JP2002134836A - Semiconductor light emitting device and manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a semiconductor light emitting device capable of driving at low voltage with high output and a small interval of light emitting points. SOLUTION: At least a first conductive clad layer 2, an active layer 3, second conductive clad layers 4 and 6, a second conductive contact layer 7, second conductive clad layers 8 and 10, an active layer 11, a first conductive clad layer 12, and a first conductive contact layer 13 are formed sequentially on a first conductive semiconductor substrate 1. The layers on the second conductive contact layer 7 corresponding to one part of the second conductive contact layer 7 are cut to expose the part of the second conductive contact layer 7. An electrode 16 is formed in the exposed region of the second conductive contact layer 7 while each electrode 17 or 15 is formed at the first conductive semiconductor substrate 1 and the first conductive contact layer 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a semiconductor light emitting device in which two semiconductor laser elements driven in parallel with each other are stacked on a common substrate.

The present invention also relates to a method for manufacturing such a semiconductor light emitting device.

[0003]

2. Description of the Related Art Recently, high-output semiconductor lasers having a wide light-emitting region have been attracting attention for printing equipment, medical use, industrial processing, and excitation of solid-state lasers. This is because semiconductor lasers are smaller, have lower power consumption, and are less expensive than other gas lasers or solid-state lasers. The semiconductor laser used here is required to have a very high output, and a normal single-mode laser emits light from a light emitting region having a width of about 3 μm, whereas a light emitting region having a width of 10 μm or more is formed. High output has been achieved.

[0004] In addition, a stack type semiconductor laser disclosed in, for example, Japanese Patent Application Laid-Open No. 07-307520 is known as a semiconductor laser with high output. This stack type semiconductor laser has a structure in which ordinary semiconductor laser chips are vertically stacked in multiple stages to achieve high output.
FIG. 3 shows such a stacked semiconductor laser.
The semiconductor laser chips 30 and 31 are illustrated as being stacked in two stages.

[0005]

However, enlarging the light emitting area in order to increase the light output, on the contrary, also impairs the light collecting characteristics. Since the conventional stacked semiconductor laser has a structure in which semiconductor laser chips are vertically stacked in multiple stages, each light emitting point (30 a in FIG.
And the distance between 31a) is increased to about 100 μm. Therefore,
For example, when this stack type semiconductor laser is to be coupled to an optical fiber, it becomes difficult to condense the light, and it is necessary to devise a lens system between the semiconductor laser and the optical fiber.

In addition, since the conventional stacked semiconductor laser has a structure in which diodes are electrically connected in series, there is also a problem that a driving voltage is high and a large load is applied to a power supply.

Further, in this conventional stacked semiconductor laser, it is difficult to stack a plurality of semiconductor laser chips in such a manner that their light emitting points are aligned in a horizontal direction (a direction perpendicular to the stacking direction). Therefore, there is also a problem that the yield in manufacturing is low.

As described above, the conventional stacked semiconductor laser has a large light emitting area when viewed optically, has a high driving voltage when electrically stated, and it is difficult to stack light emitting points in a manufacturing method. There are drawbacks. For this reason, it has been difficult to use a semiconductor laser having such a stack structure to achieve high output in fields such as printing, medical care, industry, and measurement.

In view of the above circumstances, it is an object of the present invention to provide a semiconductor light emitting device which has a small interval between light emitting points, can be driven at a low voltage, and can obtain a high output.

Another object of the present invention is to provide a method capable of manufacturing such a semiconductor light emitting device at a high yield.

[0011]

In the semiconductor light emitting device according to the present invention, two layers each constituting a semiconductor laser element are formed on one substrate, and these elements are driven in parallel. More specifically, at least a first conductive type semiconductor substrate is provided on one first conductive type semiconductor substrate.
A conductive type clad layer, an active layer, a second conductive type clad layer, a second conductive type contact layer, a second conductive type clad layer, an active layer, a first conductive type clad layer, and a first conductive type contact layer are formed in this order. A layer above the second conductive type contact layer is cut off at a portion corresponding to the partial region so that a partial region of the second conductive type contact layer is exposed; And an electrode is formed on the first conductivity type semiconductor substrate and the first conductivity type contact layer.

The first conductivity type and the second conductivity type are one and the other of n-type and p-type. In the present invention, in particular, the first conductivity type is p-type and the second conductivity type is Desirably, it is n-type.

Further, in the semiconductor light emitting device according to the present invention having the above structure, at least one of the first and second conductive type cladding layers sandwiching one of the two active layers,
In at least one of the first and second conductivity type cladding layers sandwiching the other of the two active layers, a current blocking layer for selectively passing a current to a partial region of the active layer is formed. Desirably, the layers are formed in such a manner that the ranges in which current flows selectively match each other.

The current blocking layer as described above is preferably formed from a layer in which a current blocking portion other than a range in which current flows selectively is selectively oxidized. As a material constituting the current blocking layer having the current blocking portion thus selectively oxidized, for example, AlAs can be suitably used.

On the other hand, the method of manufacturing a semiconductor light emitting device according to the present invention is a method of manufacturing a semiconductor light emitting device in which a current blocking layer made of AlAs or the like is formed in two cladding layers of the second conductivity type as described above. Forming two grooves extending perpendicularly to the layer on the substrate on which each layer including the material layer serving as a current blocking layer is formed, and forming a state in which water vapor enters these two grooves. Heat-treating the material layer from the groove side for a predetermined time to selectively oxidize a portion of the material layer which has entered a predetermined distance inward from each groove in a portion between the two grooves. is there.

[0016]

In the semiconductor light emitting device according to the present invention, at least the first conductive type semiconductor substrate is provided on one first conductive type semiconductor substrate.
A conductive type clad layer, an active layer, a second conductive type clad layer, a second conductive type contact layer, a second conductive type clad layer, an active layer, a first conductive type clad layer, and a first conductive type contact layer are formed in this order. As a result, one semiconductor laser device is formed below the second conductivity type contact layer (substrate side), and another semiconductor laser device is formed above the contact layer. As described above, if a layer for two elements is stacked on the substrate,
Compared to the case where semiconductor laser chips are separately manufactured and then stacked and fixed, the distance between two active layers, that is, the distance between light emitting points can be made smaller. If the light emitting region is formed small in this way, it becomes easier to focus the laser beam emitted therefrom.

Further, in the semiconductor light emitting device according to the present invention, the electrode is formed on the second conductivity type contact layer formed between the layers constituting the two semiconductor laser elements as described above, and the first conductivity type contact layer is formed. Type semiconductor substrate and first
Since the electrodes are formed on the conductive type contact layer, current flows between the second conductive type contact layer and the first conductive type semiconductor substrate and between the second conductive type contact layer and the first conductive type contact layer. It will flow. That is, the two semiconductor laser elements are driven in parallel with each other using the electrode formed on the second conductivity type contact layer as a common electrode. Accordingly, the semiconductor light emitting device of the present invention can be driven at a lower voltage as compared with a device in which two semiconductor laser elements are driven in series, and has an effect of reducing a load on a power supply.

Further, in the semiconductor light emitting device according to the present invention, in particular, each of the two second conductivity type cladding layers is
When a current blocking layer for selectively flowing a current is formed in a partial region of the active layer, and these two current blocking layers are formed in a state where the ranges for selectively flowing the current match each other, 2 The ranges in which the current flows in the active layers of the two semiconductor laser elements are matched with each other. Therefore, the light emitting point does not shift in the horizontal direction (the direction perpendicular to the layer stacking direction) between the two semiconductor laser elements, and the size of the light emitting point in the horizontal direction is sufficiently small.

On the other hand, in the method of manufacturing a semiconductor light emitting device according to the present invention, as described above, a semiconductor light emitting device having two current blocking layers formed in such a manner that the ranges where currents flow selectively match each other is manufactured. At this time, in the layer on the substrate on which each layer including the material layer serving as the current blocking layer is formed, two grooves extending perpendicularly to the layer are formed, and the two grooves are in a state where water vapor enters. The material layer is heat-treated from the groove side for a predetermined time to selectively oxidize a portion of the material layer that is inside a predetermined distance from each groove in a portion between the two grooves. The area to be selectively oxidized from the above-mentioned groove is equal to each other between the two material layers. Therefore, the portion of the material layer that is not affected by selective oxidation,
In other words, the portion where the current flows when the current blocking layer is formed also matches each other between the two material layers.

As described above, according to the method of manufacturing a semiconductor light emitting device according to the present invention, two current blocking layers can be formed in a state where the ranges in which current flows selectively are matched with each other. Semiconductor light emitting devices whose light emitting points are not shifted from each other in the horizontal direction can be manufactured with a high yield.

In the method of manufacturing a semiconductor light emitting device,
After forming each layer on the substrate, the current blocking layer is formed by selective oxidation using the groove, so that each layer on the substrate can be formed by one crystal growth, and the current blocking layer can be easily formed. It can be formed. Therefore, according to this method,
A high-output semiconductor light emitting device can be manufactured at low cost.

[0022]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a perspective view of a semiconductor laser device according to an embodiment of the present invention, and FIG. 2 explains a process of manufacturing the semiconductor laser device.

As shown in FIG. 1, this semiconductor laser device has a p-AlGaAs first cladding layer 2 on a p-GaAs substrate 1.
AlGaAs first active layer 3, n-AlGaAs second cladding layer 4, 1A
lAs selective oxidation current blocking layer 5, n-AlGaAs third cladding layer 6, n-GaAs contact layer 7, n-AlGaAs fourth cladding layer 8, second AlAs selective oxidation current blocking layer 9, n-AlGaAs fifth cladding layer 10 , An AlGaAs second active layer 11, a p-AlGaAs sixth cladding layer 12, and a p-GaAs contact layer 13 are laminated in this order.

Then, the p-GaAs contact layer 13 and the p-GaAs
On the substrate 1, p-type electrodes 15 and 17 are formed, respectively. On the other hand, the layer above the n-GaAs contact layer 7 is
The GaAs contact layer 7 is cut away to expose a part thereof,
The exposed n-GaAs contact layer 7 has an n-type electrode
16 are formed.

Further, each of the left and right sides of the p-type electrode 15 formed on the p-GaAs contact layer 13 is formed SiO ₂ insulating film 14, SiO ₂ insulating the p-type electrode 15 and the n-type electrode 16 Insulated by the membrane 14.

A method of manufacturing the semiconductor laser device according to the present embodiment will be described below with reference to FIG. First, (1)
As shown in FIG. 1, a p-AlGaAs first cladding layer 2, an AlGaAs first active layer 3, and an n-AlGaAs second cladding layer are formed on a p-GaAs substrate 1.
4. First p-AlAs layer 5m, n-AlG, which is the material layer of the current blocking layer
aAs third cladding layer 6, n-GaAs contact layer 7, n-AlGaA
s Fourth cladding layer 8, second p-A which is a material layer of the current blocking layer
The lAs layer 9m, the n-AlGaAs fifth cladding layer 10, the AlGaAs second active layer 11, the p-AlGaAs sixth cladding layer 12, and the p-GaAs contact layer 13 are formed by one crystal growth.

Next, as shown in FIG. 2B, the p-GaAs substrate 1 is subjected to dry etching so that the element width is set to the distance between the grooves.
The two grooves 20 and 21 reaching to are formed. In addition, one p-Ga
When fabricating a plurality of semiconductor laser devices using the As substrate 1, three or more grooves are formed with the above-mentioned grooves being kept at a constant interval, and the semiconductor laser devices are fabricated by the portions between the two grooves. do it.

Next, a heat treatment is performed in a steam atmosphere to form a groove.
20 and 21, the first p-AlAs layer 5m and the second p-AlAs layer 9
m is selectively subjected to steam oxidation treatment. At this time, by controlling the temperature and time of the steam oxidation treatment, the first p-AlAs layer 5m and the second p-AlAs layer 9m
Can be oxidized to a position inside the device by an arbitrary distance, so that a non-oxidized region (a in FIG.
(Range indicated by).

By the above processing, the first p-AlAs layer 5m and the second p-AlAs layer 9m each have the first AlAs selective oxidation current blocking with the non-oxidized region as the current passage range and the oxidized region outside the current blocking region. The layer 5 and the second AlAs selective oxidation current blocking layer 9 are formed.

The selective oxidation current blocking layers 5 and 9
Is formed by simultaneously receiving the steam oxidation treatment using the grooves 20 and 21 as described above, and therefore the selective oxidation ranges are equal to each other. Therefore, the current passing range composed of the non-oxidized regions of the selective oxidation current blocking layers 5 and 9 also matches each other between both layers.

In this embodiment, the element width, that is, both grooves 20, 21
The distance between them was 500 μm, and the portions of the first p-AlAs layer 5 m and the second p-AlAs layer 9 m which were respectively 200 μm inside from the grooves 20 and 21 were selectively oxidized. That is, the width of the current passing range of the selective oxidation current blocking layers 5 and 9 is 100 μm.
It is.

Then, at a position corresponding to one side of the selectively oxidized region, a part of each layer above the n-GaAs contact layer 7 is selectively dry-etched to the surface of the contact layer 7, as shown in FIG. The state shown in FIG. Then
After covering the entire surface of the device with an insulating film 14 of SiO ₂ , p
The SiO ₂ insulating film 14 is removed in a partial region on the -GaAs contact layer 13 and a partial region on the n-GaAs contact layer 7, and a p-type electrode 15 and an n-type electrode 16 are selectively provided in those regions. Form. Next, after forming a p-type electrode 17 on the back surface of the substrate 1, the device is formed by cleavage, whereby the semiconductor laser device of the present embodiment shown in FIG. 1 is completed.

The semiconductor laser device according to the present embodiment comprises a substrate 1
The semiconductor laser device is formed one by one above and below the p-GaAs contact layer 13 by the respective layers laminated thereon. In such a laminated structure, the distance between the light emitting points of the semiconductor laser elements, that is, the AlGaAs first active layer 3
The distance from the AlGaAs second active layer 11 is only a few μm, and the distance between the light emitting units in the conventional stacked semiconductor laser is about 100 μm.
It is considerably smaller than μm. Therefore, the semiconductor laser device of the present embodiment is very advantageous in condensing the laser light emitted therefrom.

Further, in the semiconductor laser device of the present embodiment, the current passing ranges (the range indicated by a in FIG. 1) of the two selective oxidation current blocking layers 5 and 9 are matched with each other.
The ranges in which the currents flow in the two active layers 3 and 11 match each other. Therefore, the light emitting point is between the two semiconductor laser devices in the horizontal direction (the direction perpendicular to the layer stacking direction).
The light emitting point size in the horizontal direction is sufficiently small.

The current blocking layer as described above is made of p-AlGaAs
First cladding layer 2 or p-AlGaAs sixth cladding layer
12, the same effect as in the present embodiment can be obtained also in this case.

In the semiconductor laser device of the present embodiment, the n-type electrode 16 is formed on the n-GaAs contact layer 7 formed between the respective layers constituting the two semiconductor laser elements as described above. , The back surface of the p-GaAs substrate 1 and
Since the p-type electrodes 17 and 15 are formed on the p-GaAs contact layer 13, respectively, the current flows between the n-GaAs contact layer 7 and the p-GaAs
The current flows between the substrate 1 and the n-GaAs contact layer 7 and the p-GaAs contact layer 13. That is, the two semiconductor laser elements are driven in parallel with each other using the n-type electrode 16 as a common electrode.

As a result, this semiconductor laser device is different from a device in which two semiconductor laser elements are driven in series.
It can be driven at a lower voltage and has an effect of reducing the load on the power supply. Specifically, it can be driven at a voltage substantially equal to that of a semiconductor laser having only one light emitting point.

If the selective oxidation method using the two trenches 20 and 21 described above is used, the two current blocking layers 5 and 9 can be used.
Can be formed so that the ranges in which current flows selectively match each other, so that a semiconductor laser device in which the light emitting points of the two semiconductor laser elements are not shifted from each other in the horizontal direction can be manufactured with a high yield.

In the method of manufacturing the semiconductor laser device according to the present embodiment, each layer on the substrate 1 can be formed by one crystal growth, and the current blocking layers 5 and 9 can be easily formed by the above-described selective oxidation method. It is. Therefore, according to this method, a high-power semiconductor laser device can be manufactured at low cost.

Although the conductivity type of each layer constituting the semiconductor light emitting device of the present invention may be opposite to that in the above-described embodiment, in order to flow a current satisfactorily, as in the above-described embodiment, the first conductive type is used. Preferably, the type is p-type and the second conductivity type is n-type.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a semiconductor laser device according to one embodiment of the present invention.

FIG. 2 is a diagram illustrating a process of manufacturing the semiconductor laser device.

FIG. 3 is a perspective view showing an example of a conventional stacked semiconductor laser.

[Explanation of symbols]

Reference Signs List 1 p-GaAs substrate 2 p-AlGaAs first cladding layer 3 AlGaAs first active layer 4 n-AlGaAs second cladding layer 5 first AlAs selective oxidation current blocking layer 5 m first p-AlAs layer 6 n-AlGaAs third cladding layer 7 n-GaAs contact layer 8 n-AlGaAs fourth cladding layer 9 second AlAs selective oxidation current blocking layer 9 m second p-AlAs layer 10 n-AlGaAs fifth cladding layer 11 AlGaAs second active layer 12 p-AlGaAs sixth cladding layer 13 p-GaAs contact layer 14 SiO ₂ insulating film 15, 17 p-type electrode 16 n-type electrode 30, 31 semiconductor laser chip

Claims (7)

[Claims] 1. A semiconductor device comprising at least a first conductive type clad layer, an active layer, a second conductive type clad layer, a second conductive type contact layer, a second conductive type clad layer, and an active layer on one first conductive type semiconductor substrate. A first conductive type clad layer and a first conductive type contact layer are formed in this order, and the second conductive type contact layer is formed in a portion corresponding to the second conductive type contact layer so that a part of the second conductive type contact layer is exposed. A layer above the mold contact layer is cut off, an electrode is formed in the exposed part of the second conductivity type contact layer, and an electrode is formed on the first conductivity type semiconductor substrate and the first conductivity type contact layer. A semiconductor light-emitting device characterized by having a pattern formed thereon. 2. The method according to claim 1, wherein the first conductivity type is a p-type,
2. The semiconductor light emitting device according to claim 1, wherein the conductivity type is n-type. 3. The at least one of first and second conductivity type cladding layers sandwiching one of the two active layers and at least one of the first and second conductivity type cladding layers sandwiching the other of the two active layers. A current blocking layer for selectively passing a current to a partial region of the active layer is formed therein, and these current blocking layers are formed in a state where the ranges for selectively flowing the current match each other. 3. The semiconductor light emitting device according to claim 1, wherein: 4. The semiconductor light emitting device according to claim 1, wherein said current blocking layer is a layer in which a current blocking portion other than a range in which a current flows selectively is selectively oxidized. . 5. The semiconductor light emitting device according to claim 4, wherein said current blocking layer comprises an AlAs layer. 6. The method for manufacturing a semiconductor light emitting device according to claim 4, wherein two layers extending perpendicularly to the layer on the substrate on which each layer including the material layer serving as the current blocking layer is formed. The grooves are formed, and the material layer is heat-treated from the groove side for a predetermined time in a state where water vapor enters the two grooves, so that a predetermined distance inward from each groove in a portion between the two grooves. A method for manufacturing a semiconductor light emitting device, comprising selectively oxidizing a portion of the material layer containing the material layer. 7. The method according to claim 6, wherein an AlAs layer is used as the material layer.