JPS6249681A - Light emitting element - Google Patents

Abstract

PURPOSE:To improve a light emitting efficiency and a reproducibility by a method wherein the local level density of light emitting layer composed of non-single crystalline material containing silicon atoms, carbon atoms and fluorine atoms is specified not to exceed 5X10<16>cm<-3> eV<-1> at midgap. CONSTITUTION:A light emitting element is composed of a lower electrode 102 provided on a substrate 101, a lower electrode insulating layer 103, a light emitting layer 104, an upper electric insulating layer 105 and an upper electrode 106 provided on said layer 105. The light emitting layer 104 is composed of non-single crystal silicon containing silicon atoms, carbon atoms and fluorine atoms as well as hydrogen atoms as necessary. The light emitting pack wavelength can be made the specified wavelength in the visible region while improving the efficiency of recoupling by means of changing physical property values of the light emitting layer 104.

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 to constitute the light-emitting layer of a light-emitting element, and among them, for example, Appl.
, Phys, Lett, 42(11]113),
PP432-434゜H, Munekata, H, Ku
kimoto, ya Jpn, J, Appl, Ph7s, 2
1 (1!+82) PP473-475, Tak
The hydrogenated amorphous silicon carbide described in ahashi et al. can be applied to the same semiconductor engineering as 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 as light source elements and display elements used in O, AR devices, etc.

It has not yet been industrialized.

〔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 has silicon atoms (sB) and carbon atoms (C
) and a non-single-crystal material containing fluorine atoms (F); a pair of electrically insulating layers sandwiching the light-emitting layer;
At least one pair of electrical machines is formed by sandwiching these light-emitting layers and insulating layers and electrically connecting them.

[Function] By having the above structure, the light emitting element of the present invention has the following effects:
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.
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 includes non-single-crystal silicon (hereinafter referred to as r
non-5iC: abbreviated as F(H)J).

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 5 atoms PPM- with respect to the sum of silicon atoms and carbon atoms. The content of hydrogen atoms (H) contained as necessary is desirably 25 at%, more preferably 1O atoms PPM to 20 at%, and optimally 50 to 15 at%. Although it is determined as desired depending on the relationship with the content of fluorine atoms (F) and the device characteristics required for the device, it is preferably 0.01 to 35 atoms based on the sum of silicon atoms and carbon atoms. %, more preferably 0.1 to 30 atomic %, optimally 1 to 30 atomic %, and the total amount of fluorine atoms (F) and hydrogen atoms (H) is at most 40 atomic %. It is desirable that each atom is contained in the layer so that the amount does not exceed .

By appropriately selecting the ratio of silicon atoms (St) and carbon atoms (C) as desired, the emission peak wavelength 9
Emission intensity can be adjusted, and in the present invention, 5i
If expressed as the value of X of xC1x, preferably 0.05≦X≦0
．． 99, more preferably 0.1≦X≦0.9. Optimally 0
．． It is desirable that 15≦X≦0.85.

In the present invention, the above-mentioned structure can be provided by employing the photoCVD method (deposited film formation method by chemical vapor phase method using light energy for reaction), and the raw materials for forming one light emitting layer are 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 non-SiC:F(H), and is preferably formed as a layer exhibiting so-called intrinsic (type I) semiconductor characteristics.

A layer composed of non-SiC:F(H) shows a slight N-type tendency when it does not contain so-called P-type or N-type impurities, so the light-emitting layer 104 is an I-type layer. To form a conductive layer, a slight 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 is added when forming one layer, or a layer already composed of non-SiC:F(H) is added. P
Type impurities may be implanted by means such as ion implantation.

P-type impurities include atoms belonging to the so-called Li group of the periodic table (Group atoms), namely B (boron), /Ml (aluminum), Ga (gallium), In (indium), Te (
thallium), etc., and particularly preferably used are B,
It is Ga.

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 to the emitted light in order to extract the emitted light to the outside. In the present invention, specifically, Y20 is preferably used as a material constituting the insulating layers 103 and 105.
3, S 102 1 Amorphous silicon oxide (a-3
ixOixHowever, 0 < X < 1) + Hf
O2* S l 3N a + amorphous silicon nitride (a-3iyNI-yHowever.

o<y<t), A pattern 203, PbTiO3, amorphous (
1) Examples include B aT i 03 and T a7 o5.

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 the electrode 202 and the metal electrode 206 are electrically connected to connection terminals of a power source 207 for applying a pulsed or sawtooth high frequency high electric field, respectively. .

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
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 10''.
cm-3e e V-' or less, more preferably I X 1
It is desirable that the value be less than 0 l6cm-3eV-'.

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 method is not limited to the photo-CVD method, and may be performed by, for example, the HOMOCVD method, the plasma CVD method, etc. by appropriately setting the desired conditions.

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 N iCr + stainless steel.

Examples include AJL, Cr, Mo, Au, Nb, Ta, V, and Ti.

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, Ai
, Cr, Mo, Au, Ir.

Nb, Ta, V, Ti, PL, Pd, In2O3゜5n
Conductivity is imparted by providing a thin film made of 02, ITO (In203 +5n02), etc., or a synthetic resin film such as a polyester film -t'
If present, NiC, r, AL; L, Ag.

P b , Z n , N i , A u' ,
Cr, Mo, Ir.

Conductivity is imparted to the surface by providing a thin film of metal such as Nb, Ta, V, Ti, Pt, etc. on the surface by vacuum evaporation, electron beam evaporation, sputtering, etc., or by laminating the surface with the metal. Ru.

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, for introducing silicon atoms and fluorine atoms, is 5i7F6°SiH2F2. Examples include fluorinated silane gas such as 5iFa, and for introducing silicon atoms and hydrogen atoms, the general formula 5inH2n (n=
3.

Examples include cyclic silicon hydride compounds represented by S inH2n+2 (n=2, -=-) and linear or branched chain silicon hydride compounds represented by S i nH2n+2 (n=2, -=-) .

The raw material gas for introducing carbon atoms is CH4.

C2H & , C3H6, C4Hl (1, C2H4.

C3H6, CaHe, C2H2, CH3C2HlC
Mention may be made of H gaseous or easily gasified hydrocarbon compounds such as 4H6.

In addition, (CH3)2SiH2(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.

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. 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. In the figure, the gas supply sources 6 to 9 with a suffix a are branch pipes, which are appropriately selected depending on the presence or absence of premixing of the dilution gas and raw material gas.

Those marked with b are flow meters, those marked with C are pressure gauges that measure the pressure on the high pressure side of each flow meter, and those marked with d or e are used to open and close each gas flow and adjust the flow rate. It's a valve.

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

Gases are introduced into the chamber 1 alternately from each gas 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 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 is evacuated to reduce the pressure before introducing the raw material gas etc., the atmospheric pressure in the chamber is preferably 5×1 O-Torr or less, more preferably I×10-”Torr or less. ,
When raw material gas etc. are introduced, the pressure inside the chamber 1 is as follows:
Preferably it is 1X10-2 to 100 Torr, more preferably 5X10-2 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-SiG:F(H) is formed. At this time,
The thickness of the light-emitting layer is preferably about 200A to 10,000A.

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 metal electrode such as aluminum or gold is deposited.

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, P.I.
ck,and E,E,Simonyi,Appl.
Pbys, Lett.

vol. 313 (1981) p. 73).

non-SiC:F(H) used as light emitting layer of the present invention
Even when using this method when depositing optical bands,
It is possible to create a film with a large gap and a low density of single localized levels.

〔Example〕

Using the photo-CVD apparatus shown in FIG. 3 described above, a light emitting element having the structure shown in FIG. Then, a characteristic test was conducted.

The insulating layers 203 and 205 are Y2O3 with a thickness of 3000A.
A thin film was used, and the light-emitting layer was formed using a low-pressure mercury lamp at a substrate temperature of 300° C. using C2H4 gas, Si2H6 gas, and 5i7F6 gas as source gases. As for the electrode 202.

As the ITO transparent electrode and the electrode 206, an A pattern electrode was used. The light-emitting device created in this way (when a sump wave high electric field was applied, light emission with an emission peak in the visible light wave of #ft-L was obtained. This value is more than an order of magnitude larger than that of a light-emitting device using When stability and durability were tested, the results showed that the stability was about 3 times better and the durability was 1.5 orders of magnitude better than the conventional example.

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.

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

Further, 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 range, obtains a sufficient amount of luminescence, improves luminous efficiency and reproducibility, and improves luminescent properties. The stability and lifespan of can be dramatically increased.

[Brief explanation of the drawing]

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.

Claims (1)

[Claims] A light-emitting layer made of a non-single crystal material containing silicon atoms, carbon atoms, and fluorine 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 5×10^1^6 at the midgap.
A light-emitting element characterized by having a luminance of cm^-^3・eV^-^1 or less.