JP2000022205A - Semiconductor light emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance an efficiency of an element, lower an operating voltage, and increase design flexibility, by a method wherein at least an inorganic substance layer and an organic substance layer of a hole transportation are laminated on a substrate, and the inorganic substance layer is formed as an oxide film having an wurtzite-containing crystal structure. SOLUTION: A luminous element is constituted by laminating a Si substrate 1, a hole injection electrode 2, an inorganic substance layer 4, an organic substance layer 5, and an electron injection electrode 3, and a drive power source E is connected to each electrode. A buffer layer is provided on a substrate, and an wurtzite compound thin film is formed thereon. A thin film such as an R-Zr-based oxide, etc., is formed on the buffer layer, and on the buffer layer containing at least a species of thin films, the thin film having high crystallinity and superior surface flatness can be formed on a Si substrate. For this reason, a thin film having an wurtzite crystal structure such as a ZnO-based thin film, an AlGaInN-based thin film, or the like is formed as an epitaxial film on the Si substrate via the buffer layer, thereby attaining monocrystal of high quality.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an inorganic / organic junction structure, and more particularly to an organic thin film light emitting device and a semiconductor light emitting device such as a light emitting diode (LED) and a laser diode (LD).

[0002]

2. Description of the Related Art Recent developments in blue light-emitting devices have been remarkable. In particular, first, LEDs and LDs based on the fundamental principle of injection and recombination light emission of electrons and holes by a semiconductor pn junction.
Secondly, an organic EL is formed by laminating an organic thin film serving as a light-emitting layer together with an electron-transporting and hole-transporting organic substance, and similar to a semiconductor pn junction, based on the principle of injection and emission recombination of electrons and holes. The above two R & D activities have been activated.

The above-mentioned LEDs and LDs have been studied for a long time, but in recent years, GaN-based and ZnSe-based studies have been advanced, and for example, Nikkei Electronics No.674, p.
As shown in 79 (1996), an LED that includes a stacked structure of these nitride semiconductor layers and emits light of a short wavelength such as blue or green has already been developed. At present, LD is reported on a trial basis. In the development of LED and LD,
The reason why a long period of time was required is that a wide-gap semiconductor material such as GaN or ZnSe can obtain an n-type semiconductor but cannot convert it into a p-type semiconductor. Recently, p-type has been reported due to the progress of the crystal growth technology, and LED has been made possible, and furthermore, rapid progress has been made with LD.

[0004] However, in mass production of blue devices, cost is a big problem compared to crystal growth conditions and equipment, and red LEDs such as a single crystal substrate to be used. At present, it is said that if the cost of a blue device is reduced by half, the market will be increased fivefold, and it is urgently necessary to reduce the price and improve the yield compared to the conventional technology.

Conventional LEDs and LDs use expensive single crystal substrates. For example, sapphire is used for GaN, and GaAs is used for ZnSe.

However, in recent years, an electronic device in which a functional film such as an oxide or a nitride is formed and integrated on a Si substrate which is a semiconductor crystal substrate has been devised. If a light emitting element is formed on a Si substrate, there are great advantages not only in cost but also in integration and element application.

[0007] The crystal structures of some semiconductor materials that are of practical value are of the wurtzite type, as typified by ZnO and AlN. Since the epitaxial growth of a wurtzite type compound largely depends on the crystal orientation of the substrate material, it is difficult to directly epitaxially grow on a cubic Si single crystal substrate.

When a ZnO thin film is to be directly epitaxially grown on a Si substrate, Si
An O ₂ layer is formed. When the SiO ₂ layer exists on the surface of the Si substrate, the arrangement information of the Si crystal is not transmitted when the ZnO crystal grows. Therefore, the grown ZnO thin film becomes a c-axis oriented polycrystalline film. Therefore, there is no report that a ZnO thin film is epitaxially grown on a Si substrate.

There have been several reports on attempts to epitaxially grow AlN thin films directly on Si substrates. For example, in Jpn.J.Apl.Phys.vol.20.L173 (1981), AlN was epitaxially grown by MOCVD (chemical vapor deposition using an organic metal) at a temperature of a Si substrate of 1260 ° C. It has been reported. Also,
Several research examples using AlN as a buffer layer for a GaN-based light emitting device have been reported. For example, in the IEICE Technical Report CPM92 1-13, P45 (1992), MOVP
It has been reported that epitaxial growth can be performed at 1100 ° C. or higher by an E (metal organic chemical vapor deposition) method.

In each of these cases, AlN
The growth temperature of the thin film is as high as 1100 ° C. or higher. When an AlN thin film is formed at a temperature of 1000 ° C. or higher, Al, which is a component of AlN, easily reacts with the Si substrate to form aluminum silicide. Therefore, when the forming temperature is 1000 ° C. or higher, it is necessary to pay close attention in order to suppress the production of aluminum silicide, which causes a problem that mass productivity and reproducibility are reduced.

A thin film made of a group III-V nitride semiconductor such as gallium nitride (GaN), aluminum nitride (AlN), indium nitride (InN), aluminum gallium nitride (AlGaN), or a mixed crystal thereof has an electric field. It is used for nitride semiconductor devices such as effect transistors, LEDs (light emitting diodes), laser diodes, etc., and recently includes a laminated structure of these nitride semiconductor layers and emits light of short wavelengths such as blue and green. LED is attracting attention.

III-V nitride semiconductor layer, for example, GaN
In a semiconductor element using a thin film, sapphire is generally used as a substrate for forming a GaN thin film. However, sapphire has a large difference in lattice constant and thermal expansion coefficient from GaN.
There is a problem that dislocations are introduced on the side and the GaN crystal is deformed by stress, so that a good quality crystal cannot be obtained. In addition, the sapphire substrate has a problem that it is difficult to divide the cleavage plane, and it is difficult to form an end face when manufacturing a laser diode. Further, the sapphire substrate is more expensive than a semiconductor substrate such as Si, and has problems such as poor surface flatness. Further, there is a problem that the sapphire substrate has no conductivity.

On the other hand, Si also has a lattice constant difference from GaN,
It is difficult to form a high-quality GaN thin film on a Si single crystal substrate because of a large difference between the thermal expansion coefficient and the lattice structure.

As a proposal for improving the crystallinity of a thin film made of a nitride semiconductor such as GaN, see, for example,
No. 45960 describes that an InGaAlN layer is provided on a sapphire substrate or a Si substrate via a ZnO buffer layer. In this publication, Zn on a Si substrate
The O buffer layer is directly formed by a sputtering method or the like.
However, in our experiments, as described above, Si
It was found that it was practically impossible to form a ZnO buffer layer as a single crystal film (epitaxial film in this specification) on a substrate, and it was not possible to form a film having excellent crystallinity and surface properties. Therefore, such Zn
A nitride semiconductor layer having good crystallinity cannot be formed on the O buffer layer.

Japanese Patent Application Laid-Open No. Hei 8-264894 discloses that Ca _x Mg _1-x F ₂ (0 ≦ x
≦ 1) layer and _{Mg t Ca 3-t N 2} (0 ≦ t ≦ 3) layer at least one is _{formed, Ga y In z Al 1-} yz thereon
A semiconductor device having an N (0 ≦ y, z ≦ 1) layer is described. In this publication, Si or Si having high surface flatness is used.
The effect is that C or the like can be used and a high quality GaInAlN layer can be formed. However, according to the experiments of the present inventors, Ca _x Mg _1-x formed on a Si substrate
It was found that the F ₂ layer and the Mg _t Ca _3-t N ₂ layer had insufficient crystallinity and surface properties. Therefore, a nitride semiconductor layer having good crystallinity cannot be formed over these layers.

It is also known to use an AlN thin film or a SiC thin film as a buffer layer when forming a GaN thin film on a Si substrate [J. Cryst. Growth 128, 391 (199).
3) and J. Cryst. Growth 115,634 (1991)]. However, according to the experiments of the present inventors, it was found that A directly formed on a Si substrate
It was found that the 1N thin film and the SiC thin film had insufficient crystallinity and surface properties. Therefore, a nitride semiconductor layer having good crystallinity cannot be formed on these thin films.

On the other hand, in the organic EL, since an element can be formed in a large area on glass, research and development for a display are being advanced. In general, an organic EL device is formed by forming a transparent electrode such as ITO on a glass substrate, forming an organic amine-based hole transport layer thereon, and, for example, an aluminum quinolinol complex (Alq3) which exhibits electron conductivity and emits strong light. An organic light emitting layer is laminated, and further, an electrode having a small work function such as MgAg is formed to be a basic element.

The device structure reported so far has a structure in which one or more organic compound layers are sandwiched between a hole injection electrode and an electron injection electrode. There is a two-layer structure or a three-layer structure.

Examples of the two-layer structure include a structure in which a hole transport layer and a light emitting layer are formed between a hole injection electrode and an electron injection electrode, or a structure in which a light emitting layer and an electron transport layer are provided between a hole injection electrode and an electron injection electrode. There is a structure in which a layer is formed. As an example of the three-layer structure, there is a structure in which a hole transport layer, a light emitting layer, and an electron transport layer are formed between a hole injection electrode and an electron injection electrode. Also, a single-layer structure in which a single layer has all the functions has been reported for polymers and mixed systems.

FIG. 8 and FIG. 9 show a structure which is widely used at present.

In FIG. 8, a hole transport layer 14 and a light emitting layer 15 which are organic compounds are formed between a hole injection electrode 12 and an electron injection electrode 13 provided on a substrate 11. In this case, the light emitting layer 15 also functions as an electron transport layer.

In FIG. 9, a hole transport layer 14, a light emitting layer 15, and an electron transport layer 16, which are organic compounds, are formed between a hole injection electrode 12 and an electron injection electrode 13 provided on a substrate 11.

In these organic ELs, reliability is a common problem. In an organic EL, in principle, it is necessary to use a metal having a low work function for an electron injection electrode for electron injection. Therefore, MgAg, Al
Li or the like must be used. These materials are easily oxidized, causing reliability problems. Further, the deterioration of the organic thin film is remarkably large as compared with the LED and LD.

In order to solve such a problem, a method has been conceived which utilizes the respective merits of the organic material and the inorganic semiconductor material. That is, in a light emitting element using a pn junction, an organic hole transport layer is used instead of a p-type semiconductor instead of a p-type semiconductor, so that an organic hole can be formed in the n-type semiconductor. This is an organic / inorganic semiconductor junction in which light is emitted in the n-type semiconductor layer by injecting holes from the transport layer.

Such a study is described in JP-A-2-19647.
5, JP-A-3-262170, Jpn. J. Appl.
Phys. Vol. 32 (1993) pp. 1691-
1695, it was impossible to obtain characteristics exceeding the conventional organic EL device due to the emission characteristics and the reliability of the basic device.

[0026]

SUMMARY OF THE INVENTION It is an object of the present invention to provide improved efficiency, lower operating voltage, greater design freedom,
Moreover, it is to provide a new and improved semiconductor light emitting device with increased reliability.

[0027]

This and other objects are achieved by any one of the following constitutions (1) to (8). (1) A structure in which at least an inorganic layer and an organic layer having a hole-transporting property are laminated on a substrate, wherein the inorganic layer has an oxide film having a wurtzite-type crystal structure and / or a wurtzite-type crystal structure. Nitride film and / or
Alternatively, a semiconductor light emitting device which is a sulfide film having a wurtzite type crystal structure. (2) The semiconductor light emitting device according to (1), wherein the inorganic layer is an n-type semiconductor layer. (3) The semiconductor light emitting device according to (1) or (2), wherein the inorganic layer is an epitaxial film. (4) The above (1) to (1) to wherein the substrate is a Si single crystal substrate
(3) Any of the semiconductor light emitting devices. (5) at least the surface of the substrate is a single crystal of Si, and has a buffer layer between the substrate and the inorganic layer;
The buffer layer is composed of an oxide buffer layer and / or a nitride buffer layer, and the oxide buffer layer is composed of an oxide mainly containing a rare earth element (including Sc and Y) and / or zirconium oxide. It has an R-Zr-based oxide thin film which is a film, or has an AlOx-based thin film which is an epitaxial film mainly composed of Al and O, and the nitride buffer layer is made of titanium nitride, niobium nitride, tantalum nitride and zirconium nitride. NaCl which is an epitaxial film containing at least one of
The semiconductor light emitting device according to any one of the above (1) to (4), comprising a type nitride thin film. (6) The inorganic layer is made of Zn containing zinc oxide as a main component.
The semiconductor light emitting device according to any one of the above (1) to (5), having an O-based thin film. (7) A metal thin film is provided between the buffer layer and the n-type semiconductor layer of the inorganic layer or in the buffer layer, and the metal thin film is made of Pt, Ir, Os, Re, Pd, Rh, and R.
The semiconductor light emitting device according to any one of the above (1) to (6), which is an epitaxial film containing one or two or more kinds of u as a main component. (8) The metal thin film has a (111) plane or a (000) plane.
1) The semiconductor light emitting device according to the above (7), wherein the surface is oriented parallel to the substrate surface.

[0028]

According to the present invention, a layer of an n-type semiconductor and a hole transport layer of an organic compound, which are relatively easily obtained, are laminated on an inorganic material which is a wide gap semiconductor and which is difficult to be p-type. A hole transporting layer made of an organic compound is used instead of the p-type semiconductor of the LED element to inject holes into the n-type semiconductor to obtain light emission characteristics.

Conventionally studied organic / inorganic junctions, ie, JP-A-2-196475 and JP-A-3-26217
0, Jpn. J. Appl. Phys. Vol. 32
(1993) pp. In 1691-1695, as an n-type inorganic semiconductor material, Si _1-x C _x (0 ≦ x1), GaP,
ZnS, ZnSe and the like have been used.

These junctions, ie, these inorganic n
In the type semiconductor / organic hole transport layer, TPD (tetraphenyldiaminodiphenyl) or the like is used for the organic hole transport layer. However, in a light emission experiment, no light emission was observed, or only very weak light emission was observed, although diode characteristics were obtained.

Examination of the physical properties of the inorganic materials used in these diodes, in particular, examining the binding energy of excitons contributing to light emission, showed that Si _1-x C _x (0 ≦ x1), GaP was 10 meV or less, It was found that ZnSe was as low as 22 mev.

On the other hand, it has been found that the binding energy of excitons of oxides and nitrides having a wurtzite type crystal structure is generally high. For example, GaN has 24 meV and ZnO has 60 meV. In particular, the value of ZnO is very large, which is suitable for a light emitting element.

Therefore, the inventor paid attention to an inorganic layer having high exciton efficiency instead of the n-type semiconductor thin film conventionally used in the organic / inorganic junction.

The present invention comprises an oxide film having a wurtzite crystal structure and / or a nitride film having a wurtzite crystal structure, which is an n-type semiconductor having a high exciton efficiency, instead of the conventional inorganic n-type semiconductor. As a result of using the layer, holes of the hole transport layer made of an organic compound can be injected into the light emitting layer made of an n-type semiconductor, and an element having stable light emitting characteristics can be obtained.

In general, a thin film having p-type conductivity cannot be easily obtained from a layer made of an oxide film having a wurtzite crystal structure and / or a nitride film having a wurtzite crystal structure. However, the inventor has confirmed through experiments that a thin film exhibiting n-type conductivity can be easily obtained either as an epitaxial film or as an amorphous or polycrystalline thin film. In particular, it was confirmed that a thin film having a wurtzite type crystal structure easily grows on a substrate in the form of an epitaxial film or a c-axis oriented film, and was found to be suitable for a light emitting device.

Further, a thin film having a wurtzite type crystal structure is
Doping is also easy. In addition, there is little change in electrical characteristics due to energization or temperature, and there is no electrochemical reaction with the electrode material. Furthermore, it is excellent in translucency.

[0037]

BEST MODE FOR CARRYING OUT THE INVENTION A light-emitting device of the present invention is provided on a substrate.
It has a structure in which at least an inorganic layer and a hole transporting organic layer are laminated, and the inorganic layer is an oxide film having a wurtzite type crystal structure and / or a nitride film having a wurtzite type crystal structure and / or a wurtzite type. It is a sulfide film having a crystal structure.

In the present invention, as a substrate for forming a thin film laminated structure such as an inorganic layer and an organic layer having a hole transporting property, a crystalline substrate such as an amorphous substrate such as glass or quartz,
For example, Si, GaAs, ZnSe, ZnS, Ga
Examples thereof include P, InP, sapphire, and MgO, and a substrate in which a crystalline, amorphous, or metal buffer layer is formed on these crystalline substrates can also be used. As the metal substrate, Mo, Al, Pt, Ir, Au, Pd, or the like can be used. In particular, when the inorganic layer is used in the form of an epitaxial film, it is particularly preferable to use a sapphire substrate and a Si substrate as described later.

The inorganic layer used in the present invention is an oxide film having a wurtzite crystal structure and / or a nitride film having a wurtzite crystal structure and / or a sulfide film having a wurtzite crystal structure. The oxide film is mainly composed of zinc oxide, preferably substantially
O. The nitride film is an AlGaInN-based thin film mainly containing N and at least one selected from Al, Ga and In. The composition of the AlGaInN-based thin film is not particularly limited, but is substantially Ga _x In _y Al _1-xy N (0 ≦ x ≦ 1, 0 ≦ x + y ≦
It is preferable to have a composition represented by 1). The sulfide film is mainly composed of cadmium sulfide or zinc sulfide, and is preferably substantially composed of CdS or ZnS.

Although it is preferable that these inorganic layers are made into n-type semiconductors, they may be insulating thin films. Some of these compounds show the properties of an n-type semiconductor as they are, but it is preferable to add a known doping substance or gas to make these compounds n-type. It is particularly preferable to perform n-type conversion by shifting the composition without doping. As the doping, for example, Ga, Al, In, etc.
a _x In _y Al _1-xy N is made into a semiconductor.
A known doping element may be added.

Examples of the form of the inorganic layer include an amorphous thin film, a microcrystalline thin film, a polycrystalline thin film, an epitaxial thin film, a single crystal thin film, a thin film in which these are intermingled, and a thin film including the above oxides and nitrides. A laminated thin film or an artificial lattice thin film having a different sulfide composition is used. In particular, when a display element is used on a glass substrate, a polycrystalline thin film is preferable. Since the polycrystalline thin film can be formed over a large area and is crystalline, the semiconductor characteristics of the inorganic layer can be effectively used. For an LED or the like, an epitaxial thin film or a single crystal thin film is preferably used.

The thickness of the inorganic layer is not particularly limited, but is usually about 1 to 300 nm. In particular, in the case of an inorganic layer having a high resistivity which does not have strong n-type properties, the thickness is preferably about 1 to 10 nm for driving a light emitting element at a low voltage. The n-type inorganic layer may be relatively thick,
50nm ~ 100 for large area and pinhole free
nm is preferred.

As a method of manufacturing the inorganic layer, various physical or chemical thin film forming methods such as a sputtering method, a vapor deposition method, an MBE method, and a CVD method are used. Post-treatment may be used after the formation of a thin film such as a sulfuration method.

On the other hand, the hole transporting organic material layer in the present invention comprises one kind of organic compound thin film or a laminated film of two or more kinds of organic compound thin films.

The organic compound is preferably composed of a substance having a high hole mobility.

As such an organic compound, the aforementioned T
In addition to PD, conventionally known materials are all applied. For example, diamine, TAD, pyrazoline derivative, α-NP
Organic materials such as D, CuPc, HTM-based, and TDAB-based are exemplified.

Examples of the hole transporting material having a high hole mobility include, for example, JP-A-63-295695, JP-A-2-191694, and JP-A-3-792.
JP, JP-A-5-234681, JP-A-5-25-2
39455, JP-A-5-299174, JP-A-7-126225, JP-A-7-126226
JP, JP-A-8-100172, EP0650
Various organic compounds described in 955A1 and the like can be used. For example, a tetraarylbendicine compound (triaryldiamine or triphenyldiamine: TPD), an aromatic tertiary amine, a hydrazone derivative,
Carbazole derivatives, triazole derivatives, imidazole derivatives, oxadiazole derivatives having an amino group,
And polythiophene. These compounds may be used alone or in combination of two or more. When two or more kinds are used in combination, they may be stacked as separate layers or mixed.

The electron injection electrode material is preferably a material having a low work function, for example, K, Li, Na, Mg, La, C
e, Ca, Sr, Ba, Al, Ag, In, Sn, Z
It is preferable to use a single metal element such as n or Zr, or a two-component or three-component alloy system containing them for improving the stability. As an alloy system, for example, Ag · Mg (A
g: 0.1 to 50 at%), Al.Li (Li: 0.01)
１２12 at%), In · Mg (Mg: 50 to 80 at%),
Al.Ca (Ca: 0.01 to 20 at%) and the like. Also, low-resistance semiconductors such as ZnO, ITO, G
aN and the like are preferable. As the electron injection electrode layer, a thin film made of these materials, or a multilayer thin film of two or more of these materials is used. A low-resistance semiconductor electrode can function as a hole injection electrode at the same time as being used as an electron injection electrode, so that the basic element structure can be multilayered.

The material for the hole injection electrode is generally IT
O is used, but a low-resistance semiconductor such as ZnO or GaN is also preferable. The electrode on the light extraction side is preferably a transparent or translucent electrode. ITO is usually In ₂ O
_{Although 3} and SnO are contained in a stoichiometric composition, the amount of O may slightly deviate from this. Sn for In ₂ O ₃
The mixing ratio of O ₂ is 1 to 20% by weight, further 5 to 12% by weight.
Is preferred. In addition, Zn for In ₂ O ₃ in IZO
The mixing ratio of O ₂ is usually about 12 to 32% by weight.

Further, as a hole injection electrode material other than these, a conductive oxide is preferable, and particularly, a material containing the following conductive oxide is preferable.

NaCl type oxide: TiO, VO, Nb
O, RO _1-x (where, R: one or more rare earth elements (Sc
And Y), 0 ≦ x <1), LiVO _{2 and the} like.

Spinel type oxide: LiTi ₂ O ₄ , Li
M _x Ti _2-x O ₄ (where M = Li, Al, Cr, 0 <
_{x <2), Li 1-} x M x Ti 2 O 4 ( where, M = Mg,
Mn, 0 <x <1), LiV ₂ O ₄ , Fe ₃ O _{4 and the} like.

Perovskite oxide: ReO ₃ , WO
₃ , MxReO ₃ (where M metal, 0 <x <0.
5), MxWO ₃ (where M = metal, 0 <x <0.
5), A ₂ P ₈ W ₃₂ O ₁₁₂ (where A = K, Rb, T
l), Na _x Ta _y W _{1 -y} O ₃ (where 0 ≦ x <1,0
<Y <1), RNbO ₃ (where R: one or more rare earth elements (including Sc and Y)), Na _1-x Sr _x NbO ₃
(Where 0 ≦ x ≦ 1), RTiO ₃ (where R: one or more rare earth elements (including Sc and Y)), Can _{+ 1
Ti n O 3n + 1-y} ( where, n = 2,3, ..., y >
0), CaVO ₃ , SrVO ₃ , R _1-x Sr _x VO ₃ (where R: one or more rare earth elements (including Sc and Y);
0 ≦ x ≦ 1), R _1−x Ba _x VO ₃ (where R: one or more rare earth elements (including Sc and Y), 0 ≦ x ≦ 1),
_{Sr n + 1 V n O 3n} + 1-y ( where, n = 1, 2,
3. . . . _{, Y> 0), Ba n} + 1 V n O 3n + 1-y ( where, n = 1,2,3 ...., y> 0), R 4 BaCu 5
O _13-y (where, R: one or more rare earth elements (including Sc and Y), 0 ≦ y), R ₅ SrCu ₆ O ₁₅ (where,
R: one or more rare earths (including Sc and Y)), R
₂ SrCu ₂ O ₆ . ₂ (where R: one or more rare earth elements (including Sc and Y)), R _1-x Sr _x VO ₃ (where R: one or more rare earth elements (including Sc and Y)), CaCrO ₃ , SrCrO ₃ , RMnO ₃ (where R: one or more rare earths (including Sc and Y)), R _1-x Sr _x MnO ₃ (where R: one or more rare earths (Sc and Y) ), 0 ≦ x ≦ 1), R
_1-x Ba _x MnO ₃ (where, R: one or more rare earth elements (including Sc and Y), 0 ≦ x ≦ 1), Ca _1-x R _x M
nO _3-y (where R: one or more rare earth elements (including Sc and Y), 0 ≦ x ≦ 1, 0 ≦ y), CaFeO ₃ ,
SrFeO ₃ , BaFeO ₃ , SrCoO ₃ , BaCo
O ₃ , RCoO ₃ (where R: one or more rare earths (including Sc and Y)), R _1-x Sr _x CoO ₃ (where R: one or more rare earths (including Sc and Y) ),
0 ≦ x ≦ 1), R _{1 −x} Ba _x CoO ₃ (where R: one or more rare earth elements (including Sc and Y), 0 ≦ x ≦
1), RNiO ₃ (where R: one or more rare earth elements (including Sc and Y)), RCuO ₃ (where R:
One or more rare earths (including Sc and Y)), RNb
O ₃ (where R: one or more rare earth elements (Sc and Y
The _{containing)), Nb 12 O 29,} CaRuO 3, Ca 1-x R x R
_{u 1-y Mn y O 3} ( wherein, R: one or more rare earth (S
c and Y), 0 ≦ x ≦ 1, 0 ≦ y ≦ 1), Sr
RuO ₃ , Ca _1-x Mg _x RuO ₃ (where 0 ≦ x ≦
1), Ca _1-x Sr _x RuO ₃ (where 0 <x <1),
BaRuO ₃ , Ca _1-x Ba _x RuO ₃ (where 0 <x
<1), (Ba, Sr) RuO ₃ , Ba _1-x K _x RuO ₃
(Where 0 <x ≦ 1), (R, Na) RuO ₃ (where R: one or more rare earth elements (including Sc and Y)), (R, M) RhO ₃ (where R : One or more rare earth elements (including Sc and Y), M = Ca, Sr, B
a), SrIrO ₃ , BaPbO ₃ , (Ba, Sr) P
bO _3-y (where 0 ≦ y <1), BaPb _1-x Bi _x O
₃ (where 0 <x ≦ 1), Ba _1−x K _x BiO ₃ (where 0 <x ≦ 1), Sr (Pb, Sb) O _3-y (where 0 ≦ y <1 ), Sr (Pb, Bi) O _3-y (where 0 ≦ y <1), Ba (Pb, Sb) O _3-y (where 0 ≦ y <1), Ba (Pb, Bi) O _3-y (where 0 ≦ y <1), MMoO ₃ (where M = Ca, S
r, Ba), (Ba, Ca, Sr) TiO _3-x (where 0 ≦ x) and the like.

Layered perovskite oxide (K ₂ NiF ₄₎
Type): R _{n + 1} Ni _n O _{3n + 1} (where R: Ba,
Sr, rare earth (including Sc and Y) one or more of, n = 1 to 5 _{integer), R n + 1 Cu n} O 3n + 1 ( where, R: Ba, Sr, rare earth (Sc and Y ), At least one of n = 1 to 5), Sr ₂ RuO
₄ , Sr ₂ RhO ₄ , Ba ₂ RuO ₄ , Ba ₂ RhO ₄
etc.

Pyrochlore type oxide: R_TwoV_TwoO_7-y(This
Here, R: one or more rare earth elements (including Sc and Y)
M), 0 ≦ y <1), Tl_TwoMn_TwoO_7-y (Where 0 ≦
y <1), R_TwoMo_TwoO_7-y (Where R: one or more
Rare earth (including Sc and Y), 0 ≦ y <1), R_TwoR
u_TwoO_7-y (Where R: Tl, Pb, Bi, rare earth
(Including Sc and Y), 0 ≦ y <
1), Bi_2-xPb_xPt_2-x Ru _xO_7-y (Where 0
≦ x ≦ 2, 0 ≦ y <1), Pb_Two(Ru, Pb) O_7-y 
(Where 0 ≦ y <1), R_TwoRh_TwoO_7-y (here,
R: Tl, Pb, Bi, Cd, rare earth (Sc and Y
), 0 ≦ y <1), R_TwoPd_TwoO_7-
y (Where R: Tl, Pb, Bi, Cd, rare earth (S
c and Y), 0 ≦ y <1),
R_TwoRe_TwoO_7-y (Where R: Tl, Pb, Bi, C
d, one or more of rare earths (including Sc and Y),
0 ≦ y <1), R_TwoOs_TwoO₇−_y (Where R: Tl,
Pb, Bi, Cd, rare earth (including Sc and Y)
At least one kind, 0 ≦ y <1), R_TwoIr_TwoO_7-y (here
And R: Tl, Pb, Bi, Cd, rare earth (Sc and
Y), 0 ≦ y <1), R_TwoPt_Two
O_7-y (Where R: Tl, Pb, Bi, Cd, rare earth
(Including Sc and Y), 0 ≦ y <
1) etc.

Other oxides: R ₄ Re ₆ O ₁₉ (where R: one or more rare earth elements (including Sc and Y)), R ₄ Ru ₆ O ₁₉ (where R: one or more kinds Rare earth (including Sc and Y)), Bi ₃ Ru ₃ O ₁₁ , V ₂
O ₃ , Ti ₂ O ₃ , Rh ₂ O ₃ , VO ₂ , CrO ₂ , Nb
O ₂ , MoO ₂ , WO ₂ , ReO ₂ , RuO ₂ , RhO
₂ , OsO ₂ , IrO ₂ , PtO ₂ , PdO ₂ , V ₃ O _{5
, V n O 2n-1 (} n = 4 to 9 integer), SnO _2-x
(Where 0 ≦ x <1), La ₂ Mo ₂ O ₇ , (M, M
o) O (wherein, M = Na, K, Rb , Tl), Mo n
O _3n-1 (n = 4, 8, 9, 10), Mo ₁₇ O ₄₇ , Pd
_1-x Li _x O (where x ≦ 0.1) and the like. An oxide containing In.

Among these, oxides containing In or conductive perovskite oxides are particularly preferable, and In ₂
O ₃ , In ₂ O ₃ (Sn doped), RCoO ₃ , RMn
O ₃ , RNiO ₃ , R ₂ CuO ₄ , (R, Sr) CoO ₃
, (R, Sr, Ca) RuO ₃ , (R, Sr) RuO ₃
, SrRuO ₃ , (R, Sr) MnO ₃ (R is a rare earth containing Y and Sc), and their related compounds are preferred. In general, a conductive oxide has a large work function and is preferable as a hole injection electrode. As the hole injection electrode layer, a thin film made of these materials, or a multilayer thin film of two or more of them is used. Most of perovskite oxides are opaque. In this case, a transparent or light-transmissive electrode is used as an electron injection electrode, and emitted light is extracted from the electron injection electrode side.

The device of the present invention may have a structure in which a substrate 1, a hole injection electrode 2, an inorganic material layer 4, an organic material layer 5, and an electron injection electrode 3 are sequentially stacked as shown in FIG. In addition, as shown in FIG.
A configuration may be adopted in which the layers are stacked in the reverse order of the organic layer 5 / the inorganic layer 4 / the hole injection electrode 2. These are appropriately selected and used depending on, for example, the structure of the display and the manufacturing process. In particular, when an opaque material is used for the hole injection electrode 2, the structure shown in FIG. 2 is preferable.
1 and 2, a drive power source E is connected between the hole injection electrode 2 and the electron injection electrode 3.

Further, the device of the present invention comprises an electrode layer / a layer exhibiting a light emitting function (an inorganic layer and an organic layer) / an electrode layer /
A layer / electrode layer exhibiting a light emitting function / a layer / electrode layer exhibiting a light emitting function may be stacked in multiple stages. With such an element structure, it is possible to adjust the color tone of the emitted light and to increase the number of colors.

Further, a large number of the elements of the present invention may be arranged on a plane. By changing the emission color of each element arranged on a plane, a color display can be obtained.

Further, in the present invention, it is preferable that a buffer layer is provided on a substrate having a Si surface, and a wurtzite type compound thin film is formed on the buffer layer.

A thin film made of a wurtzite type compound was
When trying to epitaxially grow directly on the i-substrate,
Since the surface of the Si substrate is very reactive, unnecessary compounds are formed before the epitaxial growth, which hinders the epitaxial growth of the wurtzite type compound. For example, when ZnO is used as a wurtzite type compound, amorphous Zn is formed on the Si surface before ZnO is epitaxially grown.
The O ₂ layer is formed to be thin, which may hinder epitaxial growth of ZnO. When a nitride such as AlN is used as the wurtzite type compound, a thin amorphous SiN layer is formed on the Si surface before the nitride grows, which hinders the epitaxial growth of the target nitride.

Therefore, in the present invention, it is preferable to provide a buffer layer on a substrate having a Si surface, and to form a wurtzite type compound thin film on this buffer layer. R-Zr-based oxide thin film, AlOx-based thin film, Na
A Cl-type nitride thin film is used. A buffer layer containing at least one of these thin films can be formed on a Si substrate as a thin film having high crystallinity and excellent surface flatness. Since the material constituting the buffer layer is similar in crystal structure and lattice constant to the wurtzite type compound, the wurtzite type compound such as the ZnO-based thin film or the AlGaInN-based thin film is interposed through the buffer layer. It becomes possible to form a thin film having a crystal structure as an epitaxial film on a Si substrate.

Therefore, according to the present invention, a high-quality large-diameter single crystal can be easily obtained, and a light-emitting element in which an epitaxial film made of a wurtzite compound exists on an extremely inexpensive Si substrate among single crystals. Can be obtained.

Since the Si single crystal substrate used in the present invention is less expensive than a sapphire substrate or a SiC single crystal substrate, an inexpensive Si substrate / inorganic layer structure can be realized.

FIGS. 3 to 6 show examples of the constitution of the inorganic layer particularly when the Si substrate of the present invention is used. The Si substrate / inorganic layer structure 20 shown in FIG. 3 has a buffer layer 22 and a wurtzite type compound thin film 23 on a Si single crystal substrate 21 in this order. The Si substrate / inorganic layer structure 20 shown in FIG. 4 is the same as that shown in FIG. 3 except that a wurtzite type compound thin film 23 and a metal thin film 24 are provided between the wurtzite type compound thin films 23. The Si substrate / inorganic layer structure 20 shown in FIG. 5 has a metal thin film 24 between a buffer layer 22 and a wurtzite type compound thin film 23, except that the structure shown in FIG.
Is the same as that shown in FIG. The Si substrate / inorganic layer structure 20 shown in FIG. 6 is the same as that shown in FIG. 3 except that a buffer layer 22 and a metal thin film 24 are provided between the buffer layers 22.

The buffer layer 22 is made of an AlOx-based thin film,
In the case of a laminated structure including two or more kinds selected from a Zr-based oxide thin film and a NaCl-type nitride thin film, the laminating order of each thin film is not limited, but preferably, an R-Zr-based oxide thin film is provided on the substrate side. . In the case of a configuration in which the metal thin film is divided into two layers like the wurtzite type compound thin film 23 in FIG. 4 and the buffer layer 22 in FIG. 6, the composition of the upper and lower layers may be the same or different. You may.

According to the present invention, when a wurtzite type compound thin film is formed on a Si single crystal substrate, a predetermined buffer layer is interposed between the two. Hereinafter, the reason why each of the thin films is used as the buffer layer will be described.

When two thin films are continuously formed, the degree of lattice mismatch between the underlying thin film (hereinafter referred to as an underlying thin film) and the thin film grown thereon (hereinafter referred to as a grown thin film) is as follows. , And the degree of mismatch. For example, if the lattice constant of the bulk body of the underlying thin film constituent material is d _sub and the lattice constant of the bulk body of the grown thin film constituent is d _epi , the mismatch degree δ (unit:%) is δ (%) = [ (D _epi −d _sub ) / d _sub ] × 100. If the lattice constant of the grown thin film is larger than that of the underlying thin film, δ will be a positive value. On the other hand, if δ is negative,
The lattice constant of the underlying thin film is larger than that of the grown thin film. When δ = 0, the lattices of the underlying thin film and the grown thin film match, that is, the lattices are perfectly matched. Regardless of the sign of δ, the larger the value of δ, the greater the degree of lattice mismatch, and it is not preferable because distortion, defects, and the like due to the lattice mismatch are likely to be introduced into the crystal.

When a wurtzite type compound thin film such as an AlN thin film is formed directly on a Si substrate, the relationship between the two crystals during epitaxial growth is Si [111] // AlN [000
1], the lattice constant in the Si (111) plane is 0.3
Since the lattice constant (lattice constant of the a-axis) in the AlN (0001) plane is 0.311 nm, the degree of mismatch δ is −1.
It becomes as large as 9.0%.

On the other hand, when an R—Zr-based oxide thin film such as a YSZ (stabilized zirconia in which Y is added to ZrO ₂ ) thin film is used as the buffer layer in the present invention, Y
The SZ crystal is usually cubic and its a-axis lattice constant (k) is 0.520 nm. Therefore, as shown in FIG.
The lattice constant (j) in the (111) plane (i) is 0.368 nm
And the lattice in the YSZ (111) plane (i) is AlN
Matching with the lattice in the (0001) plane, δ at that time is −
15.5%. Therefore, by providing the buffer layer made of the YSZ thin film on the Si substrate, the degree of mismatch is improved as compared with the case where the AlN thin film is directly formed on the Si substrate, and the AlN thin film can be formed as an epitaxial film. FIG. 7 is a lattice model showing the crystal structure of the YSZ cubic crystal, where a, b, and c indicate the a-axis, b-axis, and c-axis directions, respectively, i indicates the (111) plane, and j indicates the j-axis.
Represents the lattice constant in the (111) plane, and k represents the lattice constant of the a-axis (k = 0.5204 nm).

When the above-mentioned YSZ is used as the buffer layer and the GaN thin film is used as the wurtzite type compound thin film, the lattice in the YSZ (111) plane and the GaN (000)
1) The in-plane lattice (lattice constant 0.319 nm) matches,
At that time, δ becomes as small as −13.3%.

In place of YSZ, Yb ₂ O ₃ , Lu
_{When 2} O ₃ and Sc ₂ O ₃ are used, the lattice constants in the (111) plane are 0.3679 nm, 0.3674 nm, and 0.34 nm, respectively.
81 nm, and the matching with the GaN (0001) plane is further improved.

When TiN and ZrN are used in place of YSZ, the lattice constant in the (111) plane is 0.30 each.
0 nm and 0.326 nm, and the degree of mismatch with the GaN (0001) plane is extremely small at + 6.33% and -2.15%, respectively.

In the nitride semiconductor device using the Si substrate / inorganic layer structure of the present invention, a nitride semiconductor layer and a nitride layer serving as a base are formed on a wurtzite type compound thin film. These nitride layers are generally composed of Ga _x In _y Al _1-xy N (0 ≦ x ≦ 1, 0 ≦ x + y ≦
1) Since it is composed of a wurtzite type crystal having a composition represented by the following formula, the lattice matching with the wurtzite type compound thin film becomes extremely good. Specifically, a ZnO-based thin film used as a wurtzite type compound thin film and AlGaI
Constituent materials of the nN-based thin film, for example, ZnO crystal and AlN
In the crystal, the lattice constants in the (0001) plane are each 0.1.
325 nm and 0.311 nm, and when GaN is used for the nitride semiconductor layer or its underlying layer, the lattice in the (0001) plane of the wurtzite type compound thin film is GaN (0
(001) It matches with the lattice in the plane, and δ at that time is extremely small, −1.85% for ZnO and + 2.57% for AlN.

In the constituent material of the metal thin film, for example, a Pt crystal, the lattice constant in the (111) plane is 0.554 nm. This lattice is １ ／ and matches the lattice in the GaN (0001) plane, and δ at that time is as small as + 15.1%.
Even if a metal thin film is provided below or above the wurtzite type compound thin film, the crystallinity of the surface of the Si substrate / inorganic layer structure is hardly disturbed.

In the case of a buffer layer composed of a laminate of two or more thin films having different compositions and a buffer layer having a gradient structure in which the composition gradually changes in the thickness direction, the crystal lattice at the outermost surface of the buffer layer is Since the misfit of the crystal lattice of the wurtzite compound thin film made of the wurtzite compound can be further reduced, a wurtzite compound thin film having higher crystallinity can be formed. For example, (00) is placed on a buffer layer made of YSZ of (111) orientation.
When a wurtzite type compound thin film made of AlN of the (01) orientation is formed, δ is −15.5% as described above, but the buffer layer is made of a YSZ thin film and a ZrN thin film (NaC thin film).
(Al-Nitride thin film)
With the configuration in which the rN thin film is in contact, δ can be further reduced. The lattice constant of the a-axis of ZrN is 0.4
Since it is 61 nm, the lattice constant in the (111) plane in the ZrN film is (2 ^1/2 × 0.461) /2=0.326 nm. This lattice matches with the lattice in the AlN (0001) plane, and δ at that time becomes −4.6%, so that the degree of mismatch can be greatly improved.

The effect of the buffer layer having a laminated structure is not limited to the improvement of the degree of mismatch. For example, the stress of the entire thin film laminated structure can be reduced, and the characteristics of the Si substrate / inorganic layer structure can be improved (temperature characteristics can be improved). Etc.).

As described above, in the present invention, by forming a wurtzite type compound thin film on a Si substrate via a predetermined buffer layer, the degree of lattice mismatch can be reduced as compared with the case where a wurtzite type compound thin film is formed directly on a Si substrate. Is reduced, so that a wurtzite compound thin film made of a wurtzite compound having high crystallinity can be formed.

Next, the structure of the substrate and each thin film constituting the Si substrate / inorganic layer structure in the present invention will be described in detail.

Substrate A substrate having a Si single crystal on its surface is used. The substrate surface may be a (111) plane or a (100) plane of a Si single crystal.
It is preferable that it is composed of a plane,
It is preferable that it is composed of surfaces. Depending on conditions, cracks may occur in various thin films formed on the substrate, but the thickness of the substrate is preferably 10 to 100 μm.
By reducing the thickness to about m, more preferably about 25 to 75 μm, the occurrence of such cracks can be suppressed.

Buffer Layer In order to form a wurtzite compound thin film having high crystallinity, the buffer layer is preferably excellent in crystallinity and surface flatness. Specifically, the thin film constituting the buffer layer preferably has such crystallinity that the half width of the rocking curve of the reflection on the (111) plane by X-ray diffraction is 1.50 ° or less. When the surface property of the thin film constituting the buffer layer is represented by a surface roughness Rz (ten-point average roughness, reference length 500 nm) measured by AFM (atomic force microscope), Rz is preferably 2
nm or less, and more preferably 0.60 nm or less. In addition,
Such surface roughness is preferably 80% or more of the surface,
More preferably, it is desired to be realized in a region of 90% or more, and further preferably 95% or more. When the thin film is formed over the entire surface of the substrate, the surface roughness is 1 area.
Any 10 distributed on average over an area of 0 cm ² or more
It is a value obtained by measuring more than points. In the present specification, Rz of 2 nm or less at, for example, 80% or more of the surface of the thin film means that Rz is 8 when measured at 10 or more locations as described above.
It means that Rz is equal to or less than 2 nm at a location of 0% or more. The surface roughness Rz is specified in JIS B 0610.

There is no particular lower limit of the half width of the rocking curve and the lower limit of Rz in the thin film constituting the buffer layer, and the smaller the lower, the better. At present, the lower limit of the half width of the rocking curve is generally about 0.7 °, Especially 0.4
° and the lower limit of Rz is about 0.10 nm.

The RHE of the thin film constituting the buffer layer
When the ED image is streak and sharp, the thin film has excellent crystallinity and surface flatness. The same applies to other thin films such as a wurtzite type compound thin film and a metal thin film.

AlOx-based thin film The AlOx-based thin film is an epitaxial film containing Al and O as main components.

The AlOx-based thin film has a c-plane oriented parallel to the substrate, that is, a (0001) oriented film or (11)
1) An alignment film, preferably a single alignment film, more preferably an epitaxial film. A single orientation film is preferable because of its good crystallinity and surface properties, and an epitaxial film is more preferable because of its further excellent crystallinity and surface properties.

Note that a single alignment film in this specification is
When the measurement is performed by X-ray diffraction, the film has a peak intensity of reflection of an object other than the target surface of 10% or less, preferably 5% or less of the maximum peak intensity of the target surface.
For example, in a (0001) single orientation film, that is, a c-plane single orientation film, the intensity of the reflection peak other than the (000L) plane in the 2θ-θ X-ray diffraction is 10% of the maximum peak intensity of the (000L) plane reflection. % Or less, preferably 5% or less. Note that in this specification, (000L) is a general term for equivalent surfaces such as (0001) and (0002). Further, for example, the (111) single orientation film is a film in which the intensity of the reflection peak other than the (LLL) plane is 10% or less, preferably 5% or less of the maximum peak intensity of the (LLL) plane reflection. Note that (LLL) is a general term for equivalent surfaces such as (111) and (222).

Further, the epitaxial film in this specification refers to a crystal having an X-axis, a Y-axis, and a Z-axis when the film plane is the XY plane and the film thickness direction is the Z axis in the single orientation film. Both are aligned in the axial direction. Such an orientation can be confirmed by showing a spot or streak pattern in the RHEED evaluation. In addition, RHE
ED stands for Reflection High Ener
gy Electron Diffraction), and the RHEED evaluation is an index of the orientation of the crystal axis in the film plane.

The thickness of the AlOx-based thin film is preferably 1 to
It is 1000 nm, more preferably 3 to 50 nm. AlO
If the x-based thin film is too thin, it becomes difficult to form a uniform continuous film, and if it is too thick, it becomes difficult to obtain excellent surface properties.

R-Zr-based oxide thin film The R-Zr-based oxide thin film may be used alone as a buffer layer, or may be stacked as an AlOx-based thin film or a NaCl-type nitride thin film to form a buffer layer. When laminating, R-Z
The r-based oxide thin film is preferably provided as a base layer of an AlOx-based thin film or a NaCl-type nitride thin film. By providing an R-Zr-based oxide thin film as an underlayer, AlOx
The peeling of the base thin film and the NaCl type nitride thin film can be prevented. Further, the R-Zr-based oxide thin film has good lattice matching with the AlOx-based thin film and the NaCl-type nitride thin film. It assists in epitaxial growth and contributes to improving its crystallinity. However, AlOx-based thin films and NaC
When the l-type nitride thin film is relatively thin, the crystallinity of the AlOx-based thin film and the NaCl-type nitride thin film is improved without providing the R-Zr-based oxide thin film.

The R—Zr-based oxide thin film is made of a rare earth element (S
(including c and Y) and / or zirconium oxide.

Oxides of rare earth elements include Yb ₂ O ₃ and Tm ₂
O ₃ , Er ₂ O ₃ , Y ₂ O ₃ , Ho ₂ O ₃ , Gd ₂ O ₃ , Dy ₂ O
_{3, Tb 2 O 3, Pr} 2 O 3, Nd 2 O 3, CeO 2, Eu
It is preferably composed of ₂ O ₃ , Sm ₂ O ₃ , La ₂ O ₃ , Sc ₂ O ₃ or Lu ₂ O _3. Considering the lattice constant matching described above, Yb ₂ O ₃ , Sc ₂ O ₃ Or Lu ₂
More preferably, it is composed of O ₃ . The rare earth element oxide may be composed of a solid solution of two or more oxides selected from these. 2 rare earth elements
When containing more than one species, the ratio is arbitrary. Note that these oxides may deviate from the stoichiometric composition.

Zirconium oxide has a composition substantially equal to Zr.
O ₂ is preferred, but may deviate from the stoichiometric composition.

When the R—Zr-based oxide thin film is a solid solution of a rare earth element oxide and zirconium oxide, the solid solution ratio is arbitrary. However, in order to improve the surface flatness, it is preferable that the R-Zr-based oxide thin film be substantially composed of a rare earth element oxide or substantially composed of zirconium oxide. In the case where zirconium oxide is the main component, the higher the purity of zirconium oxide, the higher the insulation resistance and the smaller the leakage current. When zirconium oxide is the main component, the ratio of Zr in the constituent elements excluding oxygen in the thin film is preferably more than 93 mol%, more preferably 95 mol% or more, further preferably 98 mol% or more, and most preferably 99 mol% or more. 0.5 mol% or more. In the high-purity zirconium oxide thin film, constituent elements other than oxygen and Zr are usually rare earth elements, P, and the like. In addition,
The upper limit of the ratio of Zr is currently about 99.99 mol%. Also, with the current high-purity technology, ZrO ₂ and Hf
Since separation from O ₂ is difficult, the purity of ZrO ₂ is usually Z
It refers to the purity at r + Hf. Therefore, the purity of ZrO ₂ in the present specification is a value calculated by considering Hf and Zr as the same element, but HfO ₂ is exactly the same as ZrO ₂ in the R-Zr-based oxide thin film of the present invention. There is no problem to work.

An additive may be introduced into the R-Zr-based oxide thin film for improving the characteristics. For example, doping with an alkaline earth element such as Ca or Mg reduces pinholes in the film and can suppress leakage. Also, A
1 and Si have the effect of improving the resistivity of the film.
Further, transition elements such as Mn, Fe, Co, and Ni can form levels (trap levels) due to impurities in the film, and the use of these levels enables control of conductivity. .

The R-Zr-based oxide thin film needs to have a good lattice constant matching with the AlOx-based thin film or the wurtzite-type compound thin film. R-Zr-based oxide thin film
It is preferable to be composed of an epitaxial film of (111) orientation. However, since a metal thin film described later has a (111) orientation even when a base thin film has a (001) orientation, when a metal thin film is provided on an R-Zr-based oxide thin film, an R-Zr-based oxide thin film is used. The oxide thin film may be a (001) oriented thin film.

[0097] Of the R-Zr-based oxide thin films, the rare earth element oxide thin film has a (111) orientation whether formed on a Si (111) substrate or formed on a Si (100) substrate. When formed on a Si (100) substrate, it is preferable that the rare earth oxide thin film is composed of Pr ₂ O ₃ . By using Pr ₂ O ₃ , a thin film having high crystallinity can be obtained. On the other hand, among the R-Zr-based oxide thin films, the zirconium oxide thin film has a (111) orientation on a Si (111) substrate, but has a (001) orientation on a Si (100) substrate.

The preferred thickness of the R-Zr-based oxide thin film varies depending on the application, but is preferably 5 to 500 nm, more preferably 10 to 50 nm. The R-Zr-based oxide thin film is preferably thin enough not to impair its crystallinity, surface properties, and insulating properties. However, when the R-Zr-based oxide thin film is used as an insulating layer, the R-Zr-based oxide thin film has a thickness of about 10 to 500 nm. Are preferred.

The R-Zr-based oxide thin film may be a laminate of two or more thin films having different compositions, or may be a gradient structure film whose composition gradually changes in the thickness direction. .

NaCl-type nitride thin film The NaCl-type nitride thin film is composed of one selected from titanium nitride, niobium nitride, tantalum nitride and zirconium nitride, or is composed of a solid solution containing two or more of these. It is an epitaxial film.

When the NaCl-type nitride thin film is composed of a solid solution of two or more nitrides, the composition ratio of the nitride is arbitrary. The nitride contained in the NaCl-type nitride thin film may deviate from the stoichiometric composition.

The NaCl-type nitride thin film forms a wurtzite-type compound thin film having high crystallinity by preferably matching a lattice constant with a wurtzite-type compound thin film formed of a wurtzite-type compound formed thereon. Play a role. Since the wurtzite type compound thin film formed in contact with the NaCl type nitride thin film is hexagonal,
The NaCl-type nitride thin film is preferably an epitaxial film in which the (111) plane is oriented parallel to the substrate surface.

Incidentally, the NaCl type nitride thin film is made of Si (1
11) Form directly on the substrate or on the (111) oriented oxide buffer layer. In each case, NaC
The l-type nitride thin film becomes an epitaxial film of (111) orientation.

The preferable thickness of the NaCl type nitride thin film is as follows:
Preferably 5 to 500 nm, more preferably 10 to 50 nm
It is. The NaCl-type nitride thin film is preferably thin enough not to impair its crystallinity and surface properties.

The NaCl-type nitride thin film may be a laminate of two or more thin films having different compositions, or may be a gradient structure film whose composition gradually changes in the thickness direction.

Wolzite-Type Compound Thin Film A wurtzite-type compound thin film is an epitaxial film composed of a compound having a wurtzite-type crystal structure, and preferably has a (0001) plane oriented parallel to the substrate surface.

In the present invention, the use of a substrate having a Si (100) surface on the surface and the aforementioned (111) oriented R-Zr-based oxide thin film or the (111) oriented metal thin film described later is used. The crystal lattice relationship between the substrate and the wurtzite type compound thin film can be Si (100) // wurtzite type compound (0001) and Si (110) // wurtzite type compound (1-100). Therefore, the present invention is particularly suitable for application to a device manufactured using cleavage of a crystal.

In order to produce a high-performance Si substrate / inorganic layer structure, it is preferable that the wurtzite type compound thin film has excellent crystallinity and surface flatness. Specifically, the wurtzite type compound thin film preferably has such crystallinity that the half width of the rocking curve of reflection on the (0001) plane in X-ray diffraction is 2.50 ° or less. When the surface property of the wurtzite type compound thin film is represented by surface roughness Rz (ten-point average roughness, reference length 500 nm) measured by AFM (atomic force microscope), Rz is preferably 20 nm or less. , More preferably 1
0 nm or less. In addition, it is desirable that such surface roughness is realized in a region of preferably 80% or more, more preferably 90% or more, and still more preferably 95% or more of the surface. The surface roughness is a value obtained by measuring 10 or more arbitrary locations distributed on average over a region having an area of 10 cm ² or more when a wurtzite type compound thin film is formed over the entire surface of the substrate.

There is no particular lower limit of the half width of the rocking curve and the lower limit of Rz in the wurtzite type compound thin film, and the smaller the value, the better. .0
° and the lower limit of Rz is about 0.10 nm.

The flatness may be improved by polishing the surface of the wurtzite type compound thin film. For polishing, chemical polishing using an alkaline solution or the like, mechanical polishing using colloidal silica or the like, a combination of chemical polishing and mechanical polishing may be used. Such polishing may be performed on each layer other than the wurtzite type compound thin film.

The thickness of the wurtzite type compound thin film is preferably 5 nm to 50 μm, more preferably 0.5 to 10 μm.
It is. If the wurtzite type compound thin film is too thin, a high-performance Si substrate / inorganic layer structure cannot be obtained depending on the application. On the other hand, if the wurtzite type compound thin film is too thick, the productivity will be low.

The wurtzite type compound thin film may be a laminate of two or more thin films having different compositions, or may be a gradient structure film whose composition gradually changes in the thickness direction.

The composition of the wurtzite type compound thin film is not particularly limited, and may be appropriately determined so as to obtain the characteristics required for the intended Si substrate / inorganic layer structure. For example, since the lattice constant and the thermal expansion coefficient can be adjusted by the composition, the composition may be selected according to the lattice constant and the thermal expansion coefficient of the thin film formed on the Si substrate / inorganic layer structure. However, preferably, AlGaIn described below is used.
A wurtzite type compound thin film of an N-based thin film, a ZnO-based thin film, or a sulfide film is used.

The AlGaInN-based thin film The AlGaInN-based thin film is an epitaxial film mainly containing at least one selected from Al, Ga and In and N and having a wurtzite type crystal structure.

Although the composition of the AlGaInN-based thin film is not particularly limited, Ga _x In _y Al _1-xy N (0 ≦ x ≦
It is preferable to have a composition represented by 1, 0 ≦ x + y ≦ 1).

The ZnO-based thin film The ZnO-based thin film contains zinc oxide as a main component, and is preferably substantially composed of ZnO.

Sulfide Film The sulfide film contains cadmium sulfide or zinc sulfide as a main component, and is preferably substantially composed of CdS or ZnS.

The reason for providing a metal thin film is as follows. In the Si substrate / inorganic layer structure of the present invention, the metal thin film mainly functions as an electrode. In a light emitting device using a wurtzite type compound thin film such as ZnO or AlN, a function is exhibited by applying an electric field in the thickness direction of the film. In such applications, an electrode is required below the membrane. In light-emitting elements such as LEDs and laser diodes, high luminance is important. Higher luminance can be achieved by improving the quality of the semiconductor thin film. However, if a function of reflecting emitted light is provided in the element, higher luminance may be easily achieved. For example,
By disposing a thin film serving as a reflection layer at an appropriate position in the device, it is possible to promote emission of light emission to the outside of the device. The metal thin film in the present invention can function as such a reflective layer. In addition, since the metal thin film plays a role of absorbing stress in the thin film laminate, the metal thin film also has an effect of preventing cracking of the thin film formed on the metal thin film.

The metal thin film plays a role of forming a thin film having high crystallinity by preferably matching a lattice constant with a thin film formed thereon. For this purpose, it is preferable that the metal thin film be excellent in crystallinity and surface flatness like the above-described R-Zr-based oxide thin film.

The metal thin film is basically composed of a cubic crystal or a hexagonal crystal and has a (111) plane or a (00) plane parallel to the film plane.
01) It is an epitaxial film whose plane is oriented. However,
The crystal may be deformed by the stress and become a crystal deviated from cubic or hexagonal, such as tetragonal. Note that (11
1) In order to form an oriented metal thin film, the R-Zr-based oxide thin film provided thereunder may have either a (111) orientation or a (001) orientation. In each case, the metal thin film has a (111) orientation. In addition, in order to form a metal thin film having a (0001) orientation, it is usually preferable that the R-Zr-based oxide thin film provided thereunder has a (111) orientation. It is possible that the metal thin film has (0001) orientation.

The position where the metal thin film is provided is not particularly limited.
As shown in FIGS. 4 and 5, on the wurtzite-type compound thin film, in the wurtzite-type compound thin film, between the buffer layer and the wurtzite-type compound thin film, or in the buffer layer, the light-emitting device may be used. What is necessary is just to determine suitably according to it.

The metal thin film is made of Pt, Ir, Os, Re, P
It is preferable that at least one of d, Rh, and Ru is a main component, and it is preferable that the metal is composed of a simple substance of these metals or an alloy containing these metals. Note that P
t, Ir, Pd and Rh become cubic, and Os, Re
And Ru are hexagonal.

Although the thickness of the metal thin film varies depending on the application, it is preferably 5 to 500 nm, more preferably 50 to 150 nm.
It is preferable that the thickness be as thin as not to impair the crystallinity and surface properties. More specifically, in order to function sufficiently as a reflecting mirror, the thickness is preferably 30 nm or more, and sufficient reflectivity is obtained with a thickness of 100 nm or less. In order to function sufficiently as an electrode, the thickness should be 50
It is preferable to set it to 500 nm.

Manufacturing Method In manufacturing the light emitting device of the present invention, the method of forming each thin film is not particularly limited, but the formation of the buffer layer and the metal thin film is described in JP-A-8-109099 by the present applicant. It is preferable to use an evaporation method according to the above method. For forming the wurtzite type compound thin film, a sputtering method or an MOVPE (metal organic chemical vapor deposition) method is preferably used, and particularly, a sputtering method is preferably used. In the MOVPE method, the substrate temperature is 1000
Although the temperature needs to be as high as about ° C, according to an experiment by the present inventors, it is possible to form a highly crystalline wurtzite type compound thin film at a substrate temperature of about 600 ° C by the sputtering method. Also, the sputtering method is different from the MOVPE method,
The internal stress of the thin film can be controlled under various conditions, such as gas pressure,
Since it can be freely controlled by the distance between the targets, the input power, and the like, it is easy to reduce the internal stress.

As a substrate on which a thin film laminate comprising a buffer layer, a wurtzite type compound thin film, and a metal thin film provided as needed, is provided, a Si single crystal wafer is usually used. Si single crystal wafers have a large area, for example, 10
Since it is easy to have an area of ² cm ² or more, and it is extremely inexpensive as a single crystal, the production cost of the Si substrate / inorganic layer structure of the present invention can be extremely low. At present, semiconductor process using 2-8 inch Si wafer,
In particular, the 6-inch type is mainly used, but such a semiconductor process can be used for manufacturing the Si substrate / inorganic layer structure of the present invention. Note that a structure may be employed in which a thin film laminate is formed only on a part of a wafer using a mask or the like.

In the Si substrate / inorganic layer structure of the present invention, the substrate surface, that is, the surface on which the buffer layer is formed is oxidized shallowly (for example, about 5 nm or less in depth) to form an oxide layer such as SiO _2. . Such an oxide layer is formed by diffusion of oxygen in the oxide present in the thin film stack to the substrate surface. Further, at the time of forming the thin film laminate, the surface of the substrate is oxidized depending on the forming method.

[0127]

EXAMPLES Hereinafter, the present invention will be described in more detail by showing specific examples of the present invention. Example 1 A light emitting device having a structure as shown in FIG. 2 was manufactured. TPD was used for the organic compound for hole injection / transport of the organic layer, and a ZnO thin film was used for the inorganic layer.

As a glass substrate, product name 7 manufactured by Corning Incorporated
The 059 substrate was scrub-cleaned using a neutral detergent.

An AZO (Al-added ZnO) electron injecting electrode layer having a thickness of 200 nm was formed on this substrate at a substrate temperature of 250 ° C. by using an oxide target in which Al was added to ZnO at 1 wt% by an RF magnetron sputtering method.

Next, without breaking the vacuum, a substrate temperature was set to 350 ° C., a ZnO (99.9%) target was used, and a 200 nm thick ZnO thin film was formed by RF magnetron sputtering using an Ar gas. did.

According to X-ray diffraction, it was found that the ZnO thin film was a polycrystalline thin film having a wurtzite type crystal structure strongly oriented in the C axis. The resistivity of the ZnO thin film is 5
It was 0 Ωcm, and it was found from the measurement of the Seebeck coefficient that the film was an n-type semiconductor film, and the bandgap was 3.1 eV from the light transmission characteristics.

Here, the ZnO thin film was taken out for evaluation. In actual device fabrication, after the ZnO thin film was formed, the substrate temperature was cooled to room temperature and the TPD was deposited by resistance heating to break the vacuum. A thin film was formed to a thickness of 70 nm.

Further, as a hole injection electrode, a Pt electrode film was formed to a thickness of 50 nm by a sputtering method. The electrode area was 1 mm ² .

From the obtained structure, electrodes were drawn from the hole injection electrode and the electron injection electrode using a probe electrode in a vacuum, and an electric field was applied. The VI characteristic shows a diode characteristic. When the Pt side is biased positively and the AZO side is biased negatively, the current increases as the voltage increases, and a clear green light emission is observed in a normal room. Further, even when the light emitting operation was repeatedly performed, no decrease in luminance was observed.

Example 2 In the same manner as in Example 1, a light emitting device in which the stacking order was upside down was manufactured. At this time, a ZnO epitaxial thin film was used as the inorganic layer. Here, Si was used as the substrate.

First, Japanese Patent Application No. 7-21985 of the present inventors.
0, ZrO ₂ according to the method of Japanese Patent Application No. 7-24060.
Was produced as follows.

As a single crystal substrate on which a ZrO ₂ thin film was grown, an Si single crystal wafer cut and mirror-polished so that the surface became a (111) plane was used. After the purchase, the mirror surface was cleaned by etching with a 40% ammonium fluoride aqueous solution. Note that a circular substrate having a diameter of 2 inches was used as the Si substrate.

After fixing the single crystal substrate to a substrate holder provided with a rotation and heating mechanism installed in a vacuum chamber, evacuating the vacuum chamber to 10 ⁻⁶ Torr by an oil diffusion pump, and cleaning the substrate cleaning surface with Si oxide To protect with a material,
Rotate at 0 rpm, oxygen is supplied from the nozzle near the substrate by 25 cc.
/ Minute while heating at 600 ° C. Here, a Si oxide film is formed on the surface of the substrate by thermal oxidation.
By this method, a Si oxide film of about 1 nm was formed.

Subsequently, the substrate was heated to 900 ° C. and rotated. The rotation speed was 20 rpm. At this time,
By introducing oxygen gas from the nozzle at a rate of 25 cc / min and evaporating metal Zr from the evaporation source onto the substrate,
It was supplied so as to have a thickness of 5 nm in terms of the thickness of the Zr metal oxide, and a Si surface-treated substrate having a 1 × 1 surface structure was obtained.

Further, the metal Zr was supplied from the evaporation source onto the Si surface-treated substrate in a state where the substrate temperature was 900 ° C., the substrate rotation speed was 20 rpm, and oxygen gas was introduced from the nozzle at a rate of 25 cc / min. _Two epitaxial films were obtained on the processing substrate.

Subsequently, the substrate on which ZrO ₂ was formed
Heated to 00 ° C. and rotated. The rotation speed was 20 rpm.
The degree of vacuum was evacuated to 10 ^-7 Torr by an oil diffusion pump.

On this substrate, a Pt electrode was formed. Pt
Was evaporated using an electron beam to form an electron injection electrode film having a thickness of 100 nm.

As a result of RHEED observation, it was found that the Pt thin film was an epitaxial film.

Then, without breaking the vacuum, a ZnO thin film having a thickness of 200 nm was formed by RF magnetron sputtering using a target of ZnO (99.9%) at a substrate temperature of 600 ° C. and Ar + oxygen gas. Formed.

According to X-ray diffraction, the ZnO thin film has a wurtzite type crystal structure strongly oriented in the C axis, and
As a result of the observation, it was found that the film was an epitaxial film.

Further, the resistivity of the ZnO thin film is 5 Ωcm, and it is an n-type semiconductor film from the measurement of the Seebeck coefficient.
The light transmission characteristics revealed that the band gap was 3.15 eV.

Here, the thin film was taken out for evaluation of the thin film. However, in the actual device fabrication, after the thin film was formed, the substrate temperature was cooled to room temperature, and the TPD thin film was formed by resistance evaporation to break the vacuum. 70 nm was formed.

Further, as an electron injection electrode, an ITO hole injection electrode film was formed to a thickness of 50 nm by a sputtering method. The electrode area was 1 mm ² .

From the obtained structure, electrodes were pulled out of the ITO thin film and the Pt electrode film using a probe electrode in a vacuum, and an electric field was applied. The VI characteristic shows a diode characteristic. When the ITO thin film side is biased positive and the Pt side is biased negatively, the current increases as the voltage increases, an injection current is observed, and a clear green color appears in a normal room. Luminescence was observed. Further, even when the light emitting operation was repeatedly performed, no decrease in luminance was observed.

The effects of the present invention are apparent from the results of the above examples. Thus, according to the present invention, there is provided a novel and improved organic / organic material having a clear luminescent property in a room.
The present invention can provide a semiconductor light emitting device, and has a great practical value particularly for low-cost LEDs and high-performance flat-panel color displays.

[0151]

As described above, according to the present invention, it is possible to provide a novel and improved semiconductor light emitting device with improved efficiency, low operating voltage, large design freedom, and increased reliability.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a two-layer organic thin film light emitting device having a hole transport layer according to a conventional example and the present invention.

FIG. 2 is a cross-sectional view of a three-layer organic thin-film light emitting device having a hole transport layer and an electron transport layer according to a conventional example and the present invention.

FIG. 3 is a schematic view showing a first configuration example of a Si substrate / inorganic layer structure according to the present invention.

FIG. 4 is a schematic diagram showing a second configuration example of the Si substrate / inorganic layer structure according to the present invention.

FIG. 5 is a schematic diagram showing a third configuration example of the Si substrate / inorganic layer structure according to the present invention.

FIG. 6 is a schematic diagram showing a fourth configuration example of the Si substrate / inorganic layer structure according to the present invention.

FIG. 7 is a schematic diagram for explaining a lattice constant of a YSZ cubic crystal.

FIG. 8 is a cross-sectional view of a two-layer organic thin-film light emitting device having a hole transport layer according to a conventional example and the present invention.

FIG. 9 is a cross-sectional view of a three-layer organic thin-film light emitting device having a hole transport layer and an electron transport layer according to a conventional example and the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Hole injection electrode 3 Electron injection electrode 4 Inorganic layer 5 Organic layer 11 Substrate 12 Hole injection electrode 13 Electron injection electrode 14 Hole transport layer 15 Light emitting layer 16 Electron transport layer 21 Substrate 20 Electronic device substrate 22 Buffer layer 23 Inorganic layer 24 Metal thin film

Claims (8)

[Claims] 1. A structure having at least an inorganic layer and a hole transporting organic layer laminated on a substrate, wherein the inorganic layer has an oxide film having a wurtzite type crystal structure and / or a wurtzite type crystal structure. Semiconductor light-emitting device, which is a nitride film having a structure and / or a sulfide film having a wurtzite type crystal structure. 2. The semiconductor light emitting device according to claim 1, wherein said inorganic layer is an n-type semiconductor layer. 3. The semiconductor light emitting device according to claim 1, wherein said inorganic layer is an epitaxial film. 4. The semiconductor light emitting device according to claim 1, wherein said substrate is a Si single crystal substrate. 5. The substrate has at least a single-crystal Si surface, and has a buffer layer between the substrate and the inorganic layer. The buffer layer may be an oxide buffer layer and / or a nitride buffer layer. Wherein the oxide buffer layer has an R-Zr-based oxide thin film which is an epitaxial film mainly containing an oxide of a rare earth element (including Sc and Y) and / or zirconium oxide, An AlOx-based thin film that is an epitaxial film containing O as a main component; and the nitride buffer layer is an NaCl-type nitride film that is an epitaxial film containing at least one of titanium nitride, niobium nitride, tantalum nitride, and zirconium nitride as a main component. The semiconductor light-emitting device according to claim 1, further comprising an object thin film. 6. The semiconductor light emitting device according to claim 1, wherein said inorganic layer has a ZnO-based thin film containing zinc oxide as a main component. 7. A metal thin film is provided between the buffer layer and the n-type semiconductor layer of the inorganic layer or in the buffer layer, and the metal thin film is made of Pt, Ir, Os, Re, Pd, Rh.
The semiconductor light emitting device according to claim 1, wherein the semiconductor light emitting device is an epitaxial film containing one or more of Ru and Ru as a main component. 8. The semiconductor light emitting device according to claim 7, wherein said metal thin film has a (111) plane or a (0001) plane oriented parallel to a substrate surface.