materials can be used:
-Al source; trimethylaluminum (TMAl), triethylaluminum (TEAl), etc .;
Ga source; trimethylgallium (TMGa), triethylgallium (TEGa), etc.
In source: trimethylindium (TMIn), triethylindium (TEIn), etc.
When N is used together with the metal element (Ga) as the p-type dopant, the gas serving as the N source is supplied together with the organic metal serving as the Ga source when performing vapor phase growth of the p-type MgZnO layer. For example, in this embodiment, NO ₂ used as an oxygen source functions as an N source.

  Vapor phase growth of the p-type MgZnO layer 2 by the MOVPE method is performed by raising the temperature in the growth furnace in which the substrate is arranged to, for example, 300 to 700 ° C., and feeding the above raw materials together with the carrier gas in a gaseous state. it can. As the carrier gas, for example, nitrogen gas or argon gas can be used.

In the example shown in FIG. 32, the p-type Mg _x Zn _1-x O layer 2 is formed on the main surface 111 of the substrate 110 disposed in the internal space 115a of the growth vessel 115 by the MOVPE method. The substrate 110 is in the state shown in FIG. 9A, and the main surface 111 is the surface of the active layer 3 in FIG. In this case, the oxygen source gas OQ is supplied to the internal space 115a from the oxygen source gas outlet 116a, and the metal-organic jet formed so that the distance to the main surface 111 is closer to the oxygen source gas outlet 116a. Supplying the organometallic MO as the Mg and / or Zn source from the outlet 117a provides the p-type Mg _x Zn _1-x O layer 2 with few oxygen vacancies (specifically, 10 pieces / cm ³ or less). Effective above. At this time, the molar concentration of the oxygen source (Group VI) gas OQ supplied to the growth vessel 115 is increased to about 2000 to 3000 times the molar concentration of the organometallic (Group II) MO (that is, the supply II / VI ratio is 2000). ˜3000) is more effective.

In the embodiment of FIG. 32, the substrate 110 is heated by the heater 118 built in the susceptor 119. Further, the opening of the oxygen source gas supply pipe 116 connected to the growth vessel 115 forms an oxygen source gas ejection port 116a. Furthermore, the tip of the organic metal supply pipe 117 that enters the growth vessel 115 is located near the upper surface of the main surface 111 on which the p-type Mg _x Zn _1-x O layer 2 is to be formed. A jet port 117 a is formed, and an organic metal gas is blown toward the main surface 111.

It is also effective to perform vapor phase growth while maintaining the pressure in the reaction vessel at 10 torr or more. As a result, the release of oxygen is suppressed, and an MgZnO layer having good p-type characteristics with few oxygen vacancies can be synthesized. In particular, when NO ₂ is used as an oxygen source, the dissociation of NO ₂ is prevented from proceeding rapidly by the above pressure setting, and the generation of oxygen deficiency can be more effectively suppressed.

  The higher the atmospheric pressure is, the higher the oxygen desorption suppression effect is. However, even at a pressure up to about 760 torr (1 atm), the effect is sufficiently remarkable. For example, if it is 760 torr or less, there is an advantage that the container seal structure can be relatively simple because the inside of the reaction vessel is at normal pressure or reduced pressure. On the other hand, when a pressure exceeding 760 torr is adopted, the inside of the container is pressurized, so a slightly stronger sealing structure is taken into consideration so that the gas inside does not leak out. However, the effect of suppressing oxygen withdrawal becomes more remarkable. In this case, the upper limit of the pressure should be set to an appropriate value (for example, about 7600 torr (10 atm)) in consideration of the balance between the apparatus cost and the achievable oxygen desorption suppression effect.

  When the p-type MgZnO layer 2 is thus formed, the substrate is taken out of the reaction vessel, and a transparent conductive material layer 12 is formed as shown in FIG. When an ITO film is used, it can be formed by high frequency sputtering or vacuum deposition. Then, as shown in FIG. 9D, a part of the p-type MgZnO layer 2 and the InGaN active layer 3 is removed by gas etching or the like to expose the n-type AlGaN layer 4, where a metal is formed by vacuum deposition or the like. By forming the electrode 13, the light-emitting element 1 shown in FIG. 6 is completed. In order to obtain an element of an appropriate size, after the step (c), the substrate is diced, and then the step (d) is performed on each diced substrate. In addition, steps such as bonding of lead wires for energization and resin molding continue until the final product is obtained, but since it is a common-sense matter, detailed description is omitted (the same applies to other embodiments below). In the case of the light emitting device 100 shown in FIG. 7, except that the p-type AlZn layer is further vapor-phase grown by the MOVPE method after the p-type MgZnO layer 2 and the metal electrode 21 is formed thereon. It can be manufactured by the same process as in FIG.

  Next, the protective layer of the p-type MgZnO layer 2 can be the metal layer 22 as in the light emitting element 101 shown in FIG. In this case, the metal layer 22 can also be used as a light reflection layer (hereinafter referred to as the metal reflection layer 22) when light is extracted from the n-type cladding layer 4 side. In this way, the light extraction efficiency can be further improved by reflecting the light traveling from the light emitting layer portion toward the p-type cladding layer 2 toward the n-type cladding layer (n-type AlGaN layer) 4. In this case, for example, by attaching an electrode to the n-type clad layer 4 side, the metal reflection layer (metal layer) 22 can naturally be used as an electrode for light-emission energization. In the light emitting device shown in FIG. 11, a metal electrode 23 that partially covers the surface of the n-type cladding layer 4 is formed in direct contact with the n-type cladding layer 4. Light is extracted from the periphery of the metal electrode 23. Further, unlike the light emitting elements 1 and 100 of FIG. 6 or FIG. 7, the sapphire substrate 10 is removed.

  FIG. 10 shows an example of the manufacturing process of the light emitting element 101. The steps (a) and (b) for forming the buffer layer 11 and the layers 4, 3, and 2 serving as the light emitting layer on the sapphire substrate 10 are the same as those in FIG. In FIG. 10C, a metal reflective layer 22 such as an Au layer is formed by vacuum deposition or the like instead of forming the ITO film. In FIG. 10D, the sapphire substrate 10 is removed. For example, when the GaN buffer layer 11 is used, the GaN buffer layer 11 is dissolved by irradiating the excimer laser from the back side of the sapphire substrate 10, and the sapphire substrate 10 can be easily peeled and removed. Step (c) and step (d) may be interchanged. Then, as shown in FIG. 11, the metal electrode 23 is formed on the back surface side of the n-type cladding layer 4 from which the sapphire substrate 10 has been removed by vacuum deposition or the like, and further diced to obtain the light emitting element 101. Note that the sapphire substrate 10 may be removed by dissolving a buffer layer or a release layer provided separately from the buffer layer by chemical etching or the like.

  Note that a current diffusion layer 24 (for example, an n-type AlGaN layer) may be inserted between the metal electrode 23 and the n-type AlGaN layer as in the light-emitting element 99 shown in FIG. Further, as in the light emitting element 98 shown in FIG. 13, a transparent conductive material layer 25 such as an ITO film may be formed instead of the metal electrode 23.

Next, the active layer can also be formed of a semiconductor that forms a type I band lineup with the p-type Mg _x Zn _1-x O layer. Specifically, such an active layer can be formed as a Mg _y Zn _1-y O layer (where 0 <y <1, x> y) (in the second embodiment of the present invention). Applicable).

As described above, in this structure, unlike the type II band lineup shown in FIG. 8, a potential barrier also occurs with respect to forward diffusion of electrons (n-type carriers) from the active layer to the p-type cladding layer. If the material of the n-type cladding layer is selected so that the same type I band lineup as shown in FIG. 8 is formed between the active layer and the n-type cladding layer, the position of the active band and Quantum wells are formed at both upper ends of the valence band, and the confinement effect is enhanced for both electrons and holes. As a result, the promotion of carrier recombination and thus the improvement of luminous efficiency become more remarkable. The material of the n-type cladding layer may be AlGaN as shown in FIG. 6, but if an n-type Mg _z Zn _1-z O layer (where 0 ≦ z <1) is used, all of the light emitting layer portion is formed. This layer can be composed of an MgZnO-based oxide material (hereinafter, such a light-emitting layer portion is referred to as a “total oxide light-emitting layer portion”), and thus it is necessary to use a rare metal such as Ga or In described above. Eliminates (excluding dopants), enabling significant cost savings. Here, if x = y, the potential barrier heights on both sides of the quantum well are equal.

  The thickness t of the active layer is set to, for example, 30 to 1000 nm so as not to cause a decrease in carrier density in the active layer and to increase the number of carriers passing through the active layer due to the tunnel effect. .

Mg _y Zn _1-y O consisting layer active layer: _{(hereinafter,} referred to as Mg y _{Zn 1-y} O active layer but includes the case of y = 0), the value of y, factors both for determining the band gap energy Eg Become. For example, when ultraviolet light having a wavelength of 280 to 400 nm is to be emitted, the range is selected in the range of 0 ≦ y ≦ 0.5. The height of the well barrier formed is preferably about 0.1 to 0.3 eV for a light emitting diode and about 0.25 to 0.5 eV for a semiconductor laser light source. This value can be determined by selecting the composition of the p-type Mg _x Zn _1-x O layer, the Mg _y Zn _1-y O active layer, and the n-type Mg _z Zn _1-z O, that is, the numerical values of x, y, and z. . Considering the formation of a quantum well structure, the active layer does not necessarily contain Mg (that is, ZnO can be used), but the p-type and n-type cladding layers must contain Mg.

FIG. 14 shows one specific example of the light-emitting element. In the light emitting element 102, an n-type Mg _z Zn _1-z O layer 54, an Mg _y Zn _1-y O active layer 53 as an n-type cladding layer, and a p-type Mg _x Zn _{1- 1} as a p-type cladding layer. _{The xO} layer 52 is epitaxially grown in this order to form a light emitting layer portion having a double hetero structure. Since the other structure is the same as that of the light-emitting element 1 in FIG. The light-emitting element 103 in FIG. 15 corresponds to the light-emitting element 99 in FIG. 12 in which the light-emitting layer portion is replaced with the above-described double hetero structure. Furthermore, the light-emitting element 104 in FIG. 16 corresponds to a light-emitting layer part of the light-emitting element 98 in FIG. 13 replaced with the above-described double hetero structure.

Note that the Mg _y Zn _1-y O active layer 53 and the n-type Mg _z Zn _1-z O layer 54 have the same composition (ie, y = z) only with different n-type carrier concentrations. A light-emitting element structure in which the junction is homojunction is also possible. In this case, the potential barrier has a single heterostructure that occurs only between the p-type Mg _x Zn _1-x O layer 52 and the Mg _y Zn _1-y O active layer 53 (z> y).

Hereinafter, an example of a manufacturing process of the light emitting element having the all oxide light emitting layer part will be described with reference to FIG. 18 taking the case of the light emitting element 104 of FIG. First, as shown in FIG. 18A, the GaN buffer layer 11 is epitaxially grown on the sapphire substrate 10, then the n-type Mg _z Zn _1-z O layer 54 (layer thickness, for example, 50 nm), Mg _y Zn _1-y. An O active layer 53 (layer thickness, for example, 30 nm) and a p-type Mg _x Zn _1-x O layer 52 (layer thickness, for example, 50 nm) are formed in this order (the formation order may be reversed). Epitaxial growth of each of these layers can be formed by the MOVPE method, similar to the light-emitting elements 1 and 100 shown in FIG. In the case of using the MOVPE method, the raw materials are the same, but the n-type Mg _z Zn _1-z O layer 54, the Mg _y Zn _1-y O active layer 53, and the p-type Mg _x Zn _1-x O layer 52 are all the same. There exists an advantage which can form continuously in the same reaction container using a raw material. On the other hand, in this configuration, in order to reduce the reactivity with the GaN buffer layer 11 and increase the lattice matching, it is desirable to perform the growth at a slightly lower temperature, for example, 300 to 400 ° C.

In this case, depending on the mixed crystal ratios x, y, and z, the flow rate ratio of the organic metal serving as the Mg source and the Zn source is controlled for each layer by a mass flow controller or the like. Further, when forming the Mg _y Zn _1-y O active layer 53 and the p-type Mg _x Zn _1-x O layer 52, in order to suppress the generation of oxygen vacancies, the same as already described with reference to FIG. It is desirable to adopt this method. On the other hand, when the n-type Mg _z Zn _1-z O layer 54 is formed, a method in which oxygen vacancies are positively generated to be n-type can be employed. It is more effective to lower the atmospheric pressure (for example, less than 10 torr) than when the Mg _y Zn _1-y O active layer 53 and the p-type Mg _x Zn _1-x O layer 52 are formed. Further, the layer formation may be performed by separately introducing an n-type dopant. Alternatively, the ratio of feed group II to group VI (feed II / VI ratio) may be increased.

For example, the following processes are possible as an example. First, an n-type Mg _z Zn _1-z O layer 54 having a thickness of 50 nm is formed at a temperature of about 300 ° C. under an atmospheric pressure of 5 torr by MOVPE using NO ₂ , DEZn, and Cp ₂ Mg. Next, the Mg _y Zn _1-y O active layer 53 is formed at an atmospheric pressure of 760 to 7600 torr and a temperature of about 300 ° C. Finally, for example, normal butyl lithium is introduced as a dopant gas to form a p-type Mg _x Zn _1-x O layer 52 having a thickness of 50 nm at a temperature of 300 to 400 ° C.

When the formation of the light emitting layer portion is completed in this way, the metal reflective layer 22 as a protective layer is formed on the p-type Mg _x Zn _1-x O layer 52 as shown in FIG. After the sapphire substrate 10 is peeled off as shown in (c), a transparent conductive material layer 25 (for example, an ITO film) as a protective layer is formed on the n-type Mg _z Zn _1-z O layer 54 side. These steps are the same as those already described. After that, as shown in FIG. 18D, the light emitting element 104 is obtained by dicing. As can be seen from this example, since both the p-type cladding layer and the n-type cladding layer are made of MgZnO, it can be said that it is desirable to cover the side that does not contact the active layer with the protective layer. In the case where the growth substrate such as the sapphire substrate is not peeled off and used as a part of the device as it is as in the light emitting element 102 shown in FIG. 14, the growth substrate also serves as a protective layer.

In the method described above, each of the layers 52 to 54 is heteroepitaxially grown by the MOVPE method as an MgZnO single crystal layer. Even a polycrystalline body layer oriented in the c-axis in the direction can exhibit good light emission characteristics. Therefore, each layer 52 to 54 is formed on a glass substrate 9 like a polycrystalline substrate or the light emitting element 105 shown in FIG. (In this embodiment, after forming the thin n-type ZnO buffer layer 8 on the glass substrate 9, the layers 52 to 54 constituting the light emitting layer portion are grown). For example, as shown in FIG. 28A, by using a low-temperature vapor phase growth method such as laser beam sputtering on the glass substrate 9, for example, the n-type ZnO buffer layer 8 and the respective layers 52 constituting the light emitting layer portion. After forming -54 and further forming the metal reflective layer 22, dicing is performed for element isolation. Then, as shown in FIG. 28 (b), by forming the n-type _Mg z _{Zn 1-z} O layer metal electrode 13 exposes a part of 54, the light emitting element 105 is obtained. The light emitting element 105 can extract the light from the light emitting layer portion including the reflected light from the metal reflection layer 22 through the glass substrate 9. In addition, as a method of forming each of the layers 52 to 54 as a c-axis alignment layer, a method using a sol-gel method is also possible.

In the embodiment described above, the p-type Mg _x Zn _1-x O layer, the active layer, and the n-type clad layer that form the light emitting layer portion are manufactured in the form of being sequentially stacked on the substrate. It is also possible to obtain a similar laminated structure by using a bonding technique. For example, a first portion and a second portion corresponding to a laminated structure of a p-type Mg _x Zn _1-x O layer, an active layer, and an n-type cladding layer divided into two on one side of the active layer are respectively substrates. Individually formed on the top, the first part and the second part are bonded together. FIG. 19 shows a specific example. As shown in FIG. 19A, the first part PP includes a p-type Mg _x Zn _1-x O layer 2. In this embodiment, the p-type Mg _x Zn _1-x O layer 2 is epitaxially grown on the sapphire substrate 10 via the GaN buffer layer 11. On the other hand, the second portion SP includes a stacked body of the active layer 53 and the n-type cladding layer 54. An n-type Mg _z Zn _1-z O layer 54 and an Mg _y Zn _1-y O active layer 53 are epitaxially grown on the sapphire substrate 10 via the GaN buffer layer 11. The first portion PP and the second portion SP are overlapped between the Mg _y Zn _1-y O active layer 53 and the p-type Mg _x Zn _1-x O layer 2 as shown in FIG. Bonding is performed by heat treatment at an appropriate temperature (for example, about 300 to 500 ° C.).

Hereinafter, application examples of the light-emitting element of the present invention will be described.
As already described, the light-emitting element of the present invention can be formed as a visible light-emitting element 200 as shown in FIG. 20A or as shown in FIG. 20B by selecting the band gap of the active layer. In addition, the ultraviolet light emitting element 201 may be used. FIG. 20 shows a transparent conductive film formed on the p-type cladding layer 202 side while reflecting the light generated in the active layers 203 and 203 ′ on the metal reflection layer 22 formed on the n-type cladding layer 204 side. Although it is made to take out from the material layer 25 side, the formation form of an electrode etc. and the extraction form of light are not limited to this of course, FIG.6, FIG.7, FIG.11, FIG.12, FIG. Needless to say, this is possible.

  Of course, when used as the visible light emitting element 200, it can be used for general display. In particular, by realizing high-luminance blue light emission, a high-performance, low-power consumption and compact full-color display or full-color LED display can be realized. Moreover, it can be used as a light source for optical fiber communication, a point light source for a photocoupler, etc., including the case where it is used as the ultraviolet light emitting element 201. The former has the advantage that the information transmission density can be drastically improved by enabling high-luminance short-wavelength light emission. The light emitting device of the present invention can also be used as a laser light source, but it is possible to constitute a small and light short wavelength laser emission unit, for example, by using it as a laser light source for optical recording, The recording density can be dramatically increased.

  In addition, by realizing an ultraviolet light emitting element using a semiconductor, it becomes possible to achieve overwhelming light weight, size reduction, energy saving, and longer life as compared with a conventional ultraviolet light source using electrode discharge.

  Further, as shown in FIG. 21, a semiconductor ultraviolet light emitting element having a light emitting layer portion 201m having a structure in which a p-type cladding layer 202, an active layer 203 ′, and an n-type cladding layer 204 are laminated in this order is a phosphor 210. By combining them, a new type of visible light emitting device can be realized. Specifically, the photoexcited phosphor 210 emits visible light upon receiving ultraviolet irradiation from the semiconductor ultraviolet light emitting element. This is basically the same as a fluorescent lamp, CRT (Cathode Ray Tube) or the like in principle, but there is a decisive difference in using a semiconductor light emitting element as an ultraviolet light source. The effects brought about by this have already been described in the section “Means for solving the problems and actions / effects”. Hereinafter, the specific embodiment will be described in more detail.

  First, as shown in FIG. 22, ultraviolet light from a semiconductor ultraviolet light emitting element (hereinafter also simply referred to as a light emitting element) 201 can be configured to irradiate a phosphor layer 210 formed on a substrate 209. . By using such a base 209, the shape of the light emitting portion of the apparatus can be freely selected according to the shape of the base 209, and there is an advantage that the appearance of the apparatus can be designed flexibly according to various purposes. For example, in the light emitting device 250 of FIG. 22, the base 209 and the phosphor layer 210 are both formed in a plane. This greatly contributes to space saving. For example, if the substrate 209 is formed in a thin plate shape and the phosphor layer 210 is formed on the substrate 209, the light emitting layer portion can be made very thin by nature. Therefore, as shown in FIG. It is possible to realize a light-emitting device 251 with high luminance by using a thickness of 10 mm or less or 5 mm or less; in some cases, the thickness can be reduced to about 1 mm. Further, depending on the application, a curved base 210 can be used as shown in FIG.

  The light-emitting devices 250, 251, and 252 shown in FIGS. 22, 24, and 25 are common except for the difference in shape, so that the light-emitting device 250 shown in FIG. This will be explained as a representative. First, a plurality of light emitting elements 201 are provided, and the corresponding phosphor layer 210 is caused to emit light by ultraviolet rays from each light emitting element 201. By doing in this way, there exists an advantage which can enlarge the light emission area of an apparatus easily. The light-emitting device 250 is configured as a lighting device that simultaneously emits light from corresponding phosphor layers by a plurality of light-emitting elements 210, and a large-area, thin, and long-life lighting device is realized.

  In the phosphor layer 210, the portions 210a corresponding to the plurality of light emitting elements 210 are integrally formed continuously in the lateral direction. In this way, the phosphor layer portion 210a is formed as a single phosphor layer. Since it can form collectively as 210, manufacture is easy. In this case, when the phosphor layer portion 210a is considered to be a portion covered with the light emitting element 210, the ultraviolet rays from the light emitting element 201 spread outward due to the distance relationship between the light emitting element 210 and the phosphor layer portion 210a. It is also possible to leak outside the layer portion 210a, and as a result, emit light in a wider area than the phosphor layer portion 210a. Accordingly, by appropriately adjusting the distance between the phosphor layer 210 and the light emitting element 201, even if there is a slight gap between the adjacent light emitting elements 201, 201, it is caused by the ultraviolet rays from the individual light emitting elements 201, 201. The visible light emitting regions of the phosphor layer 210 are connected to each other, and uniform light emission with less unevenness can be generated over the entire surface of the phosphor layer 210.

  In the light emitting device 250, the base is configured as a transparent substrate 209, and the phosphor layer 210 is formed on one surface of the transparent substrate 209. The light extraction surface of the light emitting element 201 is disposed so as to face the opposite surface (here, disposed in close contact), and the light emitting element 201 (semiconductor ultraviolet light) is disposed on the phosphor layer 210 via the transparent substrate 209. Ultraviolet rays from a light emitting element are irradiated. According to this configuration, the light emitting element 201 (semiconductor ultraviolet light emitting element) and the phosphor layer 210 can be distributed and arranged using both surfaces of the transparent substrate 209, so that the apparatus can be made compact and the configuration can be simplified. More effective above.

  The transparent substrate 209 can use a glass plate or a transparent plastic (for example, an acrylic resin). The light emitting element 201 can be disposed on the transparent substrate 209 by attaching the light extraction surface side with, for example, an adhesive. For example, when a glass plate is used, the light emitting layer portion of the light emitting element 201 is placed on the glass plate. It is also possible to grow it. When the visible light emitting regions of the phosphor layer 210 by the individual light emitting elements 201 and 201 are to be connected to each other, the thickness of the transparent substrate 209 can be adjusted so that the ultraviolet rays spread to such an extent that such a connection occurs. That's fine. On the contrary, the closer the light emitting element 201 is to the phosphor layer 210, the smaller the spread of ultraviolet rays, which is advantageous in the clearing of pixels and the like for use in a display device or the like to be described later.

  In the light emitting device 250 of FIG. 22, the surface of the phosphor layer 210 is covered with a transparent protective layer 211 made of transparent plastic or the like. The arrangement side of the light emitting element 201 of the transparent substrate 209 is covered with a case 212. In addition, as another method for generating uniform light emission with little unevenness, a configuration in which light is extracted through a light dispersion plate 212 as shown in FIG. In the present embodiment, a transparent protective layer 211 is provided between the phosphor layer 210 and the light dispersion plate 212.

In addition, as a material of the light emitter, any material may be used as long as it can emit ultraviolet light. For example, when it is desired to emit white light, a known phosphor material used in fluorescent lamps, for example, calcium halophosphate (3Ca ₃ (PO ₄ ) ₂ .CaFCl / Sb, Mn) can be used. By adjusting the amounts of Cl, Sb, and Mn, white light with various color temperatures can be obtained. In addition, if the light emission having a narrow width in the three wavelength regions of red, green, and blue (RGB) is combined, it is possible to realize illumination with better color rendering. In this case, phosphors of respective colors are mixed and used. Typical examples include Y ₂ O ₃ : Eu ³⁺ (R: center wavelength 611 nm), CeMgAl ₁₁ O ₁₉ : Tb ³⁺ (G: center wavelength). 543 nm), BaMg ₂ Al ₁₆ O ₂₇ : Eu ²⁺ (B: center wavelength 452 nm).

  Next, as shown in FIG. 26, phosphor layers (210R, 210G, 210B) corresponding to the respective light emitting elements 201 may be provided separately. This configuration can also be used in a lighting device, but is more important for application as a display device. In this case, the light emitting element 201 can individually control the ultraviolet light emission state, and a set (201 / 210R, 201 / 210G, 201 / 210B) with a phosphor layer corresponding to each light emitting element 201 is displayed as a display unit. A plurality of these are arranged along the surface DP (formed by the plate surface of the transparent substrate 209). FIG. 26B shows a case of color display, and the RGB phosphor layers 210R, 210G, and 210B are arranged so that the same color layers are not adjacent to each other. Then, the phosphor layers 210R, 210G, and 210B of each display unit can be used as pixels, and image display can be performed based on the combination of the light emission states.

This type of display device has various major advantages.
-Unlike CRT, plasma display, etc., it does not use filaments, electrodes, or electron guns as an ultraviolet source, so it has a long life, and its driving voltage is low, resulting in low power consumption.
・ Thinners can be made as thin as liquid crystal displays and are light-emitting, eliminating the need for a backlight. Furthermore, there is almost no problem with the viewing direction.
In the configuration using the all oxide type light emitting layer part (FIG. 16 and the like), MgZnO can be easily dissolved using a dilute acid or alkali, so that the light emitting layer part corresponding to the pixel can be easily patterned by chemical etching. . Therefore, a high-resolution display having fine pixels can be easily realized. Although it is possible to construct an LED display that uses the visible light emitting element 200 shown in FIG. 20A directly as a pixel without using a phosphor, a conventional oxide light emitting layer portion can be used. An LED display with a much smaller size and higher resolution than that of the device can be realized.

  The lighting device and the display device described above can be variously configured including a current-carrying wiring to the light-emitting element 201 to be used, but some examples will be shown below. FIG. 29 shows a thin illuminating device 260. The phosphor layer 10 is formed on the back surface side of a transparent plate 74 such as an acrylic plate, and the light emitting element 105 (glass substrate 9 shown in FIG. What was manufactured: The manufacturing method has already been described with reference to FIG. 28), and a plurality of adhesives are attached (the thickness of the light emitting layer is exaggerated and actually thinner). Then, on the electrodes 13 and 22 of each element 105, the wiring boards on which the conductive wirings 71 and 72 and the electrode terminals 13a and 22a are formed are overlaid and molded as a whole by the case 73 (in this embodiment, the wiring board). Is also used as part of the molding case 73). In the case 73, a connector 75 is formed in such a manner that the ends of the energization wirings 71 and 72 are taken out. By connecting a power source 76 here, each element 105 is energized.

  A DC power source can be used as the power source 76, but it can also be driven by a pulsating current obtained by rectifying the AC. Further, if a half-wave waveform is not a problem, the AC power source It is also possible to drive directly with.

  In addition, in the case of conventional fluorescent lamps, in order to add a dimming function, it is necessary to perform electrode insulation and AC phase control at the same time, making it difficult to avoid complicated circuit configurations. (There are some dimming by switching the series impedance, but it is very uneconomical.) However, according to the illuminating device 260 of the present invention, the light can be easily adjusted without using a complicated circuit configuration by changing the supply voltage to the light emitting element 105 or changing the average current by controlling the duty ratio. There is an advantage that can be performed.

  Next, FIG. 30 shows a lighting device 261 of a type in which the light emitting layer portions 53, 54 and 52 of the light emitting element 106 are grown on the glass substrate 209. The phosphor layer 210 and the transparent protective film 211 are formed on one surface of the glass substrate 209, and the pattern of the electrode layer 220 made of a transparent conductive material such as ITO is formed on the opposite side corresponding to the formation region of each light emitting element 106. Are formed using photolithography or the like. Then, for example, all oxide type light emitting layer portions 54, 53, and 52 are sequentially formed thereon via an appropriate buffer layer 221, and then patterned by chemical etching so that a part of each electrode layer 220 is exposed. Then, the light emitting layer portion of each element 106 is separated. Finally, if the metal reflective film 22 is formed on each of the light emitting layer portions and the necessary wiring portions 71 and 72 are provided, the lighting device 262 is completed.

  FIG. 31 shows a configuration example of the display device 262. On one surface of the glass substrate 209, RGB phosphor layers 210 </ b> R, 210 </ b> G, and 210 </ b> B constituting pixels are formed and covered with a transparent protective layer 211. On the other hand, on the opposite surface of the glass substrate 209, light emitting elements 106 similar to the illumination device 261 in FIG. 30 are formed at positions corresponding to the phosphor layers 210R, 210G, and 210B (see FIG. 30). The same code is given to the common part). Each light emitting element is energized and controlled by the control circuit 75 by an individual image control signal. In the present embodiment, as a very simple example, each light emitting element 106 is switched by the transistor 75a. However, when the luminance of the pixel is changed in gradation, the energization voltage of each light emitting element 106 is individually set. The control circuit 75 may be configured to control the above.

The conceptual diagram of the light emitting element of this invention. The schematic diagram which shows the crystal structure of MgZnO. The schematic diagram which shows the arrangement | sequence form of the metal ion and oxygen ion of a MgZnO layer. Explanatory drawing showing a mode that the oxygen detachment | desorption produced when forming a MgZnO layer is suppressed by atmospheric pressure. The schematic diagram which shows the example which forms a MgZnO layer as a single crystal layer and a c-axis oriented polycrystalline layer. The cross-sectional schematic diagram which shows 1st embodiment of the light emitting element which concerns on this invention. The cross-sectional schematic diagram which shows 2nd embodiment of the light emitting element which concerns on this invention. The band schematic diagram of the light emitting element using the junction structure of the type I type and type II type band lineup concerning the 1st of this invention. Explanatory drawing which shows an example of a manufacturing process of the light emitting element of FIG. Explanatory drawing which shows an example of a manufacturing process of the light emitting element of FIG. The cross-sectional schematic diagram which shows 3rd embodiment of the light emitting element which concerns on this invention. FIG. 12 is a schematic cross-sectional view illustrating a first modification of the light emitting element of FIG. 11. FIG. 12 is a schematic cross-sectional view illustrating a second modification of the light emitting element of FIG. 11. The cross-sectional schematic diagram which shows 4th embodiment of the light emitting element which concerns on this invention. The cross-sectional schematic diagram which similarly shows 5th embodiment. The cross-sectional schematic diagram which similarly shows 6th embodiment. The band schematic diagram of the light emitting element using the junction structure of the type I type | mold band lineup based on the 2nd of this invention. FIG. 17 is an explanatory diagram illustrating an example of a manufacturing process of the light-emitting element in FIG. 16. Process explanatory drawing which shows an example of the method of manufacturing the light emitting element of this invention by a bonding system. FIG. 6 is a diagram illustrating the operation of the light emitting element of the present invention. The principle explanatory drawing of the visible light light-emitting device of this invention. The cross-sectional schematic diagram which shows the 1st example which comprised the visible light light-emitting device of this invention as an illuminating device. The cross-sectional schematic diagram which similarly shows a 2nd example. The cross-sectional schematic diagram which similarly shows a 3rd example. The cross-sectional schematic diagram which similarly shows a 4th example. The principle explanatory drawing of the display apparatus using the visible light light-emitting device of this invention. The cross-sectional schematic diagram which shows 7th embodiment of the light emitting element which concerns on this invention. FIG. 29 is an explanatory diagram illustrating an example of a manufacturing process of the light-emitting element in FIG. 28. The cross-sectional schematic diagram which shows the 2nd example which comprised the visible light light-emitting device of this invention as an illuminating device. The cross-sectional schematic diagram which shows the 3rd example which comprised the visible light light-emitting device of this invention as an illuminating device. The schematic diagram which shows the 1st example which comprised the visible light light-emitting device of this invention as a display apparatus. The figure which shows notionally an example of the apparatus which forms a MgZnO layer by MOVPE method.

Explanation of symbols

1,98-106, 200, 201 Light-emitting element 2 p-type Mg _x Zn _1-x O layer (p-type cladding layer)
3 InGaN active layer 4 n-type AlGaN layer (n-type cladding layer)
10 Sapphire substrate 11 GaN buffer layer 12, 25 Transparent conductive material layer (protective layer)
13 Metal electrode 20, 24 p-type AlGaInN layer (protective layer: current spreading layer)
21 Metal electrode 22 Metal reflective layer (protective layer)
23 metal electrode 33 active layer 34 n-type clad layer 35 protective layer 52 p-type Mg _x Zn _1-x O layer (p-type clad layer)
53 Mg _y Zn _1-y O active layer 54 n-type Mg _z Zn _1-z O layer (n-type cladding layer)
202 p-type cladding layer 203, 203 ′ active layer 204 n-type cladding layer 209 transparent substrate (substrate)
210 Phosphor Layer 250-252, 260, 261 Visible Light Emitting Device (Lighting Device)
262 Visible light emitting device (display device)

Claims (29)

The n-type cladding layer, the active layer, and the p-type cladding layer have a light emitting layer portion laminated in this order, and the p-type cladding layer is p-type Mg _x Zn _1-x O (where 0 <x ≦ 1) A light emitting device comprising a layer, and wherein the active layer is an InGaN layer forming a type II band lineup with the p-type Mg _x Zn _1-x O layer. The n-type cladding layer, the active layer, and the p-type cladding layer have a light emitting layer portion laminated in this order, and the p-type cladding layer is p-type Mg _x Zn _1-x O (where 0 <x ≦ 1) layer, and the active layer is an Mg _y Zn _1-y O layer (where 0 <y <1) that forms a type I band lineup with the p-type Mg _x Zn _1-x O layer. , X> y). The light emitting device according to claim 2, wherein the n-type cladding layer is an n-type Mg _z Zn _1-z O layer (where 0 ≦ z <1). The p-type Mg _x Zn _1-x O layer contains N as a p-type dopant and one or more of Ga, Al, and In, respectively. The light emitting element according to item. 2. The surface of the p-type Mg _x Zn _1-x O layer opposite to the active layer is covered with a protective layer made of a conductive material or a semiconductor material. The light emitting element according to claim 4. The p-type Mg _x Zn _1-x O layer has a structure in which oxygen ion filling layers and metal ion filling layers are alternately stacked in the layer thickness direction, and the protective layer is in contact with the oxygen ion filling layer. The light emitting device according to claim 5, wherein   The light emitting device according to claim 5, wherein the protective layer is a transparent conductive material layer.   The light-emitting element according to claim 7, wherein the transparent conductive material layer is also used as an electrode for light emission energization.   The light emitting device according to claim 5, wherein the protective layer is a p-type compound semiconductor layer.   The light emitting device according to claim 9, wherein the p-type compound semiconductor layer is also used as a current diffusion layer.   The light emitting device according to claim 5, wherein the protective layer is a metal layer.   The light-emitting element according to claim 11, wherein the metal layer is also used as a light reflection layer when light is extracted from the n-type cladding layer side.   The light emitting element according to claim 11, wherein the metal layer is also used as an electrode for light emission energization.   The light emitting device according to any one of claims 1 to 13, wherein a semiconductor that constitutes the active layer is selected to have a bandgap energy that can emit light with visible light having a wavelength of 400 to 570 nm.   The light emitting device according to any one of claims 1 to 13, wherein a semiconductor that constitutes the active layer is selected to have a band gap energy capable of emitting light with an ultraviolet ray having a wavelength of 280 to 400 nm. 16. A method for manufacturing the light-emitting device according to claim 1, wherein the p-type Mg _x Zn _1-x O layer is formed by metal organic vapor phase epitaxy. A method for manufacturing a light emitting device.   The method of manufacturing a light emitting device according to claim 16, wherein the metal organic chemical vapor deposition method is performed in an atmosphere having a pressure of 10 torr or more. A metal element dopant is used as the p-type dopant, and the metal element dopant is supplied in the form of an organic metal containing at least one alkyl group when performing vapor phase growth of the p-type Mg _x Zn _1-x O layer. The method for manufacturing a light-emitting element according to claim 16 or 17, wherein:   The method of manufacturing a light emitting device according to claim 18, wherein the metal element dopant is one or more of Ga, Al, In, and Li. N is used together with a metal element dopant composed of one or more of Ga, Al, In and Li as a p-type dopant, and when performing vapor phase growth of the p-type Mg _x Zn _1-x O layer, N The method for manufacturing a light-emitting element according to claim 19, wherein a gas serving as a source is supplied together with an organic metal serving as a metal element dopant source. 21. The light emitting device according to claim 16, wherein the n-type cladding layer, the active layer, and the p-type Mg _x Zn _1-x O layer are sequentially stacked on a substrate. Production method.   16. A visible light emitting device comprising: a semiconductor ultraviolet light emitting device configured as the light emitting device according to claim 15; and a phosphor that emits visible light upon receiving ultraviolet irradiation from the semiconductor ultraviolet light emitting device.   23. The visible light emitting device according to claim 22, wherein the phosphor layer formed on the substrate is irradiated with ultraviolet rays from the semiconductor ultraviolet light emitting element.   24. The visible light emitting device according to claim 23, wherein a plurality of the semiconductor ultraviolet light emitting elements are provided, and the corresponding phosphor layer is caused to emit light by ultraviolet light from each semiconductor ultraviolet light emitting element.   25. The visible light emitting device according to claim 24, wherein the visible light emitting device is configured as a lighting device that simultaneously emits light from corresponding phosphor layers by the plurality of semiconductor ultraviolet light emitting elements.   26. The visible light emitting device according to claim 25, wherein the phosphor layers corresponding to the plurality of semiconductor ultraviolet light emitting elements are integrally formed continuously in the lateral direction.   A plurality of display units each consisting of a set of the semiconductor ultraviolet light emitting element whose ultraviolet light emission state can be individually controlled and a corresponding phosphor layer are arranged along the display surface, and the phosphor layer of each display unit is used as a pixel. 25. The visible light emitting device according to claim 24, wherein the visible light emitting device is configured as a display device that displays an image based on a combination of light emitting states of the pixels.   28. The visible light emitting device according to claim 24, wherein the substrate and the phosphor layer are formed in a planar manner.   The substrate is configured as a transparent substrate, and the phosphor layer is formed on one surface of the transparent substrate, while the light extraction surface of the semiconductor ultraviolet light-emitting element is disposed opposite to the surface opposite thereto, 29. The visible light emitting device according to any one of claims 22 to 28, wherein the phosphor layer is irradiated with ultraviolet rays from the semiconductor ultraviolet light emitting element through a transparent substrate.

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