JP3383242B2 - Gallium nitride based compound semiconductor light emitting device - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates to relates to the blue light-emitting gallium nitride-based compound semiconductor light-emitting element.

[0002]

2. Description of the Related Art Conventionally, GaN has been used as a blue light emitting diode.
There are known ones using a system compound semiconductor. That Ga
N-based compound semiconductors are attracting attention because of their direct emission, high emission efficiency, and blue, which is one of the three primary colors of light, as the emission color.

In such a light emitting diode using a GaN-based compound semiconductor, an n layer made of an n-conductivity type GaN-based compound semiconductor is grown directly on a sapphire substrate or with a buffer layer made of aluminum nitride interposed. Then, a p-type impurity is added to the n-layer to grow an i-layer made of an i-type GaN-based compound semiconductor (JP-A-62-119196, JP-A-63-196196). -188977 publication).

[0004]

However, the light emission intensity of the light emitting diode having the above structure is not yet sufficient. Also, pn
Since it is not a junction, the drive voltage may vary and become high. These improvements are desired.

Therefore, an object of the present invention is to improve the blue light emission intensity of a GaN compound semiconductor light emitting diode and to stabilize the driving voltage.

[0006]

Configuration of the present invention, in order to solve the problem] is the gallium nitride-based compound semiconductor light-emitting element, gallium nitride
Addition of silicon (Si) to compound semiconductor light emitting device
And the electron concentration of the n-type ^{1 × 10 17 ~1 × 10 19} / cm 3 and
A high carrier concentration layer composed of Al _X Ga _1-X N (including X = 0),
N-type Al _X G with an electron concentration of 1 × 10 ¹⁴ to 1 × 10 ¹⁷ / cm ³
a _1-X N (including X = 0) low carrier concentration layer and p-type
And a p-layer consisting of Al _X Ga _1-X N (including X = 0)
A gallium nitride-based compound semiconductor light-emitting device characterized by
It

Another structure of the present invention is based on gallium nitride.
In compound semiconductor light emitting device, by adding silicon (Si)
N-type Al _X G with electron concentration of 1 × 10 ¹⁷ to 1 × 10 ¹⁹ / cm ³
a _1-X N (including X = 0) high carrier concentration layer
A low-capacity array of doped n-type Al _X Ga _1-X N ( including X = 0).
Consists of a rear concentration layer and p-type Al _X Ga _1-X N (including X = 0)
a gallium nitride-based compound having a p-layer
It is a semiconductor light emitting device. The structure of another invention is a nitride gas.
In a lithium compound semiconductor light emitting device, silicon (Si)
High-quality N _- type Al _X Ga _1-X N (including X = 0)
Carrier concentration layer and electron concentration of 1 × 10 ¹⁴ to 1 × 10 ¹⁷ /
Low carry of cm ³ n-type Al _X Ga _1-X N (including X = 0)
P consisting of a concentration layer and p-type Al _X Ga _1-X N (including X = 0)
And a gallium nitride-based compound semi-comprising
It is a conductor light emitting element.

[0008]

According to the present invention, the p-layer and the n-layer can be joined instead of the conventional i-layer and the n-layer.
As a result, the amount of injected carriers was increased, and the light emission efficiency and the light emission brightness could be improved.

Due to the high carrier concentration layer, the electrical resistance of the entire n layer is
The resistance can be reduced, the series resistance of the light emitting diode is reduced,
It is possible to suppress heat generation of the light emitting diode. And
With the above configuration, the emission intensity of the light emitting diode
Can be increased. In addition, the low carrier concentration layer and high
By providing a carrier concentration layer, the light emitting diode blue
The emission intensity of the color can be increased.

[0010]

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below based on specific embodiments.

In FIG. 1, a light emitting diode 10 has a sapphire substrate 1, and
A buffer layer 2 of 500 Å AlN is formed. On the buffer layer 2, a high carrier concentration n ⁺ layer 3 made of GaN having a film thickness of about 2.2 μm and a low carrier concentration n layer 4 made of GaN having a film thickness of about 1.5 μm are sequentially formed. , A low carrier concentration n layer 4 having a thickness of about 0.2 μm GaN p
Layer 5 has been formed. The electrode 7 formed of aluminum and connected to the p layer 5 and the high carrier concentration n ⁺ layer 3 are formed.
And an electrode 8 made of aluminum and connected to.

Next, a method of manufacturing the light emitting diode 10 having this structure will be described.

The light emitting diode 10 was manufactured by vapor phase epitaxy by an organometallic compound vapor phase epitaxy method (hereinafter referred to as "M0VPE").

The gases used are NH ₃ and carrier gas H ₂
Trimethyl gallium _{(Ga (CH 3) 3)} ( hereinafter referred to as "TMG") and trimethylaluminum _{(Al (CH 3) 3)} ( hereinafter "TMA
)), Silane (SiH ₄ ), and cyclopentadienyl magnesium (Mg (C ₅ H ₅ ) ₂ ) (hereinafter referred to as “CP ₂ Mg”).

First, the single crystal sapphire substrate 1 whose main surface is the a-plane cleaned by organic cleaning and heat treatment is mounted on the susceptor placed in the reaction chamber of the M0VPE apparatus. Then, at a pressure of 1100 while flowing H ₂ into the reaction chamber at a flow rate of 2 liter / min under normal pressure.
The sapphire substrate 1 was vapor-phase etched at 0 ° C.

Next, the temperature is lowered to 400 ° C. and H ₂ is added.
20 liter / min, NH ₃ 10 liter / min, TMA 1.8 × 10 ^-5
The buffer layer 2 of AlN was formed at a thickness of about 500Å by supplying at a mol / min.

Next, the temperature of the sapphire substrate 1 was maintained at 1150 ° C., H ₂ was 20 liter / min, NH ₃ was 10 liter / min, and TMG was used.
Silane (SiH ₄ ) diluted to 1.7 × 10 ^-4 mol / min and 0.86 ppm with H ₂ at a rate of 200 ml / min for 30 minutes to obtain a film thickness of about 2.
2 [mu] m, thereby forming a high carrier concentration n ⁺ layer 3 made of GaN having a carrier concentration 1.5 × 10 ¹⁸ / cm ^3.

Then, the temperature of the sapphire substrate 1 is set to 1150 ° C.
, H ₂ at 20 liter / min, NH ₃ at 10 liter / min, TMG
For 20 minutes at a rate of 1.7 × 10 ^-4 mol / min,
A low carrier concentration n-layer 4 made of GaN having a carrier concentration of 1 × 10 ¹⁵ / cm ^{3 and} a thickness of 1.5 μm was formed.

Next, the sapphire substrate 1 is set to 900 ° C.,
H ₂ = 20 liter / min, NH ₃ = 10 liter / min, TMG = 1.7
× 10 ^-4 mol / min, CP ₂ Mg at 3 × 10 ^-6 mol / min 3
Then, the i-layer 5 made of GaN having a film thickness of 0.2 μm was formed by supplying for 10 minutes. In this state, the i layer 5 is an insulator.

Next, the i layer 5 was uniformly irradiated with an electron beam by using a reflection electron beam diffraction apparatus. Electron beam irradiation conditions are: acceleration voltage 10 KV, sample current 1 μA, beam moving speed
0.2 mm / sec, beam diameter 60 μmφ, vacuum degree 2.1 × 10 ⁻⁵ Torr. This electron beam irradiation causes the i-layer 5 to have a resistivity of 10 ⁸
An insulator of Ωcm or more became a p-conductivity type semiconductor with a resistivity of 40 Ωcm. In this way, the p layer 5 exhibiting the p conductivity type is obtained.

In this way, a wafer having a multilayer structure as shown in FIG. 2 was obtained.

FIGS. 3 to 7 and 9 to 12 described below are cross-sectional views showing only one element on the wafer. In practice, a wafer in which this element is continuously repeated is processed. After that, it is cut into each element.

As shown in FIG. 3, a SiO ₂ layer 11 having a thickness of 2000 Å was formed on the p layer 5 by sputtering.
Next, a photoresist 12 is applied on the SiO ₂ layer 11, and the photoresist 12 is applied by photolithography.
Was formed in a pattern in which the photoresist was removed from the electrode forming portion A for the high carrier concentration n ⁺ layer 3 and the portion B forming a groove for insulating the electrode forming portion from the electrode for the p layer 5. Next, as shown in FIG.
The SiO ₂ layer 11 not covered with 2 was removed with a hydrofluoric acid-based etching solution.

Next, as shown in FIG. 5, the p layer 5 in a portion not covered by the photoresist 12 and the SiO ₂ layer 11, the low carrier concentration n layer 4 and the high carrier concentration n under the p layer 5 are formed.
⁺ Vacuum level 0.04 Torr, high frequency power 0.44
W / cm ² and CCl ₂ F ₂ gas were supplied at a rate of 10 ml / min for dry etching, and then Ar was used for dry etching.

Next, as shown in FIG. 6, the SiO ₂ layer 11 remaining on the p layer 5 was removed with hydrofluoric acid.

Next, as shown in FIG. 7, an Al layer 13 was formed on the entire surface of the sample by vapor deposition. Then, a photoresist 14 is applied on the Al layer 13, and the photoresist 14 is patterned into a predetermined shape by photolithography so that the electrode portions for the high carrier concentration n ⁺ layer 3 and the p layer 5 remain. did.

Next, as shown in FIG. 7, the exposed portion of the lower Al layer 13 is etched with a nitric acid-based etching solution using the photoresist 14 as a mask, and the photoresist 14 is removed with acetone to obtain a high carrier concentration n ^+. Electrode 3 of layer 3, p
The electrode 7 of the layer 5 was formed.

Thereafter, the wafer processed as described above is
Each element was cut to obtain a pn-structure gallium nitride-based light-emitting element shown in FIG.

The light emission intensity of the light emitting diode 10 thus manufactured was measured and found to be 10 mcd. This is simply the i-layer and carrier concentration 5 × 10 ¹⁷ / cm ³ , thickness 4
The light emission intensity is 10 times higher than that of a conventional light emitting diode connected to a μm n layer.

Furthermore, the driving voltage (1
(0mA) varied from 10 to 15V, but the driving voltage was reduced to about 7V due to the introduction of the p layer, and the variation was reduced.

When the light emitting surface was observed, it was also observed that the number of light emitting points increased.

For comparison, the low carrier concentration n layer 4 is used.
We manufactured the above samples with various carrier concentrations of
The emission intensity and emission spectrum were measured. The result is shown in FIG.

It can be seen that the emission intensity decreases and the emission wavelength shifts to the red side as the carrier concentration increases. This is considered to be because the doping element silicon diffuses or mixes into the p layer 5 as an impurity element.

The light emitting diode 10 can also be manufactured as follows.

The layers are laminated as shown in FIG. 2 in the same manner as described above. However, instead of the p layer 5, the i layer 5
0 (FIG. 9) are stacked. That is, the i layer 50 is not irradiated with the electron beam. Therefore, in this stacked state, i
The layer 50 is an insulator (i type).

Then, in this laminated wafer, as shown in FIG. 9, a groove was formed by etching only in the electrode forming portion A for the high carrier concentration n ⁺ layer 3.

Next, as shown in FIG. 10, only a part of the i layer 50 is irradiated with an electron beam to form the p layer 5 of p conductivity type semiconductor.
Was formed. At this time, the portion other than the p layer 5, that is, the portion not irradiated with the electron beam remains the i layer 50 of the insulator. Therefore, the p layer 5 forms a pn junction with the low carrier concentration n layer 4 in the vertical direction, but in the horizontal direction,
The p layer 5 is electrically isolated from the surroundings by the i layer 50.

Next, as shown in FIG. 11, an electrode forming portion A for the p layer 5, the i layer 50 and the high carrier concentration n ⁺ layer 3 is formed.
An Al layer 20 was formed on the entire upper surface by vapor deposition. Then, a photoresist 21 is applied on the Al layer 20, and the photoresist 21 is applied by photolithography.
Was patterned into a predetermined shape so that the electrode portions for the high carrier concentration n ⁺ layer 3 and p layer 5 remain.

Next, using the photoresist 21 as a mask, the exposed portion of the lower Al layer 20 is etched with a nitric acid-based etching solution, and the photoresist 21 is removed with acetone.
As shown in FIG. 12, the electrode 5 of the high carrier concentration n ⁺ layer 3 is formed.
2, the electrode 51 of the p layer 5 was formed.

After that, the wafer formed as described above was cut into each element.

The doping gas of magnesium Mg is
In addition to the above gases, methylcyclopentadienyl magnesium Mg ((C ₅ H ₅ ) CH ₃ ) ₂ may be used.

Further, in the above embodiment, the doping element of the p layer is magnesium (Mg). When Mg is simply doped, it becomes i-type (insulating). By irradiating the i-type layer with an electron beam, it can be changed to the p-conductivity type. The electron beam irradiation conditions include an acceleration voltage of 1 KV to 50 KV,
A sample current of 0.1 μA to 1 mA is desirable.

The carrier concentration of the low carrier concentration n layer is preferably 1 × 10 ¹⁴ to 1 × 10 ¹⁷ / cm ³ and the film thickness is preferably 0.5 to 2 μm. When the carrier concentration is 1 × 10 ¹⁷ / cm ³ or more, the emission intensity decreases, which is not desirable. When the carrier concentration is 1 × 10 ¹⁴ / cm ³ or less, the series resistance of the light emitting element becomes too high and heat is generated when an electric current is applied. . Further, if the film thickness is 2 μm or more, the series resistance of the light emitting element becomes too high and heat is generated when a current is applied, which is not desirable, and if the film thickness is 0.5 μm or less, the emission intensity decreases, which is not desirable.

Further, the carrier concentration of the high carrier concentration n ⁺ layer is preferably 1 × 10 ¹⁷ to 1 × 10 ¹⁹ / cm ³ and the film thickness is preferably 2 to 10 μm. When the carrier concentration is 1 × 10 ¹⁹ / cm ³ or more, the crystallinity is deteriorated, which is not desirable. When the carrier concentration is 1 × 10 ¹⁷ / cm ³ or less, the series resistance of the light emitting element becomes too high and heat is generated when a current is applied, which is not desirable. . Also, if the film thickness is 10 μm or more, the substrate is curved, which is not desirable, and if the film thickness is 2 μm or less, the series resistance of the light emitting element becomes too high and heat is generated when an electric current is passed, which is not desirable.

In the detailed description of the invention, the following inventions will be described.
Is also recognized. Gallium Nitride Compound Semiconductor Luminescent Element
In semiconductor, gallium nitride compound semiconductor showing p conductivity type
Layer (including Al _X Ga _1-X N; X = 0 ) and the p layer
Low carrier concentration gallium nitride compound semiconductor (A
l _X Ga _1-X N; including X = 0) and a low carrier concentration n layer,
Nitride gas with a high carrier concentration that joins to a low carrier concentration n-layer
Comprised of helium compound semiconductors (including Al _X Ga _1-X N; X = 0)
Forming a high carrier concentration n ⁺ layer and forming a pn junction
With n layer is a double layer of low carrier concentration and high carrier concentration
Structured inventions are recognized.

A buffer layer is formed on the sapphire substrate.
And the high carrier concentration gallium nitride on the buffer layer.
A step of forming a layer made of an um-based compound semiconductor, and
Of a layer made of a gallium nitride-based compound semiconductor with a carrier concentration
From gallium nitride compound semiconductor with low carrier concentration
Forming a layer composed of gallium nitride with a low carrier concentration.
Nitriding showing p-conductivity type on a layer made of a compound semiconductor
Such as forming a layer made of gallium compound semiconductor
Gallium nitride-based compound semiconductor
Methods of manufacturing optical devices have been recognized.

In the structure of the above invention, a p layer and an n layer are formed.
Since it has become possible to bond the
However, the luminous efficiency and the luminous brightness could be improved.
In addition, in order from the side where the n layer is joined to the p layer, the low carrier concentration
Double layer structure of n layer and high carrier concentration n ⁺ layer
To increase the blue emission intensity of the light emitting diode
I was able to.

In other words, the high carrier concentration n ⁺ layer enables the entire n layers to be
The electrical resistance of the body can be reduced and the series resistance of the light emitting diode
Can reduce the heat generation of the light emitting diode
It Also, the n layer joined to the p layer should have a low carrier concentration.
That is, GaN is highly purified to emit light in the light emitting region (p layer and its
Suppressing the concentration of impurity atoms that deteriorate blue light emission in the vicinity
be able to. In addition, the n layer joined to the p layer has a crystal strain.
Can be few. Due to the above action, blue
The emission intensity of was improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a configuration of a light emitting diode according to a specific embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a manufacturing process of the light emitting diode of the same embodiment.

FIG. 3 is a cross-sectional view showing a manufacturing process of the light emitting diode of the embodiment.

FIG. 4 is a cross-sectional view showing a manufacturing process of the light emitting diode of the same embodiment.

FIG. 5 is a cross-sectional view showing the manufacturing process of the light emitting diode of the same embodiment.

FIG. 6 is a cross-sectional view showing a manufacturing process of the light emitting diode of the embodiment.

FIG. 7 is a sectional view showing a manufacturing process of the light emitting diode of the embodiment.

FIG. 8 is a measurement diagram showing the relationship between the carrier concentration of a low carrier concentration n layer and the emission intensity and emission wavelength.

FIG. 9 is a sectional view showing a manufacturing process of a light emitting diode by another manufacturing method.

FIG. 10 is a cross-sectional view showing a manufacturing process of a light emitting diode by another manufacturing method.

FIG. 11 is a cross-sectional view showing a manufacturing process of a light emitting diode by another manufacturing method.

FIG. 12 is a cross-sectional view showing a manufacturing process of a light emitting diode by another manufacturing method.

[Explanation of symbols]

10-Light-emitting diode 1-Sapphire substrate 2-Buffer layer 3-High carrier concentration n ⁺ layer 4-Low carrier concentration n layer 5-p layer 50-i layer 7, 8, 51, 52-Electrode

─────────────────────────────────────────────────── ─── Continuation of the front page (73) Patent holder 396020800 Science and Technology Promotion Corporation 4-8 Hommachi, Kawaguchi City, Saitama Prefecture (72) Inventor Katsuhide Sanbe Ochiai, Nagahata, Kasuga-cho, Nishikasugai-gun, Aichi Prefecture In Toyoda Gosei Co., Ltd. (72) Inventor Sasa Dosei, Nagachi 1 Ochiai, Kasuga-cho, Nishi-Kasugai-gun, Aichi Prefecture In-house Toyoda Gosei Co., Ltd. (72) Kuki Kato 1 Ochiai, Nagahata, Kasuga-cho, Nishikasui-gun, Aichi Toyoda Gosei Incorporated (72) Inventor Shiro Yamazaki 1 Ochiai, Nagahata, Kasuga-cho, Nishikasugai-gun, Aichi Prefecture Toyota Gosei Co., Ltd. (72) Inventor, Masafumi Hashimoto, Aichi-gun, Aichi-gun, Nagakute-cho 41, Nagamage Yokomichi 1 Toyota Central Research Institute (72) Inventor Yu Akasaki Furomachi, Chikusa-ku, Nagoya-shi, Aichi (No house number) Nagoya Univ. The inner (56) Reference Patent Sho 59-228776 (JP, A) JP Akira 53-47284 (JP, A) JP Akira 48-22291 (JP, A) Japanese Journal of Applied Physic s, Vol. 28, No. 12, December, 1989, pp. L2112-L2114 (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 33/00

Claims (3)

(57) [Claims] 1. A gallium nitride-based compound semiconductor light emitting device
Then, silicon (Si) is added to make the electron concentration 1 × 10 ¹⁷ to 1 × 1.
0 ¹⁹ / cm ³ n-type Al _X Ga _1-X N (including X = 0) high
Carrier concentration layer and n-type Al _X G with electron concentration of 1 × 10 ¹⁴ to 1 × 10 ¹⁷ / cm ^3.
Nitride having a low carrier concentration layer made of a _1-X N (including X = 0) and a p- layer made of p-type Al _X Ga _1-X N (including X = 0) Gallium compound semiconductor light emitting device. 2. A gallium nitride-based compound semiconductor light emitting device
Then, silicon (Si) is added to make the electron concentration 1 × 10 ¹⁷ to 1 × 1.
0 ¹⁹ / cm ³ n-type Al _X Ga _1-X N (including X = 0) high
Low carrier concentration layer and non-doped n-type Al _X Ga _1-X N (including X = 0)
A gallium nitride-based compound semiconductor light-emitting device having a carrier concentration layer and a p- layer made of p-type Al _X Ga _1-X N (including X = 0) . 3. A gallium nitride-based compound semiconductor light emitting device
And n-type Al _X Ga _1-X N (including X = 0 ) added with silicon (Si )
And a high carrier concentration layer composed of n-type Al _X G with an electron concentration of 1 × 10 ¹⁴ to 1 × 10 ¹⁷ / cm ^3.
Nitride having a low carrier concentration layer made of a _1-X N (including X = 0) and a p- layer made of p-type Al _X Ga _1-X N (including X = 0) Gallium compound semiconductor light emitting device.