JPH10229217A - Semiconductor light emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the production of quantum dot and the no-light emitting recoupling, by a method wherein a single semiconductor layer is formed light emitting layer, and the thickness of the single semiconductor with the structure of a layer is composed of atomic layer number within a specific range. SOLUTION: After thermally cleaning a sapphire C surface substrate 1 in a hydrogen atmosphere, an AlN buffer layer 2 in thickness of 50nm is grown further by growing an Si doped n type GaN layer 3 on the buffer layer 2. Next, a single semiconductor layer 4 as a light emitting layer composed of one atomic layer number or 15 atomic layer number in film thickness is grown on the surface of the Si doped GaN layer 3 further growing an InGaN evaporation preventive layer 5 on the layer 4. Successively, an Mg doped p type GaN layer 6 is grown on the layer 5 so that a part of the layer 6 may be etched away until the Si doped n type GaN layer 3 is exposed, so as to form an n type electrode 7 on the surface of the layer 3. Furthermore, a p type electrode 8 is deposited on the Mg doped GaN layer 6.

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 more particularly, to a group III-V nitride having high luminous efficiency, long life and stable wavelength. The present invention relates to a semiconductor light emitting element having a semiconductor as a light emitting layer.

[0002]

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

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 laminated on an insulating substrate 60 such as a sapphire substrate, and a buffer layer 61, an n-type contact layer 62, 2, an n-type clad layer 63, a first n-type clad layer 64, an active layer 65, a first p-type clad layer 66,
Second p-type cladding layer 67 and p-type contact layer 6
8 are sequentially laminated, and the n-type contact layer 62
A positive electrode 70 is formed on the p-type contact layer 68.

[0004] The material of the active layer 65 and the n-type or p-type clad layers disposed on both sides of the active layer 65 is characterized in that the first n-type clad layer 64 has a smaller thermal expansion coefficient than the active layer 65. And the first p-type cladding layer 66 has
By having a thermal expansion coefficient smaller than that of the active layer 65 and making the active layer 65 a single quantum well structure or a multiple quantum well structure, the energy lower than the original band gap energy of the nitride semiconductor constituting the active layer can be obtained. This is a nitride semiconductor light emitting device characterized in that it emits light of the following type.

FIG. 10 shows the relationship between the active layer 65 of the prior art and the emission peak wavelength. More specifically, the thickness of the active layer having a single-quantum well structure, that is, the thickness of the quantum well layer and the thickness of the active layer 65 are shown in FIG. FIG. 4 is a diagram showing a relationship between a light emission element and a light emission peak wavelength. In FIG. 10, 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 whose active layer is made of non-doped In _0.3 Ga _0.7 N. In both cases, the structure of the light emitting element is a double hetero structure in which a second clad layer, a first n-type clad layer, an active layer, a first p-type clad layer, and a second p-type clad layer are sequentially stacked. It is. The second n-type cladding layer is 0.1
μm Si-doped n-type Al _0.3 Ga _0.7 N
The n-type cladding layer is 500 angstroms of In _0.01.
Ga _0.99 N, the first p-type cladding layer is made of 20 Å of Mg-doped p-type In _0.01 Ga _0.99 N, and the second p-type cladding layer is made of 0.1 μm of Mg-doped p-type Al _0.3 Ga _0.7 N. It has a double heterostructure. Thus, it is shown that changing the thickness of the active layer changes the emission wavelength.

The In _0.05 Ga _0.95 N active layer shown by the line α is
It emits ultraviolet light at around 380 nm at the original band gap energy, but it becomes 420 n
It can emit blue-violet light by increasing the wavelength to near m. The In _0.3 Ga _0.7 N active layer indicated by the line β emits blue-green light at around 480 nm in the original band gap energy, but pure green light at around 520 nm is obtained by reducing the film thickness similarly.

As described above, by 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, an ordinary active layer having a large thickness only emits light corresponding to the band gap energy of the active layer. However, in the active layer having the single-quantum well structure of the conventional example, it is necessary to reduce the thickness of the well layer. As a result, the band gap energy is reduced, and light having a lower energy than the band gap energy of the original well layer, that is, light having a longer wavelength can be emitted. Moreover, since it is non-doped, its crystallinity is better than that doped with impurities, so the output becomes higher,
In addition, light emission with a narrow half width and good color purity is obtained by light emission between bands.

Further, 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, there is also an effect that the thin film can be grown with good crystallinity even at a large In composition ratio. In the above conventional example, the thickness of the quantum well layer is 100 Å or less, more preferably 70 Å or less.
It is preferable that the film be formed to have a thickness of Å or less.

In the above conventional example, the non-doped I
Using an 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 =
5 mW, and the half width of the emission spectrum Δλ = 20 nm.

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

In the above conventional example, the non-doped I
Using an 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
mW and the half width of the emission spectrum Δλ = 40 nm.

In the above conventional example, an active layer having a single quantum well structure made of 70 Å In _0.4 Ga _0.6 N is used. If (Forward current) = 20 mA, Vf
(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 half width of the emission spectrum Δλ was 40 nm.

[0013]

In the conventional nitride-based light emitting device, the composition ratio of In must be increased in order to obtain blue-green, green, and yellow-green light-emitting devices. However, InGaN mixed crystal system or InGaAs
When a light emitting layer made of an 1N mixed crystal material is used, as described above, if the composition ratio of In increases, for example, a ternary mixed crystal of InGaN easily causes phase separation, and the InGaN layer in the quantum well of the light emitting layer Is formed naturally in a region that is a region larger than the In composition set in
Since light emission from the light-emitting layer having a quantum well structure of GaN is considered to be exciton light emission localized in the quantum dots, it is difficult to obtain a semiconductor light-emitting device having a uniform light emission wavelength within the wafer surface. . In addition, strain relaxation due to lattice mismatch in the light emitting layer due to the generation of quantum dots occurs, and In
Relaxation of strain occurs due to lattice mismatch between the GaN layer and other semiconductor layers, resulting in increased non-radiative recombination,
At present, only light-emitting elements with low luminous efficiency and short lifetime have been obtained. In addition, it is difficult to obtain a light-emitting device having a stable emission wavelength because the emission wavelength has a large dependency on an injection current.

[0014] Further, the above-mentioned prior art disclosed in Japanese Patent Application Laid-Open No. 8-316 is disclosed.
In JP-A-528, the thickness of the active layer (light-emitting layer) is 7
Although it is described that the thickness is preferably 0 Å or less, the value according to the embodiment is a description of an active layer having a thickness of 70 Å. It can be assumed that it is thick.

[0015]

According to a first aspect of the present invention, there is provided a semiconductor light emitting device having a III-V nitride semiconductor as a light emitting layer, wherein the light emitting layer has a single-semiconductor layer structure or a single semiconductor layer structure. It has a single quantum well structure or a multiple quantum well structure, and a single-semiconductor layer or a unit quantum well layer has a thickness of 1
It is characterized by being constituted by the number of atomic layers to the number of 15 atomic layers.

In a semiconductor light emitting device according to a second aspect of the present invention, the composition of the single-semiconductor layer or the unit quantum well layer constituting the light emitting layer is such that the composition ratio of In which is a group III element is 35% or more. And 65% or less.

Further, in the semiconductor light emitting device according to the third aspect of the present invention, the light emitting layer is formed of In _x Ga ₁ -xN (0.35 ≦ X ≦ 0.
65).

Moreover, the semiconductor light-emitting device according to claim 4 of the present invention, the light emitting layer is _{In X (Al Y Ga 1-} Y) 1-X N (0 <Y
≦ 1.0, 0.35 ≦ X ≦ 0.65).

Further, in the semiconductor light emitting device according to the fifth aspect of the present invention, the barrier layer constituting the multiple quantum well structure is formed of In _x G
a _1−X N (0.35 ≦ X ≦ 0.65).

In a semiconductor light emitting device according to a sixth aspect of the present invention, the barrier layer forming the multiple quantum well structure has an In barrier.
_X (Al _Y Ga _1-Y ) _1-X N (0 <Y ≦ 1.0, 0.35 ≦
X ≦ 0.65).

In a semiconductor light emitting device according to a seventh aspect of the present invention, the composition of the barrier layer forming the multiple quantum well structure is I
It is characterized in that the composition ratio of In which is a Group II element is 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 formed of In _x G
a _1−X N (X ≦ 0.35).

Further, in the semiconductor light emitting device according to the ninth aspect of the present invention, the barrier layer constituting the multiple quantum well structure is formed of In _x.
(Al _Y Ga _1-Y ) _1-X N (0 <Y ≦ 1.0, X ≦ 0.3
5).

[0024]

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

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

The sapphire C-plane substrate 1 is placed in a hydrogen atmosphere at 11
After thermal cleaning at 00 ° C., the substrate temperature is lowered to 550 ° C., and a non-doped AlN buffer layer 2 having a thickness of 50 nm is grown. Next, the substrate temperature is raised to 1050 ° C. to grow a 4 μm-thick Si-doped n-type GaN layer 3.
Next, the substrate temperature was lowered to 800 ° C., and the number of non-doped In _0.4 Ga _0.6 N light-emitting layers (single-semiconductor layers) 4 of 6 atomic layers (calculated value of about 1.6 nm, that is, 16 Å), and 50-nm thick Mg layers InGa doped p-type Al _0.2 Ga _0.8 N
The N evaporation preventing layer 5 is sequentially grown. Next, set the substrate temperature to 10
Raise the temperature up to 50 ° C and make the Mg-doped p-type G
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,
An 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 p-type GaN layer 6. Next, the wafer is divided into chips (chip size of about 400 μm square)
Then, 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 composition of In to the light emitting area in the semiconductor light emitting device having the same layer structure as the schematic sectional view shown in FIG. In FIG. 6, when a semiconductor layer of non-doped In _x Ga ₁ -xN (0 ≦ X ≦ 1.0) having a 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 at (mA or less). In FIG. 6, the In composition X of the non-doped In _x Ga ₁ -xN light emitting layer is from X = 0.0 to 0.0.
In the case of 0.2 and X = 0.8 to 1.0, the ratio of the light emitting area is almost constant at 0.92, while the ratio of 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 0.1.
This indicates that the value is as low as about 67.

The reason for this is that the TEM (transmission electron microscope) observation shows that the In composition of the light emitting layer is 0.35 to 0.65.
That the density of the quantum dots due to the phase separation of the light emitting layer is increased in the region of
It has been found that in the range of 5 to 1.0, the Ga or In composition becomes dominant, and the density of the quantum dots is reduced.

That is, when the In composition of the light emitting layer is 0.35 to 0.5.
In the region 65, an increase in the density of quantum dots causes an increase in misfit dislocation due to a difference in crystal composition in the light emitting layer. The misfit dislocation in the light emitting layer becomes a center of non-radiative recombination, and thus causes a reduction in light emission intensity of the element and a shortened life of the light emitting element.

Further, since the above-mentioned quantum dots of the light emitting layer are spontaneously formed during crystal growth, it is impossible to control the composition and size thereof. For this reason, the distribution of the characteristics 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 extremely large occurs. The generation of such quantum dots is caused by InGaAs
In the case where 1N is used as the light emitting layer, In is similar to that shown in FIG.
A decrease (dependency) in the ratio of the light emitting area to the composition was observed.

Further, since this quantum dot has a different shape and different In composition for each quantum dot,
Carriers injected for light emission are distributed over a wide energy range in the entire light emitting layer. Moreover,
Since the mobility of carriers in the InGaN or InGaAlN crystal is low and the relaxation time of the carriers is long,
Light emission occurs in a high energy state before the injected carriers relax to low energy. For this reason, it has been found that in a light emitting device having a quantum well structure of an InGaN or InGaAlN light emitting layer, the emission current has a large dependence on the injection current. This phenomenon becomes more remarkable as the In composition of the light emitting layer becomes larger (that is, as the emission wavelength becomes longer). For example, a green light emitting diode having a quantum well structure of InGaN (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 shorter wavelength side by about 10 nm, and the color changes. In the case of application to a full-color display, the color adjustment becomes difficult. There was such a problem.

The above-mentioned problem is caused by the fact that the light-emitting layer has a simple structure.
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 the single-quantum well structure is composed of only the single-well layer. Further, the single-semiconductor layer is a light-emitting layer composed of a single-semiconductor layer, and includes a light-emitting layer in which a quantum well structure is not formed. The multiple quantum well structure is a multilayer structure in which quantum well layers and barrier layers are alternately stacked. In this multilayer structure, the two outermost layers on both sides are each formed of a well layer. The simplest structure of the multiple quantum well structure is the case of a 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 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 atomic layers, 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 atomic layers.
In the case of 9 atomic layers, the decrease ratio of the light emitting area greatly increases,
0.08 to 0.24, and the number of atomic layers of the light emitting layer is 10 to 10.
With 15 atomic layers, the reduction ratio of the light emitting area was increased to 0.24. As a result, it is shown that in a region where the thickness of the light emitting layer is 9 atomic layers or less, the reduction ratio of the light emitting area is small. In other words, it is shown that by reducing the thickness of the light emitting layer, the generation of quantum dots is suppressed, and a bright semiconductor light emitting device with less non-radiative recombination 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 to 15 atomic layers, preferably 3 to 10 atomic layers.

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

As shown in FIG. 8, the thickness of the light emitting layer is 1
As the thickness becomes larger than the number of atomic layers, the emission intensity increases,
The emission intensity has a peak in the number of layers having a certain film thickness, and when the number of layers is further increased, the emission intensity conversely decreases. This is because in a region where the thickness of the light-emitting layer is small, as the layer thickness increases, the carrier concentration in the light-emitting layer increases and the light emission intensity increases. Distortion in the light emitting layer caused by the matching is alleviated, and misfit dislocations are generated. The misfit dislocations become the center of non-radiative recombination, and the light emission intensity sharply decreases. The layer thickness at which the emission intensity shows a peak is determined by the In composition (strain in the emission layer) of the emission layer. As the In composition increases, the layer thickness (the number of atomic layers) at which the emission intensity becomes maximum decreases.

To explain this phenomenon from the viewpoint of the occurrence of quantum dots, the 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 thickness of the light-emitting layer, which is reduced by the reduction, is a region of the thickness at which the generation of quantum dots starts. Further, generation of quantum dots is observed only in the unit well layer having a single-quantum well structure or a multiple quantum well structure.

In other words, as shown in FIG. 8, the present invention relates to a semiconductor light emitting device using a III-V 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 multi-layer structure. A semiconductor light emitting device having a quantum well structure, wherein a single-semiconductor layer or a unit quantum well layer has a layer thickness of 1 to 15 atomic layers. To reiterate, it is described in parallel that the single-semiconductor layer or the unit quantum well layer has a layer thickness of 1 to 15 atomic layers in parallel. This is because there is a case where a quantum well layer is not formed in a very thin semiconductor layer having a number of layers to 15 atomic layers.

In FIG. 8, In _x (Al _0.02 Ga
_0.98) has been described _1-X N light-emitting layer as an example, this phenomenon In _X Ga _1-X N light-emitting layer and _{In X Ga Y Al 1-XY} N light-emitting layer Similar results are obtained.

In addition, the above-mentioned light-emitting layer (at least 15 atomic layers or more)
In the case of a multi-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 -xN or In _x Ga _Y Al with an In composition of 35% to 65%.
_{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.
The results are based on the findings of FIGS. 7 and 8, in which the light emitting layer is a non-doped In _0.4 G single-semiconductor layer (six atomic layers).
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. When the forward current If is changed from 5 mA to 15 mA, the shift (change amount) of the emission peak wavelength λp is 3 nm or less;
The distribution of the emission peak wavelength in the same wafer (2 inches φ) was 5 nm or less. The life of the continuous current test at 20 mA at room temperature was 2,000 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 distribution of the peak wavelength is 10 nW.
m, and the life was 1000 hours. According to the present invention, the output is reduced 1.5 times, the peak wavelength shift is reduced to 3/5, the distribution of the peak wavelength is reduced to 1/2, and the life is improved more than 2 times.

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

After the sapphire A-side substrate 9 is thermally cleaned at 850 ° C. in a nitrogen radical atmosphere, the substrate temperature is reduced to 5 ° C.
The temperature is lowered to 00 ° C., and a non-doped GaN buffer layer 10 having a layer thickness of 30 nm is grown. Next, the substrate temperature was raised to 700 ° C., and the Si-doped n-type GaN layer 11 having a thickness of 2 μm and the non-doped In _0.6 (Ga _0.97 Al _0.03 ) _0.4 N having two atomic layers were used.
Quantum well layer 12 and three atomic layers of non-doped In _0.4
With the Ga _0.6 N barrier layer 13, the period number is 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 replaced with 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, 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 molding is performed 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 (yellow-green), and the light 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, 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 energization test was 1000 hours or more. In the conventional example, the light 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 reduced to 2/5, the distribution of the peak wavelength is reduced to 1/3, and the life is improved more than twice.

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

The n-type SiC substrate 18 is placed in a hydrogen atmosphere for 115
After thermal cleaning at 0 ° C., the substrate temperature was lowered to 600 ° C., and a non-doped AlN buffer layer 19 having a layer thickness of 40 nm was formed.
Grow. Next, the substrate temperature was increased to 1100 ° C., and the Si-doped n-type GaN layer 20 having a layer thickness of 4 μm and the
The Si-doped n-type Al _0.1 Ga _0.9 N cladding layer 21 is sequentially grown. Next, the substrate temperature was lowered to 750 ° C., and the number of light-emitting layers (single-quantum well structure) 22 of Si-doped n-type In _0.65 Ga _0.35 N with four atomic layers, and Mg-doped p-type Al _0.1 Ga _0.9 N clad with a 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 thickness of 0.5 μm. Next, etching is performed until the Si-doped n-type GaN layer 20 is exposed, and a part of the etching is further performed on the AlN buffer layer 19 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
N so as to electrically connect the doped n-type GaN layer 20
A type electrode 25 is deposited, and a 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 molding is performed 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 emission output Wp = 2 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 5n.
m, and the distribution of peak wavelengths within the same wafer was 10 nm or less. The life of a 20 mA continuous conduction test at room temperature was 1000 hours or more. In the conventional example, the light 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 more than 2 times.

[Fourth Embodiment] FIG. 4 is a schematic sectional view of a semiconductor light emitting device according to a fourth embodiment of the present invention. In this case, a semiconductor light emitting device is grown by MOCVD (metal organic chemical vapor deposition). Using TMG (trimethylgallium), TEG (triethylgallium), TMI (trimethylindium), and TMA (trimethylaluminum) 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 an n-type dopant, and Cp ₂ Mg (cyclopentadiethylmagnesium) or ethyl C is used as a transport gas for a p-type dopant.
Use p ₂ Mg.

The n-type SiC substrate 28 is placed in a hydrogen atmosphere at 800
After thermal cleaning at ℃, the substrate temperature is lowered to 550 ° C., and a GaN buffer layer 29 having a thickness of 25 nm is grown. Next, the substrate temperature was raised to 1050 ° C., and the Si-doped n-type GaN layer 30 having a thickness of 4 μm, the Si-doped n-type Al _0.1 Ga _0.9 N cladding layer 31 having a thickness of 0.5 μm, and the layer thickness of 0.1
A μm Si-doped GaN optical guide layer 32 is sequentially grown. Next, the substrate temperature was lowered to 850 ° C., and the number of non-doped In _0.52 Ga _0.48 N quantum well layers 33 of 7 atomic layers and the layer thickness of 3
nm non-doped In _0.15 (Ga _0.95 Al _0.05 ) _0.85 N
, A light emitting layer 35 having a multiple quantum well structure having a period number of 3 (quantum well layer × 3, barrier layer × 2), and a layer thickness of 50 nm.
Sequentially growing a Mg-doped p-type Al _0.2 Ga _0.8 N of the InGaN evaporation prevention layer 36. Next, the substrate temperature is set to 1050 ° C.
The Mg-doped GaN optical guide layer 37 has a thickness of 0.1 μm, and the Mg-doped p-type Al _0.1 Ga has a thickness of 0.5 μm.
_0.9 N cladding layer 38, 0.5 μm Mg-doped p-type G
An 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, an n-type electrode 40 is deposited on the surface thereof, and a p-type electrode 41 is deposited on the surface of the Mg-doped p-type GaN 39. Next, a cavity having a length of 1 mm was formed by cleavage and divided into chips to obtain a semiconductor laser device. This semiconductor laser device performs room-temperature pulse oscillation (maximum output: 5 mW) at a threshold current of 100 mA, and has an oscillation wavelength of 520 n.
m was green.

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

After the n-type GaN substrate 42 is thermally cleaned at 900 ° C. in a nitrogen radical atmosphere,
Temperature 2 ° C. and a 2 μm thick Si-doped n-type GaN layer 4
3. 0.5 μm thick Si-doped n-type Al _0.1 Ga _0.9 N
Clad layer 44, Si-doped GaN optical guide layer 45 having a thickness of 50 nm, and non-doped In _0.35 Ga _0.65 having 5 atomic layers
An N light emitting layer (single-quantum well structure) 46 is sequentially grown. Next, an 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
Cladding layer 48, Mg-doped p-type Ga having a thickness of 0.5 μm
An 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 clad layer 4
8 is etched to form a 5 μm wide lid waveguide. Next, an insulating film 5 of a silicon nitride film (Si ₃ N ₄ )
0 is formed. The insulating film 50 of the silicon nitride film (Si ₃ N ₄ ) on the ridge stripe is removed. The back surface of the n-type GaN substrate 42 is polished. Next, an n-type electrode 51 is deposited on the back surface of the n-type GaN layer 42, and a p-type electrode 52 is deposited on the surface of the Mg-doped p-type GaN layer 49 in the lip stripe portion. Next, a 1 mm resonator is formed by cleavage and divided into chips to form a semiconductor laser device.

This semiconductor laser device has a threshold current of 50 m.
A, The continuous oscillation at room temperature was performed at an oscillation wavelength of 470 nm, and the life at room temperature with an output of 1.5 mW was 50 hours. When the driving current was changed from 50 mA to 100 mA, the oscillation wavelength shift was 0.5 nm or less, and the oscillation wavelength distribution 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, a drive current can be reduced, and a device having a long lifetime and a stable oscillation wavelength can be realized.

[0054]

As described above, according to the semiconductor light emitting device of the first aspect of the present invention, the semiconductor light emitting device has a III-V nitride semiconductor as a light emitting layer, and the light emitting layer is a single-semiconductor layer. Or a single quantum well structure or a multiple quantum well structure, and the single-semiconductor layer or the unit quantum well layer has a thickness of 1 to 15 atomic layers. In addition, generation of quantum dots is reduced, and non-radiative recombination can be reduced. Furthermore, the thinning of the light emitting layer does not cause relaxation of distortion due to a difference in lattice constant between the other layers and the substrate, and can reduce non-radiative recombination. As a result, it is possible to obtain blue, blue-green, green, and yellow-green semiconductor light-emitting elements having a uniform emission wavelength in the wafer surface, a small emission current dependence on the injection current, a high emission efficiency, and a long life. it can.

According to the semiconductor light emitting device of the second aspect of the present invention, the composition of the single semiconductor layer or the unit quantum well layer constituting the light emitting layer is such that the composition ratio of In which is a group III element is 35%. This is not less than 65%, and the generation of quantum dots is reduced and the non-radiative recombination can be reduced by reducing the thickness of the light emitting layer regardless of the composition ratio of In. .

According to the semiconductor light emitting device of the third aspect of the present invention, the light emitting layer is made of In _x Ga ₁ -xN (0.35 ≦ X
≦ 0.65), the generation of quantum dots in the light emitting layer In _x Ga ₁ -xN is reduced, and non-radiative recombination can be reduced. Furthermore, the thinning of the light emitting layer does not cause relaxation of distortion due to a difference in lattice constant between the other layers and the substrate, and can reduce non-radiative recombination. As a result, blue-green, green, and yellow-green semiconductor light-emitting elements having a uniform emission wavelength in the wafer surface, a small dependence of the emission wavelength on the injection current, a high emission efficiency, and a long life can be obtained.

According to the semiconductor light emitting device of the fourth aspect of the present invention, the light emitting layer is made of In _x (Al _Y Ga _{1 -Y} ) ₁ -XN.
(0 <Y ≦ 1.0, 0.35 ≦ X ≦ 0.65), and the light-emitting layer In _x (Al _Y Ga
_1-Y ) Generation of _1-XN quantum dots is reduced, and non-radiative recombination can be reduced.

Further, according to the semiconductor light emitting device of the fifth aspect of the present invention, the barrier layer forming the multiple quantum well structure has
and characterized in that a _{n X Ga 1-X N (} 0.35 ≦ X ≦ 0.65), can be by the quantum effect, improve the luminous efficiency.

According to the semiconductor light emitting device of the sixth aspect of the present invention, the barrier layer forming the multiple quantum well structure has
_{n X (Al Y Ga 1-} Y) 1-X N (0 <Y ≦ 1.0,0.35
≤ X ≤ 0.65),
The luminous efficiency can be improved by the effective function of the barrier layer.

According to the semiconductor light emitting device of the present invention, the composition of the barrier layer constituting the multiple quantum well structure is such that the composition ratio of In which is a group III element is 35% or less. The luminous efficiency can be improved by the effective function of the barrier layer and the quantum effect.

According to the semiconductor light emitting device of the eighth aspect of the present invention, the barrier layer constituting the multiple quantum well structure has
It is characterized by n _x Ga ₁ -xN (X ≦ 0.35), and the luminous efficiency can be improved by the effective function of the barrier layer and the quantum effect.

Further, according to the semiconductor light emitting device of the ninth aspect of the present invention, the barrier layer constituting the multiple quantum well structure is formed of In _x (Al _Y Ga _{1 -Y} ) ₁ -XN (0 <Y ≦ 1). , X ≦ 0.3
5), and the luminous efficiency can be improved by the effective function of the barrier layer and the quantum effect. As a result, blue-green, green, and yellow-green semiconductor light-emitting elements having a uniform emission wavelength in the wafer surface, a small dependence of the emission wavelength on the injection current, a high emission efficiency, and a long life can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a semiconductor light emitting device according to a first embodiment of the present invention.

FIG. 2 is a schematic sectional view of a semiconductor light emitting device according to a second embodiment of the present invention.

FIG. 3 is a schematic sectional view of a semiconductor light emitting device according to a third embodiment of the present invention.

FIG. 4 is a schematic sectional view of a semiconductor light emitting device according to a fourth embodiment of the present invention.

FIG. 5 is a schematic sectional view of a semiconductor light emitting device according to a fifth embodiment of the present invention.

FIG. 6 relates to a semiconductor light-emitting device according to an embodiment of the present invention, in which a light _- emitting layer of about 5 nm in thickness of non-doped In _x Ga ₁ -xN is used and the In composition of the light-emitting layer is changed. FIG. 4 is a diagram illustrating a ratio of a light emitting area at the time of low current driving to the entire area.

FIG. 7 is a diagram showing a change in a reduction ratio of a light emitting area with respect to the number of atomic layers of a light emitting layer In _x Ga ₁ -xN in a semiconductor light emitting device according to an embodiment of the present invention.

FIG. 8 relates to a semiconductor light-emitting device according to an embodiment of the present invention, wherein the composition ratio of In in a light-emitting device having a light-emitting layer of In _x (Al _0.02 Ga _0.98 ) _1-x N is used as a parameter, and 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 conventional semiconductor light emitting device using a nitride-based semiconductor material.

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

[Explanation of symbols]

REFERENCE SIGNS LIST 1 Sapphire C-plane substrate 2 Buffer layer of non-doped AlN having a thickness of 50 nm 3 Si-doped n-type GaN layer having a thickness of 4 μm 4 6-atomic layer Non-doped In _0.4 Ga _0.6 N single-semiconductor layer (light emitting layer) 5 Layer having a thickness of 50 nm Mg-doped p-type Al _0.2 Ga _0.8 N InGaN evaporation preventing layer 6 Mg-doped p-type GaN layer having a thickness of 0.5 μm 7 n-type electrode 8 p-type electrode 9 sapphire A-side substrate 10 GaN buffer layer having a thickness of 30 nm 11 Si-doped n-type GaN layer having a thickness of 2 μm 12 Non-doped In _0.6 Ga _0.4 N quantum well layer of two atomic layers 13 Non-doped In _0.4 Ga _0.6 N barrier layer of three atomic layers 14 Period number 4 (well layer × 4, barrier Light-emitting layer having a multiple quantum well structure of layer × 3) 15 Mg-doped p-type GaN layer having a thickness of 0.5 μm 16 n-type electrode 17 p-type electrode 18 n-type SiC substrate 19 layer thickness 40 Si-doped n-type Al a Si-doped n-type GaN layer 21 thickness 50nm of the buffer layer 20 thickness 4μm of undoped AlN of m _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 50 nm thick
Cladding layer 24 Mg-doped p-type GaN layer having a thickness of 0.5 μm 25 n-type electrode 26 p-type electrode 28 n-type SiC substrate 29 GaN buffer layer having a thickness of 30 nm 30 Si-doped n-type GaN layer 31 having a thickness of 4 μm 31 layers 0.5 μm thick Si-doped n-type Al _0.1 Ga _0.9
N-clad layer 32 Si-doped GaN optical guide layer with a thickness of 0.1 μm 3 _Non- doped In _0.52 Ga _0.48 N quantum well layer with 7 atomic layers 34 Non-doped In _0.15 (Ga _0.95 Al with a thickness of 3 nm
_0.05 ) _0.85 N barrier layer 35 Light emitting layer having a multiple quantum well structure with 3 periods (quantum well layer × 3, barrier layer × 2) 36 Mg-doped p-type Al _0.2 Ga _0.8 N having a thickness of 50 nm
InGaN evaporation preventing layer 37 Mg-doped GaN optical guide layer having a thickness of 0.1 μm 38 Mg-doped p-type Al _0.1 Ga _{0.9 having a} thickness of 0.5 μm
N cladding 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 2 μm-thick Si-doped n-type GaN layer 44 0.5 μm-thick Si-doped n-type Al _0.1 Ga _0.9
N-cladding layer 45 Si-doped GaN optical guide layer with a thickness of 50 nm 46 5-atomic non-doped In _0.35 Ga _0.65 N light-emitting layer (single-quantum well layer) 47 Mg-doped GaN optical 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 cladding layer 48 Mg-doped p-type Al _0.1 Ga _0.9 N cladding layer 49 Mg-doped p-type GaN layer having a thickness of 0.5 μm 50 insulating film of silicon nitride film (Si ₃ N ₄ ) 51 n-type electrode 52 p-type electrode

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshiyuki Okumura 22-22 Nagaikecho, Abeno-ku, Osaka City, Osaka Sharp Corporation

Claims (9)

[Claims] 1. A semiconductor light-emitting device having a III-V 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; Unit quantum well layer thickness is 1
A semiconductor light emitting device comprising a number of atomic layers to 15 atomic layers. 2. The semiconductor light emitting device according to claim 1, wherein the composition of the single-semiconductor layer or the unit quantum well layer constituting the light emitting layer is such that the composition ratio of In which is a group III element is 35.
%, And not more than 65%. 3. The semiconductor light emitting device according to claim 2, wherein the light emitting layer is made of In _x Ga ₁ -xN (0.35 ≦ X ≦ 0.6
5) A semiconductor light emitting device characterized by the following. 4. The semiconductor light emitting device according to claim 2, wherein the light emitting layer is formed of In _x (Al _Y Ga _{1 -Y} ) ₁ -XN (0 <Y ≦
1.0, 0.35 ≦ X ≦ 0.65). 5. The semiconductor light emitting device according to claim 2, wherein the barrier layer forming the multiple quantum well structure is formed of In _x Ga _{1 -x.}
A semiconductor light-emitting device, wherein N (0.35 ≦ X ≦ 0.65). 6. The semiconductor light emitting device according to claim 2, wherein the barrier layer constituting the multiple quantum well structure is formed of In _x (Al _Y
Ga _1-Y ) _1-X N (0 <Y ≦ 1.0, 0.35 ≦ X ≦ 0.
65) A semiconductor light emitting device characterized by the above-mentioned. 7. The semiconductor light emitting device according to claim 2, wherein the composition of the barrier layer constituting the multiple quantum well structure is III.
A semiconductor light-emitting device comprising 35% or less of a composition ratio of In which is a group element. 8. The semiconductor light emitting device according to claim 7, wherein the barrier layer forming the multiple quantum well structure is formed of In _x Ga _{1 -x.}
A semiconductor light emitting device, wherein N (X ≦ 0.35). 9. The semiconductor light emitting device according to claim 7, wherein the barrier layer constituting the multiple quantum well structure is formed of In _x (Al _Y
Ga _1-Y ) _1-X N (0 <Y ≦ 1.0, X ≦ 0.35).