JP5067813B2 - Semiconductor light emitting device, method for manufacturing the same, optical transmission module, optical switching device, and optical transmission system - Google Patents

Description

  The present invention relates to a semiconductor light emitting device, a method for manufacturing the same, an optical transmission module, an optical switching device, and an optical transmission system.

  Conventionally, when a GaInNAs active layer and a layer containing Al are grown in direct contact with each other, nitrogen is segregated at the interface, the surface morphology is deteriorated, and the emission intensity is remarkably lowered. As a method for improving this, Patent Document 1 proposes a structure in which Al is not contained in a layer in direct contact with the GaInNAs layer.

  In Patent Document 2, crystallinity and light emission efficiency are improved by providing an intermediate layer that does not contain Al and N as constituent elements between a GaInNP active layer and an AlGaInP cladding layer.

  However, even when the intermediate layer is provided, it has been reported that the luminous efficiency of the GaInNAs active layer formed on the Al-containing semiconductor layer is lowered. Non-Patent Document 1 reports that when a GaInNAs quantum well layer is continuously grown on an AlGaAs cladding layer in the same MOCVD growth chamber, the photoluminescence intensity is significantly deteriorated. In the above report, in order to improve the photoluminescence intensity, the AlGaAs cladding layer and the GaInNAs active layer are grown in different MOCVD growth chambers.

  FIG. 1 shows a room temperature photoluminescence spectrum of a GaInNAs / GaAs double quantum well structure fabricated by our MOCVD apparatus. In FIG. 1, A is a sample in which a double quantum well structure is formed by sandwiching a GaAs intermediate layer on an AlGaAs cladding layer having a thickness of 1.5 μm, and B is a GaAs layer on a GaInP cladding layer having a thickness of 1.5 μm. It is a sample in which a double quantum well structure is continuously formed across an intermediate layer.

  As shown in FIG. 1, the photoluminescence intensity of sample A is reduced to less than half that of sample B. Therefore, as in the conventional example, when an active layer containing nitrogen such as GaInNAs is continuously formed on a semiconductor layer containing Al as a constituent element using a single MOCVD apparatus, the emission intensity of the active layer There was a problem that would deteriorate. Therefore, there is a problem that the threshold current density of the GaInNAs laser formed on the AlGaAs cladding layer is twice or more higher than that formed on the GaInP cladding layer.

  The present invention relates to a semiconductor light emitting device in which a light emitting characteristic can be remarkably improved in a semiconductor light emitting device in which a semiconductor layer containing Al is provided between a semiconductor substrate and an active layer containing nitrogen. An object of the present invention is to provide an optical switching device and an optical transmission system.

In order to achieve the above object, the invention according to claim 1 is a substrate, a first semiconductor layer containing Al stacked on the substrate,
A second semiconductor layer formed on the first semiconductor layer and having a layer thickness smaller than that of the first semiconductor layer and containing Al;
An intermediate layer formed on the second semiconductor layer;
In a semiconductor light emitting device including an active layer made of a nitrogen-based group V mixed crystal semiconductor formed on the intermediate layer,
The first semiconductor layer and the second semiconductor layer are grown using an organometallic Al raw material, and the active layer is grown using a nitrogen compound raw material ,
Al source material remaining in a place where the nitrogen compound source material or impurities contained in the nitrogen compound source material are in contact with each other between the growth of the first semiconductor layer and the start of the growth of the second semiconductor layer, or Al A step of removing a reactant, an Al compound, or Al is performed, and the band gap energy of the second semiconductor layer is larger than that of the intermediate layer, and a non-radiative recombination level forming impurity in the active layer containing nitrogen It is characterized in that the concentration of is equal to or less than the concentration in the intermediate layer.

Further, in the invention of claim 2, wherein, in the semiconductor light emitting device according to claim 1, and wherein the concentration of non-radiative recombination level forming impurity in the active layer containing the nitrogen is the oxygen concentration.

According to a third aspect of the present invention, in the semiconductor light emitting device according to the first aspect, the Al concentration in the active layer containing nitrogen is not more than the Al concentration in the intermediate layer .

Further, in the invention of claim 4, wherein, in the semiconductor light emitting device according to any one of claims 1 to 3, the Al content of the second semiconductor layer including the Al includes the Al 1 It is characterized by being smaller than the Al content of the semiconductor layer.

According to a fifth aspect of the present invention, in the semiconductor light emitting device according to any one of the first to fourth aspects, the first semiconductor layer containing Al is a first Al layer laminated on a substrate. Are first semiconductor multilayer mirrors in which low refractive index layers containing Al and first high refractive index layers not containing Al are alternately laminated, and the second semiconductor layer containing Al is the first semiconductor multilayer A second semiconductor multi-layer film reflecting mirror formed on a film reflecting mirror and laminated with a low refractive index layer containing second Al and a high refractive index layer not containing second Al. It is characterized by emitting light.
According to a sixth aspect of the present invention, in the surface-emitting type semiconductor light emitting device according to the fifth aspect, the Al content of the low refractive index layer containing the second Al is a low refractive index containing the first Al. It is characterized by being smaller than the Al content of the layer.

Further, in the invention according to claim 7, the substrate, the first semiconductor layer containing Al laminated on the substrate,
A second semiconductor layer formed on the first semiconductor layer and having a layer thickness smaller than that of the first semiconductor layer and containing Al;
An intermediate layer formed on the second semiconductor layer;
In a method for manufacturing a semiconductor light emitting device including an active layer made of a nitrogen-based group V mixed crystal semiconductor formed on the intermediate layer,
The first semiconductor layer and the second semiconductor layer are grown using an organometallic Al raw material, and the active layer is grown using a nitrogen compound raw material ,
The band gap energy of the second semiconductor layer is larger than that of the intermediate layer,
Al source material remaining in a place where the nitrogen compound source material or impurities contained in the nitrogen compound source material are in contact with each other between the growth of the first semiconductor layer and the start of the growth of the second semiconductor layer, or Al It has the process of removing a reactant, an Al compound, or Al.

The invention according to claim 8 is an optical transmission module using the semiconductor light emitting element according to any one of claims 1 to 6 .

The invention according to claim 9 is an optical switching device comprising the semiconductor light emitting element according to any one of claims 1 to 6 .

The invention according to claim 10 is an optical transmission system comprising the optical transmission module according to claim 8 or the optical switching device according to claim 9 .

According to the invention of claim 1, claim 2, claim 3, claim 4, claim 5 and claim 6, a substrate, a first semiconductor layer containing Al stacked on the substrate,
A second semiconductor layer formed on the first semiconductor layer and having a layer thickness smaller than that of the first semiconductor layer and containing Al;
An intermediate layer formed on the second semiconductor layer;
In a semiconductor light emitting device including an active layer made of a nitrogen-based group V mixed crystal semiconductor formed on the intermediate layer,
The first semiconductor layer and the second semiconductor layer are grown using an organometallic Al raw material, and the active layer is grown using a nitrogen compound raw material ,
Between the growth of the first semiconductor layer and the start of the growth of the second semiconductor layer, an Al raw material remaining in a place where the nitrogen compound raw material or impurities contained in the nitrogen compound raw material are in contact in the growth chamber, or an Al reaction A band gap energy of the second semiconductor layer is larger than that of the intermediate layer, and a non-radiative recombination level forming impurity in the active layer containing nitrogen is removed. Since the concentration is the same as or lower than the concentration in the intermediate layer, even when an active layer containing nitrogen is formed on a semiconductor layer containing Al, light emission equivalent to that formed on a semiconductor layer containing no Al Characteristics are obtained.

In particular, according to the invention of claim 4, wherein, in the semiconductor light emitting device according to any one of claims 1 to 3, Al content of the second semiconductor layer including the Al includes the Al By being smaller than the Al content of the first semiconductor layer, the Al concentration and the oxygen concentration in the active layer containing nitrogen can be further reduced, and the luminous efficiency of the active layer can be improved.

Further, according to the inventions of claims 5 and 6, in the semiconductor light emitting device according to any one of claims 1 to 4 , the first semiconductor layer containing Al is stacked on the substrate. The first semiconductor multilayer mirror in which the low refractive index layer containing the first Al and the high refractive index layer not containing the first Al are alternately stacked, and the second semiconductor layer containing Al is A second semiconductor multilayer film reflector formed on the first semiconductor multilayer film reflector, in which a low refractive index layer containing second Al and a high refractive index layer not containing second Al are laminated, This is a surface-emitting semiconductor light-emitting element that emits light in a direction perpendicular to the substrate, and the light-emitting efficiency of the active layer can also be improved in the surface-type semiconductor light-emitting element.

According to the invention of claim 7, the substrate, the first semiconductor layer containing Al laminated on the substrate,
A second semiconductor layer formed on the first semiconductor layer and having a layer thickness smaller than that of the first semiconductor layer and containing Al;
An intermediate layer formed on the second semiconductor layer;
In a method for manufacturing a semiconductor light emitting device including an active layer made of a nitrogen-based group V mixed crystal semiconductor formed on the intermediate layer,
The first semiconductor layer and the second semiconductor layer are grown using an organometallic Al raw material, and the active layer is grown using a nitrogen compound raw material ,
The band gap energy of the second semiconductor layer is larger than that of the intermediate layer,
Al source material remaining in a place where the nitrogen compound source material or impurities contained in the nitrogen compound source material are in contact with each other between the growth of the first semiconductor layer and the start of the growth of the second semiconductor layer, or Al Since it has a step of removing the reactant, Al compound, or Al, the Al concentration in the active layer can be reduced. Therefore, it is possible to reduce the oxygen concentration taken into the active layer by combining with Al, and to improve the luminous efficiency of the active layer.

According to the invention described in claim 8, since the semiconductor light emitting device according to any one of claims 1 to 6 is used, the optical transmission module is characterized in that the environmental temperature changes. In contrast, an optical transmission module that operates stably and consumes low power can be provided.

According to the ninth aspect of the present invention, since the optical switching device includes the semiconductor light-emitting element according to any one of the first to sixth aspects, the environmental temperature changes. Therefore, it is possible to provide an optical switching device that operates stably with low power consumption.

According to a tenth aspect of the present invention, an optical transmission system comprising the optical transmission module according to the eighth aspect or the optical switching device according to the ninth aspect is provided. In contrast, a stable optical transmission system can be constructed, and power consumption can be reduced.

It is a figure which shows the room temperature photoluminescence spectrum of a GaInNAs / GaAs double quantum well structure. It is a figure which shows an example of the semiconductor light-emitting device with which the semiconductor layer containing Al is provided between the board | substrate and the active layer containing nitrogen. It is a figure which shows the depth direction distribution of nitrogen concentration and oxygen concentration of a semiconductor light-emitting device. It is a figure which shows the depth direction distribution of Al concentration of a semiconductor light-emitting device. It is a figure which shows the structural example of the semiconductor light-emitting device by the 1st Embodiment of this invention. It is a figure which shows the room temperature photoluminescence spectrum of a GaInNAs / GaAs double quantum well structure. It is a figure which shows the structural example of the semiconductor light-emitting device by the 8th Embodiment of this invention. It is a figure which shows the structural example of the semiconductor light-emitting device by the 9th Embodiment of this invention. 1 is a diagram showing a ridge stripe semiconductor laser according to Example 1. FIG. 6 is a diagram showing a ridge stripe semiconductor laser according to Example 2. FIG. 6 is a diagram showing a ridge stripe semiconductor laser according to Example 3. FIG. 6 is a view showing a surface emitting semiconductor laser according to Example 4. FIG. It is a figure explaining the interruption | blocking interface of Example 4. FIG. It is a figure which shows the depth direction distribution of nitrogen concentration and oxygen concentration of the semiconductor light-emitting device provided with the growth interruption. FIG. 10 is a diagram illustrating an optical transceiver module according to a fifth embodiment. FIG. 10 illustrates an optical transmission module according to a sixth embodiment. FIG. 10 is a diagram illustrating an optical switching device according to a seventh embodiment. FIG. 10 illustrates an optical transmission system according to an eighth embodiment. FIG. 10 illustrates an optical transmission system according to a ninth embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 2 is a diagram illustrating an example of a semiconductor light emitting element in which a semiconductor layer containing Al is provided between a substrate and a semiconductor layer containing nitrogen. In the semiconductor light emitting device of FIG. 2, a first semiconductor layer 202 containing Al, an intermediate layer 203, an active layer 204 containing nitrogen, an intermediate layer 203, and a second semiconductor layer 205 are sequentially stacked on a substrate 201. .

  Here, as the substrate 201, for example, a compound semiconductor substrate such as GaAs, InP, or GaP is used.

  As a material of the first semiconductor layer 202 containing Al as a constituent element, AlAs, AlP, AlGaAs, AlInP, AlGaInP, AlInAs, AlInAsP, AlGaInAsP, or the like can be used. Note that the first semiconductor layer 202 is not limited to a single layer, and a plurality of semiconductor layers containing Al as a constituent element may be stacked.

  The intermediate layer 203 does not contain Al and N as constituent elements, and is made of, for example, GaAs, GaP, InP, GaInP, GaInAs, GaInAsP, or the like.

  As the active layer 204 containing nitrogen, for example, GaNAs, GaPN, GaInNAs, GaInNP, GaNASSb, GaInNAsSb, or the like is used. The active layer 204 containing nitrogen is crystal-grown without intentionally introducing an Al material. The active layer 204 can be formed not only in a single layer but also in a multiple quantum well structure in which a semiconductor containing nitrogen is used as a well layer and an intermediate layer material is used as a barrier layer.

  The energy band gap of each layer of the semiconductor light emitting device of FIG. 2 increases in the order of the active layer 204, the intermediate layer 203, the first semiconductor layer 202, and the second semiconductor layer 205. Note that the second semiconductor layer 205 is generally formed using the same material as the first semiconductor layer 202; however, the second semiconductor layer 205 is not necessarily formed using the same material, and may be formed using a material that does not contain Al. It is.

The semiconductor light emitting device of FIG. 2 can perform crystal growth using an epitaxial growth apparatus using an organometallic Al raw material and a nitrogen compound raw material. Here, as the organometallic Al raw material, for example, TMA and TEA can be used. Further, as the nitrogen compound raw material, organic nitrogen raw materials such as DMHy and MMHy and NH ₃ can be used. As a crystal growth method, MOCVD method or CBE method can be used.

  FIG. 3 shows an example of the semiconductor light emitting device shown in FIG. 2, in which 202 and 205 are made of AlGaAs, 203 is made of GaAs, and 204 is made of a GaInNAs / GaAs double quantum well structure. It is a figure which shows the depth direction distribution of nitrogen and oxygen concentration when forming using this. This measurement was performed by SIMS. Table 1 shows the measurement conditions.

  In FIG. 3, two nitrogen peaks are seen in the active layer 204 corresponding to the GaInNAs / GaAs double quantum well structure. In the active layer 204, an oxygen peak is detected. However, the oxygen concentration in the intermediate layer 203 not containing N and Al is about one digit lower than the oxygen concentration in the active layer 204.

  On the other hand, when the depth direction distribution of oxygen concentration is measured for an element in which 202 and 205 are GaInP, 203 is GaAs, and 204 is a GaInNAs / GaAs double quantum well structure, the oxygen concentration in the active layer 204 is measured. Was at the background level.

  FIG. 4 shows an example of the semiconductor light emitting device shown in FIG. 2, in which 202 and 205 are made of AlGaAs, 203 is made of GaAs, and 204 is made of a GaInNAs / GaAs double quantum well structure. It is the figure which showed the depth direction distribution of Al concentration when formed using this. The measurement was performed by SIMS. Table 2 shows the measurement conditions.

  From FIG. 4, Al is detected in the active layer 204 which is not originally introduced with the Al raw material. However, in the intermediate layer 203 adjacent to the semiconductor layers 202 and 205 containing Al, the Al concentration is about one digit lower than that of the active layer 204. This indicates that Al in the active layer 204 is not mixed by diffusion and replacement from the semiconductor layers 202 and 205 containing Al.

  On the other hand, when an active layer containing nitrogen was grown on a semiconductor layer not containing Al, such as GaInP, Al was not detected in the active layer.

  Compared to the depth distribution of nitrogen and oxygen concentrations in the same element shown in FIG. 3, the two oxygen peak profiles in the double quantum well active layer do not correspond to the peak profiles of nitrogen concentration, 4 corresponds to the Al concentration profile. From this, it was clarified that oxygen impurities in the GaInNAs well layer were incorporated together with Al incorporated in the well layer rather than being incorporated with the nitrogen source. .

  Accordingly, Al detected in the active layer 204 is bonded to impurities (such as moisture) in the Al source material, Al reactant, Al compound, or Al remaining in the growth chamber. Then, it is incorporated in the active layer. That is, when using a nitrogen compound raw material and an organometallic Al raw material, a single crystal growth apparatus continuously crystal-grows a semiconductor light emitting device in which an Al-containing semiconductor layer is provided between a substrate and an active layer containing nitrogen. Then, Al is naturally taken up in the active layer containing nitrogen.

  Then, the Al raw material, Al reaction product, Al compound, or Al remaining in the growth chamber is combined with moisture contained in the nitrogen compound raw material, oxygen or moisture remaining in the pipe or reaction tube, and the active layer. Since it is taken in, oxygen is taken into the active layer at the same time. It has been newly found out by the inventors of the present application that oxygen taken into the active layer forms a non-radiative recombination level, thus reducing the luminous efficiency of the active layer.

  This invention is made | formed based on said knowledge by this inventor.

(1) First Embodiment FIG. 5 is a diagram showing a configuration example of a semiconductor light emitting device according to a first embodiment of the present invention. 5 includes a first semiconductor layer 501 containing Al as a constituent element, a second semiconductor layer 502 containing Al as a constituent element, a lower intermediate layer 203, and an active layer 204 containing nitrogen on a substrate 201. The upper intermediate layer 203 and the third semiconductor layer 503 are sequentially stacked.

  As a method for manufacturing the semiconductor light emitting device of FIG. 5, epitaxial growth can be performed using an organometallic Al raw material and an organic nitrogen raw material. Then, after the growth of the first semiconductor layer 501 containing Al as a constituent element and between the start of growth of the second semiconductor layer 502 containing Al as a constituent element, it is contained in the nitrogen compound raw material or the nitrogen compound raw material in the growth chamber A step of removing the Al raw material, the Al reactant, the Al compound, or the Al remaining at the place where the impurities to be touched is provided.

  By providing the above steps, the growth of the first semiconductor layer 501 containing Al as a constituent element causes the Al source material remaining in the growth chamber to be exposed to the nitrogen compound source material or the impurities contained in the nitrogen compound source material, or the Al reaction. Or Al compounds or Al can be removed.

  FIG. 6 is a diagram showing a room temperature photoluminescence spectrum of a GaInNAs / GaAs double quantum well structure. In FIG. 6, B is a case where a GaInNAs / GaAs double quantum well structure is formed on a GaInP layer, A is a case where it is formed on an AlGaAs layer having a layer thickness of 1.5 μm, and C is a layer thickness of 0 When formed on a 2 μm AlGaAs layer.

  As shown in FIG. 6, when the thickness of the AlGaAs layer below the active layer containing nitrogen is made thinner than 1.5 μm generally used for a cladding layer of a semiconductor light emitting device, for example, 0.2 μm, AlGaAs Even when formed on the layer, the same photoluminescence intensity as when formed on the GaInP layer was obtained. This is because by reducing the thickness of the semiconductor layer containing Al located below the active layer containing nitrogen, the Al source material remaining in the growth chamber where the nitrogen compound source material or impurities contained in the nitrogen compound source come into contact This is because the concentration of the Al reactant, Al compound, or Al can be reduced.

  In the semiconductor light emitting device according to the first embodiment, after the growth of the first semiconductor layer 501 containing Al as a constituent element, the Al remaining in the place where the nitrogen compound raw material in the growth chamber or the impurities contained in the nitrogen compound raw material come into contact. A step of removing a raw material, an Al reactant, an Al compound, or Al is provided, and then a second semiconductor layer 502 containing Al is provided which is thinner than the first semiconductor layer 501 containing Al. Then, an active layer 204 containing nitrogen is formed.

  Therefore, the remaining Al raw material, Al reactant, Al compound, or Al is removed once by the growth of the first semiconductor layer 501 containing thick Al. Then, the concentration of the remaining Al raw material, Al reactant, Al compound, or Al is reduced by forming the second semiconductor layer 502 containing Al as thin as 0.2 μm, for example, and nitrogen The concentration of the non-radiative recombination level forming impurity in the active layer 204 containing is reduced. Accordingly, the semiconductor light emitting device of FIG. 2 in which an active layer containing nitrogen is stacked on a semiconductor layer containing Al can be continuously oscillated at room temperature.

  FIG. 14 shows the removal of the Al raw material, Al reactant, Al compound, or Al remaining in the middle of the lower intermediate layer 203 where the nitrogen compound raw material or impurities contained in the nitrogen compound raw material in the growth chamber come into contact. It is a figure which shows the depth direction distribution of nitrogen concentration and oxygen concentration of the semiconductor light-emitting device which provided the process. The measurement was performed by SIMS.

  As a step of removing Al, a step of temporarily moving the substrate from the reaction chamber to the sample exchange chamber and evacuating the substrate and purging the reaction chamber with a carrier gas was provided for 1 hour.

  As shown in FIG. 14, the concentration of oxygen forming the non-radiative recombination level is lower than the background in the active layer 204 containing nitrogen. This is because a step of removing Al is provided in the middle of the lower intermediate layer 203.

  However, when the growth was interrupted in order to provide an Al removal step in the lower intermediate layer 203, an oxygen peak was detected at the interface, and it was found that oxygen was segregated. Further, although not shown in FIG. 14, peaks of C and Si in addition to oxygen are also detected.

As in the semiconductor light-emitting element in FIG. 5 , an impurity contained in the nitrogen compound raw material or the nitrogen compound raw material in the growth chamber is between the first semiconductor layer 501 containing Al and the second semiconductor layer 502 containing Al. In the case where a step of removing the Al raw material, the Al reactant, the Al compound, or Al remaining at the touched location is provided, impurities such as oxygen, C, and Si may segregate at the interface.

Impurities such as oxygen, C, and Si segregated at the interface form a non-radiative recombination level. However, in the semiconductor light emitting device of FIG. 5 , the second semiconductor layer 502 containing Al is provided between the interface where the growth is interrupted to provide a step of removing residual Al and the active layer 204 containing nitrogen. ing. Since the band gap energy of the second semiconductor layer 502 containing Al is larger than that of the intermediate layer 203, the carrier overflowing from the active layer 204 containing nitrogen to the intermediate layer 203 has a second band containing Al having a large band gap. Blocked by the semiconductor layer 502. Therefore, as compared with the case where an interface where growth is interrupted is provided in the intermediate layer 203, the rate at which overflowed carriers are recombined and lost at the non-radiative recombination level of the interface where growth is interrupted is reduced. Therefore, a leak current can be suppressed and a highly efficient semiconductor light emitting device can be formed.

(2) Second Embodiment In the second embodiment of the present invention, in the semiconductor light emitting device described in the first embodiment, the non-light emitting recombination level forming impurity concentration of the active layer containing nitrogen is the intermediate layer. It is characterized by being equal to or less than the concentration of.

  Here, the intermediate layer is made of a material that does not contain Al and N as constituent elements, so that the semiconductor layer containing Al and the active layer containing nitrogen are not in direct contact with each other. This suppresses abnormal segregation of nitrogen on the surface because Al, which has a strong chemical bond with nitrogen, is not exposed on the surface when a nitrogen source is supplied to the growth chamber to grow an active layer containing nitrogen. is doing.

  When an active layer not containing nitrogen, for example, a GaAs or GaInAs active layer is formed on a semiconductor layer containing Al by the MOCVD method, the deterioration of the light emission characteristics of the active layer has not been reported, which is a problem. Absent. Therefore, if the non-light emitting recombination level forming impurity concentration of the active layer containing nitrogen is reduced to the same level as the intermediate layer containing no nitrogen, a high quality active layer without deterioration can be obtained. Therefore, even when an active layer containing nitrogen is formed on a semiconductor layer containing Al as a constituent element, light emission characteristics equivalent to those formed on a semiconductor layer containing no Al can be obtained.

(3) Third Embodiment In the third embodiment of the present invention, in the semiconductor light emitting device described in the first embodiment, particularly in the active layer containing nitrogen, the oxygen concentration is a concentration that enables continuous oscillation at room temperature. It is characterized by being.

  Table 3 shows the results of evaluating the threshold current density by fabricating a broad stripe laser using AlGaAs as a cladding layer (a layer containing Al) and using a GaInNAs double quantum well structure (a layer containing nitrogen) as an active layer. Yes.

From Table 3, in the structure in which the active layer containing nitrogen is continuously formed in the semiconductor layer containing Al as a constituent element, oxygen of 1 × 10 ¹⁸ cm ⁻³ or more is incorporated in the active layer, The threshold current density was as high as 10 kA / cm ² or higher. However, by reducing the oxygen concentration in the active layer to 1 × 10 ¹⁸ cm ⁻³ or less, a broad stripe laser oscillated at a threshold current density of ² to 3 kA / cm ² . If the threshold current density of the broad stripe laser is an active layer quality of several kA / cm ² or less, continuous oscillation at room temperature is possible. Therefore, it is possible to manufacture a semiconductor laser capable of continuous oscillation at room temperature by suppressing the oxygen concentration in the active layer containing nitrogen to 1 × 10 ¹⁸ cm ⁻³ or less.

In the third embodiment of the present invention, after the growth of the first semiconductor layer containing Al, the Al raw material remaining in a place where the nitrogen compound raw material in the growth chamber or the impurity contained in the nitrogen compound raw material comes into contact, or the Al reaction The oxygen concentration of the active layer containing nitrogen is reduced to, for example, 1 × 10 ¹⁸ cm ⁻³ or less by performing a step of removing the oxide, the Al compound, or Al and then providing a thin second semiconductor layer containing Al. is doing. As a result, the non-light emitting recombination level of the active layer is reduced to improve the light emission efficiency, and it becomes possible to form a semiconductor light emitting device that continuously oscillates at room temperature.

(4) Fourth Embodiment From the measurement result of the depth distribution of oxygen concentration shown in FIG. 3, the oxygen concentration in the intermediate layer 203 is 2 × 10 ^{17 to} 7 × 10 ¹⁶ cm ⁻³ . Therefore, a high-quality active layer can be obtained by reducing the oxygen concentration of the active layer containing nitrogen to at least 2 × 10 ¹⁷ cm ⁻³ or less.

Further, as shown in Table 3, when the oxygen concentration in the active layer is reduced to 2 × 10 ¹⁷ cm ⁻³ or less, in the broad stripe laser, even when the AlGaAs cladding layer is used, the GaInP cladding layer is used. An equivalent threshold current density of 0.8 kA / cm ² was obtained.

Therefore, in the fourth embodiment of the present invention, in the semiconductor light emitting device of the second embodiment, the oxygen concentration of the active layer containing nitrogen is set to 2 × 10 ¹⁷ cm ⁻³ or less, for example, and the active layer containing nitrogen is used. Even when an active layer containing nitrogen is formed on a semiconductor layer containing Al as a constituent element by making the oxygen concentration of the same as or lower than the oxygen concentration of the intermediate layer on the semiconductor layer not containing Al Emission characteristics equivalent to those obtained when formed are obtained.

(5) Fifth Embodiment Table 4 shows a threshold current obtained by fabricating a broad stripe laser using AlGaAs as a cladding layer (a layer containing Al) and a GaInNAs double quantum well structure (a layer containing nitrogen) as an active layer. The result of evaluating the density is shown.

In a structure in which an active layer containing nitrogen is continuously formed in a semiconductor layer containing Al as a constituent element, Al of 2 × 10 ¹⁹ cm ⁻³ or more is incorporated in the active layer, and the threshold current density is The value was as extremely high as 10 kA / cm ² or more. However, by reducing the Al concentration in the active layer to 1 × 10 ¹⁹ cm ⁻³ or less, the oxygen concentration in the active layer is reduced to 1 × 10 ¹⁸ cm ⁻³ or less, and the threshold current density is 2 to ³ kA / cm. ^{At 2} the broad stripe laser oscillated. If the threshold current density of the broad stripe laser is an active layer quality of several kA / cm ² or less, continuous oscillation at room temperature is possible. Therefore, it is possible to manufacture a semiconductor laser capable of continuous oscillation at room temperature by suppressing the Al concentration in the active layer containing nitrogen to 1 × 10 ¹⁹ cm ⁻³ or less.

In the fifth embodiment of the present invention, a substrate, a first semiconductor layer containing Al stacked on the substrate, and an active layer containing nitrogen formed on the first semiconductor layer containing Al are provided. In the semiconductor light emitting device including the Al source remaining in a place where the nitrogen compound source in the growth chamber or the impurity contained in the nitrogen compound source contacts the first semiconductor layer including Al and the active layer including nitrogen, or After performing the step of removing the Al reactant, the Al compound, or Al, a second semiconductor layer containing Al that is thinner than the first semiconductor layer containing Al is provided and contains nitrogen The light emission efficiency of the active layer was improved by setting the Al concentration of the active layer to 1 × 10 ¹⁹ cm ⁻³ or less, for example. Accordingly, it is possible to form a semiconductor light emitting element that continuously oscillates at room temperature.

(6) Sixth Embodiment In the sixth embodiment of the present invention, in the semiconductor light emitting device of the fifth embodiment, the Al concentration of the active layer containing nitrogen is the same as or higher than the Al concentration of the intermediate layer. It is characterized by the following.

From FIG. 4, the Al concentration in the intermediate layer 203 grown without supplying the nitrogen compound raw material and the organometallic Al raw material to the reaction chamber is 2 × 10 ¹⁸ cm ⁻³ or less. When the Al concentration incorporated in the active layer is 2 × 10 ¹⁸ cm ⁻³ or less, the oxygen impurity concentration in the active layer can be reduced to 2 × 10 ¹⁷ cm ⁻³ or less.

Further, as shown in Table 4, when the Al concentration in the active layer is reduced to 1 × 10 ¹⁸ cm ⁻³ or less, in the broad stripe laser, even when the AlGaAs cladding layer is used, the GaInP cladding layer is used. An equivalent threshold current density of 0.8 kA / cm ² was obtained.

Accordingly, whether the Al concentration of the active layer containing nitrogen is 2 × 10 ¹⁸ cm ⁻³ or less, preferably 1 × 10 ¹⁸ cm ⁻³ or less, and the Al concentration of the active layer containing nitrogen is the same as the Al concentration of the intermediate layer When the active layer containing nitrogen is formed on the semiconductor layer containing Al as a constituent element, the light emission characteristics equivalent to those formed on the semiconductor layer containing no Al can be obtained.

(7) Seventh Embodiment In the seventh embodiment of the present invention, in the semiconductor light emitting devices of the first to sixth embodiments, the Al content of the second semiconductor layer containing Al contains Al. It is characterized by being smaller than the Al content of one semiconductor layer.

  In addition to making the thickness of the second semiconductor layer containing Al thinner than the thickness of the first semiconductor layer containing Al, the Al content of the second semiconductor layer containing Al is made to contain Al. By making it smaller than the Al content of the first semiconductor layer, the Al source material, the Al reactant, the Al compound, or the Al compound remaining in the place where the impurities contained in the nitrogen compound source material or the nitrogen compound source material in the growth chamber come into contact, or The concentration of Al can be further reduced. Thereby, the luminous efficiency of the active layer can be improved and a semiconductor light emitting element with a low threshold current can be realized.

(8) Eighth Embodiment FIG. 7 is a diagram showing a configuration example of a semiconductor light emitting device according to an eighth embodiment of the present invention. 7 includes a first semiconductor layer 501, an intermediate layer 701 containing Al as a constituent element, a second semiconductor layer 502 containing Al as a constituent element, a lower intermediate layer 203, and nitrogen on a substrate 201. The active layer 204 including the upper intermediate layer 203 and the third semiconductor layer 503 are sequentially stacked.

  As a method for manufacturing the semiconductor light emitting device of FIG. 7, epitaxial growth can be performed using an organometallic Al raw material and an organic nitrogen raw material. An intermediate layer 701 is provided between the first semiconductor layer 501 containing Al and the second semiconductor layer 502 containing Al. In the middle of the intermediate layer, a nitrogen compound raw material or a nitrogen compound raw material in the growth chamber is provided. A step of removing the Al raw material, the Al reactant, the Al compound, or Al remaining at the place where the impurities contained in the substrate come into contact is provided.

  By providing the above steps, the growth of the first semiconductor layer 501 containing Al as a constituent element causes the Al source material remaining in the growth chamber to be exposed to the nitrogen compound source material or the impurities contained in the nitrogen compound source material, or the Al reaction. Or Al compounds or Al can be removed.

  The intermediate layer 701 is made of a semiconductor material that does not contain Al, such as GaAs. By providing an Al removal step by interrupting the growth in the intermediate layer 701, impurities such as O are segregated during the growth interruption compared to the case where the Al removal step is provided immediately after the growth of the first semiconductor layer 501 containing Al. Thus, formation of a non-radiative recombination level at the growth interface can be suppressed. Therefore, the non-radiative recombination level at the growth interface can be reduced and the luminous efficiency of the active layer can be improved.

(9) Ninth Embodiment FIG. 8 is a diagram showing a configuration example of a surface-emitting type semiconductor light emitting device according to a ninth embodiment of the present invention. The semiconductor light emitting device of FIG. 8 includes a first lower semiconductor multilayer reflector 801, a second lower semiconductor multilayer reflector 802, a lower spacer layer 803, an intermediate layer 203, and nitrogen on a semiconductor single crystal substrate 201. An active layer 204, an intermediate layer 203, an upper spacer layer 804, and an upper multilayer reflector 805 are sequentially stacked. Light is structured to be extracted in the vertical direction (upward) with respect to the substrate 201.

Here, as the semiconductor single crystal substrate 201, for example, a GaAs substrate is used. In the first lower multilayer reflector 801 and the second lower multilayer reflector 802, a high refractive index semiconductor layer and a low refractive index semiconductor layer are alternately laminated at a quarter optical wavelength thickness of the oscillation wavelength. It is a distributed Bragg reflector. The combination of high and low refractive index layers, for example, _{GaAs / Al x Ga 1-x} As (0 <x ≦ 1), Al x Ga 1-x As / Al y Ga 1-y As (0 < x <y ≦ 1), GaInP / (Al _x Ga _1-x ) InP (0 <x ≦ 1), or the like is used.

  The region of the lower spacer layer 803 to the upper spacer layer 804 sandwiched between the reflecting mirrors constitutes a resonator, which is an integral multiple of 1/2 optical wavelength thickness of the oscillation wavelength.

  The intermediate layer 203 is made of a material that does not contain Al and N as constituent elements, and is made of, for example, GaAs, GaInP, GaInAsP, or the like.

  The active layer 204 containing nitrogen is made of, for example, GaNAs, GaInNAs, GaNAsSb, GaInNAsSb, or the like. Such a nitrogen-based group V mixed crystal semiconductor material has a band gap wavelength of 1.2 to 1.6 μm and can be epitaxially grown on a GaAs substrate. In addition, the active layer 204 can be formed not only in a single layer but also in a multiple quantum well structure in which a semiconductor containing nitrogen is a well layer.

The upper multilayer mirror 805 is a distributed Bragg reflector similar to the lower semiconductor multilayer mirror 801. The material can be composed of a semiconductor crystal such as the lower reflecting mirrors 801 and 802, or a dielectric material such as SiO ₂ / TiO ₂ .

  By using a semiconductor layer containing Al as a constituent element as the low refractive index layer of the lower semiconductor multilayer mirrors 801 and 802, the refractive index difference from the high refractive index layer can be increased. Thereby, a high reflectance of 99% or more can be obtained with a smaller number of layers. When the number of layers is reduced, there is an advantage that the electrical resistance and thermal resistance of the semiconductor multilayer mirror can be reduced, and the temperature characteristics are improved.

  In the case of an edge emitting semiconductor laser, the cladding layer can be made of a material that does not contain Al, such as GaInP, InP, and GaInAsP. However, in the case of a surface emitting semiconductor laser, in order to improve the operating temperature up to 70 ° C. or higher, Al is contained in the low refractive index layers of the lower semiconductor multilayer reflectors 801 and 802 as in the AlGaAs material system. A semiconductor layer must be used.

  As described above, in the surface emitting semiconductor laser in which the active layer 204 containing nitrogen needs to be formed on the lower semiconductor multilayer mirror 801 containing Al, the reduction in the luminous efficiency of the active layer 204 containing nitrogen becomes a big problem. . In particular, since the lower reflector is laminated for 30 cycles or more in order to obtain a high reflectance, the layer thickness must be as thick as 5 μm or more. Therefore, the concentration of the Al raw material, the Al reactant, the Al compound, or Al remaining in the place where the nitrogen compound raw material or impurities contained in the nitrogen compound raw material come into contact with the growth chamber increases.

  According to the present invention, after the growth of the first lower semiconductor multilayer mirror 801 containing Al, the Al raw material remaining in a place where the nitrogen compound raw material in the growth chamber or the impurities contained in the nitrogen compound raw material come into contact, or the Al reaction The process which removes a thing, an Al compound, or Al is performed. As a result, the Al raw material, Al reactant, Al compound, or Al remaining in the growth chamber by the growth of the first lower semiconductor multilayer reflector 801 is removed once.

  Thereafter, the second lower semiconductor multilayer reflector 802 containing Al is grown. By forming the layer thickness thin, the Al concentration remaining in the growth chamber is reduced, and the active layer 204 containing nitrogen is grown. The luminous efficiency is improved.

  Since the layer thickness of the second semiconductor multilayer film reflecting mirror 802 containing Al is preferably made thin in order to reduce the residual Al concentration, it can be configured with a period of one cycle or less.

In addition, the step of removing the Al raw material, the Al reactant, the Al compound, or Al remaining in the place where the impurities contained in the nitrogen compound raw material or the nitrogen compound raw material in the growth chamber are in contact is the same as that of the semiconductor multilayer reflector. It is desirable to discontinue growth in the refractive index layer. Since the high refractive index layer is made of a material having a very small Al composition such as GaAs or Al _0.1 Ga _0.9 As, impurities such as O are segregated during the growth interruption, and the growth interface is not The formation of a luminescent recombination level can be suppressed.

  The layer thickness of the high refractive index layer provided in the middle of the step of removing Al does not necessarily need to be 1/4 optical wavelength thickness of the oscillation wavelength, and 1 / of the oscillation wavelength so as to satisfy the phase matching condition of light. It may be n times (n = 1, 3, 5,...) 4 optical wavelength thicknesses.

(10) Tenth Embodiment A tenth embodiment of the present invention shows a method for manufacturing the semiconductor light emitting device shown in the first to ninth embodiments. In the tenth embodiment, after the growth of the first semiconductor layer containing Al and the start of the growth of the second semiconductor layer containing Al, or in the first semiconductor layer containing Al and the first semiconductor layer containing Al. During the growth of the intermediate layer provided between the two semiconductor layers, the Al raw material remaining in the nitrogen compound raw material or the impurity contained in the nitrogen compound raw material in the growth chamber, or the Al reactant, or the Al compound, Alternatively, a process for removing Al is provided.

  More specifically, in order to remove the Al raw material, the Al reactant, the Al compound, or Al remaining in a place where the nitrogen compound raw material or impurities contained in the nitrogen compound raw material come into contact in the growth chamber, for example, a carrier gas The process of purging is provided.

  Here, the time for the purge step is that after the growth of the first semiconductor layer containing Al is completed and the supply of the Al raw material to the growth chamber is stopped, the growth of the second semiconductor layer containing Al is started. Therefore, the interval until the Al raw material is supplied to the growth chamber.

  When a semiconductor layer containing Al as a constituent element is grown, an Al raw material, an Al reactant, an Al compound, or Al remains in the growth chamber. However, it is possible to gradually reduce the concentration of Al remaining in the growth chamber by purging the growth chamber with the carrier gas. Thereby, even when an active layer containing nitrogen is formed on a semiconductor layer containing Al as a constituent element, the concentration of Al and oxygen incorporated in the active layer can be reduced, and the luminous efficiency of the active layer can be improved. .

  The step of removing the residual Al can be performed not only once but also a plurality of times during the growth of the semiconductor layer containing Al below the active layer containing nitrogen. By removing the Al concentration remaining in the reaction chamber without increasing due to the growth of the semiconductor layer containing Al, the time required for the removal step such as carrier gas purging can be shortened.

(11) Eleventh Embodiment An eleventh embodiment of the present invention is characterized in that the semiconductor light emitting element shown in any one of the first to ninth embodiments is used in an optical transmission module. The optical transmission module includes a light source that generates an optical signal in accordance with an input signal. In the eleventh embodiment, the semiconductor light emitting element shown in any one of the first to ninth embodiments is used as the light source. It is done. An optical signal emitted from the light source is coupled to an optical fiber and transmitted to the outside.

  A light-receiving element for monitoring that monitors the light intensity output from the semiconductor light-emitting element can be integrated into the semiconductor light-emitting element that serves as the light source. Further, a multi-channel optical transmission module can be configured by an array light source including a plurality of semiconductor light emitting elements. In addition to a light source, an optical branching unit and a light receiving element can be integrated in order to transmit an optical signal bidirectionally using a single optical fiber. Further, a light source driving circuit and an electronic circuit for performing signal processing can be integrated together with the above-described optical components.

  Furthermore, when the surface-emitting type semiconductor light emitting device shown in the ninth embodiment is used, a light source can be used in a two-dimensional array in addition to the one-dimensional array.

  In the optical transmission module of the eleventh embodiment, for example, GaNAs, GaInNAs, GaNAsSb, GaInNAsSb or the like is used as the material of the active layer in the semiconductor light emitting element as the light source. Such a nitrogen-based group V mixed crystal semiconductor material has a band gap wavelength of 1.2 to 1.6 μm and can be epitaxially grown on a GaAs substrate. Therefore, it is compatible with the low-loss band of silica-based optical fibers and enables long-distance and large-capacity transmission. In addition, nitrogen-based group V mixed crystal semiconductors such as GaNAs, GaInNAs, GaNASSb, GaInNAsSb, and the like can have a large conduction band discontinuity with the GaAs barrier layer, so that a semiconductor laser having a high characteristic temperature can be realized. . Therefore, it is possible to form an optical transmission module that operates stably with respect to changes in environmental temperature.

  Further, an Al raw material remaining in a place where the impurity contained in the nitrogen compound raw material or the nitrogen compound raw material in the growth chamber is in contact between the first semiconductor layer containing Al and the active layer containing nitrogen, or an Al reactant, Alternatively, after performing the step of removing Al compound or Al, the second semiconductor layer containing Al which is thinner than the first semiconductor layer containing Al is provided, thereby increasing the threshold current of the semiconductor light emitting element. Thus, the power consumption of the optical transmission module can be reduced.

(12) Twelfth Embodiment A twelfth embodiment of the present invention is characterized in that the semiconductor light emitting element shown in any one of the first to ninth embodiments is used in an optical switching device. The optical switching apparatus is an apparatus that outputs an optical signal by arbitrarily connecting optical signals input from N optical fibers to M optical fibers. Here, N and M are natural numbers of 1 or more.

  Optical switching devices are used as transceivers, hubs, repeaters, bridges, routers, gateways, etc., depending on the form and function of the connection.

  The optical signal input to the optical switching device is converted into an electrical signal by the light receiving element, and the line is electrically switched. Then, it is converted again from an electrical signal to an optical signal and output by the semiconductor light emitting element. The semiconductor light emitting element shown in any one of the first to ninth embodiments is used for this semiconductor light emitting element.

  In the semiconductor light emitting device used in the optical exchange device according to the twelfth embodiment, for example, GaNAs, GaInNAs, GaNAsSb, GaInNAsSb or the like is used as the material of the active layer. Such a nitrogen-based group V mixed crystal semiconductor material has a band gap wavelength of 1.2 to 1.6 μm and can be epitaxially grown on a GaAs substrate. Therefore, it is compatible with the low-loss band of silica-based optical fibers and enables long-distance and large-capacity transmission. In addition, nitrogen-based group V mixed crystal semiconductors such as GaNAs, GaInNAs, GaNASSb, GaInNAsSb, and the like can have a large conduction band discontinuity with the GaAs barrier layer, so that a semiconductor laser having a high characteristic temperature can be realized. . Therefore, it is possible to form an optical switching device that operates stably against changes in environmental temperature.

  Further, an Al raw material remaining in a place where the impurity contained in the nitrogen compound raw material or the nitrogen compound raw material in the growth chamber is in contact between the first semiconductor layer containing Al and the active layer containing nitrogen, or an Al reactant, Alternatively, after performing the step of removing Al compound or Al, the second semiconductor layer containing Al which is thinner than the first semiconductor layer containing Al is provided, thereby increasing the threshold current of the semiconductor light emitting element. This can reduce the power consumption of the optical switching device. In particular, when a surface emitting semiconductor element is used, the effect of reducing power consumption and cost is great.

(13) Thirteenth Embodiment A thirteenth embodiment of the present invention comprises an optical transmission module described in the eleventh embodiment or an optical switching apparatus described in the twelfth embodiment in an optical transmission system. It is characterized by being. The optical transmission system includes an optical transmission module, an optical fiber cable, and an optical reception module. The optical signal output from the optical transmission module propagates through the optical fiber cable and is transmitted to the optical reception module.

  As a form of optical transmission, there are a system for bidirectional transmission in one optical fiber and a system for transmitting in the upstream and downstream directions with two optical fibers as one set. In addition, a system that transmits optical signals in parallel using a plurality of optical fiber cables, a wavelength division multiplexing system that transmits optical signals of a plurality of wavelengths in one optical fiber, and the like can also be used. It is also possible to provide an optical switching device between the optical transmission module and the optical reception module.

  In the thirteenth embodiment, by using the optical transmission module of the eleventh embodiment or the optical switching device of the twelfth embodiment, which is stable against changes in the environmental temperature and has low power consumption, the change in the environmental temperature can be achieved. In contrast, a stable optical transmission system can be constructed, and power consumption can be reduced.

  Examples of the present invention will be described below.

Example 1
FIG. 9 is a diagram showing a semiconductor laser according to Example 1 of the present invention. 9 includes an n-type GaAs buffer layer 902, a first n-type Al _0.4 Ga _0.6 As cladding layer 903 having a layer thickness of 1.5 μm, a layer thickness of 0. 2 μm second n-type Al _0.4 Ga _0.6 As cladding layer 904, GaAs lower optical waveguide layer 905, GaInNAs / GaAs multiple quantum well active layer 906, GaAs upper optical waveguide layer 907, p-type Al _0.4 A Ga _0.6 As cladding layer 908 and a p-type GaAs contact layer 909 are sequentially stacked.

Then, etching is performed in a stripe shape from the surface of the p-type GaAs contact layer 909 to the middle of the p-type Al _0.4 Ga _0.6 As clad layer 908 to form a ridge stripe structure. The ridge stripe width is 4 μm.

  A p-side electrode 910 is formed on the p-type GaAs contact layer 909, and an n-side electrode 911 is formed on the back surface of the n-type GaAs substrate 901.

  The structure shown in FIG. 9 is a ridge stripe semiconductor laser that confines current and light in a ridge stripe structure.

The crystal growth of the semiconductor laser of FIG. 9 was performed using one MOCVD apparatus. Here, TMG, TMA, and TMI were used as Group III materials, and AsH ₃ and DMHy were used as Group V materials. The feature of Example 1 is that the growth of the first n-type Al _0.4 Ga _0.6 As cladding layer 903 and the growth start of the second n-type Al _0.4 Ga _0.6 As cladding layer 904 are performed. The crystal growth is performed by providing a growth interruption step between the two.

  In this example, as a growth interruption process, carrier gas was purged by flowing into the growth chamber. By purging the growth chamber with carrier gas, the Al raw material, Al reactant, Al compound, or Al remaining in the growth chamber due to the growth of the n-type AlGaAs cladding layer 903 can be discharged to reduce the concentration.

Then, by forming the second n-type Al _0.4 Ga _0.6 As cladding layer 904, which is grown after the growth interruption purge, as thin as 0.2 μm, the Al and Ga trapped in the GaInNAs well layer A decrease in luminous efficiency can be suppressed by sufficiently reducing the oxygen concentration. As a result, a low threshold current GaInNAs material semiconductor laser including an AlGaAs cladding layer can be formed.

Example 2
FIG. 10 is a diagram showing a semiconductor laser according to Example 2 of the present invention. In FIG. 10, the same reference numerals are given to the same portions as those in FIG. 9. The structure of the semiconductor laser in FIG. 10 is similar to the structure of the semiconductor laser in FIG. The difference from the structure of FIG. 9 is that an n-type Al _0.2 Ga _0.8 As cladding layer 1001 is provided instead of the second n-type Al _0.4 Ga _0.6 As cladding layer 904. It is a point. The layer thickness of the n-type Al _0.2 Ga _0.8 As cladding layer 1001 was 0.2 μm.

The thickness of the n-type Al _0.2 Ga _0.8 As cladding layer 1001 grown after the growth interruption purge is reduced to 0.2 μm, and the Al content of the n-type Al _0.2 Ga _0.8 As cladding layer 1001 is further reduced. Is made smaller than the Al content of the first n-type Al _0.4 Ga _0.6 As cladding layer 903, so that the nitrogen in the growth chamber is grown by growing the n-type Al _0.2 Ga _0.8 As cladding layer 1001. It is possible to further reduce the concentration of the Al raw material, the Al reactant, the Al compound, or the Al remaining in the place where the impurities contained in the compound raw material or the nitrogen compound raw material come into contact. Thereby, the luminous efficiency of the active layer can be improved, and a GaInNAs material semiconductor laser with a low threshold current can be formed.

Example 3
FIG. 11 is a diagram showing a semiconductor laser according to Example 3 of the present invention. In FIG. 11, the same reference numerals are given to the same portions as those in FIG. 9. The structure of the semiconductor laser in FIG. 11 is similar to the structure of the semiconductor laser in FIG. A difference from the structure of FIG. 9 is that the first n-type Al _0.4 Ga _0.6 As clad layer 903 and the second n-type Al _0.4 Ga _0.6 As clad layer 904 are arranged. The n-type GaAs first intermediate layer 1101 and the n-type GaAs second intermediate layer 1102 are stacked.

  In Example 3, a growth interruption step was provided between the growth of the n-type GaAs first intermediate layer 1101 and the start of the growth of the n-type GaAs second intermediate layer 1102, and the growth chamber was purged with carrier gas. It is characterized by. By purging the growth chamber with carrier gas, the Al raw material, Al reactant, Al compound, or Al remaining in the growth chamber due to the growth of the n-type AlGaAs cladding layer 903 can be discharged to reduce the concentration.

  Further, since the intermediate layers 1101 and 1102 are made of a GaAs material, impurities such as oxygen are segregated on the outermost surface during the growth interruption purge process, and non-radiative recombination levels are formed on the growth interface. Can be suppressed. Therefore, the non-radiative recombination level at the growth interface can be reduced and the luminous efficiency of the active layer can be further improved.

Example 4
FIG. 12 is a diagram showing a surface emitting semiconductor laser according to a fourth embodiment of the present invention. The semiconductor laser shown in FIG. 12 includes a first n-type semiconductor multilayer reflector 1201, a second n-type semiconductor multilayer reflector 1202, a GaAs lower spacer layer 1203, a GaInNAs / GaAs multiple quantum on an n-type GaAs substrate 901. A well active layer 906, a GaAs upper spacer layer 1204, a p-type AlAs layer 1205, and a p-type semiconductor multilayer mirror 1206 are sequentially formed.

The n-type semiconductor multilayer mirror 1201 is a distributed Bragg reflector in which n-type GaAs high refractive index layers and n-type Al _0.8 Ga _0.2 As low refractive index layers are alternately stacked. Similarly, the p-type semiconductor multilayer film reflector 1206 is also composed of a distributed Bragg reflector in which p-type GaAs high refractive index layers and p-type Al _0.8 Ga _0.2 As low refractive index layers are alternately stacked. .

  The GaInNAs / GaAs multiple quantum well active layer 906 has a band gap wavelength of 1.3 μm. The first GaAs lower spacer layer 1202 to the GaAs upper spacer layer 1204 constitute a λ resonator.

The laminated structure is etched into a cylindrical shape until reaching the n-type semiconductor multilayer film reflecting mirror 1201 to form a mesa structure. The mesa size is 30 μmφ. Then, the p-type AlAs layer 1205 is selectively oxidized from the side surface exposed by etching to form the AlO _x insulating region 1207, thereby forming a current confinement structure. The current is concentrated in the oxide opening region of about 5 μmφ by the AlO _x insulating region 1207 and injected into the active layer 906.

  Reference numeral 910 denotes a ring-shaped p-side electrode formed on the surface of the p-type semiconductor multilayer film reflecting mirror 1206, and reference numeral 911 denotes an n-side electrode formed on the back surface of the n-type GaAs substrate 901.

  The light emitted from the GaInNAs / GaAs multiple quantum well active layer 906 is reflected and amplified by the upper and lower semiconductor multilayer reflectors 1201, 1202, 1206, and the 1.3 μm band laser light is perpendicular to the substrate (in FIG. 12). Radiates in the direction of the arrow.

FIG. 13 is a diagram showing in detail the junction between the first n-type semiconductor multilayer reflector 1201 and the second n-type semiconductor multilayer reflector 1202 in the surface emitting semiconductor laser shown in FIG. As shown in FIG. 13, the first n-type semiconductor multilayer mirror 1201 has n-type Al _0.8 Ga _0.2 As low-refractive index layers 1201a and n-type GaAs high-refractive index layers 1201b alternately stacked. Has been configured. The layer thicknesses of the n-type Al _0.8 Ga _0.2 As low-refractive index layer 1201a and the n-type GaAs high-refractive index layer 1201b are each ¼ optical wavelength thickness of the oscillation wavelength of 1.3 μm. Therefore, the uppermost layer of the first n-type semiconductor multilayer reflector 1201 is an n-type GaAs high refractive index layer 1201b having a quarter optical wavelength thickness.

The second n-type semiconductor multilayer mirror 1202 is formed by laminating one n-type GaAs high refractive index layer 1202a and n-type Al _0.4 Ga _0.6 As low refractive index layer 1202b. Yes. Here, the layer thickness of the n-type GaAs high refractive index layer 1202a is ½ optical wavelength thickness of the oscillation wavelength of 1.3 μm, and the n-type Al _0.4 Ga _0.6 As low refractive index layer. The layer thickness of 1202b is a quarter optical wavelength thickness of an oscillation wavelength of 1.3 μm.

  Therefore, an n-type GaAs high refractive index layer having a total optical thickness of 3/4 is formed at the junction between the first n-type semiconductor multilayer reflector 1201 and the second n-type semiconductor multilayer reflector 1202. Yes. This satisfies the light phase matching condition in the distributed Bragg reflector.

In Example 4, crystal growth is performed using a single MOCVD apparatus, TMG, TMA, and TMI are used as Group III materials, and AsH ₃ and DMHy are used as Group V materials. Then, after the growth of the n-type GaAs high refractive index layer 1201b, which is the uppermost layer of the first n-type semiconductor multilayer mirror 1201, and the n-type GaAs high refractive index layer 1202a of the second n-type semiconductor multilayer mirror 1202. It is characterized in that a growth interruption process is provided between the start of growth and growth.

  By purging the growth chamber while flowing the carrier gas during the growth interruption, the Al raw material, Al reactant, Al compound, or Al remaining in the growth chamber due to the growth of the first n-type semiconductor multilayer reflector 1201 is removed. , It can be discharged to reduce the concentration.

Further, in the second n-type semiconductor multilayer mirror 1202 grown after the growth interruption purge, the semiconductor layer containing Al has an n-type Al _0.4 Ga _0.6 As low refractive index having a layer thickness of about 0.1 μm. Only the layer 1202b is provided. Therefore, the layer thickness of the semiconductor layer containing Al is as thin as about 0.1 μm, and the Al content is also n-type Al _0.8 Ga _0.2 constituting the first n-type semiconductor multilayer mirror 1201. It is smaller than the As low refractive index layer 1201a. Thereby, the Al concentration remaining in the growth chamber can be suppressed, and the Al and oxygen concentrations taken into the GaInNAs well layer can be reduced. Therefore, the luminous efficiency of the active layer can be improved.

  In the growth interruption purge step, the n-type GaAs high-refractive index layer 1201b, which is the uppermost layer of the first n-type semiconductor multilayer reflector 1201, and the n-type GaAs height of the second n-type semiconductor multilayer reflector 1202 are used. Since it is provided between the refractive index layers 1202a, it is performed during the growth of the GaAs material. GaAs is known to be a stable material that is chemically inactive compared to a material containing Al, such as AlGaAs, and hardly forms an interface state. Therefore, it is difficult to form a non-radiative recombination level at the growth interface.

In the surface emitting semiconductor lasers of FIGS. 12 and 13, n-type Al _0.4 Ga _0.6 As is provided between the interface where the growth is interrupted and the GaInNAs / GaAs multiple quantum well active layer 906 containing nitrogen. A low refractive index layer 1202b is provided. Since the band gap energy of the n-type Al _0.4 Ga _0.6 As low-refractive index layer 1202b is larger than that of the GaAs spacer layer 1202, it overflowed from the GaInNAs / GaAs multiple quantum well active layer 906 to the GaAs spacer layer 1202. Carriers are blocked by the n-type Al _0.4 Ga _0.6 As low-refractive index layer 1202b having a large band gap. Therefore, the rate at which carriers overflowed from the GaInNAs / GaAs multiple quantum well active layer 906 are recombined and lost at the non-radiative recombination level at the interface where the growth is interrupted is reduced. Accordingly, leakage current can be suppressed. Thereby, a high-performance 1.3 μm band surface emitting semiconductor laser can be realized.

  In this embodiment, the growth interruption process is provided only once. However, it can be provided a plurality of times during the growth of the n-type semiconductor multilayer mirror.

Example 5
FIG. 15 is a diagram illustrating the optical transmission module according to the fifth embodiment of the present invention. In the optical transmission module of FIG. 15, a semiconductor light emitting element (semiconductor laser) 1502 which is a light source is provided on a substrate 1501. In order to monitor the light intensity of the light output from the semiconductor light emitting element 1502, a monitoring light receiving element 1503 is integrated. The semiconductor light emitting device 1502 is driven by a drive circuit 1505 in accordance with an electrical signal input to the optical transmission module, and generates an optical signal. Note that a signal from the monitor light receiving element 1503 is fed back to the drive circuit 1505 in order to keep the light intensity of the semiconductor light emitting element 1502 constant.

  An optical signal generated in the semiconductor light emitting device 1502 is guided in a waveguide, coupled to an optical fiber 1508, and output to the outside.

  On the other hand, an optical signal transmitted from the same optical fiber 1508 is branched by an optical branch 1507 in the optical transmission module and guided to the light receiving element 1504. The optical signal input to the light receiving element 1504 is converted into an electric signal, amplified by the receiving circuit 1506, and output as an electric signal of a predetermined format.

  The optical transmission module of FIG. 15 has a light source and a light receiving unit integrated in a hybrid manner, and has a method of inputting / outputting optical signals through a single optical fiber.

  As a feature of the fifth embodiment, the semiconductor light emitting device 1502 uses the semiconductor laser of the third embodiment. In the semiconductor laser of Example 3, the GaInNAs / GaAs multiple quantum well active layer 906 oscillates in a 1.3 to 1.6 μm band suitable for transmission of a quartz optical fiber. Since the conduction band discontinuity between the GaInNAs well layer and the GaAs barrier layer can be increased to, for example, 200 meV or more, electrons that overflow from the GaInNAs well layer to the GaAs barrier layer can be suppressed. Therefore, a characteristic temperature of 150K or higher can be obtained. Therefore, it is possible to form an optical transmission module that operates stably with respect to changes in environmental temperature without using an electronic cooling element.

  Further, a growth interruption step is provided between the growth of the n-type GaAs first intermediate layer 1101 and the start of the growth of the n-type GaAs second intermediate layer 1102, and the growth chamber is purged with a carrier gas, whereby the n-type AlGaAs is purged. The Al raw material, Al reactant, Al compound, or Al remaining in the growth chamber by the growth of the cladding layer 903 can be discharged to reduce the Al concentration. As a result, the concentration of Al and oxygen incorporated in the GaInNAs well layer can be sufficiently reduced to suppress a decrease in light emission efficiency, so that a low threshold current GaInNAs material-based semiconductor laser having an AlGaAs cladding layer is formed. can do. Therefore, the power consumption of the optical transmission module can be reduced.

Example 6
FIG. 16 is a diagram illustrating an optical transmission module according to a sixth embodiment of the present invention. In the optical transmission module of FIG. 16, a semiconductor laser array 1601 as a light source is provided on a substrate 1501. Each semiconductor laser in the semiconductor laser array 1601 is individually operated by a drive circuit 1505. Optical signals output from the respective semiconductor lasers of the semiconductor laser array 1601 are coupled to the optical fibers 1508 and output to the outside. In FIG. 16, the case of 4 channels is shown as an example.

  Since the optical transmission module of FIG. 16 can transmit optical signals in parallel, the transmission capacity can be further increased.

  The semiconductor laser array 1601 uses an element in which the semiconductor lasers of the third embodiment are monolithically integrated. As a result, similarly to the fifth embodiment, it is possible to form an optical transmission module that operates stably with respect to changes in environmental temperature without using an electronic cooling element, and to reduce power consumption of the optical transmission module. be able to.

Example 7
FIG. 17 is a diagram illustrating an optical switching apparatus 1701 according to the seventh embodiment of the present invention. In FIG. 17, the four-channel optical signals input from the optical fiber 1508 of the port A are input to the light receiving element array 1703 and converted into electric signals. A signal path is selected by the matrix switch 1704 and distributed to each channel. In the surface emitting laser array 1702, each element of the surface emitting laser array 1702 is driven according to the distributed signal, converted into an optical signal, and output from the optical fiber at the port B.

  Similarly, the path of the optical signal input from the port D is selected by the mat risk switch 1704 and output from the port C.

  Although FIG. 17 shows an example in which optical signals input to four optical fibers are output to four optical fibers, the number of inputs and the number of outputs are not necessarily the same.

  In FIG. 17, the surface emitting laser array 1702 is formed by monolithically integrating the vertical cavity surface emitting laser elements of the fourth embodiment. By using the vertical cavity surface emitting laser element, there is an advantage that the operating current can be reduced to several mA or less and the manufacturing cost can be reduced.

In the vertical cavity surface emitting laser device of Example 4, the GaInNAs / GaAs multiple quantum well active layer 906 has a high electron confinement effect in the well layer. Further, the semiconductor multilayer mirrors 1201, 1202, 1206 are composed of distributed Bragg reflectors in which GaAs high refractive index layers and Al _0.8 Ga _0.2 As low refractive index layers are alternately stacked. A high reflectivity mirror having low resistance and thermal resistance can be formed. Therefore, a 1.3 μm band surface emitting laser with good temperature characteristics can be realized.

  Further, after the growth of the first lower semiconductor multilayer mirror 1201 containing Al, the Al raw material remaining in a place where the nitrogen compound raw material or impurities contained in the nitrogen compound raw material come into contact with the growth chamber or the Al reactant, or Al A step of removing the compound or Al is performed. As a result, the Al raw material, Al reactant, Al compound, or Al remaining in the growth chamber due to the growth of the first lower semiconductor multilayer mirror 1201 is removed once.

  Thereafter, the second lower semiconductor multilayer mirror 1202 containing Al is grown. By reducing the layer thickness, the Al concentration remaining in the growth chamber is reduced, and the GaInNAs / GaAs multiple quantum well is formed. The luminous efficiency of the active layer 906 is improved.

  Therefore, by using the vertical cavity surface emitting laser element shown in the fourth embodiment for an optical switching device, the optical switching device can operate stably against changes in environmental temperature and reduce power consumption. it can.

Example 8
FIG. 18 is a diagram illustrating an optical transmission system according to an eighth embodiment of the present invention. In the optical transmission system of FIG. 18, an optical signal generated by the optical transmission unit 1801 is transmitted to the optical reception unit 1802 through the optical fiber 1508. In the example of FIG. 18, the optical transmission unit 1801, the optical fiber 1508, and the optical reception unit 1802 are provided in two lines so that bidirectional communication is possible. The optical transmission unit 1801 and the optical reception unit 1802 are integrated in one package and constitute an optical transmission / reception module 1803.

  The eighth embodiment is characterized in that the vertical cavity surface emitting laser element of the fourth embodiment is used as the light source of the optical transmitter 1801. Thereby, the optical transmission part which operate | moves stably with respect to the change of environmental temperature can be formed, without using an electronic cooling element. In addition, the power consumption of the optical transmitter can be reduced.

  When the configuration shown in the fifth embodiment is used as the optical transmission / reception module 1803, bidirectional communication can be performed using one optical fiber. Further, when the configuration shown in the sixth embodiment is used for the optical transmission unit 1801, optical signals can be transmitted in parallel using a plurality of optical fibers, so that the transmission capacity can be increased.

Example 9
FIG. 19 is a diagram illustrating an optical transmission system according to a ninth embodiment of the present invention. The optical transmission system according to the ninth embodiment has a configuration in which the optical switching device 1701 according to the seventh embodiment is provided between four optical transmission / reception modules 1803 and connected by an optical fiber 1508. Thereby, optical signals can be transmitted between the four devices. Note that by changing the number of inputs and outputs of the optical switching device 1701, any number of devices can be connected.

  The light source of the optical transmission / reception module 1803 and the optical switching device 1701 uses the vertical cavity surface emitting laser element shown in the fourth embodiment, and thus operates stably with respect to changes in the environmental temperature and is consumed. Electric power can be reduced.

The present invention can be used for an optical transmission module, an optical switching device, an optical transmission system, and the like.

201 substrate 202 first semiconductor layer containing Al 203 intermediate layer 204 active layer containing nitrogen 205 second semiconductor layer 501 first semiconductor layer containing Al 502 second semiconductor layer containing Al 503 third semiconductor layer 701 Intermediate layer 801 First lower semiconductor multilayer reflector 802 Second lower semiconductor multilayer reflector 803 Lower spacer layer 804 Upper spacer layer 805 Upper multilayer reflector 901 n-type GaAs substrate 902 n-type GaAs buffer layer 903 first 1 n-type Al _0.4 Ga _0.6 As cladding layer 904 Second n-type Al _0.4 Ga _0.6 As cladding layer 905 GaAs lower optical waveguide layer 906 GaInNAs / GaAs multiple quantum well active layer 907 GaAs upper portion Optical waveguide layer 908 p-type Al _0.4 Ga _0.6 As cladding layer 909 p-type GaAs Contact layer 910 p-side electrode 911 n-side electrode 1001 n-type Al _0.2 Ga _0.8 As cladding layer 1101 n-type GaAs first intermediate layer 1102 n-type GaAs second intermediate layer 1201 first n-type GaAs / Al _{0 .8} Ga _0.2 As semiconductor multilayer mirror 1202 Second n-type GaAs / Al _0.8 Ga _0.2 As semiconductor multilayer mirror 1203 GaAs lower spacer layer 1204 GaAs upper spacer layer 1205 AlAs layer 1206 p-type GaAs / Al _0.8 Ga _0.2 As semiconductor multilayer mirror 1207 AlO _x insulating region 1501 substrate 1502 semiconductor light emitting element 1503 monitor light receiving element 1504 light receiving element 1505 driving circuit 1506 receiving circuit 1507 optical branching 1508 optical fiber 1601 semiconductor laser array 1701 Conversion device 1702 Surface emitting laser array 1703 Light receiving element array 1704 Matrix switch 1801 Optical transmission unit 1802 Optical reception unit 1803 Optical transmission / reception module

JP-A-10-126044 JP 2000-4068 A

Electricon. Lett. 2000, 36 (21), pp 1776-1777.

Claims (10)

A substrate, and a first semiconductor layer including Al stacked on the substrate;
A second semiconductor layer formed on the first semiconductor layer and having a layer thickness smaller than that of the first semiconductor layer and containing Al;
An intermediate layer formed on the second semiconductor layer;
In a semiconductor light emitting device including an active layer made of a nitrogen-based group V mixed crystal semiconductor formed on the intermediate layer,
The first semiconductor layer and the second semiconductor layer are grown using an organometallic Al raw material, and the active layer is grown using a nitrogen compound raw material ,
Al source material remaining in a place where the nitrogen compound source material or impurities contained in the nitrogen compound source material are in contact with each other between the growth of the first semiconductor layer and the start of the growth of the second semiconductor layer, or Al A step of removing a reactant, an Al compound, or Al is performed, and the band gap energy of the second semiconductor layer is larger than that of the intermediate layer, and a non-radiative recombination level forming impurity in the active layer containing nitrogen A semiconductor light emitting device characterized in that the concentration of is the same as or lower than the concentration in the intermediate layer. 2. The semiconductor light emitting device according to claim 1, wherein the concentration of the non-light emitting recombination level forming impurity in the active layer containing nitrogen is an oxygen concentration. 2. The semiconductor light emitting device according to claim 1, wherein the Al concentration in the active layer containing nitrogen is equal to or lower than the Al concentration in the intermediate layer. 4. The semiconductor light emitting device according to claim 1, wherein an Al content of the second semiconductor layer containing Al is smaller than an Al content of the first semiconductor layer containing Al. 5. A semiconductor light emitting element characterized by the above. 5. The semiconductor light emitting device according to claim 1, wherein the first semiconductor layer containing Al includes a first low refractive index layer containing Al and a first refractive index layer stacked on a substrate. A first semiconductor multilayer film reflector in which high refractive index layers not containing Al are alternately stacked, and a second semiconductor layer containing Al is formed on the first semiconductor multilayer film reflector, A second semiconductor multilayer mirror in which a low-refractive index layer containing Al and a second high-refractive index layer not containing Al are laminated, and emits light in a direction perpendicular to the substrate. Type semiconductor light emitting device. 6. The surface emitting semiconductor light emitting device according to claim 5, wherein the Al content of the low refractive index layer containing the second Al is smaller than the Al content of the low refractive index layer containing the first Al. A surface-emitting type semiconductor light emitting device. A substrate, and a first semiconductor layer including Al stacked on the substrate;
A second semiconductor layer formed on the first semiconductor layer and having a layer thickness smaller than that of the first semiconductor layer and containing Al;
An intermediate layer formed on the second semiconductor layer;
In a method for manufacturing a semiconductor light emitting device including an active layer made of a nitrogen-based group V mixed crystal semiconductor formed on the intermediate layer,
The first semiconductor layer and the second semiconductor layer are grown using an organometallic Al raw material, and the active layer is grown using a nitrogen compound raw material ,
The band gap energy of the second semiconductor layer is larger than that of the intermediate layer,
Al source material remaining in a place where the nitrogen compound source material or impurities contained in the nitrogen compound source material are in contact with each other between the growth of the first semiconductor layer and the start of the growth of the second semiconductor layer, or Al A method for manufacturing a semiconductor light emitting device, comprising a step of removing a reactant, an Al compound, or Al. An optical transmission module, wherein the semiconductor light emitting device according to claim 1 is used. An optical switching device comprising the semiconductor light emitting element according to claim 1. An optical transmission system comprising the optical transmission module according to claim 8 or the optical switching device according to claim 9.

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