JPS6269570A - Light emitting element - Google Patents

Abstract

PURPOSE:To improve light emitting efficiency and reproducibility, by providing a multilayer structure for a light emitting layer, in which a layer region comprising non-single crystal material including Si atoms, C atoms and H atoms and a layer region, whose optical band gap is different from that of said layer region, are combined as one unit. CONSTITUTION:A light emitting element is composed of a lower electrode 102, an electric insulating layer 103, a light emitting layer 104 and an upper electrode 105. The light emitting layer has a multilayer structure, in which a layer region I and a layer region II are periodically laminated as one unit. The layer group I comprises a non-single crystal material including Si atoms, C atoms and H atoms. The layer region II has the different optical band gap from that of the layer region I. The H atoms included in the layer region I compensates for the free dangling bonds of the Si atoms and the C atoms. With respect to the sum of the Si atoms and the C atoms, the rate of 0.1-40atom% is suitable.

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, materials constituting the light emitting layer of a light emitting device;
Various things have been reported, among which, for example, Ap
pl, Phys, Lett.

29 (1976), PP620-622. J.

1. Pankove, D.E., Carlson.

Jpn, J. Appl, Phys, 21 (, 1982
) PPL473-L475. K.

Non-single crystal silicon containing hydrogen atoms (hereinafter referred to as rnon-5t:HJ) described in Takahashi et al. It is one of the materials that is attracting attention because it can be applied with the same semiconductor technology as 11-crystalline silicon, and because it may have excellent latent properties.

The structure of the light-emitting element using non-3i:H as a light-emitting material described in the cited document 2 is based on P containing P-type impurities.
It has a homojunction in which a type conductive layer (P layer), a layer containing neither P type nor N type 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 range, and in addition, have low emission intensity, short lifespan, and poor stability of light-emitting characteristics. There are many points that need to be improved in practical terms.

]] As one of the improvement plans, attempts have been made to add carbon atoms to non-Si:H to widen the optical band gap and obtain light emission in the visible wavelength region, but there are still problems in practical use. However, it has not yet been industrialized as a light source element or display element used in 0, A equipment, etc.

〔the purpose〕

A main object of the present invention is to provide a light emitting device that improves the above-mentioned conventional drawbacks.

Another object of the present invention is to provide a light-emitting element that has a sufficient amount of light emission in the visible wavelength range and has better luminous efficiency and reproducibility.

Another object of the present invention is to provide a light emitting element with dramatically improved stability of light emitting characteristics and lifetime.

[Means for solving problems]

The light emitting device of the present invention has a light emitting layer, an electrically insulating layer superimposed on 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, The light-emitting layer includes a first layer region made of a J1 single crystal material containing silicon atoms, carbon atoms, and hydrogen atoms, and a second layer region having an optical band gap different from the layer region. It is characterized by having a multilayer structure in which layers are stacked periodically as a unit.

[For production]

The light-emitting element of the present invention has a luminescence peak in the visible wavelength region and a sufficient amount of luminescence by having the configuration described in "2", and can improve luminous efficiency and reproducibility, and improve the stability of luminescent characteristics. Lifespan can be dramatically improved.

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. 1 has an electrically insulating layer 103 on a lower electrode 102 provided on a base 101. Luminescent layer 1
04 and the upper electrode 1 provided on the light emitting layer 104'2
05 and is a mess.

Note that the insulating layer 103 can also be provided between the light emitting layer 104 and the electrode 105, separately from what is shown in the drawings.

When the light emitting element shown in FIG. 1 is used as a planar light emitting element, the electrode 102 and/or the electrode 105 must be transparent if even the color of the emitted light is to be used, and the emitted light h1 If the material is to be used, it is desirable that the material be transparent to the 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.

As described above, in the light emitting device of the present invention, the light emitting layer has a non-single crystal material (hereinafter referred to as rn) containing silicon atoms (St), carbon atoms (C), and hydrogen atoms (H).

A first layer region (I) composed of n-SiC:HJ (abbreviated as HJ) and a second layer region (II) having a different optical bandgap Egopt from the layer region (I). It has a multi-layered structure in which layers are stacked periodically as a unit. In order to achieve the effects of the present invention even more effectively, the first layer region (I) and the second layer region (II) laminated in a periodic structure should have a 61-layer mechanical size. The respective layer thicknesses are selected so as to produce the effect and are laminated alternately to construct a so-called superlattice structure.

Optical bandgap Ego of the second layer region (II)
pt(II) is preferably larger than the optical bandgap Egopt(I) of the first layer region (I), ie, so that the second layer region (II) plays the role of a potential barrier layer. The material selection is made and the layers are formed.

In the light emitting device of the present invention, the light emitting layer 104 is an I-type conductive layer exhibiting intrinsic semiconductor characteristics, or a slightly N-type or P-type conductive layer.
Formed as a molded conductive layer. And non-3iC:
According to its general tendency, a layer composed of H contains only a slight amount of N if it does not contain either so-called P-type or N-type impurities.
Since it exhibits a type tendency, in order to form a ■ type conductive layer, a P type impurity is contained in the I and v types.

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 heterojunction is formed at the junction with 202. The material constituting the second layer region (II) 202 has an optical band gap Eg higher than non-3iC:H.
Examples include non-monocrystalline semiconductor materials or non-monocrystalline electrically insulating materials with a larger opt. The material constituting these second layer regions (II) 202 is the same as that of the first layer region (II) 202.
I) The materials constituting 201 have different chemical composition elements or chemical composition ratios, but it is more effective to improve the luminescence characteristics if the m-body constituent elements are common. I can do it.

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. h is determined as desired depending on the device characteristics to be
It is desirable to determine this so that the single-child size effect becomes noticeable.

The layer thickness of the first and second layer regions is preferably 5
people to 100 people, more preferably 8 to 80 people, optimally 1
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-mentioned superlattice structure into the light emitting layer 104, specifically, for example, the first layer region (I) 201 is made of a so-called non-doped material that does not contain either P-type or N-type impurities. non-SiC:
H layer or I-type non-SiC that contains a small amount of P-type impurity and becomes an intrinsic semiconductor: H layer, second layer region (I
I) 202 is a semiconducting or electrically insulating non-single crystal material (hereinafter referred to as r
(abbreviated as "non-3iN(H)"), or a semiconducting or electrically insulating non-containing material containing hydrogen atoms (H), silicon atoms (St), and oxygen atoms (0) as necessary. They are each composed of a single crystal material (hereinafter abbreviated as rnon-3iO(H)J) or non-3i:H.

The first layer region (I) 201 and the second layer region (II) 202 made of these materials 1 are preferably arranged alternately in ten to several tens of cycles, depending on the respective layer thickness. Laminated.

The hydrogen atoms (H) contained in the first layer region (I) are
It compensates for n-type dangling bonds of silicon atoms and carbon atoms, and its content is an important factor that influences the semiconductor properties and optical properties of the formed layer, and the light emitting properties of the device, and in the present invention, The content of hydrogen atoms (H) is preferably 0.1 to 40 with respect to the sum of silicon atoms and carbon atoms.
atomic %, more preferably 0.5 to 35 atomic %, optimally 1
~30 at%.

In the present invention, the above-mentioned structure is achieved 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 raw materials for forming the light-emitting layer that are compatible with the photo-CVD method.

The first layer region (I) 201 is composed of non-3iC:H, and is preferably formed as a layer exhibiting so-called intrinsic (N-type) semiconductor characteristics. n
A layer composed of on-3iC:H generally shows a slight N-type tendency when it does not contain so-called P-type or N-type impurities, so the first layer region (I) 201 is N
To form a conductive layer, a small amount of P-type impurity is added.

The first layer region (T) 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 an N-type conductive layer, it is necessary to include 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-3iC:H. Then, P-type impurities may be implanted by means such as ion implantation.

Examples of P-type impurities include atoms belonging to the so-called group Ⅰ of the periodic table (group ① atoms), that is, B (硼、も).

AM (aluminum), Ga (gallium).

Examples include In (indium) and Ti (thallium), among which B and Ga are particularly preferably used.

The material constituting the electrically insulating layer 103 is one that has good electrical insulation properties and does not have a negative effect on efficiently extracting the light emitted from the light emitting layer 104 to the outside.
Almost any material can be used as long as it is easy to form a film.

The insulating layer 103 needs to be transparent to the emitted light in order to extract the emitted light to the outside from the base 101 side. In the present invention, specifically, Y2O3, 5i02. Amorphous silicon oxide (a-3iX01-XiI-j l
, , O<x<t), HfO2, Si3N4. , It crystalline silicon nitride: I7 (a-3iyN 1-y, where o<
y<1), A pattern 203, PbTiO3, amorphous Ba
Examples include Ti03 and Ta205.

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

The structure of the light emitting device shown in FIG. 3 is basically the same as that of the light emitting device shown in FIG.

The light emitting element shown in FIG. 3 has a transparent base 301 made of glass or the like.
1-, transparent electrode 302. Insulating layer 303, light emitting layer 3
04. The metal electrode 305 has a laminated layer structure, and the electrode 302 and the metal electrode 305 are each electrically connected to a connection terminal of a power source 306 for applying a pulse-like or sawtooth-like high frequency high electric field. .

In the case of the light emitting element shown in FIG. 3, when a high frequency electric field is applied by a high frequency power source 306, light is emitted from the light emitting layer 304, and the emitted light is transmitted to the insulating layer 303, the transparent electrode 302,
It passes through the base 301 and is emitted to the outside.

The process of light emission at this time can be considered as follows. That is, a process in which electron-hole pairs trapped at the 11th position at the interface formed at the interface between the insulating layer 203 and the light-emitting layer 204 are accelerated by the electric field, collide, and recombine in a luminescent manner, and The process of injecting high-energy electrons through the Schottky barrier generated at the interface with the light-emitting layer 204 is repeated every cycle of the excitation high-frequency high electric field.These two processes produce electroluminescence light emission.

In the light emitting device of the present invention, in order to obtain an emission wavelength in the visible range, the optical band gap Egopt of the first layer region (I) is set to 2. It is desirable that it be less than OeV.

Further, the localized level density at the center of the optical band gap (mid gap) of the first layer region (I) is preferably 5.
X 1016c "3・e V-1 or less, more preferably I
It is preferable that X 1016 cm-3·eV-1.

In this way, by controlling the physical property values of the first layer region (H), the recombination efficiency can be dramatically improved, and therefore the luminous efficiency can be improved.

In addition, the external quantum efficiency of the first layer region (I) is 1,0-4
By controlling the distribution of recombination levels so that the recombination level is less than 1%, it is possible to obtain a light emitting element that emits light with high intensity.

It is desirable that the light emitting element having the characteristics described above be produced by the photo-CVD method under the conditions described below. The method for producing the light emitting device of the present invention is not limited to the photo-CVD method, as long as the object of the present invention is achieved, and may be performed by, for example, the HOMOCVD method or the plasma CVD method by setting appropriate conditions. It may be done by etc.

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

In the case of a conductive substrate, it is not necessary to provide an electrode between the substrate and the light emitting layer.

As the conductive substrate, NiCr, stainless steel, AM, C
r, Mo, Au, Nb, Ta.

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.

When an electrically insulating substrate is used as the substrate, its surface is subjected to conductive treatment to serve as an electrode between the substrate and the light emitting layer.

For example, if it is glass, the surface may have NiCr, Al, etc.
l, Cr, Mo, Au, Ir, Nb.

Ta, V, Ti, Pt, Pd, In2O3゜5n02
, conductivity can be imparted by providing a thin film made of ITO (In203+5no2), etc., or synthetic resin such as polyester film.
iCr, AfL, Ag.

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

A thin film of a metal such as Nb, Ta, V, Ti, Pt, etc. is provided on the surface by vacuum evaporation, electron beam evaporation, sputtering, etc., or the surface is laminated with the above metal to impart conductivity to the surface. Ru.

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 stand 2'' inside.

Reference numeral 4 denotes a heater for heating the substrate, which is supplied with electricity via a conductive wire 5 and generates heat. Although the substrate temperature is not particularly limited, it is generally desirable to be 200° C. or less in order to enlarge the optical band and cap of the light emitting layer and obtain visible light emission.

6 to 9 are gas supply sources, which are provided with an appropriate vaporizer when liquid raw materials are used in normal conditions.

The vaporizing bag H may be of any type, such as a type that utilizes heating and cooling, and 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, but depending on the number of types of raw materials used, dilution gas, etc.
It is selected as appropriate depending on whether or not the dilution gas and raw material gas are premixed. In the figure, the symbols for gas supply sources 6 to 9 are marked with a for branch pipes, b for flow meters, and C for i.]
The next one is a pressure gauge that measures the pressure on the high pressure side of each flowmeter, d
The ones marked with e are valves for opening and closing each gas flow and adjusting the flow rate.

Gaseous raw materials and the like 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 a pressure gauge for measuring the pressure of the gas introduced into the chamber l. Further, 12 is a gas exhaust pipe, which reduces the pressure inside the deposition chamber 1,
It is connected to an exhaust device (not shown) for forcibly exhausting the introduced gas.

13 is a valve in the regulator. When the inside of the chamber 1 is evacuated and brought into a reduced pressure state before introducing raw material gas etc., the pressure inside the chamber is preferably 5×10 −5 Torr or less, more preferably 1×IC1 GTor or less.

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 generating device, such as a mercury lamp, a xenon lamp, a carbon dioxide laser, an argon ion laser, an excimer laser, or the like. Note 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 material gas and form a deposited film.

Light 15 is directed from the optical 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 element, first, a glass substrate (C#7059) is used as a base, and a 600-layer thick 7ITO layer is formed thereon as a conductive layer by sputtering. I+! ,! The resistance value is approximately 50Ω/mouth. Next, the conductive substrate 3 described in 1- is placed in the substrate holder 2 of a photo-CVD apparatus as shown in FIG.
Step 2: Evacuate to vacuum. The degree of vacuum is approximately i x t o -e
When the temperature is below, raise the temperature of the substrate holder 2,
Set the substrate temperature as desired. In the present invention,
The substrate temperature is preferably -20°C to 200°C, more preferably 0°C to 150°C.

Next, CH4, C2H6, C3H8, C4H10, C2
H4, C3H6, C4H8, C2H21, CH3C2H
, (CH3)23iH2.

Carbon-based gas such as (CH3)3SiH, SiH4r3
i 2H6, S i 3) (silane gas such as e, N2
, NH3, H2NNH2, HN3, NH4N3, etc., and if necessary, a gas for introducing impurities (
B2H6, PH3, etc.) in a 6°7.8.9 cylinder, 6b
~9b into the deposition chamber l using a flow meter.

At this time, gases such as H2°Ar and He may be simultaneously introduced.

Next, a low pressure mercury lamp was used to deposit 185 m
m of light is irradiated 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.
and the like are mixed with gases such as H2 and Ar to adjust the concentration and flow into the deposition chamber 1. In addition, in the case of N type, PH3,
A gas such as AsH3 is mixed with gases such as H2 and Ar and flows into the deposition chamber l. 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 stack ultra-thin layers alternately to form a superlattice structure, it is necessary to change the raw material gas for forming each thin layer each time. That is, each time a different thin layer is formed, the introduction of source gas into the deposition chamber 1 is stopped, and the chamber is evacuated to an appropriate degree of vacuum using an exhaust 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 local 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.

Finally, metal electrodes are formed by vapor depositing aluminum, gold, etc.

Another production method is HOMOCvD, in which a reaction gas flowing into a reaction tube is thermally decomposed in an external electric furnace and deposited on a substrate kept at a temperature lower than the gas temperature (B, A).

5cott, R,M, Plecenick.

and E. E. Simonyi, Appl.

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

Non-3i used as Takuaki Ki's first layer region (I)
Even if this method is used when depositing C:H, a film with a large optical band gap and a low localized level density can be produced.

[Example 1] -1- Using the optical CVD apparatus shown in FIG. 4, -1-
According to the procedure and conditions described above, a light emitting device having the structure shown in diagram t53 was produced as follows, and a pulsed high frequency electric field was applied from the power source 307 to conduct a characteristic test.

The insulating layer 303 is 7?3000 people thick. Using an O3 thin film, the emissive layer consists of the first layer region (I) of C3HB/S
i 2 H6 = 1/20 flow rate ratio, total flow rate 15
03CCM, film formation was performed at a substrate temperature of 50'O,
The second layer region (II) is N H3/S i 2
Film formation was performed at a flow rate ratio of H6=1/1, a total flow rate of 903 CCM, and a substrate temperature of 50'O. Perform this operation 25 times continuously to create 25 cycles of non-3iC:H/non-
A light emitting layer having a superlattice structure made of SiN:H was created. At this time, the first layer region (I) and the second layer region (TI
) was set at 40 people each. As the electrode 302, an ITO transparent electrode was used, and as the electrode 306, an An electrode was used. The light emitting device created in this way has a frequency of 100VIKHz.
When a pulsed high frequency high electric field of 60ft-
Luminescence having an emission peak in the visible light region of L was obtained.

This value is more than 16 orders of magnitude larger than the light emitted by light emitting elements using non-single crystal silicon that have been realized up to now, and it has been found that the light emitting efficiency has been improved. Furthermore,
'' - Testing the stability and durability of the luminescent properties by continuously applying the high-frequency electric field for a long time revealed that the stability was about 5 times better and the durability was 1.5 orders of magnitude better than the conventional example mentioned above. The result was that

[Example 2] In Example 1, when forming the second layer region (II), N H3/S i 2 F 6 = 1 / 1
The total flow rate is 11005ec with the flow rate ratio of , and the first layer region (
The characteristics were evaluated in the same manner as in Example 1 on a sample prepared using the same procedure and conditions as in Example 1, except that the periodic stacking of I) and the second layer region (IT) was 20 cycles. However, a colored luminescence of 50 ft-L was obtained.

When this sample was subjected to a separate long-term continuous use test, it showed extremely stable luminescent characteristics.

[Example 3] In Example 1, when forming the second layer region (II), the flow rate ratio was No/5i2He=10, and the total flow rate was 110.
05ec, the first layer region (I) and the second layer region (I
Example 1 except that the periodic stacking of I) was set to 35 periods.
When the same characteristics as in Example 1 were performed on a sample prepared under the same procedure and conditions as in Example 1, a colored luminescence of 48 ft-L was obtained.

When this sample was subjected to a separate long-term continuous use test, it showed extremely stable luminescent characteristics.

[Example 4] In Example 1, when forming the first layer region (II), the flow rate ratio was C3HB/S i 2H6 = 1/ioo, the total flow rate was 1203 CCM, and the first layer region (II) Characteristics were evaluated in the same manner as in Example 1 for test piece 4, which was prepared using the same procedure and conditions as in Example 1, except that the periodic stacking of (I) and the second layer region (II) was 30 cycles. When I did this, I got 58
Colored luminescence of f t-L was obtained.

When this sample was subjected to a separate long-term continuous use test, it showed extremely stable luminescent characteristics.

〔effect〕

As described above, the light-emitting element of the present invention has a luminescence peak in the visible wavelength region, can obtain a sufficient amount of luminescence, improve luminous efficiency and reproducibility, and dramatically improve the stability of luminescent characteristics and lifetime. It can be increased to

[Brief explanation of drawings]

1 to 3 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. It is. 101--m-substrate, 102,105--one electrode, 103.303--one electric insulating layer, 104.304--one luminescent layer, 301-----galanu substrate, 302--one Transparent electrode. 305---One metal electrode.

Claims (3)

[Claims] (1) A light-emitting layer, an electrically insulating layer overlaid with the light-emitting layer, and at least one pair of electrodes sandwiching and electrically connected to the light-emitting layer and the insulating layer, the light-emitting layer However, a first layer region made of a non-single-crystal material containing silicon atoms, carbon atoms, and hydrogen atoms, and a second layer region having a different optical band gap from the layer region are considered as one unit. A light emitting device characterized by having a multilayer structure in which layers are periodically stacked. (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 local level density of the first layer region is 5×10^1^6 cm^-^3 at the mid-gap. The light-emitting device according to claim 1, which has a luminance of eV^-^1 or less.