JP2003046128A - Light-emitting element and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light-emitting element and a manufacturing method therefor capable of providing a high-quality light-emitting layer part comprising Mga Zn1-a O type oxide. SOLUTION: A manufacturing method is provided for a light-emitting element 1 in which a light-emitting layer part comprises an Mga Zn1-a O (where 0<=a<=1) type oxide. A buffer layer 11, where the contacting side to the light-emitting layer part is, at least, an Mga Zn1-a O type oxide layer, is grown on a substrate 10 on which the light-emitting layer part is grown. The Mga Zn1-a O type oxide has a wurtzite type crystal structure comprising a metal atom layer and an oxygen atom layer laminated alternately in the c-axis direction. The buffer layer 11 is grown as the one in which the c-axis of wurtzite type crystal structure is oriented in the layer thickness direction. When the buffer layer 11 is grown, the metal atom layer is formed on the substrate as a metal single atom layer using an atom layer epitaxial method, and then a remaining oxygen atom layer and the metal atom layer are grown.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a light emitting device using a semiconductor, particularly a light emitting device suitable for emitting blue light or ultraviolet light.

[0002]

2. Description of the Related Art There has been a long-felt demand for a high-intensity light-emitting device that emits light with a short wavelength in the blue light region.
Such a light emitting element is realized by using a GaInN-based material. In addition, application to a full-color light emitting device, a display device and the like is rapidly progressing by combining with a red or green high brightness light emitting element. However, since the AlGaInN-based material contains Ga and In, which are relatively rare metals, as main components, it is inevitable that the cost will increase. Moreover, the growth temperature is 700 to 100.
One of the big problems is that the temperature is as high as 0 ° C. and considerable energy is consumed during manufacturing. This is not desirable not only from the viewpoint of cost reduction, but also in the sense that it goes against the current trend in recent years when discussions on energy saving and global warming suppression are hot. Therefore, Japanese Patent Laid-Open No. 2001-44
In Japanese Patent Publication No. 500, a cheaper Z is formed on a sapphire substrate.
A light emitting device in which an nO-based compound semiconductor layer is heteroepitaxially grown has been proposed.

Incidentally, ZnO-based oxides are obtained by vapor phase growth in a vacuum atmosphere, but since bulk single crystal growth is difficult, heteroepitaxial growth using a different material substrate such as sapphire is adopted. . In order to form the above-described light emitting layer portion having good crystallinity, it is necessary to insert an appropriate buffer layer between the substrate and the light emitting layer portion. In the above-mentioned Japanese Patent Laid-Open No. 2001-44500, this buffer layer (contact layer) together with the subsequent light emitting layer is M
BE (Molecular Beam Epitaxy) method or MOVPE
(Metalorganic Vapor Phase Epitaxy) method is disclosed.

[0004]

However, MBE
According to the method, since the pressure of the growth atmosphere is low, it is not easy to suppress the generation of oxygen vacancies, and it is very difficult to form a ZnO-based oxide layer which is indispensable for forming a light emitting device. On the other hand, in the vapor phase growth method using the MOVPE method, since the oxygen partial pressure during growth can be freely changed, it is possible to suppress the release of oxygen and the occurrence of oxygen deficiency by raising the atmospheric pressure to some extent. However, in the normal continuous growth type MOVPE method, when a disorder such as a defect or displacement of atoms occurs, the disorder is not repaired and the layer growth of the next and subsequent layers is continued. It is not always possible to obtain a good quality buffer layer that determines
As a result, there is a problem in that it is difficult to obtain an element having good luminous efficiency.

An object of the present invention is to provide a method of manufacturing a light emitting device capable of realizing a high quality light emitting layer portion made of Mg _a Zn _1-a O type oxide, and a light emitting device which can be manufactured by the method. It is in.

[0006]

In order to solve the above problems, the method for manufacturing a light emitting device of the present invention comprises:
The light emitting layer portion is Mg _a Zn _1-a O (where 0 ≦ a ≦ 1)
In a method of manufacturing a light emitting device made of _a type oxide, a buffer layer having at least a Mg _a Zn _1-a O type oxide layer on _a side in contact with a light emitting layer is grown on a substrate, and the light emitting layer is formed on the buffer layer. Part of the Mg _a Zn
_{The 1-a} O-type oxide has a wurtzite crystal structure composed of metal atomic layers and oxygen atomic layers that are alternately stacked in the c-axis direction, and the buffer layer has the wurtzite crystalline structure. C) with the c-axis oriented in the layer thickness direction, and at the time of growing the buffer layer, after forming the metal atomic layer as a metal monoatomic layer on the substrate using the atomic layer epitaxy method. The remaining oxygen atomic layer and the metal atomic layer are grown.

Further, the light emitting device of the present invention has a structure in which M
A light emitting device having a light emitting layer portion formed of an oxide of g _a Zn _1-a O (where 0 ≦ a ≦ 1) type oxide, wherein the light emitting layer portion is provided between the substrate and the light emitting layer portion. A buffer layer having _a contact side with at least a Mg _a Zn _1-a O type oxide layer is arranged, and the Mg _a Zn _1-a O type oxide is a metal atom alternately stacked in the c-axis direction. A wurtzite crystal structure composed of a layer and an oxygen atom layer, and the buffer layer is formed by orienting the c-axis of the wurtzite crystal structure in the layer thickness direction, and one atomic layer portion in contact with the substrate is formed. It is characterized in that it is formed as a metal monoatomic layer, and the remaining oxygen atomic layer and the metal atomic layer are alternately grown in a form following the monoatomic layer.

According to the present invention described above, the buffer layer formed on the substrate is entirely or at least on the contact side with the light emitting layer portion, Mg _a Zn having the same component system as that of the light emitting layer portion.
_1-a O-type oxide (however, the mixed crystal ratio a is not necessarily the same as that of the light emitting layer portion;
It may be described as O-type oxide or MgZnO)
It consists of. Since the part of the buffer layer on the bonding interface side and the light emitting layer part have basically the same crystal structure (wurtzite type) and have the same component system, the interaction between the components sandwiching the bonding interface. The local disorder of the crystal structure due to is less likely to occur, which is advantageous in realizing a light emitting layer portion having good crystallinity. The buffer layer may be entirely composed of MgZnO type oxide, for example. With this configuration, vapor phase growth of the buffer layer and the light emitting layer section can be extremely easily performed in the same equipment.

In the manufacturing method of the present invention, when the buffer layer is grown, the metal atomic layer is formed as a metal monoatomic layer on the substrate by the atomic layer epitaxy (ALE) method. After that, the remaining oxygen atomic layer and metal atomic layer are grown. ALE
When the method is adopted, if the first metal monolayer is completed, the formation of the metal atomic layer can be saturated by one atomic layer (so-called self-stopping function), and the atoms arranged in the layer will be deficient or displaced. Disturbance such as is hard to occur. By completing one atomic layer of such a disordered metal atomic layer and then growing the subsequent metal atomic layer and oxygen atomic layer, a buffer layer having extremely good crystallinity can be obtained, and naturally, The light emitting layer portion grown thereon also has good crystallinity, which is convenient for realizing a high performance light emitting device. Further, in the light emitting device of the present invention, by adopting the above-mentioned manufacturing method, the buffer layer is formed by aligning the c-axis of the wurtzite crystal structure in the layer thickness direction, and the one atomic layer portion in contact with the substrate is a metal monoatomic layer. The remaining oxygen atom layers and metal atom layers are alternately grown in the form of being formed and following the monoatomic layer. The buffer layer having such a structure has extremely good crystallinity, and as a result, the light emitting layer portion grown on the buffer layer has low defects and little disorder, and thus, the light emitting efficiency is excellent.

The ALE method is a metal organic vapor phase epitaxy method (MOVPE (Metal Organic Vapor Pour Method) in which a metal-organic gas and an oxygen component source gas are supplied into a reaction vessel in which a substrate is placed.
haseEpitaxy) method). Specifically, only the organometallic gas that is the raw material of the metal atomic layer is circulated in the reaction vessel to form the first metal atomic layer forming the buffer layer so as to be saturated by one atomic layer. The atomic layer. As shown in FIG. 8A, an organic metal (M
The O) molecule causes the metal atom to be chemically adsorbed on the substrate while decomposing and releasing the bonded organic group. At this time, A
When the LE method is adopted, the metal atom is adsorbed in a form in which a part of the bonded organic group remains, and the residual organic group is oriented in the surface side as shown in FIG. Form an atomic layer. Since the oriented residual organic group inhibits the adsorption of new metal atoms, when the one atomic layer is completed, the oriented residual organic group inhibits the adsorption of new metal atoms.
The manifestation of the self-terminating function becomes remarkable, and it becomes extremely difficult for disorder such as defects and displacement to occur in the atoms arranged in the layer.

Further, in the MOVPE method, since the oxygen partial pressure during growth can be freely changed, it is possible to effectively suppress the generation of oxygen desorption and eventually oxygen deficiency by raising the atmospheric pressure to some extent. As a result, it becomes possible to realize _a p-type Mg _a Zn _1-a O layer which is indispensable for a light emitting element, and in particular, _a p-type Mg _a Zn _1-a O layer having an oxygen deficiency concentration of 10 / cm ³ or less. . The lower the oxygen deficiency concentration is, the better (that is, it does not prevent the number of oxygen vacancies from reaching 0 / cm ³ ).

When the MOVPE method is used, if the entire buffer layer is made of MgZnO type oxide, the growth of the buffer layer and the light emitting layer portion can be performed in the same reaction vessel with an organic metal gas. Only by adjusting the ratio with the oxygen component source gas, it is possible to carry out consistently. Further, purging in the container when switching from the growth of the buffer layer to the growth of the light emitting layer section can be shortened or omitted as compared with the case where the buffer layer is made of another material such as GaN.

In order to obtain a high-luminance light emitting element, it is effective to grow the light emitting layer portion as having the following double hetero structure. That is, as a light emitting layer portion on the buffer layer, _a first conductivity type clad layer (p-type or n-type) made of Mg _a Zn _1-a O type oxide, an active layer, and a first conductivity type clad layer, respectively. A clad layer of a second conductivity type (n-type or p-type) having a conductivity type different from that of is laminated in this order to have a double hetero structure.

In this case, p-type MgZ by MOVPE method
The growth of the nO layer or the MgZnO active layer is 10 torr.
By carrying out in an atmosphere having a pressure of r (9.8 × 10 ⁴ Pa) or more, the generation of oxygen vacancies during film formation can be suppressed more effectively, and a p-type MgZnO layer or MgZnO active layer having good characteristics can be obtained. Can be obtained. In this case, more preferably, the oxygen partial pressure (oxygen-containing molecules other than O ₂ are also incorporated by converting the contained oxygen into O ₂ ).
Is preferably 10 torr (9.8 × 10 ⁴ Pa) or more. When an n-type MgZnO layer is formed on the buffer layer and an MgZnO active layer and a p-type MgZnO layer are grown on the buffer layer, when an oxygen deficiency occurs in the n-type MgZnO layer, the MgZnO activity that grows thereafter is reduced. Layer and p-type MgZ
Since it also affects the nO layer such as turbulence, n-type MgZnO
The layer is also preferably grown so that oxygen deficiency is not generated as much as possible. In this case, the n-type MgZnO layer has an n-type conductivity by adding an n-type dopant. On the other hand, a p-type MgZnO layer is formed on the buffer layer, and MgZnO is formed thereon.
When the active layer and the n-type MgZnO layer are formed, since the layer contributing to light emission is not formed on the n-type MgZnO layer, the n-type MgZnO layer has the conductivity type of n-type due to positive formation of oxygen vacancies. The method can also be adopted.

In order for Mg _a Zn _1-a O to become p-type, it is necessary to add an appropriate p-type dopant as described above. Such p-type dopants include N and G
One or more of a, 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.
As the metal element dopant, it is effective to use one or more of Ga, Al, In and Li, particularly Ga. By co-adding these with N, good p-type characteristics can be more reliably obtained.

In order to secure sufficient light emission characteristics, p
-Type Mg _a Zn _1-a O layer has a p-type carrier concentration of 1 × 1
It is preferable that it is not less than 0 ¹⁶ pieces / cm ^{3 and not} more than 8 × 10 ¹⁸ pieces / cm ³ . If the p-type carrier concentration is less than 1 × 10 ¹⁶ carriers / cm ³ , it may be difficult to obtain sufficient emission brightness. On the other hand, the p-type carrier concentration is 8 × 10
^{When the} number exceeds ¹⁸ / cm ³ , the amount of p-type carriers injected into the active layer becomes excessive, and it is back-diffused into the p-type Mg _a Zn _1-a O layer or overcomes the barrier to reach the n-type cladding layer. The p-type carriers that do not contribute to light emission due to inflow may increase, which may lead to a decrease in light emission efficiency. Also, n
For even type _{Mg a Zn 1-a} O layer, for the same reason, n-type carrier concentration of 1 × ^{10 16} atoms / cm ³ or more 8
It is preferably × 10 ¹⁸ pieces / cm ³ or less.

Next, as the material of the substrate, for example, aluminum oxide, gallium oxide, magnesium oxide, gallium nitride, aluminum nitride, silicon, silicon carbide, gallium arsenide, indium-tin composite oxide or glass can be used. In addition, as the aspect of the substrate particularly suitable for the present invention, there are the following aspects. That is, the Mg _a Zn _1-a O-type oxide has a wurtzite-type crystal structure composed of metal atomic layers and oxygen atomic layers alternately stacked in the c-axis direction, as shown in FIG. Oxygen atoms form a hexagonal atomic arrangement. Therefore, the substrate is an oxide single crystal substrate having oxygen atoms forming a hexagonal atomic arrangement and having the C plane ((0001) plane) of the hexagonal atomic arrangement as the main surface. It is effective in improving the crystal matching property of (3) and thus obtaining a light emitting layer portion having good crystallinity. In this case, the entire buffer layer is Mg _a Z
The n1 _- aO type oxide layer is formed on the main surface of the oxide single crystal substrate with the c-axis of the wurtzite type crystal structure oriented in the layer thickness direction. As such an oxide single crystal substrate, there is an oxide having a corundum type structure, and a sapphire substrate can be given as a more specific example thereof.

As shown in FIG. 7, it has a corundum type structure.
The oxide is a hexagonal atomic lattice of oxygen (O) atoms.
O atom (ion) layer and metal having an array in the c-axis direction
A structure in which atomic (ion: Al in the figure) layers are alternately stacked.
Have structure. In this crystal structure, both ends in the c-axis direction
One of the atomic layers that appears in
Is the metal atomic layer surface. Of these, the O atomic layer plane is the lattice constant
Except for the difference in the number, it is the same as the O atomic layer of wurtzite crystal structure.
It has the same O atom arrangement. Therefore, such a crystal structure
The main surface of the oxide single crystal substrate has a wurtzite crystal structure.
Mg_aZn _1-aO-type oxide buffer layer is grown
In the case of using a metal atom layer on the buffer layer side,
By stacking it on the main surface that forms the child layer surface,
It becomes possible to obtain a joint structure with high consistency.

As disclosed in Japanese Unexamined Patent Publication No. 2001-44500, it is possible to grow the buffer layer and the light emitting layer portion on the A surface of the sapphire substrate, and to flatten the crystal growth surface. effective. In this case, since metal atoms and oxygen atoms coexist on the A surface of the sapphire substrate, if the normal continuous growth MOVPE method as disclosed in JP 2001-44500 A is used, A
The probability that oxygen atom adsorption and zinc atom adsorption simultaneously occur on the plane ((11-20) plane) increases. As a result, c
Disturbances tend to occur in the stacking of the buffer layers grown in the axial orientation, and it may not always be possible to obtain a good quality buffer layer and thus a light emitting layer portion. However, as in the present invention, AL
When the E method is used, a metal monoatomic layer is forcibly formed on such an A surface, so that it is possible to obtain a buffer layer with good quality and thus a light emitting layer section with good reproducibility.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 schematically shows a laminated structure of a main part of a light emitting device according to the present invention, in which an n-type clad layer 34, an active layer 33 and a p-type clad layer 32 are laminated in this order. Have a section. Each of the layers 32-34 is _a Mg _a Zn _{1- a} O layer (0 ≦ a ≦.
1: Hereinafter, also referred to as MgZnO: However, as is clear from the range of the mixed crystal ratio a, even if described as MgZnO,
This includes the concept of each oxide of MgO and ZnO). The p-type MgZnO layer 32 contains, for example, N, Ga, A as a p-type dopant.
A small amount of one or more of l, In and Li is contained. The p-type carrier concentration is 1 × 10 ^{16 as} described above.
Pieces / cm ³ or more and 8 × 10 ¹⁸ pieces / cm ³ or less, for example, 1
It is adjusted in the range of about 0 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 atom layers and metal atom layers (Zn ions or Mg ions) are alternately stacked in the c-axis direction, as shown in FIG.
As shown in, the c-axis is formed along the layer thickness direction. When oxygen ions are lost to generate vacancies, oxygen vacancies are generated, and electrons that are n-type carriers are generated. If too many such oxygen vacancies are formed, the number of n-type carriers increases and p-type conductivity is not exhibited. Therefore, when forming the p-type MgZnO layer 32 and the MgZnO active layer 33, it is important to suppress the generation of this oxygen deficiency.

As the active layer 33, one having an appropriate band gap according to the required emission wavelength is used. For example, the one used for visible light emission has a wavelength of 400 nm to
Bandgap energy E capable of emitting light at 570 nm
The one having g (about 3.10 eV to 2.18 eV) is selected. This is the emission wavelength band covering from purple to green, but especially when used for blue emission, wavelength 4
A material having a band gap energy Eg (about 2.76 eV to 2.48 eV) capable of emitting light at 50 nm to 500 nm is selected. Further, the one used for ultraviolet light emission is a band gap energy Eg (4.43 eV to 3.10 eV) capable of emitting light at a wavelength of 280 nm to 400 nm.
Select the one that has

For example, the active layer 33 is made of p-type Mg _x Zn
It can be formed of a semiconductor that forms a type I band lineup with the _1-xO layer. Such an active layer 33 is, for example, a Mg _y Zn _1-y O layer (however,
0 ≦ y <1, x> y: hereinafter, also referred to as MgZnO active layer). "Active layer and p-type Mg
As shown in FIG. 4, a type I band lineup is formed between the ZnO layer and the ZnO layer.
Type MgZnO layer 32) with energy levels Ecp and Evp at the bottom of the conduction band and the top of the valence band, and energy levels Eci and Evi at the bottom of the conduction band and the top of the valence band of the active layer.
A junction structure in which the following magnitude relationship is established between and: Eci <Ecp (1) Evi> Evp (2)

In this structure, a potential barrier is generated both for the forward diffusion of holes from the active layer 33 to the n-type cladding layer 34 and the forward diffusion of electrons (n-type carriers) to the p-type cladding layer 32. Then, if the material selection of the n-type cladding layer 34 is performed so that the type I type band lineup similar to that shown in FIG. 4 is formed between the active layer 33 and the n-type cladding layer 34, the conduction layer is located at the position of the active layer. Well-shaped potential barriers are formed at both the bottom and the top of the valence band to enhance the confinement effect for both electrons and holes.
As a result, the promotion of carrier recombination, and thus the improvement in luminous efficiency, becomes more remarkable.

In the MgZnO active layer 33, the mixed crystal ratio y
The value of is also a factor that determines the band gap energy Eg. For example, when ultraviolet light emission with a wavelength of 280 nm to 400 nm is performed, the range of 0 ≦ y ≦ 0.5 is selected. Further, the height of the potential barrier formed is preferably about 0.1 eV to 0.3 eV for the light emitting diode and about 0.25 eV to 0.5 eV for the semiconductor laser light source. This value is the p-type Mg _x Zn _1-x O layer 2, M
g _y Zn _1-y O active layer 33 and n-type Mg _z Zn _1-z
It can be determined by selecting the values of the mixed crystal ratios x, y, z of the O layer 34.

An example of the manufacturing process of the light emitting device will be described below. First, as shown in FIG.
A buffer layer 11 made of MgZnO is epitaxially grown thereon. Next, the n-type MgZnO layer 34 (layer thickness, for example, 50 nm) and the MgZnO active layer 33 (layer thickness, for example, 30 nm).
nm) and the p-type MgZnO layer 32 (layer thickness, for example, 50 n
m) is epitaxially grown in this order (32-3)
5 may reverse the growth order). The epitaxial growth of each of these layers can be performed by the MOVPE method as described above.

By the MOVPE method, as shown in FIGS.
, The buffer layer 11 and the n-type MgZnO layer 3
4, the MgZnO active layer 33 and the p-type MgZnO layer 32 can all be continuously grown in the same reaction vessel using the same raw material. The temperature in the reaction container is adjusted by a heating source (infrared lamp in this embodiment) in order to promote a chemical reaction for forming a layer. The following materials can be used as the main raw material for each layer.・ Oxygen source gas: Oxygen gas can be used,
Supplying in the form of an oxidizing compound gas is desirable from the viewpoint of suppressing an excessive reaction with an organic metal described later.
Specifically, N ₂ O, NO, NO ₂ , CO and the like. In this embodiment, N ₂ O (nitrous oxide) is used.・ Zn source (metal component source) gas: dimethyl zinc (DMZ)
n), diethyl zinc (DEZn) and the like. -Mg source (metal component source) gas: Biscyclopentadienyl magnesium (Cp ₂ Mg) and the like.

The following can be used as the p-type dopant gas: Li source gas: normal butyl lithium; Si source gas: silicon hydride such as monosilane; C source gas: Hydrocarbons (eg, alkyl containing one or more C); Se source gas: hydrogen selenide, etc.

Further, one or more kinds of group III elements such as Al, Ga and In can be made to function as a good p-type dopant by co-addition with N which is a group V element. The following may be used as the dopant gas: Al source gas; trimethylaluminum (TMAl),
Triethylaluminum (TEAl) and the like; Ga source gas; trimethylgallium (TMGa), triethylgallium (TEGa) and the like; In source gas; trimethylindium (TMIn), triethylindium (TEIn) and the like. When N is used together with a metal element (Ga) as a p-type dopant, a gas serving as an N source is supplied together with an organometallic gas serving as a Ga source during vapor phase growth of a p-type MgZnO layer. . For example, in this embodiment, N ₂ O used as the oxygen component source also functions as the N source.

On the other hand, III such as B, Al, Ga and In
A group element can function as an n-type dopant when used alone. As the dopant gas,
Regarding Al, Ga and In, those described in the section of p-type dopant can be similarly used. As for B, for example, diborane (B ₂ H ₆ ) can be used.

Each of the above raw material gases is appropriately diluted with a carrier gas (for example, nitrogen gas) and supplied into the reaction vessel. The flow rate ratio of the organometallic gas MO serving as the Mg source and the Zn source for each layer is controlled by the mass flow controller MFC or the like depending on the difference in the mixed crystal ratio of each layer. The mass flow controller MFC also controls the flow rates of N ₂ O as the oxygen component source gas and the p-type dopant source gas.

The growth of the buffer layer 11 is performed as follows. The sequence of temperature control in the reaction container and the introduction of each gas in this embodiment is shown in FIG. First, the substrate 10 on which the layers are grown is a sapphire (that is, alumina single crystal) substrate whose crystal main axis is the c-axis, and the main surface on the oxygen atom plane side shown in FIG. 7 is used as the layer growth surface. Prior to the layer growth, the substrate 10 is sufficiently annealed in an oxidizing gas atmosphere. The oxidizing gas can be selected from O, CO, and N ₂ O, but N ₂ O is used in this embodiment because it is also used as an oxygen component source gas during layer growth described later. The annealing temperature is preferably 750 ° C. or higher (lower than the melting point of the substrate) and a holding time of 30 minutes or longer when the temperature is set in the MOVPE reaction vessel. However, if the substrate surface can be sufficiently cleaned by wet cleaning or the like, the annealing time may be shortened further than this.

When the above-mentioned annealing process is completed, as shown in FIG. 9, the substrate temperature is kept at 250 to 350 ° C. in order to suppress the occurrence of defects and the like while keeping the oxidizing gas atmosphere.
The temperature is lowered to the first temperature set to (350 ° C. in this embodiment). When the temperature stabilizes at the set value, the supply of the oxidizing gas is stopped, the inside of the reaction vessel is replaced with nitrogen gas, and the oxidizing gas is sufficiently purged out. The purge time varies depending on the shape and volume of the reaction container, but it is effective to secure it for 5 seconds or more.

Next, as shown in FIGS. 6 (a) and 8 (a), the organometallic gas MO is supplied into the reaction vessel, and the first metal atomic layer forming a part of the buffer layer 11 is formed by the ALE method. It is formed as a monatomic metal layer. As I already explained,
In the ALE method, the growth of the metal atomic layer is 1 due to the self-stop function.
Even if the metal layer MO is saturated and the supply of the organometallic gas MO is continued, further growth of the metal atomic layer does not occur.

After that, the supply of the organometallic gas MO is stopped and the inside of the reaction vessel is replaced with nitrogen gas to replace the organometallic gas MO.
8 is sufficiently purged out, N ₂ O is introduced as an oxygen component source gas (which is also an oxidizing gas atmosphere) as shown in FIG. 8C, and one atomic layer of oxygen is formed by the ALE method. To do. As a result, MgZnO is formed on the substrate 10.
This means that only one molecular layer has been formed.

Thereafter, as shown in FIG. 9, the temperature in the reaction vessel is kept at 400 to 80 while maintaining the oxidizing gas atmosphere.
Second temperature set to 0 ° C (750 ° C in this embodiment)
By raising the temperature to, and then continuously flowing an organometallic gas,
As shown in FIGS. 6B and 8D, the remaining portion of the buffer layer is grown by the usual MOVPE method. At that time, it is preferable to grow at a rate of about 0.1 nm / sec up to a layer thickness of about 10 nm and thereafter to grow at a rate of 1 nm / sec or more to obtain a buffer layer 11 having good flatness. it can. From the viewpoint of obtaining a buffer layer having higher crystallinity and flatness, the first plural molecular layers may be grown by the ALE method.

In this embodiment, the buffer layer 11 is formed as a layer of ZnO simple oxide, but has an appropriate mixed crystal ratio in accordance with the mixed crystal ratio of the layer on the side of the light emitting layer which is in contact with the buffer layer 11. It can also be a MgZnO composite oxide layer. Further, the Al atomic layer located immediately below the outermost O atomic layer of the sapphire substrate is formed of two Al atoms having different distances from the O atomic layer due to the peculiar circumstances of the corundum crystal structure shown in FIG.
It is composed of atomic sites Al-1 and Al-2.
In this case, the metal monoatomic layer laminated on the O atomic layer is Z
In the case of an n atomic layer, Zn atoms and Al through the O atomic layer
Coulombic repulsive force with the atoms causes both sites Al-1 and Al-
It is different from 2. Therefore, this causes Zn
In the atomic layer, a difference in displacement in the plane orthogonal direction with respect to the O atomic layer may occur between Zn atoms corresponding to both sites, which may lead to disordered stacking of subsequent layers. In order to reduce this effect, as shown in FIG. 10 (b) or (c), the first monomolecular layer (or plural molecular layers) is formed into a group II atom (eg Mg) having an ionic radius smaller than Zn. , Or group II atoms with a large ionic radius (eg Ca, Sr, B
It is effective to increase the crystallinity of the finally formed light emitting layer portion by forming a composite oxide layer in which a) and the like are mixed in an appropriate ratio. In this case, FIG. 11 (a)
As shown in FIG. 3, such a complex oxide layer (metal cation composition is A) and a clad layer formed on the buffer layer 11 (metal cation composition is B: n-type MgZnO layer 54 in the figure). Between both cation compositions A and B
It is also effective to form a composition gradient layer in which the metal cation composition is inclined in the layer thickness direction in order to enhance the above effect. For example, when both the complex oxide layer and the clad layer are made of MgZnO, the metal cation composition is the composition parameter ν≡N, where Mg ion mol content is NMg, and Zn ion mol content is NZn.
If Mg / (NMg + NZn) is represented, ν of the complex oxide layer is represented by A, and ν of the cladding layer is represented by B, the compositionally graded layer will have ν as shown in FIG. 11B, for example. It can be formed as a layer that continuously changes in the layer thickness direction between A and B.

Now, when the formation of the buffer layer 11 is completed, as shown in FIG. 6C, the n-type MgZnO layer 34,
The MgZnO active layer 33 and the p-type MgZnO layer 32 are formed in this order by MOVPE. In the case where the n-type MgZnO layer 32 is formed below the p-type MgZnO layer 32 (on the side of the substrate 10) as in the present embodiment, an n-type dopant is introduced and oxygen is introduced in the same manner as the p-type MgZnO layer 32 described later. It is desirable to carry out layer growth under conditions where defects such as defects do not occur as much as possible. On the other hand, the n-type MgZnO layer 34 is replaced with p-type MgZn.
In the case where it is formed above the nO layer 32, a method of positively causing oxygen vacancies to make it n-type can also be adopted.
It is effective to lower the atmospheric pressure (for example, less than 10 torr) as compared with the case of growing the ZnO active layer 53 and the p-type MgZnO layer 52. Further, the ratio of the group II and the group VI of the feed material (supply II / VI ratio) may be increased.

In addition, the MgZnO active layer 33 and the p-type Mg
When the ZnO layer 32 is grown, it is effective to maintain the pressure in the reaction vessel at 10 torr or more in order to suppress the generation of oxygen vacancies. As a result, the release of oxygen is further suppressed, and the MgZnO layer with few oxygen defects can be grown. Especially when N ₂ O is used as the oxygen component source,
The above pressure setting prevents the dissociation of N ₂ O from rapidly progressing, and it becomes possible to more effectively suppress the generation of oxygen deficiency. The higher the atmospheric pressure, the higher the oxygen desorption suppression effect, but 760 torr (1.0
Even at pressures up to about 1 × 10 ⁵ Pa or 1 atm), the effect is sufficiently remarkable. For example, when the pressure is 760 torr or less, the inside of the reaction container is at normal pressure or reduced pressure, which is advantageous in that the container sealing structure can be relatively simple. On the other hand, 760
When a pressure exceeding torr is adopted, the inside of the container is pressurized, so it is necessary to consider a rather strong seal structure so that the gas inside does not leak out, and if the pressure is considerably high, a pressure resistant structure etc. However, the oxygen desorption suppressing effect becomes more remarkable. In this case, the upper limit of the pressure should be set to an appropriate value in consideration of the device cost and the achievable oxygen desorption suppressing effect (for example, 7600 torr ((1.
01 × 10 ⁶ Pa or 10 atm))).

When the growth of the light emitting layer portion is completed in this manner, the active layer 33 and a part of the p-type MgZnO layer 32 are partially removed by photolithography or the like, as shown in FIG. While forming the transparent electrode 125 made of a material (ITO) or the like, the remaining p-type MgZnO layer 3
The light emitting element 1 is obtained by forming the metal electrode 122 on the substrate 2 and then dicing it together with the substrate 10. It is obvious that the light emitting device 1 is such that the buffer layer 11 made of MgZnO is formed on the substrate 10 and the light emitting layer portion made of MgZnO is further formed. Light is extracted mainly from the transparent sapphire substrate 10 side.

FIG. 12 shows a modification of the method for manufacturing a light emitting device according to the present invention. Here, FIG.
As shown in (a), on the buffer layer 11, the p-type MgZnO layer 32 and the MgZnO active layer 3 are arranged in the reverse order of FIG.
3 and the n-type MgZnO layer 34 in this order, (b)
As shown in, the metal reflective layer 22 which also serves as an electrode is formed on the n-type MgZnO layer 34. Then, the sapphire substrate 10
Is removed, the transparent electrode 25 made of ITO or the like is formed on the p-type MgZnO layer 32 side, and then dicing is performed as shown in (d) to obtain the light emitting element 104. The light emitting element 10
The light extraction of No. 4 is performed from the transparent electrode 25 side. According to this structure, MgZn forming the light emitting layer portion on the side where the substrate 10 is peeled off
Since the metal layer of O is exposed, an element having more excellent weather resistance can be obtained.

[0042]

In the manufacturing method of the present invention, when the buffer layer is grown, the atomic layer epitaxy (AL
E: Atomic Layer Epitaxy) is used to form a metal atomic layer on the substrate as a metal monoatomic layer, and then the remaining oxygen atomic layer and metal atomic layer are grown. When the ALE method is adopted, if the first metal monoatomic layer is completed, the formation of the metal atomic layer can be saturated by one atomic layer (self-stop function), and the atoms arranged in the layer will also have defects or displacement. Disturbance such as is hard to occur. Such a metal atomic layer with less disorder,
After the completion of one atomic layer, the subsequent metal atomic layer and oxygen atomic layer are grown to obtain a buffer layer having extremely excellent crystallinity, and naturally, the light emitting layer portion grown thereon is also crystalline. Therefore, it is convenient to realize a high-performance light emitting device with good reproducibility. Further, in the light emitting device of the present invention, the buffer layer is formed by adopting the above production method.
The c-axis of the wurtzite crystal structure is oriented in the layer thickness direction, the one atomic layer portion in contact with the substrate is formed as a metal monoatomic layer, and the remaining oxygen atomic layer and metal atomic layer are formed in a continuous form of the layer. And are grown alternately. The buffer layer having such a structure has extremely good crystallinity, and as a result, the light emitting layer portion grown on the buffer layer has low defects and little disorder, and thus, the light emitting efficiency is excellent.

[Brief description of drawings]

FIG. 1 is a diagram conceptually showing a light emitting layer portion having a double hetero structure composed of MgZnO.

FIG. 2 is a schematic diagram showing a crystal structure of MgZnO.

FIG. 3 is a schematic diagram showing an arrangement form of metal ions and oxygen ions in the MgZnO layer.

FIG. 4 is a schematic band diagram of a light emitting device using a junction structure of a type I band lineup.

FIG. 5 is a schematic view showing a specific example of a light emitting device of the present invention.

6 is an explanatory view showing an example of a manufacturing process of the light emitting device of FIG.

FIG. 7 is a schematic view of a corundum crystal structure.

FIG. 8 is an operation explanatory view of the method for manufacturing a light emitting device of the present invention.

9 is a diagram illustrating a temperature control sequence and a gas supply sequence in the process of FIG.

FIG. 10 is an explanatory diagram of an effect obtained by using a mixed metal atomic layer as a metal atomic layer for ALE growth.

FIG. 11 is a schematic view showing an example in which the buffer layer is a metal composition gradient layer.

FIG. 12 is an explanatory view showing an example of a manufacturing process of another light emitting element of the present invention.

[Explanation of symbols]

1,104 Light emitting element 10 sapphire substrate 11 N buffer layer 32 p-type MgZnO clad layer 33 MgZnO active layer 34 n-type MgZnO cladding layer

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 5F041 AA03 AA40 CA04 CA41 CA46                       CA65 CA67 CA82 CA88 CB15                 5F045 AA04 AA15 AB22 AC08 AC09                       AD08 AD09 AD10 AD11 AD12                       AE21 AE23 AE30 AF06 AF09                       CA11 CB01 CB02 DA53 DA63

Claims (6)

[Claims] 1. A method for manufacturing a light-emitting device, wherein the light-emitting layer portion is made of Mg _a Zn _1-a O (where 0 ≦ a ≦ 1) type oxide, wherein at least the contact side of the light-emitting layer portion is Mg _a.
A buffer layer formed of _a Zn _1-a O type oxide layer is grown on a substrate, and the light emitting layer portion is grown on the buffer layer. The Mg _a Zn _1-a O type oxide is c It has a wurtzite crystal structure composed of metal atomic layers and oxygen atomic layers that are alternately laminated in the axial direction, and the buffer layer has the c-axis of the wurtzite crystalline structure oriented in the layer thickness direction. The atomic layer epitaxy method to form the metal atomic layer on the substrate as a metal monoatomic layer, and then the remaining oxygen atomic layer and the metal atomic layer. And a method for manufacturing a light emitting device, which comprises growing 2. The atomic layer epitaxy method is carried out in the form of a metal organic chemical vapor deposition method in which a metal organic gas and an oxygen component source gas are supplied into a reaction vessel in which the substrate is arranged.
A method for manufacturing a light-emitting device as described above. 3. The substrate is an oxide single crystal substrate having oxygen atoms forming a hexagonal atomic arrangement and having a C-plane of the hexagonal atomic arrangement as a main surface, wherein the entire buffer layer is C of the wurtzite crystal structure
The method for manufacturing a light-emitting element according to claim 1, wherein the axis is oriented in the layer thickness direction on the main surface of the oxide single crystal substrate. 4. The oxide single crystal substrate is made of an oxide having a corundum type structure, and the buffer layer is formed on the main surface serving as an oxygen surface. Manufacturing method of the light emitting device. 5. The method for manufacturing a light emitting device according to claim 3, wherein the oxide single crystal substrate is a sapphire substrate. 6. A light emitting device having a light emitting layer portion formed of a Mg _a Zn _1-a O (where 0 ≦ a ≦ 1) type oxide is formed on a substrate, wherein the substrate and the light emitting layer portion. And at least the side of contact with the light emitting layer portion is Mg _a Zn.
With arranging the buffer layer and _{1-a O-type} oxide layer, the Mg a _Zn 1-a _O-type oxide is formed of a metal atom layer and an oxygen atom layers alternately stacked in the c-axis direction A wurtzite crystal structure, the buffer layer is formed by aligning the c-axis of the wurtzite crystal structure in the layer thickness direction, and the one atomic layer portion in contact with the substrate is formed as a metal monoatomic layer, Further, the light emitting element is characterized in that the remaining oxygen atomic layer and the metal atomic layer are alternately grown in a form subsequent to the monoatomic layer.