JP2012059964A - Emission wavelength adjustment method of semiconductor optical device and method for manufacturing semiconductor optical device using the same - Google Patents

Abstract

A method of manufacturing a semiconductor optical device capable of adjusting a light emission wavelength in an active layer to a desired wavelength and improving a yield.
An n-type InP clad layer 2, a GaInAsP active layer 3, a p-type InP clad layer 4 and a p-type GaInAsP cap layer 11 are sequentially grown on an n-type InP substrate 1 doped with sulfur. Estimate the short wavelength shift amount at the time of regrowth from the regrowth temperature, add the predicted short wavelength shift amount to 1.48 μm which is the peak wavelength value of PL emission of the GaInAsP active layer 3 to be finally obtained. The obtained value is 1.50 μm, and the composition of the GaInAsP quantum well layer is designed so that a peak wavelength of 1.50 μm is obtained.
[Selection] Figure 1

Description

  The present invention relates to a method for adjusting a light emission wavelength of a semiconductor optical device and a method for manufacturing a semiconductor optical device using the same, and more particularly, a semiconductor optical device in which an active layer is provided using an InP substrate doped with sulfur (S). The present invention relates to an emission wavelength adjusting method and a semiconductor optical device manufacturing method.

  In an optical communication system, a semiconductor optical device is indispensable. For semiconductor optical devices and semiconductor optical modulators as signal light sources in optical communications, an active layer made of GaInAsP formed on an InP semiconductor substrate is often used. As a semiconductor substrate, one using an InP substrate to which sulfur which is an n-type dopant is added is known (for example, see Patent Document 1).

JP 2003-60309 A

S. D. Perrion, et al., J. Elect. Mat. 23 (1994) 81.

  In the case of an active layer having a quantum well structure, a phenomenon is known in which element mutual diffusion occurs at the interface between the well layer and the barrier layer due to heat treatment, and the emission wavelength shifts to the short wavelength side (for example, Non-Patent Document 1). reference). For this reason, when manufacturing the above-mentioned semiconductor optical device, the quantum well structure of the active layer is heated at the time of multiple times of selective growth, etc. It is known to shift to the side.

  On the other hand, in a semiconductor optical device having a specific oscillation wavelength in which a diffraction grating is formed along an active layer, such as a distributed feedback (DFB) semiconductor laser, the detuning amount deviates from the design value. As a result, the threshold current increases and the optical output decreases, or the single mode property of the oscillation spectrum deteriorates. The detuning amount refers to the difference between the peak wavelength (emission wavelength) of the photoluminescence (PL) emission of the active layer and the oscillation wavelength determined by the distance between the diffraction gratings. In particular, in a coolerless DFB laser driven without using an electronic cooler, the emission wavelength of the quantum well varies depending on the temperature of the driving environment. For this reason, for example, in an operating environment of -40 degrees to 90 degrees, it is desirable that the detuning amount is 0 to 5 meV in order to prevent an increase in threshold current and a decrease in light output. .

  Here, in the heat treatment step in the process of manufacturing the semiconductor laser, the amount of shift of the emission wavelength toward the short wavelength side varies, so that the desired emission wavelength cannot be obtained, and the semiconductor optical devices manufactured on different substrates However, there is a problem that the emission wavelength varies. For this reason, there was a problem that the manufacturing yield of the semiconductor optical device was lowered. In particular, in the case of a coolerless DFB laser, there is a problem in that the detuning amount varies as a result, and the yield significantly decreases.

  The present invention has been made in view of the above, and an emission wavelength adjustment method for a semiconductor optical device capable of adjusting an emission wavelength in an active layer to a desired wavelength, and a semiconductor using the same to improve yield An object of the present invention is to provide a method for manufacturing an optical element.

  The inventors of the present invention determined that the emission wavelength of an active layer having a quantum well structure grown on an InP substrate doped with sulfur (S) is not only the active layer structure such as composition and film thickness, but also an InP substrate by heat treatment. It has been found that the shift amount is shifted to the short wavelength side according to the sulfur concentration in the medium. The present invention has been completed by conceiving that this is applied to the method for adjusting the emission wavelength of the active layer.

  In order to solve the above-described problems and achieve the object, the present invention provides a semiconductor in which an active layer is formed on an InP semiconductor substrate containing sulfur (S), and a heat treatment process is performed after the formation of the active layer. A method for adjusting the emission wavelength of an optical element, which takes into account the relationship between the sulfur concentration in the semiconductor substrate and the short wavelength shift amount by which the emission wavelength in the active layer shifts to the short wavelength side in accordance with the heat treatment step. Then, the sulfur concentration or the active layer structure is determined so that the active layer has a desired emission wavelength after the heat treatment step.

  The method for adjusting the emission wavelength of a semiconductor optical device according to the present invention is characterized in that, in the above invention, the active layer contains GaInAsP.

Moreover, the emission wavelength adjusting method for a semiconductor optical device according to the present invention is characterized in that, in the above invention, the sulfur concentration is 1 × 10 ¹⁸ to 1 × 10 ¹⁹ cm ⁻³ .

  The method for adjusting the emission wavelength of a semiconductor optical device according to the present invention is the above-described invention, wherein the active layer structure is constant, and a predetermined sulfur concentration based on the relationship between the sulfur concentration and the short wavelength shift amount. The semiconductor substrate is selected.

  Also, the method for adjusting the emission wavelength of a semiconductor optical device according to the present invention is the above-described invention, wherein the sulfur concentration of the semiconductor substrate is constant, and the activity is based on the relationship between the sulfur concentration and the short wavelength shift amount. The layer structure is determined.

  The method for adjusting the emission wavelength of a semiconductor optical device according to the present invention is characterized in that, in the above invention, the active layer structure is defined by the film thickness and composition of the quantum well layer and the barrier layer.

  Moreover, in the above invention, the method for adjusting the emission wavelength of the semiconductor optical device according to the present invention is characterized in that the temperature range used in the heat treatment step is 600 ° C. to 800 ° C.

  In order to solve the above-described problems and achieve the object, the present invention includes an active layer forming step of forming an active layer on an InP semiconductor substrate containing sulfur (S), and an active layer forming step after the active layer forming step. And a heat treatment step, comprising: a sulfur concentration of the semiconductor substrate; and a short wavelength shift amount at which an emission wavelength in the active layer is shifted to a short wavelength side in accordance with the heat treatment step. The sulfur concentration or the active layer structure is determined in advance so that the active layer has a desired emission wavelength after the heat treatment step.

  The method for manufacturing a semiconductor optical device according to the present invention is characterized in that, in the above invention, the active layer contains GaInAsP.

In the method of manufacturing a semiconductor optical device according to the present invention, the sulfur concentration is 1 × 10 ¹⁸ to 1 × 10 ¹⁹ cm ⁻³ in the above invention.

  In the method of manufacturing a semiconductor optical device according to the present invention, the active layer structure is defined by the thickness and composition of the quantum well layer and the barrier layer.

  Moreover, the method for manufacturing a semiconductor optical device according to the present invention includes, in the above invention, an optical waveguide forming step of forming an optical waveguide including the active layer in a mesa structure, and the heat treatment step is performed in the width direction of the optical waveguide. The method is characterized in that it is a step of forming a buried layer in contact with both side surfaces of the substrate.

  The method for manufacturing a semiconductor optical device according to the present invention is characterized in that, in the above invention, a temperature range used in the heat treatment step is 600 ° C. to 800 ° C.

  The method for manufacturing a semiconductor optical device according to the present invention is characterized in that, in the above invention, a step of further forming a diffraction grating layer on the active layer is provided.

  According to the present invention, it is possible to realize a method for adjusting the emission wavelength of a semiconductor optical device that can adjust the emission wavelength in the active layer to a desired wavelength. In addition, according to the present invention, it is possible to realize a method of manufacturing a semiconductor optical device that improves the yield without variation in emission wavelength between the semiconductor optical devices.

FIG. 1 is a cross-sectional process diagram illustrating a method of manufacturing a semiconductor optical device according to the first embodiment of the present invention. FIG. 2 is a cross-sectional process diagram illustrating the method of manufacturing the semiconductor optical device according to the first embodiment of the present invention. FIG. 3 is a cross-sectional process diagram illustrating the method of manufacturing the semiconductor optical device according to the first embodiment of the present invention. FIG. 4 is a cross-sectional process diagram illustrating the method of manufacturing the semiconductor optical device according to the first embodiment of the present invention. FIG. 5 is a diagram showing the relationship between the carrier concentration of the substrate, the short wavelength shift amount, and the heat treatment temperature in the semiconductor optical device. FIG. 6 is a diagram showing the relationship between the annealing temperature, the short wavelength shift amount, and the carrier concentration of the substrate in the heat treatment step. FIG. 7 is a cross-sectional process diagram illustrating a method of manufacturing a semiconductor optical device according to the second embodiment of the present invention. FIG. 8 is a cross-sectional process diagram illustrating a method of manufacturing a semiconductor optical device according to the second embodiment of the present invention. FIG. 9 is a cross-sectional process diagram illustrating a method of manufacturing a semiconductor optical device according to the second embodiment of the present invention. FIG. 10 is a cross-sectional process diagram illustrating a method of manufacturing a semiconductor optical device according to the second embodiment of the present invention. FIG. 11 is a cross-sectional process diagram illustrating a method of manufacturing a semiconductor optical device according to the second embodiment of the present invention. FIG. 12 is a cross-sectional process diagram illustrating a method of manufacturing a semiconductor optical device according to the second embodiment of the present invention. FIG. 13 is a cross-sectional process diagram illustrating a method of manufacturing a semiconductor optical device according to the second embodiment of the present invention. FIG. 14 is a partially broken perspective view showing a semiconductor optical device according to the second embodiment of the present invention. FIG. 15 is a diagram showing the relationship between the sulfur concentration, the number of manufactured products, and the yield at which the obtained peak wavelength difference is within 5 meV (corresponding to a wavelength difference of 10 nm in the case of the emission wavelength of 1550 nm).

  Below, the light emission wavelength adjustment method of the semiconductor optical element which is a form for implementing this invention is demonstrated.

(Semiconductor optical device emission wavelength adjustment method)
In the method for adjusting the emission wavelength of the semiconductor optical device according to the present embodiment, an active layer made of GaInAsP is formed on an InP substrate as a semiconductor substrate containing sulfur (S), and a heat treatment step is performed after the formation of this active layer. It is applied to a semiconductor optical device manufactured through the process.

  This light emission wavelength adjusting method takes into account the relationship between the sulfur concentration in the InP substrate and the short wavelength shift amount at which the light emission wavelength in the active layer shifts to the short wavelength side in accordance with the heat treatment step, so that the active layer is in the heat treatment step. Later, the sulfur concentration or active layer structure of the InP substrate is determined so that the desired emission wavelength is obtained.

  Further, as a method for adjusting the emission wavelength of the semiconductor optical device, the active layer structure is made constant, and the sulfur concentration in the InP substrate and the short wavelength shift amount at which the emission wavelength in the active layer shifts to the short wavelength side in accordance with the heat treatment step. Based on the relationship, an InP substrate having a predetermined sulfur concentration may be selected.

  Furthermore, as a method for adjusting the emission wavelength of the semiconductor optical device, the sulfur concentration of the InP substrate may be constant, and the active layer structure may be determined based on the relationship between the sulfur concentration and the short wavelength shift amount. This active layer structure is defined by the film thickness and composition of the quantum well layer and the barrier layer. In addition, as the heat treatment step, the buried layer may be regrown in contact with both side surfaces of the mesa stripe mesa structure. When the temperature range used for such a heat treatment step is 600 ° C. or higher, the generation of reaction gas in the metal organic vapor phase epitaxy is good, and if it is 800 ° C. or lower, desorption of adsorbed elements does not occur. This is a good condition for crystal growth. Therefore, the temperature range used for the heat treatment step is preferably 600 ° C to 800 ° C.

(Method for manufacturing semiconductor optical device)
Next, a method for manufacturing a semiconductor optical device using the above-described emission wavelength adjusting method will be described with reference to the drawings. However, it should be noted that the drawings are schematic, and the thicknesses and ratios of the layers are different from actual ones. Moreover, the part from which the relationship and ratio of a mutual dimension differ also in between drawings is contained. Therefore, specific dimensions should be determined in consideration of the following description.

(Embodiment 1)
1 to 4 are process cross-sectional views of the method for manufacturing a semiconductor optical device according to the first embodiment of the present invention. The semiconductor optical device according to the first embodiment has a structure having no diffraction grating.

In the first embodiment, an n-type InP substrate 1 having a sulfur (S) concentration of 3 × 10 ¹⁸ cm ⁻³ is prepared. As shown in FIG. 1, an n-type InP cladding layer 2, a GaInAsP active layer 3, a p-type InP cladding layer 4, and a p-type GaInAsP cap layer 11 are sequentially formed on the n-type InP substrate 1 at a substrate temperature of 580 ° C. Grow. Here, the thickness of the n-type InP cladding layer 2 is 1 μm, the thickness of the GaInAsP active layer 3 is 0.5 μm, the thickness of the p-type InP cladding layer 4 is 1.2 μm, and the thickness of the p-type GaInAsP cap layer 11. Is 0.05 μm. Thereafter, as shown in FIG. 1, an etching mask 12 made of a SiNx dielectric film is formed in a stripe pattern on the p-type GaInAsP cap layer 11. Then, using this etching mask 12 as a mask, a mesa stripe as shown in FIG. 2 is formed by wet etching or dry etching. Note that SiO ₂ or the like may be used as the etching mask 12.

  The GaInAsP active layer 3 is a multi-layer consisting of four GaInAsP compressive strain quantum well layers (thickness 7 nm) having a lattice mismatch of about 1% and a GaInAsP barrier layer (thickness 10 nm) having a composition wavelength of 1.2 μm. A quantum well structure and six multi-stage optical confinement (SCH) layers in which the thickness of each layer with a composition wavelength changed from 0.95 μm to 1.2 μm is 40 nm can be formed. Further, when the lattice mismatch degree of the GaInAsP active layer 3 is increased, a strain compensation structure in which the net strain amount of the quantum well layer is reduced by using GaInAsP having a lattice mismatch degree that causes tensile strain in the barrier layer. Can be used.

Further, the emission wavelength of the GaInAsP active layer 3 can be measured using a photoluminescence (PL) method. When determining the composition of the GaInAsP active layer 3, the regrowth is performed from the S concentration (3 × 10 ¹⁸ cm ⁻³ ) of the n-type InP substrate to be used and two regrowth temperatures described later with reference to FIGS. 5 and 6. The short wavelength shift amount (20 nm) at this time is expected. The value 1.50 μm obtained by adding the predicted short wavelength shift amount to 1.48 μm which is the PL wavelength peak wavelength value of the GaInAsP active layer 3 to be finally obtained is obtained, and the peak wavelength of 1.50 μm is obtained. The structure of the GaInAsP active layer 3 is designed so as to be obtained. That is, the structure of the GaInAsP active layer 3 may be designed in advance so that the emission wavelength of the GaInAsP active layer 3 is on the long wavelength side.

  5 and 6 show the relationship between the carrier concentration (sulfur concentration), the short wavelength shift amount, and the heat treatment temperature. As the carrier concentration increases, the short wavelength shift amount increases, and even if the carrier concentration is constant, the heat treatment temperature is increased. It can be seen that the short wavelength shift amount increases with increasing.

  Incidentally, as the film thickness of the quantum well layer decreases, the short wavelength shift amount increases, and as the film thickness increases, the short wavelength shift amount decreases. Therefore, by setting the thickness of the quantum well layer in advance by a predetermined amount, when the wavelength is shortened, the quantum well layer can be controlled to have a desired emission wavelength.

  Next, as shown in FIG. 3, a p-type InP current blocking layer is formed in a region other than the upper surface of the mesa stripe by utilizing the feature of the metal organic chemical vapor deposition method that the crystal does not grow on the etching mask 12 made of a dielectric. A current blocking region composed of the 5 and n-type InP current blocking layer 6 is formed, and the current blocking region on the side surface of the mesa stripe is grown so as to be substantially horizontal to the etching mask 12. This is the first regrowth, and the growth temperature at that time is 670 ° C.

  Thereafter, the etching mask 12 and the p-type GaInAsP cap layer 11 are removed by etching, and the p-type InP cladding layer 7 and the p-type GaInAsP contact layer 8 having a composition wavelength of 1.2 μm are again formed by metal organic chemical vapor deposition. For about 3 μm. This is the second regrowth, and the substrate temperature at that time is 630 ° C. Thereafter, in order to adjust the thickness of the substrate, the lower surface of the n-type InP substrate 1 (the surface opposite to the surface on which each of the semiconductor layers described above is formed) is thinned by polishing until it has a thickness of about 130 μm. As shown, an n-side electrode 9 is formed on the lower surface of the n-type InP substrate 1, and a p-side electrode 10 is formed on the upper surface of the p-type GaInAsP contact layer 8. As a crystal growth method in this step, a molecular beam epitaxy (MBE) method or an actinic beam epitaxy (CBE) method may be used. In this way, the manufacture of the semiconductor optical device 20 is completed.

  Since the semiconductor optical device 20 manufactured as described above is designed with the quantum well layer taking into account the short wavelength shift of the GaInAsP active layer 3 that occurs in two re-growths, it is as short as before. Compared to a semiconductor optical device manufactured without predicting the amount of wavelength shift, the probability of finally obtaining a semiconductor optical device 20 having a desired emission wavelength is increased, and the yield is improved.

  The S concentration of the n-type InP substrate 1 in FIGS. 5 and 6 can be measured by secondary ion mass spectrometry (SIMS).

(Embodiment 2)
7 to 14 show a method for manufacturing a semiconductor optical device according to the second embodiment of the present invention. 7 to 9 are cross-sectional process diagrams in which the semiconductor optical device is cut in the x direction which is the optical waveguide direction (extension direction of the mesa stripe). FIGS. 10 to 13 show the optical waveguide direction of the semiconductor optical device. It is sectional process drawing cut | disconnected in the y direction which is the width direction of the mesa stripe which makes a right angle.

First, in the second embodiment, an n-type InP substrate 31 having a sulfur (S) dose of 3.1 × 10 ¹⁸ cm ⁻³ is prepared.

  Then, as shown in FIG. 7, an n-type InP cladding layer 32 and a GaInAsP active layer 33 having a multiple quantum well structure are sequentially formed on the n-type InP substrate 31 at a substrate temperature of 580 ° C. by metal organic vapor phase epitaxy. Then, a p-type InP clad layer 34, a p-type GaInAsP diffraction layer 35, and a p-type InP cap layer 36 are sequentially grown. The n-type InP clad layer 32 has a thickness of 1 μm, and the GaInAsP active layer 33 includes a multiple quantum well structure including barrier layers having a quantum well layer thickness of 3.9 nm and a thickness of 10 nm, and GRIN sandwiching the quantum well structure -In total with the layer thickness of the SCH (Graded-Index Separate-Confinement Heterostructure) layer, the layer thickness is 0.22 μm. The thickness of the p-type InP clad layer 34 is 150 nm, the thickness of the p-type GaInAsP diffraction layer 35 is 20 nm, and the thickness of the p-type InP cap layer 36 is 10 nm. The GaInAsP active layer 33 is designed with a quantum well layer in consideration of a short wavelength shift accompanying regrowth described later.

  Next, an etching mask layer (not shown) is formed so as to form a diffraction grating with a desired interval along the x direction which is the optical waveguide direction, and the p-type InP cap layer 36, using this etching mask layer as a mask, Then, the p-type GaInAsP diffraction layer 35 is etched, and finally the p-type InP cap layer 36 is removed to form a diffraction grating 35A as shown in FIG.

  Next, as shown in FIG. 9, the p-type InP clad layer 37 is grown by metal organic vapor phase epitaxy, and the diffraction grating 35A is embedded, and at the same time, the p-type InP clad layer 37 stacked on the diffraction grating, p The type GaInAsP cap layer 38 is grown at a substrate temperature of 580 ° C. This is the first regrowth.

  Further, on the p-type GaInAsP cap layer 38, an etching mask layer 39 made of a SiNx dielectric film is formed in a stripe shape extending in the x direction as shown in FIG. As shown in FIG. 10, this etching mask layer 39 is formed with a predetermined width in the y direction (a width longer than the mesa stripe width dimension by a predetermined length). Then, using this etching mask layer 39 as a mask, as shown in FIG. 10, a mesa stripe was formed by using a wet etching method, a dry etching method, or the like.

  Next, as shown in FIG. 11, by utilizing the feature of the metal organic chemical vapor deposition method in which no crystal is grown on the etching mask layer 39 made of a dielectric by the same method as in the first embodiment, the mesa is used. A current blocking region composed of a p-type InP current blocking layer 40 and an n-type InP current blocking layer 41 is formed in a region other than the upper surface of the stripe so that the current blocking region on the side surface of the mesa stripe is substantially horizontal to the etching mask layer 39. To grow. This is the second regrowth, and the growth temperature at that time is 640 ° C.

  Thereafter, as shown in FIG. 12, the etching mask layer 39 and the p-type GaInAsP cap layer 38 are removed by etching. Then, using the metal organic chemical vapor deposition method again, as shown in FIG. 13, a p-type InP cladding layer 42 and a p-type GaInAsP contact layer 43 having a composition wavelength of 1.2 μm are grown by about 3 μm. This is the third regrowth, and the growth temperature at that time is 630 ° C. Thereafter, in order to adjust the thickness of the substrate, the lower surface of the n-type InP substrate 31 (the surface opposite to the surface on which each semiconductor layer described above is formed) is thinned by polishing to a thickness of about 130 μm and shown in FIG. As described above, the n-side electrode 44 and the p-side electrode 45 are formed on the lower surface of the n-type InP substrate 31 and the upper surface of the p-type GaInAsP contact layer 43, respectively. As a crystal growth method in this step, a molecular beam epitaxy method or a chemical beam epitaxy method may be used. In this way, the manufacture of the semiconductor optical device 50 according to the present embodiment is completed.

  Since the semiconductor optical device 50 according to the present embodiment manufactured as described above is designed with the quantum well layer in consideration of the short wavelength shift of the GaInAsP active layer 33 that occurs in three regrowths in advance. Compared to a conventional semiconductor device manufactured without expecting a short wavelength shift amount, the probability of finally obtaining a semiconductor device having a desired emission wavelength is increased, and the yield is improved.

  The detuning amount, which is the difference between the emission wavelength of the GaInAsP active layer 33 and the oscillation wavelength determined by the interval between the diffraction gratings 35A, is 0 in order to prevent an increase in threshold current and a decrease in optical output. Although it is considered desirable to be ˜5 meV, when a semiconductor optical device is manufactured without predicting the short wavelength shift amount during regrowth as in the prior art, even if the same manufacturing method is used, the depletion depends on the sulfur concentration of the substrate used. The tuning amount varies from 0 to several tens meV. For this reason, if the short wavelength shift amount is predicted in advance, the structure (composition, film thickness, etc.) of the active layer should be designed so that the peak wavelength of PL emission of the GaInAsP active layer 33 becomes longer. , Yield reduction can be suppressed.

  Furthermore, if the peak wavelength of PL emission of the manufactured GaInAsP active layer 33 is measured by the PL method at the stage shown in FIG. 7, the peak wavelength of PL emission of the GaInAsP active layer 33 is assumed to be the value designed above. Even if there is a difference, a further improvement in yield can be expected by adjusting the interval of the diffraction grating 35A to be manufactured so as to correct the difference.

  As described above, the present invention provides an active layer forming step for forming an active layer on a semiconductor substrate (InP substrate) containing sulfur (S), and an optical waveguide for forming an optical waveguide including the active layer in a mesa structure. The above-described wavelength adjustment method is applied to a method for manufacturing a semiconductor optical device including a waveguide forming step and a heat treatment step performed after the optical waveguide forming step. In other words, it takes into account the relationship between the sulfur concentration of the semiconductor substrate and the short wavelength shift amount at which the emission wavelength in this active layer shifts to the short wavelength side in accordance with the heat treatment step performed after the active layer formation step. The sulfur concentration or the active layer structure is determined in advance so that the emission wavelength of the active layer is on the long wavelength side so that the layer has a desired emission wavelength after the heat treatment step.

(Other embodiments)
Although the embodiment of the present invention has been described above, it should not be understood that the description and the drawings, which constitute a part of the disclosure of the above embodiment, limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  For example, in the first and second embodiments described above, the emission wavelength in this active layer is accompanied by a heat treatment process performed after the active layer forming process using n-type InP substrates 1 and 31 having a predetermined sulfur concentration. In view of the relationship with the short wavelength shift amount that shifts to the short wavelength side, the active layer is activated in advance so that the active layer has a long emission wavelength so that the active layer has a desired emission wavelength after the heat treatment step. The layer structure has been determined, but the structure of the active layer is kept constant, and the n-type InP substrate is added in consideration of the relationship with the short wavelength shift amount at which the emission wavelength in the active layer shifts to the short wavelength side with the heat treatment step The sulfur concentration of 1, 31 may be determined.

For example, when the DFB laser described in Embodiment 2 having a quantum well structure that emits light at 1550 nm is manufactured, the short wavelength shift amount in three heat treatment steps (heat treatment at a maximum of 640 ° C.) is desired to be about 5 meV. From the graph of FIG. 6, it is understood that a sulfur concentration of about 3 × 10 ¹⁸ cm ⁻³ may be used. Actually, Embodiment 2 having a quantum well structure that emits light at 1550 nm using n-type InP substrates having different sulfur concentrations in the range of 3.1 × 10 ¹⁸ cm ⁻³ to 5.3 × 10 ¹⁸ cm ^−3. The DFB laser described in 1) was fabricated, and the PL emission wavelength was compared with the peak wavelength of spontaneous emission light due to electroluminescence (EL) during current injection. FIG. 15 shows the yield in which the obtained peak wavelength difference is within 5 meV (corresponding to a wavelength difference of 10 nm when the emission wavelength is 1550 nm).

From FIG. 15, by determining the sulfur concentration within the range of 3.1 × 10 ¹⁸ cm ⁻³ to 3.5 × 10 ¹⁸ cm ⁻³ , regardless of the plurality of heat treatment steps in the DFB laser manufacturing process, While the emission wavelength of the desired quantum well structure can be obtained, when the sulfur concentration is 3.6 × 10 ¹⁸ cm ⁻³ or more, the short wavelength shift amount with respect to the heat treatment temperature of this embodiment is large. It can be seen that the emission wavelength of the structure cannot be realized and the yield is not good. Although the temperature reproducibility in the heat treatment process can be a factor that fluctuates the yield, it is possible to use an InP substrate having a lower sulfur concentration so that the short wavelength shift amount with respect to the temperature in the heat treatment process of this embodiment is small. It can also be seen from the results of FIG. 6 that the influence of temperature variations in the manufacturing process can be suppressed.

  In particular, the above-described active layer structure can be set by the thickness and composition of the well layer and the barrier layer.

  In the first and second embodiments, the heat treatment step is a step of forming buried layers in contact with both side surfaces in the width direction of the optical waveguide. However, the present invention can also be applied to other heat treatment steps. Needless to say.

1 n-type InP substrate 2 n-type InP clad layer 3 GaInAsP active layer 4 p-type InP clad layer 5 p-type InP current blocking layer 6 n-type InP current blocking layer 7 p-type InP clad layer 8 p-type GaInAsP contact layer 9 n side Electrode 10 p-side electrode 11 p-type GaInAsP cap layer 20 semiconductor optical device 31 n-type InP substrate 32 n-type InP clad layer 33 GaInAsP active layer 34 p-type InP clad layer 35 p-type GaInAsP diffraction layer 35A diffraction grating 36 p-type InP cap Layer 37 p-type InP cladding layer 38 p-type GaInAsP cap layer 39 etching mask layer 40 p-type InP current blocking layer 41 n-type InP current blocking layer 42 p-type InP cladding layer 43 p-type GaInAsP contact layer 44 n-side electrode 45 p-side Electrode 50 Semiconductor photoelement

Claims (14)

A method for adjusting an emission wavelength of a semiconductor optical device, wherein an active layer is formed on an InP semiconductor substrate containing sulfur (S), and a heat treatment step is performed after the formation of the active layer,
In consideration of the relationship between the sulfur concentration of the semiconductor substrate and the short wavelength shift amount at which the emission wavelength of the active layer shifts to the short wavelength side in the heat treatment step, the active layer is desired after the heat treatment step. A method for adjusting an emission wavelength of a semiconductor optical device, wherein the sulfur concentration or the active layer structure is determined so as to obtain an emission wavelength.   The method for adjusting the emission wavelength of a semiconductor optical device according to claim 1, wherein the active layer contains GaInAsP. The method for adjusting the emission wavelength of a semiconductor optical device according to claim 1, wherein the sulfur concentration is 1 × 10 ¹⁸ to 1 × 10 ¹⁹ cm ⁻³ .   4. The semiconductor substrate having a predetermined sulfur concentration is selected based on a relationship between the sulfur concentration and the short wavelength shift amount, wherein the active layer structure is constant. The light emission wavelength adjustment method of the semiconductor optical element as described in one.   The active layer structure is determined based on the relationship between the sulfur concentration and the short wavelength shift amount, with the sulfur concentration of the semiconductor substrate being constant. The light emission wavelength adjustment method of the semiconductor optical element of description.   6. The method for adjusting the emission wavelength of a semiconductor optical device according to claim 1, wherein the active layer structure is defined by the film thickness and composition of a quantum well layer and a barrier layer.   The method for adjusting the emission wavelength of a semiconductor optical device according to any one of claims 1 to 6, wherein a temperature range used in the heat treatment step is 600 ° C to 800 ° C. An active layer forming step of forming an active layer on a semiconductor substrate containing sulfur (S);
A heat treatment step performed after the active layer forming step;
A method of manufacturing a semiconductor optical device comprising:
In consideration of the relationship between the sulfur concentration of the semiconductor substrate and the short wavelength shift amount at which the emission wavelength of the active layer shifts to the short wavelength side in the heat treatment step, the active layer is desired after the heat treatment step. A method for producing a semiconductor optical device, wherein the sulfur concentration or the active layer structure is determined in advance so as to obtain an emission wavelength.   9. The method of manufacturing a semiconductor optical device according to claim 8, wherein the semiconductor substrate is an InP substrate, and the active layer contains GaInAsP. The method for manufacturing a semiconductor optical device according to claim 8, wherein the sulfur concentration is 1 × 10 ¹⁸ to 1 × 10 ¹⁹ cm ⁻³ .   The method of manufacturing a semiconductor optical device according to claim 8, wherein the active layer structure is defined by a film thickness and a composition of a quantum well layer and a barrier layer. An optical waveguide forming step of forming an optical waveguide including the active layer into a mesa structure;
12. The method of manufacturing a semiconductor optical device according to claim 8, wherein the heat treatment step is a step of forming buried layers in contact with both side surfaces in the width direction of the optical waveguide.   The method for manufacturing a semiconductor optical device according to any one of claims 8 to 12, wherein a temperature range used in the heat treatment step is 600 ° C to 800 ° C.   14. The method of manufacturing a semiconductor optical integrated device according to claim 8, further comprising a step of forming a diffraction grating layer on the active layer.

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