JP2001144378A - Compound semiconductor light-emitting element and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high-performance light-emitting element of a gallium nitride base, which has a high crystallization by suppressing a lattice distortion between a clad layer and guide and light-emitting layers in the element. SOLUTION: A GaN-based compound semiconductor light-emitting element includes a first clad layer of AlGaN, a second clad layer of AlGaN, and an active layer sandwiched between the first and second clad layers. The first clad layer is made in the form of an alternately laminated structure of a thin film of Aly1Ga1-y1N (y1<=1) and a thin film of Alz1Ga1-z1N (0.005<=z1<y1).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a GaN-based compound semiconductor light-emitting device having excellent light-emitting characteristics and lifetime characteristics, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Hitherto, GaN-based compound semiconductors have been used or studied as light-emitting devices and high-power devices. It can be used as a light emitting element having a wide width from blue to orange. In recent years, blue light-emitting diodes and green light-emitting diodes have been put to practical use by utilizing their characteristics, and blue-violet semiconductor lasers have been developed as semiconductor laser devices.

In a structure near a light emitting layer of a GaN-based compound semiconductor, particularly a light emitting layer of a laser diode, an n-type and a p-type GaN light guide layers are usually provided with an In-containing light emitting layer interposed therebetween. There are n-type and p-type AlGaN cladding layers with a larger band gap sandwiched therebetween.

However, the lattice constant of AlN in the a-axis direction is 3.11 °, GaN is 3.19 °, and InN is 3.54 °.
Since the lattices of the cladding layer, the guide layer, and the light emitting layer do not match, it has been difficult to form an element having high crystallinity.

[0005] For this reason, a method has been attempted in which a clad layer is formed in a multilayer structure to suppress lattice distortion. For example,
JP-A-5-110138 discloses an AlN thin film and Ga
Lamination of N thin films to produce a cladding layer with a multilayer structure. In the examples, examples of cladding layers with AlN thin film thicknesses and GaN thin film thicknesses of 5.0, 10.0 and 20.0 nm are introduced. are doing.

In Japanese Patent Application Laid-Open No. 5-110139, an AlN thin film and a GaN thin film are used as constituent thin films of a cladding layer. In the example, the thickness of the AlN thin film and the thickness of the GaN thin film were 10 nm at 2.0 nm and 8.0 nm, respectively.
An example is shown in which 10 layers of 6.0 nm and 24.0 nm N are laminated to produce 0.4 μm Al _0.2 Ga _0.8 N.

In Japanese Patent Application Laid-Open No. 10-173221, an n-type Al _0.15 Ga _0.85 N thin film and an n-type GaN thin film are used as constituent thin films of a cladding layer. Thickness 50-100nm
Al _0.15 Ga _0.85 N thin film with a thickness of 300 to 400 n
an n-type GaN thin film having an n-type cladding layer having a thickness of 10 m
P-type Al _0.15 Ga _0.85 N thin film and the thickness of to 20 nm 50 to
An example in which a p-type cladding layer is formed from a 80-nm p-type GaN thin film is introduced.

Further, the thickness of each thin film is 2.5 nm.
A cladding layer is composed of a _0.14 Ga _0.86 N thin film and a GaN: Si thin film, and a GaN-based compound semiconductor laser device manufactured using the cladding layer has been reported (Appl.
Phys. Lett. 73.832. (1998)).

[0009]

As described above, in order to obtain a highly crystalline light emitting device by suppressing lattice distortion between the cladding layer, the guide layer, and the light emitting layer, an attempt is made to form the cladding layer with a multilayer structure. However, in a conventional light emitting device having a clad layer having a multilayer structure, since the interface between thin films is not steep, crystallinity is low due to dislocation or the like. For this reason, the dopant is easily diffused and affects the active layer, which has been one of the factors for lowering the luminous efficiency. Furthermore, in order to prevent higher-order modes in the direction perpendicular to the substrate, which are problematic in the manufacture of laser devices, when the cladding layer having a conventional multilayer structure is made thicker, its crystallinity is low. There were problems such as the presence of serious defects.
As described above, the above-described conventional techniques are insufficient for obtaining a high-performance light-emitting element having a cladding layer with higher crystallinity.

[0010]

In order to solve the above-mentioned problems, the present invention provides a first clad layer made of AlGaN, a second clad layer made of AlGaN,
Having an active layer sandwiched between second cladding layers
In the N-based compound semiconductor light emitting device, the first cladding layer includes an Al _y1 Ga _1-y1 N (y1 ≦ 1) thin film and an Al _z1
Ga _{1 -z 1} N (0.005 ≦ z 1 <y 1) thin films are alternately stacked.

Here, it is particularly important that Al _y Ga _1-y
The point is that Al is always contained in both the N thin film and the Al _z Ga _{1 -z} N thin film. By ensuring that Al is contained in each of the thin films constituting the cladding layer, the flatness of the layer is improved and a layer with reduced dislocations and good crystallinity is obtained as compared with the case where there is a thin film into which Al is not introduced. Can be Thus, when the present invention is applied to the cladding layer serving as the base of the active layer, the crystallinity of the active layer is improved, and the luminous efficiency of the device is improved. Also,
By applying the present invention to the clad layer to which the dopant is added, diffusion of the dopant is suppressed, and a light-emitting element having good life characteristics can be obtained.

The above-mentioned Al _y1 Ga _1-y1 N (y1 ≦ 1)
The thickness of the thin film is not less than 3.0 nm and not more than 50 nm, and the thickness of the Al _z1 Ga _1-z1 N (0.005 ≦ z1 <y1) thin film is not less than 3.0 nm and not more than 50 nm. I have.

When each film thickness is smaller than this range, it is not preferable because control of the apparatus is difficult and the interface is roughened. When each film thickness is larger than this range, the lattice constant,
It is considered that the crystallinity of the manufactured device is greatly reduced because the difference in thermal expansion coefficient cannot be reduced.

Further, the second cladding layer made of AlGaN includes an Al _y2 Ga _1-y2 N (y2 ≦ 1) thin film and an Al
_{It is characterized in that z2Ga1 -z2N} (0.005≤z2 <y2) thin films are alternately laminated.

The above-mentioned _{Aly2Ga1 -y2N} (y2≤1)
The thickness of the thin film is not less than 3.0 nm and not more than 50 nm, and the thickness of the Al _z2 Ga _1-z2 N (0.005 ≦ z2 <y2) thin film is not less than 3.0 nm and not more than 50 nm. I have.

Further, the first clad layer and the second clad layer have different Al average compositions.

In particular, by increasing the Al composition or the film thickness of the n-type cladding layer, the light confinement effect on the n side is improved, and the relationship between input power and light output (good characteristics of the element) is maintained. However, it is considered that the higher-order mode phenomenon can be suppressed.

The above-mentioned Al _y1 Ga _1-y1 N (y1 ≦ 1)
The thickness of the thin film is different from the thickness of the Al _y2 Ga _1-y2 N (y2 ≦ 1), or the thickness of the Al _z1 Ga _1-z1 N
(0.005 ≦ z1 <y1) The thickness of the thin film and the Al _z2 G
a _1-z2 N (0.005 ≦ z2 <y2) The thickness of the thin film is different.

Further, the present invention is characterized in that y1 and y2 are different or z1 and z2 are different.

In one or both of the first cladding layer and the second cladding layer, In _w Ga _{1 -w}
It is characterized in that an N (0 <w <1) film is interposed.

Conventionally, GaN has been used to prevent cracks.
By introducing the In _w Ga _1-w N layer contained in the contact layer portion into the cladding layer, the strain during the growth of the crack prevention layer is introduced into each layer constituting the cladding layer in the form of dislocation or the like. Since the cladding layer has a multilayer structure, the propagation of dislocations at the interface is small, and the cladding layer absorbs and reduces strain.
For this reason, it is considered that the strain exerted on the active layer is largely suppressed, the crystallinity of the active layer becomes better than in the conventional structure, and the luminous efficiency as an element is improved.

Further, a first thin film made of Al _y Ga _{1 -yN} (y ≦ 1) and Al _z Ga ₁ -zN (0.005 ≦ z <y)
When forming an AlGaN layer in which a second thin film made of Al is alternately stacked, a predetermined growth interruption time is provided after the growth of the first thin film or the second thin film.

Here, the layers constituting the cladding layer are not limited to two types, and the order of Al _y G
If the relationship of laminating an Al _z Ga _1-z N thin film (0.005 <z ≦ y) next to the a _1-y N thin film (y ≦ 1) is maintained, the film thickness, the Al composition, and the doping concentration Three different
Combinations of more than one thin film are also possible.

Here, y is ny1 (the Al composition of the thin film constituting the first n-type cladding layer), ny2 (the Al composition of the thin film constituting the second n-type cladding layer), and py1 (the first p-type cladding layer). Composition of the thin film constituting the mold cladding layer), py2
(Al composition of the thin film that constitutes the second p-type cladding layer).

Further, y1 is a generic term including ny1 (the Al composition of the thin film constituting the first n-type cladding layer) and py1 (the Al composition of the thin film constituting the first p-type cladding layer).

Y2 is a generic term including ny2 (the Al composition of the thin film constituting the second n-type cladding layer) and py2 (the Al composition of the thin film constituting the second p-type cladding layer).

Ny is a generic term including ny1 (Al composition of the thin film constituting the first n-type cladding layer) and ny2 (Al composition of the thin film constituting the second n-type cladding layer).

Here, z is nz1 (the Al composition of the thin film constituting the first n-type cladding layer), nz2 (the Al composition of the thin film constituting the second n-type cladding layer), and pz1 (the first p-type cladding layer). Al composition of the thin film constituting the mold clad layer), pz2
(Al composition of the thin film that constitutes the second p-type cladding layer).

Further, z1 is a generic term including nz1 (the Al composition of the thin film constituting the first n-type cladding layer) and pz1 (the Al composition of the thin film constituting the first p-type cladding layer).

Z2 is a generic term including nz2 (the Al composition of the thin film constituting the second n-type cladding layer) and pz2 (the Al composition of the thin film constituting the second p-type cladding layer).

In addition, nz is a generic term including nz1 (Al composition of the thin film constituting the first n-type cladding layer) and nz2 (Al composition of the thin film constituting the second n-type cladding layer).

In the present invention, the GaN-based compound semiconductor refers to a III-N-based compound semiconductor in which the group V element is nitrogen, such as GaN, AlN, and Al.
αGa ₁ -αN (0 <α <1), InN, InβGa _1- β
N (0 <β <1), InγGaδAl ₁₋ γ ₋ δN (0 <
γ <1, 0 <δ <1).

[0033]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with specific examples.

(Embodiment 1) In this embodiment, an example in which the present invention is applied to a laser diode will be described. FIG. 1 is a cross-sectional view of a film manufactured by the method of manufacturing a GaN-based compound semiconductor laser diode in the present embodiment. A sapphire substrate (101) is used as a substrate, on which a GaN buffer layer (102), an n-type GaN contact layer (103), and an n-type cladding layer (104a) are formed. The n-type cladding layer (104a) is composed of an undoped Al _0.16 Ga _0.84 N thin film (104b) forming the n-type cladding layer and Al _0.02 Ga forming the n-type cladding layer.
It is formed of _0.98 N: Si thin film (104c). On the n-type clad layer (104a), an n-type GaN guide layer (105), an active layer (106), an AlGaN evaporation preventing layer (107), a p-type GaN guide layer (108), and a p-type clad layer (109a) Is formed. The p-type cladding layer (109a) is composed of an undoped Al _0.16 Ga _0.84 N thin film (109b) constituting the p-type cladding layer and an Al _0.02 Ga _0.98 N: Mg thin film (109c) constituting the p-type cladding layer.
Is formed. On the p-type cladding layer (109a), p
A GaN contact layer (110) is formed, and after crystal growth, a SiO ₂ insulating film (111) and a p-type electrode (112) are formed.
a), an n-type electrode (112b) is formed.

FIG. 2 is a schematic view of an MOCVD apparatus used for manufacturing the GaN-based compound semiconductor according to the present embodiment. In the drawing, (101) is a sapphire substrate having a (0001) plane, and this substrate is set on a quartz tray (203) on a carbon susceptor (202). A resistance heating heater also made of carbon is arranged in the susceptor, and the substrate temperature can be controlled by a thermocouple. (204) is a reaction tube made of double quartz, which is water-cooled. NH ₃ (209) is used as a group V raw material, and trimethyl gallium (hereinafter, TMG) (211a), TMA (211b),
Trimethyl indium (hereinafter, TMI) (211c) was used by bubbling with N ₂ or H ₂ (210). In addition, silane (hereinafter referred to as Si
H ₄ ) (212), and bis-cyclopentadienyl magnesium (hereinafter referred to as “p-type doping material”)
Cp ₂ Mg) (211d) was used. Each raw material is mixed with a carrier gas, N ₂ or H ₂ (210), by controlling the flow rate precisely by a mass flow controller (208), introduced into a reaction tube through a raw material inlet (204), and exhaust gas outlet From (205), it is discharged to an exhaust gas treatment device (207) through a pipe (206).

Using a sapphire substrate having a (0001) plane as a substrate, a GaN-based compound semiconductor layer is grown. In the figure, (101) is a sapphire substrate having a (0001) plane, and this substrate is a carbon susceptor (202).
Is placed on top. A resistance heating heater also made of carbon is arranged in the susceptor, and the substrate temperature can be controlled by a thermocouple.

(203) is a reaction tube made of double quartz, which is water-cooled. NH ₃ (2
06), and TMG (20
7a), TMA (207b) and TMI (207c)
Used by bubbling with ₂ or H ₂ (210). The n-type doping material is SiH ₄ (209)
And p-type doping material is Cp ₂ Mg
(207d) was used. Each raw material is mixed with a carrier gas, N ₂ or H ₂ (210), by controlling the flow rate precisely by a mass flow controller (208), introduced into a reaction tube through a raw material inlet (204), and exhaust gas outlet (205).

First, the substrate (101) is washed and set in a crystal growth apparatus. Substrate is 1100 ° C in H ₂ atmosphere
Heat treatment for about 10 minutes at a temperature of about
Cool down to about 50 ° C. If the temperature is constant, changing the carrier gas N _2, the total flow of N ₂ 10l / min. NH
₃ at 3 l / min. After a few seconds, flow TMG to 20 μmo
1 / min. The GaN buffer layer (102) was grown at a low temperature for one minute. The thickness of the grown film is 30
nm. Thereafter, the supply of TMG was stopped and the temperature was reduced to 1
The temperature was raised to 050 ° C., and TMG was added again at 50 μmol / mi.
n. And SiH ₄ gas at 10 nmol / min. Then, the n-type GaN contact layer (103) is grown by 4 μm.

Next, the supply of SiH ₄ gas was stopped, and TM
A at 10 μmol / min. Undoped Al _0.16 Ga _0.84 supplied to form an n-type cladding layer having a thickness of 4.0 nm
N thin film (104b) was formed, and SiN ₄ gas was further added at 5.0 nmol / min. And the supply amount of TMA was 1.5 μmol / min. To a 4.0 nm thick n
Al _0.02 Ga _0.98 N: Si thin film (104c) constituting the mold cladding layer (this layer is made thicker under the same conditions (0.4 μm)
Of Si sample measured by SIMS = 3
E + 18 cm ⁻³ ). This operation was repeated 100 times, and the thickness was 0.80 μm, the average composition was Al _0.09 Ga _0.91
A n-type cladding layer of N (104a) is grown.

Next, the supply of TMA was stopped, and 0.1 μm
Manufacturing (105) of an n-type GaN guide layer having a thickness is performed. n
SiH ₄ and TMG after growing GaN guide layer (105)
Is stopped, the temperature of the substrate is reduced to 730 ° C.,
When the temperature is stabilized, TMG is added at 10 μmol / min. ,
TMI of 10 μmol / min. Supplied with In _0.05 G
An active layer barrier layer of a _0.95 N was grown to a thickness of 5 nm.

[0041] At the time of the active layer growth, 10nmo the SiH ₄
1 / min. It may flow to the extent. Then, add 10 TMG
μmol / min. , TMI was 50 μmol / min.
And the well layer of the active layer made of In _0.2 Ga _0.8 N
It was grown to a thickness of nm. Then, TMI is set to 1
0 μmol / min. Change to, the growth of the barrier layer of the active layer made of In _0.05 Ga _0.95 N to a thickness of 5 nm. The growth of the barrier layer and the well layer which become the active layer is repeated, and after the growth of three multiple quantum wells, the barrier layer is finally grown to terminate the growth of the active layer (106). After the active layer is grown, in order to prevent the release of In from the InGaN film,
TMG was added at 10 μmol / min. , TMA 5μmol
/ Min. , And Cp ₂ Mg at 0.20 nmol / mi
n. Then, a p-type AlGaN evaporation preventing layer (107) having a thickness of 30 nm is grown. Then, TMG, TMA, C
The supply of p ₂ Mg is stopped, and the substrate temperature is raised again to 1050 ° C. After the temperature was raised, TMG was added at 50 μmol / min. And Cp ₂ Mg, and a p-type GaN guide layer (108) is grown to 0.1 μm.

Next, the supply of Cp ₂ Mg is stopped and TM
A at 10 μmol / min. Undoped Al _0.16 Ga _0.84 supplied to form a 4.0 nm thick p-type cladding layer
N thin film (109b) was formed, and the supply amount of TMA was 1.5 μmol / min. And change Cp ₂ Mg to 0.2
0 nmol / min. The Al _0.02 Ga _0.98 N: Mg thin film (109
c) (Mg concentration = 2E + 20 when this layer was thickened (0.4 μm) under the same conditions and measured by SIMS)
cm ^-3 ). This operation is repeated 100 times to grow a p-type cladding layer (109a) having a thickness of 0.80 μm and an average composition of Al _0.09 Ga _0.91 N.

After the growth, the supply of TMA is stopped, and TM
G and Cp ₂ Mg are supplied to form a p-type GaN contact layer (1).
10) is grown 0.5 μm, and after completion, TMG and Cp ₂ M
The supply of g is stopped to end the substrate heating.

Next, this grown film is subjected to photolithography and dry etching techniques to make the GaN-based crystal <1--1.
100> direction, the p-type cladding layer (10
9a) Etching up to the surface, width 30 μm, length 60
0 μm mesa type, SiO ₂ insulating film (111) is formed on p-type GaN contact layer, and n
After forming a groove reaching the p-type GaN contact layer, an n-type electrode (112b) made of Ti and Al is formed on the exposed n-type GaN contact layer, and Pd is formed on the surface of the p-type GaN contact layer.
A Au type p-type electrode (112a) having a width of 2 μm and a length of 600 μm was formed.

Next, a 650 μm long laser resonator was formed by cleaving the GaN-based crystal on the (1-100) plane. A dielectric multilayer film of titanium oxide and magnesium fluoride having a reflectivity of 70% is formed on the back end face, and a silicon nitride film having a reflectivity of 12% is formed on the front end face. Then, a laser device was manufactured.

The characteristics of the laser device thus manufactured were measured.
A, laser continuous oscillation with a low threshold value and high luminous efficiency, with a differential luminous efficiency of 0.95 W / A, was obtained. The operating current at room temperature with an optical output of 35 mW was 55.4 mA, and the operating voltage was 4.0 V (input power: 221.6 mW).

As Comparative Example 1, the cladding was
Al_0.16Ga_0.84N thin film and GaN thin film without Al
Consists of a film (Si and Mg concentrations are the same as in this embodiment)
And both thicknesses are 4.0 nm (all cladding layer thicknesses are p-type,
When the n-type is 0.80 μm), the light output is 35 mW
At room temperature was 541.4 mW. Also,
Further, as Comparative Example 2, undoped Al of Comparative Example 1_0.16G
a_0.84Undoped Al for N layer_0.18Ga_0.82Change to N layer
Thus, the average composition is changed to Al as in the present embodiment._0.09Ga _0.91
In the case of a device with N, the input power at room temperature with an optical output of 35 mW
The power was 578.2 mW, and in any case,
The laser device manufactured in the form operates at lower power.
You can see that

Further, it was confirmed that the element life was greatly improved. This is because, as in the present invention, Al is always contained in each of the thin films constituting the cladding layer, so that the flatness of the layer is improved as compared with the case where there is a thin film into which Al is not introduced. And a layer having good crystallinity with a reduced number of particles. Thus, when the present invention is applied to the cladding layer serving as the base of the active layer, the crystallinity of the active layer is improved, and the luminous efficiency of the device is improved. In addition, by applying the present invention to the clad layer to which the dopant is added, defects such as dislocations as diffusion paths are reduced, diffusion of the dopant is suppressed, and as a result, a light-emitting element having good lifetime characteristics can be obtained. it is conceivable that.

In fact, the full width at half maximum (hereinafter referred to as FWHM) of 0002 reflection of the X-ray diffraction pattern of the crystal film manufactured by the method of the present embodiment is 3.6 arcmin. , The etch pit density (hereinafter referred to as EPD) is 6.5E + 8 cm ⁻² , and the undoped Al _0.16 Ga
_It is composed of a _0.84 N thin film and a GaN thin film containing no Al (Si and Mg concentrations are the same as those of the present embodiment), and both have a thickness of 4.0 nm (all cladding layers have a thickness of 0.8 nm for both p-type and n-type).
0 μm), the FWHM of the 0002 reflection of the X-ray diffraction pattern is 4.1 arcmin. , EPD is 1.5E
+9 cm ^-2 .

Also, as in Comparative Example 2, undoped Al
_0.16 Ga _0.84 N-layer instead of the undoped Al _{0. 18} Ga _0.82 N layer, the average composition in the same manner as the present embodiment Al _0.09 Ga
Even in the case of an element set to _0.91 N, the X-ray diffraction pattern of 00
FWHM of the 02 reflection is 4.3 arcmin. , EPD was about 2.1E + 9 cm ^-2 . Thus, it can be seen that the use of the method of the present embodiment greatly improves the crystallinity.

From the results of TEM observation, in contrast to Comparative Examples 1 and 2, the interface of the cladding layer of the present embodiment is steep and defects such as dislocations are considerably reduced.
Further, it was found from the SIMS results that the diffusion of Mg as a p-type dopant was suppressed by one digit or more.

Next, the thickness of the thin film constituting the cladding layer is preferably from 3.0 nm to 50.0 nm, more preferably from 3.0 nm to 10.0 nm. I have confirmed. When each film thickness is smaller than this range, it is not preferable because control of the device is difficult and the interface is roughened without completing the molecular layer, and when each film thickness is larger than this range, the lattice constant, It is considered that the difference in thermal expansion coefficient cannot be reduced, and the high Al mixed crystal layer has defects, and the crystallinity of the manufactured device is greatly reduced.

Actually, Al _0.16 Ga constituting the cladding
The thicknesses of the _0.84 N thin film and the Al _0.02 Ga _0.98 N thin film are both 3.0 nm, 5.0 nm, 10.0 nm (Si and Mg concentrations are almost the same as in this embodiment, and the total cladding layer thickness is p
And n-type are both set to 0.80 μm).
The input power at room temperature of 5 mW was 269.5 m each.
W, 211.4 mW, 294.6 mW, Al _0.16 Ga _0.84 N thin film, Al _0.02 Ga _0.98 constituting the cladding
When the thickness of the N thin film is 60 nm (Si and Mg concentrations are almost the same as in the present embodiment, and the total cladding layer thickness is 0.80 μm for both the p-type and the n-type), the device is capable of continuous oscillation at room temperature. Did not reach.

As described above, according to the present invention, the n-type clad layer or the p-type clad layer is formed of Al _{y having} different compositions from each other.
Since it was composed of the Ga _1-y N thin film and the Al _z Ga _1-z N thin film, a high-quality light emitting device could be realized. Here, the range of y is 0.05 ≦ y ≦ 0.40, more preferably 0.10.
≦ y ≦ 0.30 is effective, and the range of z is 0.005
≦ z ≦ 0.10, more preferably 0.005 ≦ y ≦ 0.
05 is effective. If the Al composition is low, the confinement effect of the entire cladding layer is weakened, and if the Al composition is high, the crystallinity is undesirably reduced. The range of yz is 0.05 ≦
yz ≦ 0.39 is preferred, and more preferably 0.10
≤ yz ≤ 0.39. If yz is too small, the crystallinity decreases in the range of 0.15 ≦ y ≦ 0.40,
The range of 0.05 ≦ y ≦ 0.15 is not preferable because the light confinement effect is weakened. On the other hand, if yz is too large, the crystallinity is undesirably reduced.

Next, the thickness of the thin film constituting the cladding layer,
The result of a detailed examination of a preferable range of the composition will be described.

Al _0.16 Ga constituting the n-type cladding layer
Thickness and light output of _0.84 N thin film and Al _0.02 Ga _0.98 N thin film 3
FIG. 7 shows the relationship between the input power at a room temperature of 5 mW. Note that p
Al _0.16 Ga _0.84 N thin film that forms the mold cladding layer, Al
The thickness of the _0.02 Ga _0.98 N thin film was 5.0 nm for both, the total cladding layer thickness was 0.80 μm for both n-type and p-type, and the concentrations of Si and Mg contained in the cladding layer were about the same as in Example 1. .

As shown in FIG. 7, the thickness of the thin film constituting the cladding layer is 2.5 nm or less and 60 n
m and over 600 W, and the thickness of the thin film is 3.0
nm to 50 nm, more preferably 3.0 to 10.0.
nm is preferred. When each film thickness is smaller than this range, it is not preferable because the control of the thin film manufacturing apparatus is difficult, and the interface is roughened because the molecular layer is not completed, and when each film thickness is larger than this range. It is considered that the difference between the lattice multiplier and the thermal expansion coefficient cannot be alleviated, the Al-rich mixed crystal layer has defects, and the crystallinity of the manufactured light emitting device is greatly reduced.

The same tendency is shown for the p-type cladding layer. Incidentally, Al _0.16 Ga constituting the n-type cladding layer
The thickness of each of the _0.84 N thin film and the Al _0.02 Ga _0.98 N thin film is 5.
0 nm, total cladding layer thickness is 0.80 μm for both n-type and p-type
The concentrations of Si and Mg contained in the cladding layer were substantially the same as in Example 1.

Al _y1 Ga _1-y1 constituting the n-type cladding layer
FIG. 8 shows the relationship between the Al composition y1 of the N (y1 ≦ 1) thin film and the input power at room temperature with an optical output of 35 mW. In addition, n type and p
The thicknesses of the thin films constituting the mold cladding layer are both 5.0 nm,
The total cladding layer thickness is 0.80 μm for both n-type and p-type,
The lower Al composition was used as the Al _0.02 Ga _0.98 N thin film, and the concentrations of Si and Mg contained in the cladding layer were almost the same as in Example 1.

As can be seen from FIG. 8, the Al composition y of the Al _y1 Ga _1-y1 N (y1 ≦ 1) thin film constituting the n-type cladding layer
1 is preferably 0.005 to 0.40, more preferably 0.10
~ 0.30 is preferred. If the Al composition is low, the confinement effect of the entire cladding layer is weakened, and if it is high, the crystallinity is undesirably reduced. The same tendency is shown for the p-type cladding layer.

In addition, compared to a GaN thin film containing no Al, the Al _x Ga ₁ -xN thin film contains more carbon due to TMA as a raw material used when introducing Al, and has a certain amount of carbon. It has been confirmed that the crystallinity is improved, and that an n-type and a p-type can be more easily achieved. In terms of doping characteristics, it is necessary to include Al in each of the thin films constituting the cladding layer. Is considered more desirable to improve

Further, _Alny G constituting the n-type cladding layer
The carbon concentration C (ny) of the a _1-ny N (ny ≦ 1) thin film is
5E + 15 (current detection limit value) to 1E + 19 cm ^-3 when 0.40 <ny ≦ 1, 5 when ny ≦ 0.40
E + 15 to 1E + 18 cm ^-3 is desirable. Al _nz Ga
The carbon concentration C (nz) of the _1-nz N (nz ≦ 1) thin film is 0.5.
5E + 15 in all ranges of 005 ≦ nz <ny
１1E + 19 cm ⁻³ is desirable. In particular, 0.40 <ny
If ≤1, C (nz) is 5E + 15E + 18cm
^-3 , when ny ≦ 0.40, C (nz) is 5E + 15
It is preferably 5E + 18 cm ^-3 .

Further, Al _py G constituting the p-type cladding layer
The carbon concentration C (py) of the a _1-py N (py ≦ 1) thin film is
5E + 15 (current detection limit value) to 1E + 19 cm ^-3 when 0.40 <py ≦ 1, and 5 when py ≦ 0.40
E + 15 to 1E + 18 cm ^-3 is desirable. Al _pz Ga
The carbon concentration C (pz) of the _1-pz N (pz ≦ 1) thin film is 0.1.
5E + 15 in all ranges of 005 ≦ pz <py
１1E + 19 cm ⁻³ is desirable. In particular, 0.40 <py
When ≤1, C (pz) is 5E + 15E + 18cm
^-3 , when py ≦ 0.40, C (pz) is 5E + 15
It is preferably 5E + 18 cm ^-3 . It has been confirmed that if the carbon concentration is too low or too high, the crystallinity of the semiconductor decreases, the element resistance increases, and it becomes difficult to make the semiconductor device n-type or p-type. .

Further, _Alny G constituting the n-type cladding layer
a _1-ny N (ny ≦ 1) thin film dopant concentration C (dn
y) is preferably 5E + 19 cm ^-3 or less. C (dn
If y) is too high, the crystallinity decreases, which is not desirable. Al
_{nz Ga 1-nz N (0.005} ≦ pz <py) dopant concentration of the thin film C (dnz) is, 1E + 17~1E + 19cm
^-3 is preferred. If C (dnz) is too high, the crystallinity decreases, and if it is too low, the resistance increases, which is not preferable.

Further, Al _py G constituting the p-type cladding layer
a _1-py N (py ≦ 1) Dopant concentration C (dp
y) is preferably 5E + 20 cm ^-3 or less. C (dp
If y) is too high, the crystallinity decreases, which is not desirable. Al
_{pz Ga 1-pz N (0.005} ≦ pz <py) of the thin film dopant concentration C (DPZ) is, 1E + 18~1E + 19cm
^-3 is preferred. If C (dpz) is too high, the crystallinity decreases, and if it is too low, the resistance increases, which is not preferable.

Here, the average composition of Al means that the Al composition of each thin layer constituting the cladding layer is determined from the substrate side as y (1), z (1), y (2), z (2), y ( 3),
As z (3),..., y (m), z (m), the thickness of each thin layer constituting the cladding layer is determined from the substrate side as T (y (1)), T (z (1)). , T (y (2)), T
(Z (2)), T (y (m)), T (z
(M)), the average Al composition (M (Al)) can be expressed by Equation 1.

[0067]

(Equation 1)

The average Al compositions of the n-type cladding layer and the p-type cladding layer are both 0.05 ≦ M (Al) ≦ 0.30
Thus, an effect appears. Furthermore, 0.07
By setting ≦ M (Al) ≦ 0.20, more effect can be obtained. If it is low, the confinement effect becomes weak, and if it is high, the crystallinity decreases, which is not preferable.

The effect is exhibited when the total thickness of both the n-type cladding layer and the p-type cladding layer is 0.20 μm to 3.00 μm. Furthermore, 0.50 μm
When the thickness is up to 1.50 μm, more effects can be obtained.
If the total thickness of the cladding layer is small, the confinement effect becomes weak, and if the total thickness is large, the element resistance increases and the crystallinity also decreases, which is not preferable.

In particular, when the average Al composition is 0.05 to 0.10
The total thickness of the cladding layer is 0.50 μm to 3.00.
μm, when the average Al composition is 0.10 to 0.20, the total thickness of the cladding layer is 0.50 μm to 2.50 μm, and the average A
When the l-composition is 0.20 to 0.30, the effect appears when the total thickness of the cladding layer is 0.05 μm to 1.50 μm.

In this embodiment, the n-type cladding layer is made of Al
_ny Ga _1-ny N (ny ≦ 1) thin film and Al _nz Ga _1-nz N
(0.005 ≦ nz ≦ ny) thin film, and the p-type cladding layer is composed of Al _py Ga _1-py N (py ≦ 1) thin film and Al
_pz Ga _1-pz N constituted by (0.005 ≦ pz ≦ py) thin film, and the Al _ny Ga _1-ny N thin film and Al _py Ga _1-py N thickness of the thin film with the same, Al _nz Ga _1-nz N thin film and Al _pz Ga _1-pz
The thickness of the N thin film was the same, but the thickness of the Al _ny Ga _1-ny N thin film was different from the thickness of the Al _py Ga _1-py N thin film, or the thickness of the Al _nz Ga _1-nz N thin film was It has been confirmed that the effect is exhibited even in a device having a configuration in which the thickness of the Al _pz Ga _1-pz N thin film is different. In the present embodiment, (n
y) = (py) and (nz) = (pz), but (n
y) and (py) are different, or (nz) and (p)
It has been confirmed that the effect is exhibited even in the elements having different configurations of z). In addition, it has been confirmed that the effect is exhibited also in an element having a configuration in which the Al composition is different between the n-type cladding layer and the p-type cladding layer.

In this embodiment, both the n-type cladding layer and the p-type cladding layer are made of an Al _y Ga _{1 -yN} (y ≦ 1) thin film and an Al _z Ga ₁ -zN (0.005 ≦ z < y) A thin film and a thin film are alternately laminated, but only one side of the n-type cladding layer or the p-type cladding layer
_y Ga _1-y N (y ≦ 1) thin film and Al _z Ga _1-z N (0.0
05 ≦ z <y) Even in the case of a structure in which thin films are alternately stacked, the effect of improving the crystallinity and characteristics of the element has been confirmed.

The layers constituting the cladding layer are not limited to two kinds, but in terms of the order, the Al _y Ga _{1 -y} N thin film (0 <y <1), then the Al _z Ga _{1 -z} N thin film (0 <z ≦
If the relationship of stacking y) is maintained, the film thickness, Al
A combination of three or more kinds of thin films having different compositions and doping concentrations is also possible, and the effect has actually been confirmed.

When a c-plane substrate is used, the direction perpendicular to the substrate surface (the direction in which crystals are stacked) and the c-axis of the growth substrate are set to 0.10.
When it is shifted by 0.2 to 0.25 °, more preferably 0.1 °
It has been confirmed that when the angle is shifted by 5 ° to 0.20 °, the flatness of the growth surface is promoted, the crystallinity of the entire device is improved, and the characteristics of the active layer are further improved.

In this embodiment, an example in which a sapphire substrate having a (0001) plane is used has been described. However, a sapphire substrate having another plane, GaN, SiC, spinel, mica, or the like can be applied. It has been confirmed that the same effects as those of the embodiment appear.

When GaN is used as the substrate, it is not necessary to perform heat treatment in an H ₂ atmosphere and grow the buffer layer at a low temperature, and the temperature is raised by using a carrier gas mainly composed of an inert gas and NH 3. It can be carried out in _three atmospheres and at the same time as the introduction of TMG and / or SiH ₄ from the growth of the underlying GaN film. In this case also, the light emitting device produced has the same effects as the present embodiment.

In this embodiment, the case where a GaN film is grown as the low-temperature buffer layer has been described. However, even if AlηGa ₁ -ηN (0 ≦ η ≦ 1) is used as the low-temperature buffer layer, ZnO is further used. In any case, there is no problem in manufacturing the light emitting element, and in each case, the same effect as that of the present embodiment is exhibited.

(Embodiment 2A) In this embodiment, n
The result of manufacturing a GaN-based compound semiconductor laser diode in which the configuration of the p-type cladding layer is different from that of the p-type cladding layer will be described.

A cross-sectional view of a film manufactured by the method of manufacturing a GaN-based compound semiconductor laser diode of the present embodiment is shown in FIG.
4b) undoped Al _0.20 constituting the n-type cladding layer
The Ga _0.80 N thin film and (104c) are Al _0.04 Ga _0.96 N thin films constituting the n-type cladding layer. The schematic diagram of the MOCVD apparatus used in the present embodiment is the same as FIG. 2 used for describing the first embodiment.

A case where the average Al composition of the n-type cladding layer is increased as compared with the p-type cladding layer will be described.

The method of forming the n-type cladding layer (104a) is as follows. After the growth of the 4 μm n-type GaN contact layer (103), the supply of SiH ₄ gas is stopped, TMA is supplied, and the n-type Undoped A constituting the cladding layer
l _0.20 Ga _0.80 N layer (104b) is formed.
H ₄ gas was supplied, the supply amount of TMA was changed, and the thickness was 4.0.
Al _0.04 Ga _0.96 N constituting the n-type cladding layer of nm:
Si layer (104c) (this layer is thickened under the same conditions (0.4
(μm) is measured to form a Si concentration = 3E + 18 cm ⁻³ ) as measured by SIMS. Perform this operation 100 times.
Times, thickness 0.80 μm, average composition Al _0.12 Ga
_{A 0.88} N n-type cladding layer (104a) is grown.

In the subsequent steps, growth was performed in the same manner as in Embodiment 1, the crystal film was processed, and a laser device was manufactured.

When the characteristics of this laser device were measured,
Laser continuous oscillation with high luminous efficiency was obtained at a low threshold. The input power at room temperature with an optical output of 35 mW is 241.7.
mW, and the device characteristics were improved as compared with the comparative example of the first embodiment.

At present, when a GaN-based compound semiconductor LD is used as a laser element for pickup, a higher-order mode of the laser on the n-type cladding layer side is a problem. By increasing only the Al composition of the layer, the light confinement effect on the n side was improved, and this phenomenon was successfully reduced while maintaining the relationship between the input power and the light output.

(Example 2B) Next, the n-type clad layer and the p-type
The case where the layer thickness of the n-type cladding layer in the mold cladding layer is increased will be described. After the growth of the 4 μm n-type GaN contact layer (103), the supply of SiH ₄ gas is stopped, TMA is supplied, and the undoped Al _0.16 Ga _0.84 N layer (104) constituting the 4.0-nm thick n-type cladding layer is formed.
b) is formed, SiH ₄ gas is further supplied, the supply amount of TMA is changed, and an Al _0.02 Ga _0.98 N: Si layer (104c) constituting an n-type cladding layer with a thickness of 4.0 nm (this layer is The sample whose thickness is increased (0.4 μm) under the conditions
An Si concentration as measured by S = 3E + 18 cm ^-3 ) is formed. This operation was repeated 150 times to obtain a thickness of 1.20 μm.
m, n-type cladding layer of composition Al _0.09 Ga _0.91 N (104
a) grow. In the subsequent steps, growth was performed in the same manner as in Embodiment 1, the crystal film was processed, and a laser element was manufactured.

When the characteristics of this laser device were measured,
Laser continuous oscillation with high luminous efficiency was obtained at a low threshold. The input power at room temperature with an optical output of 35 mW is 231.8.
mW, and the light emitting characteristics of the device were improved as compared with the comparative example of the first embodiment. Further, the life characteristics were also improved.

Further, as in the present embodiment, by increasing only the thickness of the n-type cladding layer, the light confinement effect on the n side is improved, and the relationship between the input power and the light output is maintained. Higher-order mode phenomena could be suppressed considerably.

In the above-described Embodiments 2A and 2B, the following configuration is desirable. In order to suppress higher-order modes while maintaining the relationship between input power and optical output, the average Al composition of the n-type cladding layer (Mn (Al))
Is preferably 0.07 ≦ Mn (Al) ≦ 0.30, more preferably 0.10 ≦ Mn (Al) ≦ 0.25. The thickness of the n-type cladding layer is 0.40 μm to 3.0 μm.
0 μm is preferred, and more preferably 0.80 μm to 1.80.
μm is preferred.

In this case, although the average Al composition and the film thickness of the n-type cladding layer can be independently changed, there is an effect, but it has been confirmed that the effect can be further improved by changing both of them. Also, the thickness of the Al _ny Ga _1-ny N thin film and Al _py Ga
The thickness of the _1-py N thin film is different or Al _nz Ga
_It has been confirmed that the effect is exhibited even in a device having a structure in which the thickness of the _1-nz N thin film is different from the thickness of the Al _pz Ga _1-pz N thin film. In addition, it has been confirmed that the effect is exhibited also in an element having a configuration in which (ny) and (py) are different or a configuration in which (nz) and (pz) are different. When the thickness of the thin film constituting the cladding layer closer to the substrate is reduced and the Al composition is increased, the distortion caused by the difference between the lattice constant and the thermal expansion coefficient from sapphire can be suppressed, and the high crystallinity A light-emitting element having good characteristics can be obtained.

In Embodiments 2A and 2B, both the n-type cladding layer and the p-type cladding layer are Al _y Ga _{1 -yN} (y
≦ 1) Thin film and Al _z Ga _1-z N (0.005 ≦ z <y)
The thin film and the thin film are alternately stacked, but only on one side of the n-type clad layer or the p-type clad layer, an Al _y Ga _1-y N (y ≦ 1) thin film and an Al _z Ga _{1- z} N
(0.005 ≦ z <y) Even in the case of a structure in which thin films are alternately stacked, an effect of improving the crystallinity and characteristics of the element has been confirmed.

The Al composition ratio y of the thin film is 0.05 ≦ y ≦
It is effective when 0.40, more preferably 0.10 ≦ y ≦ 0.30, and z is effective when 0.005 ≦ z ≦ 0.1, more preferably 0.005 ≦ z ≦ 0.05. Also, y-
The range of z is effective when 0.05 ≦ y ≦ 0.39, more preferably 0.10 ≦ y ≦ 0.39.

The thickness of the thin film constituting the cladding layer is preferably 3.0 nm to 50.0 nm, more preferably 3.0 nm to 10.0 nm, and it has been confirmed that the effect of further improving the crystallinity appears. I have.

The thickness of the p-type cladding layer is from 0.20 μm
An effect appears when the thickness is 2.50 μm. Further, when the thickness is 0.50 μm to 1.50 μm, more effects are exhibited.

The average Al composition of the p-type cladding layer (Mp (A
1)) has an effect because 0.05 ≦ Mp (Al) ≦ 0.25. Furthermore, 0.07 ≦
When Mp (Al) ≦ 0.20, the effect is more apparent.

The layers constituting the cladding layer are not limited to two types, and the order of the layers is not limited to Al _y Ga _{1 -yN} thin film (0 <y <1), then Al _z Ga _{1 -z} N thin film. (0 <z ≦
If the relationship of stacking y) is maintained, the film thickness, Al
A combination of three or more kinds of thin films having different compositions and doping concentrations is also possible, and the effect has actually been confirmed.

As in the first embodiment, when a c-plane substrate is used, when the vertical direction of the substrate surface (the direction of crystal lamination) and the c-axis of the growth substrate are shifted by 0.10 ° to 0.25 °, More preferably, when shifted by 0.15 ° to 0.20 °,
It has been confirmed that the flatness of the growth surface is promoted, the crystallinity of the entire device is improved, and the characteristics of the active layer are further improved.

In Embodiments 2A and 2B, (0001)
Although an example using a sapphire substrate having a surface has been described, sapphire substrates of other surfaces, GaN, SiC, spinel, mica, etc. can be applied, and it is confirmed that the same effects as those of the present embodiment can be obtained with any substrate. are doing.

When GaN is used as the substrate, it is not necessary to perform heat treatment in an H ₂ atmosphere and grow the buffer layer at a low temperature, and the temperature is raised by using a carrier gas mainly composed of an inert gas and NH 3. It can be carried out in _three atmospheres and at the same time as the introduction of TMG and / or SiH ₄ from the growth of the underlying GaN film. In this case also, the light emitting device produced has the same effects as the present embodiment.

In the embodiments 2A and 2B, the case where a GaN film is grown as a low-temperature buffer layer has been described. However, as a low-temperature buffer layer, AlηGa ₁ -ηN
Even when (0 ≦ η ≦ 1) is used, and when ZnO is further used, there is no problem in manufacturing a light emitting element, and in each case, the same effect as that of the present embodiment appears.

[0100] (Embodiment 3) In this embodiment, _{In 1-w Ga w N (} 0 <w <1) results of GaN-based compound semiconductor laser diode incorporating a crack preventing layer were prepared in the clad layer explain.

FIG. 3 is a cross-sectional view of a film manufactured by the method of manufacturing a GaN-based compound semiconductor laser diode of the present embodiment. Sapphire substrate (101) as the substrate
GaN buffer layer (102), n-type G
An aN contact layer (103) and a first n-type clad layer (304a1) are formed. The first n-type cladding layer (304a1) is composed of an undoped Al _0.16 Ga _0.84 N thin film (304b) forming the n-type cladding layer and an Al _0.02 Ga _0.98 N: Si thin film (30) forming the n-type cladding layer.
4c).

On the first n-type cladding layer (304a1), an In _0.1 Ga _0.9 N crack preventing layer (313),
A n-type cladding layer (304a2) is formed. The second n-type cladding layer (304a2) is made of an undoped Al _0.16 Ga _0.84 N thin film (30), which constitutes the n-type cladding layer, similarly to the first n-type cladding layer (304a1).
4b) and Al _0.02 Ga constituting the n-type cladding layer
It is formed of a _0.98 N: Si thin film (304c). Second
N-type GaN guide layer (105), active layer (106), AlGaN evaporation preventing layer (107), p-type GaN guide layer (108), p-type
A mold cladding layer (109a) is formed.

The p-type cladding layer (109a) is composed of an undoped Al _0.16 Ga _0.84 N thin film (109b) forming the p-type cladding layer and Al _0.02 G forming the p-type cladding layer.
a _{0. 98} N: formed by Mg thin film (109c). A p-type GaN contact layer (110) is formed on the p-type cladding layer (109a). After crystal growth, an SiO ₂ insulating film (111), a p-type electrode (112a), and an n-type electrode (11) are formed.
2b) is formed.

The schematic diagram of the MOCVD apparatus used in the present embodiment is the same as that shown in FIG. 2 used for describing the first embodiment. A description will be given of the result of fabricating a GaN-based compound semiconductor laser diode in which an In _0.1 Ga _0.9 N crack prevention layer is incorporated in an n-type cladding layer. The growth method is the same as that of the first embodiment up to the n-type GaN contact layer.

Thereafter, the supply of the SiH ₄ gas was stopped, and T
MA at 10 μmol / min. Supply, thickness 4.0nm
Al _0.16 Ga constituting the n-type cladding layer of
_0.84 N layer (304b) formed, further the SiH ₄ gas 5.0nmol / min. And the supply amount of TMA was 1.5 μmol / min. To a 4.0 nm thick n
Al _0.02 Ga _0.98 N: Si layer (304c) constituting the mold clad layer (this layer is thickened under the same conditions (0.4 μm)
Of Si sample measured by SIMS = 3
E + 18 cm ^-3 ) is formed. This operation was repeated 50 times, and the thickness of 0.5 μm and the average composition of Al _0.09 Ga _0.91 N
A n-type cladding layer (304a1) is grown.

Next, 5.0 nmol / mi of SiH ₄ was added.
n. , TMG at 10 μmol / min. , TMI to 50
μmol / min. Then, a crack preventing layer (313) made of In _0.2 Ga _0.8 N was grown to a thickness of 0.1 μm.

Thereafter, the supply of the SiH ₄ gas was stopped, and T
MA at 10 μmol / min. Supply, thickness 4.0nm
Of an undoped Al _0.16 Ga _0.84 N layer (304b), and 5.0 nmol / min. Of SiH ₄ gas. And the supply amount of TMA was 1.5 μmol / min. And a 4.0 nm thick Al _0.02 Ga _0.98 N: Si layer (3
04c) (Si concentration = 3E + 18 cm ⁻³ ) is formed.
This operation was repeated 50 times, and the thickness was 0.5 μm and the composition was Al.
_0.09 Ga _0.91 N second n-type cladding layer (304a
2) is grown, and an InGaN crack preventing layer is incorporated in the n-type cladding layer. In the subsequent steps, growth was performed in the same manner as in Embodiment 1, the crystal film was processed, and a laser element was manufactured.

When the characteristics of this laser device were measured,
Laser continuous oscillation with high luminous efficiency was obtained at a low threshold. The input power at an optical output of 35 mW is 192.1 mW, which is smaller than that of an element in which a crack preventing layer is inserted in an n-type GaN contact layer other than the cladding layer or between the n-type GaN contact layer and the n-type cladding layer. It was confirmed that the light emitting characteristics of the device were improved. Further, the life characteristics were also improved.

Conventionally, GaN has been used to prevent cracks.
By introducing the In _w Ga _1-w N layer contained in the contact layer portion into the cladding layer, the strain during the growth of the crack prevention layer is introduced into each layer constituting the cladding layer in the form of dislocation or the like. Since the cladding layer has a multilayer structure, the propagation of dislocations at the interface is small, and the cladding layer absorbs and reduces strain.
For this reason, the strain exerted on the active layer is largely suppressed. For this reason, the crystallinity of the active layer and the luminous efficiency as an element are improved as compared with the conventional case.

Although an effect is also obtained in a device in which a crack preventing layer is incorporated in the second clad layer, it has been confirmed that the effect is further exhibited by incorporating a crack preventing layer in the first and second clad layers. I have.

In this embodiment, the n-type cladding layer
And p-type cladding layer, Al_yGa_1-yN (y ≦ 1) thin
Film and Al_zGa_1-zN (0.005 ≦ z <y) thin film
The structure is alternately stacked, but the crack prevention layer
The n-type cladding layer or the p-type cladding layer
Crack prevention layer for only one side of the cladding layer
Only for the cladding layer incorporating_yGa_1-yN (y
≦ 1) Thin film and Al _zGa_1-zN (0.005 ≦ z <y)
By adopting a structure in which thin films are alternately stacked,
The effect of improving crystallinity and characteristics has been confirmed.

The Al composition ratio y of the thin film is 0.05 ≦ y ≦
It is effective when 0.40, more preferably 0.10 ≦ y ≦ 0.30, and z is effective when 0.005 ≦ z ≦ 0.1, more preferably 0.005 ≦ z ≦ 0.05. Also, y-
The range of z is effective when 0.05 ≦ yz ≦ 0.39, and more preferably 0.10 ≦ yz ≦ 0.39.

The thickness of the thin film constituting the cladding layer is preferably 3.0 nm to 50.0 nm, more preferably 3.0 nm to 10.0 nm, and it has been confirmed that the effect of improving the crystallinity appears. I have.

The average Al compositions (M (Al)) of the n-type cladding layer and the p-type cladding layer are both 0.05 ≦ M (A
l) ≦ 0.30 produces an effect. Further, when 0.07 ≦ M (Al) ≦ 0.20, the effect is more enhanced. If it is low, the confinement effect becomes weak, and if it is high, the crystallinity decreases, which is not preferable.

The effect is exhibited when the total thickness of each of the n-type cladding layer and the p-type cladding layer is 0.20 μm to 3.00 μm. Furthermore, 0.50 μm
When the thickness is up to 1.50 μm, more effects can be obtained.
If the total thickness of the cladding layer is small, the confinement effect becomes weak, and if the total thickness is large, the element resistance increases and the crystallinity also decreases, which is not preferable. In particular, when the average Al composition is 0.1.
In the case of 05 to 0.10, the total thickness of the cladding layer is 0.50
μm to 3.00 μm, average Al composition is 0.10 to 0.2
In the case of 0, the total thickness of the cladding layer is 0.50 μm to 2.5
When the average Al composition is 0 μm and the average Al composition is 0.20 to 0.30, the effect appears when the total thickness of the cladding layer is 0.05 μm to 1.50 μm.

In the present embodiment, the n-type cladding layer is made of Al
_ny Ga _1-ny N (ny ≦ 1) thin film and Al _nz Ga _1-nz N
(0.005 ≦ nz <ny) thin film, and the p-type cladding layer is made of Al _py Ga _1-py N (py ≦ 1) thin film and Al
_pz Ga _1-pz N constituted by (0.005 ≦ pz <py) thin film, and the Al _ny Ga _1-ny N thin film and Al _py Ga _1-py N thickness of the thin film with the same, Al _nz Ga _1-nz N thin film and Al _pz Ga _1-pz
The thickness of the N thin film was the same, but the thickness of the Al _ny Ga _1-ny N thin film was different from the thickness of the Al _py Ga _1-py N thin film, or the thickness of the Al _nz Ga _1-nz N thin film was It has been confirmed that the effect is exhibited even in devices having a configuration in which the thickness of the Al _pz Ga _1-pz N thin film is different. In the present embodiment, (n
y) = (py) and (nz) = (pz), but (n
y) and (py) are different, or (nz) and (p)
It has been confirmed that the effect is exhibited even in the elements having different configurations of z). In addition, it has been confirmed that the effect is exhibited also in an element having a configuration in which the Al composition is different between the n-type cladding layer and the p-type cladding layer.

The layers constituting the cladding layer are not limited to two types, but in terms of the order, the Al _y Ga _{1 -y} N thin film (0 <y <1), followed by the Al _z Ga _{1 -z} N thin film (0 <z ≦
If the relationship of stacking y) is maintained, the film thickness, Al
A combination of three or more kinds of thin films having different compositions and doping concentrations is also possible, and the effect has actually been confirmed.

When a c-plane substrate is used, the direction perpendicular to the substrate surface (the direction in which the crystals are stacked) and the c-axis of the growth substrate are set to 0.10.
When it is shifted by 0.2 to 0.25 °, more preferably 0.1 °
It has been confirmed that when the angle is shifted by 5 ° to 0.20 °, the flatness of the growth surface is promoted, the crystallinity of the entire device is improved, and the characteristics of the active layer are further improved.

In this embodiment, an example in which a sapphire substrate having a (0001) plane is used has been described. However, a sapphire substrate having another plane, GaN, SiC, spinel, mica, or the like can be used. It has been confirmed that the same effects as those of the embodiment appear.

When GaN is used as the substrate, it is not necessary to perform heat treatment in an H ₂ atmosphere and grow the buffer layer at a low temperature, and the temperature is raised by using a carrier gas mainly composed of an inert gas and NH 3. It can be carried out in _three atmospheres and at the same time as the introduction of TMG and / or SiH ₄ from the growth of the underlying GaN film. In this case also, the light emitting device produced has the same effects as the present embodiment.

Further, in this embodiment, the case where a GaN film is grown as a low-temperature buffer layer has been described.
As the low-temperature buffer layer, AlηGa ₁ -ηN (0 ≦ η ≦
Even if 1) is used or ZnO is used, there is no problem in manufacturing a light emitting element, and in each case, the same effect as that of the present embodiment is exhibited.

(Embodiment 4) In the present embodiment, a description will be given of the result of manufacturing a GaN-based compound semiconductor laser diode in which the Al composition of the cladding layer is reduced as approaching the contact layer. A cross-sectional view of a film manufactured by the method of manufacturing a GaN-based compound semiconductor laser diode of the present embodiment is the same as FIG. 1 used for describing the first embodiment. The schematic diagram of the MOCVD apparatus used in the present embodiment is the same as FIG. 2 used for describing the first embodiment.

FIG. 4 is a diagram showing the change over time in the supply amounts of the respective raw materials during the growth of the p-type cladding layer in the method of manufacturing the GaN-based compound semiconductor light emitting device used in the present embodiment.

First, the Al composition of the p-type cladding layer was changed to p-type G
A description will be given of the result of manufacturing a GaN-based compound semiconductor laser diode that is lowered as approaching the aN contact layer.

The growth method is the same as that of the first embodiment except for the time of forming the p-type cladding layer. After the growth of the p-type GaN guide layer, the supply of Cp ₂ Mg was stopped and TMA was reduced to 1
0 μmol / min. Then, an undoped Al _0.16 Ga _0.84 N layer (109b) having a thickness of 4.0 nm was formed, and the supply amount of TMA was 0.7 μmol / min. To
0.20 nmol / min of Cp ₂ Mg. 3. supply;
0nm of Al _0.02 Ga _{0.9 8} N: Mg layer (109c) (a sample thickened (0.4 .mu.m) in the layer same condition S
Mg concentration as measured by IMS = 2E + 20 cm ^-3 )
To form Further, as shown in FIG. 4, the supply amount of Al in the Al-rich mixed crystal layer is gradually reduced so that the Al composition is finally supplied to 0.02. This Al high mixed crystal layer and A
l Repeat the lamination of the low mixed crystal layer 100 times to obtain a thickness of 0.8 μm.
m, n-type cladding layer of composition Al _0.09 Ga _0.91 N (109
a) grow.

Thereafter, the supply of TMA is stopped, TMG and Cp ₂ Mg are supplied, and the p-type GaN contact layer (11
0) is grown 0.5 μm, and after completion, TMG and Cp ₂ Mg
Is stopped, and the substrate heating is terminated. After the growth is over,
The grown crystal was processed in the same manner as in Embodiment 1 to produce a laser device.

When the characteristics of this laser device were measured,
Laser continuous oscillation with high luminous efficiency was obtained at a low threshold. Input power at room temperature with light output of 35 mW: 191.6 m
It was W, and it was confirmed that the light emission characteristics were improved as compared with a device in which the Al composition of the Al-rich mixed crystal layer of the p-type cladding layer was not changed. Further, the life characteristics were also improved.

This is because the Al composition of the cladding layer is made smaller as approaching the contact layer, so that the carrier composition and the electrical characteristics are largely changed from the cladding layer to the contact layer as in the prior art. It is considered that the relationship between the input power and the optical output became better.

It has been confirmed that the device characteristics are improved by decreasing the Al composition of the p-type cladding layer as it approaches the p-type guide layer. The p-type cladding layer Al
It has been confirmed that reducing the composition as it approaches the p-type contact layer and the guide layer further improves the light emission characteristics and the life characteristics of the device.

Also in the n-type cladding layer, the Al composition is changed to n
It has been confirmed that the device characteristics are improved by decreasing the size as it approaches the mold contact layer. It has been confirmed that the device characteristics are improved by reducing the Al composition as it approaches the guide layer. In addition, A of the n-type cladding layer
It has been confirmed that the element characteristics are further improved by decreasing the l-composition as it approaches the n-type contact layer and the guide layer. Also, it has been confirmed that by performing this operation on both the n-type cladding layer and the p-type cladding layer, the element characteristics are further improved.

In the present embodiment, for both the n-type cladding layer and the p-type cladding layer, an Al _y Ga _{1 -yN} (y ≦ 1) thin film and an Al _z Ga ₁ -zN (0.005 ≦ z < y) A thin film and a thin film are alternately stacked, but only one of the n-type and p-type cladding layers is formed of Al _y Ga _1-y N (y ≦
1) As a structure in which thin films and Al _z Ga _{1 -z} N (0.005 ≦ z <y) thin films are alternately stacked, the crystallinity of the device and the improvement of characteristics can be improved by manipulating the Al composition. The effect has been confirmed.

The Al composition ratio y of the thin film is 0.05 ≦ y ≦
It is effective when 0.40, more preferably 0.10 ≦ y ≦ 0.30, and z is effective when 0.005 ≦ z ≦ 0.1, more preferably 0.005 ≦ z ≦ 0.05. Also, y-
The range of z is effective when 0.05 ≦ yz ≦ 0.39, and more preferably 0.10 ≦ yz ≦ 0.39.

The thickness of the thin film constituting the cladding layer is preferably 3.0 nm to 50.0 nm, more preferably 3.0 nm to 10.0 nm, and it has been confirmed that the effect of improving the crystallinity is more apparent. I have.

The average Al compositions (M (Al)) of the n-type cladding layer and the p-type cladding layer are both 0.05 ≦ M (A
l) ≦ 0.30 produces an effect. Further, when 0.07 ≦ M (Al) ≦ 0.20, the effect is more enhanced. If it is low, the confinement effect becomes weak, and if it is high, the crystallinity decreases, which is not preferable.

The effect is exhibited when the total thickness of each of the n-type cladding layer and the p-type cladding layer is 0.20 μm to 3.00 μm. Furthermore, 0.50 μm
When the thickness is up to 1.50 μm, more effects can be obtained.
If the total thickness of the cladding layer is small, the confinement effect becomes weak, and if the total thickness is large, the element resistance increases and the crystallinity also decreases, which is not preferable. In particular, when the average Al composition is 0.1.
In the case of 05 to 0.10, the total thickness of the cladding layer is 0.50
μm to 3.00 μm, average Al composition is 0.10 to 0.2
In the case of 0, the total thickness of the cladding layer is 0.50 μm to 2.5
When the average Al composition is 0 μm and the average Al composition is 0.20 to 0.30, the effect appears when the total thickness of the cladding layer is 0.05 μm to 1.50 μm.

When a c-plane substrate is used, the direction perpendicular to the substrate surface (the direction in which crystals are stacked) and the c-axis of the growth substrate are set to 0.10.
When it is shifted by 0.2 to 0.25 °, more preferably 0.1 °
It has been confirmed that when the angle is shifted by 5 ° to 0.20 °, the flatness of the growth surface is promoted, the crystallinity of the entire device is improved, and the characteristics of the active layer are further improved.

In this embodiment, an example in which a sapphire substrate having a (0001) plane is used has been described. However, a sapphire substrate having another plane, GaN, SiC, spinel, mica, or the like can be used. It has been confirmed that the same effects as those of the embodiment appear.

When GaN is used as the substrate, it is not necessary to perform heat treatment in an H ₂ atmosphere and grow the buffer layer at a low temperature, and the temperature is raised by using a carrier gas mainly composed of an inert gas and NH 3. It can be carried out in _three atmospheres and at the same time as the introduction of TMG and / or SiH ₄ from the growth of the underlying GaN film. In this case also, the light emitting device produced has the same effects as the present embodiment.

In this example, the case where a GaN film was grown as the low-temperature buffer layer was described. However, even if AlηGa _1- ηN (0 ≦ η ≦ 1) was used as the low-temperature buffer layer, ZnO was further used. In any case, there is no problem in manufacturing the light emitting element, and in each case, the same effect as that of the present embodiment is exhibited.

(Embodiment 5) In this embodiment, a description will be given of the result of producing a GaN-based compound semiconductor laser diode by introducing a growth interruption during the growth of a cladding layer. A cross-sectional view of a film manufactured by the method of manufacturing a GaN-based compound semiconductor laser diode of the present embodiment is the same as FIG. 1 used for describing the first embodiment.

The schematic view of the MOCVD apparatus used in the present embodiment is the same as that shown in FIG. 2 used for describing the first embodiment. FIG. 5 is a diagram showing a change over time in the supply amount of each raw material during the growth of each clad layer in the method for manufacturing a GaN-based compound semiconductor light emitting device used in the present embodiment.

The growth method was as follows, except when each clad layer was formed.
This is the same method as in the first embodiment. As shown in FIG.
The method of manufacturing the n-type cladding layer (104a) is as follows.
GaN contact layer (103) growth (n-type GaN core)
Contact layer growth time (501)), TMG, SiH_Four
Supply is stopped and N_TwoAnd NH_ThreeSink only
(Time of growth interruption (502)), and then TMA is increased by 10
μmol / min. , TMG at 50 μmol / min.
To form an n-type cladding layer having a thickness of 4.0 nm.
Undoped Al_0.16Ga_0.84Forming an N layer (104b)
(Undoped Al constituting the cladding layer_0.16Ga_0.84N
Layer growth time (503)), followed by TMA, TMG
The supply is stopped and N_TwoAnd NH_ThreeSink only
Long interruption time (502)), and then add TMG to 50 μmo
1 / min. , SiH_Four5.0 nmol / min. Offering
To form a 4.0 nm n-type cladding layer_0.02
Ga _0.98N: forming a Si layer (104c) (cladding)
Al constituting the layer_0.02Ga_{0. 98}N: growth time of Si layer
(504)). Then, TMG, SiH_FourSupply stopped
And for 12 seconds, N_TwoAnd NH_ThreeShedding only (at the time of growth interruption
(502)), and then TMA was added at 10 μmol / mi.
n. , TMG at 50 μmol / min. Supply the thickness
Undoped Al constituting 4.0 nm n-type cladding layer
_0.16Ga_0.84Form N layer (104b) (cladding layer
Undoped Al_0.16Ga_0.84N layer growth time
(503)). This operation is repeated until the thickness of 0.4 μm
A n-type cladding layer (104a) is grown. After this, n-type
A GaN guide layer (105) is grown.

Manufacturing method of p-type cladding layer (109a)
Means that after growth of the p-type GaN guide layer (108),
p_TwoThe supply of Mg was stopped, and N was_TwoAnd NH_Threeonly
(Time of growth interruption (502)), and then TMA
Is 10 μmol / min. , TMG at 50 μmol / m
in. To form a p-type cladding layer having a thickness of 4.0 nm.
Undoped Al_0.16Ga_0.84N layer (109b)
Formed (undoped Al constituting the cladding layer)_0.16Ga
_0.84N layer growth time (503)), then TMA, T
The supply of MG is stopped, and N_TwoAnd NH_ThreeFlow only
(Time of growth interruption (502)), and TMG
0 μmol / min. , Cp_Two0.20 nmol of Mg
/ Min. Supply to form a 4.0 nm p-type cladding layer
Al_{0. 02}Ga_0.98N: forming a Mg layer (109c)
(Al constituting the cladding layer_0.02Ga_0.98N: Mg layer
Growth time (504)). Then, TMG, Cp_TwoMg
Supply is stopped and N_TwoAnd NH_ThreeSink only
(Time of growth interruption (502)), and then TMA is increased by 10
μmol / min. , TMG at 50 μmol / min.
To form a p-type cladding layer having a thickness of 4.0 nm.
Undoped Al_0.16Ga _0.84Form N layer (109b)
(Undoped Al constituting the cladding layer_0.16Ga_0.84
(N layer growth time (503)). Repeat this operation until the thickness
A 0.4 μm-thick p-type cladding layer (109a) is grown.
You. Thereafter, a p-type GaN contact layer (110) is grown.
Let it. After the growth is completed, the growth is performed in the same manner as in the first embodiment.
The long crystal was processed to produce a laser device.

When the characteristics of this laser device were measured,
Laser continuous oscillation with high luminous efficiency was obtained at a low threshold. The operating current at room temperature with an optical output of 35 mW is 47.8 m.
A, operating voltage is 3.8V (input power: 181.6mW)
Thus, it can be seen that the performance of the element is significantly improved as compared with the first embodiment.

This is because, after the layers constituting the cladding layer have been grown,
Exposure to heat in an atmosphere of N ₂ and NH ₃ for a certain period of time promotes surface flatness of each layer due to migration of surface atoms and the like, and the interface becomes steep. As a result,
It is considered that a laser having a low threshold value and a high luminous efficiency was obtained by improving the crystallinity of the entire device. The interruption of the growth is preferably from 1 second to 10 minutes. If the interruption time is too short, the effect of expelling the gas decreases, and if the interruption time is too long, the growth surface becomes rough due to re-evaporation or the like, which is not preferable.

In this embodiment, N ₂ and NH ₃ are used as the atmosphere gas during the interruption of the growth. However, it was confirmed that the same effect as in this embodiment can be obtained by using only N _2. ing.

The Al composition ratio y of the thin film is 0.05 ≦ y ≦
It is effective when 0.40, more preferably 0.10 ≦ y ≦ 0.30, and z is effective when 0.005 ≦ z ≦ 0.1, more preferably 0.005 ≦ z ≦ 0.05. Also, y-
The range of z is effective when 0.05 ≦ yz ≦ 0.39, and more preferably 0.10 ≦ yz ≦ 0.39.

The thickness of the thin film constituting the cladding layer is preferably from 3.0 nm to 50.0 nm, more preferably from 3.0 to 10.0 nm, and it has been confirmed that the effect of improving the crystallinity appears. I have.

The average Al compositions (M (Al)) of the n-type cladding layer and the p-type cladding layer are both 0.05 ≦ M (A
l) ≦ 0.30 produces an effect. Further, when 0.07 ≦ M (Al) ≦ 0.20, the effect is more enhanced. If it is low, the confinement effect becomes weak, and if it is high, the crystallinity decreases, which is not preferable.

The effect is exhibited when the total thickness of each of the n-type cladding layer and the p-type cladding layer is 0.20 μm to 3.00 μm. Furthermore, 0.50 μm
When the thickness is up to 1.50 μm, more effects can be obtained.
If the total thickness of the cladding layer is small, the confinement effect becomes weak, and if the total thickness is large, the element resistance increases and the crystallinity also decreases, which is not preferable. In particular, when the average Al composition is 0.1.
In the case of 05 to 0.10, the total thickness of the cladding layer is 0.50
μm to 3.00 μm, average Al composition is 0.10 to 0.2
In the case of 0, the total thickness of the cladding layer is 0.50 μm to 2.5
When the average Al composition is 0 μm and the average Al composition is 0.20 to 0.30, the effect appears when the total thickness of the cladding layer is 0.05 μm to 1.50 μm.

In this embodiment, the n-type cladding layer is made of Al
_ny Ga _1-ny N (ny ≦ 1) thin film and Al _nz Ga _1-nz N
(0.005 ≦ nz <ny) thin film, and the p-type cladding layer is made of Al _py Ga _1-py N (py ≦ 1) thin film and Al
_pz Ga _1-pz N constituted by (0.005 ≦ pz <py) thin film, and the Al _ny Ga _1-ny N thin film and Al _py Ga _1-py N thickness of the thin film with the same, Al _nz Ga _1-nz N thin film and Al _pz Ga _1-pz
The thickness of the N thin film was the same, but the thickness of the Al _ny Ga _1-ny N thin film was different from the thickness of the Al _py Ga _1-py N thin film, or the thickness of the Al _nz Ga _1-nz N thin film was It has been confirmed that the effect is exhibited even in devices having a configuration in which the thickness of the Al _pz Ga _1-pz N thin film is different. In the present embodiment, (n
y) = (py) and (nz) = (pz), but (n
y) and (py) are different, or (nz) and (p)
It has been confirmed that the effect is exhibited even in the elements having different configurations of z). In addition, it has been confirmed that the effect is exhibited also in an element having a configuration in which the Al composition is different between the n-type cladding layer and the p-type cladding layer.

In this embodiment, both the n-type cladding layer and the p-type cladding layer are made of an Al _y Ga _{1 -yN} (y ≦ 1) thin film and an Al _z Ga ₁ -zN (0.005 ≦ z < y) A thin film and a thin film are alternately stacked, but only one of the n-type and p-type cladding layers is formed of Al _y Ga _1-y N (y ≦
1) As a structure in which a thin film and an Al _z Ga _{1 -z} N (0.005 ≦ z <y) thin film are alternately stacked, the crystallinity and characteristics of the device can be improved by operating the growth interruption. The effect has been confirmed.

The layers constituting the cladding layer are not limited to two types, but in terms of the order, the Al _y Ga _{1 -y} N thin film (0 <y <1), followed by the Al _z Ga _{1 -z} N thin film (0 <z ≦
If the relationship of stacking y) is maintained, the film thickness, Al
A combination of three or more kinds of thin films having different compositions and doping concentrations is also possible, and the effect has actually been confirmed.

When a c-plane substrate is used, the direction perpendicular to the substrate surface (the direction in which crystals are stacked) and the c-axis of the growth substrate are set to 0.10.
When it is shifted by 0.2 to 0.25 °, more preferably 0.1 °
It has been confirmed that when the angle is shifted by 5 ° to 0.20 °, the flatness of the growth surface is promoted, the crystallinity of the entire device is improved, and the characteristics of the active layer are further improved. In this embodiment, an example in which a sapphire substrate having a (0001) plane is used has been described. However, a sapphire substrate having another plane, GaN, SiC, spinel, mica, or the like can be applied. It has been confirmed that the same effect as described above appears.

When GaN is used as the substrate, it is not necessary to perform heat treatment in an H ₂ atmosphere and grow the buffer layer at a low temperature, and the temperature is raised by using a carrier gas mainly composed of an inert gas and NH 3. It can be carried out in _three atmospheres and at the same time as the introduction of TMG and / or SiH ₄ from the growth of the underlying GaN film. In this case also, the light emitting device produced has the same effects as the present embodiment.

In this example, the case where a GaN film was grown as the low-temperature buffer layer was described. However, even if AlηGa _1- ηN (0 ≦ η ≦ 1) was used as the low-temperature buffer layer, ZnO was further used. In any case, there is no problem in manufacturing the light emitting element, and in each case, the same effect as that of the present embodiment is exhibited.

(Embodiment 6) In this embodiment, a GaN substrate is used as a growth substrate, and G is applied to the present invention.
The result of fabricating an aN-based compound semiconductor laser diode will be described.

FIG. 6 shows a GaN-based compound according to the present embodiment.
Conductor Laser Diode Fabrication Method
It is sectional drawing. N-type GaN substrate (601)
And an n-type GaN layer (602) and an n-type
A doped layer (603a) is formed. This n-type cladding layer
(603) is an undoped A constituting the n-type cladding layer.
l_0.16Ga_0.84N thin film (603b) and n-type cladding layer
Constituting Al_0.02Ga_{0. 98}N: Si thin film (603c)
Is formed. On the n-type cladding layer (603a),
n-type GaN guide layer (604), active layer (605), A
lGaN evaporation prevention layer (606), p-type GaN guide layer
(607), a p-type cladding layer (608a) is formed
You. This p-type cladding layer (608a)
Undoped Al constituting the layer_0.16Ga_0.84N thin film (60
8b) and Al constituting the p-type cladding layer _0.02Ga
_0.98N: formed of a Mg thin film (608c). p-type club
P-type GaN contact layer on the pad layer (608a)
(609) is formed, and after crystal growth, SiO_TwoInsulation
Membrane (610), p-type electrode (611a), n-type electrode (61
1b) is formed. MOCV used in this embodiment
The schematic diagram of the D apparatus is the same as FIG. 2 used for describing the first embodiment.
They are the same.

N-type G having (0001) plane as substrate
A GaN-based compound semiconductor layer is grown using an aN substrate. In the drawing, (601) is an n-type G having a (0001) plane.
aN substrate, and this substrate is a susceptor (20
2) Located above. A resistance heating heater also made of carbon is arranged in the susceptor, and the substrate temperature can be controlled by a thermocouple. (203)
Is a reaction tube made of double quartz, which is water-cooled.
NH ₃ (206) was used as a group V raw material, and III
Group materials include TMG (207a) and TMA (207a).
b), TMI (207c) was used by bubbling with N ₂ or H ₂ (210). Also, SiH ₄ (209) was used as an n-type doping material, and Cp ₂ Mg (207d) was used as a p-type doping material.
Each raw material is precisely controlled in flow rate by a mass flow controller (208) to control N ₂ or H ₂ (21
0), introduced into the reaction tube through the raw material inlet (204), and discharged from the exhaust gas outlet (205).

First, the n-type GaN substrate (601) is washed and set in a crystal growth apparatus. The substrate was heated to 1050 ° C. in an NH ₃ atmosphere, and TMG was added at 50 μmol / mi.
n. And SiH ₄ gas at 10 nmol / min. Then, the n-type GaN layer (602) is grown by 4 μm. Next, Si
The supply of H ₄ gas was stopped, and TMA was reduced to 10 μmol / mi.
n. Supplied, the thickness of undoped Al _0.16 Ga _0.84 to form a N thin film (603b) constituting the n-type cladding layer of 4.0 nm, further SiH ₄ gas 5.0nmol / min.
And the supply amount of TMA was 1.5 μmol / min. To form an n-type cladding layer having a thickness of 4.0 nm.
_{A 0.02} Ga _0.98 N: Si thin film (603c) (Si concentration when this layer is thickened (0.4 μm) under the same conditions and measured by SIMS = 3E + 18 cm ⁻³ ) is formed. This operation was repeated 100 times, and the thickness was 0.80 μm,
An n-type cladding layer having an average composition of Al _0.09 Ga _0.91 N (603)
a) grow.

Next, the supply of TMA was stopped, and 0.1 μm
Manufacturing (604) of an n-type GaN guide layer having a thickness is performed. n
SiH ₄ and TMG after growing GaN guide layer (604)
Is stopped, the temperature of the substrate is reduced to 730 ° C.,
When the temperature is stabilized, TMG is added at 10 μmol / min. ,
TMI of 10 μmol / min. Supplied with In _0.05 G
An active layer barrier layer of a _0.95 N was grown to a thickness of 5 nm. At the time of the active layer growth, 10n the SiH ₄
mol / min. It may flow to the extent. Thereafter, TMG was added at 10 μmol / min. , TMI is 50 μmol / mi
n. Then, a well layer of an active layer made of In _0.2 Ga _0.8 N was grown to a thickness of 3 nm. After that, TMI
Is 10 μmol / min. To In _0.05 Ga _0.95
A barrier layer of an active layer made of N was grown to a thickness of 5 nm. The growth of the barrier layer serving as the active layer and the well layer is repeated, and after the growth of three multiple quantum wells, the barrier layer is finally grown to complete the growth of the active layer (605). After the growth of the active layer, TMG was added at 10 μmol / min. For the purpose of preventing the release of In from the InGaN film. , TMA 5 μm
ol / min. , And Cp ₂ Mg at 0.20 nmol /
min. Then, a p-type AlGaN anti-evaporation layer (606) having a thickness of 30 nm is grown. After that, TMG, TM
A, supply of Cp ₂ Mg was stopped, and the substrate temperature was set to 105 again.
Heat to 0 ° C. After raising the temperature, TMG was added at 50 μmol / mi.
n. And Cp ₂ Mg, and the p-type GaN guide layer (60
7) is grown 0.1 μm.

Next, the supply of Cp ₂ Mg was stopped, and TM
A at 10 μmol / min. Undoped Al _0.16 Ga _0.84 supplied to form a 4.0 nm thick p-type cladding layer
N thin film (608b) was formed, and the supply amount of TMA was 1.5 μmol / min. And change Cp ₂ Mg to 0.2
0 nmol / min. The Al _0.02 Ga _0.98 N: Mg thin film (608
c) (Mg concentration = 2E + 20 when this layer was thickened (0.4 μm) under the same conditions and measured by SIMS)
cm ^-3 ). This operation is repeated 100 times to grow a p-type cladding layer (608a) having a thickness of 0.80 μm and an average composition of Al _0.09 Ga _0.91 N. After the growth is over, TMA
Is stopped, TMG and Cp ₂ Mg are supplied, and p-type G
The aN contact layer (609) is grown to a thickness of 0.5 μm, and after completion, the supply of TMG and Cp ₂ Mg is stopped to end the substrate heating.

Next, this grown film was subjected to photolithography and dry etching techniques to make GaN-based crystals <1--1.
100> direction, the p-type cladding layer (60
8a) Etching up to the surface, width 30 μm, length 60
0 μm mesa type, SiO ₂ insulating film (610) is formed on the p-type GaN contact layer, and n-type GaN
An n-type electrode (611b) made of Ti and Al was formed on the substrate, and a p-type electrode (611a) of Pd and Au having a width of 2 μm and a length of 600 μm was formed on the surface of the p-type GaN contact layer.

Next, a 650 μm long laser resonator was formed by cleaving the GaN-based crystal on the (1-100) plane. A dielectric multilayer film of titanium oxide and magnesium fluoride having a reflectivity of 70% is formed on the back end face, and a silicon nitride film having a reflectivity of 12% is formed on the front end face. Then, a laser device was manufactured.

When the characteristics of the laser device thus manufactured were measured, the operating current at room temperature with an optical output of 35 mW was 46.4 mA, and the operating voltage was 3.8 V. This value is better than when sapphire is used as the substrate. By applying the present invention and using GaN as a substrate, a layer containing Al and a layer not containing Al of the conventional method are alternately laminated, and compared with a device in which a clad layer is produced. This is considered to be due to the fact that defects caused by the difference in lattice constant and coefficient of thermal expansion are further reduced, and the luminous efficiency of the active layer is greatly increased. In addition, the life characteristics have also been improved, which is considered to be due to the fact that the diffusion of the dopant was suppressed as the number of defects decreased. In addition, the use of a GaN substrate eliminates the need for an etching step for forming an n-electrode, and the cleavage direction of the substrate and the device is the same.
Chips are easily cut out, and the yield is greatly improved.

The Al composition ratio y of the thin film is 0.05 ≦ y ≦
It is effective when 0.40, more preferably 0.10 ≦ y ≦ 0.30, and z is effective when 0.005 ≦ z ≦ 0.1, more preferably 0.005 ≦ z ≦ 0.05. Also, y-
The range of z is effective when 0.05 ≦ yz ≦ 0.39, and more preferably 0.10 ≦ yz ≦ 0.39.

The thickness of the thin film constituting the cladding layer is preferably from 3.0 nm to 50.0 nm, more preferably from 3.0 to 10.0 nm, and it has been confirmed that the effect of improving the crystallinity appears. I have.

The average Al compositions (M (Al)) of the n-type cladding layer and the p-type cladding layer are both 0.05 ≦ M (A
l) ≦ 0.30 produces an effect. Further, when 0.07 ≦ M (Al) ≦ 0.20, the effect is more enhanced. If it is low, the confinement effect becomes weak, and if it is high, the crystallinity decreases, which is not preferable.

The effect is exhibited when the total thickness of each of the n-type cladding layer and the p-type cladding layer is 0.20 μm to 3.00 μm. Furthermore, 0.50 μm
When the thickness is up to 1.50 μm, more effects can be obtained.
If the total thickness of the cladding layer is small, the confinement effect becomes weak, and if the total thickness is large, the element resistance increases and the crystallinity also decreases, which is not preferable. In particular, when the average Al composition is 0.1.
In the case of 05 to 0.10, the total thickness of the cladding layer is 0.50
μm to 3.00 μm, average Al composition is 0.10 to 0.2
In the case of 0, the total thickness of the cladding layer is 0.50 μm to 2.5
When the average Al composition is 0 μm and the average Al composition is 0.20 to 0.30, the effect appears when the total thickness of the cladding layer is 0.05 μm to 1.50 μm.

In this embodiment, the n-type cladding layer is made of Al
_ny Ga _1-ny N (ny ≦ 1) thin film and Al _nz Ga _1-nz N
(0.005 ≦ nz <ny) thin film, and the p-type cladding layer is made of Al _py Ga _1-py N (py ≦ 1) thin film and Al
_pz Ga _1-pz N constituted by (0.005 ≦ pz <py) thin film, and the Al _ny Ga _1-ny N thin film and Al _py Ga _1-py N thickness of the thin film with the same, Al _nz Ga _1-nz N thin film and Al _pz Ga _1-pz
The thickness of the N thin film was the same, but the thickness of the Al _ny Ga _1-ny N thin film was different from the thickness of the Al _py Ga _1-py N thin film, or the thickness of the Al _nz Ga _1-nz N thin film was It has been confirmed that the effect is exhibited even in devices having a configuration in which the thickness of the Al _pz Ga _1-pz N thin film is different. In the present embodiment, (n
y) = (py) and (nz) = (pz), but (n
y) and (py) are different, or (nz) and (p)
It has been confirmed that the effect is exhibited even in the elements having different configurations of z). In addition, it has been confirmed that the effect is exhibited also in an element having a configuration in which the Al composition is different between the n-type cladding layer and the p-type cladding layer.

In this embodiment, both the n-type cladding layer and the p-type cladding layer are made of an Al _y Ga _{1 -yN} (y ≦ 1) thin film and an Al _z Ga ₁ -zN (0.005 ≦ z < y) A thin film and a thin film are alternately laminated, but only one side of the n-type cladding layer or the p-type cladding layer
_y Ga _1-y N (y ≦ 1) thin film and Al _z Ga _1-z N (0.0
05 ≦ z <y) Even in the case of a structure in which thin films are alternately stacked, the effect of improving the crystallinity and characteristics of the element has been confirmed.

The layers constituting the cladding layer are not limited to two kinds, and the order is not limited, and the order of the order is Al _y Ga _{1 -y} N thin film (0 <y <1), then Al _z Ga _{1 -z} N thin film. (0 <z ≦
If the relationship of stacking y) is maintained, the film thickness, Al
A combination of three or more kinds of thin films having different compositions and doping concentrations is also possible, and the effect has actually been confirmed.

When a c-plane substrate is used, the c-axis of the growth substrate deviates from the vertical direction of the substrate surface (the direction of crystal lamination) by 0.10 ° to 0.25 ° as in the case of the sapphire substrate. In this case, more preferably, when the angle is shifted by 0.15 ° to 0.20 °, the flatness of the growth surface is promoted, the crystallinity of the entire device is improved, and the characteristics of the active layer are further improved. Make sure that.

In this embodiment, an example in which a GaN substrate having a (0001) plane is used has been described. However, a GaN substrate having another plane, SiC which can be easily made conductive, or the like can be applied. It has been confirmed that the same effect as described above appears. In addition, it has been confirmed that the same effect as that of the present embodiment can be obtained when the configuration of the element layers is reversed using the p-type GaN substrate.

When GaN is used as the substrate, it is not necessary to perform heat treatment in an H ₂ atmosphere and grow the buffer layer at a low temperature, and the temperature is raised by using a carrier gas mainly composed of an inert gas and NH 3. It can be carried out in _three atmospheres and at the same time as the introduction of TMG and / or SiH ₄ from the growth of the underlying GaN film. In this case also, the light emitting device produced has the same effects as the present embodiment.

In this embodiment, the case where a GaN film is grown as the low-temperature buffer layer has been described. However, even if AlηGa _1- ηN (0 ≦ η ≦ 1) is used as the low-temperature buffer layer, ZnO is further used. In any case, there is no problem in manufacturing the light emitting element, and in each case, the same effect as that of the present embodiment is exhibited.

Further, _Alny G forming the n-type cladding layer
The carbon concentration C (ny) of the a _1-ny N (ny ≦ 1) thin film is
5E + 15 (current detection limit value) to 1E + 19 cm ^-3 when 0.40 <ny ≦ 1, 5 when ny ≦ 0.40
E + 15 to 1E + 18 cm ^-3 is desirable. Al _nz Ga
The carbon concentration C (nz) of the _1-nz N (nz ≦ 1) thin film is 0.5.
5E + 15 in the entire range of 005 <nz ≦ ny
１1E + 19 cm ⁻³ is desirable. In particular, 0.40 <ny
If ≤1, C (nz) is 5E + 15E + 18cm
^-3 , when ny ≦ 0.40, C (nz) is 5E + 15
It is preferably 5E + 18 cm ^-3 .

Further, Al _py G forming the p-type cladding layer
The carbon concentration C (py) of the a _1-py N (py ≦ 1) thin film is
5E + 15 (current detection limit value) to 1E + 19 cm ^-3 when 0.40 <py ≦ 1, and 5 when py ≦ 0.40
E + 15 to 1E + 18 cm ^-3 is desirable. Al _pz Ga
The carbon concentration C (pz) of the _1-pz N (pz ≦ 1) thin film is 0.1.
5E + 15 in all ranges of 005 <pz ≦ py
１1E + 19 cm ⁻³ is desirable. In particular, 0.40 <py
When ≤1, C (pz) is 5E + 15E + 18cm
^-3 , when py ≦ 0.40, C (pz) is 5E + 15
It is preferably 5E + 18 cm ^-3 . It has been confirmed that if the carbon concentration is too low or too high, the crystallinity of the semiconductor decreases, the element resistance increases, and it becomes difficult to make the semiconductor device n-type or p-type. .

Also, _Alny G constituting the n-type cladding layer
a _1-ny N (ny ≦ 1) thin film dopant concentration C (dn
y) is preferably 5E + 19 cm ^-3 or less. C (dn
If y) is too high, the crystallinity decreases, which is not desirable. Al
_{nz Ga 1-nz N (0.005} ≦ pz <py) dopant concentration of the thin film C (dnz) is, 1E + 17~1E + 19cm
^-3 is preferred. If C (dnz) is too high, the crystallinity decreases, and if it is too low, the resistance increases, which is not preferable.

Further, Al _py G forming the p-type cladding layer
a _1-py N (py ≦ 1) Dopant concentration C (dp
y) is preferably 5E + 20 cm ^-3 or less. C (dp
If y) is too high, the crystallinity decreases, which is not desirable. Al
_{pz Ga 1-pz N (0.005} ≦ pz <py) of the thin film dopant concentration C (DPZ) is, 1E + 18~1E + 19cm
^-3 is preferred. If C (dpz) is too high, the crystallinity decreases, and if it is too low, the resistance increases, which is not preferable.

[0181]

As described above, by applying the present invention, a GaN-based compound semiconductor light-emitting device having high luminous efficiency can be manufactured with good in-plane uniformity.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a light emitting device manufactured by a method for manufacturing a GaN-based compound semiconductor laser diode according to Embodiments 1, 2, 4, and 5.

FIG. 2 is a schematic view of an MOCVD apparatus used for manufacturing a GaN-based compound semiconductor of the present invention.

FIG. 3 is a cross-sectional view of a light-emitting element manufactured by a method of manufacturing a GaN-based compound semiconductor laser diode according to a third embodiment.

FIG. 4 is a diagram showing a change over time in supply amounts of respective raw materials during growth of a p-type cladding layer in a method for manufacturing a GaN-based compound semiconductor light emitting device according to a fourth embodiment.

FIG. 5 is a diagram showing a change over time in the supply amount of each raw material at the time of growing each clad layer in the method for manufacturing a GaN-based compound semiconductor light emitting device of the fifth embodiment.

FIG. 6 is a cross-sectional view of a light-emitting element manufactured by a method for manufacturing a GaN-based compound semiconductor laser diode according to a sixth embodiment.

FIG. 7 shows Al _0.16 Ga _0.84 N forming an n-type cladding layer.
Thin film, thickness of Al _0.02 Ga _0.98 N thin film and light output 35mW
FIG. 4 is a diagram showing a relationship between the power and the input power at room temperature.

FIG. 8 is a diagram showing the relationship between the Al composition y1 of the Al _y1 Ga _1-y1 N thin film forming the n-type cladding layer and the input power at room temperature with an optical output of 35 mW.

[Explanation of symbols]

Reference Signs List 101 sapphire substrate 102 GaN buffer layer 103 n-type GaN contact layer 104a n-type cladding layer 104b undoped Al constituting n-type cladding layer
_0.16 Ga _0.84 N layer or undoped Al _0.20 Ga _0.80 N layer constituting the n-type cladding layer 104 c Al _0.02 Ga _0.98 constituting the n-type cladding layer
N: Al _0.04 G constituting a Si layer or an n-type cladding layer
a _0.96 N: Si layer 105 n-type GaN guide layer 106 active layer 107 AlGaN evaporation preventing layer 108 p-type GaN guide layer 109a p-type clad layer 109b undoped Al constituting p-type clad layer
_0.16 Ga _0.84 N layer 109 c Al _0.02 Ga _0.98 constituting the p-type cladding layer
N: Mg layer 110 p-type GaN contact layer 111 SiO ₂ insulating film 112 a p-type electrode 112 b n-type electrode 202 quartz tray 203 susceptor 204 reaction tube 205 exhaust gas outlet 206 piping 207 exhaust gas treatment device 208 mass flow controller 209 NH ₃ 210 N ₂ Or H ₂ 211a TMG 211b TMA 211c TMI 211d Cp ₂ Mg 212 SiH ₄ 304a1 First n-type cladding layer 304b Undoped Al constituting n-type cladding layer
_0.16 Ga _0.84 N layer 304c Al _0.02 Ga _0.98 constituting n-type cladding layer
N: Si layer 304a2 Second n-type clad layer 313 In _0.1 Ga _0.9 N crack prevention layer 401 Growth time of p-type GaN guide layer 402 Undoped Al _y G forming p-type clad layer
a _1-y N layer growth time 403 Al _z Ga _1-z N: M constituting p-type cladding layer
g layer growth time 404 p-type GaN contact layer growth time 501 n-type GaN contact layer growth time, or p
GaN guide layer growth time 502 Growth interruption time 503 Undoped Al _0.16 constituting n-type cladding layer
Growth time of Ga _0.84 N layer or undoped Al _0.16 Ga _0.84 N layer forming p-type cladding layer 504 Al _0.02 Ga forming n-type cladding layer
Growth time of _0.98 N: Si layer or Al _0.02 Ga _0.98 N: Mg layer constituting p-type cladding layer 505 Growth time of n-type GaN guide layer or p-type G
aN contact layer growth time 601 n-type GaN substrate 602 n-type GaN layer 603a n-type cladding layer 603b undoped Al constituting n-type cladding layer
_0.16 Ga _0.84 N layer, 603 c Al _0.02 Ga _0.98 constituting n-type cladding layer
N: Si layer 604 n-type GaN guide layer 605 active layer 606 AlGaN evaporation preventing layer 607 p-type GaN guide layer 608a p-type clad layer 608b undoped Al constituting p-type clad layer
_0.16 Ga _0.84 N layer 608 cp Al _0.02 Ga _0.98 constituting p-type cladding layer
N: Mg layer 609 p-type GaN contact layer 610 SiO ₂ insulating film 611a p-type electrode 611b n-type electrode

Claims (9)

[Claims] A first cladding layer made of AlGaN; a second cladding layer made of AlGaN;
Having an active layer sandwiched between second cladding layers
In the N-based compound semiconductor light emitting device, the first cladding layer includes an Al _y1 Ga _1-y1 N (y1 ≦ 1) thin film and an Al _z1
A GaN-based compound semiconductor light-emitting device characterized in that Ga _1-z1 N (0.005 ≦ z1 <y1) thin films are alternately stacked. 2. The thickness of the Al _y1 Ga _1-y1 N (y1 ≦ 1) thin film is not less than 3.0 nm and not more than 50 nm;
_{l z1 Ga 1-z1 N (} 0.005 ≦ z1 <y1) thickness of the thin film, GaN-based compound semiconductor light-emitting device according to claim 1, characterized in that at 50nm or less than 3.0 nm. 3. The second cladding layer made of AlGaN includes an Al _y2 Ga _{1- y2} N (y2 ≦ 1) thin film and an Al _z2 G thin film.
The GaN-based compound semiconductor light-emitting device according to claim 1, wherein thin films of a _{1 -z2N} (0.005 ≦ z2 <y2) are alternately stacked. 4. The thickness of the Al _y2 Ga _1-y2 N (y2 ≦ 1) thin film is from 3.0 nm to 50 nm, and the Al _z2 Ga _1-z2 N (0.005 ≦ z2 <y2). 4. The GaN-based compound semiconductor light emitting device according to claim 3, wherein the thickness of the thin film is not less than 3.0 nm and not more than 50 nm. 5. The GaN-based compound semiconductor light emitting device according to claim 1, wherein the first clad layer and the second clad layer have different Al average compositions. 6. The thickness of the Al _y1 Ga _1-y1 N (y1 ≦ 1) thin film and the thickness of the Al _y2 Ga _1-y2 N (y2 ≦ 1) thin film, or the thickness of the Al _z1 Ga _{1 -z1N} (0.0
05 ≦ z1 <y1) Thickness of the thin film and Al _z2 Ga _1-z2 N
6. The GaN according to claim 3, wherein (0.005 ≦ z2 <y2) the thickness of the thin film is different.
Based compound semiconductor light emitting device. 7. The method according to claim 3, wherein y1 and y2 are different, or z1 and z2 are different.
7. The GaN-based compound semiconductor light-emitting device according to any one of items 1 to 6. 8. In one or both of the first cladding layer and the second cladding layer, In _w Ga _{1 -w} N
8. The GaN-based compound semiconductor light-emitting device according to claim 1, wherein a (0 <w <1) film is interposed. 9. The Ga according to claim 1, wherein
The method of manufacturing a N-based compound semiconductor light-emitting element, Al _y
A _first thin film made of Ga _1-y N (y ≦ 1) and Al _z Ga
When forming the AlGaN layer in which the second thin films made of _1-z N (0.005 ≦ z <y) are alternately stacked, a predetermined thickness is formed after the growth of the first thin film or the second thin film. A method for producing a GaN-based compound semiconductor, comprising providing a growth interruption time.