JP4014861B2 - Compound semiconductor device and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
In the present invention, a distributed feedback semiconductor laser element (hereinafter referred to as a DFB laser) and an optical modulator (hereinafter referred to as an EA optical modulator) using a modulation method based on electroabsorption are abutted (hereinafter referred to as a butt joint). More specifically, the present invention relates to a compound semiconductor device bonded and integrated by a bonding method, and more specifically, a compound semiconductor device having a layer structure with reduced coupling loss, low light absorption, and good device characteristics, and a method for manufacturing the compound semiconductor device It is about.
[0002]
[Prior art]
An optical modulator-semiconductor laser element integrated semiconductor optical element in which an optical modulator and a single longitudinal mode semiconductor laser element as a light source of the optical modulator are monolithically integrated has been developed and put into practical use.
As one of such integrated semiconductor optical elements, an electroabsorption optical modulator (hereinafter referred to as an EA optical modulator) that utilizes a change in absorption coefficient due to an electric field is used as an optical modulator, and a light source of the EA optical modulator. In particular, a semiconductor optical device including a distributed feedback semiconductor laser device (hereinafter referred to as a DFB laser) has attracted attention.
[0003]
Here, with reference to FIGS. 5 and 6A to 6C, the configuration of a conventional EA optical modulator-DFB laser / integrated semiconductor optical device (hereinafter referred to as EA-DFB laser) 80 will be described. To do. 5 is a plan view of a conventional EA-DFB laser, FIG. 6 (a) is a cross-sectional view taken along line II-II in FIG. 5, and FIG. 6 (b) is taken along line III-III in FIG. FIG. 6C is a cross-sectional view taken along line IV-IV.
A conventional EA-DFB laser 80 includes a GaInAsP-based SI-BH (Semi-Insulating Buried Heterostructure) type DFB laser 80A and an EA optical modulator in which a heterojunction structure including a multiple quantum well structure is embedded in a semi-insulating buried layer. As shown in FIG. 6A, a DFB laser 80A and an EA light modulator 80B are coaxially monolithically arranged in a waveguide direction on one n-InP substrate 12 as shown in FIG. It is what was collected in.
[0004]
As shown in FIG. 6A, the DFB laser 80A includes an n-InP lower cladding layer 14 having a film thickness of 100 nm, a band gap wavelength on the DFB laser region of the n-InP substrate 12 common to the EA optical modulator 80B. SCH-MQW16 with 5 wells made of GaInAsP with λg of 1.55 μm, p-InP upper cladding layer 18 with a thickness of 100 nm, and a diffraction grating forming layer 20 with a thickness of 10 nm made of GaInAsP with a bandgap wavelength λg of 1.2 μm The p-InP upper cladding layer 24 having a thickness of 200 nm including the p-InP cap layer 22 and the p-InP having a thickness of 2000 nm, which are respectively common to the EA optical modulator 80B. It has a laminated structure of an InP upper cladding layer 32 and a p-GaInAs contact layer 38 having a thickness of 300 nm. .
[0005]
The upper part of the lower clad layer 14 having the above-described laminated structure, the SCH-MQW 16, the upper clad layer 18, the diffraction grating 20a, the upper clad layer 24 including the p-InP cap layer 22, the upper clad layer 32, and the contact layer 34 are shown in FIG. As shown in FIG. 6B, a mesa structure 46 is formed. Further, both sides of the mesa structure 46 are embedded with a semi-insulating Fe-doped InP layer (hereinafter referred to as an Fe—InP layer) 36 that is common to the EA optical modulator 80B.
A common passivation film 44 made of a SiN film is formed on the Fe—InP layer 36 on both sides of the mesa structure 46 except for the window 50 on the contact layer 34.
A p-side electrode 38 is formed on the contact layer 34 through a window 50, and a common n-side electrode 42 is formed on the back surface of the common n-InP substrate 12.
[0006]
As shown in FIG. 6A, the EA optical modulator 80B includes an n-InP buffer layer 26 having a film thickness of 50 nm, a band gap on the EA optical modulator region of the n-InP substrate 12 common to the DFB laser 80A. A SCH-MQW 28 with 9 wells made of GaInAsP with a wavelength λg of 1.50 μm, a p-InP upper cladding layer 30 with a thickness of 150 nm, and a p-InP upper cladding layer 32 with a thickness of 2000 nm that is common to the DFB laser 80A, respectively. And a p-GaInAs contact layer 34 having a thickness of 300 nm.
[0007]
The upper part of the n-InP buffer layer 26, the SCH-MQW 28, the upper cladding layer 30, the upper cladding layer 32, and the contact layer 34 having the above-described stacked structure are formed as a mesa structure 48 along the waveguide direction. Further, both sides of the mesa structure 48 are buried with a semi-insulating Fe—InP layer 36 common to the DFB laser 80A.
A common passivation film 44 made of a SiN film is formed on the Fe—InP layer 36 on both sides of the mesa structure 48 except for the window 52 on the contact layer 34.
A p-side electrode 40 is formed on the contact layer 34 through a window, and a common n-side electrode 40 is formed on the back surface of the common n-InP substrate 12.
[0008]
The carrier concentration of each layer is 5 × 10 5 in the lower cladding layer 14.¹⁷cm^-35 × 10 5 for the upper cladding layer 24¹⁷cm^-35 × 10 in the buffer layer 26¹⁷cm^-35 × 10 for the upper cladding layer 30¹⁷cm^-31 × 10 for the upper cladding layer 32¹⁸cm^-31 × 10 in the contact layer 38¹⁹cm^-3It is.
[0009]
A method for manufacturing the above-described conventional EA-DFB laser 80 will be described. FIGS. 7A to 7D are cross-sectional views showing respective steps in manufacturing the EA-DFB laser, and FIGS. 8A and 8B each manufacture the EA-DFB laser. It is a top view which shows the mask pattern at the time of doing.
First, a GaInAsP-based DFB laser structure is formed up to the waveguide layer on the entire surface of the n-InP substrate 12 having the DFB laser region and the EA light modulator region.
That is, the n-InP lower clad layer 14, the SCH-MQW 16, the p-InP upper clad layer 18, the diffraction grating formation layer 20, and the p-InP cap layer 22 are epitaxially grown on the entire surface of the n-InP substrate 12, for example, by MOCVD. Let
Next, as shown in FIG. 7A, the cap layer 22 and the diffraction grating forming layer 20 are etched to form the diffraction grating 20a, and then the p-InP upper cladding layer 24 is epitaxially grown to form the diffraction grating 20a. A laminated structure having the cladding layer 24 is formed on the diffraction grating 20a.
[0010]
Next, as shown in FIG. 7B, the SiN butt joint mask 60 shown in FIG. 8A is formed to cover the stacked structure in the DFB laser region, and the EA light modulator region exposed from the mask is formed. The stacked structure formed in this step is etched to expose the n-InP substrate 12.
Subsequently, as shown in FIG. 7C, the GaInAsP-based EA optical modulator structure is selectively grown on the n-InP substrate 12 in the EA optical modulator region where the GaInAsP-based EA optical modulator structure is exposed. That is, the n-InP buffer layer 26, the SCH-MQW 28, and the p-InP upper clad layer 30 are epitaxially grown on the n-InP substrate 12 by, for example, the MOCVD method to form a stacked structure.
[0011]
Next, after removing the butt joint mask 60 in the DFB laser region, the p-InP upper cladding layer 32 and the p-GaInAs contact layer 34 are epitaxially grown on the entire surface of the substrate as shown in FIG.
Next, a stripe-shaped SiN stripe mask 64 having a width of 2 μm shown in FIG. 8B is successively formed on the stacked structure in the DFB laser region and the stacked structure in the EA light modulator region, respectively. Dry etching is performed using these as a mask.
Thus, in the DFB laser region, the upper portion of the lower clad layer 14, the SCH-MQW 16, the upper clad layer 18, the diffraction grating 20a, the upper clad layer 24 including the p-InP cap layer 22, the upper clad layer 32, and the contact layer A mesa structure 46 composed of 34 is formed.
On the other hand, in the EA optical modulator region, a mesa structure 48 including the upper part of the n-InP buffer layer 26, the SCH-MQW 28, the p-InP upper clad layer 30, the upper clad layer 32, and the contact layer 34 is formed.
[0012]
Next, the stripe mask 64 is used as a selective growth mask in each of the DFB laser region and the EA optical modulator region, and a semi-insulating Fe—InP current blocking layer 36 is embedded and grown to form the mesa structure 46, 48 formed. Embed both sides.
Furthermore, the EA-DFB laser 80 can be manufactured by forming the passivation film 44, the p-side electrodes 38 and 40, the n-side electrode 40, and the like.
Conventional example
When the sample of this conventional example was manufactured by the above-described conventional manufacturing method, the device characteristics of the EA-DFB laser were as follows: threshold current 12 mA, extinction ratio 15 dB at 3 V bias, and FFP (far field pattern) noise. It was the result that there was.
[0013]
[Problems to be solved by the invention]
However, the conventional EA-DFB laser manufactured according to the above-described manufacturing method has the following problems.
As a first problem, the light incident on the EA optical modulator from the DFB laser has a coupling loss due to the difference between the mode fields 72a and 72b on the coupling surface, as schematically shown in FIG. There was a problem of getting bigger.
Here, the mode field refers to the distribution shape of light propagating inside the element. The coupling loss refers to a loss at the time of coupling of light between different areas, and is largely caused by a difference in mode fields.
Furthermore, since this fabrication method uses the butt joint method, the film thickness near the coupling portion is actually large in the EA optical modulator due to side growth by the mask, as schematically shown in FIG. Become. As a result, the difference between the mode fields 74a and 74b on the coupling surface is further increased, and the coupling loss is larger than expected.
FIG. 9A shows an actual layer structure and a mode field in consideration of side growth in the conventional EA-DFB laser 80.
[0014]
In order to suppress the coupling loss at the coupling surface, conventionally, it has been attempted to configure the layer structures of the DFB laser and the EA optical modulator so that the mode fields match. However, this method is often different from the structure in which the device characteristics of the EA-DFB laser are optimized, and there is a problem that, for example, the device characteristics such as an increase in the oscillation threshold and a decrease in the extinction ratio are deteriorated. was there.
[0015]
As a second problem, as shown in FIG. 9B, the band gap wavelength in the EA optical modulator becomes longer as compared with the region without a side growth (flat region) as it approaches the coupling surface. There was a problem that light absorption occurred.
In other words, the band gap wavelength in the EA optical modulator is 1500 nm in the region where there is no side growth (flat region), but gradually increases as it approaches the coupling surface, and reaches about 1550 nm on the coupling surface.
FIG. 9B shows a graph of the band gap wavelength along the ridge stripe of the conventional EA-DFB laser 80.
[0016]
Furthermore, these coupling losses and light absorption have caused problems that device characteristics deteriorate, such as a reduction in laser light output, a deterioration in extinction ratio, and an increase in noise in the emitted light.
Accordingly, an object of the present invention is to provide a compound semiconductor device having a layer structure with reduced coupling loss, low light absorption, and good device characteristics, and a method for manufacturing the compound semiconductor device.
[0017]
[Means for Solving the Problems]
The present inventor has conceived to change the film thickness in the vicinity of the coupling portion of the EA optical modulator by changing the shape of the mask at the time of butt joint growth in order to suppress coupling loss in the vicinity of the coupling portion, It confirmed by experiment and came to invent this invention.
That is, if the structure in which the film thickness in the vicinity of the coupling portion of the EA optical modulator is made smaller than that of the conventional one and close to the film thickness of the DFB laser is formed, the difference in mode field on the coupling surface is reduced.
For this purpose, a mask as shown in FIG. 4A is used instead of the conventional mask shown in FIG. The mask shown in FIG. 4A includes a butt joint mask 60 on the DFB laser region and a selective region growth mask 62 on the EA light modulator region. The butt joint mask 60 and the selective region growth mask 62 are predetermined. Place them apart by an interval of.
By using a mask as shown in FIG. 4A, as shown in FIG. 1, the increase in film thickness due to side growth in the vicinity of the coupling portion is limited to a narrow region, and as the distance from the coupling surface increases, the film thickness increases. Is once thinned and then gradually increases in shape.
By taking the above shape, as schematically shown in FIG. 1, the difference between the mode fields 70 and 70b on the coupling surface is reduced, and the coupling loss is reduced.
[0018]
Moreover, said structure has the effect of reducing light absorption for the following reasons.
That is, the band gap wavelength in the EA optical modulator becomes longer as approaching the bonding surface as shown in (i) of FIG. 2B when only the butt joint mask 60 is used as described above. effective. Further, in the case of the selective region growth mask, as shown in FIG. 2B (ii), there is an effect that the wavelength becomes shorter as the distance from the selective growth region mask region increases.
By forming EA-DFB using the above pattern mask, the effects of both (i) and (ii) are combined, and as shown in (iii) of FIG. The band gap wavelength can be shortened little by little.
[0019]
  Therefore, in order to achieve the above object, based on the above knowledge, at least two compound semiconductor devices according to the present invention (hereinafter referred to as the first invention) have different configurations on a common substrate. In a compound semiconductor device in which compound semiconductor optical elements are bonded and integrated by a butt bonding method,
  The film thickness of the active layer of the second compound semiconductor optical device that is butt-bonded to the bonding surface of the first compound semiconductor optical device formed on the substrate isDecreases as you move away fromIt is characterized by being minimized and then gradually increasing as the distance from the bonding surface reaches a predetermined film thickness.
[0020]
Another compound semiconductor device according to the present invention (hereinafter referred to as a second invention) is formed by coupling and integrating at least two compound semiconductor optical elements having different configurations on a common substrate by a butt coupling method. In the compound semiconductor device
The band gap wavelength of the active layer of the second compound semiconductor optical device butt-bonded to the coupling surface of the first compound semiconductor optical device formed on the substrate is minimized at the coupling surface and is separated from the coupling surface. It is characterized by gradually increasing and reaching a predetermined band gap.
[0021]
  In addition, a method for manufacturing a compound semiconductor device according to the present invention is a method for manufacturing a compound semiconductor device in which at least two compound semiconductor optical elements having different configurations are coupled and integrated on a common substrate by a butt coupling method. In
  When the layer structure of the second compound semiconductor optical device is butt-bonded to the bonding surface of the first compound semiconductor optical device formed on the substrate,
  Forming a first mask covering the laminated structure of the first compound semiconductor optical device;
  Etching the stacked structure of the first compound semiconductor optical device on the second compound semiconductor optical device formation region using the first mask;
  Forming a selective region growth mask on the second compound semiconductor optical device formation region at a predetermined distance from the first mask, and growing a stacked structure of the second compound semiconductor optical device;
  As a selective area growth mask, separated from each otherOrthogonal to the coupling surfaceTwo masks extending in the direction are formed.
[0022]
  The order of the above steps is not essential, and another method for producing a compound semiconductor device according to the present invention is to combine at least two compound semiconductor optical elements having different configurations on a common substrate by a butt-coupling method. In a method for producing an integrated compound semiconductor device,
  When the layer structure of the second compound semiconductor optical device is butt-bonded to the bonding surface of the first compound semiconductor optical device formed on the substrate,
  A first mask covering the laminated structure of the first compound semiconductor optical device, and a step of forming a selective region growth mask on the second compound semiconductor optical device formation region, separated from the first mask by a predetermined dimension;
  Etching the stacked structure of the first compound semiconductor optical device on the second compound semiconductor optical device formation region using the first mask and the selective region growth mask;
  Growing a laminated structure of the second compound semiconductor optical device;
  As a selective area growth mask, separated from each otherOrthogonal to the coupling surfaceTwo masks extending in the direction are formed.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below specifically and in detail with reference to the accompanying drawings.
Example embodiment
This embodiment is an embodiment of the compound semiconductor device according to the present invention, and the compound semiconductor device described in this embodiment is an EA-DFB laser. FIG. 1 is a cross-sectional view showing a layer structure and a mode field of an EA-DFB laser according to this embodiment, and FIG. 2A is a plan view of the EA-DFB laser according to this embodiment. The cross-sectional view of FIG. 1 shows a cross section taken along line II in FIG.
The EA-DFB laser of the present embodiment has the same configuration as the EA-DFB laser 80 of the prior art, except that the configuration of the EA optical modulator is different from the EA-DFB laser described in the prior art.
As shown in FIG. 1, the EA-DFB laser 10 of the present embodiment includes a GaInAsP-based SI-BH type DFB laser 10A and EA in which a heterojunction structure including a multiple quantum well structure is embedded in a semi-insulating buried layer. A semiconductor optical device composed of an optical modulator 10B, in which a DFB laser 10A and an EA optical modulator 10B are monolithically integrated on a single n-InP substrate 12 coaxially in the waveguide direction. .
[0024]
As shown in FIG. 1, the DFB laser 10A has an n-InP lower clad layer 14 with a film thickness of 100 nm and a band gap wavelength λg of 1 on the DFB laser region of the n-InP substrate 12 common to the EA optical modulator 10B. Etch the SCH-MQW16 with 5 wells made of GaInAsP at .55 μm, the p-InP upper cladding layer 18 with a thickness of 100 nm, and the diffraction grating forming layer 20 with a thickness of 10 nm made of GaInAsP with a band gap wavelength λg of 1.2 μm. And the p-InP upper cladding layer 24 having a thickness of 200 nm including the p-InP cap layer 22 and the p-InP upper cladding layer having a thickness of 2000 nm, which are common to the EA optical modulator 10B. It has a laminated structure of the layer 32 and the p-GaInAs contact layer 34 having a thickness of 300 nm.
[0025]
The upper part of the lower clad layer 14 having the above-described laminated structure, the SCH-MQW 16, the upper clad layer 18, the diffraction grating 20a, the upper clad layer 24 including the p-InP cap layer 22, the upper clad layer 32, and the contact layer 34 are shown in FIG. As shown in FIG. 6B, a mesa structure 46 is formed. Further, both sides of the mesa structure 46 are embedded with a semi-insulating Fe-doped InP layer (hereinafter referred to as an Fe—InP layer) 36 common to the EA optical modulator 10B.
A common passivation film 44 made of a SiN film is formed on the Fe—InP layer 36 on both sides of the mesa structure 46 except for the window 50 on the contact layer 34.
A p-side electrode 38 is formed on the contact layer 34 through a window 50, and a common n-side electrode 42 is formed on the back surface of the common n-InP substrate 12.
[0026]
As shown in FIG. 1, the EA optical modulator 10B has an n-InP buffer layer 26 having a film thickness of 50 nm and a band gap wavelength λg on the EA optical modulator region of the n-InP substrate 12 common to the DFB laser 10A. SCH-MQW28 with 9 wells made of 1.52 μm GaInAsP, 150 nm thick p-InP upper clad layer 30, and 2000 nm thick p-InP upper clad layer 32 and thickness common to DFB laser 10 A, respectively. It has a laminated structure with a 300 nm p-GaInAs contact layer 34.
[0027]
The upper part of the n-InP buffer layer 26, the SCH-MQW 28, the upper cladding layer 30, the upper cladding layer 32, and the contact layer 34 having the above-described stacked structure are formed as a mesa structure 48 along the waveguide direction. Further, both sides of the mesa structure 48 are embedded with a semi-insulating Fe—InP layer 36 common to the DFB laser 10A.
A common passivation film 44 made of a SiN film is formed on the Fe—InP layer 36 on both sides of the mesa structure 48 except for the window 52 on the contact layer 34.
A p-side electrode 40 is formed on the contact layer 34 through a window, and a common n-side electrode 40 is formed on the back surface of the common n-InP substrate 12.
[0028]
The carrier concentration of each layer is 5 × 10 5 in the lower cladding layer 14.¹⁷cm^-35 × 10 5 for the upper cladding layer 24¹⁷cm^-35 × 10 in the buffer layer 26¹⁷cm^-35 × 10 for the upper cladding layer 30¹⁷cm^-31 × 10 for the upper cladding layer 32¹⁸cm^-31 × 10 in the contact layer 38¹⁹cm^-3It is.
[0029]
A method for manufacturing the EA-DFB laser 10 of the above-described embodiment will be described. The EA-DFB laser 10 of this embodiment example is manufactured by the same manufacturing method except that the mask pattern at the time of butt joint growth is different from the mask pattern at the time of butt joint growth of the conventional EA-DFB laser 80. Can do.
3 (a) to 3 (d) are cross-sectional views of respective steps when producing an EA-DFB laser by the production method of the embodiment, and FIG. 4 shows an EA-DFB laser by the production method of this embodiment. The top view of the mask pattern at the time of producing the pad joint at the time of producing is shown.
First, a GaInAsP-based DFB laser structure is formed up to the waveguide layer on the entire surface of the n-InP substrate 12 having the DFB laser region and the EA light modulator region.
That is, the n-InP lower clad layer 14, the SCH-MQW 16, the p-InP upper clad layer 18, the diffraction grating formation layer 20, and the p-InP cap layer 22 are epitaxially grown on the entire surface of the n-InP substrate 12, for example, by MOCVD. Let
Next, as shown in FIG. 3A, the cap layer 22 and the diffraction grating forming layer 20 are etched to form the diffraction grating 20a, and then the p-InP upper cladding layer 24 is epitaxially grown to form the diffraction grating 20a. A laminated structure having the cladding layer 24 is formed on the diffraction grating 20a.
[0030]
Next, as shown in FIG. 3B, the SiN butt joint mask 60 shown in FIG. 4 is formed to cover the stacked structure in the DFB laser region, and is formed in the EA light modulator region 66 exposed from the mask. The laminated structure thus formed is etched to expose the n-InP substrate 12.
Subsequently, a SiN selective region growth mask 62 shown in FIG. 4 is formed on the exposed n-InP substrate 12.
Then, using the butt joint mask 60 and the selective region growth mask 62 as a selective growth mask, the GaInAsP-based EA optical modulator structure is selectively grown on the exposed region on the n-InP substrate 12.
That is, as shown in FIG. 3C, the n-InP buffer layer 26, the SCH-MQW 28, and the p-InP upper cladding layer 30 are epitaxially grown on the exposed region on the n-InP substrate 12 by, for example, MOCVD. Thus, a laminated structure is formed.
[0031]
  next,As shown in FIG.After the butt joint mask 60 is removed, the p-InP upper cladding layer 32 and the p-GaInAs contact layer 34 are epitaxially grown on the entire surface of the substrate except the region of the selective region growth mask 62.
  Next, a stripe-shaped SiN stripe mask 64 having a width of 2 μm shown in FIG. 8B is formed in the vicinity of the center of the two masks constituting the selective region growth mask 62, and each laminated structure of the DFB laser region. And the EA light modulator region are continuously formed on the laminated structure, and then dry etching is performed using them as a mask.
  Thus, in the DFB laser region, the upper portion of the lower clad layer 14, the SCH-MQW 16, the upper clad layer 18, the diffraction grating 20a, the upper clad layer 24 including the p-InP cap layer 22, the upper clad layer 32, and the contact layer A mesa structure 46 composed of 34 is formed.
  On the other hand, in the EA optical modulator region, a mesa structure 48 including the upper part of the n-InP buffer layer 26, the SCH-MQW 28, the p-InP upper clad layer 30, the upper clad layer 32, and the contact layer 34 is formed.
[0032]
Next, after the selective region growth mask 62 is removed, the SiN stripe mask 64 is used as a selective growth mask in each of the DFB laser region and the EA optical modulator region, and a semi-insulating Fe-InP current blocking layer 36 is used. Are buried and both sides of the formed mesa structures 46 and 48 are buried.
Furthermore, by forming the passivation film 44, the p-side electrodes 38 and 40, the n-side electrode 40, and the like, the EA-DFB laser 10 having a configuration in which coupling loss is reduced and light absorption is small can be manufactured. .
[0033]
In this embodiment, an EA-DFB laser is used as an example of the compound semiconductor device according to the present invention. However, the present invention is not limited to this embodiment.
For example, even in other integrated devices in which laser diodes, photodiodes, waveguides, semiconductor optical amplifiers, and the like are integrated, a configuration with reduced coupling loss can be formed by using the present invention.
In addition, regarding the device structure, an example of SI-BH is shown in the present embodiment, but SI-PBH (Semi-Insulating Planar Buried Heterostructure), p / n buried, ridge structure, and the like are combined. Even in a device, the characteristics of the coupling portion can be improved by the concept of the present invention.
Further, regarding the material, GaInAsP is used in the present embodiment, but the present invention can also be applied to, for example, an AlGaAs system, an AlGaInAs system, or a combination thereof.
[0034]
Concrete example
As a specific example of the above-described embodiment, the dimensions of the butt joint mask 60 and the selective region growth mask 62, and the distance between the masks are shown in FIG._DFB300 μm, L_EA130 μm, L_EA2300 μm, W_EA110 μm, W_DFB30 μm, W_EA2Was 10 μm.
[0035]
When the sample of this specific example was fabricated with the above-mentioned dimensions, the device characteristics of the EA-DFB laser were such that a threshold current of 10 mA, an extinction ratio of 21 dB at 3 V bias, and FFP (far field pattern) noise were obtained. There was no.
From the above results, it can be evaluated that the device characteristics of the EA-DFB laser of this embodiment example are improved compared to the EA-DFB laser of the conventional example.
[0036]
In the step of forming the butt joint mask 60, the selective region growth mask 62 is formed at the same time as the butt joint mask 60, and a structure having the same effect can be obtained through the same steps.
That is, the butt joint mask 60 and the selective region growth mask 62 shown in FIG. 4 are formed in the laminated structure shown in FIG. 3A, and only the EA light modulator region 66 exposed from the mask is etched. As shown in FIG. 3B, the n-InP substrate 12 is exposed.
Subsequently, using the butt joint mask 60 and the selective region growth mask 62 as the selective growth mask, the GaInAsP-based EA optical modulator structure is exposed in the exposed region 66 on the n-InP substrate 12 as shown in FIG. Selective growth.
[0037]
【The invention's effect】
According to the present invention, when a butt joint is grown, a selective region growth mask is used in combination with the butt joint mask, thereby reducing coupling loss, having a layer structure with less light absorption, and good device characteristics. The compound semiconductor device which shows is realized.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a layer structure and a mode field of an EA-DFB laser according to an embodiment.
FIG. 2A is a plan view of an EA-DFB laser according to an embodiment, and FIG. 2B shows a band gap wavelength at each position of the EA-DFB laser according to the embodiment. It is a graph to show.
FIGS. 3A to 3D are cross-sectional views of respective steps when an EA-DFB laser is manufactured by the manufacturing method of the embodiment.
FIG. 4 is a plan view showing a mask pattern when a pad joint is manufactured when an EA-DFB laser is manufactured by the manufacturing method of the embodiment.
FIG. 5 is a plan view of a conventional EA-DFB laser.
6 (a) is a cross-sectional view taken along line II-II in FIG. 5, and FIG. 6 (b) is a cross-sectional view taken along line III-III in FIG. (C) is sectional drawing which followed the line IV-IV in FIG.
FIGS. 7A to 7D are cross-sectional views of respective steps when an EA-DFB laser is manufactured by a conventional manufacturing method.
FIGS. 8A and 8B are plan views showing mask patterns when an EA-DFB laser is manufactured by a conventional manufacturing method.
FIG. 9A is a sectional view showing a layer structure and a mode field of a conventional EA-DFB laser in consideration of side growth, and FIG. 9B is a conventional EA-DFB laser. -It is a graph which shows the band gap wavelength in each position of a DFB laser.
[Explanation of symbols]
10 EA-DFB Laser of Embodiment
10A DFB laser
10B EA optical modulator
12 n-InP substrate
14 n-InP lower cladding layer
SCH-MQW made of GaInAsP with 16 λg of 1.55 μm
18 p-InP upper cladding layer
20 Diffraction grating forming layer
20a diffraction grating
22 p-InP cap layer
24 p-InP upper cladding layer
26 n-InP lower cladding layer
28 SCH-MQW made of GaInAsP with λg of 1.50 μm
30 p-InP upper cladding layer
32 p-InP upper cladding layer
34 p-GaInAs contact layer
36 Fe-InP current blocking layer
38 p-side electrode in DFB laser region
40 p-side electrode in EA light modulator region
42 n-side electrode
44 SiN passivation film
46 Mesa structure of DFB laser region
48 Mesa structure of EA optical modulator area
50 DFB laser window
52 EA light modulator window
60 Butt Joint Mask
62 selective area growth mask
64 stripe mask
66 EA light modulator area exposed from mask
70a, 70b, 70c, 72a, 72b, 74a, 74b, 74c Mode field
80 Conventional EA-DFB laser
80A DFB laser region
80B EA optical modulator area

Claims (4)

In a compound semiconductor device in which at least two compound semiconductor optical elements having different configurations are coupled and integrated on a common substrate by a butt coupling method.
The film thickness of the active layer of the second compound semiconductor optical device butt-bonded to the bonding surface of the first compound semiconductor optical device formed on the substrate decreases as the distance from the bonding surface decreases , and then temporarily minimizes. A compound semiconductor device characterized by increasing gradually as the distance from the bonding surface reaches a predetermined film thickness. In a compound semiconductor device in which at least two compound semiconductor optical elements having different configurations are coupled and integrated on a common substrate by a butt coupling method.
The band gap wavelength of the active layer of the second compound semiconductor optical device butt-bonded to the coupling surface of the first compound semiconductor optical device formed on the substrate is minimized at the coupling surface and is separated from the coupling surface. The compound semiconductor device is characterized in that it gradually increases as it reaches a predetermined band gap wavelength. In a method for producing a compound semiconductor device in which at least two compound semiconductor optical elements having different configurations are coupled and integrated on a common substrate by a butt coupling method.
When the layer structure of the second compound semiconductor optical device is butt-bonded to the bonding surface of the first compound semiconductor optical device formed on the substrate,
Forming a first mask covering the laminated structure of the first compound semiconductor optical device;
Etching the stacked structure of the first compound semiconductor optical device on the second compound semiconductor optical device formation region using the first mask;
Forming a selective region growth mask on the second compound semiconductor optical device formation region at a predetermined distance from the first mask, and growing a stacked structure of the second compound semiconductor optical device. A method of manufacturing a compound semiconductor device, comprising forming two masks as region growth masks that are separated from each other and extend in a direction perpendicular to the coupling surface . In a method for producing a compound semiconductor device in which at least two compound semiconductor optical elements having different configurations are coupled and integrated on a common substrate by a butt coupling method.
When the layer structure of the second compound semiconductor optical device is butt-bonded to the bonding surface of the first compound semiconductor optical device formed on the substrate,
A first mask covering the laminated structure of the first compound semiconductor optical device, and a step of forming a selective region growth mask on the second compound semiconductor optical device formation region, separated from the first mask by a predetermined dimension;
Etching the stacked structure of the first compound semiconductor optical device on the second compound semiconductor optical device formation region using the first mask and the selective region growth mask;
Forming a stacked structure of a second compound semiconductor optical device, and forming two masks that are separated from each other and extend in a direction perpendicular to the coupling surface as a selective region growth mask. A method for manufacturing a compound semiconductor device.

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