JP2002305357A - Semiconductor laser device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor laser device which has high output and realizes high speed writing. SOLUTION: The semiconductor laser device is provided with a substrate, first conductive clad layer formed on the substrate, the active layer of single quantum well structure or multiplex quantum well structure which is formed on the first conductive clad layer and whose well layer is set to be Alb Ga1-b As (0<=b<=0.15) and a second conductive clad layer which is formed on the active layer and is constituted of In0.5 (Ga1-c Alc )0.5 P (0<=c<=0.2).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a semiconductor laser device.

[0002]

2. Description of the Related Art In recent years, a semiconductor laser device having a wavelength of 780 nm has been put to practical use for writing a CD (Compact Disk). In this writing laser device, the speed has been increased. For example, a CD-R having a 12 × or 16 × speed has been put to practical use. This wavelength 78
The 0 nm semiconductor laser device is a GaAs laser device using AlGaAs for the active layer. The structure is such that an n-type cladding layer made of n-type AlGaAs and a multiple quantum well (MQW; Multip
le Quantum Well) structure AlGaAs
/ AlGaAs active layer and a p-type cladding layer made of p-type AlGaAs are sequentially used to form a double hetero structure.

[0003]

If there is an ultra-high-speed writing laser device capable of writing at a higher speed than a conventional high-speed writing laser device, the above-mentioned CD-R, etc.
It is thought that it can be used effectively for various uses. In order to realize such an ultra-high-speed writing laser device, it is necessary to further increase the output than a conventional high-speed writing laser device. However, it has been considered that it is extremely difficult to increase the output of a conventional high-speed writing laser device any further. For example, it has been considered that it is difficult to obtain an ultra-high-speed writing laser device exceeding 20 times speed with a CD-R.

That is, in the conventional high-speed writing laser device, the Al composition of the cladding layer is controlled and the cladding layer is made of Al _0.5 Ga in order to confine the laser beam in the active layer.
_A refractive index difference was provided between the active layer and the cladding layer at _0.5 As or the like. However, in AlGaAs, the mobility decreases when the Al composition ratio becomes 0.45 or more. For this reason, in the conventional laser device for high-speed writing, it is inevitable that the mobility of the cladding layer becomes small. But,
When the mobility of the cladding layer is reduced, high output cannot be obtained. If high output cannot be obtained, high-speed writing cannot be performed. For this reason, it has been considered that the conventional high-speed writing laser device has a limit in increasing the output. For example, in a laser device used for a CD-R, writing at about 20 times speed was considered to be the limit.

However, the present inventor has conducted various experiments in order to obtain an ultra-high-speed writing laser device capable of writing at high speed with high output. As a result, the material of the cladding layer was changed to AlGaAs and In _0.5 (Ga _1-y A
l _y ) _0.5 P (0 ≦ y ≦ 0.2)
It has been found that the mobility of the cladding layer can be increased. As a result, the output of the laser device can be increased, and the present inventors have come to know independently that an ultra-high-speed writing laser device can be obtained.

However, in a GaAs laser device,
As described above, instead of the AlGaAs cladding layer, InGa
The use of an AlP cladding layer is unexpected for a technician. Because InGaAlP is Al
This is because the thermal resistance is higher than that of GaAs. That is, generally, when a semiconductor material having a high thermal resistance is used for a semiconductor device,
The temperature of the semiconductor device tends to increase. When the temperature of the semiconductor device rises, the reliability of the device greatly decreases.

However, according to the experiment of the present inventor, GaAs
In the case of a system-based semiconductor laser device, it has been found that even when InGaAlP is used, the temperature of the device hardly increases.
The inventor has further repeated simulations and experiments. As a result, InGaAlP has the disadvantage of high thermal resistance and the advantage of high mobility.
It has been found that if the composition of 1P is set to an appropriate value, the merit of high mobility becomes greater. As a result, a laser device with a high output can be used without lowering its reliability.
It turned out to be obtained. In this manner, the present inventor contradicts the conventional technical common sense and adds the I.S.A.
By using the nGaAlP cladding layer, they came to know uniquely that an ultrahigh-speed writing laser device can be obtained.

The present invention has been made in view of this. In other words, this method is obtained based on the results of unique simulations and experiments of the inventor, which is different from the conventional common sense of the art, and is based on the unique knowledge of the inventor.

SUMMARY OF THE INVENTION An object of the present invention is to provide a laser device capable of writing at high speed with high output.

[0010]

The laser device according to the present invention comprises:
Substrate and a first conductivity type cladding layer formed on said substrate, formed in said first conductivity type cladding layer, the well layer _{Al b Ga 1-b As (} 0 ≦ b ≦ 0.15) An active layer having a single quantum well structure or a multiple quantum well structure, and _In0.5 (Ga1 _- cA) formed on the active layer.
l _c) characterized by comprising a _{0.5 P (0 ≦ c ≦ 0.2} ) second conductivity type cladding layer made of, a.

Further, the laser device according to the present invention comprises an n-type GaAs
s, an n-type cladding layer formed on the substrate, the active layer formed on the n-type cladding layer, and an impurity concentration formed on the active layer having an impurity concentration of 1.0 ×
10 ¹⁸ [/ cm ³ ] or less p-type In _0.5 (Ga
_1-c Al _c ) _0.5 P (0 ≦ c ≦ 0.2), a first p-type clad layer, and a p-type In layer formed on the first p-type clad layer in a ridge shape. _0.5 (Ga _1-d A
l _d ) _0.5 p (0 ≦ d ≦ 0.2) second p-type cladding layer, and n-type Al _h Ga _1-h formed on both sides of the second p-type cladding layer As (0.5 ≦ h ≦ 1)
And a current blocking layer comprising:

Further, the laser device according to the present invention has an n-type GaAs
and a n-type InG formed on the substrate.
an n-type cladding layer made of aP, and on the n-type cladding layer
Formed on the active layer, and formed on the active layer
The impurity concentration is 1.0 × 10 ¹⁸[/ Cm³]below
p-type In_0.5(Ga_1-cAl_c)_0.5P (0 ≦ c
≦ 0.2), the first p-type cladding layer
Formed on the p-type cladding layer of
N-type Al with grooves formed_hGa_1-hAs (0.5 ≦
h ≦ 1), and a current blocking layer formed in the groove.
In_0.5(Ga _1-eAl_e)_0.5P (0 ≦ e ≦
0.2), the second p-type cladding layer comprising:
A second conductive type clad layer and a current blocking layer formed on the current blocking layer;
In_{0 . 5}(Ga_1-fAl_f)_0.5P (0 ≦
f ≦ 0.2).
It is characterized by that.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A semiconductor laser device according to the present embodiment comprises an n-type GaAs substrate, an n-type cladding layer,
An active layer of As / AlGaAs, a p-type cladding layer,
, A laser device for a CD having a wavelength of about 780 nm sequentially provided with In _0.5 Ga _{0 .} One of the features is that the resistance of the cladding layer is reduced by using ₅ P. The laser device of the present embodiment can be used for ultra-high speed writing in a CD-R or the like. Hereinafter, a laser device having a ridge conduction path structure according to the first embodiment and a laser device having an internal stripe structure according to the second embodiment will be described with reference to the drawings.

(First Embodiment) FIG. 1 is a view showing the structure of a semiconductor laser device according to a first embodiment of the present invention. On the n-type GaAs substrate 101, an n-type In _0.5 G
a _0.5 P n-type cladding layer 102, Al _0.3
First guide layer 103 made of Ga _0.7 As, AlG
a multiple quantum well structure composed of aAs / AlGaAs (MQ
W structure), a second guide layer 105 made of Al _0.3 Ga _0.7 As, a p-type In _{0. 5} Ga
_0.5 P first p-type cladding layer 106, ridge-shaped p-type In _{0. A} second p-type cladding layer (ridge portion) 107 made of ₅ Ga _0.5 P is formed. The impurity concentration of the p-type cladding layers 106 and 107 is 8.0 × 10
¹⁷ [/ cm ³ ]. Further, the above-mentioned ridge portion 10
7 has a bottom width of 3.0 μm. This ridge portion 107
Are buried with a current blocking layer 108 made of n-type Al _0.3 Ga _0.7 As. These ridges 1
07, a p-type GaAs contact layer 109 is formed on the current blocking layer 108. The laser device, the well layer of the active layer 104 is _{Al b Ga 1-b As (} 0 ≦ b ≦
0.15), and the wavelength of the laser beam becomes about 780 nm.

One of the features of the laser device shown in FIG. 1 is that the n-type cladding layer 102 and the p-type
7 is made of In _0.5 Ga _0.5 P.
By doing so, the cladding layers 102, 106, 1
07 has a higher mobility. Then, the p-type cladding layer 10
Since the mobility of 6, 107 is high, the threshold voltage does not increase even if the bottom width of the ridge portion is reduced to 3.0 μm.

In the semiconductor laser device shown in FIG.
An active layer 104 includes an n-side electrode (not shown) formed on the lower side of the s substrate 101 in the figure and a p-side electrode (not shown) formed on the upper side of the p-type GaAs contact layer 109 in the figure.
Current is injected into the Here, since the current blocking layer 108 is an n-type semiconductor, a current from the p-side electrode is applied to the current blocking layer 1.
08, the second p-type cladding layer (ridge portion)
The active layer 104 is injected from the first p-type cladding layer 106 into the active layer 104. That is, the current blocking layer 108
It functions to constrict the current just below the ridge portion 107. In the device shown in FIG. 1, the forbidden band width of the current blocking layer 108 is made larger than the forbidden band width of the ridge portion 107 to enhance the current blocking effect. The current blocking layer 108
Has a function of forming a difference in the refractive index between the lower portion of the ridge portion 107 and both sides thereof, and confining the laser beam to the lower portion of the ridge portion 107. As described above, the ridge portion 1
Current is injected immediately below the active layer 107, and a laser beam having a wavelength of about 780 nm is emitted from the vicinity of the active layer 104 immediately below the ridge portion 107.

The semiconductor laser device shown in FIG.
In the cladding layers 102, 106, 107_0.5Ga
_0.5Ultra-high speed write operation is possible because of using P
You. This is In_0.5Ga_0.5Because the mobility of P is high
Is analyzed as That is, In _0.5Ga_0.5P
When used for the cladding layer, the mobility of the cladding layer can be increased.
You. And by increasing the mobility of the cladding layer,
Output can be made possible. This enables high output
To enable writing at ultra-high speeds.
it can. For example, the laser device shown in FIG.
If it is used as a user device, writing over 20 times speed
Can be made possible.

In the laser device of FIG. 1, a ridge conduction path type laser device having a current blocking layer 108 is provided.
The threshold voltage can be reduced.

In the laser device of FIG. 1, since the mobility of the p-type cladding layers 106 and 107 is large, the width of the ridge portion 107 can be reduced to 4 μm or less. FIG.
This device is an example in which the width of the ridge portion 107 is 3 μm. By thus narrowing the ridge portion, kink can be prevented, and light emission becomes stable even at high output. In most cases, a laser device is used by focusing a laser beam on a minute spot by an optical system, and therefore, the stability of light emission is important.

In the laser device shown in FIG. 1, since the mobility of the cladding layer is high, the impurity concentration can be reduced. With such a low impurity concentration,
Impurity diffusion into the active layer can be suppressed. Then, by suppressing impurity diffusion, deterioration of the active layer can be suppressed, and the life of the laser device can be prolonged. In particular, when the laser device of FIG. 1 is used as an ultra-high-speed writing laser device, it is liable to deteriorate, so that it is important that the lifetime is long. Here, according to experiments performed by the inventor, when the impurity concentration was set to 1.0 × 10 ¹⁸ [/ cm ³ ] or less, the life of the laser device was particularly prolonged. FIG.
The apparatus described above has an impurity concentration of 8.0 × 10
^This is an example of ¹⁷ [/ cm ³ ].

The laser device shown in FIG. 1 can also be used as a high-speed writing laser device. For example, FIG.
Can be used as a laser device for CD-Rs of about 16 times speed. In this case, the laser device of FIG. 1 has an impurity concentration of 1.0 × 10 ¹⁸ [/
cm ³ ] or less, so that the life of the laser device can be extended. In contrast, Al _0.5 G
In the conventional high-speed writing laser device using the a _0.5 As cladding layer, the impurity concentration of the cladding layer is set to 1.0 × 10 ¹⁸ [/ cm ³ ] in order to reduce the resistance of the cladding layer.
Had to be larger. For this reason, in the conventional high-speed writing laser device, the active layer is easily deteriorated due to impurity diffusion into the active layer, and the life of the device is short.

Next, the cladding layers 102, 106, 107
Consider the material and composition of That is, the laser device of FIG.
In this case, the cladding layers 102, 106, 107_0.5
Ga _0.5P, but this was changed to InGaAlP or AlG
Since a laser device can be formed even with aAs,
Argue.

According to the simulations and experiments of the inventor, the n-type cladding layer 102 and the p-type cladding layer 10
The _{6,107, In 0.5 (Ga 1-} y Al y) 0.5
P, and when this Al composition y is 0.2 or less,
It has been found that the laser device can be used for ultra-high speed writing. This is because the cladding layers 102, 106, and 107 are made of In _0.5 (Ga _1-y Al
_y ) By setting to _0.5 P, the temperature rise of the laser device is suppressed, and the cladding layers 102, 10
By setting the Al composition y of each of the layers 6 and 107 to 0.2 or less, the refractive index difference between the cladding layers 102, 106, and 107 and the active layer 104 increases, and the light confinement coefficient of the active layer 104 increases to increase the output. Will be analyzed, according to. Further, the p-type cladding layers 106 and 107 are
_{0.5 (Ga 1-y Al y} ) 0. ₅ P (0 ≦ y ≦ 0.
In the case of 2), the ridge width of the first p-type cladding layer 106, the first p-type cladding layer 106 and the second p-type
It has been found that the impurity concentration of the mold cladding layer 107 may be about the same as that of the apparatus shown in FIG.

Further, according to the inventor of simulations and experiments, the p-type cladding layer 106, 107 as described above _{In 0.5 (Ga 1-y Al} y) 0.5 P (0 ≦
y ≦ 0.2) and the n-type cladding layer 102 is made of AlGaAs
Even at s, it was found that the laser device could be used for ultra-high speed writing. It is analyzed that this is because there is no current blocking layer 108 on the n-type cladding layer 102 side.

As described above, in the laser device of FIG.
Mold cladding layers 106 and 107 _0.5(Ga_1-y
Al_y)_0.5P (0 ≦ y ≦ 0.2) and n-type crack
Layer 102_0.5(Ga_1-yAl_y)_0.5P
(0 ≦ y ≦ 0.2) or AlGaAs,
The device can be used for ultra-high speed writing.

(Second Embodiment) The difference between the semiconductor laser device of the second embodiment and the first embodiment is that the p-type cladding layers 206 and 207, as shown in FIG.
207a is different. This device uses p
A first current blocking layer 208a on the mold cladding layer 206;
After growing the second current blocking layer 208b, the current blocking layer 208
a, 208b are formed in a part of the groove by etching, and then the second p-type cladding layer 207 and the third groove are formed.
Is a semiconductor laser device called an internal stripe structure.

FIG. 2 shows a semiconductor device according to a second embodiment of the present invention.
It is a figure showing the structure of a body laser device. n-type GaAs substrate
On n-type In 201_0.5Ga_0.5N consisting of P
Mold cladding layer 202, Al_0.3Ga_0.7From As
First guide layer 203, AlGaAs / AlGaAs
Active layer 204 of MQW structure made of_0.3Ga
_0.7As guide layer 205 made of As, p-type In
_0.5Ga_0.5P-type first p-type cladding layer 20
6, n-type Al_0.7Ga_0.3Current blocking layer made of As
208a, a current blocking layer 208b made of n-type AlAs,
Are sequentially formed. Then, the current blocking layer 208a,
At the center of 208b, striped by etching
Grooves are formed. In this striped groove, p
Type In_0.5Ga_0.5Second p-type cladding made of P
A layer (stripe portion) 207 is formed. p-type
The impurity concentration of the lad layers 206 and 207 is 8.0 × 10
¹⁷[/ Cm³]. Also, a second p-type cladding layer
The width of the bottom side of the lower side of FIG. 207 is 3.0 μm. This second
2 p-type cladding layer 207 and current blocking layer 208
b, p-type In_0.5Ga_0.5The third of P
A p-type cladding layer 207a is formed. And this
Is formed on the third p-type cladding layer 207a.
A contact layer 209 is formed. This laser device
Means that the well layer of the active layer 104 is Al_bGa_1-bAs (0
≦ b ≦ 0.15) and the wavelength of the laser beam is about 780 n
m.

First, the first p-type cladding layer 206 and the first p-type cladding layer 206 around the stripe portion 207 of the semiconductor laser device of FIG.
The current blocking layer 208a and the second current blocking layer 208b are sequentially formed, and then the first current blocking layer 208a and the second current blocking layer 208b are formed.
The central portion of the current block layer 208b is etched in a stripe shape to form a groove, and then the second p-type cladding layer (stripe portion) 207 and the third p-type cladding layer 20 are formed.
7a and the p-type contact layer 209 can be sequentially formed and obtained.

In the semiconductor laser device of FIG. 2, similarly to the first embodiment (FIG. 1), the n-type cladding layer 202 and the p-type cladding layers 206 and 207 are formed of In _0.5 Ga.
_0.5 P. This increases the mobility of the cladding layers 202, 206, and 207. Since the mobility of the p-type cladding layers 206 and 207 is high, the threshold voltage does not increase even if the bottom width of the stripe portion 207 is reduced to 3.0 μm.

The laser device shown in FIG. 2 can also be used as an ultra-high-speed writing laser device, as in the first embodiment (FIG. 1). Further, similarly to the first embodiment, it can be used as a long-life laser device for high-speed writing.

[0031]

According to the present invention, on a substrate, the first conductivity type cladding layer, the well layer _{Al b Ga 1- b As (0} ≦ b ≦
0.15). In a semiconductor laser device in which an active layer having a single quantum well structure or a multiple quantum well structure and a second conductivity type cladding layer are sequentially formed, the second conductivity type cladding layer is formed of In _0.5 (Ga _1-c Al _c ) _0.5 P (0 ≦ c ≦
0.2), it is possible to provide a laser device which has a high output, a long life, and can be written at a high speed.

[Brief description of the drawings]

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

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

[Explanation of symbols]

101, 201 n-type GaAs substrate 102, 202 n-type cladding layer 104 made of n-type In _0.5 Ga _0.5 P, MQW active layer 106, 206 made of AlGaAs / AlGaAs p-type In _0.5 Ga _0. First p-type cladding layer made of ₅ P 107 Second p-type made of p-type In _0.5 Ga _0.5 P
Type cladding layer (ridge portion) 207 p-type In _0.5 Ga _0.5 P second p
Type clad layer (stripe portion) 207a Third p-type clad layer made of p-type In _0.5 Ga _0.5 P 108 Current blocking layer 208 made of n-type Al _0.7 Ga _0.3 As 208a n-type Al _{0 0.7} Ga _0.3 As
Current blocking layer 208b of n-type AlAs

Claims (9)

[Claims] 1. A substrate, a first conductivity type clad layer formed on the substrate, and a well layer formed on the first conductivity type clad layer,
_{l b Ga 1-b As (} 0 ≦ b ≦ 0.15) and the active layer of single quantum well structure or a multiple quantum well structure and, _{an In} 0.5 formed on the active layer _{(Ga 1-c} Al
_c ) a second conductivity type cladding layer made of _0.5 P (0 ≦ c ≦ 0.2). 2. The p-type cladding layer according to claim 1, wherein the first conductivity type cladding layer is an n-type cladding layer, and the second conductivity type cladding layer is a p-type cladding layer having an impurity concentration of 1.0 × 10 ¹⁸ [/ cm ³ ] or less. The semiconductor laser device according to claim 1, wherein 3. An In _0.5 (Ga _{1- d} Al _d ) _0.5 P formed in a ridge shape on the second conductivity type cladding layer.
A second second-conductivity-type clad layer made of (0 ≦ d ≦ 0.2), and formed on both sides of the second second-conductivity-type clad layer;
3. The semiconductor laser device according to claim 1, further comprising: a current blocking layer made of a first conductivity type semiconductor. 4. 4. A method according to claim 1, wherein said second conductive type clad layer is formed on said second conductive type clad layer.
First conductivity type semiconductor with a stripe-shaped groove formed in part
A current blocking layer made of a body, and In formed in the groove._0.5(Ga_1-eAl_e)
_0.5P (0 ≦ e ≦ 0.2) second second conductivity type
A cladding layer, the second second conductivity type cladding layer, and the current blocking layer
In formed on _0.5(Ga_1-fAl_f)
_0.5Third second conductivity type made of P (0 ≦ f ≦ 0.2)
And a cladding layer.
The semiconductor laser device according to claim 2. 5. The semiconductor laser device according to claim 3, wherein a width of a bottom side of said second second conductivity type cladding layer is 4.0 [μm] or less. Wherein said current blocking _layer, Al _{h Ga 1-h} As
5. The semiconductor laser device according to claim 3, wherein the current blocking layer comprises (0.5 ≦ h ≦ 1). 7. The semiconductor laser device according to claim 6, wherein a forbidden band width of all or a part of said current blocking layer is larger than a forbidden band width of said second second conductivity type cladding layer. . 8. A substrate made of n-type GaAs, an n-type clad layer formed on the substrate, the active layer formed on the n-type clad layer, and formed on the active layer. The impurity concentration is 1.0 × 10
¹⁸[/ Cm³] The following p-type In_0.5(Ga_1-cA
l_c)_0.5First p-type consisting of P (0 ≦ c ≦ 0.2)
A cladding layer, formed in a ridge shape on the first p-type cladding layer,
p-type In_0.5(Ga _1-dAl_d)_0.5P (0 ≦ d
≦ 0.2), and an n-type A layer formed on both sides of the second p-type cladding layer.
l_hGa_1-hCurrent blocking consisting of As (0.5 ≦ h ≦ 1)
A semiconductor laser device comprising: a stop layer. 9. A substrate made of n-type GaAs, and an n-type semiconductor formed of n-type InGaP formed on the substrate.
A lad layer; the active layer formed on the n-type clad layer; and an impurity concentration formed on the active layer, the impurity concentration being 1.0 × 10
¹⁸[/ Cm³] The following p-type In_0.5(Ga_1-cA
l_c)_0.5First p-type consisting of P (0 ≦ c ≦ 0.2)
A cladding layer, formed on the first p-type cladding layer,
N-type Al with an i-shaped groove formed_hGa_1-hAs
A current blocking layer made of (0.5 ≦ h ≦ 1);_0.5(Ga_1-eAl_e)
_0.5A second p-type crack consisting of P (0 ≦ e ≦ 0.2)
Layer, the second second conductivity type cladding layer and the current blocking layer
In formed on _0.5(Ga_1-fAl_f)
_0.5A third p-type crack composed of P (0 ≦ f ≦ 0.2)
And a semiconductor layer.