JP2001237460A - Light-emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light-emitting element, in which ZnO is used as an active region which comprises a p-n junction composed of a total-oxide semiconductor heterostructure and which is used in an ultraviolet region and a visible region. SOLUTION: An n-type Zn0.8Mg0.2O layer 2 is formed on the (0001) plane of a sapphire substrate 1. An n-type ZnO layer 3 is formed selectively on the n-type Zn0.8Mg0.2O layer 2. A p-type Zn0.75Ni0.25O layer 4 is formed on the n-type ZnO layer 3. Ohmic electrodes 5, 6, which are composed selectively of Au, are formed on the exposed n-type Zn0.8Mg0.2O layer 2 and the exposed p-type Zn0.75Ni0.25O layer 4. As a result, the light-emitting element, in which the p-n junction by a double heterostructure can be formed and which is used in the ultraviolet region can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting device using an oxide semiconductor.

[0002]

2. Description of the Related Art As a material for an ultraviolet light emitting device currently in practical use, there is GaN which is a compound of gallium (hereinafter, referred to as Ga) and nitrogen (hereinafter, referred to as N).

Recently, as a material for an ultraviolet light emitting device,
Zinc oxide (hereinafter, referred to as ZnO), which is a compound of zinc (hereinafter, referred to as Zn) and oxygen (hereinafter, referred to as O), is expected.

[0004] ZnO is a direct transition type, has a band gap of about 3.37 eV and has a large exciton binding energy of 60 meV which does not dissociate even at room temperature in the near ultraviolet region, and emits room temperature exciton laser by optical pumping. It has also been reported. This is described, for example, in Z. K. Tang
et al. , Appl. Phys. Lett, Vo
l. 72, no. 25,22 June 1998-3
270 to 3272.

Recently, an ultraviolet LED (Light E) made of InGaN, which is a compound of Indium (hereinafter referred to as In), Ga and N, for application to the field of lighting.
Mitting Diode) and YAG ((YGd) ₃
A white light emitting LED using (AlGa) ₅ O ₁₂ : Ce) fluorescent material has been commercialized. This is described in, for example, Mukai et al., Applied Physics, Vol. 68, No. 2, (1999), p.
155 pages.

[0006]

In order to realize a light emitting device,
Although formation of a pn junction is indispensable, a light-emitting element using ZnO can easily obtain n-type conductivity but hardly obtain p-type conductivity.

The white light emitting LED emits yellow-green light by exciting a YAG fluorescent material with a blue LED, and emits white light in blue and yellow green in combination with the original blue light. Therefore, the luminous efficiency is not sufficient.

The present invention has been made to solve the above-mentioned problems, and it is an ultraviolet and visible light emitting device having a double heterostructure pn junction composed of an oxide semiconductor using ZnO as an active layer. The purpose is to provide.

Another object of the present invention is to provide a white light-emitting element having high luminous efficiency and low cost.

[0010]

The compositional formulas of elements and compounds are described below by using element symbols as follows.

That is, magnesium is Mg, cobalt is Co, lithium is Li, nickel is Ni, europium is Eu, erbium is Er, praseodymium is Pr, terbium is Tr, cerium is Ce, thulium is Tm, strontium is Sr, titanium is titanium. Is Ti, aluminum is A
1, argon is described as Ar, lanthanum as La, and niobium as Nb.

In order to achieve the above object, in a light emitting device of the present invention, a ZnO layer serving as an active layer is formed of one conductivity type ZnMg.
O layer and ZnNi of the opposite conductivity type to the ZnMgO layer
It is formed between the O layer.

As a result, ZnMgO serving as a buffer layer is formed.
The layer is made of ZnO (band gap about 3.37 eV) and Mg
O (band gap: about 7.7 eV)
The band gap is larger than that of O, n-type conductivity can be easily obtained, and the ZnNiO layer serving as a buffer layer is made of ZnO.
And a mixed crystal of NiO and a band gap of about 4.2 eV. Since the band gap is larger than that of ZnO and p-type conductivity can be easily obtained, a pn junction of a double hetero structure using ZnO as an active layer can be obtained. A light emitting element in the ultraviolet region can be realized.

Further, in the light emitting device of the present invention, the ZnO layer serving as an active layer is a one-conductivity type ZnMgO layer and the ZnM layer.
The gO layer is formed between the opposite conductive type NiO layer and the gO layer.

As a result, as described above, the ZnMgO layer serving as the buffer layer has a larger band gap than ZnO, so that n-type conductivity can be easily obtained. The NiO layer serving as the buffer layer has a band gap higher than that of ZnO. Since p-type conductivity can be obtained easily and easily, and a pn junction having a double heterostructure using ZnO as an active layer can be obtained, a light emitting element in an ultraviolet region can be realized.

Further, in the light emitting device of the present invention, the ZnO layer serving as an active layer is a one-conductivity-type ZnMgO layer and the ZnM layer.
The gO layer is formed between the opposite conductivity type ZnCoO layer and the gO layer.

As a result, ZnMgO serving as a buffer layer is formed.
As described above, the layer has a larger band gap than ZnO and can easily obtain n-type conductivity. The ZnCoO layer serving as a buffer layer is a mixed crystal of ZnO and CoO (band gap of about 4.7 eV). Since the band gap is larger than that of ZnO and p-type conductivity can be easily obtained, a pn junction having a double hetero structure using ZnO as an active layer can be obtained, and a light emitting element in an ultraviolet region can be realized.

Further, in the light emitting device of the present invention, the ZnO layer serving as an active layer is formed of one conductivity type ZnMgO layer and the ZnM layer.
It is formed between the gO layer and the CoO layer of the opposite conductivity type.

As a result, as described above, the ZnMgO layer serving as the buffer layer has a larger band gap than ZnO, so that n-type conductivity can be easily obtained. The CoO layer serving as the buffer layer has a band gap higher than that of ZnO. Since p-type conductivity can be obtained easily and easily, and a pn junction having a double heterostructure using ZnO as an active layer can be obtained, a light emitting element in an ultraviolet region can be realized.

Further, the light emitting device of the present invention uses a ZnO layer doped with a rare earth element as an active layer.

Thus, when an electric current is applied, the inner electron system of the rare earth element is excited by the energy of the inter-band transition in the ZnO layer serving as the active layer of the base semiconductor, and visible light is emitted according to the type of the rare earth element. can do.

Further, in the light emitting device of the present invention, the rare earth element is at least one of Eu, Pr, Er, Tb, Tm, and Ce.

Thus, for example, Er of the rare earth element is
The outer orbitals of 5S and 5P are completely filled with electrons, but the 4f orbitals of the inner shell are only partially occupied by electrons. When added to the semiconductor, they become trivalent ions, and f Since electrons in the shell are shielded by electrons in the outer 5S and 5P orbits, light can be emitted by transition in the f-shell electron system. Depending on the type of the rare earth element, Eu and Pr have red emission, Er and Tb have green emission, and Tm and Ce have blue emission transition.
By doping nO, the energy of the interband transition in ZnO is converted to the transition energy of rare earth, and a light emitting element of visible light can be formed.

Further, the light emitting device of the present invention comprises a first active layer which emits red light doped with at least one of Eu or Pr and a green light which is doped with at least one of Er or Tb, on the same substrate. A second active layer that emits light and a third active layer that emits blue light doped with at least one of Tm and Ce are formed, and the first active layer, the second active layer, The third active layer is formed from the same material.

Thus, Eu, Pr and Pr are formed on the same substrate surface.
, A green light-emitting region doped with Tb and Er, and a blue light-emitting region doped with Ce and Tm. The light emission output of each blue light can be controlled, and the light emission intensity can be controlled by applying different currents to the respective regions, so that an element that emits white light can be easily realized.

Further, in the light emitting device of the present invention, the same material may be used for ZnO, GaN, InGaN, AlInGa
It is made of one of N and AlGaN.

Thus, the Z formed on the same substrate surface
nO, GaN, InGaN, AlInGaN, AlGa
In an active layer having a bandgap larger than the visible region such as N, a region emitting red light doped with Eu and Pr, a region emitting green light doped with Tb and Er, and a blue region doped with Ce and Tm are provided. Each light-emitting area has a light-emitting area, and each light-emitting area can control the light-emission output of red, green, and blue by adjusting current, and the light-emission intensity is
Since control can be performed by supplying different currents to the respective regions, an element that emits white light can be easily realized.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a light emitting device of the present invention will be described in detail with reference to the drawings.

(Embodiment 1) FIG. 1 is a sectional view of a light emitting device according to a first embodiment of the present invention.

This structure corresponds to (000) of the sapphire substrate 1.
1) On the surface, n-type Zn_0.8Mg_0.2An O layer 2 is formed, and n
Type Zn_0.8Mg_0.2An active layer on a selected region of the O layer 2
Is formed on the n-type ZnO layer 3.
p-type Zn_0.75Ni_0.25An O layer 4 is formed and the exposed n
Type Zn_0.8Mg_0.2O-layer 2 and p-type Zn_0.75Ni
_0.25An ohmic electrode made of Au is formed on the O layer 4.
The poles 5 and 6 are formed.

Next, an example of a method for manufacturing the light emitting device according to the first embodiment will be described with reference to FIG.

First, as shown in FIG. 2A, an MBE (Molecu) is formed on the (0001) plane of the sapphire substrate 1.
lar Beam Epitaxy) device, n
The type Zn _0.8 Mg _0.2 O layer 2 is formed to a thickness of 150 nm,
The thickness of the nO layer 3 is set to 50 nm, and the p-type Zn _0.75 Ni _0.25 O
Layer 4 is grown continuously to a thickness of 150 nm.

Note that the growth of these oxide semiconductor layers is as follows.
According to the MBE method, a solid deposition source (K cell) of Zn, Mg, and Ni and a O ₂ radical ion source are used, and a solid deposition source (K cell) of Al is used as an n-type dopant and Li ₂ O is used as a p-type dopant. , Substrate temperature 600 ℃
I went in.

In this case, n-type Zn serving as an n-type buffer layer
The band gap of the _0.8 Mg _0.2 O layer 2 is about 3.67 eV,
The band gap of the p-type Zn _0.75 Ni _0.25 O layer 4 serving as the p-type buffer layer is about 3.48 eV, and the band gap of the n-type ZnO layer 3 serving as the active layer (about 3.37 eV).
A larger, double heterostructure pn junction is formed.

Here, the crystal structure of MgO or NiO is usually cubic, but when mixed with ZnO, if the composition ratio is about 0.3 or less, the same hexagonal crystal structure as the base ZnO is used. And the change in lattice constant is small. Therefore, good crystals can be obtained.

The ZnO layer serving as an active layer is difficult to obtain p-type conductivity. However, by forming a ZnNiO layer by forming a mixed crystal with NiO which can easily obtain p-type conductivity by doping with Li or the like. Mold conductivity can be obtained.

Next, as shown in FIG.
_0.75Ni_0.25A predetermined area on the surface of the O layer 4 is
Ar ion milling using Ar
With p-type Zn_0.75Ni_0.25O layer 4 and n-type ZnO layer
3 to etch n-type Zn _0.8Mg_0.2Partial table of O layer 2
Expose the surface.

Next, as shown in FIG. 2 (c), by using a lift-off method or the like, from the n-type Zn _0.8 Mg _{0 .2} O layer 2 and the p-type Zn _0.75 Ni _0.25 respectively Au on the O layer 4 The ohmic electrode 5 and the ohmic electrode 6 are formed to complete the light emitting device.

Next, FIG. 3 shows an emission spectrum of the light emitting device formed by this manufacturing method.

As shown in FIG. 3, the center wavelength is about 380n.
It can be seen that light is emitted in the ultraviolet region of m.

Further, since the double hetero structure was used, good external quantum efficiency of about 8% was obtained.

(Embodiment 2) FIG. 4 is a sectional view of a light emitting device according to a second embodiment of the present invention.

This structure corresponds to (000) of the sapphire substrate 1.
1) An n-type Zn _0.8 Mg _0.2 O layer 2 is formed on the surface,
An n-type ZnO layer 3 serving as an active layer is formed on a selected region of the type Zn _0.8 Mg _0.2 O layer 2, a p-type NiO layer 7 is formed on the n-type ZnO layer 3, and an exposed n-type Zn _0.8 M
Ohmic electrodes 5 and 6 made of Au are formed on the g _0.2 O layer 2 and the p-type NiO layer 7, respectively.

This is a structure in which the p-type Zn _0.75 Ni _0.25 O layer 4 serving as the p-type buffer layer of the first embodiment is replaced by the p-type NiO layer 7.

Here, the ordinary NiO layer is an oxide semiconductor having a band gap of about 4.2 eV and easily obtaining p-type conductivity by doping with Li or the like, and its crystal structure is cubic. If the MBE method or the like is used, epitaxial growth can be performed on the ZnO layer, and a pn junction having a double hetero structure can be easily formed.

Note that the growth of these oxide semiconductor layers is as follows.
By the MBE method as described in the first embodiment,
Using a solid deposition source (K cell) of Zn, Mg and Ni and an O ₂ radical ion source, Al, p as n-type dopant
Li ₂ O as solid type dopant (K
(Cell) at a substrate temperature of 600 ° C.

The light emitting device formed in the second embodiment showed an emission spectrum in the ultraviolet region similar to that shown in FIG.

(Embodiment 3) FIG. 5 is a sectional view of a light emitting device according to a third embodiment of the present invention.

This structure corresponds to (000) of the sapphire substrate 1.
1) An n-type Zn _0.8 Mg _0.2 O layer 2 is formed on the surface,
An n-type ZnO layer 3 serving as an active layer is formed on a selected region of the type Zn _0.8 Mg _0.2 O layer 2, and a p-type Zn _0.8 Co _0.2 O layer 8 is formed on the n-type ZnO layer 3 and exposed. N-type Zn _0.8 Mg _0.2 O layer 2 and p-type Zn _0.8 Co _0.2 O
On the layer 8, ohmic electrodes 5 each made of Au,
6 is formed.

This is because the p-type Zn _0.75 Ni _0.25 O layer 4 serving as the p-type buffer layer of the first embodiment is replaced with the p-type Zn _0.8 C
The structure is replaced by an o _0.2 O layer 8.

The Zn _0.8 Co _0.2 O layer 8 is a layer composed of a mixed crystal of ZnO and CoO having a band gap of about 4.7 eV, has a band gap of about 3.55 eV, and can be easily used as a double heterojunction layer. A pn junction of the structure can be formed.

That is, it is difficult to obtain p-type conductivity in the ZnO layer, but by forming a ZnCoO layer by forming a mixed crystal with CoO which can easily obtain p-type conductivity by doping with Li or the like, the p-type conductivity can be reduced. Can be obtained.

As in the case of the ZnNiO layer, Co
O usually has a cubic crystal structure, but when a mixed crystal with ZnO has a composition ratio of about 0.3 or less, the base Zn
Maintains the same hexagonal crystal structure as O, with little change in lattice constant. Therefore, good crystals can be obtained.

Note that the growth of these oxide semiconductor layers is as follows.
By the MBE method as described in the first embodiment,
Using a solid deposition source (K cell) of Zn, Mg and Co and an O ₂ radical ion source, Al, p as n-type dopant
Li ₂ O as solid type dopant (K
(Cell) at a substrate temperature of 600 ° C.

The light emitting device formed in the third embodiment exhibited an emission spectrum in the ultraviolet region similar to that shown in FIG.

(Embodiment 4) FIG. 6 is a sectional view of a light emitting device according to a fourth embodiment of the present invention.

This structure corresponds to (000) of the sapphire substrate 1.
1) An n-type Zn _0.8 Mg _0.2 O layer 2 is formed on the surface,
An n-type ZnO layer 3 serving as an active layer is formed on a selected region of the type Zn _0.8 Mg _0.2 O layer 2, a p-type CoO layer 9 is formed on the n-type ZnO layer 3, and a p-type CoO layer The ohmic electrodes 5 and 6 made of Au are formed on the N-type Zn _0.8 Mg _0.2 O layer 2 and on the exposed n-type Zn _0.8 Mg _0.2 O layer 2, respectively.

This is because the p-type Zn _0.75 Ni _0.25 O layer 4 serving as the p-type buffer layer of the first embodiment is replaced with the p-type CoO layer 9.
This is the structure replaced by.

The CoO layer has a band gap of about 4.7 eV.
Which can be used to form a pn junction of a double hetero structure.

That is, as in the case of NiO, CoO
Is an oxide semiconductor whose p-type conductivity can be easily obtained by doping with Li or the like, and its crystal structure is usually cubic, but it can be epitaxially grown on a ZnO layer by MBE or the like. It is.

Note that the growth of these oxide semiconductor layers is as follows.
By the MBE method as described in the first embodiment,
Using a solid deposition source (K cell) of Zn, Mg and Co and an O ₂ radical ion source, Al, p as n-type dopant
Li ₂ O as solid type dopant (K
(Cell) at a substrate temperature of 600 ° C.

The light emitting device formed in the fourth embodiment exhibited an emission spectrum in the ultraviolet region similar to that shown in FIG.

As described above, the case where the oxide semiconductor described in the first embodiment to the fourth embodiment uses the MBE method is described. However, other film formation methods such as a laser ablation method and a sputtering method are used. However, similar results were obtained.

Although the case where a sapphire substrate is used as the substrate has been described, another oxide substrate such as a SrTiO ₃ substrate or a MgO substrate may be used. In particular, SrTi
The O ₃ substrate includes an n-type conductive substrate doped with La or Nb. In this case, an electrode can be removed from the back surface of the substrate, so that the process is facilitated.

(Embodiment 5) FIG. 7 is a sectional view showing a light emitting device according to a fifth embodiment of the present invention.

This structure corresponds to (000) of the sapphire substrate 1.
1) An n-type Zn _0.8 Mg _0.2 O layer 2 is formed on the surface,
An Er-doped n-type ZnO layer 10 serving as an active layer is formed on a selected region of the type Zn _0.8 Mg _0.2 O layer 2, and a p-type Zn _0.75 Ni is formed on the Er-doped n-type ZnO active layer 10. _{A 0.25} O layer 4 is formed and the exposed n
On the p-type Zn _0.8 Mg _0.2 O layer 2 and p-type Zn _0.75 Ni
Ohmic electrodes 5 and 6 made of Au are formed on the _0.25 O layer 4 respectively.

This is a structure in which the n-type ZnO active layer 3 in the light-emitting element described in the first embodiment of the present invention is replaced with an n-type ZnO active layer 10 doped with rare earth element Er.

The film forming method according to the fifth embodiment is performed by using the MBE method as shown in FIG.
The Er doping method was performed using an Er solid deposition source (K cell).

In the rare earth element Er, the outer orbital of 5S or 5P is completely filled with electrons, but the 4f orbital of the inner shell is only partially occupied by electrons, and is added to the semiconductor. And trivalent ions, and the electrons in the 4f shell are shielded by the electrons in the outer 5S and 5P orbits.
Light can be emitted by the transition of the shell electron system. FIG. 8 shows this energy transition diagram. When a current is passed through this light emitting element,
The 4f shell electron system of Er is excited by the energy of the interband transition in the ZnO layer 3 which becomes the active layer of the host semiconductor having a higher energy, and the wavelength is about 545 nm.
Emit with green visible light.

FIG. 9 shows an emission spectrum of the light emitting device formed in the fifth embodiment.

In the fifth embodiment, the case where Er is doped as a rare earth element has been described. However, when other rare earth elements are doped, for example, Eu and Pr emit red light, and Tb emits green light similarly to Er. Ce or Tm can make a light-emitting element in the visible region of blue light emission.

Further, it goes without saying that the same effect can be obtained even if the active layer of the ZnO layer 3 shown in the second to fourth embodiments of the present invention is doped with a rare earth element.

Further, as the doping method of the rare earth element into the ZnO layer serving as the active layer, the case where the MBE method is used has been described. However, the same effect can be obtained by using, for example, the ion implantation method.

Further, as the light emitting element shown in the first to fifth embodiments, a light emitting diode (LED) has been described, but a laser diode (LD) has a similar effect. Needless to say.

(Embodiment 6) FIG. 10 is a sectional view of a light emitting device according to a sixth embodiment of the present invention.

This structure corresponds to (000) of the sapphire substrate 1.
1) An n-type Zn _0.8 Mg _0.2 O layer 2 is formed on the surface, and a predetermined region on the n-type Zn _0.8 Mg _0.2 O layer 2 is doped with a rare earth element Eu or Pr to form an n-type ZnO layer 11, T
n-type ZnO layer 12 doped with b or Er and C
An n-type ZnO layer 13 doped with e or Tm is formed, and a p-type ZnO layer is formed on each n-type ZnO layer serving as an active layer.
An n _0.75 Ni _0.25 O layer 4 is formed, and ohmic electrodes 14, 15, 16 made of Au are formed on each p-type Zn _0.75 Ni _0.25 O layer 4 on each n-type ZnO layer, and the exposed n An ohmic electrode 5 made of Au is formed on a type Zn _0.8 Mg _0.2 O layer 2.

Next, an example of a method for manufacturing a light emitting device according to the sixth embodiment will be described with reference to FIGS.

First, as shown in FIG. 11A, an n-type Zn _0.8 Mg _0.2 O layer 2 was formed on an (0001) plane of a sapphire The layer 3 is formed to a thickness of 50 nm, and p-type Zn _0.75 Ni _0.25
The O layer 4 is continuously grown to a thickness of 150 nm.

Here, the growth by the MBE method is performed by using a solid deposition source (K cell) of Zn, Mg and Ni and an O ₂ radical ion source in the same manner as described in the first embodiment.
Al as an n-type dopant and Li as a p-type dopant
_The substrate temperature was set at 600 ° C. by using a solid deposition source (K cell) of ₂ O.

Next, FIG. 11 (b), FIG. 11 (c), FIG.
1 (d), the photoresist film 17
a, 17b, and 17c are selectively formed on the p-type Zn _0.75 Ni _0.25 O layer 4 before ion implantation, respectively, as masks so that the peak concentration comes near the center of the active layer of the n-type ZnO layer 3. Eu in the case of FIG. 11B, and FIG.
In this case, Er is ion-implanted, and in FIG. 11D, Tm is ion-implanted. In this case, the implantation dose is about 5
× 10 ¹⁴ cm ^-2 is appropriate.

Next, as shown in FIG.
Annealing is performed for about 3 hours in an oxygen atmosphere at 00 ° C. to activate the ion-implanted layer.
Layer 11, Er-doped n-type ZnO layer 12, Tm
Is formed, respectively.

Next, as shown in FIG. 12F, using a resist mask or the like having an opening in a predetermined region on the substrate surface,
P-type Zn _0.75 Ni _0.25 O layer 4 on n-type ZnO layer 3 not doped with Eu, Er or Tm;
n-type Z not doped with u, Er or Tm
The nO layer 3 is etched by Ar ion milling to form an n-type Z
The n _0.8 Mg _0.2 O layer 2 is partially exposed.

Next, as shown in FIG.
Exposed n-type Zn_0.8Mg_0.2O layer 2
An ohmic electrode 5 made of Au is formed on
N-type ZnO layer 11 doped with Eu,
N-type ZnO layer 12 doped with Tm
Each p-type Zn on each ZnO layer of the ZnO layer 13_0.75Ni
_0.25The ohmic electrodes 14 and 1 made of Au are formed on the O layer 4.
5 and 16 are formed to complete the light emitting device.

This light emitting element structure has a structure in which a red light emitting region (Eu doped n-type ZnO layer 1) is formed on the same substrate.
1), a region that emits green light (a region of the n-type ZnO layer 12 doped with Er), and a region that emits blue light (T
The light-emitting output of each light-emitting region can be independently controlled by adjusting its current by the electrodes 14, 15, and 16. Thereby, a white light emitting element can be obtained.

FIG. 13 shows the emission spectrum of each region of the light emitting device formed by the above method, wherein red is about 615 nm, green is about 545 nm, and blue is about 45 nm.
It can be seen that light is emitted at 0 nm.

As described above, since the red light emitting region, the green light emitting region, and the blue light emitting region are respectively formed by using the active layers simultaneously formed on the same substrate, the number of process steps can be reduced. As a result, a white light-emitting element which has been improved can be obtained. Further, since no phosphor is used, the luminous efficiency is high.

As described above, in the description of the sixth embodiment, Eu is emitted as red light, Er is emitted as green light, and T is emitted as blue light.
Although the case where m is used has been described, other rare earth elements,
For example, Pr may be used for red light emission, Tb for green light emission, and Ce for blue light emission. Also, the case where the ZnO layer is used as the active layer has been described, but a GaN-based device, that is, GaN, InGaN, AlInGaN,
It goes without saying that the same is true even when an active layer such as AlGaN is used.

[0088]

According to the present invention, ZnO is used as an active layer,
By using a ZnMgO layer as an n-type buffer layer and a ZnNiO layer, a NiO layer, a ZnCoO layer, and a CoO layer as a p-type buffer layer, a pn junction of a double hetero structure using ZnO as an active layer is obtained, and light emission in the ultraviolet region is obtained. An element can be realized.

Further, Eu, Pr, Er, Tb, Tm, C
By doping a rare earth element such as e into the ZnO active layer, a light emitting device in the visible region such as red, green, and blue can be realized.

Also, the Z simultaneously formed on the same substrate
nO, GaN, InGaN, AlInGaN, AlGa
In the active layer having a band gap larger than the visible region such as N, a region emitting red light selectively doped with Eu, Pr, etc., a region emitting green light doped with Tb, Er, etc., and Ce, Tm A white light-emitting element with high luminous efficiency is realized by controlling the luminous output of each of red, green, and blue by using the electrodes provided in each luminous region to control the luminous output of blue. it can. In addition, the number of manufacturing steps is reduced, so that cost reduction and size reduction can be achieved.

[Brief description of the drawings]

FIG. 1 is a sectional view of a light emitting device showing a first embodiment of the present invention.

FIG. 2 is a process cross-sectional view of the method for manufacturing the light-emitting element according to the first embodiment of the present invention.

FIG. 3 is a diagram of an emission spectrum of the light-emitting element according to the first embodiment of the present invention.

FIG. 4 is a cross-sectional view of a light emitting device according to a second embodiment of the present invention.

FIG. 5 is a sectional view of a light emitting device showing a third embodiment of the present invention.

FIG. 6 is a sectional view of a light emitting device showing a fourth embodiment of the present invention.

FIG. 7 is a sectional view of a light emitting device according to a fifth embodiment of the present invention.

FIG. 8 is a diagram showing energy transition of a 4f shell electron system of Er.

FIG. 9 is a diagram of an emission spectrum of a light emitting device according to a fifth embodiment of the present invention.

FIG. 10 is a sectional view of a light emitting device showing a sixth embodiment of the present invention.

FIG. 11 is a process sectional view of a method for manufacturing a light emitting device according to a sixth embodiment of the present invention.

FIG. 12 is a process sectional view of a method for manufacturing a light emitting device according to a sixth embodiment of the present invention.

FIG. 13 is a diagram of an emission spectrum of a light emitting device according to a sixth embodiment of the present invention.

[Explanation of symbols]

Reference Signs List 1 sapphire substrate 2 n-type Zn _0.8 Mg _0.2 O layer 3 n-type ZnO layer 4 p-type Zn _0.75 Ni _0.25 O layer 5, 6, 14, 15, 16 ohmic electrode 7 p-type NiO layer 8 p-type Zn _0.8 Co _0.2 O Layer 9 p-type CoO layer 10 n-type ZnO layer doped with Er 11 n-type ZnO layer doped with Eu or Pr 12 n-type ZnO layer doped with Tb or Er 13 n-type ZnO layer 17a doped with Ce or Tm 17b, 17c Photoresist film

Claims (9)

[Claims] The ZnO layer serving as an active layer is made of one conductivity type Z
nMgO layer and Z of opposite conductivity type to the ZnMgO layer
A light emitting element formed between the nNiO layer and the light emitting element. 2. The method according to claim 1, wherein the ZnO layer serving as an active layer is made of one conductivity type ZO.
nMgO layer and Ng of the opposite conductivity type to the ZnMgO layer
A light-emitting element formed between the light-emitting element and an iO layer. 3. The method according to claim 1, wherein the ZnO layer serving as an active layer is made of one conductivity type ZN.
nMgO layer and Z of opposite conductivity type to the ZnMgO layer
A light-emitting element formed between the light-emitting element and an nCoO layer. 4. The method according to claim 1, wherein the ZnO layer serving as an active layer is made of one conductivity type ZO.
C of the opposite conductivity type to the nMgO layer and the ZnMgO layer
A light emitting element formed between the light emitting element and an oO layer. 5. A light emitting device comprising a ZnO layer doped with a rare earth element as an active layer. 6. The light emitting device according to claim 5, wherein the rare earth element comprises at least one of europium, praseodymium, erbium, terbium, thulium, and cerium. 7. The ZnO layer serving as an active layer is a layer doped with at least one rare earth element of europium, praseodymium, erbium, terbium, thulium, and cerium. A light-emitting element according to any one of the above. 8. A first active layer emitting red light doped with at least one of europium or praseodymium and a second active layer emitting green light doped with at least one of erbium or terbium on the same substrate. And a third active layer that emits blue light doped with at least one of thulium or cerium, and wherein the first active layer, the second active layer, and the third active layer A light-emitting element formed of the same material. 9. The same material may be made of ZnO, GaN, InG
9. The light emitting device according to claim 8, wherein the light emitting device is made of any one of aN, AlInGaN, and AlGaN.