JP3394678B2 - Semiconductor light emitting device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light emitting device such as a light emitting diode (LED) and a laser diode (LD), and particularly to a III-V group nitride having high luminous efficiency, long life and stable wavelength. The present invention relates to a semiconductor light emitting device having a semiconductor as a light emitting layer.

[0002]

2. Description of the Related Art III-V group nitride semiconductors, particularly nitride semiconductors containing indium (In) (In _A Al _B Ga).
_1-AB N, 0 ≦ A, 0 ≦ B, A + B ≦ 1) is used as a light emitting layer, and a semiconductor light emitting element is an LE that emits light from an ultraviolet color to a red color.
It is expected as a material for light emitting devices such as D and LD, and is under development.

FIG. 9 is a schematic sectional view of a conventional example of a semiconductor light emitting device using a nitride-based semiconductor material.
No. 528, title of invention: nitride semiconductor light emitting device, applicant: Nichia Corporation. In FIG. 9, an n-type gallium nitride-based compound semiconductor layer and a p-type gallium nitride-based compound semiconductor layer are stacked on an insulating substrate 60 such as a sapphire substrate, and a buffer layer 61, an n-type contact layer 62, and a N-type clad layer 63, first n-type clad layer 64, active layer 65, first p-type clad layer 66,
Second p-type cladding layer 67 and p-type contact layer 6
8 has a structure in which the n-type contact layer 62 is sequentially stacked.
A negative electrode 69 is formed on the p-type contact layer 68, and a positive electrode 70 is formed on the p-type contact layer 68.

The material setting of the active layer 65 and the n-type or p-type clad layer disposed on both sides of the active layer 65 is characteristic, and the first n-type cladding layer 64 has a thermal expansion coefficient smaller than that of the active layer 65. And the first p-type cladding layer 66 has
Since the active layer 65 has a thermal expansion coefficient smaller than that of the active layer 65 and has the single quantum well structure or the multiple quantum well structure, the energy is lower than the original bandgap energy of the nitride semiconductor forming the active layer. The nitride semiconductor light emitting device is characterized in that the light is emitted.

FIG. 10 shows the relationship between the active layer 65 of the above-mentioned conventional example and the emission peak wavelength. Specifically, the thickness of the active layer of the single-quantum well structure, that is, the thickness of the quantum well layer, is shown. FIG. 3 is a diagram showing a relationship with a light emission peak wavelength of a light emitting element. In FIG. 10, the line α indicates that the active layer is non-doped In
_A light emitting element made of _0.05 Ga _0.95 N is shown, and a line β shows a light emitting element having an active layer made of non-doped In _0.3 Ga _0.7 N. Both of the light emitting devices have a double hetero structure in which a second cladding layer, a first n-type cladding layer, an active layer, a first p-type cladding layer, and a second p-type cladding layer are sequentially stacked. Is. The second n-type cladding layer is 0.1
1 μm of Si-doped n-type Al _0.3 Ga _0.7 N,
The n-type cladding layer 500 Å In _0.01
Ga _0.99 N, the first p-type cladding layer is 20 Å of Mg-doped p-type In _0.01 Ga _0.99 N, and the second p-type cladding layer is 0.1 μm of Mg-doped p-type Al _0.3 Ga _0.7 N. It is a double hetero structure. Thus, it is shown that the emission wavelength changes when the film thickness of the active layer is changed.

The In _0.05 Ga _0.95 N active layer shown by the line α is
With the original bandgap energy, it emits ultraviolet light in the vicinity of 380 nm.
The wavelength can be lengthened to near m, and violet emission can be obtained. The In _0.3 Ga _0.7 N active layer indicated by the line β emits blue-green light near 480 nm in the original band gap energy, but pure green light emission near 520 nm is obtained by reducing the film thickness.

By thus reducing the thickness of the active layer sandwiched between the first n-type cladding layer and the first p-type cladding layer, the emission wavelength can be made longer. In other words, a normal active layer having a large film thickness only emits light corresponding to the bandgap energy of the active layer, but in the conventional active layer having a single-quantum well structure, it is necessary to reduce the film thickness of the well layer. As a result, the band gap energy becomes small, and it becomes possible to emit light having energy lower than the band gap energy of the original well layer, that is, long wavelength. Moreover, because it is non-doped, it has better crystallinity than that doped with impurities, so the output is high,
Furthermore, light emission with good color purity with a narrow half width is obtained by light emission between bands.

When the active layer is formed of thick InGaN, the crystallinity of the active layer is poor. For example, when the In composition ratio is 0.3 to 0.5, the crystallinity is poor and the light emission output is very low. However, the use of a thin film also has the effect of enabling growth with good crystallinity even with a large In composition ratio. In the above conventional example, the quantum well layer has a film thickness of 100 angstroms or less, more preferably 70 angstroms or less.
It is said that it is preferably formed so as to have a thickness of less than angstrom.

Further, in the above conventional example, the non-doped I
n ( _0.05 Ga _0.95 N) active layer, If (forward current) =
At 20 mA, Vf (forward voltage) = 3.5 V, emission peak wavelength λp = 410 nm (blue emission), emission output Wp =
The emission spectrum was 5 mW, and the full width at half maximum of the emission spectrum was Δλ = 20 nm.

Further, in the above conventional example, the non-doped I
If (forward current) = 2 using n _0.2 Ga _0.8 N active layer
At 0 mA, Vf (forward voltage) = 3.5 V, emission peak wavelength λp = 465 nm (blue emission), emission output Wp = 5
The emission spectrum was mW and the full width at half maximum of the emission spectrum was Δλ = 25 nm.

Further, in the above conventional example, the non-doped I
n ( _0.3 Ga _0.7 N) active layer, If (forward current) = 2
At 0 mA, Vf (forward voltage) = 3.5 V, emission peak wavelength λp = 500 nm (green emission), emission output Wp = 3
The emission spectrum was mW and the half-width of the emission spectrum was Δλ = 40 nm.

Further, in the above-mentioned conventional example, an active layer having a single quantum well structure made of In _0.4 Ga _0.6 N of 70 Å is used, and Vf is set at If (forward current) = 20 mA.
(Forward voltage) = 3.5 V, emission peak wavelength λp = 52
The emission power was 5 nm (green emission), the emission output Wp was 4 mW, and the full width at half maximum of the emission spectrum was Δλ = 40 nm.

[0013]

In the conventional nitride-based light emitting device, the In composition ratio must be increased in order to obtain blue-green, green, and yellow-green light-emitting devices. However, InGaN mixed crystal or InGaA
When a light emitting layer made of a 1N mixed crystal material is used, as described above, when the composition ratio of In becomes large, for example, a ternary mixed crystal of InGaN is likely to cause phase separation, and thus, in the InGaN layer in the quantum well of the light emitting layer. That the quantum dots are naturally formed in a region larger than the In composition set in
Since the light emission from the light emitting layer of the GaN quantum well structure is considered to be excitonic light emission localized in the quantum dots, it is difficult to obtain a semiconductor light emitting device having a uniform emission wavelength within the wafer surface. . Further, strain relaxation occurs due to lattice mismatch in the light emitting layer due to generation of quantum dots, and In
Strain relaxation occurs due to the lattice mismatch between the GaN layer and the other semiconductor layer, and non-radiative recombination resulting from them is increased,
At present, only light-emitting elements with low luminous efficiency and short lifetime are obtained. Further, the dependence of the emission wavelength on the injection current is large, and it is currently difficult to obtain a light emitting element with a stable emission wavelength.

Further, the conventional example described in Japanese Patent Laid-Open No. 8-316.
In Japanese Patent No. 528, the thickness of the active layer (light emitting layer) is 7
Although it is described that 0 angstroms or less is desirable, the value according to the embodiment is for the active layer having a film thickness of 70 angstroms. From the above description, this film thickness is a film in which quantum dots are generated. It can be assumed to be thick.

[0015]

The semiconductor light emitting device according to claim 1, wherein the SUMMARY OF THE INVENTION The present invention is a semiconductor light emitting element according to the light-emitting layer III-V nitride semiconductor, light emitting layer be a multiple quantum well structure The unit quantum well layer constituting the multiple quantum well structure has a layer thickness of 3 to 10 atomic layers ,
The composition ratio of In of the group III element contained in the child well layer is 35
% To 65%, forming a multiple quantum well structure
The barrier layer to be In _X Ga _1-X N (0.35 ≦ X ≦ 0.6
5) is a feature.

According to a second aspect of the present invention, there is provided a semiconductor light emitting device, which is a semiconductor device having a III-V group nitride semiconductor as a light emitting layer.
In the body light emitting device, the light emitting layer has a multiple quantum well structure.
The unit quantum well layer that constitutes the multiple quantum well structure is
A unit quantum well layer having a layer thickness of 10 to 10 atomic layers
Or the composition ratio of In of the III group element is 35% or more contained in the
One is 65% or less, barriers constituting the multiple quantum well structure
It is characterized in that the layer is In _X Ga _1-X N (X ≦ 0.35) .

Further, in the semiconductor light emitting device according to the third aspect of the present invention, the light emitting layer has In _X Ga _{1 -X} N (0.35≤X≤0.
65).

Further, in the semiconductor light emitting device according to claim 4 of the present invention, the light emitting layer has In _X (Al _Y Ga _1-Y ) _1-X N (0 <Y
≦ 1.0, 0.35 ≦ X ≦ 0.65).

According to a fifth aspect of the present invention, there is provided a semiconductor light emitting device comprising a III-V group nitride semiconductor as a light emitting layer.
A body light emitting device, wherein the light emitting layer has a single semiconductor layer structure, a single
Quantum well structure or multiple quantum well structure, single semiconductor
Single semiconductor layer or single quantum well structure constituting the body layer structure
Unit quantum well layer forming a multi-quantum well structure
Has a layer thickness of 3 to 10 atomic layers, and a single semiconductor
The body layer or the unit quantum well layer is In _X (Al _Y Ga _1-Y ) _1-X
It is characterized in that N (0 <Y ≦ 1.0, 0.35 ≦ X ≦ 0.65) .

Further, in the semiconductor light emitting device according to claim 6 of the present invention, the light emitting layer has a multiple quantum well structure, and the barrier layer constituting the multiple quantum well structure is In _X Ga _{1 -X} N (0.35 ≦
X ≦ 0.65) .

Further, the semiconductor light-emitting device according to claim 7 of the present invention, the light emitting layer is a multiple quantum well structure, In the group III element contained in the barrier layer constituting the multiple quantum well structure
The composition ratio of is characterized in that 35% or less.

Further, in the semiconductor light emitting device according to claim 8 of the present invention, the barrier layer constituting the multiple quantum well structure is In _X G
a _1−X N (X ≦ 0.35).

Further, the semiconductor light emitting device according to claim 9 of the present invention is a semiconductor light emitting device having a III-V group nitride semiconductor as a light emitting layer.
A conductor light emitting device, wherein the light emitting layer has a multiple quantum well structure.
The unit quantum well layer that constitutes the multiple quantum well structure is
A unit quantum well layer having a layer thickness of 10 to 10 atomic layers
The composition ratio of In of the group III element contained in is 35% or more
Is 65% or less, and the barrier layer forming the multiple quantum well structure is In _X (Al _Y Ga _1-Y ) _1-X N (0 <Y ≦ 1.0,
0.35 ≦ X ≦ 0.65 ) or multiple quantum wells
In of the group III element contained in the barrier layer forming the door structure
Is less than 35% (provided that the unit quantum well layer is In _0.35 Ga _0.65 N).
Excluding those) . Further, the semiconductor device according to claim 10 of the present invention
In the body light emitting device, the light emitting layer has In _X Ga _1-X N (0.35 ≦ X
≦ 0.65).

[0024]

1 to 8 are views showing a semiconductor light emitting device according to an embodiment of the present invention. Embodiments of the present invention will be described below.

[First Embodiment] FIG. 1 is a sectional view showing the structure of a semiconductor light emitting device according to the first embodiment of the present invention. The MOCVD method (metal organic chemical vapor deposition method) is used for the growth of the semiconductor light emitting device. TMG (trimethylgallium), TEG (triethylgallium), TMI (trimethylindium), TMA (trimethylaluminum), etc. are used as the group III element transport gas, and NH ₃ (ammonia) is used as the group V element transport gas. To use. SiH ₄ as n-type dopant transport gas
(Silane) is used, and Cp ₂ Mg (cyclopentadiethylmagnesium) or ethyl Cp ₂ Mg is used as a transport gas for the p-type dopant.

The sapphire C-plane substrate 1 was placed in a hydrogen atmosphere 11
After thermal cleaning at 00 ° C., the substrate temperature is lowered to 550 ° C. and a buffer layer 2 of non-doped AlN having a layer thickness of 50 nm is grown. Next, the substrate temperature is raised to 1050 ° C. to grow the Si-doped n-type GaN layer 3 having a layer thickness of 4 μm.
Next, the substrate temperature was lowered to 800 ° C., and the number of 6 atomic layers (calculated value: about 1.6 nm, that is, 16 angstrom) non-doped In _0.4 Ga _0.6 N light-emitting layer (single-semiconductor layer) 4; Doped p-type Al _0.2 Ga _0.8 N InGa
The N evaporation prevention layer 5 is sequentially grown. Next, the substrate temperature is set to 10
Mg-doped p-type G with a layer thickness of 0.5 μm after being raised to 50 ° C.
The aN layer 6 is grown. Subsequently, a part of the growth layer is etched until the Si-doped n-type GaN layer 3 is exposed,
The n-type electrode 7 is formed on the surface. Also, Mg-doped p
A p-type electrode 8 is deposited on the surface of the type GaN layer 6. Next, divide the wafer into chips (chip size about 400 μm square)
After mounting on the stem, resin molding is performed to obtain a semiconductor light emitting element (LED element).

FIG. 6 shows the result of measuring the ratio of the In composition and the light emitting area in the semiconductor light emitting device having the same layer structure as that of the schematic sectional view shown in FIG. In FIG. 6, when a non-doped In _X Ga _1-X N (0 ≦ X ≦ 1.0) semiconductor layer having a film thickness of about 5 nm (50 Å) is used as the light emitting layer and the In composition of the light emitting layer is changed, Low current drive (1
FIG. 6 shows the ratio of the light emitting area to the total area of the light emitting region in mA or less). In FIG. 6, the In composition X of the non-doped In _X Ga _{1 -X} N light emitting layer is X = 0.0 to
At 0.2 and X = 0.8 to 1.0, the ratio of the light emitting area is 0.92, which is almost constant, whereas at X = 0.2.
At ~ 0.8, the ratio of the light emitting area is greatly reduced,
When X = 0.4 to 0.6, the ratio of the light emitting area is 0.
It shows that the value is as low as 67.

The reason is that the In composition of the light emitting layer is 0.35 to 0.65 from TEM (transmission electron microscope) observation.
The density of the quantum dots increases due to the phase separation of the light emitting layer in the region of, and the In composition of the light emitting layer is 0 to 0.35 and 0.6.
It was found that the Ga or In composition becomes dominant in the region of 5 to 1.0 and the density of the quantum dots decreases conversely.

That is, the In composition of the light emitting layer is 0.35 to 0.
In the region 65, the increase in the density of the quantum dots causes the increase in misfit dislocations due to the difference in crystal composition in the light emitting layer. This misfit dislocation in the light emitting layer becomes the center of non-radiative recombination, which causes a decrease in the emission intensity of the device and a shortening of the life of the light emitting device.

Further, since the quantum dots in the light emitting layer described above are spontaneously formed during crystal growth, it is impossible to control the composition and size thereof. For this reason, the characteristic distribution of the light emitting elements taken out from one wafer becomes large, and for example, the phenomenon that the distribution of the emission wavelength becomes significantly large occurs. Generation of such quantum dots is caused by InGaA
In the case where 1N is used as the light emitting layer, the same In as shown in FIG.
A decrease (dependency) in the ratio of the light emitting area to the composition was observed.

Further, this quantum dot has a different shape and composition of In for each quantum dot.
The carriers injected for emitting light are distributed in a wide energy range in the entire light emitting layer. Moreover,
Since the mobility of carriers in InGaN or InGaAlN crystal is low and the relaxation time of carriers is long,
As for light emission, light emission occurs in a high energy state before the injected carriers relax to low energy. It has been found that, due to this cause, in the light emitting device having the InGaN or InGaAlN light emitting layer as the quantum well structure, the emission current has a large dependency on the injection current. This phenomenon becomes more remarkable as the In composition of the light emitting layer increases (that is, the emission wavelength becomes longer). For example, a green light emitting diode of InGaN quantum well structure (In composition ratio 0.4
(5, emission wavelength 520 nm), when the driving current is changed by 10 mA, the emission peak wavelength shifts to the short wavelength side by about 10 nm, and the color changes, and it is difficult to adjust the color in the application to full color display. There was a problem such as.

Further, the above-mentioned problem is that the light emitting layer has a single
It is also found in semiconductor layers or unit well layers or multiple quantum well structures. Here, the single-quantum well structure refers to a structure having a single quantum well layer. That is, the light emitting layer (active layer) having a single-quantum well structure is composed of only a single well layer. Further, the single-semiconductor layer is a light-emitting layer composed of a single-semiconductor layer, and also includes a light-emitting layer in which a quantum well structure is not formed. The multiple quantum well structure is a multilayer film structure in which quantum well layers and barrier layers are alternately laminated. In this multilayer film structure, the two outermost layers on both sides are each formed by a well layer. A possibly simple structure of the multiple quantum well structure is a case of quantum well layer / barrier layer / quantum well layer.

FIG. 7 shows InGaN or InGaAl.
When the thickness of the N light emitting layer is changed, the reduction ratio of the light emitting area with respect to the number of atomic layers (layer thickness) of the light emitting layer is shown. In FIG. 7, when the number of atomic layers of the light emitting layer is 1 to 5, the reduction ratio of the light emitting area is 0.08, and the number of atomic layers of the light emitting layer is 6 to 5.
With the number of 9 atomic layers, the reduction ratio of the light emitting area greatly increases,
0.08 to 0.24, and the number of atomic layers in the light emitting layer is 10
With the number of 15 atomic layers, the reduction ratio of the light emitting area was 0.24, while it was still increasing. As a result, it is shown that the reduction ratio of the light emitting area is small in the region where the thickness of the light emitting layer is 9 atomic layers or less. In other words, it is shown that by reducing the thickness of the light emitting layer, generation of quantum dots is suppressed, non-radiative recombination is reduced, and a bright semiconductor light emitting device can be obtained. Therefore, it can be said that the layer thickness of the light emitting layer for obtaining a practical semiconductor light emitting element is 1 atomic layer to 15 atomic layers, and preferably 3 atomic layer to 10 atomic layers.

FIG. 8 shows light emission using In _X (Al _0.02 Ga _0.98 ) _1-X N, which is a semiconductor light emitting device according to one embodiment of the present invention, as a parameter with the In composition ratio of a light emitting device having a light emitting layer. The relation between the layer thickness (the number of atomic layers) and the emission intensity of the semiconductor light emitting device is shown. The structure of the semiconductor light emitting device is the same as the schematic cross-sectional view shown in FIG. In _X (Al _0.02 G
a _0.98 ) _1-X N In the case of the composition ratio X = 0.35 of the light emitting layer, the emission intensity of the device becomes maximum at the number of 7 atomic layers and the number of 8 atomic layers, and the In _X (Al _0.02 Ga _0.98 ) _1-X N Composition ratio X of light emitting layer
= 0.52, the emission intensity of the element is maximum in the number of 5 atomic layers, and when the composition ratio of the In _x (Al _0.02 Ga _0.98 ) _1-x N emission layer is X = 0.65, the emission intensity of the element is The maximum result was obtained with four atomic layers.

As shown in FIG. 8, the thickness of the light emitting layer is 1
The emission intensity increases as the number of atomic layers increases,
The emission intensity has a peak in the number of layers having a certain thickness, and when the number of layers is further increased, the emission intensity decreases conversely. This is because the carrier concentration in the light emitting layer increases and the light emission intensity increases as the layer thickness increases in a region where the thickness of the light emitting layer is thin. The strain generated in the light emitting layer due to the matching is relaxed, misfit dislocations occur, and the misfit dislocations become the center of non-radiative recombination, and the emission intensity sharply decreases. The layer thickness at which the emission intensity peaks is determined by the In composition of the emission layer (strain in the emission layer), and the layer thickness (the number of atomic layers) that maximizes the emission intensity becomes smaller as the In composition increases.

Explaining this phenomenon from the standpoint of whether or not quantum dots are generated, the film thickness of the light emitting layer until the emission intensity has a peak is a region where the quantum dots are not generated, and the emission intensity passes the peak. It can be explained that the film thickness of the light-emitting layer that decreases as a result is the region of the film thickness where the generation of quantum dots has started. Moreover, the generation of quantum dots is to be observed only in the unit well layer of the single-quantum well structure or the multiple quantum well structure.

In other words, as shown in FIG. 8, the present invention is a semiconductor light emitting device using a III-V group nitride semiconductor as a light emitting layer, wherein the light emitting layer has a single-semiconductor layer structure, a single quantum well structure, or a multiple quantum well structure. A semiconductor light-emitting device having a quantum well structure, wherein the single-semiconductor layer or the unit quantum well layer is composed of one atomic layer to 15 atomic layers. To reiterate, the single-semiconductor layer or the unit quantum well layer is characterized in that the layer thickness is composed of one atomic layer to 15 atomic layers. This is because there are cases where the quantum well layer is not formed in a very thin semiconductor layer having 15 to 15 atomic layers.

In FIG. 8 described above, In _X (Al _0.02 Ga)
_{Although the 0.98} ) _1-X N light emitting layer has been described as an example, the same result can be obtained for the In _X Ga _{1 -X} N light emitting layer and the In _X Ga _Y Al _{1 -XY} N light emitting layer.

In addition, the above-mentioned light-emitting layer (one atomic layer number or more 15
In the case of a multiple quantum well structure having a unit quantum well layer having a thickness equal to or less than the number of atomic layers), In _X Ga _1-X N or In _X Ga _Y Al having an In composition of 35% to 65% is also used.
_{In 1-XYN} , a bright semiconductor light emitting device can be obtained and the device characteristic distribution in the wafer can be reduced.

The LED element shown in FIG. 1 is the same as that shown in FIG.
This is a result based on the findings of FIGS. 7 and 8. In this case, the light emitting layer is a single-semiconductor layer (six atomic layers) of undoped In _0.4 G.
This is the result when the well layer 4 of a _0.6 N is selected and used. The LED element has a forward current If = 20 mA, a forward voltage Vf = 3.5 V, and an emission peak wavelength λp = 485 nm.
(Blue-green) and the light emission output Wp = 6 mW. The shift (change amount) of the emission peak wavelength λp when the forward current If is changed from 5 mA to 15 mA is 3 nm or less,
The distribution of the emission peak wavelength within the same wafer (2 inches φ) was 5 nm or less. The life of the current-carrying test of continuous 20 mA at room temperature was 2000 hours or more.

On the other hand, in the conventional example, the emission output is 4 mW, the peak wavelength shift is 5 nm, and the peak wavelength distribution is 10 n.
m, the life was 1000 hours. According to the present invention, the output is 1.5 times, the peak wavelength shift is 3/5, the peak wavelength distribution is reduced to 1/2, and the life is improved to more than twice.

[Second Embodiment] FIG. 2 shows a schematic cross-sectional view of a semiconductor light emitting device according to a second embodiment of the present invention. In this case, the gas source MBE method (molecular beam epitaxy method) is used for the growth of the semiconductor light emitting device. Ga metal, In metal, and Al metal are used as the group III molecular beam source, and NH ₃ or a nitrogen radical generated by decomposition of nitrogen gas is used as the group V molecular beam source. RF (Radi
o Frequency) plasma, ECR (Elec
Tron Cyclotron Resonance) plasma or thermal cracking techniques are used. Si is used as the n-type dopant and Mg is used as the p-type dopant.

After the sapphire A-side substrate 9 was thermally cleaned at 850 ° C. in a nitrogen radical atmosphere, the substrate temperature was raised to 5
The temperature is lowered to 00 ° C. and a buffer layer 10 of undoped GaN having a layer thickness of 30 nm is grown. Next, the substrate temperature is raised to 700 ° C., the Si-doped n-type GaN layer 11 having a layer thickness of 2 μm, and the number of two atomic layers of non-doped In _0.6 (Ga _0.97 Al _0.03 ) _0.4 N
Quantum well layer 12 and three atomic layers of undoped In _0.4
With the Ga _0.6 N barrier layer 13, the period number 4 (quantum well layer ×
4, a light emitting layer 14 having a multiple quantum well structure of a barrier layer × 3) and a Mg-doped p-type GaN layer 15 having a layer thickness of 0.5 μm are sequentially grown. Next, a part of the growth layer is used as a Si-doped n-type GaN layer 1
Etching is performed until 1 is exposed, an n-type electrode 16 is formed on the surface thereof, and a p-type electrode 17 is deposited on the surface of the Mg-doped p-type GaN layer 15. Next, the wafer is divided into chips and resin-molded to obtain LED elements.

This LED element has a forward current If = 20 m.
A, forward voltage Vf = 4.0 V, emission peak wavelength λp
= 550 nm (yellowish green), and the emission output Wp = 4 mW. When the forward current If is changed from 10 mA to 20 mA, the shift (change amount) of the emission peak wavelength λp is 4n.
m or less, and the distribution of the emission peak wavelength within the same wafer (2 inches φ) was 7 nm or less. Room temperature continuous 2
The life of the 0 mA electrification test was 1000 hours or more. In the conventional example, the emission output is 3 mW, the peak wavelength shift is 10 nm, the peak wavelength distribution is 20 nm, and the lifetime is 50 nm.
It was 0 hours. According to the present invention, the output is 1.3 times, the peak wavelength shift is 2/5, the peak wavelength distribution is reduced to 1/3, and the life is more than doubled.

[Third Embodiment] FIG. 3 is a schematic cross-sectional view of a semiconductor light emitting device according to a third embodiment of the present invention. In this case, the MOCVD method (metal organic chemical vapor deposition method) is used to grow the semiconductor light emitting device. TMG (trimethylgallium), TEG (triethylgallium), TMI (trimethylgallium), and TMA (trimethylaluminum) are used as a group III element transport gas.
NH ₃ (ammonia) is used as a transport gas for group V elements. SiH ₄ (silane) is used as a transport gas for the n-type dopant and Cp ₂ Mg (cyclopentadiethylmagnesium) or ethyl C is used as a transport gas for the p-type dopant.
Use p ₂ Mg.

115 n-type SiC substrate 18 in a hydrogen atmosphere
After thermal cleaning at 0 ° C., the substrate temperature is lowered to 600 ° C., and the buffer layer 19 of undoped AlN having a layer thickness of 40 nm is formed.
Grow. Next, the substrate temperature was raised to 1100 ° C., the Si-doped n-type GaN layer 20 having a layer thickness of 4 μm, and the layer thickness of 50 nm.
Si-doped n-type Al _0.1 Ga _0.9 N cladding layer 21 is sequentially grown. Next, the substrate temperature is lowered to 750 ° C., and the emission layer (single-quantum well structure) 22 of four-atom layers of Si-doped n-type In _0.65 Ga _0.35 N and the Mg-doped p-type Al _0.1 Ga _0.9 N clad with a layer thickness of 50 nm. Layer 23 is grown sequentially.

Next, the substrate temperature is raised to 1050 ° C. to grow the Mg-doped p-type GaN layer 24 having a layer thickness of 0.5 μm. Next, etching is performed until the Si-doped n-type GaN layer 20 is exposed, a part of the etching is further performed on the AlN buffer layer 19, and etching is performed until the n-type SiC substrate 18 is exposed. The back surface of the n-type SiC substrate 18 and the n-type SiC substrate 18 and Si exposed by etching
N so as to electrically connect to the doped n-type GaN layer 20.
The mold electrode 25 is deposited, and the p-type electrode 26 is deposited on the surface of the Mg-doped p-type GaN layer 24. Next, the wafer is divided into chips and resin-molded to obtain LED elements.

This LED element has a forward current If = 20 m.
A, forward voltage Vf = 4.0 V, emission peak wavelength λp
= 570 nm (yellow), and the emission output Wp = 2 mW. The shift (change amount) of the emission peak wavelength λp when the forward current If is changed from 10 mA to 20 mA is 5 n.
m or less, and the peak wavelength distribution within the same wafer was 10 nm or less. The service life of the continuous current test of 20 mA at room temperature was 1,000 hours or more. In the conventional example, the emission output was 1 mW, the peak wavelength shift was 20 nm, the peak wavelength distribution was 30 nm, and the life was 500 hours. According to the present invention, the output is doubled, the peak wavelength shift is reduced to 1/4, the peak wavelength distribution is reduced to 1/3, and the life is improved to more than double.

[Fourth Embodiment] FIG. 4 is a schematic cross-sectional view of a semiconductor light emitting device according to a fourth embodiment of the present invention. In this case, the MOCVD method (metal organic chemical vapor deposition method) is used to grow the semiconductor light emitting device. TMG (trimethylgallium), TEG (triethylgallium), TMI (trimethylindium), and TMA (trimethylaluminum) are used as a group III element transport gas.
NH ₃ (ammonia) is used as a transport gas for group V elements. SiH ₄ (silane) is used as a transport gas for the n-type dopant and Cp ₂ Mg (cyclopentadiethylmagnesium) or ethyl C is used as a transport gas for the p-type dopant.
Use p ₂ Mg.

The n-type SiC substrate 28 is set to 800 in a hydrogen atmosphere.
After thermal cleaning at ℃, the substrate temperature is lowered to 550 ℃, and a GaN buffer layer 29 having a layer thickness of 25 nm is grown. Next, the substrate temperature is raised to 1050 ° C., the Si-doped n-type GaN layer 30 having a layer thickness of 4 μm, the Si-doped n-type Al _0.1 Ga _0.9 N cladding layer 31 having a layer thickness of 0.5 μm, and the layer thickness of 0.1.
A μm Si-doped GaN light guide layer 32 is sequentially grown. Next, the substrate temperature is lowered to 850 ° C., and the quantum well layer 33 of 7 atomic layers of non-doped In _0.52 Ga _0.48 N and the layer thickness 3 are formed.
nm non-doped In _0.15 (Ga _0.95 Al _0.05 ) _0.85 N
And the barrier layer 34 of the multi-quantum well structure having a period number of 3 (quantum well layer × 3, barrier layer × 2), and a layer thickness of 50 nm.
The Mg-doped p-type Al _0.2 Ga _0.8 N InGaN evaporation prevention layer 36 is sequentially grown. Next, the substrate temperature is 1050 ° C
The Mg-doped GaN optical guide layer 37 having a layer thickness of 0.1 μm and the Mg-doped p-type Al _0.1 Ga having a layer thickness of 0.5 μm.
_0.9 N cladding layer 38, 0.5 μm Mg-doped p-type G
The aN layer 39 is grown. Next, Si-doped n-type GaN
Etching is performed until the layer 30, the GaN buffer layer 29, and the n-type SiC substrate 28 are exposed, the n-type electrode 40 is vapor-deposited on the surface thereof, and the p-type electrode 41 is vapor-deposited on the surface of the Mg-doped p-type GaN 39. Next, a cavity having a length of 1 mm was produced by cleavage and divided into chips to obtain a semiconductor laser device. This semiconductor laser device oscillates at room temperature with a threshold current of 100 mA (maximum output 5 mW) and has an oscillation wavelength of 520 n.
It was m green.

[Fifth Embodiment] FIG. 5 shows a schematic cross-sectional view of a semiconductor light-emitting device according to a fifth embodiment of the present invention. In this case, the gas source MBE method (molecular beam epitaxy method) is used for the growth of the semiconductor light emitting device. Ga metal, In metal, and Al metal are used as the group III molecular beam source, and NH ₃ or a nitrogen radical generated by decomposition of nitrogen gas is used as the group V molecular beam source. RF (Radi
o Frequency) plasma, ECR (Elec
Tron Cyclotron Resonance) plasma or thermal cracking techniques are used. Si is used as the n-type dopant and Mg is used as the p-type dopant.

After heat-cleaning the n-type GaN substrate 42 at 900 ° C. in a nitrogen radical atmosphere, the substrate temperature is set to 700.
Si-doped n-type GaN layer 4 having a layer thickness of 2 μm after being lowered to ℃
3. Si-doped n-type Al _0.1 Ga _0.9 N with a layer thickness of 0.5 μm
Cladding layer 44, Si-doped GaN optical guide layer 45 with a layer thickness of 50 nm, and 5 atomic layers of non-doped In _0.35 Ga _0.65
An N light emitting layer (single-quantum well structure) 46 is sequentially grown. Next, a Mg-doped GaN optical guide layer 4 having a layer thickness of 50 nm
7. Mg-doped p-type Al _0.1 Ga _0.9 N with a layer thickness of 0.5 μm
Clad layer 48, Mg-doped p-type Ga having a layer thickness of 0.5 μm
The N layer 49 is grown. Next, the Mg-doped p-type GaN layer 49 and the Mg-doped p-type Al _0.1 Ga _0.9 N cladding layer 4
A part of 8 is etched to form a 5 μm wide lid waveguide. Next, a silicon nitride film (Si ₃ N ₄ ) insulating film 5
Form 0. The insulating film 50 of the silicon nitride film (Si ₃ N ₄ ) on the lid stripe portion is removed. The back surface of the n-type GaN substrate 42 is polished. Next, the n-type electrode 51 is vapor-deposited on the back surface of the n-type GaN layer 42, and the p-type electrode 52 is vapor-deposited on the surface of the Mg-doped p-type GaN layer 49 in the lid stripe portion. Next, a 1 mm resonator is produced by cleavage and divided into chips to obtain a semiconductor laser device.

This semiconductor laser device has a threshold current of 50 m.
A, continuous oscillation at room temperature with an oscillation wavelength of 470 nm and an output of 1.5 mW at room temperature had a life of 50 hours. When the drive current was changed from 50 mA to 100 mA, the shift of the oscillation wavelength was 0.5 nm or less, and the distribution of the oscillation wavelength on the same wafer was 5 nm or less. In the conventional example, the threshold current was 80 mA, the life was 27 hours, and the peak shift of the oscillation wavelength was 5 nm. According to the present invention, the drive current can be reduced, and a device having a long life and a stable oscillation wavelength can be realized.

[0054]

As described above, the III-V group nitride semiconductor
In a semiconductor light emitting device having a body as a light emitting layer,
As shown in FIG.
With a layer thickness of up to 10 atomic layers, the generation of quantum dots can be reduced and non-radiative recombination can be reduced. Furthermore, the thinning of the light emitting layer does not cause strain relaxation due to the difference in lattice constant with other layers and the substrate, and non-radiative recombination can be reduced. As a result, it is possible to obtain a semiconductor light emitting device of blue, blue-green, green, and yellow-green that has a uniform emission wavelength within the wafer surface, has a small dependency of the emission wavelength on the injection current, has high emission efficiency, and has a long life. it can.

[0055]

[0056]

[0057]

[0058]

[0059]

[0060]

[0061]

[0062]

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a semiconductor light emitting device that is a first embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view of a semiconductor light emitting device that is a second embodiment of the present invention.

FIG. 3 is a schematic cross-sectional view of a semiconductor light emitting device that is a third embodiment of the present invention.

FIG. 4 is a schematic cross-sectional view of a semiconductor light emitting device that is a fourth embodiment of the present invention.

FIG. 5 is a schematic cross-sectional view of a semiconductor light emitting device that is a fifth embodiment of the present invention.

FIG. 6 shows a semiconductor light emitting device according to an embodiment of the present invention, which uses a non-doped In _X Ga _{1 -X} N light emitting layer having a film thickness of about 5 nm and changes the In composition of the light emitting layer. It is a figure which shows the ratio of the light emission area at the time of low current drive with respect to the whole area.

FIG. 7 is a diagram showing changes in the reduction ratio of the light emitting area with respect to the number of atomic layers in the light emitting layer In _x Ga _{1 -x} N in the semiconductor light emitting device according to the embodiment of the present invention.

FIG. 8 relates to a semiconductor light emitting device according to an embodiment of the present invention, in which In _X (Al _0.02 Ga _0.98 ) _1-X N is used as a parameter with the In composition ratio of the light emitting device having a light emitting layer as a parameter. The relationship between the number of layers and the emission intensity of the device is shown.

FIG. 9 is a schematic cross-sectional view of a semiconductor light emitting device using a conventional nitride-based semiconductor material.

FIG. 10 is a diagram showing a relationship between the thickness of an active layer and an emission peak wavelength in a semiconductor light emitting device using a nitride-based semiconductor material of a conventional example.

[Explanation of symbols]

1 Sapphire C-plane substrate 2 50 nm thick non-doped AlN buffer layer 3 4 μm thick Si-doped n-type GaN layer 4 6 atomic layer non-doped In _0.4 Ga _0.6 N single-semiconductor layer (light emitting layer) 5 50 nm thick layer Mg-doped p-type Al _0.2 Ga _0.8 N InGaN evaporation prevention layer 6 Mg-doped p-type GaN layer with a layer thickness of 0.5 μm 7 n-type electrode 8 p-type electrode 9 sapphire A-side substrate 10 GaN buffer layer with a layer thickness of 30 nm 11 Si-doped n-type GaN layer 12 having a layer thickness of 2 μm 12 Non-doped In _0.6 Ga _0.4 N quantum well layer 13 2 atomic layer non-doped In _0.4 Ga _0.6 N barrier layer 14 Period number 4 (well layer × 4, barrier Layer × 3) light-emitting layer 15 having a multiple quantum well structure 15 Mg-doped p-type GaN layer 16 having a layer thickness of 0.5 μm n-type electrode 17 p-type electrode 18 n-type SiC substrate 19 non-layer having a layer thickness of 40 nm Of Si-doped n-type GaN layer 21 thickness 50nm of the buffer layer 20 thickness 4μm of flop AlN Si-doped n-type Al _0.1 Ga _0.9 N
Cladding layer 22 4 atomic layer Si-doped n-type In _0.65 Ga _0.35 N quantum well layer (single-semiconductor layer) 23 Mg-doped p-type Al _0.1 Ga _0.9 N with a layer thickness of 50 nm
Clad layer 24 Mg-doped p-type GaN layer 25 with a thickness of 0.5 μm n-type electrode 26 p-type electrode 28 n-type SiC substrate 29 GaN buffer layer with a thickness of 30 nm 30 Si-doped n-type GaN layer 31 with a thickness of 4 μm Si-doped n-type Al _0.1 Ga _{0.9 with a} thickness of 0.5 μm
N cladding layer 32 Si-doped GaN optical guide layer 33 having a thickness of 0.1 μm 7 7 atomic layer non-doped In _0.52 Ga _0.48 N quantum well layer 34 Non-doped In _0.15 (Ga _0.95 Al) having a thickness of 3 nm
_0.05 ) _0.85 N barrier layer 35 Multi-quantum well structure light emitting layer 36 with period number 3 (quantum well layer × 3, barrier layer × 2) Mg-doped p-type Al _0.2 Ga _0.8 N with a layer thickness of 50 nm
InGaN evaporation prevention layer 37, Mg-doped GaN optical guide layer 38 having a layer thickness of 0.1 μm, and Mg-doped p-type Al _0.1 Ga _{0.9 having a} layer thickness of 0.5 μm.
N-clad layer 39 0.5 μm Mg-doped p-type GaN layer 40 n-type electrode 41 p-type electrode 42 n-type GaN substrate 43 Si-doped n-type GaN layer 44 having a layer thickness of 2 μm Si-doped n-type Al having a layer thickness of 0.5 μm _0.1 Ga _0.9
N-clad layer 45 Si-doped GaN light guide layer 46 with a thickness of 50 nm 5 Atomic layer non-doped In _0.35 Ga _0.65 N light-emitting layer (single-quantum well layer) 47 Mg-doped GaN light guide layer with a thickness of 50 nm 48 Layer thickness 0 0.5 μm Mg-doped p-type Al _0.1 Ga _0.9
N-clad layer 48 Mg-doped p-type Al _0.1 Ga _0.9 N-clad layer 49 0.5-μm-thick Mg-doped p-type GaN layer 50 Silicon nitride film (Si ₃ N ₄ ) insulating film 51 n-type electrode 52 p-type electrode

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshiyuki Okumura 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (56) References JP-A-9-36430 (JP, A) JP-A-10- 65271 (JP, A) JP 10-32348 (JP, A) JP 9-307188 (JP, A) JP 9-162444 (JP, A) JP 9-129922 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01L 33/00 H01S 5/00-5/50 JISST file (JOIS)

Claims (10)

(57) [Claims] 1. A semiconductor light emitting device having a III-V group nitride semiconductor as a light emitting layer, wherein the light emitting layer has a multiple quantum well structure, and the unit quantum well layer forming the multiple quantum well structure has three atomic layers. To 10 atomic layers , the unit quantum well layer
The composition ratio of In of the group III element contained in is 35% or more
Is 65% or less, and the barrier layer constituting the multiple quantum well structure is In _x Ga _{1 -x}
A semiconductor light emitting device, wherein N (0.35 ≦ X ≦ 0.65) . 2. A III-V group nitride semiconductor is used as a light emitting layer.
In the semiconductor light emitting device according to the first aspect, the light emitting layer has a multiple quantum well structure, and the unit quantum well layer forming the multiple quantum well structure has three sources.
A unit quantum well layer having a layer thickness of 10 to 10 atomic layers
Or the composition ratio of In of the III group element is 35% or more contained in the
One is 65% or less, the barrier layer constituting the multiple quantum well structure is In _X Ga _1-X
A semiconductor light emitting device characterized by N (X ≦ 0.35) . 3. A semiconductor light emitting device according to claim 1 or claim 2, wherein the light emitting layer is _{In X Ga 1-X N (} 0.35 ≦ X ≦ 0.6
5) A semiconductor light emitting device characterized in that 4. The method of claim 1 or the semiconductor light emitting device according to claim 2, wherein the light emitting layer is _{In X (Al Y Ga 1-} Y) 1-X N (0 <Y ≦
1.0, 0.35 ≦ X ≦ 0.65). 5.A Group III-V nitride semiconductor is used as a light emitting layer.
RuIn the semiconductor light emitting device,The light emitting layer has a single semiconductor layer structure, a single quantum well structure or
Is a multiple quantum well structure, Or a single semiconductor layer forming the single semiconductor layer structure
Forming a single quantum well structure or a multiple quantum well structure
The unit quantum well layer has a thickness of 3 to 10 atomic layers.
And the single semiconductor layer or unit quantum well layer is In
_X (Al _Y Ga _1-Y ) _1-X N (0 <Y ≦ 1.0, 0.35 ≦
X ≦ 0.65) A semiconductor light-emitting element characterized by
Child. 6. A semiconductor light emitting device according to claim 5, wherein said light emitting layer is a multiple quantum well structure, the barrier layer constituting the multiple quantum well structure is In _X Ga _1-X
A semiconductor light emitting device characterized by N (0.35 ≦ X ≦ 0.65) . In the semiconductor light emitting device of claim 7 according to claim 5, wherein the light emitting layer is a multiple quantum well structure includes the barrier layers constituting the multiple quantum well structure II
The semiconductor light emitting element composition ratio of In of the Group I element is equal to or less than 35%. 8. The semiconductor light emitting device according to claim 7, wherein the barrier layer forming the multiple quantum well structure is In _X Ga _{1 -X.}
A semiconductor light emitting device characterized by N (X ≦ 0.35). 9. A III-V nitride semiconductor is used as a light emitting layer.
In the semiconductor light emitting device according to the first aspect, the light emitting layer has a multiple quantum well structure, and the unit quantum well layer forming the multiple quantum well structure has three sources.
A unit quantum well layer having a layer thickness of 10 to 10 atomic layers
The composition ratio of In of the group III element contained in is 35% or more
One is 65% or less, the barrier layer constituting the multiple quantum well structure In _X (Al _Y
Ga _1-Y ) _1-X N (0 <Y ≦ 1.0, 0.35 ≦ X ≦ 0.
65 ) or constitutes the multiple quantum well structure
The composition ratio of In of the group III element contained in the barrier layer is 35
% Or less semiconductor light-emitting device (only
And the unit quantum well layer is In _0.35 Ga _0.65 N
Excluding) . 10. The semiconductor light emitting device according to claim 9.
hand, The light emitting layer is In _X Ga _1-X N (0.35 ≦ X ≦ 0.6
5) is that Semiconductor light emitting device.