JPH03225969A - Manufacture of light-emitting element - Google Patents

Abstract

PURPOSE:To control a light-emitting characteristic and to easily obtain a light- emitting layer complying with a demand by a method wherein a-C:Si, H film obtained by a P-CVD method are used as a hole injection layer and the light- emitting layer and the mixture amount of SiH4 gas is changed. CONSTITUTION:A hole injection layer 3 composed of a p-type amorphous carbon- based film is produced by a plasma chemical vapor deposition method by which a low-pressure reaction gas containing a hydrocarbon gas, hydrogenated silicon gas and a p-type impurity gas is glow-discharged inside a vacuum container and a decomposed gas is polymerized. A light-emitting layer 4 whose mixture ratio of a hydrocarbon gas to hydrogenated silicon gas is made larger than the mixture ratio in the hole injection layer 3 and which is composed on an amorphous carbon-based film is laminated on the hole injection layer. An electron injection layer 5 composed of an n-type amorphous silicon carbide film is laminated on the light-emitting layer 4 by a plasma chemical vapor deposition method by which a reaction gas which contains an n-type impurity gas and whose mixture ratio of hydrogenated silicon gas to a hydrocarbon gas is larger than the mixture ratio in the light-emitting layer 4 is polarized.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a method of manufacturing a light emitting device made of an amorphous semiconductor.

B1 Summary of the Invention The present invention provides a method for manufacturing a light emitting device in which a hole injection layer and an electron injection layer are laminated on both sides of a light emitting layer, in which low pressure hydrogen gas, hydrocarbon gas, and silicon hydride gas are reacted. An amorphous carbon-based film obtained by a plasma chemical vapor deposition method in the form of a gas is used as a light-emitting layer, and the mixing ratio of silicon hydride gas to hydrocarbon gas is set in the relationship of hole-injection layer <light-emitting layer><electron-injection layer. As a result, the light-emitting layer has good light-emitting properties, and this property can be fully brought out.

C. Conventional technology Conventionally, light-emitting materials such as GaAs, GaAsP, GaP, and GaAQAsZnSe, which are used for light-emitting diodes, have been used as light-emitting materials.
Examples include xTe+-x, Znx' Cd+-xTe, and CdTe.

B3 Problems to be solved by the invention However, with such conventional luminescent materials,
For example, in GaP, the peak wavelength (the wavelength at which the emission energy peaks) is 698 nm, and the optical energy gap is 1.76 eV.The peak wavelength and optical energy gap are unique to the luminescent material. . Therefore, when you want to change the luminescent properties of a luminescent material, it is necessary to select a luminescent material that has the required properties, and in some cases, you may not be able to obtain the properties derived from the required peak wavelength and optical energy gap. There were some problems that arose.

For this reason, it is being considered to generate an amorphous carbon-based material using the CVD method and apply it to a light-emitting material. Specifically, this amorphous carbon-based material is produced by maintaining the substrate temperature at, for example, 300°C or less in a vacuum container and applying a high frequency voltage or DC voltage in the presence of hydrogen gas of, for example, 133.3 mPa to 6 x 133.3 Pa to generate plasma. It is generated by performing the CVD method (P-CVD method).

Luminescent materials made of such substances have a large optical energy gap (in terms of heat resistance, the gap does not change up to 300°C), and can have arbitrary optical energy gaps and luminescent properties by controlling the conditions of the CVD method. Therefore, it has the advantage that it is easy to obtain a material that meets your needs. In a film made of this luminescent material, strong photoluminescence (PL) is observed depending on the size of the optical energy gap (Ego). E in Figure 3
The relationship between go and the peak value of P L is shown. In particular, since a film with an Ego of about 30 V emits blue-white light, there is a possibility of realizing a large-area blue light-emitting panel that takes advantage of the amorphous characteristics. Furthermore, by selecting various Ego's, it is also possible to create a light emitting element that repeatedly emits colors from red to blue.

Furthermore, regarding the PL intensity depending on the size of Ego, it shows very strong light emission when observed at room temperature, and is a light emitting element material (one that creates R, G, 83 elemental colors) that can be used to expand its application to flat panel displays with large screens. This is promising.

By the way, LE with a film made of such a substance as a light-emitting layer
When creating a D (Light Emitting Diode), an injection layer is required to inject electrons and holes into the light emitting layer, and as this injection layer, the above-mentioned amorphous carbon-based material of semiconducting p-type or n-type can be used. is the best. However, when using this material as an injection layer,
Target characteristics Ego>2eV, ρ (resistivity)≦I06
It is very difficult to make p-type and n-type films having Ω·cm, and this problem prevents the application of the above-mentioned amorphous carbon-based material to light-emitting devices.

An object of the present invention is to provide a method for manufacturing a light-emitting element that can impart arbitrary optical energy gaps and light-emitting characteristics to a light-emitting layer and can fully bring out the characteristics of the light-emitting layer.

E9 Means and operation for solving the problem The present invention is a plasma chemistry method in which a low-pressure reaction gas containing a hydrocarbon gas, a silicon hydride gas, and an n-type impurity gas is glow-discharged in a vacuum container to polymerize a decomposed gas. A process of generating a hole injection layer made of a p-type amorphous carbon film by a selective evaporation method, and using low-pressure hydrogen gas, hydrocarbon gas, and silicon hydride gas as reaction gases, and forming a silicon hydride gas for the hydrocarbon gas. a step of laminating a light-emitting layer made of an amorphous carbon-based film on the curved hole-injection layer by a plasma chemical vapor deposition method in which the mixing ratio of iJ is larger than the same mixing ratio of the hole-injection layer; A reaction gas containing silicon hydride gas, silicon hydride gas, and n-type impurity gas, in which the mixing ratio of silicon hydride gas to hydrocarbon gas is larger than the same mixing ratio in the light emitting layer, is subjected to claw discharge in a vacuum container to produce decomposed gas. The method is characterized in that it includes a step of laminating an electron injection layer made of an n-type amorphous silicon carbide film on the light emitting layer by a plasma chemical vapor deposition method of polymerizing.

Further, in the present invention, it is preferable that the substrate temperature in the step of forming the hole injection layer is higher than the substrate temperature in each step of forming the light emitting layer and the electron injection layer.

F. Example FIG. 1 is a block diagram showing an example of a light emitting device obtained by the method of the present invention. In FIG. 1, for example, a glass substrate with an area of about 63 cyn2, 2 a transparent electrode made of tin oxide, and 3 a p-type amorphous carbon-based film doped with B'' and having a thickness of about 30 nm (hereinafter ra-C) are shown. Si, H film J
4 is a light-emitting layer made of a-C:Si,H film with a thickness of 300 nm, and 5 is an n-type amorphous silicon carbide film doped with P5' and with a thickness of about 50 nm ( 6 is an aluminum electrode.

Each amorphous thin film can be produced using a general P-CVD apparatus equipped with a vacuum chamber, a gas introduction system, a gas exhaust system, a high frequency power supply (or a DC power supply), and the like.

Here are three examples of manufacturing conditions for manufacturing light emitting devices (
Samples 1 to 3) are listed below.

(+, ) Regarding sample 1 ■ Hole injection layer gas pressure inside vacuum container 26.7Pa (0.2To
rr) Substrate temperature 275℃ CH4 gas: SiH, gas 9:1 B2Ho gas (CI-14 gas + SiH4 gas)
3:]000 High frequency power source power 0W (0 for input electrode area] 25 W/am2) ■ Light emitting layer mixed gas (CH, H2 and 5iH4) in vacuum container pressure 2
6.7 Pa (0 Torr) Mixing ratio of 5iI44 gas to CI-1: 12% Substrate temperature 250°C High frequency power source power 0W ■Electron injection layer vacuum vessel internal gas pressure 26.7 Pa (0 'I'orr) Substrate Temperature 506C CH4 gas: SjH, gas 3.2 PI (3 gases (CH, gas + 5iHa gas) Regarding ■ Hole injection layer H4 iHt was manufactured under the same conditions as Sample 1 except that it was 1.

(2) Light emitting layer This was manufactured under the same conditions as Sample 1 except that the mixing ratio of SiH4 gas to CH4 gas was 15%.

■Electron injection layer It was manufactured under the same conditions as Sample 1.

(3) About sample 3 ■Hole injection layer Cl44: S i H4 Same as sample 1 except for ■ Manufactured under the following conditions.

2 (2) Light-emitting layer This was manufactured under the same conditions as Sample I except that the mixing ratio of SiH4 gas to CH4 gas was 25%.

■Electron injection layer Manufactured under the same conditions as Sample 1.

When the relationship between wavelength and EL intensity was investigated for each of the above samples 1 to 3, the relationship shown in FIG. 3 was obtained. In the same figure, solid lines ■ to ■ correspond to samples 1 to 3, respectively. In order to obtain such good luminescent properties, the mixing ratio of silicon hydride gas to methane gas used for forming the luminescent layer must be 5.
It is preferably 35%. However, in the production steps of the hole injection layer, light emitting layer, and electron injection layer, the concentrations of silicon hydride gas relative to methane gas are AP and AL, respectively.

When AN, it is necessary to satisfy A p < A I and < A N.

The reason for this is to make the light-emitting layer smaller than the hole-injection layer and to make the electron-injection layer smaller than the light-emission layer in terms of the carbon atom content relative to the silicon atom content.

It was found that all Samples 1 to 3 exhibited sufficient luminescence that could be observed visually, and had sufficient luminescent properties. The forward bias voltage used in the test was 5V, and the current density was 20
It was 0 mA/cz2. Regarding the substrate temperature, a-
C: Limited by the heat resistance of Si, H film, a-C:
When the Si, I-1 film is heated to 350°C or higher, Ego decreases and the film thickness becomes small, so about 350°C is the limit.

Here, in the above samples 1 to 3, CH4 gas is used as the hydrocarbon gas used in the process of generating each layer, but the present invention is not limited to CH4 gas, and for example, C2H4 gas may be used. Good too. In this way C2
The manufacturing conditions for samples (4 to 6) manufactured using H4 gas will be described below.

(1) Regarding sample 4 ■ Hole injection layer gas pressure inside vacuum container 26.7Pa (0.2To
rr) Substrate temperature 275°CC2H
4 gas: SiH4 gas 9.1 B 2 Ho gas: (C2F (, gas + 5i) L gas)
3:1000 High frequency power supply power 10W (0 to input electrode area, 125 W/cm2) ■ Light emitting layer Mixed gas in vacuum container (C2H4, H2 and S jH4) Pressure 26.7P2L (0.2 Torr) 5 SiH4 to C2H4 Gas mixture ratio 12% Substrate temperature 250°C High frequency power supply power 0W ■Electron injection layer vacuum chamber internal gas pressure 6 7 Pa (0 'I'orr) Substrate temperature 250°C C2H4 gas SiH + gas 3:2 PI43 gas (C2H4 gas + SiH4 gas) 5.8 000 High frequency power source power 0W (0.125W/c for the input electrode area) (2) Regarding sample 5■ Hole injection layer C7H4: Same as sample I except that SiH4 was set to 1 Manufactured under the following conditions.

(2) Light emitting layer 6 This was manufactured under the same conditions as Sample 1 except that the mixing ratio of SiH4 gas to C2H gas was 15%.

■Electron injection layer Manufactured under the same conditions as Sample I.

(3) Regarding Sample 6 ■ Hole injection layer C2H4: Manufactured under the same conditions as Sample 1 except that S i H*-'-4.1.

(2) Light Emitting Layer The light emitting layer was manufactured under the same conditions as Sample 1 except that the mixing ratio of Sigh gas to C2H4 gas was 25%.

■Electron injection layer It was manufactured under the same conditions as Sample 1.

When the relationship between wavelength and EL intensity was investigated for each of Samples 4 to 6 listed below, it was found that the relationship was the same as that for Samples 1 to 3, respectively. In order to obtain such good luminescent properties, the concentration of silicon hydride gas (concentration (mixing ratio) to ethylene gas) used for forming the luminescent layer is preferably 2.5 to 20%.

It was found that all Samples 4 to 6 exhibited luminescence that could be sufficiently observed visually, and had sufficient luminescence characteristics as in the case of Samples 1 to 3. The conditions in the luminescence test were the same as Samples 1-3.

In addition, the peak values of luminescence energy when an electric field was applied to all of the above samples 1 to 6 were quite high.

The reason for this is that in the above embodiment, the substrate temperature in the hole injection layer generation step is higher than the substrate temperature in the light emitting layer and electron injection layer generation steps. It is sometimes thought that boron in the hole injection layer is difficult to diffuse into the light emitting layer.

By the way, p-type aC:5iSH film, 1-type aC:Si
When a p-1-n type cell is made by laminating a H film and an n-type a-SiC film, the junction between each layer becomes a heterojunction. The problem was whether holes (electrons) were successfully injected from the layer to the light-emitting layer, but when we investigated the diode characteristics of samples 1 to 6, they showed good characteristics and good junctions. It turned out that there was.

G8 Effect of the invention According to the invention, a-C obtained by P-CVD method:
Since the SiH film is used as the hole injection layer and the light emitting layer, it has a large optical energy top and can emit light by changing the mixing amount of SiH + gas while maintaining the predetermined relationship between each layer. Since the characteristics can be controlled, a light-emitting layer that meets your needs can be easily obtained.

Furthermore, regarding the carbon atom content relative to the silicon atom content, the emissive layer is made smaller than the hole injection layer, and the electron resident layer is made smaller than the emissive layer. Even if the electrons and holes are combined with each other, electrons and holes can be successfully injected into the light emitting layer, the characteristics of the light emitting layer can be fully brought out, and a light emitting device with high practical value can be obtained.

In addition, since the substrate temperature in the hole injection layer generation process is higher than the substrate temperature in the emission layer and electron injection layer generation processes, it is possible to prevent impurities in the hole injection layer from diffusing into the emission layer. The damage to the light emitting layer is small and its characteristics are not lost.

0

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing a light emitting element according to an embodiment of the present invention,
FIG. 2 is a characteristic diagram showing the light emitting characteristics of the diode, and FIG. 3 is a characteristic diagram showing the relationship between Ego and PL of the amorphous carbon film. 3. Hole injection layer, 4. Light emitting layer, 5. Electron injection layer. Figure 1 Structure of Example 1...Substrate 2.6...Electrode 3...Hole injection layer 4...Light emitting layer 5...Electron injection layer

Claims (2)

[Claims] (1) A p-type amorphous carbon-based film is produced using a plasma chemical vapor deposition method in which a low-pressure reaction gas containing hydrocarbon gas, silicon hydride gas, and p-type impurity gas is glow-discharged in a vacuum container and the decomposed gas is polymerized. A step of generating a hole injection layer consisting of low pressure hydrogen gas, hydrocarbon gas, and silicon hydride gas as reaction gases, and adjusting the mixing ratio of silicon hydride gas to hydrocarbon gas to the same mixing ratio in the hole injection layer. a step of laminating a light-emitting layer made of an amorphous carbon-based film on the hole injection layer by a plasma chemical vapor deposition method with a ratio larger than An n-type amorphous silicon carbide film is formed by a plasma chemical vapor deposition method in which a reaction gas in which the mixing ratio of silicon hydride gas to hydrogen gas is larger than the same mixing ratio in the light emitting layer is caused to glow discharge in a vacuum container to polymerize the decomposed gas. A method for manufacturing a light emitting device, comprising the step of laminating an electron injection layer consisting of the following on the light emitting layer. (2) Manufacturing the light emitting device according to claim (1), wherein the substrate temperature in the step of forming the hole injection layer is set to be higher than the substrate temperature in each step of forming the light emitting layer and the electron injection layer. Method.