JP2003204120A - Semiconductor laser device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor laser device that is improved in luminous efficiency in a wavelength band of 1.2-1.6 μm for optical communication and reduced in output fluctuation with respect to temperature changes by forming a good-quality GaInAsN active layer in the laser device. <P>SOLUTION: The semiconductor laser device is provided with a GaAs substrate (S) and an Al<SB>x1</SB>Ga<SB>1-x1-y1</SB>In<SB>y1</SB>As<SB>p1</SB>N<SB>q1</SB>P<SB>1-p1-q1</SB>light emitting layer (E) (wherein, 0≤x1≤1, 0≤1-x1-y1≤1, 0<y≤1, 0<p1≤1, and 0<q1≤1) which is on the substrate (S), has an energy band gap of 0.92-1.65 μm in terms of the wavelength of light, and has a larger grating constant than the GaAs has. The light emitting layer (E) contains carbon (C) and an n-type impurity in a state where the content of the n-type impurity is made higher than that of the carbon (C). <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser device, and more particularly to a semiconductor laser device provided with AlGaInAsNP having a larger lattice constant than GaAs formed on a GaAs substrate as an active layer.

[0002]

2. Description of the Related Art In recent years, a GaInAsN crystal grown on a GaAs substrate has been proposed as a new crystal for forming a semiconductor laser device that oscillates in a wavelength range for long wavelength optical communication. However, it is difficult to add a high concentration of nitrogen (N) to the GaInAsN crystal, and it is not easy to realize a bandgap corresponding to light having a wavelength of 1.2 to 1.6 μm used for optical communication. On the other hand, by using a low growth temperature, a GaInAsN crystal having a high nitrogen concentration is grown.

However, the GaInAsN crystal having a high nitrogen concentration formed at a low temperature is significantly inferior in properties such as luminous efficiency to the GaInAsN crystal having a low nitrogen composition grown at a high temperature. Therefore, in order to improve the crystallinity of crystals grown at low temperature, a process of annealing at high temperature after growth has been attempted. However, even if such an attempt is made, it is difficult to obtain the quality of a crystal grown at a high temperature. Especially when the nitrogen concentration exceeds several percent, it is difficult to obtain a good quality crystal.

Therefore, instead of increasing the amount of nitrogen added,
Attempts have also been made to reduce the band gap by increasing the amount of indium (In) added. However, when the concentration of indium is increased, the lattice constant of the GaInAsN layer increases, and the difference in lattice constant from the lattice constant of the GaAs substrate increases. Therefore, for example, Japanese Patent Laid-Open No. 2000-332
As disclosed in Japanese Patent No. 363, it becomes impossible to form a good quality and thick GaInAsN layer due to strain.

[0005]

As described above,
In a semiconductor laser device using GaInAsN formed on a GaAs substrate, there is a problem that crystal quality is deteriorated when nitrogen (N) is added at a high concentration.
On the other hand, when the amount of indium (In) added is increased, GaAs
The lattice mismatch with the substrate becomes large, and high quality and thick GaIn
There is a problem that the AsN layer cannot be grown.

When a semiconductor laser device is produced by using these crystals, there are problems that a laser having a desired oscillation wavelength cannot be obtained, the light output does not increase, and the output sharply decreases as the temperature rises.

The present invention has been made on the basis of the recognition of such a problem, and its purpose is to provide a good quality GaInAsN.
By forming the active layer, the wavelength for optical communication is 1.2μ.
It is an object of the present invention to provide a semiconductor laser device having a high luminous efficiency in the m-1.6 μm band and a small output fluctuation with respect to temperature changes.

[0008]

In order to achieve the above object, a first semiconductor laser device of the present invention is provided on a GaAs substrate and the GaAs substrate and has a wavelength of light of 0.92 μm or more. Al _x1 Ga _1-x1-y1 In _y1 As _p1 N _p1 P having an energy band gap of 0.65 μm or less and a lattice constant larger than that of GaAs.
_1-p1-q1 (0 ≦ x1 ≦ 1, 0 ≦ 1-x1-y1 ≦
1, 0 <y1 ≦ 1, 0 <p1 ≦ 1, 0 <q1 ≦ 1) (0
≦ x1 ≦ 1, 0 ≦ 1-x1-y1 ≦ 1, 0.07 <y1
<0.53, 0 <p1 ≦ 1, 0 <q1 ≦ 1), and the light emitting layer contains carbon (C) and n-type impurities, and contains the n-type impurities. The amount is larger than the content of the carbon (C).

According to the above structure, it is possible to obtain a light emitting layer having a predetermined band gap and good crystallinity while relaxing the lattice mismatch with the GaAs substrate. Moreover, it is possible to suppress the deterioration of the characteristics due to the deep level of carbon (C).

Here, the content of the carbon (C) is 2
When the density is × 10 ¹⁸ cm ⁻³ or more, the lattice mismatch can be relaxed and the concentration of indium (In) can be increased, and long-wavelength light emission can be obtained while maintaining good emission characteristics.

The second semiconductor laser device of the present invention
Is provided on the GaAs substrate and on the GaAs substrate.
And a p-type semiconductor layer doped with a Group II element, and the G
It is provided on the aAs substrate and is 0.92μ in terms of light wavelength.
energy band gap of m to 1.65 μm
Have, Al_x2Ga_1-x2-y2In _y2As_p2N
_p2P_1-p2-q2(0 ≦ x2 ≦ 1, 0 ≦ 1-x2-
y2 ≦ 1, 0 <y2 ≦ 1, 0 <p2 ≦ 1, 0 <q2 ≦
1) a light emitting layer, the p-type semiconductor layer, and the light emission
Al provided between the layers_x3Ga_{1-x3- y3}In
_y3As_p3N_p3P_1-p3-q3(0 ≦ x3 ≦ 1,
0 ≦ 1-x3-y3 ≦ 1, 0 <y3 ≦ 1, 0 <p3 ≦
1, 0 <q3 ≦ 1) and a light guide layer
The light-emitting layer contains carbon (C) and a high concentration of carbon (C).
The n-type impurity, the light guide layer is made of carbon.
(C) and the n-type impurity of higher concentration than this carbon (C)
Content of the carbon (C) contained in the light emitting layer
Is the content of the carbon (C) contained in the light guide layer
It is characterized by being smaller than.

According to the above structure, the p-type semiconductor layer
It is possible to prevent the group II element from diffusing into the light emitting layer, and it is possible to maintain good light emitting characteristics. Furthermore, overflow of carriers to the light guide layer side can be suppressed, and the luminous efficiency can be improved.

In particular, the total value of the concentration of the carbon (C) and the concentration of the n-type impurity contained in the light emitting layer is 5
When it is ^{x10 15} cm ^-3 or more, so-called "kick-off type" diffusion due to the group II element doped in the p-type semiconductor layer can be effectively prevented.

Here, the n-type impurity is silicon (S
It is desirable to use at least one selected from the group consisting of i), sulfur (S) and selenium (Se).

In addition, these semiconductor laser devices have remarkable effects particularly when they emit laser light having a wavelength of 1.2 μm or more and 1.6 μm or less.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a conceptual diagram showing a main part of the semiconductor laser of the present invention. That is, this figure is a cross-sectional view parallel to the resonator of the semiconductor laser device.

The first feature of the semiconductor laser device of the present invention is that Al _x Ga _{1-x y} In _y As _p N _p P having a larger lattice constant on the GaAs substrate S than on the GaAs substrate.
_1-p-q (0≤x, 1-x-y≤1, 0 <y, p, q
≦ 1) is provided with a light emitting layer E, and the light emitting layer E is
This is because carbon (C) and an n-type impurity having a higher concentration than that are contained.

Here, silicon (Si) is most desirable as the n-type impurity contained in the light emitting layer E, but tin (S
n), selenium (Se), sulfur (S), or chlorine (Cl) can also be used.

In this way, the wavelength of 0.92 μm
The light emitting layer E formed on the GaAs substrate S can realize the laser light L having a wavelength band of 1.65 μm, particularly a wavelength of 1.2 μm to 1.6 μm used for long-wavelength optical communication and the like. .

That is, when an AlGaInAsNP-based compound semiconductor is epitaxially grown on a GaAs substrate, in order to set the energy band gap thereof to 0.92 μm in terms of light wavelength, indium (In) composition (total of group III elements is It is necessary to increase the ratio) to 0.09 or more. However, when the indium composition is 0.09 or more, the crystallinity of AlGaInAsNP sharply decreases, and the peak half-width of X-ray diffraction also sharply increases.

FIG. 2 shows the indium concentration of a GaInAsN crystal epitaxially grown on a GaAs substrate.
It is a graph showing the relationship with the half width of the X-ray diffraction peak.

As can be seen from the figure, when the indium composition exceeds 0.09, the half-width of the GaInAsN crystal sharply increases.

On the other hand, according to the present invention, when the band gap is set to 0.92 μm or more, nitrogen is added to reduce the amount of indium added and alleviate the deterioration of crystallinity. Further, at this time, the deterioration of the light emission characteristics due to the addition of nitrogen is suppressed by the n-type impurities. Furthermore, the effect of alleviating the lattice mismatch can be obtained by adding carbon. In this way, it becomes possible to obtain a good crystal having a predetermined band gap.

On the other hand, when the energy band gap of AlGaInAsNP exceeds 1.65 μm in terms of wavelength, InP is used as the substrate instead of GaAs, and InGaAs with an indium composition of 0.53 is epitaxially grown to achieve lattice matching. Excellent crystals can be obtained.

Therefore, in the present invention, the range between them, that is, 0.92 μm or more and 1.65 in terms of wavelength is used.
A particularly remarkable effect is obtained in the range of μm or less,
AlGa with good emission characteristics on GaAs substrate
An InAsNP epitaxial growth layer can be obtained.

From FIG. 2, the indium composition is 0.2
It can be seen that the change in the crystal quality is relatively small in the range from 1 to 0.35. Therefore, it can be said that the use of the composition within this range is particularly advantageous in that a semiconductor laser device having a large tolerance for the composition variation and the like can be obtained.

In other words, in the present invention, the light emitting layer E
The indium contained in (3) has a role of reducing the band gap of the light emitting layer E in a range in which the lattice mismatch with the GaAs substrate S is not fatal. Then, nitrogen is added in order to further reduce the band gap of the light emitting layer E and obtain a predetermined oscillation wavelength. However, when nitrogen is added, carbon is likely to be incorporated into the crystal, resulting in deterioration of light emission characteristics. Therefore, the influence of carbon is suppressed by adding an n-type impurity such as Si (silicon) at a concentration higher than that of carbon.

The bond energy between nitrogen and carbon contained in the light emitting layer E is extremely large as compared with the bond energy between carbon and a group V element other than nitrogen. Therefore, in a system containing nitrogen, carbon and nitrogen bond preferentially. When carbon and nitrogen are combined, carbon does not enter the group V element site as a substitutional impurity. In this case, carbon forms deep levels in the crystal. Therefore, in a system containing nitrogen,
Unlike other III-V group compound semiconductors, carbon has a stronger tendency to form deep levels. As a result, it was found that the emission characteristics deteriorate.

On the other hand, in the present invention, the semiconductor becomes n-type by adding the n-type impurity in the light emitting layer E at a concentration higher than that of carbon. Therefore, the deep level due to carbon comes to a position deeper than the Fermi level and is less likely to be activated, and the influence is reduced.

As the n-type impurities used in the present invention, the above-mentioned various types can be used, but among these, it is particularly preferable to use silicon (Si). Since these elements have a large binding energy with carbon, carbon can be deactivated with high efficiency by adding them at a concentration higher than that of carbon.

Further, silicon (Si) has a large binding energy with nitrogen (N), and is also efficiently bound with nitrogen. As a result, these dopants act as n-type dopants at the Group III element sites, while at the same time preventing the formation of deep carbon levels by preventing the bond between nitrogen and carbon.

Due to these effects, it is possible to suppress the generation of deep levels derived from carbon and form a high quality GaInAsNP light emitting layer, reduce the decrease in light emitting efficiency, have high light emitting efficiency, and output fluctuations with temperature changes. It is possible to provide a semiconductor laser device having a small size.

Here, Al _x Ga _1-x-y In _y
As _p N _p P _1-p-q (0 ≦ x, 1-x-y ≦ 1, 0
The light emitting layer made of <y, p, q ≦ 1) means Al _x Ga.
_{1-x -y In y As p} N p P 1-p-q (0 ≦ x ≦
1, 0 ≦ 1-x−y ≦ 1, 0 <y ≦ 1, 0 <p ≦ 1,0
<Not limited to the light emitting layer of q ≦ 1) a single layer, Al _x
Ga _1−x−y In _y As _p N _p P _1−p−q (0 ≦ x
≦ 1, 0 ≦ 1-x−y ≦ 1, 0 <y ≦ 1, 0 <p ≦ 1,
SCH (Single C) having a well layer of 0 <q ≦ 1)
onfined Heterostructure) structure and SQW (Single Qu
antum well) structure or MQW (Multiple-Quantum W)
well layer in the (ell) structure.

In the present invention, when sulfur (S) or selenium (Se) is used as the n-type impurity added to the light emitting layer E, nitrogen (N) or carbon (C) is obtained as much as silicon (Si). Although the effect of strong bonding cannot be obtained, since the atomic radius takes an intermediate value between arsenic (As) and nitrogen (N), it has an effect of reducing local strain inside the crystal. Therefore, good crystals can be obtained even with the same AlGaInAsNP.

On the other hand, for silicon (Si), Ga
Has the effect of reducing the average lattice constant because the atomic radius is smaller than that of GaA, even if the same AlGaInAsNP composition is used.
This has the effect of reducing the lattice strain with the s substrate. Tin (S
n), gallium (Ga) and indium (In)
Since it has an intermediate atomic radius, it has the effect of reducing local strain.

Since chlorine (Cl) is a so-called “double donor”, it suppresses activation of n-type carriers generated from a deep carbon level. Further, since it has an atomic radius intermediate between nitrogen (N) and arsenic (As), it has an effect of relaxing local strain in the crystal. Therefore, the same AlG
High quality crystals can be obtained with aInAsNP.

A second characteristic of the semiconductor laser device of the present invention is the semiconductor laser device having the above-mentioned first characteristic, in which the concentration of carbon (C) in the light emitting layer E is 2 × 10 5.
^It is over ¹⁸ cm ⁻³ .

According to the second feature of the present invention, by adding carbon (C) at a high concentration to the light emitting layer E, the lattice constant of the light emitting layer E can be reduced, and the lattice mismatch with the GaAs substrate S can be achieved. Can be relaxed. And in this case also, this carbon (C)
By simultaneously adding an n-type impurity having a concentration higher than the above, it is possible to suppress the formation of a deep level and prevent the deterioration of the light emission characteristics.

Al_xGa_1-xyIn_yAs_pN_pP
_1-p-q(0 ≦ x, 1−x−y ≦ 1, 0 <y, p, q
When determining the lattice constant of the light emitting layer E consisting of ≦ 1), X
The most accurate is the measurement by line diffraction. But this material
In the system, the line width of X-ray diffraction is usually less than 5 seconds.
No On the other hand, the concentration of carbon (C) is 2 × 10¹⁸cm
^-3In the above case, X-rays are compared to the case where carbon is not added.
Converted to a diffraction angle, the lattice constant of the light emitting layer E is about 4 seconds.
Get smaller. Therefore, the lattice constant is increased without increasing the strain amount.
By adding indium (In) as much as the reduction amount of
Wear. As a result, without increasing the concentration of nitrogen (N),
Long wavelength emission wavelength by reducing the band cap of the light emitting layer E
It can be lengthened.

FIG. 3 is a conceptual diagram for explaining the third feature of the present invention. That is, this figure is also a cross-sectional view in the direction parallel to the resonator of the semiconductor laser device.

The third feature of the present invention is on the GaAs substrate S.
A semiconductor laser device formed on a p-type clad layer
C contains Group II impurities, and the active layer A is at least
Al _xGa_1-xyIn_yAs_pN_pP
_1-p-q(0 ≦ x, 1−x−y ≦ 1, 0 <y, p, q
≦ 1) including the light emitting layer E and indium (I
n) Al with low composition_xGa_1-xyIn_yAs_pN_p
P_1-p-q(0 ≦ x, 1−x−y ≦ 1, 0 <y, p,
a light guide layer G consisting of q ≦ 1),
G exists on the p-type clad layer C side of the light emitting layer E, and
The guide layer G contains carbon (C) and a Si layer having a concentration higher than that of carbon.
Recon (Si) is added, and the light emitting layer E has a light guide.
Of lower concentration carbon (C) and higher concentration than carbon
It means that silicon (Si) is added.
It

According to the third feature of the present invention, first, the p-type cladding layer C contains a Group II impurity such as zinc (Zn). These Group II impurities act extremely effectively as p-type dopants in the AlGaInAsNP-based compound semiconductor used in the present invention.

However, there is a problem that group II impurities have a large diffusion coefficient in III-V group compound semiconductors. In particular, the concentration distribution near the tip of the diffusion region has a so-called "two-stage structure", and the diffusion front on the low concentration side has a large diffusion coefficient. Therefore, the group II impurities introduced into the clad layer C may diffuse into the active layer A and deteriorate the emission characteristics.

On the other hand, according to the third feature of the present invention, silicon (Si) and carbon (C) are added to the optical guide layer G on the p-type cladding layer C side. Carbon (C) is partially n-type and partially acts as p-type. But,
Since silicon (Si) is added at a higher concentration than carbon (C), the light guide layer G becomes n-type. If carbon (C) or silicon (Si) that generates n-type carriers is present in the optical guide layer G, the diffusion rate of a group II element such as zinc (Zn) diffused from the p-type clad layer C side. Significantly lower. Therefore, it is possible to suppress the diffusion of the p-type impurities and prevent the impurities from entering the active layer A.

Here, the optical guide layer G on the p-type clad C side
With regard to (2), it is desirable that the p-type is originally used, and it is desirable that the carrier concentration is low even when the n-type is used. On the other hand, in the present invention, carbon (C) is also added to prevent the invasion of the group II impurities, so that the n-type carrier is compared with the case where the invasion of the group II impurities is prevented only by silicon (Si). The amount can be reduced.

On the other hand, in order to increase the light emitting efficiency of the light emitting layer E, the concentration of carbon (C) that may form a non-light emitting center is set low in the light emitting layer E and is set in the light guide layer G.
The concentration of carbon (C) is increased to suppress the diffusion of the group II element. This prevents the emission efficiency of the light emitting layer E from being lowered due to the deep level of carbon (C), prevents the p-type impurities from entering the light emitting layer E, and allows the light guide layer G on the p-type clad side to have n. The carrier concentration of the mold can be lowered.

Furthermore, the light emitting layer E is made of silicon (Si).
When the concentration is higher than the silicon (Si) concentration of the light guide layer G, a barrier corresponding to the difference in Fermi level is formed for the n-type carriers overflowing from the light emitting layer E toward the p-side light guide layer C. Therefore, it is possible to suppress the problem that n-type carriers overflow into the optical guide layer G on the p-type clad C side. As a result, the luminous efficiency of the semiconductor laser device can be improved.

As described above, according to the third feature of the present invention, the light output of the laser can be improved and the fluctuation of the light output due to the change in the ambient operating temperature can be reduced.

[0050]

The embodiments of the present invention will be described in more detail below with reference to the examples.

(Embodiment 1) FIG. 4 is a schematic sectional view showing a semiconductor laser device according to a first embodiment of the present invention.
That is, this laser device has a structure in which semiconductor layers are stacked on the GaAs substrate 1. The materials and layer thicknesses of the layers are listed in order from the GaAs substrate 1 side as follows.

GaAs substrate 1 n-type AlGaAs cladding layer (1000 nm) 2 n-type GaAs spacer layer (25 nm) 3 n-side Ga _0.95 In _0.05 As _0.98 N _0.02
Optical guide layer (10 nm) 4 Ga _0.75 In _0.25 As _0.99 N _0.01 Quantum well layer (7 nm) 5 Ga _0.95 In _0.05 As _0.98 N _0.02 Barrier layer (10 nm ) 6 Ga _0.75 In _0.25 As _0.99 N _0.01 Quantum well layer (7 nm) 7 p-side Ga _0.95 In _0.05 As _0.98 N _0.02
Optical guide layer (10 nm) 8 p-type GaA layer (10 nm) 9 p-type AlGaAs oxide layer 10 p-type GaAs layer 11 p-type AlGaAs cladding layer 12 p-type GaAs heterobarrier reducing layer 13 p-type GaInAsN contact layer 14

That is, in this semiconductor laser,
The optical guide layers 4 to 8 act as active layers, and a multiple quantum well structure is formed with the quantum well layers 5 and 7 as light emitting layers. The current constriction for the active layer is caused by the p-type AlGaA.
s oxide layer 10.

In this embodiment, GaInA
For the sN quantum well layers 5 and 7, 5 × 1 of silicon (Si) is used.
0 ¹⁷ cm ⁻³ and carbon (C) are added at 5 × 10 ¹⁵ cm ⁻³ . Further, the p-side GaInAsN optical guide layer 8, a silicon (Si) of 1 × ¹⁰ 17 ^{cm -3,} carbon (C) were added 1 × ¹⁰ 16 ^{cm -3,} GaInAsN
The barrier layer 6 is made of silicon (Si) 3 × 10 ¹⁷ cm
^-3 , carbon (C) 1x10 ¹⁶ cm ^-3 , n-side GaI
The nAsN light guide layer 4 is made of silicon (Si) 5 × 1.
0 ¹⁷ cm ⁻³ and carbon (C) are added at 1 × 10 ¹⁶ cm ⁻³ .

Each of these three layers has a band gap of 0.98 μm in terms of wavelength. As described above, the active layer of the laser includes the GaInAsN quantum well layers 5 and 7, the p-side GaInAsN optical guide layer 8, and GaInA.
It is composed of the sN barrier layer 6 and the n-side GaInAsN light guide layer 4, and the active layer emits light having a wavelength of 1.3 μm as a whole.

The p-type GaAs layer 9 contains zinc (Z
n) is doped at 5 × 10 ¹⁷ cm ⁻³ . Also, A
The AlGaAs oxide layer 10 has an Al composition of 0.98, is doped with zinc (Zn) at 1 × 10 ¹⁸ cm ⁻³ , and has p
Type GaAs layer 11 has a zinc (Zn) concentration of 2 × 10 ¹⁸ c
m ⁻³ , the p-type AlGaAs cladding layer 12 has a zinc (Zn) concentration of 1 × 10 ¹⁸ cm ⁻³ , and the p-type GaAs heterobarrier reducing layer has a zinc (Zn) concentration of 5 × 10 ¹⁸ c.
The zinc (Zn) concentration of the m ⁻³ and p-type GaInAsN contact layer 14 is 7 × 10 ¹⁸ cm ⁻³ .

Here, in the GaInAsN quantum well layers 5 and 7, silicon (Si) is 5 × 10 ¹⁷ cm ⁻³ , carbon (C) is 5 × 10 ¹⁵ cm ⁻³ , and p-side GaInAsN is used.
The light guide layer 8 is made of silicon (Si) at 1 × 10 ¹⁷ c
m ⁻³ , carbon (C) 1 × 10 ¹⁶ cm ⁻³ , GaIn
3 × ¹⁰ silicon (Si) in AsN barrier layer 6 ^{1 7}
cm ⁻³ , carbon (C) 1 × 10 ¹⁶ cm ⁻³ , n side G
The aInAsN optical guide layer 4 is made of silicon (Si) 5 ×.
10 ¹⁷ cm ⁻³ , carbon (C) 1 × 10 ¹⁶ cm ⁻³
It is added, and in any case, the silicon (Si) concentration is higher than the carbon (C) concentration, so that it exhibits n-type conductivity.

Also, when carbon (C) forms a deep level, the Fermi level is near the impurity level of silicon (Si) and the concentration of silicon (Si) is high, so the carbon (C) is deep. The probability of transitions through levels is extremely low. Therefore, when the semiconductor laser device is laser-oscillated, the characteristic deterioration due to carbon (C) does not substantially appear.

Zinc (Zn) is formed in each layer on the p-type cladding side.
Is added, and the doping amount is set to the p-type GaAs layer 9
Is 5 × 10 ¹⁷ cm ⁻³ , the AlGaAs oxide layer 10 is 1 × 10 ¹⁸ cm ⁻³ , and the p-type GaAs layer 11 is 2 × 1.
It is 0 ¹⁸ cm ⁻³ , and the p-type AlGaAs cladding layer 12 has 1 × 10 ¹⁸ cm ⁻³ .

It is considered that the diffusion of zinc (Zn) is a two-step diffusion, the high concentration portion is a normal substitutional impurity diffusion, and the low concentration portion is a so-called "kick-off type" diffusion. In case of kick-off type diffusion, zinc (Zn)
The concentration is usually lower than about 5 × 10 ¹⁵ cm ⁻³ . Therefore, if the total value of the concentration of carbon (C) and the concentration of silicon (Si) in each layer forming the active layer is equal to or more than this value, diffusion of zinc (Zn) can be substantially prevented.

In fact, in this embodiment, GaInAs
For the N quantum well layers 5 and 7, 5 × 1 of silicon (Si) is used.
0 ¹⁷ cm ⁻³ , carbon (C) 5 × 10 ¹⁵ cm ⁻³ ,
Silicon (Si) is used for the p-side GaInAsN optical guide layer 8.
1 × 10 ¹⁷ cm ⁻³ , carbon (C) 1 × 10 ¹⁶ c
m ⁻³ , the GaInAsN barrier layer 6 is made of silicon (S
i) is 3 × 10 ¹⁷ cm ⁻³ and carbon (C) is 1 × 10
¹⁶ cm ⁻³ , n-side GaInAsN optical guide layer 4 was added from the p-type cladding layer side by adding silicon (Si) at 5 × 10 ¹⁷ cm ⁻³ and carbon (C) at 1 × 10 ¹⁶ cm ^−3. It was possible to prevent the diffusion of zinc (Zn).

The procedure for producing the semiconductor laser device of this embodiment will be described below.

First, n-type AlGa is formed on the GaAs substrate 1.
The As clad layer 2 is formed by MOCVD (Metal-Organic Chemic
al Vapor Deposition) at 670 ° C., the growth temperature is lowered to 620 ° C. to grow the n-type GaAs spacer layer 3, and the growth temperature is further lowered to 520 ° C. to grow the n-side Ga _0.95 In _{0. 05} As _0.98 N
_{0.0 2} Light guide layer 4, Ga _0.75 In _0.25 As
_0.99 N _0.01 quantum well layer 5, Ga _0.95 In
_0.05 As _0.98 N _0.02 barrier layer 6, Ga
_{0.7 5} In _0.25 As _0.99 N _0.01 quantum well layer 7, p-side Ga _0.95 In _{0 . 05} As _0.98 N
_{The 0.02} optical guide layer 8 and the p-type GaAs layer 9 were sequentially stacked.

Thereafter, the growth temperature is raised to 640 ° C. and p
-Type AlGaAs layer 17, p-type GaAs layer 11, p-type Al
The GaAs clad layer 12 was formed. Then, the growth temperature was lowered again to 520 ° C. to form the p-type GaAs heterobarrier reducing layer 13 and the p-type GaInAsN contact layer 14.

Here, the growth temperature is raised to increase the crystallinity, and the temperature is lowered to prevent the phase separation of GaInAsN. Regarding the p-type GaAs heterobarrier reducing layer 13 and the p-type GaInAsN contact layer 14, it is possible to increase the zinc (Zn) addition efficiency by lowering the growth temperature and prevent the diffusion of zinc (Zn) into the active layer. it can.

Materials for MOCVD include TMG (trimethyl gallium), TMAl (trimethyl aluminum), TMI (trimethyl indium), and SiH4.
(Silane), AsH3 (arsine), and DMHy (dimethylhydrazine) were used.

As the group III organic metal, ethyl type, chloride type and the like may be used. Dimethylhydrazine may be used as a raw material of nitrogen (N), ammonia,
Hydrazine or monomethylhydrazine may be used. Raw materials for carbon (C) include TMG, TMAl and DM
Hy or the like may be used, or CBr4 (carbon tetrabromide) may be used. When sulfur (S) or selenium (Se) is used, these hydrides may be used as a raw material, or an organometallic raw material may be used.

After the crystal growth is completed, a mesa structure is formed, and the p-type AlGaAs layer is oxidized by the oxidation process leaving the unoxidized conductive region 17, thereby forming the p-type Al.
A GaAs oxide layer 10 was formed.

After the p-type AlGaAs oxide layer 10 is formed, the passivation film 15 is formed, and the polyimide filling 1
6 was done. After that, an electrode metal was vapor-deposited and then cleaved to prepare a laser, and evaluation was performed.

The semiconductor laser of this example has a wavelength of 1.3 μm, a threshold current value of 3 mA, and an efficiency of 0.35 W at room temperature with the coating of (wavelength / 2) on the end face of the resonator.
/ A was obtained. Moreover, it was found that the maximum oscillation temperature exceeded 150 ° C. and the temperature characteristics were good.

On the other hand, in the comparative example in which carbon (C) and silicon (Si) were not added to the active layer, the optical output of the laser sharply decreased with the ambient temperature,
The maximum oscillation temperature dropped below 80 ° C. It is considered that this is because zinc (Zn) diffused from each p-type layer in the active layer.

(Second Embodiment) Next, a second embodiment of the present invention will be described. In this embodiment, a semiconductor laser device having the same laminated structure as that of the first embodiment described above is formed. However, the concentration of silicon (Si) in the GaInAsN quantum well layer 5 and the GaInAsN quantum well layer 7 was set to 2 × 10 ²⁰ cm ^−3, and the concentration of carbon (C) was set to 1.5 × 10 ¹⁹ cm ⁻³ .

With this structure, silicon (Si) and carbon (C)
When Ga is not added, the composition of GaInAsN is Ga
_{When 0.67} In _0.33 As _0.995 N _0.005 is set, oscillation occurs at 1.3 μm. At this time, the lattice mismatch is 2.
3%.

On the other hand, when silicon (Si) and carbon (C) are added, the lattice mismatch of the crystal having this composition becomes 2.1%. When the lattice mismatch is 2.3%, the critical film thickness (upper limit film thickness where misfit defects do not occur) is about 8 nm. Since the double quantum well structure is used in this embodiment, the increase in energy due to the quantum well is about 180.
It becomes meV.

On the other hand, when the lattice mismatch is 2.1%, the critical film thickness is about 10 nm. The increase in energy due to the quantum well at this time is about 120 meV. Therefore, in order to select the same oscillation wavelength, indium (In) can be reduced by an amount corresponding to this energy, and the lattice mismatch becomes 0.2%. Since the critical thickness is increased due to the reduction of lattice mismatch, the width of the quantum well can be increased. Therefore, the transition wavelength becomes longer, and the indium (In) composition can be further reduced.

Due to such a synergistic effect, the final composition
Is Ga_0.72In_0.28As _0.995N
_0.005The lattice irregularity is 1.9% and the critical film thickness is
It becomes 13 nm.

FIG. 5 is a graph showing the relationship between the lattice mismatch (mismatch) of the light emitting layer and the critical film thickness in this embodiment.

Thus, the critical film thickness can be increased by adding silicon (Si) and carbon (C). As a result, the active layer volume of the laser is 5
Since it can be increased by 0% or more, the light output can be increased. In practice, addition of impurities can suppress the growth effect of crystal defects such as dislocations. Therefore, even if the critical film thickness is the same, the spread of crystal defects is small, and a semiconductor laser device with high luminous efficiency and high reliability can be realized. .

The embodiments of the present invention have been described above with reference to specific examples. However, the present invention is not limited to these specific examples.

For example, the present invention is not limited to the edge-emitting semiconductor laser device, but is also a surface-emitting semiconductor laser device, or an HBT (Hetero-Bipolar Tra) using strained GaInAsN for the light emitting diode, the base layer and the collector layer.
HEMT (High-Electron Mobility Transistor) using strained GaInAsN for the channel layer,
A photovoltage converter using strained GaInAsN for the absorption layer,
The same effects can be obtained by applying the same to a photocurrent converter or the like.

In addition, the present invention can be variously modified and implemented without departing from the spirit of the invention, and these examples are also included in the scope of the present invention.

[0082]

As described above, according to the present invention,
In the wavelength range of 1.2 to 1.6 μm, which is suitable for long-wavelength optical communication, the influence of deep level based on carbon (C) is suppressed, and the lattice distortion is small despite the same GaInAsN composition, and p It is possible to realize a semiconductor laser device in which fluctuations in optical output are small with respect to a rise in temperature at which p-type impurities do not easily diffuse from the mold cladding layer to the active layer, which is a great industrial advantage.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing a main part of a semiconductor laser of the present invention.

FIG. 2 is a graph showing the relationship between the indium concentration of a GaInAsN crystal epitaxially grown on a GaAs substrate and the half width of the X-ray diffraction peak.

FIG. 3 is a conceptual diagram for explaining a third feature of the present invention.

FIG. 4 is a schematic sectional view showing a semiconductor laser device according to a first embodiment of the present invention.

FIG. 5 is a graph showing the relationship between the lattice mismatch (mismatch) of the light emitting layer and the critical film thickness in the second embodiment of the present invention.

[Explanation of symbols]

1 GaAs substrate 2 n-type AlGaAs cladding layer (1000 nm) 3 n-type GaAs spacer layer (25 nm) 4 n-side Ga _0.95 In _0.05 As _0.98 N
_0.02 Optical guide layer (10 nm) 5 Ga _0.75 In _0.25 As _0.99 N _0.01
Quantum well layer (7 nm) 6 Ga _0.95 In _0.05 As _0.98 N _0.02
Barrier layer (10 nm) 7 Ga _0.75 In _0.25 As _0.99 N _0.01
Quantum well layer (7 nm) 8 p-side Ga _0.95 In _0.05 As _0.98 N
_0.02 optical guide layer (10 nm) 9 p-type GaA layer (10 nm) 10 p-type AlGaAs oxide layer 11 p-type GaAs layer 12 p-type AlGaAs cladding layer 13 p-type GaAs heterobarrier reduction layer 14 p-type GaInAsN contact layer 15 passivation film 16 Polyimide 17 Unoxidized conductive region A Active layer C Cladding layer E Light emitting layer G Light guide layer L Laser light S Substrate

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Rei Hashimoto             1st Komukai Toshiba-cho, Sachi-ku, Kawasaki-shi, Kanagawa             Inside the Toshiba Research and Development Center F term (reference) 5F073 AA13 AA45 AA74 AA83 CB16                       CB18 CB19 DA05 DA35 EA15                       EA29

Claims (6)

[Claims] 1. A GaAs substrate, which is provided on the GaAs substrate and has a wavelength of 0.
Al having an energy band gap of 92 μm or more and 1.65 μm or less and having a larger lattice constant than GaAs.
_{x1 Ga 1-x1-y1 In} y1 As p1 N p1 P
_1-p1-q1 (0 ≦ x1 ≦ 1, 0 ≦ 1-x1-y1 ≦
1, 0 <y1 ≦ 1, 0 <p1 ≦ 1, 0 <q1 ≦ 1), the light emitting layer containing carbon (C) and an n-type impurity, and the n-type A semiconductor laser device, wherein the content of impurities is larger than the content of carbon (C). 2. The content of the carbon (C) is 2 × 10.
^18. The semiconductor laser device according to claim 1, wherein the semiconductor laser device has a size of ¹⁸ cm ⁻³ or more. 3. A GaAs substrate, It is provided on the GaAs substrate and is doped with a Group II element.
A p-type semiconductor layer, It is provided on the GaAs substrate and has a wavelength of 0.
Energy band gap of 92 μm or more and 1.65 μm or less
With Alps_x2Ga_1-x2-y2In _y2As
_p2N_p2P_1-p2-q2(0≤x2≤1, 0≤1-
x2-y2 ≦ 1, 0 <y2 ≦ 1, 0 <p2 ≦ 1, 0 <q
2 ≦ 1) a light emitting layer, A provided between the p-type semiconductor layer and the light emitting layer
l_x3Ga_{1-x3- y3}In_y3As_p3N_p3P
_1-p3-q3(0 ≦ x3 ≦ 1, 0 ≦ 1-x3-y3 ≦
From 1, 0 <y3 ≦ 1, 0 <p3 ≦ 1, 0 <q3 ≦ 1)
Light guide layer, Equipped with The light emitting layer may include carbon (C) and higher than carbon (C).
Containing a concentration of n-type impurities, The light guide layer is made of carbon (C) and carbon (C).
Also contains a high concentration of n-type impurities, The content of the carbon (C) contained in the light emitting layer is
Less than the content of carbon (C) contained in the light guide layer
A semiconductor laser device characterized by the following. 4. The total value of the concentration of the carbon (C) and the concentration of the n-type impurity contained in the light emitting layer is 5 × 10 ^15.
The semiconductor laser device according to claim 3, wherein the semiconductor laser device has a cm ^-3 or more. 5. The n-type impurity is at least one selected from the group consisting of silicon (Si), sulfur (S) and selenium (Se).
4. The semiconductor laser device according to any one of 4 above. 6. A laser beam having a wavelength of 1.2 μm or more and 1.6 μm or less is emitted.
The semiconductor laser device according to any one of 1.