JP2537295B2 - Semiconductor laser device and manufacturing method thereof - Google Patents

Description

TECHNICAL FIELD The present invention relates to a semiconductor laser device and a method for manufacturing the same,
In particular, the present invention relates to a semiconductor laser device that exhibits excellent temperature characteristics and can continuously oscillate visible light even at room temperature, and a method for manufacturing the same.

(Prior Art) In recent years, there has been a demand for the realization of a semiconductor laser device that oscillates in a short wavelength region for the purpose of enhancing the functions of an optical information processing system.

An AlGaInP crystal lattice-matched to a GaAs substrate has attracted attention as a material for a visible light semiconductor laser that emits light having a wavelength of 600 nm band.

As a method for growing AlGaInP crystal on a GaAs substrate, a molecular beam epitaxy method (MBE method) is expected in addition to the metal organic chemical vapor deposition method (MOCD method).

It has been reported that an AlGaInP-based visible light semiconductor laser device fabricated by using the MBE method continuously oscillated visible light at room temperature (Hayakawa, et.al. Journal of Crystal Growt
h 95 (1989) pp.949).

FIG. 3 shows a cross-sectional view of a conventional AlGaInP-based visible light semiconductor laser device manufactured by the MBE method.

On a first conductivity type GaAs substrate 1, a first conductivity type GaAs buffer layer 2, a first conductivity type GaInP buffer layer 3, a first conductivity type AlGaI
nP first clad layer 4, GaInP active layer 5, second conductivity type AlGaI
The nP second cladding layer 6 and the second conductivity type GaInP layer 20 are stacked in this order from the substrate 1 side.

An insulating silicon nitride film 2 is formed on the second conductivity type GaInP layer 20.
1 are formed, and a stripe-shaped groove having a width of 10 μm reaching the second conductivity type GaInP layer 20 is formed in the silicon nitride film 21.

An electrode 1 is provided on the upper surface of the above-described laminated structure and the back surface of the substrate 1.
5 and 14 are formed.

The semiconductor laser device shown in FIG. 3 is a gain waveguide type semiconductor laser device in which an insulating silicon nitride film 21 having a stripe-shaped groove constricts a current.

This semiconductor laser device has an oscillation threshold of 93 mA, and can continuously emit visible light at room temperature.

As shown in FIG. 3, many semiconductor laser devices having an AlGaInP crystal grown by the MBE method are gain waveguide type semiconductor laser devices. However, in the gain guided semiconductor laser device, the horizontal and transverse modes of the laser light are not sufficiently controlled. Therefore, there is a need for a semiconductor laser device having an AlGaInP crystal to develop a refractive index guided semiconductor laser device that is excellent in stabilizing the horizontal and transverse modes of laser light.

FIG. 4 shows a sectional view of a conventional example of a refractive index guided semiconductor laser device.

First conductivity type GaAs buffer layer 2, first conductivity type AlGaInP first cladding layer 4, GaInP active layer 5, second conductivity type AlGaInP second cladding layer 6, second conductivity type on first conductivity type GaAs substrate 1. The GaAs layer 8 and the second conductivity type InGaAs layer 30 are stacked in this order from the substrate 1 side.

GaInP active layer 5, second conductivity type AlGaInP second cladding layer 6, second conductivity type GaAs layer 8, and second conductivity type InGaAs layer 30
Is etched into a ridge shape having a width of 10 μm, and a ridge portion is formed. The surface of the ridge portion is covered with the silicon oxide layer 31 except the upper surface thereof. On the upper surface of the silicon oxide layer 31 and the back surface of the substrate 1, the electrodes 1
5 and 14 are formed.

A current flows between the electrodes 15 and 14 through the region where the silicon oxide layer 31 is not formed on the upper surface of the ridge portion.

Since the semiconductor laser device shown in FIG. 4 has the narrow active layer 5 having a width of about 10 μm, it can oscillate in a single horizontal transverse mode.

(Problems to be Solved by the Invention) However, the above-described conventional technology has the following problems.

The semiconductor laser device shown in FIG. 4 has a drawback that the heat generated in the active layer 5 is not efficiently dissipated to the outside of the device because of the voids formed on both sides of the ridge portion formed by etching. Therefore, the semiconductor laser device of FIG. 4 has a problem that it cannot continuously oscillate at room temperature.

The present invention has been made to solve the above problems, and an object thereof is a semiconductor laser device having a structure excellent in heat dissipation and capable of continuously oscillating visible light at room temperature, It is to provide the manufacturing method.

(Means for Solving the Problems) A semiconductor laser device of the present invention includes a GaAs substrate, a double heterostructure made of an AlGaInP crystal formed on the GaAs substrate, and a double heterostructure formed on the double heterostructure (Al _X Ga _1-X )
_0.5 In _0.5 P etching stop layer (0 <X ≦ 1), a GaAs light absorption layer having a stripe groove formed on the etching stop layer and reaching the etching stop layer,
The regrown AlGa formed on the etching stop layer and the GaAs light absorption layer so as to fill the stripe groove.
An As layer, and an Al _X Ga _1-X As layer or an Al As layer having a thickness of several molecular layers is formed on the surface of the etching stop layer.
The AlGaAs layer has a bandgap energy that is larger than the energy value of the light generated in the double heterostructure, thereby achieving the above object.

Further, an (Al _Y Ga _{1 -Y} ) _0.5 In _0.5 P etching stop layer (0 ≦ Y ≦ 1) may be provided between the upper surface of the GaAs light absorption layer and the lower surface of the AlGaAs layer.

The manufacturing method of the present invention comprises a step of forming a double heterostructure composed of an AlGaInP crystal on a GaAs substrate, and a band having a value larger than the energy value of light generated in the double heterostructure on the double heterostructure. (Al _X Ga _1-X ) _0.5 In _0.5 P etching stop layer (0
<X ≦ 1), a step of forming a GaAs light absorption layer on the etching stop layer, a step of forming a stripe groove reaching the etching stop layer in the GaAs light absorption layer, and an MBE device. Inside, while irradiating the GaAs substrate with As molecular beam, the temperature of the GaAs substrate is raised to a temperature above the temperature at which In and P of the etching stop layer evaporate,
A step of changing a few molecular layers near the surface of the etching stop layer exposed in the stripe groove into an Al _X Ga _1-X As layer, and occurring in the double hetero structure in the MBE device Forming an AlGaAs layer having a bandgap energy larger than the energy value of light on the Al _X Ga _1-X As layer and the GaAs light absorption layer so as to fill the stripe groove. The above object is achieved thereby.

Further, a step of forming a double hetero structure made of AlGaInP crystal on the GaAs substrate, and a step of forming the double hetero structure on the double hetero structure.
It has a bandgap energy larger than that of light generated in the double heterostructure (Al _X G
a _1-X ) _0.5 In _0.5 P Etching stop layer (0 <X ≦ 1)
And a step of forming a GaAs light absorption layer on the (Al _X Ga _1-X ) _0.5 In _0.5 P etching stop layer,
A GaAs optical absorption _{layer, (Al Y Ga 1-Y} ) 0.5 In 0.5 P and forming an etch stop layer (0 ≦ Y ≦ 1), the (Al _X G
a _1-X ) _0.5 In _0.5 P etching stop layer is formed in the (Al _Y Ga _1-Y ) _0.5 In _0.5 P etching stop layer and the GaAs light absorption layer, and in the MBE device, While irradiating the As molecular beam onto the GaAs substrate, the Ga
The temperature of the As substrate is raised above the temperature at which In and P of the etching stop layer evaporate, and several molecular layers in the vicinity of the surface of the etching stop layer exposed in the stripe groove are replaced with Al _X Ga _1- Changing to an _X As layer and AlGaAs having a bandgap energy in the MBE device that is greater than the energy value of the light generated in the double heterostructure.
A layer such that the Al _X Ga layer fills the stripe groove.
_1-X As layer and the step of forming on the GaAs light absorption layer.

Further, a step of forming a double hetero structure made of AlGaInP crystal on the GaAs substrate, and a step of forming the double hetero structure on the double hetero structure.
It has a bandgap energy larger than that of light generated in the double heterostructure (Al _X G
a _1-X ) _0.5 In _0.5 P Etching stop layer (0 <X ≦ 1)
And a GaAs layer on the etching stop layer.
A step of forming a light absorption layer, a step of forming a stripe groove in the GaAs light absorption layer having a depth that does not reach the etching stop layer, and
While irradiating with a molecular beam, the temperature of the GaAs substrate is raised to a temperature above the temperature at which GaAs in the GaAs light absorbing layer evaporates, and the GaAs layer on the surface of the light absorbing layer evaporates. Where the etching stop layer is exposed,
A step of changing a few molecular layers near the exposed surface into an AlAs layer, and an AlGaAs layer having a bandgap energy larger than the energy value of light generated in the double heterostructure in the MBE device. Is formed on the AlAs layer and the GaAs light absorption layer so as to fill the stripe groove.

(Example) Hereinafter, the present invention will be described with reference to Examples.

FIG. 1D shows a sectional view of the semiconductor laser device according to the first embodiment. In this semiconductor laser device,
A first conductivity type GaAs buffer layer 2, on a conductivity type GaAs substrate 1,
First conductivity type GaInP buffer layer 3, first conductivity type AlGaInP first
Cladding layer 4, GaInP active layer 5, second conductivity type AlGaInP second
Cladding layer 6, (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P first etching stop layer 7, GaAs light absorbing layer 8, and (Al _0.4 Ga _0.6 ).
_{The 0.5} In _0.5 P second etching stop layer 9 is laminated in this order from the substrate 1 side.

The GaAs light absorption layer 8 and the (Al _0.4 Ga _0.6 ) _0.5 In _0.5 P second etching stop layer 9 include (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P.
A stripe groove (width: 5 μm) reaching the first etching stop layer 7 is formed.

At the bottom of the stripe groove, (Al _0.7 Ga _0.3 ) _0.5 In _0.5
On the surface of the P first etching stop layer 7, several molecular layers
An Al _0.7 Ga _0.3 As layer 10 is formed. On the other hand, (Al _0.4 Ga
_0.6 ) _0.5 In _0.5 P A few molecular layers of Al _0.4 Ga _0.6 layer 16 are also formed on the surface of the second etching stop layer 9.

The second conductivity type Al is formed so as to fill the stripe groove.
_0.7 Ga _0.3 As regrown clad layer 11 is GaAs layer 8, Al _0.7 Ga
It is formed on the _0.3 As layer 10 and the Al _0.4 Ga _0.6 layer 16.

First conductivity type AlGaInP first cladding layer 4, GaInP active layer 5
A double hetero structure is composed of the second conductivity type AlGaInP second cladding layer 6 and most of the light generated in the active layer 5 is confined in the double hetero structure.

The band gap energy of the GaAs layers 8 located on both sides of the stripe groove is smaller than the energy of light generated in the active layer 5, and the light generated in the active layer 5 is easily absorbed. However, the Al _0.7 Ga _0.3 As regrown cladding layer 11 is designed to have a sufficiently large bandgap and a sufficiently small refractive index necessary for confining the light generated in the active layer 5 in the double heterostructure. .

With the above structure, an effective refractive index difference is generated inside and outside the stripe groove provided above the double hetero structure, and the horizontal transverse mode of the laser light is unified.

On the second conductivity type Al _0.7 Ga _0.3 As regrown cladding layer 11,
The second conductivity type GaAs cap layer 12 is formed, and the second conductivity type Ga is formed.
Electrodes 15 and 14 are formed on the upper surface of the As cap layer 12 and the back surface of the substrate 1, respectively.

Next, a method of manufacturing the above semiconductor laser device will be described with reference to FIGS.

First, as shown in FIG. 1A, a first conductivity type GaAs buffer layer 2 and a first conductivity type Ga
InP buffer layer 3, first conductivity type AlGaInP first cladding layer 4, GaInP active layer 5, second conductivity type AlGaInP second cladding layer 6, (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P first etching stop layer 7, GaAs Light absorption layer 8 and (Al _0.4 Ga _0.6 ) _0.5 In _0.5 P
The second etching stop layer 9 was continuously grown in this order from the substrate 1 side by the MBE method (FIG. 1 (a)). The substrate temperature during growth was set to be in the range of about 480 ° C to about 570 ° C.

In order to maintain the cleanliness of the growth layer, the substrate 1 was not taken out of the MBE device during the step of growing each layer.

Further, the total layer thickness of the second conductivity type AlGaInP second cladding layer 6 and the second conductivity type (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P first etching stop layer 7 is such that the light generated in the active layer 5 is GaAs. It was set to about 2000 Å so as to leak to the light absorption layer 8.

After forming the (Al _0.4 Ga _0.6 ) _0.5 In _0.5 P second etching stop layer 9, the substrate 1 was taken out of the MBE apparatus. Therefore, a portion of the (Al _0.4 Ga _0.6 ) _0.5 In _0.5 P second etching stop layer 9 and the GaAs light absorption layer 8 is selectively etched using the photomask 13 to obtain (Al _0.7 Ga
_0.3 ) _0.5 In _0.5 P A stripe groove reaching the first etching stop layer 7 is formed (FIG. 1 (b)).

After the etching process for forming the stripe groove, impurities such as oxygen and water vapor are adsorbed on the surface of the second conductivity type AlGaInP first etching stop layer 7 by contact with the atmosphere and the like. Due to such impurities, the second conductivity type AlGa
When the surface of the InP first etching stop layer 7 is contaminated,
The crystallinity of the other layer grown on that layer will deteriorate.

After introducing the substrate 1 into the MBE device again, (Al _0.7 G
a _0.3 ) _0.5 In _0.5 P First etching stop layer 7 and (Al
_0.4 Ga _0.6 ) _0.5 In _0.5 P In order to clean the surface of the second etching stop layer 9, (Al _0.7 Ga _0.3 )
While irradiating a sufficient amount of As molecular beam to _0.5 In _0.5 P7 and (Al _0.4 Ga _0.6 ) _0.5 In _0.5 P layer 9, the substrate temperature is adjusted to 62
A step of raising the temperature to 0 ° C. and maintaining the state for several minutes was performed.

By this step, In and P in the vicinity of the surface of the (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P first etching stop layer 7 and the (Al _0.4 Ga _0.6 ) _0.5 In _0.5 P second etching stop layer 9 are changed to As.
By substituting As for the molecular beam, these (Al _0.7 Ga
_{0.3) 0.5} In _0.5 P layer 7 (and Al _0.4 Ga _{0.6) 0.5} In _0.5 number molecular layer in the vicinity of the surface of the P layer 9 are each, having molecular layer Al _0.7 Ga
_{It changed into 0.3} As layer 10 and Al _0.4 Ga _0.6 As layer 16 (FIG. 1 (c)).

At this time, (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P layer 7 and (Al
_The contaminants were removed from the surface of the _0.4 Ga _0.6 ) _0.5 In _0.5 P layer 9 and the surface thereof was cleaned.

In addition, a few molecular layers of Al _0.7 Ga formed by this process
_0.3 As layer 10 and Al _0.4 Ga _0.6 As layer are
It is a layer made of a thermally stable material in which the compositional elements hardly evaporate. Therefore, (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P layer 7 and (Al _0.4 G
The vaporization of In or P from the a _0.6 ) _0.5 In _0.5 P layer 9 was prevented by being covered with the Al _0.7 Ga _0.3 As layer 10 and the Al _0.4 Ga _0.6 As layer 16 of these few molecular layers.

In the present embodiment, the substrate temperature during the above step was 620 ° C. as described above, but the Al _0.7 Ga _0.3 As layer 10 and the Al _0.4 Ga _0.6 As layer 10 were formed.
In order to form the layer 16, this temperature may be set to about 580 ° C. or higher at which In is evaporated. At the temperature at which evaporation of In occurs, P also evaporates, so by irradiating a sufficient amount of As molecular beam, In and P are replaced with As,
An Al _0.7 Ga _0.3 As layer 10 and an Al _0.4 Ga _0.6 As layer 16 are formed.

However, Al _0.7 Ga _0.3 formed by irradiation with As molecular beam
In order for the As layer 10 and the Al _0.4 Ga _0.6 As layer 16 to exist stably during the above steps, the substrate temperature is preferably about 680 ° C. or lower.

Then, the second conductivity type Al _0.7 Ga _0.3 As regrowth cladding layer 11 and the second conductivity type GaAs cap layer 12 are sequentially formed from the substrate 1 side in this order from the substrate 1 side by MBE at a substrate temperature of about 600 ° C.
A step of growing the _0.7 Ga _0.3 As layer 10 and the like so as to fill the stripe groove was performed.

At the temperature required to grow the second conductivity type Al _0.7 Ga _0.3 As regrown cladding layer 11, it is usually (Al _0.7 G
a _0.3 ) _0.5 In _0.5 P layer 7 and the (Al _0.4 Ga _0.6 ) _0.5 In _0.5 P layer 9 are significantly deteriorated due to evaporation of In or P. However, in the present embodiment, the thermally stable Al _0.7 Ga _0.3 As layer 10 and Al
_{Due to the 0.4} Ga _0.6 As layer 16, deterioration of the (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P layer 7 and the (Al _0.4 Ga _0.6 ) _0.5 In _0.5 P layer 9 could be prevented.

By adjusting the Al mixed crystal ratio of the Al _0.7 Ga _0.3 As regrown cladding layer 11, the regrown cladding layer 11 having a bandgap energy larger than the energy value of light generated in the active layer 5 was formed. . In this way, the light generated in the active layer 5 can be confined in the double hetero structure.

By forming electrodes 15 and 14 on the upper surface of the laminated structure thus formed and the back surface of the substrate 1, the index-guided semiconductor laser device shown in FIG.

The semiconductor laser device of the present example has a double hetero structure made of AlGaInP and was able to continuously oscillate light having a wavelength of 670 nm at room temperature. Further, since this semiconductor laser device is of a refractive index guided type having a stripe groove inside the device, the horizontal transverse mode of the oscillated laser light is unified.

Since the semiconductor laser device of this embodiment has the second conductivity type AlGaAs regrowth cladding layer 11 made of AlGaAs, which is relatively excellent in thermal conductivity, the heat generated in the active layer 5 is efficiently generated by the semiconductor. It was diffused out of the laser element. Therefore, it was possible to achieve temperature characteristics superior to those of the semiconductor laser device shown in FIG.

In this embodiment, as the etching stop layer, (Al
_0.7 Ga _0.3 ) _0.5 In _0.5 P layer 7 and (Al _0.4 Ga _0.6 ) _0.5 In _0.5
Although the P layer 9 is used, the layer can be lattice-matched to the substrate by using an etching stop made of an AlGaInP layer having another composition ratio. Thus, since the etching stop layer of the present invention is composed of the AlGaInP layer,
Compared to the aAs layer, it is possible to achieve lattice matching with the substrate even if the composition ratio is changed in a wider range. If a lattice mismatch occurs at the bottom of the stripe groove, the light emission efficiency is lowered, so that there is a problem that it is not possible to obtain a laser beam with a high optical output. However, in this embodiment, the lattice mismatch does not occur. , There was no such problem. Further, the AlGaAs layer formed on the surface of the AlGaInP layer has a characteristic of being less likely to be contaminated with impurities such as oxygen than the AlAs layer not containing Ga, for example.

As described above, according to the configuration of this embodiment, there is an advantage that the lattice mismatch is small and a high luminous efficiency can be obtained, and further, the etching stop layer is not easily contaminated during the manufacturing process.

According to the manufacturing method of this embodiment, the surfaces of the etching stop layers 7 and 9 whose surfaces are contaminated by taking out the substrate 1 once from the MBE apparatus are cleaned in the MBE apparatus, and a good quality AlGaAs The growth clad layer 11 could be grown.

In the semiconductor laser device thus manufactured, the AlGaAs layers 10 and 16 which are more thermally stable than these layers are formed on the surfaces of the etching stop layers 7 and 9, so that the heat of the surfaces of the etching stop layers 7 and 9 is heated. Deterioration due to is prevented. As a result, the number of crystal defects at the interface between these layers at the bottom of the stripe groove and the AlGaAs regrown cladding layer 11 was reduced to such an extent that it did not matter.

However, in the semiconductor laser device (comparative example) manufactured by the method described above, in which the step of raising the substrate temperature to 620 ° C. while irradiating the As molecular beam is omitted, the oscillation threshold increases, so It was not possible to realize continuous oscillation. This is the second conductivity type AlGaIn of the comparative example.
The surface of the P first etching stop layer 7 is not cleaned,
This is because the high quality AlGaAs regrown cladding layer 11 could not be grown on it.

Since the Al _0.7 Ga _0.3 As layer 10 and the Al _0.4 Ga _0.6 As layer 16 are thin layers made up of several molecular layers, they have a direct optical and electrical effect on the characteristics of the semiconductor laser device. There wasn't.

In the semiconductor laser device of this example, the second etching stop layer 9 is formed on the light absorption layer 8 (Al _0.4 G).
a _0.6 ) _0.5 In _0.5 P layer, so AlGaAs regrown layer
The crystallinity of the portion 11 of the AlGaAs above the light absorption layer 8 was as excellent as the crystallinity of the AlGaAs regrowth layer 11 grown on the strip groove where the light absorption layer 8 was removed.

However, in the portion of the AlGaAs regrowth layer 11 above the light absorption layer 8, the light leakage generated in the active layer 5 is small.
Therefore, the semiconductor laser device having the structure of the above-described embodiment except for the second etching stop layer 9 also stably oscillated at room temperature, like the semiconductor laser device of the above embodiment.

FIG. 2D shows a sectional view of a semiconductor laser device of another embodiment. The main difference between this embodiment and the embodiment of FIG. 1 (d) is that (Al _0.4 Ga _0.6 ) is present on the light absorption layer 8 of this embodiment.
_{There is no 0.5} In _0.5 P layer, and an Al _0.7 Ga _0.3 As layer is formed on the etching stop layer at the bottom of the stripe groove.
In place of 10, an AlAs layer 19 is formed.

A method for manufacturing the semiconductor laser device will be described below with reference to FIGS. 2 (a) to 2 (d).

First, as shown in FIG. 2 (a), the first conductivity type GaAs buffer layer 2 and the first conductivity type Ga are formed on the first conductivity type GaAs substrate 1.
InP buffer layer 3, first conductivity type AlGaInP first cladding layer 4, GaInP active layer 5, second conductivity type AlGaInP second cladding layer 6, (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P etching stop layer 7, and GaAs light The absorption layer 8 in this order from the substrate 1 side,
It was grown by the MBE method. Here, the second conductivity type AlGaInP second cladding layer 6 and the second conductivity type (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P
The total thickness of the etching stop layer 7 and the etching stop layer 7 is 25 so that the light generated in the active layer 5 leaks to the GaAs light absorption layer 8.
It was about 00Å.

After this, once remove the board 1 from the MBE device,
By selectively etching a part of the aAs light absorption layer 8 using the photomask 13, (Al _0.7 Ga _0.3 ) _0.5 In
Do not reach the _0.5 P etching stop layer 7,
Striped grooves were formed (Fig. 2 (b)). Ga has a thickness of about 1000Å between the bottom surface of the stripe groove and the top surface of the (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P etching stop layer 7.
The As layer is left.

 Thereafter, the substrate 1 was again introduced into the MBE apparatus.

Next, in the MBE device, the substrate whose upper surface is covered with the GaAs layer is irradiated with a sufficient amount of As molecular beam, the substrate temperature is raised to 720 ° C., and the state is maintained for several minutes. I went through the process.

By this process, Ga remaining on the bottom of the stripe groove
As evaporates, then exposed (Al _0.7 Ga _0.3 ) _0.5 In _0.5
Ga, In and P near the surface of the P etching stop layer 7
Replaced with As in the As molecular beam. Thus, several molecular layers near the surface of the (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P layer 7 at the bottom of the stripe groove were changed to several AlAs layers 19 (FIG. 2 (c)).

This AlAs layer 19 of several molecular layers, even at about 720 ℃,
It is a layer made of a thermally stable material that does not cause significant vaporization of constituent elements. Therefore, In or P from the (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P layer 7 that should normally occur at about 720 ° C.
Evaporation was prevented by being covered with this few molecular layers of AlAs layer 19.

In this example, the substrate temperature during the above step was 720 ° C. as described above, but in order to form the AlAs layer 19, this temperature is 680 ° C. which is the temperature at which Ga and As vaporize. It should be above a certain level. At the temperature at which Ga and As vaporize, In and P also vaporize. Therefore, by irradiating a sufficient amount of As molecular beam, the Ga of the exposed portion of the (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P layer 7, In and P replace As, and the AlAs layer 19
Is formed.

However, the AlAs layer 19 formed by As molecular beam irradiation
However, the substrate temperature is preferably about 740 ° C. or lower in order to stably exist even in the above process.

Thus, by leaving the GaAs layer at the bottom of the stripe groove when forming the stripe groove, (Al _0.7 Ga _0.3 ) _0.5 In
It was possible to prevent contamination of the surface of the _0.5 P layer 7 without exposing the surface in the atmosphere.

The surface of the GaAs layer contaminated by contact with the atmosphere was cleaned by evaporating the layer near the surface of the GaAs layer by the process performed in the MBE apparatus.

Furthermore, due to the AlAs layer 19 formed by the irradiation of As molecular beam, it is originally remarkable at about 580 ° C or higher (A
l _0.7 Ga _0.3 ) _0.5 In _0.5 It was possible to prevent deterioration of the P layer 7 due to evaporation of In or P.

After the above steps, the second conductivity type Al _0.7 Ga _0.3 As regrowth cladding layer 11 and the second conductivity type GaAs cap layer 12 are grown in this order from the substrate 1 side on the Al _0.7 Ga _0.3 As layer 10 by the MBE method. Was performed.

The AI mixed crystal ratio of this Al _0.7 Ga _0.3 As regrown cladding layer 11 is
It is designed to have a sufficiently low refractive index necessary for confining the light generated in the active layer 5 in the active layer 5.

By forming electrodes 15 and 14 on the upper surface of the laminated structure thus formed and the back surface of the substrate 1, the index guided semiconductor laser element shown in FIG. 2D is formed.

In each of the semiconductor laser devices described above, the double hetero structure is composed of the first conductivity type AIGaInP first cladding layer 4, the GaInP active layer 5, and the second conductivity type AlGaInP second cladding layer 6, The structure may be formed of another formed AlGaInP-based semiconductor layer. For example, as the first and second cladding layers 4 and 6, layers made of AIInP ternary mixed crystal may be used. Further, a layer made of AlGaInP quaternary mixed crystal may be used as active layer 5. Further, as the active layer 5, a layer having a quantum well structure or a superlattice structure may be used. Further, the SCH structure may be formed by providing a guide having a small gain or absorption loss between the clad layer and the active layer 5.

(Effect of the Invention) As described above, since the semiconductor laser device of the present invention has the AlGaAs layer having relatively excellent thermal conductivity, the heat generated in the double hetero structure made of AlGaInP is efficiently transferred to the semiconductor. It can be dissipated outside the laser element. In addition, it is of a refractive index waveguide type with a stripe structure provided inside. Therefore, the semiconductor laser device of the present invention exhibits excellent temperature characteristics and is capable of continuously oscillating visible light in the horizontal transverse mode even at room temperature.

Also, according to the method of the present invention, the AlGaInP etching stop layer surface is cleaned in the MBE apparatus before growing the AlGaAs layer, and yet a thermally stable amount is formed on the surface of the etching stop layer. Therefore, an AlGaAs layer having excellent crystallinity can be grown on it.

Therefore, according to the method of the present invention, it is possible to provide a visible light semiconductor laser device having a small light absorption loss in the stripe groove and a low oscillation threshold.

[Brief description of drawings]

1 (a) to 1 (d) are sectional views for explaining the method for manufacturing a semiconductor laser device of the present invention, and FIGS. 2 (a) to 2 (d).
FIG. 4 is a sectional view for explaining another method of manufacturing a semiconductor laser device, FIG. 3 is a sectional view showing a conventional example, and FIG. 4 is a sectional view showing another conventional example. 1 ... First conductivity type GaAs substrate, 2 ... First conductivity type GaAs buffer layer, 3 ... First conductivity type GaInP buffer layer, 4 ... First conductivity type AlGaInP first cladding layer, 5 ... GaInP activity layer,
6 ... Second conductivity type AlGaInP second cladding layer, 7 ... AlGaI
nP first etching stop layer, 8 ... GaAs light absorption layer, 9
…… AlGaInP second etching stop layer, 10 …… AlGaAs
Layer, 11 ... Second conductivity type Al _0.7 Ga _0.3 As regrown cladding layer,
12 ... Second conductivity type GaAs cap layer, 14, 15 ... Electrode, 19
...... AlAs layer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Naohiro Suyama 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Within Sharp Corporation (72) Inventor Matsui Kanekaku 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Sharp shares In-house (56) References Japanese Patent Laid-Open No. 1-168091 (JP, A)

Claims (5)

(57) [Claims] 1. A GaAs substrate, a double heterostructure composed of an AlGaInP crystal formed on the GaAs substrate, and (Al _X Ga _1-X ) _0.5 In formed on the double heterostructure.
_0.5 P etching stop layer (0 <X ≦ 1), a GaAs light absorption layer having a stripe groove formed on the etching stop layer and reaching the etching stop layer, and the etching so as to fill the stripe groove. Regrown AlGa formed on the stop layer and the GaAs light absorption layer
And an As layer, and an Al _X Ga _1-X As layer or an Al As layer having a thickness of several molecular layers is formed on the surface of the etching stop layer. The AlGaAs layer has a bandgap energy that is larger than the energy value of light generated in the double hetero structure. 2. An (Al _Y Ga _{1 -Y} ) _0.5 In _0.5 P etching stop layer (0 ≦ Y ≦ 1) is also provided between the upper surface of the GaAs light absorbing layer and the lower surface of the AlGaAs layer. 1. The semiconductor laser device according to item 1. 3. A step of forming a double heterostructure made of AlGaInP crystal on a GaAs substrate, and a bandgap energy having a value larger than an energy value of light generated in the double heterostructure on the double heterostructure. Forming (Al _X Ga _1-X ) _0.5 In _0.5 P etching stop layer (0 <X ≦ 1), forming a GaAs light absorption layer on the etching stop layer, and the etching stop A stripe groove reaching the layer
The step of forming the light absorption layer, and the temperature of the GaAs substrate is controlled by irradiating the GaAs substrate with an As molecular beam in the MBE device.
Raising the temperature above the temperature at which In and P evaporate to change several molecular layers near the surface of the etching stop layer exposed in the stripe groove into an Al _X Ga _1-X As layer; In the device, an AlGaAs layer having a band gap energy larger than the energy value of light generated in the double heterostructure is embedded in the stripe groove so that the Al _X Ga _1-X As layer and the Al A method of manufacturing a semiconductor laser device, comprising: a step of forming on a GaAs light absorption layer; 4. A step of forming a double heterostructure made of an AlGaInP crystal on a GaAs substrate, and a bandgap energy having a value larger than an energy value of light generated in the double heterostructure on the double heterostructure. in the a _{(Al X Ga 1-X)} 0.5 in 0.5 P etching stop layer and forming a (0 <X ≦ 1), the _{(Al X Ga 1-X)} 0.5 in 0.5 P etching stop layer,
Forming a GaAs optical absorption layer, on the GaAs optical absorption _{layer, (Al Y Ga 1-Y} ) 0.5 In 0.5 P and forming an etch stop layer (0 ≦ Y ≦ 1), the (Al _X Ga _1-X ) _0.5 In _0.5 P etching stop layer is formed in the (Al _Y Ga _1-Y ) _0.5 In _0.5 P etching stop layer and the GaAs light absorption layer, and in the MBE device, While irradiating the GaAs substrate with an As molecular beam, the temperature of the GaAs substrate is adjusted to the temperature of the etching stop layer.
Raising the temperature above the temperature at which In and P evaporate to change several molecular layers near the surface of the etching stop layer exposed in the stripe groove into an Al _X Ga _1-X As layer; In the device, an AlGaAs layer having a band gap energy larger than the energy value of light generated in the double heterostructure is embedded in the stripe groove so that the Al _X Ga _1-X As layer and the Al A method of manufacturing a semiconductor laser device, comprising: a step of forming on a GaAs light absorption layer; 5. A step of forming a double heterostructure made of an AlGaInP crystal on a GaAs substrate, and a bandgap energy having a value larger than an energy value of light generated in the double heterostructure on the double heterostructure. Forming (Al _X Ga _1-X ) _0.5 In _0.5 P etching stop layer (0 <X ≦ 1), forming a GaAs light absorption layer on the etching stop layer, and the etching stop A step of forming a stripe groove having a depth that does not reach the layer in the GaAs light absorption layer; and, while irradiating the GaAs substrate with an As molecular beam in the MBE device, the temperature of the GaAs substrate is changed to the GaAs substrate. In the stripe groove, by elevating the temperature above the temperature at which GaAs in the light absorbing layer evaporates and evaporating the GaAs layer on the surface of the light absorbing layer,
A step of exposing the etching stop layer and changing a few molecular layers in the vicinity of the exposed surface into an AlAs layer; and a value larger than the energy value of light generated in the double hetero structure in the MBE device. And a step of forming an AlGaAs layer having a bandgap energy on the AlAs layer and the GaAs light absorption layer so as to fill the stripe groove.