JPS6255971A - Light emitting element - Google Patents

Abstract

PURPOSE:To improve the light emitting efficiency of a light emitting element by composing a light emitting layer of the first and second intermediate layers of P-type and N-type amorphous Si which contain fluorine atoms when laminating upper and lower electrodes for holding a light emitting layer therebetween on a substrate as the light emitting element, and specifying the optical band gap and quantum efficiency. CONSTITUTION:A lower layer 102 is coated as required to enhance the bondability with an electrode layer 103 on a substrate 101, and the lower electrode layer 103 of the prescribed layer is formed thereon. Then, when a light emitting layer 104 is formed thereon, the layer 104 is formed of a laminated of P-type and N-type amorphous Si intermediate layers which contain fluorine atoms, optical band gaps are selected to 2.0eV or higher, and the quantum efficiency is set to 10<-4> or more. Here, these intermediate layers may be of I-type, or may be of Si which does not contain an impurity. Thereafter, an upper electrode 105 is coated on the layer 104 as a light emitting element. Thus, the peak value of emitting light is obtained in a visible wavelength range to improve the light emitting efficiency and the lifetime.

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.
, Phys., Lett.

29 (1976), PP620-622. J.

1. Pankou, D.E., Carlson.

Jpn, J., Appl, Phys, 21 (1982)
PP473-475. Non-single crystal silicon containing hydrogen atoms (hereinafter referred to as
rnOn-5i (denoted as HJ) is a material that is attracting attention because it can be applied with semiconductor engineering similar to single crystal silicon, and it may have excellent latent properties. It is one of the

The structure of the light-emitting element using non-5t:H as a light-emitting material described in the above cited document includes a P-type conductive layer (P layer) containing P-type impurities, and a P-type conductive layer (P layer) containing both P-type and N-type impurities. It has a homojunction in which a layer containing no impurities (non-doped layer) and an N-type conductive layer (N layer) containing N-type impurities are laminated.

[Problem to be solved]

However, conventionally reported light-emitting devices with such configurations do not emit a sufficient amount of light in the visible light region, and in addition, have low emission intensity and short lifetime.1. There are many points that need to be improved in practical terms. As one of the above improvement plans, non-3i:H
Adding carbon atoms to expand the optical bandgap,
Attempts have been made to obtain light emission in the visible wavelength region, but practical problems still remain, and it has not yet been industrialized as a light source element or display element 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 a sufficient amount of light emitted in the visible wavelength region 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 an N-type conductive layer and a semiconductor intermediate layer (I).
, the P-type conductive layer, and the second semiconducting intermediate layer (II),
comprising a light emitting layer having a layered structure stacked in this order and at least one pair of electrodes electrically connected to the light emitting layer;
The light emitting layer is made of non-single crystal silicon containing fluorine atoms and has an optical band gap of 2. It is characterized by being Oe V or higher.

[For production]

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

The present invention will be specifically explained below 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 includes a P-type conductive layer (P layer), a first semiconductor intermediate layer (I), and an N-type conductive layer (N layer) on an electrode 103 provided on a base 101. and a second semiconductor intermediate layer (II), and an electrode 105 provided on the light emitting layer 104.

Reference numeral 102 denotes an undercoat layer, which is provided for the purpose of improving the adhesion between the base 101 and the electrode 103, and is not necessarily required.

When the light emitting device shown in FIG. 1 is used as a planar light emitting device, the electrode 103 and/or the electrode 105 must be transparent if the color of the emitted light is to be utilized, and the amount of light emitted is If the material is to be used, it is desirable that the material be transparent to the emitted light. When emitted light is extracted from the electrode 103 side, it is preferable that the base 101 be transparent like the electrode 103 or be Δ-optical with respect to the emitted light.

The light-emitting element of the present invention includes a P-type conductive layer (P layer), a first semiconductor intermediate layer (I), an N-type conductive layer (N layer), and a second semiconductor intermediate layer (I), which constitute the light-emitting layer 104, as shown in @. Semiconducting intermediate layer (II
) contains fluorine atoms (F) and optionally hydrogen atoms (II) (hereinafter referred to as rnon-S).
i: F(II)J).

The light-emitting layer 104 has a layer structure in which the above-mentioned P layer, intermediate layer (I), N layer, and intermediate layer (TI) are laminated in this order, and the layer structure has the purpose of improving the luminescent properties. It is desirable that the process be repeated periodically. In that case, the number of repetition periods is determined as appropriate depending on the layer thickness of each layer within the period, but if each layer is made thin enough to produce a quantum mechanical size effect, the number of repetition periods is approximately 10 or more. It is desirable to be able to obtain a cycle to several tens of cycles. In that case, both ends of the light emitting layer 104 do not necessarily have to be in the order of the layer structure of the periodic layer structure.

That is, for example, 52 layers, middle layer (I), N layer, middle layer (
II)] n-N layer/semiconductor intermediate layer (III)/P
It is considered to be a layer. At this time, the middle layer (1).

The intermediate layer (II) and the intermediate layer ([+) may have different electrical conductivity properties, or may have similar electrical conductivity properties.

In the present invention, the layer thicknesses of the P layer, the intermediate layer (I), the N layer, and the intermediate layer (II) may be changed by introducing a superlattice structure or by using a simple repeating periodic layer structure. Further, it is selected as desired, taking into consideration the light emitting characteristics required for the device.

In the light emitting device of the present invention, the layer thickness of the P layer and the N layer is preferably 5 to 10,000, more preferably 8
It is desirable to have 10 to 7,000 people, most preferably 10 to 7,000 people.

The layer thickness of the intermediate layer (I) and the intermediate layer (II) is preferably 5 to 15,000 layers, more preferably 8 to 10 layers.
000 people, optimally 10 to 8000 people.

In the light emitting device of the present invention, the semiconducting intermediate layer CI) and the semiconducting intermediate layer (II) are formed as a conductive layer exhibiting intrinsic conductive properties or a slightly N-type or P-type conductive layer. be done. And no n-5i : F (II
According to its general tendency, a layer composed of
Since it shows a type tendency, a small amount of P-type impurity is contained in order to form an I-type conductive layer.

In the present invention, in order to introduce a superlattice structure, P layer, N
The layer thicknesses of the intermediate layer (CI) and the intermediate layer (II) are determined as desired depending on the material constituting each layer and the required device characteristics, but the quantum size effect is preferably 5 to 100 people, more preferably 8 to 80 people, and optimally 10 to 70 people. In particular, it is desirable to set the wavelength to about the dove σ wavelength of the carrier or about the mean free path of the carrier.

The fluorine atoms (F) contained in the light-emitting layer compensate for the free dumping of silicon atoms, and its content depends on the semiconductor properties of the formed layer.

It is an important factor that influences the optical properties, structural stability, heat resistance, and light emitting properties of the device and its stability, and in the present invention, the content of fluorine atoms (F) is preferably silicon atoms. 5 atomic PPM to 25 atomic %, more preferably 10 atomic PPM to 20 atomic %, optimally 50 atomic PP
M is 15 atomic %.

The content of hydrogen atoms (II) contained as necessary is:
It is determined as desired depending on the relationship with the fluorine atom (F) content and the device characteristics required for the device, but is preferably 0.01 to 35 at.%, more preferably 0.1 to 30 at.%.
The content is preferably 1 to 30 atomic %. Further, it is desirable that the total amount of fluorine atoms (F) and hydrogen atoms (II) is contained in the layer so that the total amount does not exceed 40 at %.

The P-type conductive layer and the N-type conductive layer constituting the light-emitting layer are P\I! which give P-type conductive characteristics when the layers are formed. Impurity or N
P in a layer that contains N-type impurities that change the type conductivity, or is already composed of non-5i:F(II).
Type or N type impurities may be implanted by means such as ion implantation.

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

Afl (aluminum), Ga (gallium).

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

N-type impurities include atoms belonging to Group V of the periodic table (Group V atoms), such as P (phosphorus), As (arsenic), and Sb.
(antimony), Bi (bismal), etc.
In particular, P and As are preferably used.

The content of these impurities is appropriately determined as desired, taking into account the electrical conductivity properties of the layer to be formed, the local level density in the midgap, and the like.

In the present invention, the above-mentioned structure can be provided by employing a photo-CVD method (deposited film formation method by a chemical vapor phase method using light energy for reaction), and the above-mentioned structure can be provided by adopting the photo-CVD method (deposited film formation method by a 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.

In an uninvented light-emitting device, carriers (electrons, holes) injected into the light-emitting layer from a pair of electrodes sandwiching the light-emitting layer are moved near the N layer by the internal electric field of the semiconductor intermediate layer. Since holes are accumulated in the vicinity of the P layer, the lifetimes of electrons and holes are longer than in a normal bulk case. Therefore, the luminous efficiency is extremely high.

In addition, since it has a multilayer structure formed by periodic lamination, there are multiple effective recombination regions that contribute to the emission of electrons and holes, making it possible to further improve the luminous efficiency.

In the light emitting device of the present invention, the applied bias voltage is selected so that a forward bias is applied to the junction of each layer, and the probability of recombination of electrons and holes once injected into the light emitting layer is reduced. The magnitude of the bias is adjusted so that it becomes higher.

As for the bias at that time, AC or pulse bias is preferably used at the same time as DC bias.

In the present invention, in order to obtain an emission wavelength in the visible range, it is desirable that the optical bandgap Egopt of each layer constituting the light emitting layer be 2.0 eV or more.

Each layer constituting the light emitting layer has localized 1015 cnr3 e at the center of the optical band gap (mid gap).
It is preferable to use V-double.

In this way, by controlling the physical property values of each layer, the recombination efficiency can be dramatically improved, and therefore the luminous efficiency can be further improved.

Further, by controlling the distribution of recombination levels so that the external quantum efficiency of the light emitting layer is 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 may be performed by setting appropriate conditions to, for example, HOMOCVD.
It may be performed by a method such as a method, a plasma CVD method, or the like.

As materials constituting the substrate and electrodes 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.

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, in the case of glass, its surface is coated with NiCr, A, Cr, Mo, Au, Ir, and Nb.

Ta, V, Ti, Pt, Pd, In203Sn02,
Conductivity can be imparted by providing a thin film made of ITO (In203+5n02), etc., or if it is a synthetic resin film such as polyester film, NiCr,
AM, 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, 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 200° 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, which are provided with an appropriate vaporizer when liquid raw materials are used in normal conditions.

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, 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, to the symbols of gas supply sources 6 to 9, a is attached to the branch pipe, b is attached to the flowmeter, and C is attached to the pressure meter that measures the pressure on the high pressure side of each flowmeter. , d or e are valves for opening/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 gas introduced into the chamber 1. 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 regulator valve. 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 5X to -5 Torr or less, more preferably 1 x 1 O-GTor or less. In addition, in the state where the raw material gas etc. is introduced,
The pressure in chamber 1 is preferably between I x 10-2 and 100
Torr, more preferably 5X10-2 to 10 Torr
It is preferable that it be r.

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 the wavelength range does not matter 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 raw material gas etc. 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 170 layers of 600 mm thick are formed thereon as conductive layers by sputtering. The resistance value of the membrane is approximately 50Ω/hole.

Next, the conductive substrate 3 is placed in a substrate holder 2 of a photo-CVD apparatus as shown in FIG. 4, and first evacuated to a vacuum using a pump 12. When the degree of vacuum becomes about 1X10-8 or less, the temperature of the substrate holder 2 is raised and the substrate temperature is set as desired. In the present invention, the substrate temperature is
Preferably -20°C to 200°C, more preferably 0°C to 15°C
It is desirable that the temperature be 0°C.

Next, SiF6. SiH2F2. Fluorinated silane gas such as SiF4 gas and SiH4, Si2H6 as necessary
, 5i3HB, etc., and if necessary, impurity introduction gas (B2H6, BF3, PH3, , P2
H4.

PF3, etc.) into the deposition chamber 1 using 6.7 and 8.9 cylinders and flow meters 6b to 9b. At this time H2
, Ar, He, or other gases may be introduced at the same time.

Next, a low-pressure mercury lamp was used to emit light at 185 nm from the top of the deposition chamber l.
of light is irradiated onto the substrate with an intensity of approximately 5-50 mW 70 m2 to deposit the layer.

In order to form P-type and N-type conductive layers, at the same time as the fluorinated silane gas, in the case of P-type, a gas such as B2H6 is mixed with a gas such as H2 or Ar to adjust the concentration. It flows into the deposition chamber l.

In addition, in the case of N type, gases such as PH3, AsH3, etc. are replaced with H2,
It mixes with Ar gas 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. The P-type conductive layer, the semiconductor intermediate layer, and the N-type conductive layer are controlled by changing the light intensity and light irradiation time.

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 as desired, 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 fτ and hν, the local level density is determined by the FE method, and the quantum efficiency is determined by the light emission of the diode. It can be determined from the characteristics (temperature dependence).

Example 1 Using an ITO substrate as a base, a layer was created at a substrate temperature of 45°C. The P-type conductive layer is B2H6/ (S i 2 F
At a flow rate ratio of 6+S i 2H6) = 10-2, Si
Flow rate ratio of 2F6/5i2Fs=2, total flow rate 120SCC
M (hydrogen dilution), N-type conductive layer is PH3/S i 2H6
=Flow rate ratio of IO-2, total flow rate 1203 CCM (hydrogen dilution), semiconducting intermediate layers (I) and (II) are S i 2
H6 and Si2F6 were introduced into the deposition chamber 1 at a flow rate of 40 SCCM and 80 SCCM, respectively, and the pressure was set to 0. IT
Each layer was created by reacting under the following conditions: orr and light intensity of 40 mW/cm2 (7). The layer thickness of the P-type conductive layer at this time is 2
5 people, the layer thickness of the semiconducting intermediate layers CI) and (II) is 2
5 people for the N-type conduction layer, 25 people for the N-type conduction layer, and this P layer/intermediate layer (I
) eNN layer (intermediate layer II) is stacked repeatedly for 20 cycles as one unit, and then N layer and intermediate layer (I) are formed with the above layer thickness.
and P layer were laminated. .

On the upper surface of the light-emitting layer formed in this way, 100 letters A are written.
It was evaporated to a thickness of 0 and used as the upper electrode.

The obtained light emitting device emits white light, and its optical bandgap is shown in Table 1.

Example 2 Same device as Example 1, same conditions, substrate temperature 20°C
Layer formation was performed using the following settings.

The layer thickness of the P-type conductive layer at this time was 30 layers, and the semiconductor intermediate layer (
The layer thickness for I) and (II) is 30 people.

The layer thickness of the N-type conductive layer was 30 layers. P layer Φ layer (I)
・The repetition of the N-layer conflict layer (II) was set to 20 cycles. The obtained light emitting device emits white light and its optical band gap is shown in Table 1.

Example 3 Using the same apparatus as Example 2, the corresponding layer was created under the same conditions, the layer thickness of the P-type conductive layer was 200, and the middle layer (
The layer thickness of I) and intermediate layer (n) is 1500 layers, the layer thickness of N-type conductive layer is 200 layers, and these layers are P layer and layer (I).
- Laminated in a layered structure of N layer, layer (II), P layer, layer (I), and N layer. A light emitting device with such a structure exhibited colored light emission. The measured optical bandgaps of the devices are shown in Table 1.

Table 1 From the above Examples 1 to 3, the light emitting device of the present invention has a conventional n
It was found that a light emitting element using on-5i:H has a small amount of light emission in the visible region and a low intensity, but white light emission with higher intensity can be obtained.

Furthermore, when the lifespan of the light-emitting elements in each example was measured, the lifespan was an order of magnitude higher than that of conventional light-emitting elements.
The reproducibility was also good, and the luminescent properties were always stable during lifetime measurements.

〔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, and can improve luminous efficiency and reproducibility.1. It can be increased to

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the layer structure of a preferred embodiment of the light emitting device of the present invention, and FIG. 2 is a schematic diagram showing an example of an apparatus for producing the light emitting device of the present invention.

Claims (5)

[Claims] (1) N-type conductive layer, first semiconductor intermediate layer (I) and P
A light-emitting layer having a layer structure in which a type conductive layer and a second semiconductor intermediate layer (II) are laminated in this order, and at least one pair of electrodes electrically connected to the light-emitting layer, A light emitting device, wherein the light emitting layer is made of non-single crystal silicon containing fluorine atoms and has an optical band gap of 2.0 eV or more. (2) The light emitting device according to claim 1, wherein the first semiconducting intermediate layer (I) and/or the second semiconducting intermediate layer (II) have I-type conductivity. (3) The first semiconducting intermediate layer (I) and/or the second semiconducting intermediate layer (II) do not contain P-type and N-type impurities. Light emitting element. (4) Claim 1, wherein the layer structure is periodic.
The light-emitting element described in . (5) The light emitting device according to claim 1, wherein the light emitting layer has a quantum efficiency of 10^-^4% or more.