JPH08167736A - Blue light emitting device and manufacturing method thereof - Google Patents

Abstract

(57) [Summary] [Object] To provide a blue light emitting device in which deterioration of characteristics over time is suppressed, and an efficient manufacturing method thereof. In a blue light emitting diode device having a PIN diode structure, i-type a-SiC: H which is an active layer is formed.
The thin film (hydrogenated amorphous SiC thin film) 4 contains 1 to 50 atomic% of N. By containing N, uniform dispersion of Si atoms and C atoms in the film is promoted, and blue light emission is realized even in an amorphous film. Furthermore, since at least a part of the dangling bond is terminated by the N atom, the recombination center disappears and the light emission efficiency is improved. Since the N atom is stable in the film, the moisture resistance of the PIN diode is improved and the life is extended.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blue light emitting device using a semiconductor and a method of manufacturing the same, and more particularly to a blue light emitting device with suppressed deterioration of characteristics over time and an efficient method of manufacturing the same.

[0002]

In the field of optoelectronics,
There is a strong demand for shorter wavelength semiconductor light emitting devices such as light emitting diodes and laser diodes. There are two reasons behind the desire for shorter wavelengths. One is that short-wavelength light has a larger energy of one photon than long-wavelength light, and another is that if the numerical aperture of the lens is the same, the shorter the wavelength, the better the light-collecting property. The former increases the degree of freedom in selecting a photoconductor used in, for example, a laser printer, and contributes to speeding up printing. On the other hand, the latter contributes to a dramatic increase in the storage capacity of optical memories such as compact discs and magneto-optical discs. Further, if a blue light emitting diode is developed in addition to the red light emitting diode and the green light emitting diode which are currently on the market, it is possible to realize a large area full color display and a traffic signal light with low power consumption and long life.

The emission wavelength of a semiconductor light emitting device is basically determined by the band gap. Band gap E
The wavelength λ (n of photons with energy equal to _g (eV)
m) is represented by λ = 1240 / E _g , and it is necessary to select a semiconductor having a large band gap in order to obtain light emission with a shorter wavelength. For example, to obtain blue light at 460 nm, a semiconductor with a band gap of about 2.7 eV is needed. Conventionally, as a semiconductor capable of emitting blue light, I
GaN which is a II-V group compound semiconductor, ZnSe and ZnS which are II-IV group compound semiconductors, and SiC which is an IV-IV group compound semiconductor have been studied. However, Ga
Regarding N, ZnSe, and ZnS, although high brightness derived from the direct transition type energy band structure is expected, there is no bulk single crystal substrate for forming a good crystalline thin film, and therefore, another substrate is used. I have no choice but to substitute
As a result, crystal defects due to substrate stress are generated, which causes light emission to be disturbed. In addition, since it is generally difficult to obtain a p-type semiconductor required for forming a pn junction, M having a low luminous efficiency in spite of requiring a high voltage.
There is a problem that the IS type (junction of metal-insulating layer-n type semiconductor layer) structure has to be taken. On the other hand, Si
Although C is slightly inferior in brightness because it has an indirect transition type energy band structure, it is possible to use a bulk single crystal substrate made of the same material, and it is possible to easily convert it to p-type to obtain p-type.
Since the n-junction can be realized, it has been put to practical use from a relatively early stage.

[0004]

In the meantime, regarding the SiC-based semiconductor light emitting device, it has been considered to use an amorphous thin film as an active layer, which has relatively few restrictions on the substrate to be used. The 29th Joint Lecture Meeting on Applied Physics (1982 Spring Annual Meeting) Lecture Proceedings 3a-Z-8 uses white hydrogenated amorphous SiC (hereinafter abbreviated as a-SiC: H) thin film. There is a statement that luminescence was obtained. However, only white light emission was observed here because three-coordinate atoms and four-coordinate atoms were present in the film because the Si and C atoms in a-SiC: H were not uniformly dispersed. As a result, fluctuations in the bond angle and interatomic distance occur, and levels called tail states are formed near the energy band edge, which shifts the emission wavelength to the long wavelength side and expands the half width (whitening). ) Has occurred. Further, the emission was low in brightness because the a-SiC: H thin film did not have a high-density network structure because a large amount of linear or graphite-like C-atom bonds were present in the thin film. The reason for this is that a large number of fine voids are contained therein, and the dangling bonds existing around the voids act as non-radiative recombination centers, so that the luminous efficiency is reduced.

In order to solve this problem, Japanese Unexamined Patent Publication (Kokai) 5-2
Japanese Patent No. 9652 discloses a blue light emitting device using an a-SiC: H thin film having a fluorine concentration in the range of 5 to 50 atomic% as an active layer. This is because the introduction of F atoms promotes the uniform dispersion of Si atoms and C atoms to form a random network to shorten the emission wavelength, and the dangling bond is terminated by F atoms to recombine. By eliminating the center, the luminous efficiency is improved. However, such a film containing a large amount of fluorine produces HF due to moisture absorption, and there is a high possibility that the film quality deteriorates with time and the deterioration of the light emitting element with time due to the deterioration.

Therefore, an object of the present invention is to provide a blue light emitting device in which such deterioration of characteristics over time is suppressed, and an efficient manufacturing method thereof.

[0007]

The present invention is proposed to achieve the above objects.

That is, the blue light emitting element of the present invention has
An a-SiC: H thin film containing 50 atomic% of nitrogen is used as a light emitting layer.

In the method for manufacturing a blue light emitting device of the present invention, plasma CVD is performed using a source gas containing a silane-based gas, a hydrocarbon-based gas and a nitrogen-based gas,
The light emitting layer is formed of a nitrogen-containing a-SiC: H thin film. Here, the silane-based gas is, for example, silane (SiH ₄ ) or disilane (Si ₂ H ₆ ), and the hydrocarbon gas is methane (CH ₄ ) or methanol (CH ₂ ).
₃ OH), ethane (C ₂ H ₆ ), and as the nitrogen-based gas, nitrogen (N ₂ ) or nitrous oxide (N ₂ O)
Nitric oxide typified by each can be typically used. In either case, it is desirable to use a relatively low molecular weight simple substance or compound that is easily dissociated under plasma discharge conditions.

[0010]

In the blue light emitting device of the present invention, 1 to 50 atomic% of N atoms are introduced into the light emitting layer made of an a-SiC: H thin film to promote uniform dispersion of Si atoms and C atoms in the film. , Blue light emission is possible. In addition, since N atoms are used as the terminating atoms of the dangling bonds to eliminate the recombination centers and improve the luminous efficiency, N atoms are used along with H atoms, so even if a-SiC: H absorbs moisture, it is harmful like HF. Therefore, it is possible to avoid deterioration of the film quality over time and deterioration of the characteristics of the light emitting device over time.

In the production of the blue light emitting device of the present invention, a silane-based gas as a Si supply source, a hydrocarbon-based gas as a C supply source, and a nitrogen-based gas as an N supply source are formed in the step of forming the light emitting layer. Since plasma CVD is used, the film can be formed at a relatively low temperature and under low irradiation damage. At this time, the film quality can be finely controlled by optimizing the control parameters such as the gas flow rate, the substrate heating temperature, and the input power, and a highly reliable light emitting layer that does not deteriorate over time can be formed. In addition, since the impurity gas can be switched instantaneously, it has different conductivity types.
-SiC: H thin films can be laminated one after another, enabling extremely efficient production.

[0012]

EXAMPLES Specific examples of the present invention will be described below.

Example 1 In this example, the structure of a blue light emitting diode element to which the present invention is applied will be described with reference to FIG.

This blue light emitting diode element has a PIN type (p type semiconductor layer / i) layer on a transparent electrode layer 2 on an insulating substrate 1.
A diode of a type (type having a laminated structure of a type (intrinsic) semiconductor layer / n-type semiconductor layer) is formed. This PI
The N diode is formed by laminating a p-type a-SiC: H thin film 3, an i-type (intrinsic) a-SiC: H thin film 4, which is a light emitting layer, and an n-type SiC thin film 5 in this order from the lower layer side.
An n-type electrode 6 made of a known aluminum-based material is deposited on the n-type a-SiC: H thin film 5, and the n-type electrode 6 and the negative electrode lead 8 are connected by a bonding wire 7. . On the other hand, the transparent electrode layer 2 is connected to the positive electrode lead 9 by the bonding wire 7.
These structures are housed in a plastic dome type package 10 and emit light hν in all directions.

The insulating substrate 1 is made of an insulating material such as glass or sapphire. In addition, the transparent electrode layer 2 is
It is made of a transparent conductive material such as ITO (indium tin oxide) or SnO ₂ (tin oxide).

Further, the above-mentioned conductive type SiC thin films 3,
Although all of 4 and 5 are based on a hydrogen-containing a-SiC: H thin film, the i-type a-SiC: H thin film 4, which is a light emitting layer, has a maximum feature of 40 atomic% of N atoms. Is included. Since the ESR (electron spin resonance) signal of this i-type a-SiC: H thin film 4 was almost below the detection limit, there was almost no paramagnetic defect having unpaired electrons in this film, that is, in the film. It was found that the dangling bond of was almost completely terminated by H atoms and N atoms.

The blue light emitting diode element having such a structure exhibits a bright blue light emission of the order of 100 cd / m ² and almost no deterioration of the luminance is observed even after conducting an energization test at a current density of 100 mA / cm ^{2 for} 100 hours. There wasn't.

Example 2 In this example, a method for manufacturing the blue light emitting diode element described in Example 1 will be described.

First, an insulating substrate 1 in which a transparent electrode layer 2 made of ITO was formed in advance to a film thickness of 0.2 μm by a sputtering method was set in a parallel plate type plasma CVD apparatus. This plasma CVD apparatus uses a silane-based gas, a hydrocarbon-based gas, a nitrogen-based gas, and other raw material gases that are basically necessary for forming an a-SiC: H thin film in a CVD chamber evacuated to a high vacuum. -SiC: H is connected to a gas supply system for supplying a dopant gas for introducing p-type or n-type impurities into the thin film, and each gas is individually controlled in flow rate and supply / stop by a mass flow controller and a valve. It is designed to be controlled by.

Here, Si is used as the silane-based gas.
H ₄ , CH ₄ as the hydrocarbon-based gas, and N ₂ as the nitrogen-based gas are used, and as an example, p-type, i
Type and n type a-SiC: H thin films 3, 4 and 5 were formed.

[P-type a-SiC: H thin film 3] SiH ₄ flow rate 50 SCCM CH ₄ flow rate 30 SCCM N ₂ flow rate 25 SCCM B ₂ H ₆ flow rate 0.5 SCCM gas pressure 7 Pa RF power 80 W (2.45 GHz) ) Substrate temperature 100 ° C. Film formation time 8 minutes (film thickness 0.015 μm) [i-type a-SiC: H thin film 4] Except for the following items, the film formation conditions of the p-type a-SiC: H thin film 3 are the same.

SiH ₄ flow rate 50 SCCM CH ₄ flow rate 30 SCCM N ₂ flow rate 25 SCCM Film formation time 90 minutes (film thickness 0.15 μm) [n-type a-SiC: H thin film 5] p-type a except the following items -Same as the film forming conditions for the SiC: H thin film 3.

SiH ₄ flow rate 50 SCCM CH ₄ flow rate 30 SCCM N ₂ flow rate 25 SCCM PH ₃ flow rate 0.5 SCCM film formation time 16 minutes (film thickness 0.03 μm) The p-type a-SiC: H thin film 3 and n type a-S
The impurity concentration of the iC: H thin film 5 is 10 ¹⁹ / cm, respectively.
It was on the order of ³ . The N content of the a-SiC: H thin film was about 40 atom%.

After that, batch patterning of each of the SiC: H thin films 3, 4 and 5 by a known technique, deposition of an Al-based thin film,
Formation of the n-type electrode 6 by patterning the Al-based thin film,
Wire bonding and packaging were performed to complete the blue light emitting diode device.

The present invention has been described above based on the two embodiments, but the present invention is not limited to these embodiments. For example, in the embodiment, i-type a-SiC:
N ₂ was used as a nitrogen-based gas when forming the H thin film 4,
Even when N ₂ O was used at the same flow rate instead of this, a blue light emitting diode element having similarly good characteristics could be manufactured. When N ₂ O is used for plasma CVD, O ^* (oxygen radical) generated from this gas is CH
_Since the excessive deposition of the carbon-based polymer derived from No. ₄ in the chamber was suppressed, the side effect that the maintenance frequency for cleaning the chamber could be reduced was also obtained. In addition, details of the structure of the blue LED, CV
The D condition and the like can be changed as appropriate.

[0026]

As is apparent from the above description, by applying the present invention, it is possible to obtain a blue light emitting device which is suppressed in deterioration of characteristics over time and has a long life and high reliability. Moreover, the manufacturing method is relatively economically limited because of the crystallinity of the substrate, and an amorphous SiC film that can be easily p-typed can be used.
Therefore, the present invention greatly contributes to the progress of optoelectronics by providing a blue light emitting element having high brightness and high reliability.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing one structural example of a blue light emitting diode element to which the present invention is applied.

[Explanation of symbols]

 1 Insulating Substrate 2 Transparent Electrode 3 p-type a-SiC: H Thin Film 4 i-type a-SiC: H Thin Film (Active Layer) 5 n-type a-SiC: H Thin Film 6 n-type Electrode 7 Bonding Wire 8 Negative Lead 9 Positive Electrode Lead 10 dome type package

Claims (2)

[Claims] 1. A blue light emitting device using a hydrogenated amorphous SiC thin film containing 1 to 50 atomic% of nitrogen as a light emitting layer. 2. A blue light-emitting device having a light-emitting layer formed of a nitrogen-containing hydrogenated amorphous SiC thin film by performing plasma CVD using a source gas containing a silane-based gas, a hydrocarbon-based gas, and a nitrogen-based gas. Production method.