JPS6269571A - Light emitting element - Google Patents

Abstract

PURPOSE:To enhance light emitting efficiency and reproducibility, by laminating an electric insulating layer on a light emitting layer, which is composed of a non-single crystal material including silicon atoms, carbon atoms and fluorine atoms, thereby providing a light emitting peak in a visible wavelength region. CONSTITUTION:On a lower electrode 102, which is provided on a substrate 101, an electric insulating layer 103, a light emitting layer 104 and an upper electrode 105 are provided. The light emitting layer 104 is constituted by non- single crystal silicon, which includes silicon atoms Si, carbon atoms C and fluorine atoms F and also includes hydrogen atoms H as required. The local level density of the light emitting layer 104 is made to be 5X10<16>cm<-3>.eV<-1> or less at an intermediate gap. Then a light emitting peak is located in a visible wavelength region, and sufficient amount of light emission can be obtained.

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.

Tsuchie (1983), PP432-434. H.

Munekata, H, Kukimoto, and Jpn,
J, Appl, Phys, 21 (1982) P
P473-475. The hydrogenated amorphous silicon carbide described in Takahashi et al.
It is one of the materials that is attracting attention because it can be applied to semiconductor engineering similar to single-crystal silicon, and because it potentially has excellent properties.

The light-emitting element using hydrogenated amorphous silicon carbide as a light-emitting material described in the cited document 2 has a double insulation structure in which a light-emitting layer is sandwiched between insulating layers.

[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. However, there are still many points that need to be improved in practical terms, and they have not yet been industrialized as light source elements or display elements used in O, A equipment, etc.

〔the purpose〕

The 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 an emission peak in the visible wavelength region and a sufficient amount of light emission, and is designed to improve 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 includes a light emitting layer made of a non-single crystal material containing silicon atoms (Si), carbon atoms (C), and fluorine atoms (F), and an electrically insulating layer overlaid with the light emitting layer. and at least one pair of electrodes sandwiching and electrically connecting these light-emitting layer and insulating layer, and the localized level density of the light-emitting layer is 5 x 1016 cm-3 in midgap.
-Characterized by being less than eV-1.

[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. A light emitting layer 104 and an upper electrode 1 provided on the light emitting layer 104
05.

The insulating layer 103 is a light emitting layer 104 in a different form from that shown in the drawing.
It can also be provided between the electrode 105 and the electrode 105.

When the light emitting device shown in FIG. 1 is used as a planar light emitting device, 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 amount of light emitted per unit 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 base 101 be transparent like the electrode 102 or translucent to the emitted light.

In the present invention, the light-emitting layer includes non-single crystal silicon (hereinafter referred to as rnon) containing silicon atoms (Si), carbon atoms (C), fluorine atoms (F), and optionally hydrogen atoms (H).
-SiC:F(H)").

Fluorine atoms (F) contained in the light-emitting layer compensate for free dangling bonds of silicon atoms and carbon atoms, and its content depends on the semiconductor properties, optical properties, structural stability, and heat resistance of the formed layer. In the present invention, the content of fluorine atoms (F) is preferably from 5 atoms PPM to the sum of silicon atoms and carbon atoms. Desirably, the range is 25 at.%, more preferably 10 at.PPM to 20 at.%, optimally 50 at.PPM to 15 at.%. The content of hydrogen atoms (H) contained as necessary is determined as desired depending on the relationship with the content of fluorine atoms (F) and the device characteristics required for the device, but silicon atoms and carbon atoms, preferably from 0.01 to 35 atom %, more preferably from 0.1 to 30 atom %, and most preferably from 1 to 30 atom %. Further, it is desirable that the total amount of fluorine atoms (F) and hydrogen atoms (H) is contained in the layer so that the total amount does not exceed 40 at %.

By appropriately selecting the ratio of silicon atoms (Si) and carbon atoms (C) as desired, the emission peak wavelength 9 emission intensity can be adjusted.
If expressed as the value of X of ixC1-x, preferably 0.05≦X
It is desirable that ≦0.99, more preferably 0.1≦X≦0.9, optimally 0.15≦X≦0.85.

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 also desirable to select and use raw materials that are compatible with the photo-CVD method.

The light emitting layer 104 is composed of non-3iC: F (H), and is preferably formed as a layer exhibiting so-called intrinsic (type 1) semiconductor characteristics. no
Since a layer composed of n-SiC: F (H) exhibits a slight N-type tendency when it does not contain so-called P-type or N-type impurities, the light-emitting layer 104 has a ■-type conductivity. To form a layer, a small amount of P-type impurity is added.

The light-emitting layer 104 can also 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 light-emitting layer 104 an I-type conductive layer, a P-type impurity that imparts P-type conductivity characteristics is contained during layer formation, or a P-type impurity is added to a layer already composed of non-3iC:F(H).
Type impurities may be implanted by means such as ion implantation.

The P-type impurity is an atom belonging to the so-called group 1 of the periodic table (group 3 atom), ie, B (boron).

AJI (aluminum), Ga (gallium).

Examples include In (indium) and Te (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, does not adversely affect the efficient extraction of light emitted from the light emitting layer 104 to the outside, and is easy to form. Almost anything can be used.

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, as a material constituting the insulating layer 103,
Specifically, Y2O3,5i02.
Amorphous silicon oxide (a-3ixO1-x, where Oxx<1), HfO2, 5f3N4, amorphous silicon nitride (a-3iyNl-y, where o<y<1), A2
03, PbTiO2, amorphous BaTiO3, Ta2
05 etc. can be mentioned.

FIG. 2 shows another preferred embodiment of the light emitting device of the present invention.

The structure of the light emitting device shown in FIG. 2 is basically the same as that of the light emitting device shown in FIG.

The light emitting element shown in FIG. 2 has a transparent base 201 made of glass or the like.
Transparent electrodes 202 . Insulating layer 203, light emitting layer 20
4. The metal electrode 205 has a laminated layer structure, and the electrode 2
02 and the metal electrode 205 are electrically connected to connection terminals of a power source 206 for applying a pulsed or sawtooth high frequency high electric field, respectively.

In the case of the light emitting device shown in FIG. 2, when a high frequency electric field is applied by a high frequency power source 207, light is emitted from the light emitting layer 204, and the emitted light is transmitted to the insulating layer 203. Transparent electrode 202.
It passes through the base 201 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 in an interface state formed at the interface between the insulating layer 203 and the light-emitting layer 204 are accelerated by an 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 half cycle of the excitation high frequency high electric field.

These two processes result in electroluminescent 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 light emitting layer is set to 2. OeV
It is desirable that the number is above.

Further, the local level density at the center of the optical band gap (mid gap) of the light emitting layer is preferably 5 X I 01
6cm0*e V-1 or less, more preferably approximately
It is desirable that it be 1016 cm0 e e V-1 or less.

In this way, by controlling the physical properties of the light-emitting layer, it is possible to set the emission peak wavelength to a desired wavelength in the visible range and to dramatically improve the recombination efficiency. It can be measured.

Further, by controlling the distribution of recombination levels so that the external quantum efficiency of the light emitting layer is preferably 10 -4% or more, 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. 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 the method can be set to desired conditions as appropriate, such as HOMOCVD.
It may be performed by a method such as a method, a plasma CVD 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 substrate may be electrically conductive or electrically insulating, but preferably has relatively good 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.

The conductive substrate is NiCr or stainless steel.

All, Cr, Mo, Au, Nb, Ta, V.

Tj 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, NiCr, AM
, Cr, Mo, Au, Ir, Nb.

Ta, V, Ti, Pt, Pd, In203Sn02,
If conductivity is added by providing a thin film made of ITO (In203+5n02) or a synthetic resin film such as polyester film, NiC
r, A l, A g +Pb, Zn, Ni, A
u, Cr, Mo, Ir.

A thin film of metal such as N b , Ta , V , T i , P or the like is provided on the surface by vacuum evaporation, electron beam evaporation, sputtering, etc., or the surface is laminated with the above metal to make the surface conductive. gender is given.

Next, an example of manufacturing the light emitting device of the present invention will be explained using the optical CvD apparatus shown in FIG.

As the raw material gas for forming the light emitting layer used in the case of the photo-CVD method, for introducing silicon atoms and fluorine atoms, Si2F6. SiH2F2. Examples include fluorinated silane gas such as SiF4, and for introducing silicon atoms and hydrogen atoms, the general formula Si nH2n (n=
3.

Examples include cyclic silicon hydride compounds represented by S i nH2n+2 (n=2, ----) and linear or branched chain silicon hydride compounds represented by S i nH2n+2 (n=2, ----1). It will be done.

The raw material gas for introducing carbon atoms is CH4, C2H.
6, C3H8, C4H10, C2H4, C3H6, C4
Mention may be made of gaseous or easily gasified hydrocarbon compounds such as H8, C2H2, CH3C2H, C4H6.

In addition, (CH3)25iH2(CH3)3SiH can also be used.

Each of the above-mentioned fluorinated silicon compounds, silicon compounds, and carbon compounds may be used in combination of two or more types, but in this case, the film properties expected by each compound are averaged or synergistically obtained. Improved properties are obtained.

Further, hydrogen gas may be mixed with the raw material gases listed in L and used.

The silicon compound of the above general formula easily undergoes a chemical reaction when applied with light energy or relatively low thermal energy, so it is possible to form a deposited film of good quality, and in this case, the substrate temperature is also relatively low. be able to. Furthermore, although the excitation energy can be applied uniformly or selectively to the source gas that has reached the vicinity of the substrate, it is also possible to form a deposited film by irradiating the entire substrate using an appropriate optical system. Alternatively, it is also possible to selectively control and selectively irradiate only a desired area to form a deposited film, and it is also convenient that a resist or the like can be used to irradiate only a predetermined graphic area to form a deposited film. have.

In FIG. 3, l is the deposition chamber, and the internal substrate support 2''-
A desired substrate 3 is placed on.

Reference numeral 4 denotes a heater for heating the substrate, which is supplied with electricity via a conductive wire 5 and generates heat. The substrate temperature is not particularly limited, but in general, in order to increase the optical band gap of the light emitting layer and obtain visible light emission, it is preferably 350° C. or lower, more preferably 300° C. or lower.

6 to 9 are gas supply sources, and if a liquid one of the chain silicon hydride compounds represented by the above general formula is used, 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 number of types of the fluorinated silicon compound, the silicon hydride compound of the general formula, and the carbon compound used, the diluent 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 gas supply sources 6 to 9 are marked with a for branch pipes, b for the flow, and C for the gas supply sources 6 to 9.
The pressure gauges that measure the pressure on the high-pressure side of each flowmeter are the ones marked with d or e, and the valves marked with d or e are for opening and closing each gas flow and adjusting the flow rate.

Raw material gases and the like supplied from each gas supply source are mixed in the middle of the gas introduction pipe 10, and are introduced into the chamber 1 by being energized by a ventilation device (not shown).

Alternatively, the gases are introduced into the chamber 1 alternately from each gas supply source. 1
1 is a pressure gauge for measuring the pressure of gas introduced into the chamber l. Further, 12 is a gas exhaust pipe, which is connected to an air loss 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 deaerated and brought into a reduced pressure state before introducing the raw material gas etc., the atmospheric pressure in the chamber is preferably 5xto-5Torr or less, more preferably 1x1O-GTorr or less. Further, in a state where the raw material gas and the like are introduced, the pressure inside the chamber 1 is preferably txto-2 to 100 Torr, more preferably 5 x 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 generator 14 to the entire substrate or a desired part of the substrate using an appropriate optical system, and is irradiated onto the raw material gas flowing in the direction of the arrow 16, causing excitation and decomposition, and causing the substrate to be heated. No on the whole or desired part on 3.
A deposited film of n-StC: F (H) is formed. At this time, it is desirable that the thickness of the light emitting layer be about 200 to 10,000.

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

Another manufacturing 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-3iC used as the light emitting layer of the present invention: F
(H) Even if this method is used during deposition, a film with a large optical band gap and a low degree of localization can be produced.

〔Example〕

A light-emitting device having the structure shown in FIG. 2 was created as follows using the photo-CVD apparatus shown in FIG. A characteristic test was conducted.

The insulating layer 203 is 7?3000 people thick. O3 thin film is used, and the light emitting layer is made of C2) T4 gas and Si
Film formation was performed using 2H6 gas and Si2F6 gas at a substrate temperature of 300° C. using a low-pressure mercury lamp. As the electrode 202, an ITO transparent electrode was used, and as the electrode 206, an AfL electrode was used. The light emitting device created in this way (
When a pulsed high frequency high electric field of 100 V and IKHz was applied to sample No. 1), light emission having an emission peak in the visible light region of 20 ft-L was obtained. This value is more than an order of magnitude larger than the light emitted by light emitting elements using non-single crystal silicon carbide that have been realized to date, and it was confirmed 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 above-mentioned high-frequency electric field for a long time, we found that the stability was about 3 times that of the conventional example, and the durability was 1.5 times that of the conventional example.
The result was an order of magnitude better.

Further, light emitting devices of samples No. 2 and 3 were prepared in the same manner as above except that the substrate temperature was changed as shown in Table 1, and the results of measuring the characteristics of each are shown in Table 1.

Furthermore, when we measured the lifetime of the light-emitting elements of each sample, they showed an order of magnitude longer lifespan than conventional light-emitting elements, good reproducibility, and the light-emitting characteristics were always stable during lifetime measurements. .

In addition, when an environmental test was conducted by continuous use in an environment of 80% RH and 40° C., it was confirmed that the initial device characteristics were maintained even after 72 hours had passed, and that the device had excellent environmental characteristics.

Table 1 [Effects] 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, improves luminous efficiency and reproducibility, and has stable luminescent characteristics. It can dramatically improve your health and longevity.

[Brief explanation of drawings]

1 and 2 are schematic diagrams showing the layer structure of a preferred embodiment of the light emitting device of the present invention, and FIG. 3 is a schematic diagram showing an example of an apparatus for producing the light emitting device of the present invention. be. 101--M-Substrate 102.106--Electrode 103.203--One insulating layer 104.204--One light emitting layer 201---Glass substrate 202---One transparent electrode 205--- monometallic electrode

Claims (1)

[Claims] A light-emitting layer made of a non-single-crystal material containing silicon atoms, carbon atoms, and fluorine atoms, an electrically insulating layer overlaid on the light-emitting layer, and an electrically at least one pair of electrodes connected to the light emitting layer, and the localized level density of the light emitting layer is 5×10^1^ with a midgap.
A light-emitting element characterized in that it is 6 cm^-^3·eV^-^1 or less.