JPS6248082A - Light emitting element - Google Patents

Abstract

PURPOSE:To improve the stability of light emitting characteristic and lifetime by providing a light emitting layer, a pair of electric insulating layers and a pair of electrodes, and setting a local level density of the emitting layer in a midgap to 10<16>cm<-3>.eV<-1> or less. CONSTITUTION:A transparent electrode 202, a lower insulating layer 203, a light emitting layer 204, an upper insulating layer 205, a metal electrode 206 are sequentially laminated on a substrate 201, and a connecting terminal of a power source 207 for applying a high frequency high electric field is electrically connected with the electrodes 202, 206. When the high frequency electric field is applied by the source 207, the layer 204 emits a light, and the emitted light is externally emitted through the layer 203, the electrode 202 and the substrate 201. The local level density at the center of the optical band gap of the emitting layer is set to 10<16>cm<-3>.eV<-1> or less.

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, 42 (1983), PP
432-434.

H, Munekata, H, Kukimoto, YaJP
n, J, Appl, Phys, η.

(1!382) PP473-475, Ni, Takah
Hydrogenated amorphous silicon carbide described in Ashi et al. can be applied with semiconductor engineering similar to single crystal silicon, and may potentially have excellent properties. It is one of the materials that is attracting attention for its

The light-emitting element using hydrogenated amorphous silicon carbide as a light-emitting material described in the above cited document 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. There are many points that need to be improved in practical terms, and 0. It has not yet been industrialized as a light source element or display element used in A-equipment or the like.

〔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 has a good 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 silicon atoms (Si) and carbon atoms (
C) and a hydrogen atom (H) (hereinafter referred to as r
non-SiG (abbreviated as HJ), a pair of electrically insulating layers sandwiching the light emitting layer, and at least one electrically connected layer sandwiching the light emitting layer and the insulating layer. and a pair of electrodes, and the localized level density of the light-emitting layer is 10"cm-3ae V-' or less in a mid-gap.

[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, increases 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 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.
and an upper electrode 106 provided above.

When the light emitting device shown in FIG. 1 is used as a planar light emitting device, the electrode 102 and/or the electrode 106 must be transparent if the color of the emitted light is to be utilized, and the amount of light emitted is If the substrate 101 is to be used, it is desirable that the substrate 101 be transparent to the emitted light.If the emitted light is extracted from the electrode 102 side, the base 101 should be transparent like the electrode 102, or be transparent to the emitted light. On the other hand, it is desirable that the material be translucent.

In the present invention, the light emitting layer is made of n0n-5rC:H! I
will be accomplished.

Hydrogen atoms (H) contained in the light-emitting layer compensate for free dangling bonds between silicon base rods and carbon atoms, and its content depends on the semiconductor properties and optical properties of the formed layer, and the light-emitting properties of the device. In the present invention, the content of hydrogen atoms (H) is preferably 0.1 to 40 at%, more preferably 0.1 to 40 at%, based on the sum of silicon atoms and carbon atoms. The content is desirably 5 to 35 atom %, most preferably 1 to 30 atom %.

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, and in the present invention, Si
If expressed as the value of X of xC1-x, preferably 0.05≦X≦
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 provided by adopting the photo-CVD method (deposited film formation method by chemical vapor phase method using light energy for reaction), and the raw materials for forming the light emitting layer can be provided. It is also desirable to select and use materials that are compatible with the photo-CVD method.

The light emitting layer 104 is composed of a non-SiC:H layer, and is preferably formed as a layer exhibiting so-called intrinsic (■-type) semiconductor characteristics.

A layer made of non-SiG: f (a) exhibits a slight N-type tendency when it does not contain so-called P-type or N-type impurities. 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, it is necessary to include a P-type impurity that gives P-type conductivity when forming one layer, or to add a P-type impurity to a layer already composed of non-5iC:H. may be implanted by means such as ion implantation.

Examples of P-type impurities include atoms belonging to so-called Group Ⅰ of the periodic table (Group 1 atoms), such as B (boron), A (aluminum), Ga (gallium), In (indium), and Tf (thallium). B, G are particularly preferably used.
The material constituting the electrically insulating layers 103 and 105 has good electrical insulation properties and is suitable for the light emitting layer 10.
Almost any material can be used as long as it does not adversely affect the efficient extraction of the light emitted from 4 and is easy to form.

Either one of the insulating layers 103 and 105 needs to be transparent to the emitted light in order to extract the emitted light to the outside. In the present invention, specifically, Y20 is preferably used as the material constituting the insulating layers 103 and 105.
3, S102 1 Amorphous silicon oxide (a-5
ixO1-x However, 0<x<1), Hf07, Si3
N, amorphous silicon nitride (a-SiyNl-y, where o<y<B, A-703.Pb"rto3. Amorphous BaTiO3, Ta70c, 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 . Lower insulating layer 2039 light emitting layer 204. Upper insulating layer 205. The metal electrode 206 has a laminated layer structure, and connection terminals of a power source 207 for applying a pulse-like or tooth-like high frequency high electric field are electrically connected to the electrode 202 and the metal electrode 206, respectively. There is.

In the case of the light-emitting element shown in FIG. 2, when a high-frequency electric field is applied by a high-frequency power supply 207, light is emitted from the light-emitting layer 204, and the emitted light is transmitted to the insulating layer 203, the transparent electrode 202.
It passes through the base 201 and is emitted to the outside.

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
This is considered to be the above.

Further, the localized level density at the center of the optical band gap (mid gap) of the light emitting layer is preferably 5 x 1016
cm-3e e V-' or less, more preferably I X 1
6 I6am-3* e V-' or less is desirable.

In this way, by controlling the physical property values of the light emitting layer, it is possible to set the single emission peak wavelength to a desired wavelength in the visible range, and to dramatically improve the recombination efficiency, thereby improving the light emission 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 preferable that the light emitting device having the above-mentioned characteristics be produced by the photo-CVD method under the conditions described below. For example, the material constituting the substrate constituting the light-emitting device of the present invention may be a material that is not limited to the photo-CVD method, but may be used in the HOMOCVD method by appropriately setting the desired conditions. I can list most of the materials used.

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.

AM, Cr, Mo, Au, Nb, Ta, V, Ti, etc. can be mentioned.

Examples of the electrically insulating substrate include films or sheets of synthetic resins such as polyester, polyethylene, polycarbonate, polyamide, etc., glass, and ceramics.

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, Ding r.

Nb, Ta, V, Ti, Pt, Pd, I-nzo3°S
n02, I To (I H203+s n02
), etc., or if it is a synthetic resin film such as a 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 deposited in a vacuum, provided on the surface by electron beam evaporation, sputtering, etc., or the surface is laminated with the metal to impart conductivity to the surface. be done.

Next, an example of producing the light emitting device of the present invention will be explained using the photo-CVD apparatus shown in FIG.

The raw material gas for forming the light-emitting layer used in the photo-CVD method has the general formula 5inH2n (n = 3, 4, 5) for introducing silicon atoms and hydrogen atoms.
, ----) cyclic silicon hydride compound, 5
Examples include linear or branched chain silicon hydride compounds represented by inH2n+2 (n=2°-111).

The raw material gas for introducing carbon atoms is CH4.

C2H6, C3He, C4H101C2H4.

C3H6, C4Ha, C2H2, CH3C,,H.

Mention may be made of container gaseous or easily gasified hydrocarbon compounds such as C4H6.

In addition, (CH3)2SiH2(CH3)3SiH can also be used.

Each of the silicon compound and carbon compound mentioned above.

Two or more types may be used in combination, but in this case, properties that are averaged over the film properties expected by each compound, or properties that are synergistically improved can be obtained.

Moreover, there is no problem even if hydrogen gas is mixed with the above-mentioned raw material gas.

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, the excitation energy is applied uniformly or selectively to the source gas that has reached the vicinity of the substrate, but 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, 1 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 conductive wire 5 and generates heat. Although the substrate temperature is not particularly limited, it is generally desirable to be 300° C. or less in order to increase the optical band gap of the light emitting layer and obtain visible light emission.

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 is a type that utilizes heating.

There are types that allow a carrier gas to pass through the liquid raw material, and any of them may be used.The number of gas supply sources is not limited to four, and the number of types of silicon hydride compounds and carbon compounds of the above general formula to be used, as well as dilution. When using gas etc., the gas supply sources 6 to 9 in Figure 0 are selected as appropriate depending on the presence or absence of pre-mixing of the diluent gas and raw material gas, etc.
The one with a is the branch pipe, the one with b is the flow meter, and the one with C is the quantity U8! ! ! ! This is a valve for

Raw material gases 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. Or.

Gas is introduced into the chamber 1 alternately from each gas supply source.

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

13 is a regulator valve. When the inside of the chamber 1 is evacuated and brought into a reduced pressure state before introducing the raw material gas and the like, the atmospheric pressure inside the chamber is preferably 5×1 O−5 Torr or less, more preferably I×10−6 Torr or less. Further, in the state where the raw material gas and the like are introduced, the pressure within the chamber 1 is preferably IXjO-2 to 100 Torr, more preferably 5X10''2 to 10 Torr-c'.

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-SiC:H is formed. At this time, it is desirable that the thickness of the light-emitting layer be approximately 20 () to 10,000.

After this, an insulating layer similar to the insulating layer made of the above material is layered on top of the light emitting layer. Finally, a 7N metal electrode such as aluminum or gold is deposited.

Another production method is HOMOCVD, in which the reaction gas flowing into the 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. Simo.
nyi, Appl, Ph7s, Lett.

vol. 39 (1981) 9.73).

Even when this method is used to deposit non-9iC:H used as the light-emitting layer of the present invention, a film with a large optical band gap and a low localized level density 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. Then, a characteristic test was conducted.

The insulating layers 203 and 205 are 3000mm thick. O3
The light-emitting layer was formed using a thin film at a substrate temperature of 50° C. using C, H4 gas and Si2H6 gas as source gases. As the electrode 202, an ITO transparent electrode, an electrode 20
A for 6! ; L electrode was used. Light emitting device created in this way (sample NO, t) j,: 100V, IK
Hzc7) When a pulsed high frequency high electric field was applied, 1
Luminescence having an emission peak in the visible light region of 2 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 high-frequency electric field for a long time, we found that the stability was approximately 3 times better and the durability was 1.5 orders of magnitude better than the above conventional example. The result was that

Further, a light emitting device of sample No. 2.3 was 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.

Table 1 [Effects] As mentioned above, the light-emitting element of the present invention has a luminescence peak in the visible wavelength region, obtains a sufficient amount of luminescence, and improves luminous efficiency and reproducibility. Stability and lifespan can be dramatically increased.

[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---one substrate 102,106---electrode 10
3.105---P type conductive layer 104---N type conductive layer 201---Glass substrate 202---One transparent electrode 203.205---One insulating layer 204---One light emitting layer 206---One metal electrode No.
1 Kasumi No. 1 Koda

Claims (1)

[Claims] A light-emitting layer made of a non-single-crystal material containing silicon atoms, carbon atoms, and hydrogen atoms, a pair of electrically insulating layers sandwiching the light-emitting layer, and a pair of electrically insulating layers sandwiching the light-emitting layer and the insulating layer. at least one pair of electrodes connected to the light emitting layer, and the localized level density of the light emitting layer is 10^1^6 cm at the midgap.
A light-emitting element characterized in that the voltage is ＾-＾3・eV＾-＾1 or less.