JP2003152264A - Optical integration device including nitride-based semiconductor laser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical integrated device including a nitride-based semiconductor laser, prevent light absorption by a substrate, and to easily realize integration of various optical components. SOLUTION: The optical integrated device has a multiple quantum well structure active layer formed of a nitride-based III-V compound semiconductor on an insulating substrate 1 provided with an optical waveguide 7 formed of a nitride-based III-V compound semiconductor, and integrates at least a semiconductor laser 2 which emits light in accordance with the transition between sub-bands.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical integrated device equipped with a nitride semiconductor laser, and for example, in an optical integrated platform in which each optical element is integrated on a substrate, each optical element can be easily integrated. The present invention relates to an optical integrated device including a nitride-based semiconductor laser, which is characterized by a structure using intersubband (ISB) transitions, as well as using a nitride-based III-V group compound semiconductor.

[0002]

2. Description of the Related Art Currently, the modulation speed is 1 in the field of optical communication.
It has become faster at 0 G and 40 Gbps, and the number of wavelengths is 100 and even 10 even in wavelength division multiplexing systems.
It is progressing with 00 waves.

The background of this is the increase in the amount of information to be transmitted, including the Internet, and it is difficult to cope with such a situation with the current device configuration due to problems such as the scale of the device and cost, and integration is strongly desired. It is rare.

In the past, many optical communication devices were individual devices, and integration was unsuitable. Therefore, the semiconductor laser, which is a light emitting element, the light receiving element, the modulator, and the like are separately packaged and combined on a board. As a result, the device scale is large, and there is a problem in terms of the device scale particularly when many wavelengths are handled in the wavelength multiplexing system.

On the other hand, in order to cope with such a problem of large-scaled device structure, integration of optical parts has been attempted,
For example, one in which optical components are integrated on a glass substrate (PL
C) and integration using a semiconductor substrate have also been attempted.

[0006]

However, although the PLC is suitable for monolithic integration of passive elements, it becomes a hybrid for integration of active elements, which causes problems such as interface matching. There is a problem that it is not suitable for large-scale integration.

On the other hand, in the case of integration using a semiconductor substrate, in the GaAs / AlGaAs system, since the substrate is the same material as the active region of the active element, light absorption loss due to direct transition occurs, and InGaAsP / InP. In the system, there is a problem that it is difficult to handle because light absorption loss occurs in the cap layer and the refractive index changes during operation.

Therefore, it is an object of the present invention to prevent light absorption in a substrate and facilitate integration of various optical components.

[0009]

FIG. 1 is an explanatory view of the principle configuration of the present invention, and means for solving the problems in the present invention will be described with reference to FIG. In order to achieve the above object, the present invention provides an optical integrated device including a nitride-based semiconductor laser 2, an optical waveguide 7 made of a nitride-based III-V group compound semiconductor, particularly a GaN core layer. And an insulating substrate 1 provided with an optical waveguide 7 composed of an AlGaN cladding layer, particularly an insulating substrate made of a sapphire substrate, a semi-insulating SiC substrate, a semi-insulating GaN substrate, or a semi-insulating AlN substrate. It is characterized in that it has a multiple quantum well structure active layer made of a nitride-based III-V group compound semiconductor on a substrate 1, and at least a semiconductor laser 2 emitting light by transition between subbands is integrated.

As described above, the same nitride waveguide II as the optical waveguide 7 made of a nitride III-V compound semiconductor is used.
By integrating the semiconductor laser 2 made of an IV compound semiconductor, monolithic integration can be facilitated and absorption loss of laser light in the substrate or the cap layer can be eliminated.

In particular, as the semiconductor laser 2, a semiconductor laser 2 utilizing the transition between subbands, that is, ISB (I
The use of an inter-subband laser is suitable for optical communication due to intersubband transition, for example, transition between the second quantum level and the first quantum level 1.3 to 1.
A laser beam having a wavelength of 55 μm band can be used.

Further, since the insulating substrate 1 is used as the substrate, it is possible to prevent the signal from sneaking through the substrate, and thereby each optical element can be driven and controlled completely independently.

Further, the semiconductor optical amplifier 4, the semiconductor photodetector, or the optical modulator 3, for example, the semiconductor optical amplifier 4 using the intersubband transition, the semiconductor photodetector, or
The semiconductor optical modulator 3 may be integrated, and the multimode interference type optical coupling waveguide, that is, MMI (Multi-
By combining with the mode interference 5 and the branch optical waveguide 8, it becomes possible to construct an optical integrated platform for wavelength division multiplexing communication.

As the optical modulator 3, a Mach-Zehnder type optical modulator having an excellent extinction ratio characteristic may be used, and at least a part of the Mach-Zehnder type optical modulator may be used.
A ferroelectric waveguide such as LiNbO ₃ or a polymer waveguide may be used. In this way, by interposing the optical element made of an insulator in a part of the series of optical paths, the insulation separation between the optical elements can be performed more reliably.

Further, the drive circuit 6 for driving the semiconductor laser 2, the semiconductor optical amplifier 4, the semiconductor photodetector, and the optical modulator 3 is integrated on the insulating substrate, and a drive element forming the drive circuit 6 is integrated. Of at least a part of a Schottky barrier field effect transistor (MESFET), a high electron mobility transistor (HEMT), or a heterojunction bipolar transistor (HBT) made of a nitride-based III-V group compound semiconductor. It is desirable to configure with elements, whereby the entire system including the drive circuit 6 can be configured monolithically.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION An optical integrated platform according to an embodiment of the present invention will now be described with reference to FIGS. See FIG. 2. FIG. 2 shows an optical integrated platform according to an embodiment of the present invention.
That is, it is a configuration explanatory view of an optical integrated device in which various optical elements are integrated on an insulating substrate, and D on the sapphire substrate 10.
FB-ISB laser 30, ISB optical modulator 40, ISB
The optical amplifier 50 and the MMI 60 are monolithically integrated, and the optical waveguide 20 is provided between the optical elements. A plurality of branch optical waveguides 61 are provided on the output side of the MMI 60.

Further, the DFB-ISB laser 30, ISB
A laser drive circuit 70, an optical modulator drive circuit 80, and an optical amplifier drive circuit 90 for driving the optical modulator 40 and the ISB optical amplifier 50 are also monolithically integrated.

In this case, the laser light oscillated by the DFB-ISB laser 30 may be directly taken out via the optical waveguide 20 on the left side in the figure, or the ISB optical modulator 40,
The light enters the MMI 60 via the ISB optical amplifier 50, and the MM
In I60, the output may be output to the selected branch waveguide 61.

3A and 3B. FIG. 3A is a longitudinal sectional view of a DFB-ISB laser integrated on the optical integrated platform according to the embodiment of the present invention, and FIG. FIG. 3B) is a cross-sectional view taken along the alternate long and short dash line connecting AA ′ in FIG. First, (000
1) On the sapphire substrate 10 whose main surface is the C surface, an n-type AlGaN cladding layer 31 having a thickness of, for example, 0.5 μm is formed by MOVPE (metal organic chemical vapor deposition). The crystal is grown to form a diffraction grating 32 having a period corresponding to the oscillation wavelength.

Next, after a SiO ₂ mask (not shown) having a rectangular opening is provided, an InGaN / AlGaN MQW active layer 33 consisting of an AlGaN barrier layer and an InGaN well layer having a film thickness not more than the de Broglie wavelength is formed. , For example, after depositing to 0.2 μm,
An n-type AlGaN cladding layer 34 having a thickness of, for example, 0.6 μm is selectively deposited.

Next, Si having a width of 1.0 μm, for example,
After forming a stripe mesa by etching using an O ₂ mask (not shown) as a mask, the i-type AlN buried layer 35 is grown using this SiO ₂ mask as a selective growth mask.

Next, a part of the i-type AlN buried layer 35 is selectively removed by etching to remove the n-type AlGaN cladding layer 3.
1 is exposed and then Ni is deposited to form the Ni electrode 36,
DFB-ISB laser 3 by forming 37
The basic configuration of 0 is completed.

FIG. 3C is an explanatory view of the light emission principle of the above-mentioned DFB-ISB laser, in which the InGaN / AlGaN MQW active layer 33 has an InGaN well layer and an InGaN well layer in the conduction band (E _C ). Al
Quantum levels corresponding to the composition ratio and layer thickness of the GaN layer are formed. In the present invention, only two quantum levels are generated in the quantum well, that is, only the first quantum level 38 that is the ground level and the second quantum level 39 that is the first excitation level, and The composition ratio and the layer thickness of the InGaN well layer and the AlGaN layer are determined so that the energy difference between the two corresponds to 1.3 to 1.55 μm.

When a current is injected into the DFB-ISB laser 30 from the laser driving circuit 70 through the Ni electrodes 36 and 37, the second quantum level 39 changes to the first quantum level 38. Laser light having a wavelength of 1.3 to 1.55 μm is output.

The laser light having a wavelength of 1.3 to 1.55 μm is suitable for optical communication because it has characteristics such as a small optical fiber loss and is not absorbed by the sapphire substrate 10. In addition, the light propagation characteristic does not change due to the change in the refractive index due to the light absorption of the substrate. Note that FIG.
In order to simplify the description and illustration, the n-type Ga
Although the N cap layer is not provided, even if the n-type GaN cap layer is provided, laser light having a wavelength of 1.3 to 1.55 μm is not absorbed by the n-type GaN cap layer.

FIG. 4 is a schematic cross-sectional view of an ISB optical modulator integrated on the optical integrated platform according to the embodiment of the present invention. The ISB optical modulator is formed on the sapphire substrate 10 by using the MOVPE method. But,
For example, a 0.5 μm n-type AlGaN cladding layer 41 is grown.

Next, an SiO ₂ mask (not shown) having a rectangular opening was provided, and then an InGaN / AlGaN MQW active layer 42 consisting of an AlGaN barrier layer and an InGaN well layer having a film thickness not larger than the de Broglie wavelength was deposited. After that, for example, n-type AlGa having a thickness of 0.6 μm
The N cladding layer 43 is selectively deposited.

In this case, the rectangular opening provided in the SiO ₂ mask is the SiO used in the DFB-ISB laser.
_{2 By} making the width wider than the rectangular opening provided in the mask, the InGaN well layer and the AlGaN barrier layer become thinner than the film thickness in the above DFB-ISB laser,
Therefore, since the energy difference between the second quantum level and the first quantum level becomes large, the InGaN / AlGaN MQW
There is no light absorption loss in the active layer 42. However, the film thickness of the InGaN / AlGaN MQW active layer 42 in this case is, when formed simultaneously with the DFB-ISB laser,
It becomes thinner than 0.2 μm.

Then, as in the case of the DFB-ISB laser described above, etching is performed using a SiO ₂ mask (not shown) having a width of, for example, 1.0 μm as a mask to form stripe mesas, and then this SiO is formed. _{2 The} i-type AlN buried layer 44 is grown using the mask as a selective growth mask.

Next, a part of the i-type AlN buried layer 44 is selectively removed by etching to remove the n-type AlGaN cladding layer 4.
1 is exposed and then Ni is deposited to form the Ni electrode 4
ISB optical modulator 40 by forming 5, 46
The basic configuration of is completed.

FIG. 5 is a schematic cross-sectional view of an ISB optical amplifier integrated on the optical integrated platform according to the embodiment of the present invention, which has a thickness of sapphire substrate 10 formed by the MOVPE method. ,
For example, a 0.5 μm n-type AlGaN cladding layer 51 is grown.

Next, after a SiO ₂ mask (not shown) having a rectangular opening is provided, an InGaN / AlGaN MQW active layer 52 consisting of an AlGaN barrier layer and an InGaN well layer having a film thickness not more than the de Broglie wavelength is formed. , For example, after depositing to 0.2 μm,
An n-type AlGaN cladding layer 53 having a thickness of, for example, 0.6 μm is selectively deposited.

In this case, the rectangular opening provided in the SiO ₂ mask is formed of SiO used in the above DFB-ISB laser.
_{By making the} size of the rectangular opening provided in the _two masks, the InGaN well layer and the AlGaN barrier layer have the same film thickness as the above DFB-ISB laser, and therefore, the second quantum level-the first quantum level. The energy difference between the levels becomes the same as that of the DFB-ISB laser, which enables optical amplification.

Then, as in the case of the DFB-ISB laser described above, etching is performed using a SiO ₂ mask (not shown) having a width of, for example, 1.0 μm as a mask to form a stripe mesa, and then this SiO is formed. _{2 The} i-type AlN buried layer 54 is grown using the mask as a selective growth mask.

Then, a part of the i-type AlN buried layer 54 is selectively removed by etching to remove the n-type AlGaN cladding layer 5.
1 is exposed and then Ni is deposited to form the Ni electrode 5
ISB optical amplifier 50 by forming 5, 56
The basic configuration of is completed. In this ISB optical amplifier 50, a current is passed through the InGaN / AlGaN MQW active layer 52 to the extent that laser oscillation does not occur, and InGaN / Al
The laser light incident on the GaN MQW active layer 52 is amplified.

See FIG. 6. FIG. 6 is a schematic cross-sectional view of a HEMT that constitutes a drive circuit integrated in the optical integrated platform according to the embodiment of the present invention. First, the sapphire substrate 10 having the C-plane as the main surface is first described. On top, using the MOVPE method, i-type GaN with a thickness of 3 μm
Electron transit layer 71, i-type Al _0.25 Ga _{0.75 with} a thickness of 3 nm
N layer 72, thickness 25 nm, Si doping concentration 2
× 10 ¹⁸ cm ^-3 n-type Al _0.25 Ga _0.75 N electron supply layer 7
3 and an i-type Al _0.25 Ga _0.75 N protective layer 74 having a thickness of 5 nm are sequentially deposited.

Then, a SiN film 75 having a thickness of 20 nm is deposited on the entire surface by the CVD method, and then an opening is provided in the gate formation region to form a gate electrode 76 made of Ni / Au.
And the source / drain contact regions are provided with openings to form the source / drain electrodes 77 of Ti / Au, the basic structure of the HEMT is completed.

The electron mobility of the two-dimensional electron gas layer in the i-type GaN electron transit layer 71 is 1000 to 1500.
Although it is about cm ² / V · sec, the concentration of the two-dimensional electron gas is about 1 × 10 ¹³ cm ^-2 , which is one or more orders of magnitude higher than the concentration of the two-dimensional electron gas of the GaAs system.
It is possible to obtain a current driving characteristic similar to that of T and to obtain a high withstand voltage characteristic because the forbidden band width is wide.

FIG. 7 is a schematic cross-sectional view of an optical waveguide used in the optical integrated platform according to the embodiment of the present invention. First, the MOVPE method is applied to the sapphire substrate 10 having the C-plane as the main surface. The n-type AlGaN cladding layer 21 having a thickness of, for example, 0.5 μm is grown by using this. The thickness is then, for example,
An i-type GaN core layer 22 having a thickness of 0.2 μm and an i-type AlN cladding layer 23 having a thickness of, for example, 0.6 μm are sequentially deposited on the entire surface.

Then, as in the case of the DFB-ISB laser described above, etching is performed using a SiO ₂ mask (not shown) having a width of, for example, 1.0 μm as a mask to form a stripe mesa, and then this SiO is formed. _{2 The} i-type AlN buried layer 24 is grown using the mask as a selective growth mask.

As described above, the optical device described with reference to FIGS. 3 to 5, the HEMT described with reference to FIG. 6, and
By combining the optical waveguides described in FIG. 7, the optical integrated platform shown in FIG. 2 can be obtained. In this case, in order to simplify the manufacturing process, it is desirable to make part of the process common, but since the HEMT has a different specific configuration, it is desirable to selectively grow the HEMT last.

That is, the n-type AlGaN cladding layer 21 and
The n-type AlGaN clad layer 31, the n-type AlGaN clad layer 41, and the n-type AlGaN clad layer 51 are commonly used,
DFB of this common n-type AlGaN cladding layer 21
-The diffraction grating 32 is selectively formed only in the ISB laser forming portion.

Next, the DFB-ISB laser 30, IS
A SiO ₂ mask having a rectangular opening corresponding to a region where the B optical modulator 40 and the ISB optical amplifier 50 are formed is provided, and the InGaN / AlGaN MQW layer is formed on the DFB-
In the ISB laser section, the thickness is, for example, 0.2 μm.
To be deposited. In this case, as described above, D
In the FB-ISB laser section and the ISB optical amplifier section, the sizes of the rectangular openings are made the same, and the sizes of the rectangular openings of the ISB optical modulator section are made wider.

Next, the thickness of n is 0.6 μm, for example.
-Type AlGaN clad layer 34, n-type AlGaN clad layer 43, and n-type AlGaN clad layer 53 are simultaneously deposited, the SiO ₂ mask is removed, and then a new DFB-ISB laser 30 and ISB optical modulator Four
A SiO ₂ mask having a length corresponding to each element length is formed in the area where 0 and the ISB optical amplifier 50 are formed, and the exposed portion is removed by etching.

Next, using this SiO ₂ mask as a selective growth mask, the i-type GaN core layer 22 having a thickness of, for example, 0.2 μm and the i-type GaN core layer 22 having a thickness of, for example, 0.6 μm are used.
The type AlN cladding layer 23 is sequentially deposited.

Next, after removing the SiO ₂ mask used for the selective growth, a new SiO ₂ film is deposited on the entire surface,
One striped pattern that reaches MMI60, MM
Forming a SiO ₂ pattern having a pattern corresponding to I60 and a pattern corresponding to the branched optical waveguide 61,
By etching using this SiO ₂ pattern as a mask, a stripe mesa or the like is formed.

Next, using this SiO ₂ pattern as a selective growth mask, the i-type AlN burying layer 24 and the i-type AlN are formed.
Buried layer 35, i-type AlN buried layer 44, and i-type AlN
The buried layer 54 is formed. That is, the i-type AlN buried layer 35,
i-type AlN buried layer 44 and i-type AlN buried layer 54
Is a layer common to the i-type AlN buried layer 24.

Next, one side of the i-type AlN burying layer 24 is selectively removed to form an electrode formation region on the substrate side, and the laser drive circuit 70, the optical modulator drive circuit 80, and The optical amplifier 90 may be selectively formed, and each electrode may be finally formed.

As described above, in the present invention, since the nitride-based III-V group compound semiconductor is used and each optical element is an optical element utilizing the intersubband transition, the entire structure including the drive circuit is It can be configured monolithically, and can modulate, amplify, and propagate laser light having a width of 1.3 to 1.55 μm suitable for optical communication without absorption loss.

Further, in the present invention, since the sapphire substrate 10 having a high insulation property is used as the substrate, all the elements can be driven independently of each other without electric signals sneaking through the substrate. It will be possible.

Although not shown in the above embodiment, semiconductor light receiving elements may be integrated if necessary, and the structure is exactly the same as that of the ISB optical amplifier shown in FIG. The configuration is good, and when laser light is introduced into the semiconductor light receiving element in the state where no current flows, a current flows according to the output of the input light, and an optical signal can be converted into an electrical signal by detecting this current. it can.

Next, modified examples of the optical element and the optical waveguide used in the embodiment of the present invention will be described with reference to FIGS. Reference is made to FIGS. 8A and 8B. FIG. 8A is a vertical cross-sectional view of a modified example of the semiconductor laser integrated on the optical integrated platform according to the embodiment of the present invention, and FIG. Is a cross-sectional view taken along the alternate long and short dash line connecting AA ′ in FIG.
It becomes a DBR-ISB laser.

First, the sapphire substrate 1 whose main surface is the C surface
0 using the MOVPE method, the thickness is, for example, 0.
A 5 μm n-type AlGaN cladding layer 31 is grown to form the diffraction grating 12 having a period corresponding to the oscillation wavelength on both sides in the optical axis direction of the laser.

Next, after a SiO ₂ mask (not shown) having a rectangular opening is provided, the InGaN / AlGaN MQW active layer 33 consisting of an AlGaN barrier layer and an InGaN well layer having a film thickness not more than the de Broglie wavelength is formed. , For example, after depositing to 0.2 μm,
An n-type AlGaN cladding layer 34 having a thickness of, for example, 0.6 μm is selectively deposited.

Next, Si having a width of, for example, 1.0 μm is used.
After forming a stripe mesa by etching using an O ₂ mask (not shown) as a mask, the i-type AlN buried layer 35 is grown using this SiO ₂ mask as a selective growth mask.

Then, a part of the i-type AlN buried layer 35 is selectively removed by etching to remove the n-type AlGaN cladding layer 3.
1 is exposed and then Ni is deposited to form the Ni electrode 36,
By forming 37, the basic structure of the DBR-ISB laser is completed.

Also in this case, in the case where the optical elements are commonly used, the SiO 2 has such a length that the diffraction grating 12 is exposed when the optical elements are etched so that the light input / output end sides are aligned. You can use ₂ masks.

Reference is made to FIG. 9A. FIG. 9A is a schematic sectional view of a modification of the optical waveguide used in the optical integrated platform according to the embodiment of the present invention.
In this case, it is a rib-loaded optical waveguide. First, an i-type AlN cladding layer 13 having a thickness of, for example, 0.5 μm, and an i-type AlN clad layer 13 having a thickness of, for example, 0.2 μm are formed on the sapphire substrate 10 having the C-plane as a main surface by using the MOVPE method. GaN
The core layer 14 and the i-type AlN cladding layer 15 having a thickness of, for example, 0.6 nm are sequentially deposited.

Next, a rib-loaded optical waveguide is completed by forming a stripe-shaped mesa having a width of 3.3 μm and a height of 0.3 μm in the central portion. When such a rib-loaded optical waveguide is used, it is necessary to form each optical element up to the buried layer and then form the i-type GaN core layer or more of the optical waveguide.

FIG. 9B is a schematic sectional view of another modification of the optical waveguide used in the optical integrated platform according to the embodiment of the present invention. In this case, selective growth is performed. It was produced using the method. First, an SiO ₂ pattern having a stripe-shaped opening is formed on a sapphire substrate 10 having a C-plane as a main surface, and this SiO ₂ pattern is used as a selective growth mask to form M.
Using the OVPE method, the thickness is, for example, 0.5 μm
-Type AlN clad layer 17, the thickness is, for example, 0.2 μm
I-type GaN core layer 18 having a thickness of 0.
A 6 nm i-type AlN cladding layer 19 is sequentially deposited.

10A and 10B. FIG. 10A is a schematic view of a Mach-Zehnder type optical modulator which is a modification of the optical modulator integrated on the optical integrated platform according to the embodiment of the present invention. 10B is a perspective view of an essential part, and FIG. 10B is an LN optical modulation element 82 in FIG. 10A.
It is a schematic cross-sectional view of the formation part of.

First, the sapphire substrate 1 whose main surface is the C surface
0, using a sputtering method, the thickness is
0.5 μm SiO ₂ film, 0.2 μm LiNbO
After sequentially depositing _three films and a SiO ₂ film of 0.6 μm, patterning is performed in the shape shown in the figure to form an optical waveguide 81 including a SiO ₂ clad layer 85 / LiNbO ₃ core layer 86 / SiO ₂ clad layer 87. Form.

Next, a Cr film and an Au film are selectively deposited in order on the portion where the LN optical modulator 82 for giving a phase difference is formed, and a pair of electrodes 88 for applying an electric field to the LiNbO ₃ core layer 86. , 89, the basic structure of the Mach-Zehnder type optical modulator is completed.
Reference numerals 83 and 84 are optical amplifiers formed in the removed portion of the optical waveguide 81 after the optical waveguide 81 is formed, and have the same configuration as the ISB optical amplifier shown in FIG.

In this Mach-Zehnder type optical modulator, a voltage is applied to the LN optical modulation element 82 via the electrodes 88 and 89 to change the refractive index in the portion, thereby giving a phase difference to the laser light. As a result, an optical signal corresponding to the change in this voltage can be obtained at the output side. Incidentally, the output becomes 0 when the phase difference is π, and the output becomes 1 when the phase difference is 0 or 2π.

Further, by incorporating the optical modulation element made of such an insulating member into the optical waveguide in the optical integrated platform, the optical elements can be completely electrically separated from each other and crosstalk can be prevented. be able to.

Although the embodiments and modifications of the present invention have been described above, the present invention is not limited to the numerical values, conditions, etc. described in the embodiments and modifications, and various changes can be made. . For example, although the sapphire substrate is used as the substrate in the above-described embodiments, it is not limited to the sapphire substrate, and a semi-insulating SiC substrate, a semi-insulating GaN substrate, or a semi-insulating AlN substrate is used. It is also good.

[0067] Further, in the above embodiment, it is provided with the electrode directly in the n-type AlGaN clad layer, n ⁺
May be provided with an electrode through type GaN layer, in which case the lower n through n ⁺ -type GaN contact layer on a substrate
-Type AlGaN clad layer is provided and the upper n-type A
An n ⁺ -type GaN cap layer may be provided on the lGaN clad layer, and when the i-type AlN buried layer is etched to form the substrate-side electrode, the lower n-type AlGaN clad layer may also be etched. .

Further, in the above embodiment, the clad layer is the AlGaN layer, but the AlN layer or A
An l (Ga) N / (Al) GaN superlattice layer may be used, and the InGaN / AlGaN MQW layer may be GaN.
A / AlGaN MQW structure or a GaN / AlNM MQW structure may be used.

Further, the combination of the optical elements to be integrated on the optical integrated platform is not limited to the combination shown in FIG. 2, and the required optical elements may be appropriately combined depending on the usage form and purpose. .

For example, in the above embodiment, only one semiconductor laser is shown, but a plurality of DFB-ISB lasers having mutually different oscillation wavelengths are provided in parallel and the MMI is provided.
It may be configured to output from one optical waveguide via the optical waveguide, and thereby a light source for wavelength division multiplexing can be configured.

In order to make the oscillation wavelengths of the DFB-ISB lasers different from each other, the period of each diffraction grating is changed, and the SiO ₂ at the time of depositing the MQW layer is changed.
The sizes of the rectangular openings provided in the mask may be different from each other so that the film thickness of the well layer may be different.

Further, in the modification of the above embodiment, the Mach-Zehnder interferometer type optical modulator is formed by using LiNbO ₃ , but the present invention is not limited to such a ferroelectric member, and it is not limited to such a ferroelectric member. polymi
de, oxynitrostilbenzene-based "MONS" -polymer, aminonitrostilbenzene-based "DANS"-
Polymers such as polymers may also be used.

In the Mach-Zehnder interferometer type optical modulator, the pair of electrodes 8 is applied so that an electric field is applied from the lateral direction.
8 and 89 are provided, the SiO ₂ clad layer 87 and the sapphire substrate 1 are provided as in the ISB optical modulator shown in FIG.
It is also possible to provide electrodes on each of the electrodes and apply an electric field between these electrodes.

Further, in the above description of the embodiment, the HEMT is used as the drive element constituting the drive circuit for driving each optical element, but the HEMT is not limited to the HEMT, and for example, a nitride type III- MESFET (Schottky barrier type FET) made of Group V compound semiconductor
Alternatively, H composed of a nitride III-V compound semiconductor
You may comprise by BT (heterojunction bipolar transistor).

Further, in the above embodiment, the drive circuit is also integrated in order to make the whole compact, but the drive circuit does not necessarily have to be integrated. In this case, the drive element is used. Need not be a nitride III-V compound semiconductor.

Further, the application is not limited to long-distance optical communication, but is also suitable as a signal transmission system between various information processing terminals, and when not used for long-distance optical communication. Has a good compatibility with the optical fiber.
It does not have to be in the band of 3 to 1.55 μm, and laser light in other wavelength ranges may be used.

Here, the characteristic points of the present invention will be described again with reference to FIG. See FIG. 1 (Appendix 1) A multiple quantum well structure active layer made of a nitride-based III-V compound semiconductor is provided on an insulating substrate 1 provided with an optical waveguide 7 made of a nitride-based III-V compound semiconductor. An optical integrated device including a nitride semiconductor laser 2 in which at least the semiconductor laser 2 that emits light by transition between subbands is integrated. (Supplementary Note 2) The nitride system according to Supplementary Note 1, wherein the insulating substrate 1 is a sapphire substrate, a semi-insulating SiC substrate, a semi-insulating GaN substrate, or a semi-insulating AlN substrate. An optical integrated device including a semiconductor laser 2. (Supplementary Note 3) The optical waveguide 7 includes a GaN core layer and Al.
3. An optical integrated device comprising a nitride semiconductor laser 2 according to appendix 1 or 2, which is composed of an _x Ga _1-x N cladding layer (0 <x ≦ 1). (Additional remark 4) At least one type of optical element among the semiconductor optical amplifier 4, the semiconductor photodetector, and the optical modulator 3 is integrated on the above-mentioned insulating substrate.
An optical integrated device comprising the nitride semiconductor laser 2 described in any one of 1. (Supplementary Note 5) The semiconductor optical amplifier 4, the semiconductor photodetector,
And at least one type of optical element in the optical modulator 3,
An optical integrated device comprising the nitride semiconductor laser 2 according to appendix 4, which is an optical element utilizing intersubband transition. (Additional remark 6) The optical modulator 3 is a Mach-Zehnder interferometer type optical modulator 3, and an optical integrated device comprising the nitride semiconductor laser 2 according to the additional remark 4. (Additional remark 7) At least a part of the Mach-Zehnder interferometer type optical modulator 3 is composed of either a ferroelectric waveguide or a polymer waveguide, and the nitride semiconductor laser 2 according to additional remark 6 is characterized. An optical integrated device equipped with. (Supplementary Note 8) The semiconductor laser 2, the semiconductor optical amplifier 4,
A semiconductor photodetector and a drive circuit 6 for driving at least one type of optical element in the optical modulator 3 are integrated on the insulating substrate, and at least a part of the drive elements constituting the drive circuit 6 is integrated. 9. An optical integrated device comprising a nitride semiconductor laser 2 according to any one of appendices 1 to 7, characterized in that is composed of a nitride III-V compound semiconductor. (Supplementary Note 9) The supplementary note 1 to 7, wherein the driving element is any one of a Schottky barrier field effect transistor, a high electron mobility transistor, and a heterojunction bipolar transistor. An optical integrated device including a nitride semiconductor laser 2.

[0078]

According to the present invention, the nitride III-V
An optical integrated platform that includes a semiconductor laser that uses transitions between subbands using group compound semiconductors is configured monolithically, facilitating integration of optical devices and suppressing fluctuations in characteristics due to absorption of light. Therefore, it contributes to the practical application and spread of large-capacity optical communication.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a principle configuration of the present invention.

FIG. 2 is a configuration explanatory view of an optical integrated platform according to the embodiment of the present invention.

FIG. 3 is an explanatory diagram of a DFB-ISB laser integrated on the optical integrated platform according to the embodiment of the present invention.

FIG. 4 is a schematic cross-sectional view of an ISB optical modulator integrated on the optical integrated platform according to the embodiment of the present invention.

FIG. 5 is a schematic cross-sectional view of an ISB optical amplifier integrated in the optical integrated platform according to the embodiment of the present invention.

FIG. 6 is a schematic cross-sectional view of a HEMT that constitutes a drive circuit integrated in the optical integrated platform according to the embodiment of the present invention.

FIG. 7 is a schematic cross-sectional view of an optical waveguide used in the optical integrated platform according to the embodiment of the present invention.

FIG. 8 is an explanatory diagram of a modified example of a semiconductor laser integrated on the optical integrated platform according to the embodiment of the present invention.

FIG. 9 is a schematic cross-sectional view of a modification of the optical waveguide used in the optical integrated platform according to the embodiment of the present invention.

FIG. 10 is a structural explanatory view of a modified example of the optical modulator integrated in the optical integrated platform according to the embodiment of the present invention.

[Explanation of symbols]

1 Insulating Substrate 2 Semiconductor Laser 3 Optical Modulator 4 Semiconductor Optical Amplifier 5 MMI 6 Drive Circuit 7 Optical Waveguide 8 Branching Optical Waveguide 10 Sapphire Substrate 11 Bonding Wire 12 Diffraction Grating 13 i-type AlN Clad Layer 14 i-type GaN Core Layer 15 i Type AlN clad layer 16 SiO ₂ mask 17 i type AlN clad layer 18 i type GaN core layer 19 i type AlN clad layer 20 optical waveguide 21 n type AlGaN clad layer 22 i type GaN core layer 23 i type AlN clad layer 24 i type AlN buried layer 30 DFB-ISB laser 31 n-type AlGaN clad layer 32 diffraction grating 33 InGaN / AlGaN MQW active layer 34 n-type AlGaN clad layer 35 i-type AlN buried layer 36 Ni electrode 37 Ni electrode 38 first quantum level 39 Second quantum level 40 ISB optical modulator 41 n-type AlG N clad layer 42 InGaN / AlGaN MQW active layer 43 n-type AlGaN clad layer 44 i-type AlN buried layer 45 Ni electrode 46 Ni electrode 50 ISB optical amplifier 51 n-type AlGaN clad layer 52 InGaN / AlGaN MQW active layer 53 n-type AlGaN clad layer 54 i-type AlN buried layer 55 Ni electrode 56 Ni electrode 60 MMI 61 Branched optical waveguide 70 Laser drive circuit 71 i-type GaN electron transit layer 72 i-type Al _0.25 Ga _0.75 N layer 73 n-type Al _0.25 Ga _0.75 N electron supply layer 74 i-type Al _0.25 Ga _0.75 N protective layer 75 SiN film 76 Gate electrode 77 Source / drain electrode 80 Optical modulator drive circuit 81 Optical waveguide 82 LN optical modulator 83 Optical amplifier 84 Optical amplifier 85 SiO ₂ clad layer 86 LiNbO ₃ core Layer 87 SiO ₂ clad layer 88 electrode 89 Polar 90 optical amplifier drive circuit

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Gen Imai             4-1, Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa             No. 1 within Fujitsu Limited (72) Inventor Katsumi Kishino             1782 Sobana, Akiruno-shi, Tokyo (72) Inventor Ken Ozeki             2-443-26 Amanumacho, Saitama City, Saitama Prefecture F-term (reference) 2H079 BA01 BA03 CA05 DA03 DA16                       DA22 EA03 EA05                 5F073 AA22 AA64 AA65 AA74 AB13                       AB14 AB21 AB25 CA07 CB05                       DA05

Claims (5)

[Claims] 1. A subband having a multiple quantum well structure active layer made of a nitride III-V compound semiconductor on an insulating substrate provided with an optical waveguide made of a nitride III-V compound semiconductor. An optical integrated device comprising a nitride semiconductor laser, wherein at least a semiconductor laser that emits light due to transitions between them is integrated. 2. The nitride according to claim 1, wherein the insulating substrate is a sapphire substrate, a semi-insulating SiC substrate, a semi-insulating GaN substrate, or a semi-insulating AlN substrate. Optical integrated device equipped with a semiconductor laser. 3. The semiconductor optical amplifier, the semiconductor photodetector, and at least one type of optical element of an optical modulator are integrated on the insulating substrate. Optical integrated device equipped with the above-mentioned nitride semiconductor laser. 4. An optical integrated device equipped with a nitride semiconductor laser according to claim 3, wherein the optical modulator is a Mach-Zehnder type optical modulator. 5. A drive circuit for driving at least one type of optical element of the semiconductor laser, the semiconductor optical amplifier, the semiconductor photodetector, and the optical modulator is integrated on the insulating substrate, and the drive circuit is integrated. 5. A light provided with a nitride semiconductor laser according to any one of claims 1 to 4, wherein at least a part of a driving element constituting the circuit is composed of a nitride III-V group compound semiconductor. Accumulation device.