JP2003332619A - Semiconductor light emitting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To retrieve light from a substrate side by emitting light of arbitrary chromaticity (saturation, hue) by a single pixel. <P>SOLUTION: A semiconductor light emitting element comprises a first light emitting layer 3 and a second light emitting layer 9 laminated on a substrate 1 to emit lights of different chromaticities so that the first layer 3 is formed in a multiple quantum well structure. Since a forbidden band width can be changed by changing a crystal ratio of the layer 3 to the layer 9, the peak wavelength of the emitting light can be changed by the crystal ratio, and wavelength intensity characteristics of combined light of the lights emitted from the layers 3 and 9 are set to desired characteristics. Accordingly, the light having the arbitrary chromaticity can be emitted from the single pixel. The element also comprises a buffer layer 6 provided between the layer 3 and the layer 9, and since the light emitted from the layer 3 to an electrode 14 side is reflected to the substrate 1 side by the layer 6, the retrieving efficiency of the light from the substrate 1 side can be enhanced. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting device using a group III nitride semiconductor capable of emitting white light.

[0002]

2. Description of the Related Art Conventionally, a light emitting device in which a group III nitride semiconductor is formed on a sapphire substrate is known. Since the light emitting element emits blue, which is one of the three primary colors of light, it is expected to be applied to full color displays and the like. On the other hand, white is a color that humans have a good sense of color sense, and development of a white light emitting diode (LED) is expected. Therefore, as shown in FIG. 8, AlGaIn is formed on the stem 57.
Green LEDs 50a and 50d composed of P and Al
Red LED 50b made of GaInP and AlGaIn
By arranging the LED 50c that emits blue light composed of N and sealing it with resin, white light emission was obtained by mixing the light emitted from the LEDs 50a to 50d.

[0003]

However, in the above-mentioned prior art, in order to obtain white light emission, the LEDs 50a to 50d for emitting blue, red, and green colors are arranged on the same stem 57, respectively. Since it is necessary to encapsulate the resin, there are problems that the number of chips increases, the manufacturing becomes complicated, and the cost increases. Also, three-color LED 50
Since a to 50d are arranged in a plane, there is a problem that the color mixing property of light is low. In addition, each LED 50a-50
Since the light emitted from d is taken out from the electrode side, there is a problem that the emission brightness is low.

Therefore, in view of the above problems, an object of the present invention is to provide an LED which emits white light having a high color mixing property in a single pixel.
In particular, it is to obtain an LED with high emission brightness by extracting light from the sapphire substrate side.

[0005]

[Means for Solving the Problems] In order to solve the above problems, the means described in claim 1 can be adopted. According to this means, a group III nitride semiconductor (Al _x Ga _1-x ) _y In _1-y N (0 ≤ x ≤ 1; 0 ≤ y ≤ 1) containing no impurities is provided on the substrate, and In _z Ga _{1 -z} N (0 <z ≤ 1) in which a first light emitting layer that emits light of chromaticity is formed and emits light of chromaticity different from that emitted from the first light emitting layer A second light emitting layer consisting of is laminated on the first light emitting layer. And the first and second
The combined light of the lights emitted from the respective light emitting layers has a desired wavelength intensity characteristic, and the combined light is extracted from the substrate side. As a result, light having an arbitrary chromaticity can be emitted from a single pixel, and unlike the conventional configuration, a configuration in which arbitrary chromaticity is obtained by mixing light from a plurality of chips or a plurality of pixels is not provided. Therefore, the manufacturing is simplified and the manufacturing cost can be reduced. Further, by taking out the light emitted from each light emitting layer from the substrate side, it is possible to enhance the light emission brightness.

According to the second aspect of the present invention, at least one of the light emitting layers has a multiple quantum well structure, whereby the emission intensity can be further increased and the thickness of the well layer can be changed. The emission intensity can be controlled.

According to the third aspect, the light is emitted from each light emitting layer so that the average value of the chromaticity coordinates of the light emission of each light emitting layer becomes a desired coordinate on the xy chromaticity diagram. The desired wavelength intensity characteristic can be obtained.

According to the means described in claim 4, the average value of the chromaticity coordinates of the light emission of each light emitting layer is an average value weighted by the lightness of the light emission from each light emitting layer to obtain a desired color. A degree of synthetic light is obtained.

According to the means described in claim 5, the desired chromaticity coordinates are set to the coordinates (1/3, 1/3) of the substantially equal-energy white light to obtain white light with one pixel. be able to.

According to the means described in claim 6, the first and second light emitting layers are formed such that the chromaticity coordinates of the respective light emission are two points having a complementary color relationship on the xy chromaticity diagram. As a result, white light can be obtained with one pixel.

According to the seventh aspect, the mixed crystal ratio of each light emitting layer is set so that the light emitting layer closer to the substrate has a wider band gap than the light emitting layer farther from the substrate, and thus each light emitting layer. It is possible to prevent the light emission from the light absorption in the light emitting layer existing in the front, the light extraction efficiency is improved, and the controllability of chromaticity is improved. In each light emitting layer, the forbidden band width becomes wider as the Al mixed crystal ratio becomes higher, and the forbidden band width becomes narrower as the In mixed crystal ratio becomes higher.

[0012]

DETAILED DESCRIPTION OF THE INVENTIONFirst embodiment Hereinafter, the present invention will be described based on specific examples.
The present invention is not limited to the examples below. Figure
1 is the entire light emitting device 100 according to the first embodiment of the present invention.
FIG. 2 shows a cross-sectional configuration diagram, and FIGS. 2, 3 and 4 show the manufacturing process order.
The cross-sectional structure is shown. The light emitting element 100 is sapphire
It has a substrate 1, on which sapphire substrate 1
And a buffer layer 111 made of AlN having a thickness of about 0.05 μm,
Film thickness about 2μm, electron density 2 × 10¹⁸/cm³Silicon (Si)
High carrier concentration n consisting of GaN⁺Layer 2, total thickness about 5
50 Å InGaN multiple quantum well first light emitting layer 3, film
Thickness approx. 350Å, hole concentration 2 × 10 ¹⁷/ cm, magnesium (M
g) Doped Al_0.15Ga_0.85P-conductivity type crack consisting of N
Layer 4, thickness about 2000Å, magnesium (Mg) -doped Ga
A contact layer 5 made of N 2 is formed. The first
As shown in FIG. 2, the light emitting layer 3 is In_0.08Ga_0.92Made up of N
Barrier layer 31 and In_0.4Ga_0.6Well layer 32 consisting of N
They are stacked on each other in five cycles.

On the contact layer 5, GaAs is sequentially formed.
Buffer layer (reflecting layer) consisting of 6 and zinc (Zn) -doped p
-Type GaAs layer 7, zinc (Zn) -doped p-type Al _0.6 G
a p layer 8 made of a _0.4 As, second light emitting layer 9 made of Al _0.3 Ga _0.7 As, n layer 10 made of silicon (Si) -doped n-type Al _0.6 Ga _0.4 As, silicon (Si) -doped n-type A contact layer 11 made of GaAs is formed. Further, on the n ⁺ layer 2 and the contact layer 5, electrode forming regions A and B are formed, respectively.
And an electrode 1 made of Al on these regions A and B
Electrodes 13 made of 2 and Au / Ni are formed respectively. Then, Ni / AuGe / Ni is formed on the entire upper surface of the contact layer 11.
An electrode 14 made of / Au is formed.

Next, a method of manufacturing the light emitting device 100 having this structure will be described. The light emitting device 100 was manufactured by vapor phase epitaxy by a metal organic vapor phase epitaxy method (hereinafter referred to as “MOVPE”). The gas used was ammonia (NH ₃ )
, Carrier gas (H ₂ ), trimethylgallium (Ga (C
H _{3) 3)} (hereinafter referred to as "TMG"), trimethylaluminum _{(Al (CH 3) 3)} ( hereinafter referred to as "TMA"), trimethylindium _{(In (CH 3) 3)} ( hereinafter referred to as "TMI" ), Silane (SiH
_4), diethylzinc _{(Zn (C 2 H 5)} 2) ( hereinafter, referred to as "DEZ"), cyclopentadienyl magnesium _{(Mg (C 5 H 5)} 2)
(Hereinafter referred to as “CP ₂ Mg”), arsine (AsH ₃ ) and dimethylzinc (hereinafter referred to as “DMZ”).

First, a single crystal sapphire substrate 1 is mounted on a susceptor mounted in the reaction chamber of a MOVPE apparatus, with the a-plane cleaned by organic cleaning and heat treatment as the main surface. Next, the sapphire substrate 1 was baked at a temperature of 1100 ° C. while flowing H ₂ into the reaction chamber at a flow rate of ₂ liter / min for about 30 minutes under normal pressure. Then lower the temperature to 400 ° C and add H ₂ at 20 liter / min.
NH ₃ 10liter / min, TMA 1.8 × 10 ^-5 mol / min about 90
The buffer layer 2 made of AlN was formed to have a thickness of about 0.05 μm by supplying for 2 seconds. Next, the temperature was maintained at 1150 ° C, and H ₂ was added to 2
0 liter / min, NH ₃ 10 liter / min, TMG 1.7 × 10 ⁻⁴ mol / min, 20 silane diluted to 0.86 ppm with H ₂ gas
Introduced at a ^{rate of} × 10 ^-8 mol / min, film thickness of about 2.0 μm, silicon (S
i) A high carrier concentration n ⁺ layer 2 made of doped GaN was formed.

Thereafter, the temperature is kept at 900 ° C. and N ₂ or H _{2 is} added.
20 liter / min, NH ₃ 10 liter / min, TMG 1 × 10 ^-5
The barrier layer 31 made of GaN and having a film thickness of about 35Å was formed at a growth rate of 35Å / min by introducing TMI at a rate of 1 × 10 ^-5 mol / min for 1.5 minutes. Next, at 700 ° C., N ₂ or H ₂ ,
The well layer 32 made of In _0.4 Ga _0.6 N and having a film thickness of about 35 Å was formed at a growth rate of 10 Å / min while the supply amount of NH ₃ was kept constant.
By repeating such a procedure, as shown in FIG.
The barrier layer 31 and the well layer 32 were alternately laminated to form the first light emitting layer 3 having a thickness of about 550 Å, which was formed by laminating 6 layers and 5 layers, respectively.

Subsequently, the temperature was maintained at 1100 ° C. and N ₂ or H _{2 was} added.
20 liter / min, NH ₃ 10 liter / min, TMG 0.22 × 10
^-4 mol / min, TMA 0.1 × 10 ^-4 mol / min, and CP ₂ Mg
0.02 × 10 ⁻⁴ mol / min was introduced to form a cladding layer 4 made of Al _0.15 Ga _0.85 N doped with magnesium (Mg) and having a film thickness of about 350 Å. In this state, the cladding layer 4 is still an insulator having a resistivity of 10 ⁸ Ωcm or more. Then, at the same temperature, N ₂
Or ₂₀ liters / minute for H ₂ , 10 liters / minute for NH ₃ , and 0 for TMG.
Introduced 37 × 10 ^-4 mol / min and CP ₂ Mg 0.03 × 10 ^-4 mol / min, respectively, and apply magnesium (Mg) -doped Ga with a film thickness of approximately 2000
A contact layer 5 made of N 2 was formed. In this state,
The contact layer 5 is still an insulator having a resistivity of 10 ⁸ Ωcm or more.

Next, the contact layer 5 and the cladding layer 4 were uniformly irradiated with an electron beam by using an electron beam irradiation device. Electron beam irradiation conditions are acceleration voltage of about 10KV, sample current of 1μA,
The moving speed of the beam is 0.2 mm / sec, the beam diameter is 60 μmφ, and the degree of vacuum is 5.0 × 10 ⁻⁵ Torr. By this electron beam irradiation, the contact layer 5 and the cladding layer 4 each became a p-conduction type semiconductor having a predetermined hole concentration.

Next, the temperature was kept at 400 ° C., TMG was 1.12 × 10 ⁻⁴ mol / min and AsH ₃ was 5.6 × 10 ⁻³ together with the carrier gas.
The buffer layer 6 made of GaAs was formed on the contact layer 5 by introducing each mol / min. Next, the temperature is raised to 700 ° C. and TMG is added to the carrier gas at 1.12 × 10 ⁻⁴ mol / mol.
Min, AsH ₃ 5.6 × 10 ^-3 mol / min, DMZ 2 × 10 ^-6 mol / min
Then, a layer 7 made of zinc (Zn) -doped p-type GaAs was formed. Next, at the same temperature, TMG with carrier gas was 0.78 × 10 ^-4 mol / min, AsH ₃ was 5.6 × 10 4.
^-3 mol / min, DMZ 2 × 10 ^-6 mol / min, TMA 0.34 × 10
^-4 mol / min introduced and zinc (Zn) -doped p-type Al
_A p-layer 8 made of _0.6 Ga _0.4 As was formed.

Next, at the same temperature, TMG was introduced together with carrier gas at 0.95 × 10 ^-4 mol / min, AsH ₃ at 5.6 × 10 ^-3 mol / min, and TMA at 0.17 × 10 ^-4 mol / min, respectively. And Al
To form a second light-emitting layer 9 made of _0.3 Ga _{0 .7} As. Next, at the same temperature, add TMG with carrier gas to 0.78 × 10 ^-4.
Mol / min, AsH ₃ 5.6 × 10 ^-3 mol / min, SiH ₄ 1 × 10 ^-6
Mol / min, TMA 0.34 × 10 ⁻⁴ mol / min, respectively,
An n-layer 10 made of n-type Al _0.6 Ga _0.4 As doped with silicon (Si) was formed. Next, at the same temperature, with the carrier gas, TMG was 1.12 × 10 ^-4 mol / min, AsH ₃ was 5.6 × 10 ^-3.
Mol / min, SiH ₄ was introduced at 2 × 10 ⁻⁶ mol / min, and the contact layer 1 was made of silicon (Si) -doped n-type GaAs.
1 was formed.

Next, as shown in FIG. 2, the contact layer 1
On top of No. 1, Ti is formed to a thickness of 2000Å, and on top of that Ti layer
Forming Ni to a thickness of 9000Å, Ti / Ni metal mask layer 16
Was formed. Then, a photoresist 17 was applied on the metal mask layer 16. Then, by photolithography, as shown in FIG. 2, on the metal mask layer 16, the electrode forming portion A for the high carrier concentration n ⁺ layer 2 was formed.
The photoresist 17 of ^' was removed. Next, as shown in FIG. 3, the metal mask layer 16 not covered with the photoresist 17 was removed with an acidic etching solution.

Next, the contact layer 11, the n layer 10, the second light emitting layer 9, the p layer 8, the layer 7, the buffer layer 6, the contact layer 5, and the clad layer of the portion A ″ which is not covered with the metal mask layer 16. 4 and the first light emitting layer 3 with a vacuum degree of 0.04 Tor
r, high frequency power 0.44 W / cm ² , and BCl ₃ gas were supplied at a rate of 10 ml / min to perform dry etching, and then dry etching was performed using Ar. In this step, as shown in FIG. 4, the electrode formation region A was formed on the high carrier concentration n ⁺ layer 2. And
The contact layers 11 and n are formed by the same process as the formation of the region A.
Layer 10, second light emitting layer 9, p layer 8, layer 7 and buffer layer 6
Was dry-etched to form an electrode formation region B on the contact layer 5. Then, the metal mask layer 16 was removed.

Next, a layer of Ni / AuGe / Ni / Au was uniformly deposited, and an electrode 14 was formed on the contact layer 11 by applying a photoresist, a photolithography process, and an etching process. On the other hand, for the n ⁺ layer 2, aluminum (Al) is vapor-deposited to form the electrode 12, and for the contact layer 5, a layer made of Au / Ni is vapor-deposited to form the electrode 13.
Was formed. Thereafter, the wafer processed as described above is cut into each element, and the light emitting element 1 having the structure shown in FIG.
I got 00.

In the light emitting device 100 having this structure, the first light emitting layer 3 emitted blue-green light having a peak wavelength of 490 nm, and the second light emitting layer 9 emitted red light having a peak wavelength of 660 nm. This emission is represented by points U and V in the chromaticity diagram shown in FIG. 5, and the straight line connecting the points U and V is the coordinate (1 /
It passes through the isoenergy white point of (3,1 / 3). That is, the chromaticity at the V point and the chromaticity at the U point have a complementary color relationship. Therefore, white light emission can be obtained by mixing the two emitted lights, and the light emitted from the first light emitting layer 3 to the electrode 14 side is reflected to the substrate 1 side by the buffer layer 6 and the second light emitting layer. The light emitted from the electrode 9 to the side of the electrode 14 is transmitted to the substrate 1 by the electrode 14.
Since the light is reflected to the side, the efficiency of extracting light from the substrate 1 can be further increased.

In order to obtain more accurate white light emission,
The lightness of the V point light emission and the lightness of the U point light emission are weighted to obtain V
It may be designed so that the value obtained by averaging the chromaticity coordinate of the point and the chromaticity coordinate of the U point becomes the coordinate (1/3, 1/3).

That is,

[Number 1] _{{(x V, y V)} · M V + (x U, y U) · M U}
/ (M _V + M _U ) = (1 / 3,1 / 3) where (x _V, y _V ) is the chromaticity coordinate of the V point, (x _U, y _U ) is the chromaticity coordinate of the U point, and M _V and M _U are the lightness of the light emission at the points V and U, respectively.

The emission intensity that determines the brightness may be changed by changing the thickness of each well layer 32. In the case of the quantum well structure, the emission efficiency can be improved and the emission intensity can be increased by making the thickness of the well layer thinner. By changing the mixed crystal ratios of the first light emitting layer 3 and the second light emitting layer 9, respectively,
The chromaticity coordinates of the U point and the V point can be changed respectively. Therefore, so that the chromaticity coordinates and brightness of the light emission of the first light-emitting layer 3 and the chromaticity coordinates and brightness of the light emission of the second light-emitting layer 9 satisfy the above formula 1, their mixed crystal ratio and thickness It is possible to obtain pure white light emission by controlling the brightness.

In the above embodiment, the emission wavelength is short,
That is, the first light emitting layer 3 having a wide forbidden band exists on the light extraction surface (sapphire substrate 1) side of the second light emitting layer 9 having a long emission wavelength, that is, a narrow forbidden band. For this reason,
The long wavelength 660 nm light emitted from the second light emitting layer 9 is
Since it is emitted to the outside without being absorbed by the first light emitting layer 3, the light extraction efficiency can be improved.

In this embodiment, the first light emitting layer 3 and the second light emitting layer 3
The emission wavelengths emitted from the light emitting layer 9 are 490 nm and 66, respectively.
Although the wavelength is set to 0 nm, pure white light can be obtained even in combination with other wavelengths as long as the relation of the above formula 1 is satisfied. Further, by determining the mixed crystal ratio and the thickness of each light emitting layer so that the left side of Formula 1 is equal to the chromaticity coordinate of the desired light, it is possible to obtain the light of the desired chromaticity.

In the above embodiment, the first light emitting layer 3 is multiplexed.
Although it has a quantum well structure, it may be composed of a single quantum well.
Yes. That is, a quantum well structure in which the mixed crystal ratio is changed for each well layer
The first light emitting layer 3 may be structured. Also, in the above embodiment
Forms a well layer 32 and a barrier layer 31 of InGaN semiconductor
However, the general formula (Al_xGa_1-x)_yIn_1-yN (0 ≤ x1; 0 ≤ y ≤ 1)
The well layer 32 and the barrier layer 31 are formed of the semiconductor to fill.
You may. Further, in the above embodiment, the composition of the second light emitting layer 9 is
To Al_0.3Ga_0.7As, but general formula Al _zGa_1-zAs (0 ≦ z ≦ 1)
A layer having an arbitrary composition ratio satisfying the above conditions can be used.

Second Embodiment In the above-mentioned first embodiment, the composition of the second light emitting layer 9 is changed to Al _0.3 Ga _0.7.
Although As is used, the present embodiment is characterized in that the second light emitting layer is made of InGaN. FIG. 6 is a schematic sectional view showing the structure of the light emitting device 101 according to the second embodiment of the present invention.
The light emitting element 101 has a sapphire substrate 1, and on the sapphire substrate 1, an Al film having a thickness of about 0.05 μm is formed in order.
Buffer layer 111 made of N, film thickness about 2 μm, electron concentration
High carrier concentration n ⁺ layer 2 consisting of 2 × 10 ¹⁸ / cm ³ silicon (Si) -doped GaN, first emissive layer 300 consisting of multiple quantum wells of InGaN with total film thickness of about 550 Å, film thickness of about 350 Å , P-conductivity type clad layer 4 composed of Al _0.15 Ga _0.85 N doped with magnesium (Mg), film thickness of about 5000Å, magnesium (Mg)
A contact layer 5 made of doped GaN is formed. Although not shown, the first light emitting layer 300 includes a barrier layer made of GaN and a well layer made of In _0.35 Ga _0.65 N, which are alternately formed.
It is stacked in cycles. Then, on the contact layer 5, a layer 18 made of p-type AlGaN doped with magnesium (Mg), a second light emitting layer 19 made of In _0.45 Ga _0.55 N, and a contact layer made of GaN doped with silicon (Si) are sequentially formed. 20 are formed.

Further, on the n ⁺ layer 2 and the contact layer 5,
Electrode forming regions C and D are provided respectively, and an electrode 12 made of Al and an electrode 13 made of Au / Ni are formed on these regions C and D, respectively. Then, the electrode 15 made of Al is formed on the entire upper surface of the contact layer 20.

The manufacturing method of this light emitting device 101 is similar to that of the first embodiment, except that the buffer layer 111 and n ⁺ are sequentially formed on the substrate 1.
After forming the layer 2, the first light emitting layer 300, the clad layer 4, the contact layer 5 and the layer 18, the layer 18, the contact layer 5 and the clad layer 4 are uniformly irradiated with an electron beam by using an electron beam irradiation device. The p-conduction type. After that, the second light emitting layer 19 and the contact layer 20 are sequentially formed on the layer 18,
Electrode formation regions C and D are formed on the n ⁺ layer 2 and the contact layer 5, respectively, by dry etching. And
The electrode 14 is formed on the second contact layer 20, and the electrodes 12 and 13 are formed on the electrode formation regions C and D, respectively. In this way, the light emitting device 101 having the sectional structure shown in FIG. 6 is obtained.

The light emitting device 101 having this structure emits blue light having a peak wavelength of 470 nm from the first light emitting layer 300,
The light emitting layer 19 emitted yellowish green light having a peak wavelength of 570 nm. Although not shown, this luminescence is represented by two coordinate points in the chromaticity diagram, and the straight line connecting the points is the coordinate (1 / 3,1 /
It passes through the isoenergy white point of 3). That is, these two points have a complementary color relationship with each other. Therefore, white light emission can be obtained by mixing these two light emissions. Also, the first light emitting layer 3
00 and the respective lights emitted from the second light emitting layer 19 to the electrode 15 side are reflected to the substrate 1 side by the electrode 15, so that the light can be effectively extracted from the substrate 1 side.
Further, by extracting light from the substrate 1 side, the first light emitting layer 300 having a short emission wavelength is arranged on the substrate 1 side, so that the light having a long emission wavelength emitted from the second light emitting layer 19 is the first emission light. Light is not absorbed by the layer 300, and light extraction efficiency can be improved. Thus, the second light emitting layer 1
By forming 9 with In _0.45 Ga _0.55 N, the same effect as in the first embodiment can be obtained.

In this embodiment, the first light emitting layer 300 and the second light emitting layer 300
The emission wavelengths emitted from the light emitting layer 19 are 470 nm and 470 nm, respectively.
Although the wavelength is 570 nm, pure white light can be obtained even in combination with other wavelengths, as long as the relation of the above-mentioned formula 1 is satisfied. Further, by determining the mixed crystal ratio and the thickness of each light emitting layer so that the left side of Formula 1 is equal to the chromaticity coordinate of the desired light, it is possible to obtain the light of the desired chromaticity.

Although the first light emitting layer 300 has a multiple quantum well structure in the present embodiment, it may have a single quantum well.
That is, the first light emitting layer 300 may have a quantum well structure in which the mixed crystal ratio is changed for each well layer. Further, in the above embodiment, the well layer and the barrier layer were formed of InGaN semiconductor,
The well layer and the barrier layer may be formed of a semiconductor that satisfies the general formula (Al _x Ga _1-x ) _y In _1-y N (0 ≤ x1; 0 ≤ y ≤ 1).

In each of the above-mentioned embodiments, the well layer is not doped with impurities. However, donor impurities such as silicon, acceptor impurities such as zinc, and other elements of groups 2, 4 and 6 are added as impurities. May be. Further, both the donor impurity and the acceptor impurity may be added to the well layer.

In each of the above embodiments, the barrier layer may be undoped, and donor impurities (eg, silicon) and acceptor impurities (eg, zinc) may be alternately added to the well layers. Furthermore, donor impurities (for example,
Silicon) may be added and an acceptor impurity (eg, zinc) may be added to the barrier layer. Conversely, acceptor impurities may be added to the well layer and donor impurities may be added to the barrier layer. These characteristics concerning the distribution of impurities can change the emission wavelength together with the mixed crystal ratio of the well layer and the barrier layer. The well layer and barrier layer may be n-type, p-type, or semi-insulating.

In each of the above embodiments, the thickness of the cladding layer 4 is preferably 2 nm to 70 nm. The thickness of the clad layer 4 is 2 nm
If the thickness is smaller than the above range, the effect of confining carriers is reduced and the luminous efficiency is reduced, which is not desirable. In each of the above embodiments, the contact layer 5 preferably has a thickness of 2 nm to 500 nm. If the thickness of the contact layer 5 is thinner than 2 nm, the number of holes to be injected is reduced, so that the luminous efficiency is lowered, and the ohmic property is deteriorated to increase the contact resistance, which is not desirable. Further, when each layer exceeds the above upper limit thickness,
The light emitting layer is exposed to the growth temperature or higher for a long time, and the effect of improving the crystallinity of the light emitting layer decreases, which is not desirable.

In each of the above embodiments, the cladding layer 4
1 × 10¹⁷~ 1 x 10¹⁸/cm ³Is desirable. Ho
1 × 10¹⁸/cm³If the above, the impurity concentration is high
It is desirable because the crystallinity decreases and the light emitting efficiency decreases.
Without, 1 x 10¹⁷/cm³When the value is below, the series resistance becomes high.
It is not desirable because it is too much.

Third Embodiment In the first and second embodiments described above, two light emitting layers emitting light of different chromaticity are provided, but in the present embodiment, light emission emitting light of different chromaticity. The feature is that it has three layers. FIG. 7 shows a light emitting device 1 according to a third embodiment of the present invention.
It is a schematic cross-sectional view showing the configuration of No. 02. Light emitting element 10
2 has a sapphire substrate 1 on which a buffer layer 11 made of AlN with a thickness of about 0.05 μm is formed in order.
1, a film thickness of about 2 μm, electron concentration of 2 × 10 ¹⁸ / cm ³ of silicon (S
i) A high carrier concentration n ⁺ layer 2 made of doped GaN, a first light emitting layer 23 made of In _0.35 Ga _0.65 N having a film thickness of about 35 Å, a layer 24 made of GaN having a film thickness of about 35 Å, a film thickness of about 500 Å Magnesium (Mg) -doped Al _0.15 Ga _0.85 N p-conductivity layer 25, magnesium (Mg) -doped Ga with a thickness of about 5000 Å
A p-conduction type contact layer 26 made of N 2 is formed.

On the contact layer 26, a film thickness of about
A p-conducting layer 27 made of 500 Å magnesium (Mg) -doped Al _0.15 Ga _0.85 N, a layer 28 made of GaN having a thickness of about 35 Å, and a second light emitting layer made of In _0.45 Ga _0.55 N having a thickness of about 35 Å. 29, an n-conductivity type contact layer 30 made of GaN doped with silicon (Si) and having a film thickness of about 5000Å is formed. Then, on the contact layer 30, GaAs with a film thickness of about 2000 Å is sequentially formed.
Buffer layer 31 consisting of, silicon (Si) with a film thickness of about 5000Å
N-conductivity type layer 32 made of doped GaAs, film thickness about 2000Å
Of n-type Al _0.6 Ga _0.4 As doped with silicon (Si)
Conductive layer 33, third light emitting layer 34 made of Al _0.3 Ga _0.7 As with a thickness of about 1000Å, zinc (Zn) -doped Al with a thickness of about 2000Å
_A p-conduction type layer 35 made of _0.6 Ga _0.4 As and a contact layer 36 made of zinc (Zn) -doped p-conduction type GaAs having a film thickness of about 5000 Å are formed.

Further, the n ⁺ layer 2, the contact layers 26 and 30
Electrode forming regions E, F and G are provided on the upper side, and electrodes 37 made of Al are formed on these regions E, F and G, respectively.
An electrode 38 made of Ni / Au and an electrode 39 made of Al are respectively formed. An electrode 40 made of Au / AuZn is formed on the entire upper surface of the contact layer 36.

As in the first and second embodiments, the method of manufacturing the light emitting device 102 includes the buffer layer 11 on the substrate 1 in order.
1, the n ⁺ layer 2, the first light emitting layer 23, the layer 24, the layer 25, the contact layer 26 and the layer 27 are formed, and then the layer 27, the contact layer 26 and the layer 25 are uniformly formed by using an electron beam irradiation device. It is irradiated with an electron beam to make it a p-conductivity type. After this, layer 27
Layer 28, second light emitting layer 29, contact layer 3
0, buffer layer 31, layer 32, layer 33, third light emitting layer 3
4, the layer 35 and the contact layer 36 are formed. And
Electrode formation regions E, F, and G are formed by dry etching, an electrode 40 is formed on the contact layer 36, and electrodes 37, F are formed on the electrode formation regions E, F, and G, respectively.
38 and 39 are formed. In this way, the light emitting device 102 having the sectional structure shown in FIG. 7 is obtained.

With three different chromaticity emissions, each emission is a color
Represented by three coordinate points on the diagram, each coordinate point is a straight line
Get light of arbitrary chromaticity inside the triangle
be able to. Here, the chromaticity coordinates of the light you want to obtain are (x_O,y
_O), Chromaticity T, chromaticity R, chromaticity S coordinates and lightness, respectively
, (X_T,y_T), (X_R,y_R), (X_S,y_S), M_T,
M_R,M _SThen, the color of each emission point should be
You can set the degree and brightness.

[0046]

(2) (x _O, y _O ) = {(x _T, y _T ) · M _T + (x _R,
y _R ) ・ M _R + (x _S, y _S ) ・ M _S } / (M _T + M _R +
M _S )

When the brightness of the light emission at each point is I _T, I _R, I _S , M _T = I _T / y _T , M _R = I _R / y _{R ,} M _S =
It is also I _S / y _S. Light-emitting element 102 in this embodiment
Emits blue light having a peak wavelength of 480 nm from the first light emitting layer 23, emits yellow-green light having a peak wavelength of 570 nm from the second light emitting layer 29, and emits blue light having a peak wavelength of 660 n from the third light emitting layer 34.
Emitted m red light. The average value of the chromaticity coordinates of the emitted light was (1 / 3,1 / 3), and white light could be obtained from the combined light. In addition, the first light emitting layer 23 and the second light emitting layer 2
The light emitted from 9 to the electrode 40 side is reflected to the substrate 1 side by the buffer layer 31, and the light emitted from the third light emitting layer 34 to the electrode 40 side is reflected to the substrate 1 side by the electrode 40. Therefore, the light extraction efficiency from the substrate 1 can be further increased. By extracting light from the substrate 1 side, the second light emitting layer 29 having an emission wavelength shorter than that of the third light emitting layer 34 is disposed on the substrate 21 side, and the first light emitting layer 300 having an emission wavelength shorter than that of the second light emitting layer 29. Is disposed on the substrate 1 side, light emitted from the second light emitting layer 19 and the third light emitting layer 34 is not absorbed by the light emitting layers located in front of each other, and the light extraction efficiency is improved. be able to. By providing the three light emitting layers in this way, the same effects as those of the first and second embodiments can be obtained.

In this embodiment, the composition of the first light emitting layer 23 is In
_{Although 0.35} Ga _0.65 N is used, a layer having an arbitrary composition ratio satisfying the general formula In _x1 Ga _1-x1 N (0 ≦ x1 ≦ 1) can be used. In addition, in the present embodiment, the composition of the second light emitting layer 19 is In _0.45 Ga _0.55 N, but any composition ratio satisfying the general formula In _X2 Ga _1-x2 N (0 ≦ x2 ≦ 1; x1 <x2) is obtained. Although a layer can be used and the composition of the third light emitting layer 34 is Al _0.3 Ga _0.7 As, the general formula Al _x3 Ga _1-x3 As (0 ≦
A layer having an arbitrary composition ratio satisfying x3 ≦ 1) can be used.

In this embodiment, each light emitting layer 23, 2
The wavelengths of the light emitted from 9 and 34 are not limited to the values shown above, and pure white light can be obtained even in combination with other wavelengths as long as the relationship of Equation 2 is satisfied. You can Further, by determining the mixed crystal ratio and the thickness of each light emitting layer so that the right side of the equation 2 becomes equal to the chromaticity coordinate of the desired light, it is possible to obtain the light of the desired chromaticity.

In each of the above embodiments, sapphire was used as the substrate, but SiC, MgAl ₂ O ₄ or the like can be used.
In addition, each layer consisting of GaN, InGaN, and AlGaN has an arbitrary composition ratio.
3 consisting of (Al _x Ga _1-x ) _y In _1-y N (0 ≤ x ≤ 1; 0 ≤ y ≤ 1)
Group nitride semiconductors can be used.

As indicated above, according to the present invention,
By stacking multiple light-emitting layers that emit light of different chromaticity on the substrate and extracting the combined light of the light emitted from each light-emitting layer from the substrate side as the desired wavelength intensity characteristic, you can arbitrarily select from a single pixel. Light having chromaticity can be emitted with high brightness, and the manufacturing cost of the light emitting element can be reduced. Further, by reflecting the light emitted from the light emitting layer to the substrate side using the reflective layer, it is possible to further increase the light emission brightness of the light emitting element.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing the structure of a light emitting device according to a first embodiment of the invention.

FIG. 2 is an explanatory view showing a method for manufacturing the light emitting device according to the first embodiment of the present invention.

FIG. 3 is an explanatory view showing a method for manufacturing the light emitting device according to the first embodiment of the present invention.

FIG. 4 is an explanatory view showing a method for manufacturing the light emitting device according to the first embodiment of the present invention.

FIG. 5 is an explanatory diagram showing composition of chromaticity of the light emitting device according to the first embodiment of the present invention.

FIG. 6 is a schematic cross-sectional view showing the structure of a light emitting device according to a second embodiment of the invention.

FIG. 7 is a schematic cross-sectional view showing the structure of a light emitting device according to a third embodiment of the invention.

FIG. 8 is a schematic plan view showing a configuration of a conventional light emitting element.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Sapphire substrate 2 ... High carrier concentration n ^<+> layer 3 ... 1st light emitting layer 31 ... Well layer 32 ... Barrier layer 4 ... Cladding layer 5, 11 ... Contact layer 6 ... Buffer layer 8 ... P layer 9 ... 2nd light emitting layer 10 ... N layers 12-14 ... Electrode 15 ... Pad 100 ... Light emitting element

Continued front page    (72) Inventor Norikatsu Koide             Aichi Prefecture Kasuga-cho, Nishikasugai-gun Ochiai character Nagahata 1             Address within Toyoda Gosei Co., Ltd. (72) Inventor Masayoshi Koike             Aichi Prefecture Kasuga-cho, Nishikasugai-gun Ochiai character Nagahata 1             Address within Toyoda Gosei Co., Ltd. (72) Inventor Junichi Umezaki             Aichi Prefecture Kasuga-cho, Nishikasugai-gun Ochiai character Nagahata 1             Address within Toyoda Gosei Co., Ltd. (72) Inventor Mitsuo Yuguchi             Aichi Prefecture Kasuga-cho, Nishikasugai-gun Ochiai character Nagahata 1             Address within Toyoda Gosei Co., Ltd. (72) Inventor Shinya Asami             Aichi Prefecture Kasuga-cho, Nishikasugai-gun Ochiai character Nagahata 1             Address within Toyoda Gosei Co., Ltd. (72) Inventor Kenji Ito             Aichi Prefecture Nagachite Town Aichi District             Ground 1 Toyota Central Research Institute Co., Ltd. (72) Inventor Toru Kaji             Aichi Prefecture Nagachite Town Aichi District             Ground 1 Toyota Central Research Institute Co., Ltd. (72) Inventor Kazuyoshi Tomita             Aichi Prefecture Nagachite Town Aichi District             Ground 1 Toyota Central Research Institute Co., Ltd. (72) Inventor Takahiro Ozawa             Aichi Prefecture Nagachite Town Aichi District             Ground 1 Toyota Central Research Institute Co., Ltd. F-term (reference) 5F041 AA03 AA12 CA05 CA13 CA22                       CA34 CA49 CA53 CA57 CA65                       CA74 CA77 CA83 CA92 CB28

Claims (7)

[Claims] 1. A Group III nitride semiconductor (Al _x Ga _{1- x} ) _y In _1-y N (0 ≤ x ≤ 1; 0 ≤ y ≤ 1) formed on a substrate and containing no impurities
A first light-emitting layer that emits light of a predetermined chromaticity, and light that emits light of a chromaticity different from the light emitted from the first light-emitting layer and is laminated on the first light-emitting layer. In _z Ga _1-z N (0 <z
≦ 1) second light emitting layer, and the combined light of the lights emitted from the first and second light emitting layers has a desired wavelength intensity characteristic, and the combined light is extracted from the substrate side. A semiconductor light emitting device characterized by the above. 2. The semiconductor light emitting device according to claim 1, wherein at least one of the light emitting layers has a multiple quantum well structure. 3. The semiconductor light emitting device according to claim 1, wherein an average value of chromaticity coordinates of light emission of each of the light emitting layers is formed to be a desired coordinate on an xy chromaticity diagram. . 4. The semiconductor light emitting device according to claim 3, wherein the average value is an average value weighted by the brightness of light emitted from each of the light emitting layers. 5. The desired coordinates are substantially the same-energy white light coordinates (1/3, 1/3).
Alternatively, the semiconductor light emitting device according to the item 4. 6. The first and second light emitting layers are formed such that the chromaticity coordinates of the respective emitted lights are two points having a complementary color relationship on the xy chromaticity diagram. Item 3. The semiconductor light emitting device according to item 3. 7. The mixed crystal ratio of each of the light emitting layers is set so that the forbidden band width of the light emitting layer closer to the substrate is wider than that of the light emitting layer farther from the substrate.
The semiconductor light emitting device according to any one of 1.