JPS6254482A - Light emitting element - Google Patents

Abstract

PURPOSE:To improve light emitting efficiency and reproducibility, by forming a layer as multilayer structure constituted by laminating periodically a unit of the first layer region composed of amorphous silicon containing by hydrogen atom and the second layer region whose optical band gap is different from the first layer region. CONSTITUTION:A light emitting element is constituted of a lower electrode 102 formed on a substrate 101, a lower insulating layer 103, a light emitting layer 104, an upper insulating layer 105 and an upper electrode 106 formed on insulating layer 105. The first layer region I where a light emitting layer is composed of a non-Si:H and the second layer region whose optical band Eg opt is different from that of the first layer region I are united into a unit which is laminated periodically to constitute a multilayer structure. As to the first layer region I and the second layer region II, each of their thickness is selected so as to exhibit the size-effect in quantum mechanics, and they are alternately laminated to constitute a superlattice structure. The optical band gap Eg opt II of the second layer region II is made larger than the optical band gap Eg opt I of the first layer region I.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a light source used in O, A equipment, etc. or a light emitting element used for display.

[Conventional technology]

Conventionally, various materials have been reported as materials constituting the light emitting layer of light emitting devices, among which, for example, Appl.
, Phys, 'Lett.

29 (1976), PP620-622. J.

1. Pankou, D., E. Carlson.

Jpn, J., Appl, Phys, 21 (1982)
PP473-475. Non-single crystal silicon containing hydrogen atoms (hereinafter referred to as
rnon-5i (denoted as HJ) is being poured because it can be applied with semiconductor engineering similar to single-crystal silicon and may have superior latent properties. It is one of the materials.

The structure of the light-emitting device using non-5i:H as a light-emitting material described in the cited document 1- is: a P-type conductive layer (P layer) containing p5 impurity, and either P-type or N-type impurity. It has a homojunction in which a layer containing no impurities (non-doped layer) and an N-type conductive layer (N layer) containing N-type impurities are laminated.

[Problem to be solved]

However, conventionally reported light-emitting devices with such configurations do not emit a sufficient amount of light in the visible light region, and in addition, have low emission intensity and short lifetime.1. There are many points that need to be improved in practical terms.

1-Numerical idea (7) As one, add a carbon atom to non-3t:H to widen the optical band gap, ii
Attempts have been made to obtain light in the f-visual wavelength region, but there are still problems in practical use, and it has not yet been industrialized as a light source element or display element used in 0, A equipment, etc. not present.

The main object of the present invention is to provide a light emitting device that improves the drawbacks of the conventional bipedal light emitting device.

Another aspect of the present invention is that sufficient light emission in the visible wavelength region is achieved.
- It is an object of the present invention to provide a light-emitting element having 5-5 improvements in luminous efficiency and reproducibility.

Another feature of the present invention is the stability of luminescent properties.
The objective is to provide a light emitting device that dramatically improves life.

[Means for solving problems]

The light emitting device of the present invention has a light emitting layer, a pair of electrically insulating layers sandwiching the light emitting layer, and at least one pair of electrodes sandwiching the light emitting layer and the insulating layer and electrically connected to each other, At least one of the three layers constituting the light emitting layer includes a first layer region made of non-single crystal silicon containing hydrogen atoms, and a second layer region having a different optical band gap from the first layer region. , is characterized by having a multilayer structure in which these are periodically stacked as one unit.

[For production]

By having the above structure, the light emitting element of the present invention has the following features:
It has a luminescence peak in the visible wavelength region, obtains a sufficient amount of luminescence, improves luminous efficiency and reproducibility, and dramatically improves the stability of luminescent characteristics and lifespan.

Hereinafter, the present invention will be specifically explained with reference to the drawings.

FIG. 1 is a schematic layer structure diagram showing the layer structure of a preferred embodiment of the light emitting device of the present invention.

The light emitting device shown in FIG.
It is composed of a negative electrode 106 provided above and a partial electrode 106.

When the light emitting device shown in FIG. 1 is used as a planar light emitting device, the electrode 102 or/and 1 [pole 106 must be transparent if the color of the emitted light is to be utilized. If a light-emitting layer is to be used, it is desirable that the layer be transparent to emitted light. When emitting light is extracted from the electrode 102 side, it is desirable that the substrate 101 be transparent like the electrode 102 or translucent to the emitted light.

The light-emitting element of the present invention has a light-emitting layer that is non-conductive as described in Section 111j.
- A first layer region (I) composed of Si:H and a second layer region (II) having an optical bandgap Egopt different from that of the layer region (I). It has a multilayer structure in which layers are stacked periodically. In order to achieve the effects of the present invention even more effectively, the first layer region (I) stacked in one periodic structure should be replaced with the second layer region (II).
), the respective layer thicknesses are selected such that the premechanical size effect occurs, and the layers are stacked alternately, and 1) an IT superlattice structure is constructed.

Optical bandgap Ego of the second layer region (II)
pt(II) is preferably larger than the optical/hand gap Egopt(I) of the first layer region (I), i.e. the second layer q1 region (II) has a potential of 4
Materials are selected and layers are formed to fulfill the role of the 97 layers.

In the light emitting device of the present invention, the semiconducting intermediate layer 104 is an I-type conductive layer exhibiting intrinsic semiconductor characteristics, or an I-type conductive layer with a slight N content.
It is formed as a type or P-type conductive layer. And non-
Due to its general tendency, the layer composed of Si:H has a so-called P
When neither type nor N-type impurities are contained, the layer exhibits a slight N-type tendency, so in order to form an I-type conductive layer, a slight amount of P-type impurity is contained.

FIG. 2 shows the first layer region (I) 201 and the second layer region (I) 201.
An example of a layer structure in which layer regions (II) 202 are alternately laminated in n periods with a suitably desired layer thickness is shown.

The second layer region (II) 202 is the first layer region (I) 2
01, the larger optical bandgap Egop
t, the first layer region (I) 201 and the second layer region (
II) A Peter junction is formed at the junction with 202. , as the material 4 constituting the second layer region (II) 202.

Optical bandgap Egop than non-St:H
Non-single-crystalline semiconductor materials with a larger t or non-single-crystalline electrically insulating materials may be used. The material constituting these second layer regions (II) 202 is the same as that of the first layer region (II) 202.
I) Although the chemical composition elements or chemical composition ratios are different from those of the material 1 constituting 201, it is better to have the same base constituents to improve the luminescent properties more effectively. It can be measured.

In the present invention, the respective layer thicknesses of the first layer region (I) 201 and the second layer region (II) 202 for introducing a superlattice structure depend on the materials constituting each layer region and requirements. It is determined as appropriate and desired depending on the element characteristics to be used.
It is desirable that it be determined so that the quantum size effect becomes noticeable.

The layer thickness of the first and second layer regions is preferably 5
~100 people, more preferably 8~80 people, optimally 1 person
It is desirable that the number be 0 to 70 people. In particular, it is desirable that the distance be approximately the de Broglie wavelength of the carrier or approximately the mean free path of the carrier. When introducing the above superlattice structure into the semiconductor intermediate layer 104, specifically, for example, the first layer region (I) 201 is formed using a so-called layer containing neither P-type nor N-type impurities. Non-doped non-
As the St:H layer, the non-Si:H layer of air containing a small amount of P-type impurity and made into an intrinsic semiconductor, and the second layer region CI layer 202, hydrogen atoms - (H) are added as necessary.
A semiconducting or electrically insulating non-single crystal material (hereinafter referred to as
(abbreviated as "rnon-SiN(H)"), or silicon atom (Si) containing a hydrogen atom (H) as necessary
and MJ atoms (0) (hereinafter abbreviated as rnOn-5iO(H)).

The first layer region (I) 201 and the second layer region (II) 202 made of these materials are preferably laminated alternately in ten to several dozen cycles with respective layer thicknesses. Ru.

The hydrogen atoms (H) contained in the first layer region (I) are
The content of t compensates for free dangling bonds of silicon atoms, and its content is a modifying factor that affects the semiconductor properties, optical properties, and light emitting properties of the device. The content of H) is preferably 0.1 to 40 atomic % based on silicon atoms, more preferably 0.5
~35 atom %, optimally 1-3o atom %.

In the present invention, the above-mentioned structure can be overcome by adopting the photo-CVD method (deposited film formation method by chemical vapor phase method using light energy for reaction). It is desirable to select and use a raw material '1 that is compatible with the photo-CVD method.

The first (7) layer region (I) 201 is composed of non-5i:H, but preferably 81′i intrinsic (
From its general tendency, a layer composed of non-5i:H, which is preferably created as a layer exhibiting the semiconductor properties of air), contains only a slight amount of N if it does not contain MP-type or N-type impurities. Since it shows a type tendency, the first layer region (I) 20
In order to make 1 an I-type conductive layer, a small amount of P-type impurity is contained.

The first layer region (I) 201 may be a so-called non-doped layer that does not contain P-type or N-type impurities, although the light-emitting characteristics are slightly degraded.

In order to make the first layer region (I) 201 a conductive layer, it is necessary to contain a P-type impurity that gives P-type conductivity when forming the layer, or to add a P-type impurity to the layer already composed of non-5i:H. Then, P-type impurities may be implanted by means such as ion implantation.

The P-type impurity is an atom belonging to the so-called group Ⅰ of the periodic table (group Ⅰ atom), that is, B (boron).

Al (aluminum), Ga (gallium).

There are In (indium), T4 (thallium), etc., and B and Ga are particularly preferably used.

The materials constituting the electrically insulating layers 103 and 105 include:
Almost any material can be used as long as it has good electrical insulation properties, does not have a negative effect on efficiently extracting the light emitted from the light emitting layer 104 to the outside, and is easy to form. I can do it.

Either one of the insulating layers 103 and 105 needs to be transparent with respect to one light-emitting layer in order to extract the light emitted to the outside. In the present invention, specifically, Y2O3 is preferably used as a material constituting the insulating layers 103 and 105.
, 5i02. Amorphous silicon oxide (a-SiX01-
X However, 0<x<1), HfO2.

Si3N4. Amorphous silicon nitride (a-3iyN1-
y However, o<y<t), A-texture 203, PbTiO3, amorphous (7) BaTi03°Ta205, etc. can be mentioned.

FIG. 3 shows another preferred embodiment of the light emitting device of the present invention.

The light emitting device shown in Fig. 3 has a structure that is the first in terms of the S tree.
It is similar to the light emitting element shown in the figure.

The light emitting element shown in Fig. 3 is made of transparent material such as glass (body 3
01, transparent 1 electrode 302. Lower insulating layer 3031
Light emitting layer 304. It has a layered structure in which a seventh insulating layer 305° and a metal electrode 306 are laminated, and an electric Th 302 and a metal electrode 30
6 are electrically connected to connection terminals of a power source 307 for applying a pulse-like or sawtooth-like high frequency high electric field, respectively.

In the case of the light emitting device shown in FIG. 3, when a high frequency electric field is applied by a high frequency power supply 307, light is emitted from the light emitting layer 304, and the emitted light is transmitted to the insulating layer 303, the transparent electrode 302,
), (transmits through the air 301 and is released to the outside.

In the light emitting device of the present invention, in order to obtain an emission wavelength in the visible range, it is desirable that the optical band gap Egopt of the first layer region (I) is 2.0 eV or more.

Further, the localized position density at the center of the optical band gap (mid gap) of the first layer region (I) is preferably I
X 1016 cm-3 fist e V-1 or less, more preferably I x 1015 cm-3 e V-1.

In this way, by controlling the physical property values of the first layer region (I), it is possible to dramatically improve the recombination efficiency, and therefore it is possible to measure the direction of the luminous efficiency. .

In addition, the child efficiency is 10-4% outside the first layer region (I).
By controlling the recombination and usable portion 1HT so as to achieve the above, a light emitting element that emits light with high intensity can be obtained.

It is desirable that the light emitting element having the above-mentioned characteristics be produced by the photo-CVD method under the conditions described below, as described in j) η. The method for producing a light emitting device of the present invention is provided as long as the object of the present invention is achieved.

The method is not limited to the photo-CVD method, and the method can be set to desired conditions as appropriate, such as HOMOCVD horn 1. Plasma C
This may also be done by a VD method or the like.

As the material constituting the substrate constituting the light emitting device of the present invention, most of the materials commonly used in the field of light emitting devices can be mentioned.

(The body may be electrically conductive or electrically insulating, but it is desirable that it has relatively excellent heat resistance.)

Conductivity), (in the case of a body), (an electrode provided between the body and the light emitting layer) is not necessarily provided.

As the conductive substrate, NiCr, stainless steel, A f
L, Cr, Mo, Au, Nb
, T a.

V, Ti, etc. can be mentioned.

Electrically insulating substrates include polyester, polyethylene, polycarbonate, and polyamide.

Examples include films or sheets of synthetic resins, glass, ceramics, and the like.

J. (If an electrically insulating material is used as the body,
Its surface is subjected to conductive treatment to serve as an electrode between the light emitting layer and the light emitting layer.

For example, if it is glass, NiCr, AM
, Cr, Mo, Au, Ir, Nb.

Ta, V, Ti, Pt, Pd, In2O3゜5n02
, ITO (In203+5n02), etc. to give conductivity, or if it is a synthetic resin film such as polyester film, NiCr,
All, Ag.

Pb, Zn, Ni, Au, Cr, Mo, Ir.

A thin film of metal such as Nb, Ta, V, Ti, Pt, etc. is provided on the surface by vacuum deposition, electron beam evaporation, sputtering, etc., or the surface is laminated with the above metal to make the surface conductive. Granted.

A specific example of the method for producing a light emitting element of the present invention will be described below using a photo-CVD apparatus shown in FIG. It goes without saying that the production means and production conditions described below are only preferred examples and do not limit the present invention.

In FIG. 3, l is a deposition chamber, and a desired substrate 3 is placed on a substrate support 2 inside.

Reference numeral 4 denotes a heater for heating the substrate, which is supplied with electricity via a conductor Vj5 and generates heat. Although the substrate temperature is not particularly limited, it is generally desired to be 200'C or less in order to obtain visible light emission by narrowing the optical band gap of the light emitting layer.

6 to 9 are gas supply sources, and if a liquid raw material is used in a normal state, an appropriate vaporizer is provided.

The vaporizer may be of any type, such as a type that uses heating and boiling, or a type that allows a carrier gas to pass through the liquid raw material.

The number of gas supply sources is not limited to four, and the original document used =
The number of types of I substances, the diluent gas, etc. to be used are appropriately selected depending on whether or not the diluent gas and the raw material gas are premixed. In the figure, the symbols for gas supply sources 6 to 9 are
The ones with a are branch pipes, the ones with b are flow meters, the ones with C are pressure gauges that measure the pressure on the high pressure side of each flow meter, and the ones with d or e are each gas flow. This is a valve for opening/closing and adjusting the flow direction.

Gaseous raw materials supplied from each gas supply source are mixed in the middle of the gas introduction pipe 10, energized by a ventilation device (not shown), and introduced into the chamber 1. Alternatively, the gases are introduced into the chamber 1 alternately from each gas supply source. 11 is the total IIE force of the gas introduced into the chamber 1, Δ11! It is a pressure gauge for Further, 12 is a gas exhaust pipe, which is connected to an exhaust device (not shown) for reducing the pressure inside the deposition chamber 1 and forcibly exhausting introduced gas.

13 is a regulator valve. When the inside of the chamber 1 is evacuated and the pressure is reduced to 1 mm before introducing the raw material gas etc., the pressure inside the chamber is preferably 5X10-5 Torr or less, more preferably 1X10-[1 Torr or less. Delicious.

In addition, with the raw material gas etc. introduced, chamber 1
The pressure inside is preferably 1X10-2 to 100 Torr.
, more preferably 5×10 −2 to 10 Torr.

As an example of the excitation energy supply source used in the present invention,
Reference numeral 14 denotes a light energy generator, for example, a mercury lamp, a xenon lamp, a carbon dioxide laser, an argon ion laser, an excimer laser, or the like. It should be noted that the light energy used in the present invention is not limited to ultraviolet energy, and any wavelength range may be used as long as it can cause a chemical reaction in the raw four gases and form a deposited film.

Light 15 is directed from the light energy generating device 14 to the entire substrate or a desired portion of the substrate using an appropriate optical system, and is irradiated onto the gas of the raw material flowing in the direction of the arrow 16.

Specifically, as an example of producing a light emitting device, first, a glass substrate (C#7059) is used as a base, and an ITO layer with a thickness of 600 mm is formed as a conductive layer thereon by sputtering. The resistance value of the membrane is approximately 50Ω/hole.

Next, the conductive substrate 3 is placed in a nozzle holder 2 of a photo-CVD apparatus as shown in FIG. 4, and first evacuated to a vacuum using a pump 12. When the degree of vacuum becomes approximately IXLOG or lower, the temperature of the substrate holder 2 is raised and the substrate temperature is set as desired. In the present invention, the substrate temperature is preferably -20°C to 200°C, more preferably O
It is desirable that the temperature is between 150°C and 150°C.

Next, silane gas such as SiH4, Si2H6, 5i3HB, N2, NH3, H2NNH2.

Nitrogen gas such as HN3, NH4N3, and impurity introduction gas (B2H6゜PH3f-) as needed.
．． It flows into the deposition chamber 1 using cylinders 7, 8, and 9 and flow meters 6b to 9b. At this time, gases such as H2, Ar, and He may be simultaneously introduced.

Next, a low-pressure mercury lamp was used from the top of the reaction tank to
7) Irradiate the light onto the substrate with an intensity of about 5-50 mW/Cm2 to deposit the layer.

In order to form the first layer region of P-type and N-type conductivity, it is necessary to simultaneously use the silane-based gas and B2H6 in the case of P-type conductivity.
Gases such as H2 and Ar are mixed with gases such as H2 and Ar to adjust the concentration and flow into the reaction tank. In addition, in the case of N type, PH3, A
A gas such as sH3 is mixed with a gas of H2 and Ar, and the mixture is deposited in the deposition chamber 1.
flows into. After the gas flows in, the pressure is adjusted and the gas is irradiated with light to decompose and deposit a layer.

In order to actually form ultrathin layers in the intersecting IL in order to form a superlattice structure, it is necessary to change the four raw gases used to form each thin layer each time. That is, each time a different thin layer is formed, the raw material gas is introduced into the deposition chamber 1, and the chamber is evacuated to an appropriate degree of vacuum using a fresh air device to prevent autodoping. Furthermore, in order to control the thickness of each layer to a desired level, the excitation light is irradiated intermittently by opening and closing the shutter 17.

The optical bandgap of each layer constituting the light-emitting layer of the light-emitting device is determined by measuring the absorption coefficient α, and from the relationship between Jαhν and hν, the localized level density is determined by the FE method, and the quantum efficiency is determined by the light-emitting characteristics of the diode ( (temperature dependent force).

The thickness of the light-emitting layer is preferably about 500 to 3,000.

After this, an insulating layer similar to the above-mentioned material is layered on top of the light emitting layer. And finally aluminum.

Based on metal electrodes such as gold.

Other preparation methods include heating and decomposing the reaction gas flowing into the reaction tube in an external electric furnace and depositing it on a substrate kept at a temperature lower than the gas temperature. .

5cott, R,M, Plecenick.

and E. E. Simonyi, Appl.

Phys, Lett, vol. 39 (1981) p.
73).

non-5i used as the first layer region (I) of the present invention
Even if this method is used when depositing :H, a film with a large optical band gap and a low local level density can be produced.

〔Example〕

The optical CVD apparatus shown in FIG. 4 described above was used.

According to the above procedure and conditions, a light emitting device having the structure shown in FIG. 3 was prepared as follows, and a pulsed high frequency electric field was applied from the power source 307 to conduct a characteristic test.

The insulating layers 303 and 305 have a thickness of 3000 y20.
3 thin film is used, and the light emitting layer is formed by forming the first layer region (I) into a raw material 4.
Using Si2H6 gas as the gas, the substrate temperature was 50°C.
The second layer region (II) was formed using NH3/5
Film formation was performed at a flow rate ratio of i2Hs = 1/1 and a substrate temperature of 50°C using Soronhoshi 90SCCM. Perform this operation 25 times continuously to create 25 cycles of non-St:H/non-5i.
A light-emitting layer having a superlattice structure composed of N:H was created.

At this time, the first layer region (I) and the second layer region (II)
The thickness of each group was set at 40 people. As the electrode 302, I
As the TO transparent electrode and the electrode 306, an A pattern electrode was used.

When a pulsed high frequency electric field of 100 VIKHz was applied to the light emitting device thus prepared, light emission having an emission peak in the visible light region of 50 ft-L was obtained. this is,
This value is more than 16 orders of magnitude larger than the light emitted by light emitting elements using non-crystalline silicon realized to date, and it was found that the light emitting efficiency has been improved. Furthermore, when we tested the stability and durability of the light emitting characteristics by continuously applying the high frequency electric field described in "-" for a long time, we found that the stability was about 5 times that of the conventional example, and the durability was 1.5 times that of the conventional example. As a result, it was ranked 71#, which is an order of magnitude better.

〔effect〕

As mentioned above, the light-emitting element of the present invention has a luminescence peak in the visible wavelength region, and also can obtain sufficient luminescence H and H, 1) improves the luminous efficiency and reproducibility, and 1) stabilizes the luminescent characteristics. You can dramatically increase your health and longevity.

[Brief explanation of the drawing]

FIGS. 1 to ff13 are schematic diagrams showing the layer structure of preferred embodiments of the light emitting device of the present invention, and FIG. 4 is a schematic diagram showing an example of an apparatus for producing the light emitting device of the present invention. be. 101---one substrate, 102,106---electrode, 103.105---one electrically insulating layer. 104---One light emitting layer, 301---Glass substrate, 302---One transparent electrode, 303.305---One insulating layer. 304---One light emitting layer, 306---Metal electrode.

Claims (3)

[Claims] (1) A pair of electrically insulating layers that sandwich a light-emitting layer, and at least one pair of electrodes that sandwich and electrically connect the light-emitting layer and the insulating layer, and the light-emitting layer contains hydrogen atoms. a first layer region made of non-single-crystal silicon including
A light-emitting element characterized by having a multilayer structure in which these are periodically laminated as a unit. (2) The optical band gap of the first layer region is 2.
The light emitting device according to claim 1, which has a voltage of 0 eV or more. (3) The light emitting device according to claim 1, wherein the localized level density of the first layer region is 10^1^6 cm^-^3, eV^-^1 or less at the midgap.