JPH02260669A - Manufacture of light emitting element - Google Patents

Abstract

PURPOSE:To enable a light emitting element of this design to display its excellent light emitting characteristic by a method wherein an amorphous carbon film is used as a light emitting layer, and an amorphous silicon carbide layer is used as an injection layer of holes and electrons. CONSTITUTION:A reaction gas of a mixed gas of CH4, SiH4, and B2H6 diluted with an H2 gas is introduced into a vacuum chamber 71, a high frequency voltage is applied to the mixed gas, and the decomposed gas is polymerized on a substrate 8 for the formation of a P-type a-SiC film 3. Then, the chamber 71 is vacuumed, the substrate 8 is transferred into a chamber 72, hydrocarbon gas and H2 gas are introduced into the chamber 72, a high frequency voltage is applied to the above mixed gas to form an a-C:H light emitting layer 4 on the layer 3 in lamination, then the chamber 72 is vacuumed, the substrate 8 is transferred into a chamber 73, a PH3 gas is used in the chamber 73 in place of a B2H6 gas utilized in the chamber 71 to form an N-type a-SiC film 5, an electrode film 6 is formed thereon, and thus a P-i-N type light emitting element is obtained. This single light emitting layer is formed in an amorphous superlattice structure, a C2H4 a-C:H, N film is used as a well layer which serves as a recombination section of electrons and holes, and a CH4 a-C:H film is used as a barrier layer.

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 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 an amorphous carbon-based film obtained by a sputter impurity introduction plasma CVD method is used as a light emitting layer. By using an amorphous silicon carbide film obtained by the plasma CVD method as the hole and electron injection layers, the light-emitting layer has good light-emitting properties, and these properties can be fully brought out. .

C0 Conventional technology Conventionally, light-emitting materials include GaAs, GaAsP, GaP, GaA&As, and Zn5, which are materials for light-emitting diodes.
Examples include exTe+-x and ZnS.

However, in 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, and 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 having the required characteristics, and there is a problem in that there are cases in which the required characteristics due to the wavelength and optical energy gap cannot be obtained.

For these reasons, an attempt was made to generate an amorphous carbon-based material using the plasma CVD method, use it as a light-emitting material, and apply it to a pin-type light-emitting element with high luminous efficiency. This is because the amorphous carbon-based material produced has a large optical band gap (hereinafter referred to as Ego) (3 eV or more, the gap does not change up to 250'C in terms of heat resistance).
In addition, arbitrary optical energy gaps and emission characteristics can be obtained by controlling film forming conditions. In addition, strong photoluminescence (PL) is observed in this film depending on the size of Ego, so by selecting various Ego, colors from red to blue can be emitted from the tuner pull. This is because it is a light-emitting material that can be used in flat panel displays and other applications due to its large surface area that takes advantage of its characteristics.

D1 Problems to be Solved by the Invention However, when attempting to use such a material in a PTN semiconductor layer, which is an electron/hole injection layer of a PIN light emitting device, the target characteristics of Eg > 2° (leV, Since it is difficult to create a film with the characteristic of ρ (resistivity) ≦10'Ω・cm, we created a pin-type light emitting device using an amorphous silicon carbide film as the injection layer and confirmed visible electroluminescence. However, for E go, the i layer (
The resistivity of the light emitting layer) is still high, and the p and n layers (injection layers)
Due to insufficient bonding properties with the LED, the luminescence intensity in the blue region, where human visibility is low, is still insufficient, and device characteristics vary, which is an obstacle to commercialization.

81 Means for Solving the Problems Therefore, 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. A plasma chemical vapor deposition method is performed in which a low-pressure reactive gas containing a p-type impurity gas is caused to glow discharge in a vacuum container and the decomposed gas is polymerized, thereby creating a hole injection layer made of a p-type amorphous silicon carbide film. By investigating the relationship between film thickness and thin film properties in advance for the thin film obtained using a mixed gas of one type of hydrocarbon gas and hydrogen gas, the thin film can be adjusted depending on the film thickness. In addition to determining the critical film thickness at which the characteristics of A mixture of other types of highly efficient hydrocarbon gases A mixed gas of hydrocarbon gas and hydrogen gas was introduced into a vacuum container to start film formation, and then the volume ratio of hydrocarbon gas to hydrogen gas was fixed. a step of producing a light-emitting layer made of a hydrogenated amorphous carbon superlattice film by reducing the amount of introduced hydrocarbon gas of the above-mentioned type so that it becomes zero after or near the elapse of the time T0; and carbonization. A plasma chemical vapor deposition method is performed in which a low-pressure reaction gas containing hydrogen gas, silicon hydride gas, and n-type impurity gas is glow-discharged in a vacuum container to polymerize the decomposed gas, thereby forming an n-type amorphous silicon carbide film. The method for solving this problem consists of a step of generating an electron injection layer consisting of:

F8 action p type a-SiC/i type a-C: H/n type a-8iC p
In an in-type light emitting device, the i layer produced by plasma CVD has a superlattice structure, and is an amorphous superlattice well layer composed of, for example, a barrier layer made of CH4-based a-C:H and a well layer made of CtHh-based. By mixing nitrogen gas into the C, H, system a-C:H, N film, the PL-EL intensity increases.

Furthermore, if a computer control method is used to control the initial power in superlattice film fabrication, p/i.

The junction and interface between i/n and barrier layer/well layer are improved. This makes it possible to prevent variations in characteristics between devices.

G. Examples Hereinafter, details of the method for manufacturing a light emitting device according to the present invention will be explained based on examples shown in the drawings.

FIG. 1 is a block diagram showing an example of a light emitting device manufactured by the method according to the present invention. For example, 1 in Figure 1 is 63 cm.
2 is a transparent electrode made of tin oxide, 3 is a p-type amorphous silicon carbide film doped with B 3- and having a thickness of about 30 nm (hereinafter referred to as RA-9I).
It is called "C membrane". ), 4 is 300 n
a light-emitting layer made of an amorphous carbon-based film (hereinafter referred to as ra-C:H film or a-C:H,N film) with a thickness of m;
5 is an electron injection layer made of an n-type a-SiC film doped with P5° and has a thickness of about 50 nm, and 6 is an aluminum electrode.

Next, a method for manufacturing such a light emitting device will be explained with reference to FIG. In the figure, 7 is a vacuum container, which is divided into three consecutive vacuum chambers 7I to 73. First, C
A reaction gas obtained by diluting a mixed gas of H4, SiH4, and BtHe about 10 times with H, gas is added to the first vacuum chamber 7I.
At the same time, a high frequency voltage is applied to this gas by a high frequency power source E1, and the decomposed gas generated by glow discharge is polymerized on the substrate 8, thereby obtaining a p-type a-SiC film.

That is, this a-9iC film was produced by plasma CVD (Chemi-CVD).
cal vapor deposition) method. Continued 11. Vacuum chamber 7. After evacuating, without breaking the vacuum state (the substrate 8 on which the a-SiC film is formed is transferred to the second vacuum chamber 7., hydrocarbon gas and Hz gas are introduced into it, and a high frequency power source E is turned on.

A high frequency voltage was applied to form the a-8i light emitting layer according to the following invention by plasma CVD method.
A layer is formed on the C film. Next, vacuum chamber 7. After evacuating, the substrate 8 on which these films were formed was transferred to the third vacuum chamber 7 without breaking the vacuum state, and the same vacuum was used as in the first vacuum except that PH gas was used instead of B, H, and gases. An n-type a-3iC film is obtained in the same manner as the method applied in chamber 71, and then a pi-3iC film is formed by forming an electrode film on this λSiC film.
An n-type light emitting element is obtained. Note that 91 to 9 in Figure 2. 1 is a susceptor rotatably provided by a magnetic seal;
0,11.12 is the heater, E.

Et and E3 are high frequency power supplies.

Here, the manufacturing conditions for the p, n semiconductor layers when manufacturing a light emitting device using the apparatus shown in FIG. 2 are listed below.

Gas pressure inside the hole injection layer vacuum container: 66.7 Pa (0.5 Torr)
Substrate temperature 200℃ CL gas: 5IH4 gas l: IB, HJ: (
CHJsu÷5i11. 'Jj Su) 3:1000 High frequency power supply power 40W (O,13W/am'' for the area of the manual electrode)b*Gas pressure in the empty container of the electron injection layer 66.7Pa (0.5Torr)
Substrate temperature 200℃ CH, gas: 5IH4 gas l: IPHJ gas: (
CH4j+5illJ) 5.8:1000 High frequency power supply power 40W (O, 13Y/c++1 for input electrode area) Next, the light emitting layer will be described.

Conventionally, hydrocarbon gas and Ht gas were stored in the vacuum chamber 7 in Figure 2.
．． The a-C:H film was converted into p-type a-8 by plasma CVD method by applying a high-frequency source using a high-frequency power source E.
It was laminated on the iC:H film to serve as a light emitting layer. In addition, the hydrogen dilution of hydrocarbon gas is 50%.

Substrate temperature 200℃, chamber pressure 13.3Pa (0.1T
o r r), CH, C, H as hydrocarbon gas under the basic conditions of 18 W of human power and 2 cm distance between electrodes.

When using C1)(
In the 4th system, the PL peak energy changed as shown in FIG. 4 with respect to the optical gap Ego. As you can see from the figure, E g
o is larger in the CH4 system than in the C, H, system, and conversely, the PL intensity is stronger in the Cx H- system, and when compared with the same E g o, the resistivity is higher in the CH, system than in the C, H, system. It is known that it is about 1 to 0.5 orders of magnitude smaller (in Ωcm units). Therefore, in order to improve the conventional problems, the single light-emitting layer was made to have an amorphous superlattice structure. Based on the above facts, the superlattice structure is based on the Ct H- system a-C:H,N which exhibits strong PL in the well layer which is the recombination part of electrons and holes.
CH film with low resistivity and λ-C system are used for the barrier layer.
:H film was used. In addition, in order to increase the injection efficiency of holes from the p layer and electrons from the n layer, the i of the p/i and i/n junctions is
The barrier layer was prepared as the layer.

Each barrier and well layer is formed using the method described later so that the inside of the barrier and well layers of the superlattice becomes a uniform film, and the resistance of the film of about ION nm used in the superlattice is the same as that of a film with a thickness of 200 nm or more. The team corrected the instability of the film properties caused by the initial plasma, and created a steep interface to achieve good bonding, which was common in conventional superlattice films. The steepness and flatness of the interface were confirmed by X-ray diffraction as shown in FIG.

By using this film manufacturing method, it became possible to obtain good bonding properties between the p-layer, n-layer, and i-layer, improving the injection efficiency of electrons and holes, and reducing variations in characteristics between devices. Next, the manufacturing procedure of the superlattice film will be described. Film formation is a so-called step-by-step method. In FIG. 2, a substrate on which a p-type a-9iC film is formed is placed in a vacuum chamber 7.
．． After moving CH, gas, H, gas into this tank and applying computer-controlled high-frequency power using high-frequency power source E to form a barrier layer, the high-frequency power source was stopped and the inside of the tank was After evacuating again, C,H.

Gas, hydrogen gas, and nitrogen gas are introduced, and computer-controlled high-frequency power is applied again to form a well layer. Thereafter, the inside of the tank is evacuated, a barrier layer is formed by the same procedure, and a superlattice film forming a light emitting layer is produced by repeating this procedure. In order to control the atomic layer of the superlattice film, the film formation rate is CH.

Both C, H, and systems were set to 0.2 nm/see or less (CH4
is half the film forming speed of Ct H4). As an example of film forming conditions, barrier layer vacuum chamber gas pressure 13.3 Pa (0, ITo
rr) Substrate temperature 200℃ CH, :H, 1:1 High frequency power 15W Well layer Gas pressure in vacuum chamber 13.3Pa (0.1 Tor
r) Substrate temperature 200°C C, H,: H, 1:1.2 High frequency power 251 N, gas concentration 0% Under these conditions, the barrier layer has a voltage of 3.2 eV and the well layer has a voltage of 25 eV.
A film of E g o of V is obtained. EgQ of the barrier and well layer that determines the luminescent color can be changed by various combinations of film forming conditions.
Although a value of OeV or less can be easily obtained, when used as a light emitting element, the emission intensity at room temperature decreases significantly when the substrate temperature is raised to 300° C. or higher, so 300° C. is the limit.

The Ega and PL peak energies of the light emitting layer when the light emitting layer is constructed under the above conditions, the barrier layer is constant at 5 nm, and the thickness of the well layer is changed as shown in Figure 6, and the same EL (electric field When comparing a conventional light-emitting element having a peak position with a light-emitting element using a superlattice, an increase in peak intensity was observed, and as shown in FIG. 7, a decrease in half-width was observed.

If the thickness of the barrier and well layers is 400 nm or more, the resistance will increase, and in order to obtain strong light emission, the superlattice structure must have a period of 1O or more, and the quantum effect will be sufficient. From the necessity and Figure 4,
The thickness of the barrier layer needs to be about 5 to 20 nm, and the thickness of the well layer needs to be about 1 to 10 nm.

Next, when forming the well layer by mixing nitrogen gas under the above conditions, the PL peak intensity and the EL (electroluminescence) pealing intensity changed with respect to the nitrogen concentration as shown in FIG. In the diagram! ,. , IEO is the intensity when the nitrogen concentration is 0%. It is clear from the figure that the PL and EL intensities are improved by adding nitrogen, and the concentration is preferably 0.05 to 20%.

Although the embodiments have been described above, various design changes can be made to the present invention depending on the gist of the configuration.

H. Effects of the Invention As is clear from the above explanation, according to the method for manufacturing a light emitting device according to the present invention, the PL and EL intensities can be increased.

Furthermore, it has the effect of improving the emission intensity in the blue region and reducing the half-width of the emission spectrum due to quantum effects.

Furthermore, the present invention has the effect of improving bonding properties at the film interface and has the effect of reducing variations between devices.

In addition, i at the junction between the p layer and the i layer and between the i layer and the n layer
There is an efficiency in improving injection efficiency by creating a barrier layer in the layer.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a light emitting device manufactured by the method for producing a light emitting device according to the present invention, Fig. 2 is a block diagram showing a light emitting device manufacturing apparatus, and Fig. 3 is a block diagram showing a light emitting device manufacturing method according to the present invention. Graph showing the relationship between intensity and Figure 4 is a graph showing the relationship between E g o and PL peak energy. Figure 5 is a graph showing X-ray diffraction. Figure 6 is when the thickness of the well layer is changed. Figure 7 is a graph showing the relationship between the Ego and PL peak energies of the light-emitting layer. Figure 7 is a graph comparing the peaks of a conventional light-emitting element and a light-emitting element using a superlattice, which have the same EL peak position. It is a graph showing changes in PL peak intensity and EL peak intensity with respect to nitrogen concentration. DESCRIPTION OF SYMBOLS 1... Substrate, 2.6... Electrode, 3... Hole injection layer, 4... Light emitting layer, 5... Electron injection layer, 7... Vacuum container, 7-7. ... Vacuum chamber, 8... Substrate, 9. ~9
3...Susceptor. Outside Z? 5. Fig. 1. Block diagram of the embodiment. Fig. 2. Block diagram of the manufacturing apparatus. C,H. Gas species Fig. 4Eg. (eV) 1.5 2.0 2.5 3.0

Claims (2)

[Claims] (1) In 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, a low pressure reactive gas containing a hydrocarbon gas, a silicon hydride gas and a p-type impurity gas is used. A plasma chemical vapor deposition method is performed in which the decomposed gas is polymerized by glow discharge in a vacuum container, thereby producing a hole injection layer made of a p-type amorphous silicon carbide film, and one type of hydrocarbon gas. For the thin film obtained using a gas mixture with hydrogen gas, by investigating in advance the relationship between the film thickness and the properties of the thin film, we can determine the critical film thickness at which the properties of the thin film do not change depending on the size of the film thickness, and also The time T_0 from the start of the film until the film thickness reaches the critical film thickness is determined, and the mixed carbonization of the one type of hydrocarbon gas and another type of hydrocarbon gas with higher decomposition efficiency than the hydrocarbon gas is performed. A mixed gas of hydrogen gas and hydrogen gas is introduced into a vacuum container to start film formation, and then, while the volume ratio of hydrocarbon gas and hydrogen gas is fixed, the amount of the other type of hydrocarbon gas introduced is is reduced to zero after or around the time T_0 to produce a light-emitting layer made of a hydrogenated amorphous carbon superlattice film; a hydrocarbon gas, a silicon hydride gas, and an n-type impurity gas; A process of performing a plasma chemical vapor deposition method in which a low-pressure reactive gas containing a gas is caused to glow discharge in a vacuum container to polymerize the decomposed gas, thereby producing an electron injection layer made of an n-type amorphous silicon carbide film. A method for manufacturing a light emitting device, characterized by: (2) The method for manufacturing a light emitting device according to claim 1, wherein the well layer in the light emitting layer is produced using a plasma chemical vapor deposition method in which nitrogen gas is mixed.