JPH1022525A - Iii group nitride semiconductor light emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a light with an arbitrary chromaticity, especially, a nearly equivalent white-light emission to an equi-energy white light, in a single pixel, by varying the mixed crystal ratios of a plurality of light emitting well layers to equalize the wavelength-intensity characteristic of a light synthesized out of the emission lights from the respective well layers to a desired characteristic. SOLUTION: In a light emitting diode, an yellow green light is emitted from a first multiple quantum well 51, and a blue light is emitted from a second multiple quantum well 52. Their luminous intensities determining their lightnesses may be varied by changing the thicknesses of the respective well layers 512, 522. In the case of a quantum well structure, the smaller the thickness of a well layer is, the higher its luminous efficiency is to make its luminous intensity incresable. In this way, varying the mixed crystal ratio of the first multiple quantum well 51, the chromaticity coordinates of a V-point can be varied, and varying the mixed crystal ratio of the second multiple quantum well 52, the chromaticity coordinates of a U-point can be varied. Therefore, controlling the mixed crystal ratios and the thicknesses of the first and second multiple quantum wells 51, 52, a pure white-light emission can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a group III nitride semiconductor light emitting device 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 has been known. Since the light-emitting element emits blue light, which is one of the three primary colors of light, application to a full-color display or the like is expected.

[0003] On the other hand, white is a color that has a favorable impression in terms of human color sensation, and development of a light emitting diode (LED) that emits white light is expected.

[0004]

However, in order to obtain white light emission in a conventional light emitting diode, a blue LE is required.
D, a red LED, and a green LED are arranged on the same stem, and white light is obtained by mixing light emitted from each chip. For this reason, there are problems that the number of chips for obtaining white color increases, the manufacturing becomes complicated, the manufacturing takes time, and the cost increases. or,
In general, even in an LED that emits light of any color mixture, LEDs that emit light of each of the three primary colors must be arranged on the same surface, and there is a similar problem.

Accordingly, the present invention has been made to solve the above-mentioned problem, and an object of the present invention is to make a single pixel emit light of an arbitrary chromaticity (saturation, hue). In particular, it is to obtain white light emission substantially equivalent to equal energy white light.

[0006]

The band gap can be changed by changing the mixed crystal ratio of each well layer of the multiple quantum well structure. Therefore, the peak wavelength of light emission can be changed by the mixed crystal ratio. it can. According to the first aspect of the present invention, in a light emitting device having a multiple quantum well structure using a group III nitride semiconductor, by changing a mixed crystal ratio of a plurality of light emitting well layers, a combined light of light emitted from each well layer is changed. Since the wavelength intensity characteristic is a desired characteristic, light having an arbitrary chromaticity can be emitted from a single pixel. Therefore, as before,
Since an arbitrary chromaticity is not obtained by mixing light from a plurality of chips or a plurality of pixels, manufacturing is simplified and manufacturing cost can be reduced.

Since the peak wavelength of light emission can be changed by changing the mixed crystal ratio of the well layer, the coordinate point on the xy chromaticity diagram of the emitted light can be changed by the mixed crystal ratio. Therefore, as in claim 2, the mixed crystal ratio of each well layer that emits light is determined such that the average value of the chromaticity coordinates of light emission of each well layer becomes a desired coordinate on the xy chromaticity diagram. By setting the ratio, the chromaticity of the combined light of the light from each well layer can be set to a desired value.

Further, the chromaticity coordinates of the light emitted from each well layer are weighted by the brightness of each light so that the average value of the chromaticity coordinates of each well layer becomes a desired chromaticity. By selecting the crystal ratio, synthetic light having a desired chromaticity can be obtained.

Further, by setting the desired chromaticity coordinates to substantially the coordinates (1/3, 1/3) of the equal energy white light, it is possible to obtain white light with one pixel. it can.

Further, the mixed crystal ratio of each of the at least two light emitting well layers is determined by comparing the chromaticity coordinates of the light emission of each well layer with two points having complementary colors on the xy chromaticity diagram. With such a ratio, white light can be obtained with one pixel.

[0011] The brightness of the luminescent color perceived by a person depends on the luminous intensity, and the luminous intensity can be controlled by the thickness of the well layer. Therefore, with the configuration according to the sixth aspect, the wavelength intensity characteristics of the combined light can be changed. That is, the chromaticity can be changed by one pixel.

Further, the mixed crystal ratio of each well layer is set such that the sum of the wavelength intensity characteristics of light emitted from each well layer becomes the wavelength intensity characteristic of white light. Thus, white light can be obtained from one pixel.

[0013] Further, the plurality of well layers may include:
By setting the mixed crystal ratio so that the forbidden band becomes wider from the side closer to the light extraction surface, light emission from each well layer can be prevented from being absorbed by the well layer existing in front, and light The takeout efficiency is increased, and the controllability of chromaticity is improved.

Further, as a ninth aspect, the group III nitride semiconductor is (Al _x Ga _{1 -X} ) _y In _{1 -y} N (0 ≦ x ≦ 1; 0 ≦ y ≦ 1).
And by changing the mixed crystal ratio x, y of each well layer,
By changing the forbidden band width of each well layer, the peak wavelength of light emission can be changed. The bandgap becomes wider as the mixed crystal ratio of Al increases, and the bandgap becomes narrower as the mixed crystal ratio of In increases.

Further, in addition to the change in the mixed crystal ratio of each well layer, an acceptor impurity or / and / or a donor impurity is added to each well layer or / and barrier layer. The chromaticity of light emission from each well layer can be changed by changing the concentration, and the chromaticity of light emission can be more precisely controlled by the mixed crystal ratio and the impurities.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described based on specific embodiments. The present invention is not limited to the following examples. FIG. 1 shows an overall view of the light emitting device 100 according to the embodiment of the present invention. The light emitting device 100 has a sapphire substrate 1, and a 0.05 μm AlN buffer layer 2 is formed on the sapphire substrate 1.

On the buffer layer 2, a film thickness of about
4.0 μm, silicon (Si) doped with 2 × 10 ¹⁸ / cm ³ electron concentration
High carrier concentration n ⁺ layer 3 made of GaN, thickness about 0.5 μm
N layer 4 composed of GaN doped with silicon (Si) having an electron concentration of 5 × 10 ¹⁷ / cm ³ , light emitting layer 5 composed of multiple quantum wells of InGaN having a total film thickness of about 65 nm, film thickness of about 10 nm, and hole concentration of 2 × 10 ¹⁷ / c
m ³ , magnesium (Mg) concentration 5 × 10 ¹⁹ / cm ³ doped Al
_A p-type cladding layer 71 made of _0.08 Ga _0.92 N, having a thickness of about 35 nm and a hole concentration of 3 × 10 ¹⁷ / cm ³ of magnesium (M
g) A first contact layer 72 made of GaN doped with 5 × 10 ¹⁹ / cm ³ , having a thickness of about 5 nm and a magnesium (Mg) concentration of 1 × 10 ²⁰ / cm ^{3 with} a hole concentration of 6 × 10 ¹⁷ / cm ^3. A second contact layer 73 of p ⁺ made of GaN is formed. A transparent electrode 9 composed of a double layer of Ni / Au is formed on the entire upper surface of the second contact layer 73, and a pad 10 for bonding composed of a double layer of Ni / Au is formed at a corner of the transparent electrode 9. Have been. Further, an electrode 8 made of Al is formed on the n ⁺ layer 3.

As shown in FIG. 2, the light emitting layer 5 is made of In _0.1 Ga.
_A 35 nm-thick first multiple quantum well 51 composed of a barrier layer 511 composed of _0.9 N and a well layer 512 composed of In _0.68 Ga _0.32 N, a well layer 522 composed of In _0.3 Ga _0.7 N and In _0.05
30 nm thick composed of barrier layer 521 made of Ga _0.95 N
And the second multiple quantum well 52.

Next, a method of manufacturing a semiconductor device having this structure will be described. The light emitting device 100 was manufactured by vapor phase growth using metal organic chemical vapor deposition (hereinafter, MOVPE). The gases used were ammonia (NH ₃ ), carrier gas (H ₂ ), and trimethylgallium (Ga (CH ₃ ) ₃ ) (hereinafter “TMG
), Trimethyl aluminum (Al (CH ₃ ) ₃ ) (hereinafter referred to as “TMA”), trimethyl indium (In (CH ₃ ) ₃ )
(Hereinafter referred to as “TMI”), silane (SiH ₄ ), diethylzinc
(Zn (C ₂ H ₅ ) ₂ ) (hereinafter referred to as “DEZ”) and cyclopentadienyl magnesium (Mg (C ₅ H ₅ ) ₂ ) (hereinafter referred to as “CP ₂ Mg”).

First, a single-crystal sapphire substrate 1 is mounted on a susceptor placed in a reaction chamber of an MOVPE apparatus, with the a-plane cleaned by organic cleaning and heat treatment as a 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 at normal pressure for about 30 minutes.

Next, by lowering the temperature to 400 ° C., and H ₂
20 liter / min, NH ₃ 10 liter / min, TMA 1.8 × 10 ^-5
The AlN buffer layer 2 was supplied at about 0.1 mol / min for about 90 seconds.
It was formed to a thickness of 05 μm. Next, the temperature of the sapphire substrate 1 was maintained at 1150 ° C., H ₂ was 20 liter / min, and NH ₃ was 10 lite.
r / min, TMG 1.7 × 10 ^-4 mol / min, 0.86p by H ₂ gas
Silane diluted at 20 × 10 ⁻⁸ mol / min was introduced for 40 minutes at a film thickness of about 4.0 μm, an electron concentration of 1 × 10 ¹⁸ / cm ³ , and a silicon concentration of 4 × 10 ¹⁸ / cm ³ (Si). 3.) A high carrier concentration n ⁺ layer 3 made of doped GaN was formed.

After forming the high carrier concentration n ⁺ layer 3, the temperature is maintained at 1100 ° C. and H ₂ is reduced to 20 liter / H _2.
Min, NH ₃ at 10 liter / min, TMG at 1.12 × 10 ^-4 mol / min
Min, silane to 10 × 10 diluted to 0.86ppm with H ₂ gas
Introduced at ^-9 mol / min for 30 minutes, film thickness approx.
× 10 ¹⁷ / cm ³ , silicon (Si) with a silicon concentration of 1 × 10 ¹⁸ / cm ³
An n layer 4 made of doped GaN was formed.

Thereafter, the temperature of the sapphire substrate 1 is raised to 660 ° C.
And N ₂ or H ₂ at 20 liter / min, NH ₃ at 10 liter / min.
Min, TMG at 2.0 × 10 ^-4 mol / min and TMI at 0.03 × 10 ^-4 mol / min for 1.5 minutes, consisting of In _0.1 Ga _0.9 N with a growth rate of 0.1 μm / h and a film thickness of about 5 nm. A barrier layer 511 was formed. Next, while keeping the temperature of the sapphire substrate 1 the same,
TMG is 7.2 × 10 with the supply amount of N ₂ or H ₂ , NH ₃ constant.
^-5 mol / min, TMI was introduced at 0.19 × 10 ^-4 mol / min for 1.5 minutes, and the growth rate was 0.1 μm / h and the thickness of In _0.68 Ga
_A well layer 512 of _0.32 N was formed. By repeating such a procedure, as shown in FIG.
The first quantum well 51 having a thickness of 70 nm was formed by laminating four and three layers alternately with 1 and the well layer 512.

Next, similarly, the temperature of the sapphire substrate 1 is changed.
Held in 660 ° C., the supply amount of N ₂ or H ₂ without changing, 1.6 × 10 ^-4 mol / min TMG, by introducing 1.5 minutes TMI at 0.08 × 10 ^-4 mol / min, growth rate At 0.1 μm / h, a well layer 522 made of In _0.3 Ga _0.7 N and having a thickness of about 5 nm was formed. Next, while keeping the temperature of the sapphire substrate 1 the same,
Without changing the supply amount of N ₂ or H ₂ , TMG is 2.1 ×
10 ^-4 mol / min, TMI was introduced at 0.01 × 10 ^-4 mol / min for 1.5 minutes, and at a growth rate of 0.1 μm / h, In _0.05 Ga with a film thickness of about 5 nm was used.
_A barrier layer 521 made of _0.95 N was formed. By repeating such a procedure, as shown in FIG.
The second quantum well 52 having a thickness of 60 nm was formed by alternately laminating three layers of the second and the barrier layers 521, respectively.

Subsequently, the temperature was maintained at 1100 ° C. and N ₂ or H ₂
20 liter / min, NH ₃ 10 liter / min, TMG 0.5 × 10
^-4 mol / min, TMA 0.47 × 10 ^-5 mol / min, and CP ₂ Mg
^Was introduced at 2 × 10 ⁻⁷ mol / min for 2 minutes to form a cladding layer 71 made of magnesium (Mg) -doped Al _0.08 Ga _0.92 N and having a thickness of about 10 nm. The magnesium concentration of the cladding layer 71 is 5 × 10 ¹⁹ / cm ³ . In this state, the cladding layer 7
1 is an insulator having a resistivity of 10 ⁸ Ωcm or more.

Next, the temperature is maintained at 1100 ° C. and N ₂ or H ₂ is added.
20 liter / min, NH ₃ 10 liter / min, TMG 0.5 × 10 ^-4
Mole / min and CP ₂ Mg were introduced at 2 × 10 ⁻⁸ mol / min for 4 minutes to form a first contact layer 72 made of magnesium (Mg) -doped GaN having a thickness of about 35 nm. The magnesium concentration of the first contact layer 72 is 5 × 10 ¹⁹ / cm ³ . In this state, the first contact layer 72 still has a resistivity of 10
It is an insulator of ⁸ Ωcm or more.

Next, the temperature was maintained at 1100 ° C. and N ₂ or H ₂ was added.
20 liter / min, NH ₃ 10 liter / min, TMG 0.5 × 10 ^-4
Mol / min and CP ₂ Mg were introduced at 4 × 10 ^-8 mol / min for 1 minute to form a p ⁺ second contact layer 73 of magnesium (Mg) doped GaN having a thickness of about 5 nm. . The magnesium concentration of the second contact layer 73 is 1 × 10 ²⁰ / cm ³ . In this state, the second contact layer 73 is still an insulator having a resistivity of 10 ⁸ Ωcm or more.

Next, the second contact layer 73, the first contact layer 72, and the cladding layer 7 are formed using an electron beam irradiation apparatus.
1 was uniformly irradiated with an electron beam. Electron beam irradiation conditions are: acceleration voltage about 10KV, data current 1μA, beam moving speed 0.2m
m / sec, beam diameter 60 μmφ, vacuum degree 5.0 × 10 ⁻⁵ Torr. By the irradiation of the electron beam, the second contact layer 73,
The first contact layer 72 and the cladding layer 71 have a hole concentration of 6 × 10 ¹⁷ / cm ³ , 3 × 10 ¹⁷ / cm ³ , 2 × 10 ¹⁷ / c, respectively.
It became a p-conduction type semiconductor having m ³ and resistivity of 2Ωcm, 1Ωcm, 0.7Ωcm. Thus, a wafer having a multilayer structure was obtained.

Next, as shown in FIG. 2, on the second contact layer 73, Ti is formed to a thickness of 2000.degree., And on the Ti layer, Ni is formed to a thickness of 9000.degree. A metal mask layer 11 of Ni was formed. Then, a photoresist 12 was applied on the metal mask layer 11. Then, by photolithography, as shown in FIG. 2, on the second contact layer 73, the photoresist 12 at the electrode formation site A ^′ for the high carrier concentration n ⁺ layer 3 was removed. next,
As shown in FIG. 3, the metal mask layer 11 not covered with the photoresist 12 was removed with an acidic etching solution.

Next, the second contact layer 73, the first contact layer 72, the cladding layer 71, the light emitting layer 5, and the n-layer 4 at portions not covered by the metal mask layer 11 are vacuumed to a degree of 0.
After dry-etching by supplying 04 Torr, high-frequency power of 0.44 W / cm ² and BCl ₃ gas at a rate of 10 ml / min, dry etching was performed with Ar. In this step, as shown in FIG. 4, a hole A for extracting an electrode from the high carrier concentration n ⁺ layer 3 was formed. After that, the metal mask layer 11 was removed.

Next, two layers of Ni / Au were uniformly deposited, and a transparent electrode 9 was formed on the second contact layer 73 through the application of a photoresist, a photolithography step, and an etching step. Then, Ni / Au is applied to a part of the transparent electrode 9.
Were deposited to form the pad 10. On the other hand, the electrode 8 was formed on the n ⁺ layer 3 by evaporating aluminum. Thereafter, the wafer processed as described above was cut into individual devices to obtain light emitting diodes having the structure shown in FIG.

The light emitting diode 100 having this structure emits yellow-green light having a peak wavelength of 570 nm from the first multiple quantum well 51, and emits light having a peak wavelength of 450 nm from the second multiple quantum well 52.
Emitted blue light. This light emission is represented by a point V and a point U in the chromaticity diagram shown in FIG. 4, and a straight line connecting the point V and the point U represents an equi-energy white point at coordinates (1/3, 1/3). Pass. That is, the chromaticity at point V and the chromaticity at point U are in a complementary color relationship. Therefore, white light emission can be obtained by mixing these two light emissions.

In order to obtain more precise white light emission,
By weighting the brightness of the V point emission and the brightness of the U point emission, V
What is necessary is just to design so that the average value of the chromaticity coordinates of the point and the chromaticity coordinates of the point U becomes the coordinates (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) chromaticity coordinates of point V, (x _U, y _U) chromaticity coordinates of the point U, M _V and MU are the lightness of light emission at point V and point _U , respectively.

The light emission intensity for determining the lightness depends on each well layer 51.
2. The thickness of each well layer 522 may be changed. In the case of a quantum well structure, the luminous efficiency is improved and the luminous intensity can be increased by making the thickness of the well layer thinner. As described above, by changing the mixed crystal ratio of the first multiple quantum well 51, the chromaticity coordinates of the point V can be changed, and by changing the mixed crystal ratio of the second multiple quantum well 52, U The chromaticity coordinates of a point can be changed. Therefore, the mixed crystal ratios of the chromaticity coordinates and brightness of the light emission of the first multiple quantum well 51 and the chromaticity coordinates and brightness of the light emission of the second multiple quantum well 52 satisfy the above equation (1). By controlling the thickness and the thickness, pure white light emission can be obtained.

In the above embodiment, the light emission wavelength is short.
That is, the second multiple quantum well 52 having a wide bandgap has a long emission wavelength, that is, the first multiple quantum well 51 having a narrow bandgap.
Than on the light extraction surface (transparent electrode 9) side. Therefore, light having a long wavelength of 570 nm is emitted outside without being absorbed by the second multiple quantum well, so that the light extraction efficiency can be increased.

In the above embodiment, the emission wavelength is 450 nm
Although it is set to 0 nm, pure white light can be obtained even in combination with other wavelengths if the relationship of the above equation 1 is satisfied. Further, by determining the mixed crystal ratio and the thickness of the first multiple quantum well 51 and the second multiple quantum well 52 such that the left side of the equation 1 becomes equal to the chromaticity coordinates of the light to be obtained,
Light of a desired chromaticity can be obtained.

Furthermore, three or more multiple quantum wells may be provided. For example, as shown in FIG. 5, a first multiple quantum well, a second multiple quantum well, and a third multiple quantum well that emit light of chromaticity T, chromaticity R, and chromaticity S are formed from the side close to the substrate 1 By providing the light, light of an arbitrary chromaticity existing inside the triangle TRS can be obtained. In this case, the chromaticity coordinates of the light desired to obtain (x _O, y _O), chromaticity T, chromaticity R, the coordinates and brightness of chromaticity S, _{respectively, (x T, y T)} , (x _R, y _R ), (
_{x S, y S), M} T, M R, if M _S, so as to satisfy the following equation, the chromaticity of the light emitting points may be set brightness.

[0039]

[Number 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 )

[0040] Incidentally, luminance I _T of the emissions at each point, I _R, when the _{I S, M T = I T} / y T, M R = I R / y R, M S =
It is also I _S / y _S. About the synthesis of this light,
explain. In FIG. 6, the light emitting layer 5 has a well layer of In _0.5 G
a _0.5 N first multiple quantum well 51 with well layer of In _0.46 Ga _0.54
It is assumed that the second multiple quantum well 52 of N 2 and the third multiple quantum well 53 of In _0.43 Ga _0.57 N are formed in the well layer. At this time, the first multiple quantum well 51 emits light having a peak wavelength of 510 nm, the second multiple quantum well 52 emits light having a peak wavelength of 500 nm, and the third multiple quantum well 53 emits light having a peak wavelength of 490 nm. As shown. By combining these lights, light having a broad spectrum can be obtained as shown in FIG. That is, light close to pure white can be obtained.

Further, by changing the mixed crystal ratio of each well layer and changing the thickness of the well layer, light having a wavelength intensity characteristic as shown in FIG. 8 can be emitted from each well layer. it can. This combined light exhibits the wavelength intensity characteristics shown in FIG. 8, and can provide a more equal-energy white color.

In the above embodiment, multiple quantum wells are used to obtain light emission of each chromaticity coordinate. However, a single quantum well may be used. That is, the light emitting layer 5 may be configured with a quantum well structure in which the mixed crystal ratio is changed for each well layer. In the above embodiment, the well layer and the barrier layer are formed of an InGaN semiconductor, but the general formula (Al _x Ga _1-X ) _y In _1-y N (0 ≦ x1; 0 ≦ y ≦ 1)
The well layer and the barrier layer may be formed of a semiconductor satisfying the above conditions.

Further, in the above embodiment, the well layer is doped with no impurities. However, a donor impurity such as silicon, an acceptor impurity such as zinc, and other elements of the second, fourth and sixth groups are added as impurities. Is also good. Further, both a donor impurity and an acceptor impurity may be added to the well layer. For example, as shown in FIG. 9, the light emitting layer 5 is made of (Al _x Ga _{1 -X} ) _y In _{1 -y} N
And the well layer 552 and the barrier layer 551, and the well layer 5
52, silicon and zinc, 1 × 10 ¹⁷ to 1 ×, respectively
It may be added in the range of 10 ²⁰ / cm ³ .

As shown in FIG. 10, a barrier layer 561 is formed.
Is not added, and the well layer 562 contains a donor impurity (eg, silicon) and an acceptor impurity (eg, zinc).
May be added alternately. Further, as shown in FIG. 11, a donor impurity (for example, silicon) is added to the well layer 572.
, An acceptor impurity (for example, zinc) may be added to the barrier layer 571, or conversely, an acceptor impurity may be added to the well layer 572 and a donor impurity may be added to the barrier layer 571. These characteristics relating to the impurity distribution can change the emission wavelength together with the mixed crystal ratio of the well layer and the barrier layer. The well layer and the barrier layer may be n-type, p-type, or semi-insulating.

In the above embodiment, a sapphire substrate is used, but SiC, MgAl ₂ O ₄ or the like can be used. Although AlN is used for the buffer layer, AlGaN, GaN, InAlGaN, or the like can be used. Further, the n layer 4, but with GaN, it is possible to use a group III nitride semiconductor such as _{In x Ga y Al 1-xy} N. Similarly, the cladding layer 71, the first contact layer 72, and the second contact layer 73 also have an arbitrary composition ratio of In _x G
A group 3 nitride semiconductor such as a _y Al _1-xy N can be used.

Although the contact layer has a two-layer structure, it may have a one-layer structure. The thickness of the cladding layer 71 is preferably 2 nm to 70 nm, the thickness of the first contact layer 72 is preferably 2 nm to 100 nm, and the thickness of the second contact layer 73 is preferably 2 nm to 50 nm. If the thickness of the cladding layer 71 is smaller than 2 nm, the effect of confining carriers is reduced and the luminous efficiency is reduced, which is not desirable. When the thickness of the first contact layer 72 is smaller than 2 nm,
Since the number of holes to be injected is reduced, the luminous efficiency is reduced, which is not desirable. If the second contact layer 73 is thinner than 2 nm, the ohmic property becomes poor and the contact resistance increases, which is not desirable. On the other hand, when the thickness of each layer exceeds the above upper limit thickness, the time during which the light emitting layer is exposed to a temperature higher than its growth temperature becomes longer, and the effect of improving the crystallinity of the light emitting layer is not desirable.

The hole concentration of the cladding layer 71 is 1 × 10
¹⁷ to 1 × 10 ¹⁸ / cm ³ is desirable. Hall concentration 1 × 10 ¹⁸
/ Cm ³ or more and becomes undesirable since crystallinity becomes higher impurity concentration is lowered luminous efficiency decreases, 1 × 10 ¹⁷ /
If it is less than cm ³ , the series resistance becomes too high, which is not desirable.

The first contact layer 72 is made of magnesium (M
g) is added at a concentration lower than the magnesium (Mg) concentration of the second contact layer 73 in the range of 1 × 10 ^{19 to} 5 × 10 ²⁰ / cm ³ to form a layer exhibiting the p-conduction type, so that the hole of the layer is formed. The concentration can be an area including the maximum value of 3 × 10 ¹⁷ to 8 × 10 ¹⁷ / cm ³ . Thus, the luminous efficiency does not decrease.

The second contact layer 73 is made of magnesium (M
g) It is desirable that the concentration be 1 × 10 ²⁰ to 1 × 10 ²¹ / cm ³ . Magnesium (Mg) is 1 × 10 ²⁰ -1 × 10 ²¹ /
The p-type layer added to the cm ³ layer can improve the ohmic property of the metal electrode, but the hole concentration is slightly reduced to 1 × 10 ¹⁷ to 8 × 10 ¹⁷ / cm ³ . (The Mg concentration is preferably in the above range from the viewpoint of improving ohmic properties, including the range in which the driving voltage can be reduced to 5 V or less.)

[Brief description of the 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 sectional view showing a manufacturing process of the light-emitting diode of the embodiment.

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

FIG. 4 is an explanatory diagram showing the synthesis of chromaticity of the light emitting diode of the embodiment.

FIG. 5 is an explanatory diagram showing the synthesis of chromaticity of a light emitting diode according to another embodiment.

FIG. 6 is an explanatory view showing a quantum well structure of a light emitting diode according to another embodiment and a synthesis of wavelength intensity characteristics of light emitted from each well layer.

FIG. 7 is an explanatory diagram showing light synthesis in wavelength intensity characteristics of light emitted from each well layer of a light emitting diode according to another embodiment.

FIG. 8 is an explanatory diagram showing light synthesis in wavelength intensity characteristics from each well layer of a light emitting diode according to another embodiment.

FIG. 9 is a cross-sectional view illustrating a configuration of a light emitting layer of a light emitting diode according to another embodiment.

FIG. 10 is a cross-sectional view illustrating a configuration of a light emitting layer of a light emitting diode according to another embodiment.

FIG. 11 is a cross-sectional view illustrating a configuration of a light emitting layer of a light emitting diode according to another embodiment.

[Explanation of symbols]

REFERENCE SIGNS LIST 100 light emitting diode 1 sapphire substrate 2 buffer layer 3 high carrier concentration n ⁺ layer 4 n layer 5 light emitting layer 51 first multiple quantum well 52 second multiple quantum well 53 third third quantum well 512 , 522, 552, 562, 572 well layer 511, 521, 551, 561, 571 barrier layer 71 cladding layer 72 first contact layer 72 second contact layer 9 transparent electrode

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Shinya Asami 1 Ochiai Nagahata, Kasuga-cho, Nishi-Kasugai-gun, Aichi Prefecture Inside Toyoda Gosei Co., Ltd. No. 1 Toyoda Gosei Co., Ltd.

Claims (10)

[Claims] In a light emitting device having a multiple quantum well structure using a group III nitride semiconductor, a wavelength intensity of a combined light of light emitted from each well layer is changed by changing a mixed crystal ratio of a plurality of light emitting well layers. 3. The characteristic is a desired characteristic.
Group nitride semiconductor light emitting device. 2. The group III nitride semiconductor light emitting device according to claim 1, wherein the intensity of light emitted from each of the well layers is controlled by the thickness of the well layer. 3. The composition ratio of each well layer that emits light,
3. The group III nitride according to claim 1, wherein on the xy chromaticity diagram, the average value of the chromaticity coordinates of the light emission of each well layer is set to a ratio so as to be a desired coordinate. 4. Semiconductor light emitting device. 4. The group III nitride semiconductor light emitting device according to claim 3, wherein said average value is an average value weighted by lightness of light emission from each of said well layers. 5. The group III nitride semiconductor according to claim 3, wherein the desired coordinates are approximately the coordinates (1/3, 1/3) of equi-energy white light. Light emitting element. 6. The mixed crystal ratio of at least two light emitting well layers is such that the chromaticity coordinates of light emission of each well layer are two points that have complementary colors on the xy chromaticity diagram. The group III nitride semiconductor light emitting device according to claim 1, wherein: 7. The mixed crystal ratio of each of the plurality of well layers is set such that the sum of the wavelength intensity characteristics of light emitted from each of the well layers becomes the wavelength intensity characteristic of white light. The group III nitride semiconductor light emitting device according to claim 1 or 2, wherein: 8. A method according to claim 1, wherein the plurality of well layers have a mixed crystal ratio such that a forbidden band width is widened from a side near a light extraction surface. 3. A group III nitride semiconductor light-emitting device according to item 1. 9. The group III nitride semiconductor is (Al _x Ga _1-X ) _y In _1-y
9. The group III nitride semiconductor light emitting device according to claim 1, wherein N (0.ltoreq.x.ltoreq.1; 0.ltoreq.y.ltoreq.1). 10. In addition to the change in the mixed crystal ratio of each well layer,
The chromaticity of light emitted from each well layer is changed by adding an acceptor impurity or / and / or a donor impurity to each of the well layers or / and the barrier layers while changing its type and / or concentration. The group III nitride semiconductor light emitting device according to claim 1, wherein