JP2008227329A - Quantum well structure, semiconductor laser, spectroscopic measurement apparatus, and method for manufacturing quantum well structure - Google Patents

Abstract

The present invention provides a quantum well structure, semiconductor laser, and spectroscopic measurement apparatus capable of improving the performance of characteristics by realizing a quantum well structure in which a crystal having a thick In composition and a larger thickness than conventional ones is used as a quantum well layer. And a method of manufacturing a quantum well structure.
In a quantum well structure 12 in which a quantum well layer 10 is formed on an InP substrate, the quantum well layer 10 grows at a temperature of 440 ° C. or more and 510 ° C. or less, and the quantum well layer 10 is 2%. The compression strain was less than 10%.
[Selection] Figure 1

Description

  The present invention relates to a quantum well structure, a semiconductor laser, a spectroscopic measurement apparatus, and a method for manufacturing a quantum well structure.

  In recent years, spectroscopic instruments that perform medical diagnosis, environmental measurement, food inspection, gas concentration measurement, and the like using laser light in the mid-infrared region have attracted attention. As the laser light source, a small-sized, low power consumption and monochromatic light source is desirable, and a semiconductor laser is a promising candidate. In semiconductor lasers, it has been found that the introduction of strained quantum wells in the active layer significantly improves the laser performance in addition to increasing the oscillation wavelength. The well structure has become available for semiconductor lasers.

  In particular, a semiconductor laser using InGaAsP formed on an InP substrate has been vigorously researched and developed as a communication light source using an optical fiber, and a mature processing technique and excellent performance have been realized. The wavelength range that is the target of the semiconductor laser formed on the InP substrate was mainly 1.25 μm to 1.6 μm for the purpose of optical communication as described above.

  On the other hand, recently, by using an InGaAs / InGaAs (P) quantum well structure having a compressive strain of about 2% with respect to InP as an active layer, it is experimentally possible to realize a semiconductor laser that oscillates at a wavelength of 2.0 μm or more. Became clear. As a result, the application range of semiconductor lasers using InP-based materials, which has heretofore been almost limited to the optical communication field, has been expanded.

  Furthermore, by reducing the amount of Ga in InGaAs, the amount of compressive strain increases, and in the case of InAs with Ga as O, the strain amount is 3.2%, theoretically a wavelength of 2 μm to 3 μm. It has been found that laser emission in the band is possible. It is also known that the laser oscillation wavelength can be increased by adding N or Sb, which are group V atoms, to InAs.

M.M. Gendry, V.M. Drout, C.I. Santine III, and G.G. Hollinger, “Critical thickness of high strained InGaAs layers grown on InP by molecular beam,” Appl. Phys. Lett, Vol. 60, no. 18, 4 May 1992, p. 2249-2251

  Generally, in crystal growth of a high strain material system, three-dimensional island growth is induced by an increase in strain stress accompanying an increase in film thickness. This island growth significantly deteriorates the crystal quality of the quantum well structure. In a quantum well structure in which InGaAs on an InP substrate is a quantum well layer, this three-dimensional island-like growth becomes prominent when the compressive strain exceeds 2% with respect to InP (see Non-Patent Document 1 above). .

  Furthermore, in a crystal having a large In composition such as InAs or lnAsN, it is difficult to form a quantum well structure having a flat and steep interface because In atoms evaporate from the surface during growth. In this way, when island growth accompanying the increase in film thickness and evaporation of In atoms become prominent, the film thickness of a crystal with a large In composition (for example, InAs) cannot be increased, and light emission at 2 μm or more occurs. The problem that it cannot be obtained arises.

  In a conventional method for manufacturing a quantum well structure using a crystal having a large In composition as a quantum well layer, the conditions for suppressing island-like growth and evaporation of In atoms are not clear with respect to the growth temperature. It was difficult to get.

  The present invention has been made in view of the above circumstances, and can take island growth and evaporation of In atoms by taking an optimum growth temperature when forming a crystal with a large In composition. As a result, a quantum well structure in which a crystal with a large In composition and a thicker In composition is used as a quantum well layer, a quantum well structure, a semiconductor laser, a spectroscopic measurement device, and a quantum well structure capable of achieving high performance characteristics. It aims at providing the manufacturing method of.

A quantum well structure according to a first invention (corresponding to claim 1) for solving the above problem is
In a quantum well structure in which a quantum well layer is formed on an InP substrate,
The quantum well layer grows at a temperature between 440 ° C. and 510 ° C.,
The quantum well layer has a compressive strain of 2% or more and less than 10%.

A quantum well structure according to a second invention (corresponding to claim 2) for solving the above problem is the quantum well structure according to the first invention,
The band gap wavelength is 1.9 μm or more and 2.8 μm or less.

A quantum well structure according to a third invention (corresponding to claim 3) for solving the above-described problem is the quantum well structure according to the first invention or the second invention,
The quantum well layer has a thickness of 2 nm to 9 nm.

A quantum well structure according to a fourth invention (corresponding to claim 4) for solving the above problem is the quantum well structure according to any one of the first invention to the third invention,
The number of the quantum well layers is 1 to 7 layers.

A quantum well structure according to a fifth invention (corresponding to claim 5) for solving the above problem is the quantum well structure according to any one of the first to fourth inventions,
The quantum well layer is formed of any one of InAs, InGaAs, InAsN, and InAsSb.

A quantum well structure according to a sixth invention (corresponding to claim 6) for solving the above problem is the quantum well structure according to any one of the first to fifth inventions,
The barrier layer is characterized by being lattice-matched to InP or having a tensile strain of 2% or less.

A quantum well structure according to a seventh invention (corresponding to claim 7) for solving the above problem is the quantum well structure according to any one of the first to sixth inventions,
The quantum well structure is sandwiched between optical confinement layers,
The optical confinement layer is characterized by crystal growth at a temperature higher than the crystal growth temperature of the quantum well layer.

A semiconductor laser according to an eighth invention (corresponding to claim 8) for solving the above-described problem is
A quantum well structure according to any one of the first to seventh inventions;
The oscillation wavelength is 1.9 μm to 2.8 μm.

A semiconductor laser according to a ninth invention (corresponding to claim 9) for solving the above-mentioned problem is,
Having a quantum well structure according to an eighth invention;
A diffraction grating is formed on the optical confinement layer.

A semiconductor laser according to a tenth invention (corresponding to claim 10) for solving the above problem is the semiconductor laser according to the eighth invention or the ninth invention,
The laminated structure consisting of the cladding layer and the quantum well layer is formed in a mesa stripe shape,
A semi-insulating semiconductor crystal doped with Ru or Fe is buried on both sides of the laminated structure.

A semiconductor laser according to an eleventh invention (corresponding to claim 11) for solving the above problem is the semiconductor laser according to the eighth invention or the ninth invention,
A laminated structure composed of a cladding layer and the quantum well layer is formed in a mesa stripe shape,
A pn buried layer in which n-type and p-type InP layers are alternately laminated is buried on both sides of the laminated structure.

A spectroscopic measurement device according to a twelfth invention (corresponding to claim 12) for solving the above-mentioned problem is
A semiconductor laser according to any one of the eighth to eleventh aspects is used as a light source.

A method for manufacturing a quantum well structure according to a thirteenth invention (corresponding to claim 13) for solving the above-described problems is as follows.
In a method for manufacturing a quantum well structure in which a stacked structure having a first optical confinement layer, a quantum well layer, and a second optical confinement layer is grown on an InP substrate,
Crystal growth of the first optical confinement layer;
Crystal growth of the quantum well layer;
Crystal growth of the second optical confinement layer,
The temperature for crystal growth of the quantum well layer is 440 ° C. or more and 510 ° C. or less, and the temperature for crystal growth of the first optical confinement layer or the second optical confinement layer is a temperature for crystal growth of the quantum well layer It is characterized by being higher.

  According to the present invention, it is possible to easily produce a quantum well structure using a large crystal of In composition with a large amount of compressive strain and a thick In composition, which has been difficult to produce, and applied the structure. This is extremely useful for realizing high performance lasers.

  Embodiments of a quantum well structure, a semiconductor laser, a spectroscopic measurement apparatus, and a quantum well structure manufacturing method according to the present invention will be described with reference to FIGS. FIG. 1 is a schematic cross-sectional structure diagram showing a quantum well structure for explaining Example 1, FIG. 2 is a diagram showing an example of the relationship between growth temperature and quantum well layer strain, and FIG. 3 is a diagram showing InAs quantum well layer thickness and PL emission. FIG. 4 is a diagram showing an example of the relationship between peak wavelengths, FIG. 4 is a diagram showing an example of the relationship between the number of quantum well layers and the PL emission peak intensity, and FIG. 5 is a schematic cross-sectional structure showing an optical confinement quantum well structure for explaining Example 5 FIG. 6 is a schematic perspective view showing the structure of a broad contact laser for explaining the sixth embodiment, FIG. 7 is a schematic perspective view showing the structure of a ridge type DFB laser for explaining the seventh embodiment, and FIG. It is a schematic perspective view which shows the structure of the embedded DFB laser demonstrated.

First embodiment of the present invention using InAs having a compressive strain of 3.2% with respect to InP as the quantum well layer 10 and In _0.53 Ga _0.47 As lattice-matched to InP (the strain amount is 0) as the barrier layer 11 An example will be described with reference to FIG. As shown in FIG. 1, the quantum well structure 12 of the present embodiment includes an InP buffer layer 14 (thickness 200 nm), an InAs quantum well layer 10 and an InGaAs barrier layer 11 on the surface of an InP (100) substrate 13. The quantum well structure 12 and the InP cap layer 15 (thickness: 100 nm) are composed of two quantum well layers 10 and three barrier layers 11.

  As the InAs quantum well layer 10, a 5 nm InAs layer was used, and as the InGaAs barrier layer 11, a 16.5 nm thick InGaAs layer lattice-matched to InP was used. Crystal growth was performed by the MOVPE method with a reduced pressure of 50 Torr. The growth temperature was determined based on the value measured by placing a Si wafer with a thermocouple embedded in the susceptor of the MOVPE growth furnace. In all the samples, the growth temperature of the InP buffer layer 14 was 620 ° C., and the growth temperatures of the InAs quantum well layer 10, the InGaAs barrier layer 11, and the InP cap layer 15 were changed from 420 ° C. to 620 ° C.

  In addition, trimethylindium (TMIn) and triethylgallium (TEGa) were used as Group III materials, and arsine (AsH3) and phosphine (PH3) were used as Group V materials. An X-ray diffractometer manufactured by Philips was used to evaluate the structural characteristics of the sample. For evaluation of optical characteristics, photoluminescence (PL) measurement using a laser having a wavelength of 532 nm as a light source was performed at room temperature (25 ° C.).

  X-ray diffraction measurement was performed on samples having different growth temperatures. FIG. 2 shows the relationship between the growth temperature and the strain amount of the quantum well layer 10 of the fabricated sample. The growth temperature is plotted on the horizontal axis, and the strain amount of the quantum well layer 10 derived from the X-ray diffraction measurement results is plotted on the vertical axis. If the quantum well layer 10 is formed of InAs without deterioration, the strain amount must be 3.2%. As is apparent from FIG. 2, the sample produced at a growth temperature of 440 ° C. to 510 ° C. shows a strain amount of 3.2%.

  However, at 430 ° C. or lower and 520 ° C. or higher, the strain amount is 3.2% or less. This reveals that lattice relaxation occurs due to island-like growth of InAs or evaporation of In atoms, and a good quantum well structure 12 is not obtained. In addition, a sample with a plotted marker ◯ is a sample from which PL emission was obtained, and a sample with × represents a sample from which PL emission was not obtained.

  That is, no light emission is obtained at a growth temperature of 520 ° C. or higher. This is because the evaporation temperature of In atoms became active due to the high growth temperature, and the interface of the quantum well structure 12 was deteriorated. It was confirmed that a good quantum well structure 12 having the InAs layer as the quantum well layer 10 can be obtained by setting the growth temperature in the range of 440 ° C. to 510 ° C.

  From the above results, when producing the quantum well structure 12 using InAs as the quantum well layer 10, the quantum well structure 12 having good characteristics can be obtained by setting the growth temperature to 440 ° C. or more and 510 ° C. or less. Was confirmed.

  In this example, InAs was used as the quantum well layer 10, it was confirmed that a good quantum well structure 12 could be obtained similarly even when using InGaAs having a compressive strain of 2% or more with respect to the InP substrate. . Here, since the strain amount of InAs where the Ga composition ratio in InGaAs is zero is 3.2%, the range of the compressive strain amount is less than 3.2%.

  In this embodiment, an InGaAs layer lattice-matched to InP is used as the barrier layer 11. However, it is confirmed that a good quantum well structure 12 can be obtained even if a lattice-matched InGaAsP layer or InGaAlAs layer is used. It was.

  A second embodiment in which the thickness of the InAs quantum well layer 10 is different from that in the first embodiment will be described. The growth temperature and growth rate of the InAs quantum well layer 10 are in the range shown in Example 1. FIG. 3 shows the relationship between the film thickness of the InAs quantum well layer 10 and the PL emission peak wavelength. The horizontal axis plots the thickness of the InAs quantum well layer 10 and the vertical axis plots the PL emission peak wavelength. ● indicates the measurement point, and the solid line is the calculation result.

  Light emission was obtained even when the thickness of the InAs quantum well layer 10 was increased to 9 nm. The PL emission peak wavelength at this time was 2.62 μm. Further, since the relationship between the film thickness of the quantum well layer 10 and the emission wavelength is in good agreement with the calculation result, it was confirmed that a good quantum well structure 12 having InAs as the quantum well layer 10 was obtained. .

Example 3 in which Example 1 and the number of InAs quantum well layers 10 are different will be described. The quantum well layer 10 was made of 5 nm InAs, and the barrier layer 11 was made 16.5 nm or 20.0 nm In _0.46 Ga _0.54 As having a tensile strain of 0.5% with respect to InP. Other conditions are in the range shown in the first embodiment.

  FIG. 4 shows the relationship between the number of InAs quantum well layers 10 and the PL emission peak intensity. The number of InAs quantum well layers 10 is plotted on the horizontal axis, and the PL emission peak intensity is plotted on the vertical axis. Even when any barrier layer 11 was used, light emission was confirmed up to 10 InAs quantum well layers 10. When the number of quantum well layers 10 increases, strain stress in the quantum well structure 12 accumulates. Therefore, in the 16.5 nm InGaAs barrier layer 11, when the number of quantum well layers 10 is six or more, a single quantum well structure 12 is obtained. The emission intensity is less than half compared to.

  On the other hand, in the case where the 20.0 nm barrier layer 11 is used, the number of InAs quantum well layers 10 is eight, which is half or less. It was confirmed that the quantum well structure 12 including the seven InAs quantum well layers 10 was obtained by setting the barrier layer 11 to 20.0 nm. Here, although there is no restriction | limiting in the upper limit of the thickness of the barrier layer 11, when actually using for a device, about 100 nm is effective.

In this example, the strain amount of the barrier layer 11 was set to 0.5% tensile strain, but it was confirmed that the same result was obtained even when the lattice strain was matched to 2% tensile strain or InP.
For reference, an example of growth conditions for the quantum well layer 10 in Examples 1 to 3 is shown in Table 1.

  Example 4 in which the crystals constituting the quantum well layer 10 are different from Example 1 will be described. The quantum well layer 10 was made of 5 nm InAsN. Dimethylhydrazine (DMHy) was used as a raw material for N. The N composition of InAsN is 3%. Here, the N composition may be 1% or more and 5% or less.

  Other conditions are in the range shown in the first embodiment. When PL measurement of the produced quantum well structure 12 was performed, light emission having a peak wavelength of 2.8 μm was obtained, and it was confirmed that a good quantum well structure 12 was obtained.

  In this example, InAsN was used as the quantum well layer 10, it was confirmed that similar results were obtained even when InAsSb was used. Here, the amount of strain in InSb corresponding to the case where the As composition of InAsSb is zero is about 10%. Therefore, it is considered that the strain amount of InAsSb applicable to this example is less than 10%. In addition, considering the strain relaxation in InAsSb, a strain amount of 5% or less is effective.

  FIG. 5 shows a quantum well structure having an optical confinement (SCH) structure of Example 5. In this example, InGaAsP layers having a band gap wavelength of 1.3 μm lattice matched to InP were used as SCH layers above and below the quantum well structure 12. The SCH structure of this example is characterized in that the growth temperature of the SCH layer is higher than that of the quantum well structure 12. The quantum well structure 12 is the structure shown in the first to fourth embodiments.

A method for manufacturing the SCH structure of this example will be described. After the InP buffer layer 14 is grown at 620 ° C., the lower InGaAsP optical confinement layer 16 having a predetermined thickness is grown at 620 ° C. Thereafter, the InGaAs barrier layer 11 (see FIG. 1) is grown to 10 nm, and the growth temperature is lowered to the growth temperature (for example, 500 ° C.) of the InAs quantum well layer 10 (see FIG. 1) in an AsH ₃ atmosphere.

  After the growth of the InAs quantum well layer 10, the InGaAs barrier layer 11 is grown to 10 nm, and the growth temperature is raised to 620 ° C. Thereafter, the upper InGaAsP optical confinement layer 16 is grown. Thereafter, the InP cap layer 15 is grown. It was confirmed that even in such an SCH structure, characteristics equivalent to those shown in Examples 1 to 3 can be obtained.

In this example, after growing the InGaAsP optical confinement layer 16 and then growing InGaAs to 10 nm, the temperature was lowered to the growth temperature of the InAs quantum well layer 10 (see FIG. 1) in the AsH ₃ atmosphere. The quantum well structure 12 having the same characteristics can be obtained in the sequence in which the growth temperature is lowered while growing the InGaAs barrier layer 11 or the InGaAs quantum well layer 10 is grown in the AsH ₃ atmosphere after the growth of the InGaAs barrier layer 11. It was confirmed.

  In this example, the InGaAsP optical confinement layer 16 having a band gap wavelength of 1.3 μm was used as the SCH layer. However, similar characteristics were obtained with InGaAsP layers or InGaAs having other band gap wavelengths lattice-matched to InP. Moreover, it was confirmed that the same characteristics can be obtained by using any of these layers for the combination of the upper and lower SCH layers.

  In the present embodiment, the growth temperature of the layers other than the InAs quantum well layer 10 (see FIG. 1) is set to 620 ° C. Generally, high quality crystals can be grown at a growth temperature up to about 700 ° C.

A broad contact laser manufactured using the SCH structure shown in Example 5 will be described as Example 6 with reference to FIG. An n-type InP cladding layer 17 doped with Si at a concentration of 1 × 10 ¹⁸ cm ³ is grown on the InP substrate 13 (see FIG. 1), and the SCH structure shown in Example 5 is produced. Thereafter, a p-type InP cladding layer 18 and a p-type InGaAsP contact layer 19 doped with Zn at a concentration of 1 × 10 ¹⁸ cm ³ are sequentially formed.

The quantum well structure 12 used in this example includes three InAs quantum well layers 10 (see FIG. 1), an InGaAs barrier layer 11 (see FIG. 1) lattice-matched to 20.0 nm InP, and a 100 nm band gap. It consists of an InGaAsP optical confinement layer 16 with a wavelength of 1.3 μm. After the growth of the contact layer 19, a 40 μm wide stripe structure is formed using SiO ₂ as a mask 20, and a p-type electrode 21 is deposited. Thereafter, the InP substrate 13 is polished and an n-type electrode 22 is deposited on the back surface. Finally, the cavity length is cleaved to 900 μm, and a laser structure is manufactured.

In the laser of this embodiment, by changing the film thickness of the quantum well layer 10 (see FIG. 1), multimode oscillation at a wavelength of 1.9 μm to 2.6 μm can be obtained in continuous operation at room temperature. Was about 1.5 kA / cm ² , and an optical output of about 30 mW was obtained.
In this embodiment, InAs is used as the quantum well layer 10, by using InAsN or InAsSb for the quantum well layer 10, oscillation up to 2.8 μm can be obtained, and the same results can be obtained for other characteristics. confirmed.

  As a seventh embodiment, a ridge type distributed feedback laser manufactured using the SCH structure shown in the fifth embodiment will be described with reference to FIG. After the SCH structure is fabricated in the same manner as in Example 5, a diffraction grating is formed on the upper InGaAsP optical confinement layer 16 using electron beam exposure and wet etching to produce a distributed feedback (DFB) structure.

Thereafter, the p-type InP cladding layer 18 and the InGaAsP contact layer 19 are regrown. After the contact layer 19 is grown, a 1.5 μm wide stripe structure is produced by using dry etching and wet etching together with SiO ₂ as a mask 20. Thereafter, SiO ₂ 20 is formed on the side of the stripe, and a p-type electrode 21 is deposited. After the n-type electrode 22 is formed, it is cleaved to a resonator length of 900 μm, and a ridge type DFB laser structure is produced.

  In the laser of this example, single mode oscillation at a wavelength of 1.9 μm to 2.8 μm was obtained in continuous operation at room temperature, the threshold current was about 30 mA, and an optical output of about 5 mW was obtained. In any laser, a wavelength change of 4 nm was possible by controlling the injection current and the operating temperature.

An embedded DFB laser manufactured using the SCH structure shown in Example 5 will be described as Example 8 with reference to FIG. After producing the DFB structure as in Example 7, the p-type InP cladding layer 18 is regrown. Thereafter, a stripe structure having a width of 1.4 μm is formed by using dry etching and wet etching using SiO ₂ as a mask 20 (see FIG. 7).

  Thereafter, the stripe side is filled with semi-insulating InP doped with ruthenium (Ru). Thereafter, the p-type InP cladding layer 18 is stacked and grown, and an InGaAsP contact layer 19 is further formed. P-type and n-type electrodes are formed and cleaved to a resonator length of 900 μm, and an embedded DFB laser is manufactured. The laser of this example had the same characteristics as in Example 7.

  In this example, a semi-insulating InP layer doped with Ru was used as the buried layer 23 beside the stripe. However, a semi-insulating InP layer doped with Fe, or a pn layer in which n-type and P-type InP layers are alternately stacked. It was confirmed that similar characteristics were obtained when the buried layer was used.

As a ninth embodiment, a gas molecule spectroscopic measurement apparatus using the DFB laser shown in the seventh and eighth embodiments will be described. This spectroscopic measurement device is described in Examples 7 and 8 having the same oscillation wavelength as the absorption lines of gas molecules (for example, CO ₂ : 2.05 μm, N ₂ O: 2.13 μm, CO: 2.33 μm). By using a DFB laser, it was possible to measure with a sensitivity of two orders of magnitude or more compared to the case of using a laser in the conventional communication wavelength band.

  The present invention can be applied to, for example, a high-quality quantum well structure having a quantum well layer with a large compressive strain, a semiconductor laser, a spectroscopic measurement device, and a method for manufacturing a quantum well structure.

1 is a schematic sectional view showing a quantum well structure for explaining Example 1. FIG. It is a figure which shows an example of the relationship between growth temperature and quantum well layer distortion amount. It is a figure which shows an example of the relationship between an InAs quantum well layer film thickness and PL light emission peak wavelength. It is a figure which shows an example of the relationship between the number of quantum well layers, and PL light emission peak intensity. FIG. 6 is a schematic cross-sectional structure diagram showing an optical confinement quantum well structure for explaining Example 5; FIG. 9 is a schematic perspective view showing a structure of a broad contact laser for explaining Example 6. FIG. 10 is a schematic perspective view showing the structure of a ridge type DFB laser for explaining Example 7. FIG. 10 is a schematic perspective view showing the structure of an embedded DFB laser for explaining Example 8.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 InAs quantum well layer 11 InGaAs barrier layer 12 Quantum well structure 13 InP substrate 14 InP buffer layer 15 InP cap layer 16 InGaAsP optical confinement layer 17 n-type InP clad layer 18 p-type InP clad layer 19 p-type InGaAsP contact layer 20 SiO ₂ Mask 21 P-type electrode 22 N-type electrode

Claims (13)

In a quantum well structure in which a quantum well layer is formed on an InP substrate,
The quantum well layer grows at a temperature between 440 ° C. and 510 ° C.,
The quantum well structure has a compressive strain of 2% or more and less than 10%. The quantum well structure according to claim 1,
A quantum well structure having a band gap wavelength of 1.9 μm or more and 2.8 μm or less. In the quantum well structure according to claim 1 or 2,
The quantum well structure has a thickness of 2 nm to 9 nm. In the quantum well structure according to any one of claims 1 to 3,
The quantum well structure has one to seven quantum well layers. In the quantum well structure according to any one of claims 1 to 4,
The quantum well structure is formed of any one of InAs, InGaAs, InAsN, and InAsSb. In the quantum well structure according to any one of claims 1 to 5,
A quantum well structure characterized in that the barrier layer has lattice matching with InP or has a tensile strain of 2% or less. In the quantum well structure according to any one of claims 1 to 6,
The quantum well structure is sandwiched between optical confinement layers,
The quantum well structure, wherein the optical confinement layer is crystal-grown at a temperature higher than a crystal growth temperature of the quantum well layer. A quantum well structure according to any one of claims 1 to 7,
A semiconductor laser having an oscillation wavelength of 1.9 μm to 2.8 μm. The quantum well structure according to claim 8,
A semiconductor laser, wherein a diffraction grating is formed in the optical confinement layer. In the semiconductor laser according to claim 8 or 9,
The laminated structure consisting of the cladding layer and the quantum well layer is formed in a mesa stripe shape,
A semiconductor laser characterized in that a semi-insulating semiconductor crystal doped with Ru or Fe is buried on both sides of the laminated structure. In the semiconductor laser according to claim 8 or 9,
A laminated structure composed of a cladding layer and the quantum well layer is formed in a mesa stripe shape,
A semiconductor laser characterized in that a pn buried layer in which n-type and p-type InP layers are alternately laminated is buried on both sides of the laminated structure. 12. A spectroscopic measurement device using the semiconductor laser according to claim 8 as a light source. In a method for manufacturing a quantum well structure in which a stacked structure having a first optical confinement layer, a quantum well layer, and a second optical confinement layer is grown on an InP substrate,
Crystal growth of the first optical confinement layer;
Crystal growth of the quantum well layer;
Crystal growth of the second optical confinement layer,
The temperature for crystal growth of the quantum well layer is 440 ° C. or more and 510 ° C. or less, and the temperature for crystal growth of the first optical confinement layer or the second optical confinement layer is a temperature for crystal growth of the quantum well layer A manufacturing method of a quantum well structure characterized by being higher.

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