JP2003234533A - Semiconductor optical integrated element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor optical integrated element and a method of manufacturing the same wherein a drop in optical intensity resulting from stray beam within a window portion and a drop in optical coupling efficiency with an optical fiber can be prevented. <P>SOLUTION: In an optical radiating unit 40, an optical absorbing layer 41 is provided to the side surface of an window 44 and a second clad layer 16 and the upper surface of the second clad layer 16. The optical absorbing layer 41 includes a semiconductor in the photoluminescence wavelength which is longer than the wavelength of the light from the active layer 13 of an optical device 10. Therefore, the light beam L<SB>1</SB>progressing radially in the window portion 44 is absorbed with the light absorbing layer 41 when the beam reaches the light absorbing layer 41. The light L<SB>2</SB>reflected at the interface between the window portion 44 and a reflection preventing film 45 also reaches the optical absorbing layer 41 and is then absorbed with the light absorbing layer 41. Therefore, the light L<SB>1</SB>does not stay in the window portion 44 and therefore stray beam in the window portion 44 can be lowered. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a semiconductor optical integrated device and a method for manufacturing the same.

[0002]

2. Description of the Related Art Semiconductor laser diodes (Semiconductor
Laser diode (LD) and electro-absorption optical modulator (Electr
Semiconductor optical integrated devices in which an oabsorption modulator (hereinafter, EA modulator) is integrated are being used in an optical communication system. In such a semiconductor optical integrated device, the semiconductor laser diode is driven by direct current, and the laser light emitted from the LD is modulated at high speed by the EA modulator.

[0003]

In the above-described semiconductor optical integrated device, when light is reflected by the light emitting end face of the EA modulator and returns to the EA modulator and the LD, a so-called wavelength chirping phenomenon occurs. When this phenomenon occurs, the distance over which an optical signal can be transmitted in the optical communication system becomes short.

A semiconductor optical integrated device having a window portion on the light emitting end face has been developed in order to prevent reflection at the light emitting end face of the EA modulator. However, as a result of studies by the present inventors, it was found that the semiconductor optical integrated device having the window has the following problems. In a semiconductor optical integrated device provided with a window portion, most of the laser light travels straight along the extending direction of the optical waveguide, but since the optical waveguide structure is not provided in the window portion, the laser light is radial. Will be spread over. Therefore, the returning light is reduced, but the light that spreads radially becomes stray light that remains in the window without being transmitted through the window and being emitted to the outside. Then, an interaction occurs between the stray light and the laser light that travels straight through the window portion, so that the optical output intensity from the semiconductor optical integrated device decreases. Further, due to this interaction, the radiation pattern of the light emitted from the light emitting end face becomes a multimodal radiation pattern in which a plurality of side lobes occur. Therefore, the optical coupling efficiency between the semiconductor optical integrated device and the optical fiber is significantly reduced.

In order to solve such a problem, a semiconductor optical integrated device has been developed in which the width or thickness of the window portion is changed in a taper shape according to the spread angle of light (Japanese Patent Laid-Open No. 10-27).
5960 publication). However, in such a semiconductor optical integrated device, since the window portion is tapered, the capacitance of the device is increased. As the capacitance increases, the high speed operation characteristics of the device deteriorate. Further, when manufacturing this semiconductor optical integrated device, a process of processing the window portion into a tapered shape is required, which increases the manufacturing cost.

Therefore, an object of the present invention is to provide a semiconductor optical integrated device and a method for manufacturing the same in which a decrease in light intensity due to stray light in the window and a decrease in optical coupling efficiency with an optical fiber are suppressed. To do.

[0007]

In a semiconductor optical integrated device according to the present invention, (1) a semiconductor light emitting device portion that emits light, (2) a first surface on which light is incident, and the incident light is emitted. A window having a second surface and a semiconductor portion provided between the first and second surfaces; and (3) provided on the window, where the wavelength of the photoluminescent light is greater than the wavelength of the light. A light-absorbing layer containing a long first semiconductor.

In the above structure, the light absorption layer is provided on the window portion. The light absorption layer includes a first semiconductor in which the wavelength of photoluminescence light is longer than the wavelength of light from the semiconductor light emitting element section. Therefore, the light that spreads radially in the window portion is absorbed by the light absorption layer when reaching the light absorption layer.
Therefore, stray light in the window portion is reduced, and as a result, a decrease in light intensity and a decrease in optical coupling efficiency with the optical fiber due to the stray light are suppressed.

The light absorption layer is preferably provided on at least one of the upper surface and the side surface of the window portion. By doing this, the light that spreads radially in the window is
It is reliably absorbed by the light absorbing layer, and stray light in the window is reduced.

The semiconductor optical integrated device described above modulates the light from the semiconductor light emitting device portion, and the modulated light is the first light.
Further includes a semiconductor modulation element portion provided so as to be incident on the surface. With this configuration, the light from the semiconductor light emitting element section can be modulated by the semiconductor modulation element section without modulating the injection current to the semiconductor light emitting element section. Further, according to the knowledge of the present inventors, the semiconductor optical integrated device including the semiconductor modulation element portion is strongly affected by the stray light of the window portion, but in the above configuration, stray light is generated by the light absorption layer provided on the window portion. Since it is absorbed, its effect is reduced.

The semiconductor light emitting element section has a first contact layer and a first electrode provided on the first contact layer, and the semiconductor modulation element section has a second contact layer. And a second electrode provided on the second contact layer, and the first and second contact layers preferably include the first semiconductor. The wavelength of the photoluminescence light of the first semiconductor is longer than the wavelength of the light from the semiconductor light emitting element section. Therefore, the first semiconductor can have an energy band gap smaller than that of various semiconductors forming the semiconductor light emitting element section and the semiconductor modulation element section. The carrier concentration of such a semiconductor can be easily increased to such an extent that ohmic contact between the first and second electrodes is improved. Further, since the first and second contact layers include the first semiconductor as well as the light absorption layer, the first to second semiconductor layers including the first semiconductor formed for the light absorption layer are changed to the first to second contact layers.
And a second contact layer can be made. That is, the first and second contact layers and the light absorption layer can be formed without increasing the number of manufacturing steps.

The semiconductor optical integrated device may have a semiconductor film made of a second semiconductor capable of transmitting the light, between the light absorption layer and the window. Even with this configuration, the light that spreads radially in the window portion can reach the light absorption layer and be absorbed by the light absorption layer.

The semiconductor light emitting element portion is Ga_xIn_1-xAs_yP
_1-y(0 <x <1, 0 <y <1) Having an active layer containing a semiconductor
However, the window portion includes an InP semiconductor, and the light absorption layer is Ga._xIn
_1-xAs _yP_1-y(0 <x <1, 0 <y ≦ 1) including semiconductor
And preferred. With such a configuration, the Ga composition ratio x and
If the As composition ratio y is adjusted, the light from the active layer is absorbed by the light absorption layer.
The above semiconductor optical integrated device is realized because it is absorbed by
To be done.

Further, it is preferable that the semiconductor optical integrated device further includes an antireflection film provided on the second surface. If the antireflection film is provided on the second surface of the window portion, the light from the semiconductor light emitting element portion can be efficiently emitted to the outside through the window portion. Therefore, the returning light to the semiconductor light emitting element section is reduced and the stray light is also reduced. Further, the reflectance of this antireflection film is more preferably 1% or less.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of a semiconductor optical integrated device according to the present invention will be described below with reference to the drawings. In the description of the drawings, the same elements will be denoted by the same reference symbols, without redundant description. Further, the present invention can be implemented for a semiconductor optical integrated device including a semiconductor light emitting device portion and a window portion, but in the present embodiment, an EA modulation type semiconductor optical integrated device will be described.

(First Embodiment) FIG. 1A is a sectional view showing an embodiment of a semiconductor optical integrated device according to the present invention. The figure also shows an example of electrical wiring when the semiconductor integrated device is used. In addition, FIG.
It is sectional drawing which follows the II line in (a). Referring to FIG. 1A, the semiconductor optical integrated device 1 includes an n-type InP substrate 2
Including a plurality of semiconductor layers formed on the substrate 2. The semiconductor optical integrated device 1 includes a light emitting device unit 10,
Modulation device unit 20, separation unit 30, and light emission unit 40
Have. The separation unit 30 is provided between the light emitting device unit 10 and the modulation device unit 20, and the separation unit 30 electrically separates these two device units 10 and 20. Further, the light emitting unit 40 is adjacent to the modulation device unit 20 on the side opposite to the separation unit 30 of the modulation device unit 20.

The light emitting device section 10 comprises a cladding layer 11,
It has a light guide layer 12, an active layer 13, a light guide layer 14, and a first cladding layer 15. These layers 11-15
Are provided on the substrate 2. The active layer 14 is provided between the optical guide layers 12 and 14, and these layers 12 to 14 are provided between the cladding layer 11 and the first cladding layer 15. A diffraction grating 14a is formed at the interface between the light guide layer 14 and the first cladding layer 15.
The modulation device unit 20 also includes a clad layer 21, a light guide layer 22, an active layer 23, a light guide layer 24, a first clad layer 25, and a second clad layer 26. These layers 21 to 25 are provided on the substrate 2. Active layer 2
4 is provided between the optical guide layers 22 and 24, and these layers 22 to 24 are provided between the cladding layer 21 and the first cladding layer 25. The separation unit 30 is
The layers 11 to 15 are shared with the light emitting device unit 10, and the layers 21 to
26 is shared with the modulation device unit 20. Layer 1 above
Examples of constituent elements and dopants for 1 to 15 and 21 to 25 are as follows. For the sake of simplicity, Ga _x In _1-x As _y P _{1-y is referred} to as GaInAsP. -Cladding layers 11 and 21: Si-doped InP-light guide layers 12 and 22: undoped GaInAsP-active layers 13 and 23: undoped GaInAsP-light guide layers 14 and 24: undoped GaInAsP-first cladding layers 15 and 25: Zn-doped InP

The active layers 13 and 23 have a multi-quantum well (MQW) structure made of GaInAsP. The MQW structure of the active layer 13 is determined so that light in the 1.55 μm band is emitted from this MQW structure. The MQW structure of the active layer 23 is determined so that the absorption short wavelength of the MQW structure is shorter than the laser oscillation wavelength determined by the diffraction grating 14a by about 50 nm.

The light emitting section 40 is adjacent to the modulation device section 20. The light emitting portion 40 has a window portion 44 provided on the substrate 2. The window 44 has a light incident surface 40g.
The light from the modulation device section 20 enters the window section 44 through the light incident surface 40g. The window portion 44 includes a first window layer 42 provided on the substrate 2 and a second window layer 43 provided on the first window layer 42. In this embodiment, the first
The window layer 42 is made of iron (Fe) -doped InP, and the second window layer 43 is made of Si-doped InP. The second window layer 43 of the window portion 44 also functions as a hole blocking layer. Further, the light emitting portion 40 has a light emitting surface 40f and an antireflection film 45 provided on the light emitting surface 40f. The antireflection film 45 is made of silicon nitride (SiN) or silicon oxynitride.
It can be formed from a dielectric material such as (SiON). The reflectance of the antireflection film 45 can be 1% or less. The light incident on the window 44 is emitted to the outside through the light emitting surface 40f and the antireflection film 45.

The second window layer 43 and the first cladding layer 15,
A second clad layer 16 is formed on 25. The second clad layer 16 is shared by the light emitting device unit 10, the modulation device unit 20, the separating unit 30, and the light emitting unit 40. The constituent elements and dopants of the second cladding layer 16 are as follows. -Second cladding layer 16:
Zn-doped InP

Referring to FIG. 1A, the light emitting portion 40 has a light absorbing layer 41. The second cladding layer 16 is provided between the light absorption layer 41 and the window portion 44. Also,
As shown in FIG. 1B, the light absorption layer 41 is in contact with not only the upper surface of the second cladding layer 16 but also the side surfaces of the second cladding layer 16 and the window portion 44. Therefore, the second cladding layer 1
Compared with the case where the light absorption layer is provided only on the upper surface of 6, stray light can be suppressed more effectively. Further, the light absorption layer 41 may be directly formed on the upper surface of the second window layer 43.

The light absorption layer 41 is the contact layer 1 described later.
Similar to 7, 27, Zn-doped Ga _xIn_1-xAs (
Below, GaInAs). Light absorbing layer 41
The composition ratio x of GaInAs that constitutes the
Selected to be lattice matched to, preferably 0.4
7 Here, the lattice matching means that the difference in lattice constant is approximately
It means the case of −0.1 to + 0.1%. Lattice match
Photoluminesce from GaInAs with compositional ratio x of about
The wavelength of the luminescence light is about 1680 nm at room temperature.
Is. This wavelength is a wave of light emitted from the active layer 13.
Longer than 1550 nm.

Referring again to FIG. 1A, the contact layer 17 is provided in the light emitting device section 10 and the contact layer 27 is provided in the modulation device section 20 on the second cladding layer 16. Contact layers 17, 27
Is composed of Zn-doped GaInAs. An electrode 18 for the light emitting device section 10 is provided on the contact layer 17, and a modulation device section 20 is provided on the contact layer 27.
An electrode 28 for is provided. Electrodes 18, 28
Is composed of a metal such as gold (Au) / Zn. On the back side of the substrate 2, an electrode 3 used together with the electrodes 18, 28
8 is formed. The electrode 38 is AuGe / Ni / A
It is composed of a metal such as u. Further, the semiconductor optical integrated device 1 has a passivation film 19 that covers the contact layers 17 and 27 and the second cladding layer 16. The passivation film 19 can be made of silicon oxide (SiO ₂ ).

The operation of the semiconductor optical integrated device 1 will be described below. Referring to FIG. 1A, the light emitting device unit 10
, The electrode 18 is connected to the anode of the DC power supply 51, and the electrode 38 is connected to the cathode of the power supply 51. Therefore, a forward bias voltage is applied to the light emitting device section 10. In the modulation device unit 20, the electrode 28 is connected to the cathode of the power supply 52 that receives the modulation signal S, and the electrode 38 is connected to the anode of the power supply 52. Therefore, a reverse bias voltage is applied to the modulation device section 20. The electrode 38 is the light emitting device unit 1.
It is shared by both 0 and the modulation device section 20.

When the forward bias voltage is applied to the light emitting device section 10 as described above, light is emitted from the active layer 13. Then, laser oscillation occurs due to the diffraction grating 14a formed at the interface between the light guide layer 14 and the first cladding layer 15, and the laser light passes through the active layers 13, 23 and the light guide layers 12, 22, 14, 24. Propagate.

When a voltage is not applied to the modulation device section 20, the absorption edge wavelength of the active layer 13 is shorter than the wavelength of the laser light, so that the laser light propagates through the active layer 23 without being absorbed. However, when a sufficiently large reverse bias voltage is applied to the modulation device unit 20, the quantum confined Stark effect (QCSE: Quantum) in the active layer 23.
Confined Stark Effect) occurs, and this effect absorbs light. Therefore, by applying the modulated reverse bias voltage from the power supply 52 to the modulation device unit 20, the laser light from the light emitting device unit 10 can be modulated. The laser light modulated by the modulation device section 20 enters the window section 44.

Since the waveguide structure is not formed in the window portion 44, the laser light incident on the window portion 44 propagates in the window portion 44 while spreading radially. Most of the laser light that reaches the antireflection film 45 passes through the antireflection film 45 and is emitted to the outside, and a very small part thereof is reflected by the antireflection film 45. Since the laser light spreads and travels in the window portion 44, it does not return to the active layer 23 and the active layer 13 even when reflected by the antireflection film 45. Therefore, there is no adverse effect that the intensity of the laser light is reduced.
That is, the window portion 44 has a function of reducing the return light to the active layers 13 and 23.

In the window 44, the active layers 13,
The light component L ₁ traveling at an angle θ with respect to the axis L along the extending direction of 23 directly reaches the second cladding layer 16. Further, the light L ₂ reflected by the antireflection film 45 also reaches the second cladding layer 16. Second cladding layer 16 and window portion 4
Since 4 is composed of InP, the lights L ₁ and L ₂ are incident on the second cladding layer 16 without being reflected at the interface between them. After being incident on the second cladding layer 16, the lights L ₁ and L ₂ pass through the second cladding layer 16 and reach the light absorption layer 41. Since the Eg of the light absorption layer 41 is smaller than the light energy corresponding to the wavelengths of the light L ₁ and L ₂ as described above, the light L ₁ and L ₂ are absorbed by the light absorption layer 41. Therefore, stray light generated in the window portion 44 is reduced. Therefore, the interaction between the laser light and the stray light is suppressed, the intensity of the laser light is prevented from decreasing, and the radiation pattern of the light emitted from the light emitting end face is surely monomodal. Become.

The present inventors measured a far field pattern (FFP) of the semiconductor optical integrated device 1 in order to confirm the effect of the semiconductor optical integrated device 1.
2A and 2B are graphs showing the FFP of the laser light emitted from the semiconductor optical integrated device 1. 2A shows the FFP measured along the x-axis direction shown in FIG. 1, and FIG. 2B shows the FF measured along the y-axis direction shown in FIG.
P is shown. 2A and 2B, the horizontal axis represents the tilt angle from the predetermined center axis passing through the active layers 13 and 23 of the semiconductor optical integrated device 1, and the vertical axis represents the light intensity of the laser light. .
2A and 2B, it can be seen that the FFP of the laser light emitted from the semiconductor optical integrated device 1 has a monomodal peak in both the x and y axis directions.

In order to make a comparison with the semiconductor optical integrated device 1, the present inventors manufactured a semiconductor optical integrated device having no light absorption layer 41 and conducted FFP measurement. FIG. 3A is a sectional view of a semiconductor optical integrated device having no light absorption layer. FIG. 3B is a sectional view taken along the line II-II of FIG. Referring to FIG. 3A, the semiconductor optical integrated device 50 includes a light emitting device section 100, a modulation device section 200, and a separating section 30.
0, and the light emitting part 400. Further, the semiconductor optical integrated device 50 has the second cladding layer 116 included in each of these parts. A passivation film 190 is provided on the second cladding layer 116 in the light emitting section 400. Referring to FIG. 3B, a passivation film 190 made of SiO ₂ is provided on the side surfaces of the window portion 440 and the second cladding layer 600. That is, unlike the semiconductor optical integrated device 1, the semiconductor optical integrated device 50 does not have a light absorption layer.

FIGS. 4A and 4B show a semiconductor optical integrated device 50.
It is a graph which shows FFP of emitted laser light. Figure 4
(a) is the FFP measured along the x-axis direction shown in FIG.
4B shows the FFP measured along the y-axis direction shown in FIG. Referring to FIG. 4A, so-called side lobes S ₁ , S ₂ and S ₃ are observed on both sides of the main peak P ₁ . Further, referring to FIG. 4B, side lobes S ₄ and S ₅ are observed on one side of the main peak P ₁ . If there are such side lobes S _{1 to} S ₄ , the optical coupling efficiency between the semiconductor optical integrated device 50 and the optical fiber will be significantly reduced. As described above, the semiconductor optical integrated device including the EA modulator is generally strongly affected by the stray light of the window.

The present inventors believe that the reason why the side lobes S _{1 to} S ₄ occur in the FFP is as follows. Figure 3
Referring to, the light L ₃ traveling in the window portion 440 at an angle θ with respect to the traveling direction of the laser light enters the second cladding layer 116, passes through the second cladding layer 116, and passes through the passivation film 190. Leading to. Since the passivation film 190 is made of SiO ₂ , such light L ₃ is not absorbed by the passivation film 190 but becomes stray light and stays in the window portion 440. Therefore, interaction between the stray laser light occurs, side lobe S ₁ to S ₄ are generated.

Since the semiconductor optical integrated device 1 according to the present embodiment has the unimodal FFP, the optical coupling efficiency between the semiconductor optical integrated device 1 and the optical fiber is maintained sufficiently high.
That is, the semiconductor optical integrated device 1 has an excellent effect as compared with the semiconductor optical integrated device that does not include the light absorption layer 41.

(Second Embodiment) FIGS. 5A to 5C and FIG.
A method of manufacturing a semiconductor optical integrated device according to a third embodiment of the present invention with reference to (a) to (c), FIGS. 7 (a) to (c), and FIGS. 8 (a) to (c). Will be explained. The case where the semiconductor optical integrated device 1 is manufactured will be described below.

(Process of Forming Multilayer Film for Light Emitting Device) First, the process of forming a multilayer film for light emitting device will be described with reference to FIGS. 5 (a) and 5 (b). An n-type cladding film 111, a light guide film 112, an active layer film 113, and a light guide film 114 are sequentially grown on the n-type InP substrate 2.
A metalorganic vapor phase epitaxy method (MOCVD method) can be used to grow these films 111 to 114. The constituent elements, dopants and thicknesses of these films 111 to 114 are as follows. -N-type cladding film 111: Si-doped InP, 200 nm-light guide film 112: undoped GaInAsP, 50 nm-active layer film 113: undoped GaInAsP, 150 nm-light guide film 114: undoped GaInAsP, 50 nm active layer film 113 is a GaInAsP semiconductor. MQ consisting of
Equipped with W.

Next, the diffraction grating 14a is formed on the surface layer portion of the light guide film 114. The diffraction grating 14a is provided, for example, by forming irregularities on the surface layer portion periodically by using lithography and etching. Then, the p-type first cladding film 115 is formed on the diffraction grating 14a by MOC.
It is epitaxially grown by the VD method. Examples of constituent elements, dopants, and thicknesses of the first cladding film 115 are: first cladding film 115: Zn-doped InP,
It is 200 nm.

Next, the first mask layer 61 is formed on the first cladding film 115. The first mask layer 61 covers the portions of the films 111 to 115 to be the semiconductor laser element portion. The first mask layer 61 is made of a silicon nitride (hereinafter, SiN) film and is formed by a method such as a CVD method, photolithography, and etching. The first mask layer 61 is made of silicon oxide (Si
It may be composed of an insulating silicon compound film such as an O ₂ ) film and a silicon oxynitride (hereinafter, SiON) film.

Subsequently, the film 11 is formed by using the first mask layer 61.
Etching 1-115. This etching is, for example, Reactive Ion Etching (R).
IE) method. By this etching, the surface 2a of the portion of the substrate 2 where a semiconductor multilayer film for the modulation device section, which will be described later, is to be formed is exposed, and the first semiconductor multilayer film 100 for the semiconductor laser is formed.

(Formation Step of Multilayer Film for Modulation Device Section) Next, the formation step of the multilayer film for modulation device section will be described with reference to FIG. In this step, the n-type cladding film 121, the light guide film 122, the active layer film 123, and the active layer film 123 are formed on the surface 2a of the substrate 2 while leaving the first mask layer 61.
The light guide film 124 and the first clad film 125 are sequentially grown.

Examples of the constituent elements, dopants and thicknesses of these films 121 to 125 are: n-type cladding film 121: Si-doped InP, 200 nm, light guide film 122: undoped GaInAsP, 50 nm, active layer film 123: Undoped GaInAsP, 150 nm • Light guide film 124: undoped GaInAsP, 50 nm • First cladding film 125: Zn-doped InP, 200 nm. The active layer film 123 has a quantum well structure such as MQW made of GaInAsP semiconductor. The second semiconductor multilayer film 2 for the modulation device is manufactured by the steps up to now.
00 is formed.

(First Mesa Forming Step) Referring to FIG. 6A, the first mesa 71 is formed on the substrate 2. The first mesa 71 is formed as follows. First, after forming the second semiconductor multilayer film 200, the first mask layer 61 is removed and the first cladding films 115 and 125 are exposed. Next, a stripe-shaped second mask layer 62 extending in the direction from the first semiconductor multilayer film 100 to the second semiconductor multilayer film 200 is formed on these films. Second mask layer 6
2 is formed of an insulating film such as SiN. Thereafter, using the second mask layer 62, the first semiconductor multilayer films 100 and 200 are etched by the RIE method until the surface of the substrate 2 is exposed. By the above procedure, the first mesa 71 is formed as shown in FIG.

The first mesa 71 is the first semiconductor multilayer film 10.
0, and a modulation device mesa 20 formed from the second semiconductor multilayer film 200.
1 and. The light emitting device mesa 101 includes a cladding layer 11, a light guide layer 12, an active layer 13, a light guide layer 14,
And a first cladding layer 15. In addition, the modulation device mesa 201 includes the clad layer 21, the light guide layer 22, the active layer 23, the light guide layer 24, and the first clad layer 25.
Have.

Further, referring to FIG. 6A, the surface of the substrate 2 is exposed between the end surface of the modulation device mesa 201 and the edge 2b of the substrate 2. A window portion that contacts the end surface of the modulation device mesa 201 is formed in the exposed surface portion in a later step.

(Embedded Layer Forming Step) Referring to FIGS. 6A and 6B, the first embedded layer 14 is formed on the exposed surface of the substrate 2.
2 and a second buried layer 143 is formed on the first buried layer 142. The first buried layer 142 may be composed of Fe-doped InP, and the second buried layer 143 may be Si-doped I.
It can be composed of nPs. In addition, the first buried layer 1
The MOCVD method may be used to form the second buried layer 143 and the second buried layer 143.

After forming the second buried layer 143, the second mask layer 62 is removed to expose the first cladding layers 15 and 25. After that, as shown in FIG. 6C, the first cladding layer 1
5, 25 and the second buried layer 143, Zn-doped In
The second cladding film 116 of P is formed.

(Second Mesa Forming Step) Subsequently, a third mask layer made of an insulating film such as SiN is formed on the second cladding film 116. Using the third mask layer, the second cladding film 116, the second burying layer 143, and the first burying layer 14 are formed.
2 is etched, and as shown in FIG. 7A, the second mesa 7
2 is formed. The second mesa 72 is the second cladding film 11
6, a first buried layer 142, and a second buried layer 143. Further, the second mesa 72 includes the first mesa 71. The second cladding film 116 appears on the upper surface of the second mesa 72, and the second cladding film 116 appears on the side surface of the second mesa.
The first buried layer 142 and the second buried layer 143 are exposed. For forming the second mesa 72, etching with a solution of hydrogen bromide (HBr) or the like may be used, or dry etching may be used.

(Third Mesa Forming Step) Referring to FIG. 7B, the semiconductor film 141 for forming the light absorption layer 41 and the contact layers 17 and 27 is formed on the side surface and the upper surface of the second mesa 72. It The semiconductor film 141 is Zn-doped Ga
It is composed of InAs and has a hole concentration of 1 × 10 ¹⁹ to 2
It can be set to × 10 ¹⁹ cm ^-3 . The semiconductor film 141 can be formed by MOCVD. The semiconductor film 141 is formed so as to be lattice-matched with the second mesa 72. Therefore, the wavelength of photoluminescence light from the semiconductor film 141 is longer than the wavelength of light emitted from the active layer 13.

After forming the semiconductor film 141, the semiconductor film 14 is formed.
On the first mask layer 64 made of an insulating film such as SiN
Is formed. Referring to FIG. 7C, the fourth mask layer 6
4 has a first portion 64a and a second portion 64b. The first portion 64a overlaps the first mesa 71. The second portion 64b covers a portion of the second mesa 72 that should become the light emitting portion 40. RIE etching is performed using the fourth mask layer 64, and after the etching, a fourth mask layer 64 is formed.
When the mask layer 64 is removed, the light emitting portion 40 and the third mesa 73 are obtained as shown in FIG.

The light emitting portion 40 has a first window layer 42 formed of the first burying layer 142, a second window layer 43 formed of the first burying layer 143, and a second cladding layer 16. And a light absorption layer 41 formed of the semiconductor film 141. The window portion 44 is composed of the first window layer 42 and the second window layer 43. The light absorption layer 41 covers the side surfaces of the window portion 44 and the second cladding layer 16 and the upper surface of the second cladding layer 16.

(Finishing Process) Referring to FIG. 8B, the contact layers 17 and 27 are formed. The contact layers 17 and 27 are the semiconductor film 14 included in the third mesa 73.
1 and is formed by lithography and etching.

After that, the light emitting portion 40 and the third mesa 73 are formed.
A passivation film 19 made of an insulating material such as SiO ₂ is deposited thereon. An opening is provided in the passivation film 19, and the contact layers 17 and 27 are exposed.
Next, the light emitting portion 40 and the third mesa 73 are filled with the resin 80. At this time, the contact layers 17 and 27 are exposed in the openings of the passivation film 19. As the resin 80, a thermosetting resin such as a benzocyclobutene (BCB) resin can be used. Then, the antireflection film 45 is formed on the end surface of the light emitting portion 40, and the reflection film 46 is formed on the end surface of the third mesa 73. The antireflection film 45 can be formed of a dielectric material such as silicon nitride (SiN) or silicon oxynitride (SiON). The reflectance of the antireflection film 45 can be set to 1% or less. With this configuration, the light inside the window 44 is easily emitted to the outside, so that the returning light is suppressed and the generation of stray light is reduced. Then, the electrode 18 is formed on the contact layer 17 exposed in the opening of the passivation film 19, and the electrode 28 is formed on the contact layer 27. The electrodes 18 and 28 are formed of a metal such as Au / Zn. A vacuum deposition method may be used to form the electrodes 18 and 28, for example. Then, on the back surface of the substrate 2,
An electrode 38 made of a metal such as AuGe / Ni / Au is formed. Through the above steps, the semiconductor optical integrated device 1 is completed as shown in FIG.

According to the method of manufacturing the semiconductor optical integrated device of the second embodiment, the window 44 and the second cladding layer 16 are formed.
The light absorption layer 41 is formed to cover the side surface of the second cladding layer 16 and the upper surface of the second cladding layer 16. The light absorption layer 41 is composed of InGaAs, and its photoluminescence light wavelength is equal to that of the active layer 13.
Longer than the wavelength of the light emitted from. Therefore, the light absorption layer 41
This reduces stray light in the window 44. That is, according to the above manufacturing method, the semiconductor optical integrated device in which the stray light in the window portion 44 is reduced is manufactured.

Further, the light absorption layer 41 and the contact layer 1
Since 7 and 18 are formed from the semiconductor film 141, an extra step for forming only the light absorption layer 41 is unnecessary.
Furthermore, since the window portion 44 is formed from the first embedded layer 142 and the second embedded layer 143, an extra step for forming only the window portion 44 is unnecessary. That is, according to the method for manufacturing a semiconductor optical integrated device according to the second embodiment, the semiconductor optical integrated device according to the present invention can be manufactured without increasing the number of steps.

As described above, referring to some embodiments,
Although the semiconductor optical integrated device according to the present invention has been described, the present invention is not limited to these. In the first and second embodiments, the semiconductor optical integrated device including the EA modulator has been described. However, even in the case of the semiconductor optical integrated device without the EA modulator, the stray light in the window portion is reduced and the stray light It is clear that the impact will be reduced.

The light absorption layer 41 is not limited to GaInAs, but G
It may also be composed of a _x In _1-x As _y P _1-y (0 <x <1, 0 <y <1). Also in this case, the compositions x and y are
The photoluminescence light wavelength is determined to be longer than the wavelength of the light from the light emitting device section 10.

The light absorption layer 41 is formed on the lower surface of the window 44,
That is, it may be provided between the substrate 2 and the window portion 44. A semiconductor optical integrated device including such a light absorption layer,
It can be produced by modifying the second embodiment as follows. That is, the first for the semiconductor laser
Prior to forming the semiconductor multilayer film 100, the light absorption layer film to be the light absorption layer 41 is grown on the substrate 2. The first semiconductor multilayer film 100 grown in the region where the modulation device section is to be formed on the substrate 2 is removed to expose the light absorption layer film. Further, the second semiconductor multilayer film 200 grown in the region on the substrate where the window is to be formed is removed,
From the first semiconductor multilayer film 100 to the second semiconductor multilayer film 10
When forming the first mesa 71 formed of the first and second semiconductor multilayer films extending in the direction toward 0, the light absorption layer film is exposed. By doing so, a semiconductor optical integrated device including the light absorption layer between the substrate 2 and the window portion 44 can be manufactured.

[0057]

As described above, according to the semiconductor optical integrated device of the present invention, stray light is absorbed by the light absorbing layer provided in contact with the window portion, so that the influence of stray light is reduced. . Therefore, there is provided a semiconductor optical integrated device capable of preventing a decrease in light intensity and a decrease in optical coupling efficiency with an optical fiber due to stray light in the window. In addition, the effect of the present invention is particularly prominent in a semiconductor optical integrated device including an EA modulator that is strongly affected by stray light in the window.

[Brief description of drawings]

FIG. 1A is a sectional view showing an embodiment of a semiconductor optical integrated device according to the present invention. 1 (b) is shown in FIG. 1 (a).
It is sectional drawing which follows the II line in FIG.

2A and 2B are graphs showing FFP of laser light emitted from a semiconductor optical integrated device.

FIG. 3 (a) is a cross-sectional view of a semiconductor optical integrated device having no light absorption layer. FIG. 3B is a sectional view taken along the line II-II in FIG.

4 (a) and 4 (b) are graphs showing FFP of laser light emitted from a semiconductor optical integrated device having no light absorption layer.

5A to 5C are views for explaining the method for manufacturing the semiconductor optical integrated device according to the second embodiment.

6A to 6C are views for explaining the method for manufacturing the semiconductor optical integrated device according to the second embodiment.

7A to 7C are views for explaining the method for manufacturing the semiconductor optical integrated device according to the second embodiment.

8A to 8C are views for explaining the method for manufacturing the semiconductor optical integrated device according to the second embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Integrated semiconductor optical device, 2 ... Substrate, 10 ... Light emitting device part 11, 21, 15, 25 ... Clad layer, 12, 22
... light guide layer, 12, 22, 14, 24 ... light guide layer,
13, 23 ... Active layer, 14a ... Diffraction grating, 17, 27 ...
Contact layer, 18, 28 ... Electrode, 19 ... Passivation film, 20 ... Modulation device section, 30 ... Separation section, 38 ...
Electrodes, 40 ... Light emitting portion, 40f ... Light emitting surface, 41 ... Light absorbing layer, 44 ... Window portion, 111, 121, 122, 124 ...
Clad film, 112, 114 ... Optical guide film, 115, 1
25 ... Clad film, 141 ... Semiconductor film, 190 ... Passivation film.

Claims (8)

[Claims] 1. A semiconductor light emitting element portion that emits light, a first surface on which the light is incident, and a second surface on which the incident light is emitted.
And a window having a semiconductor portion provided between the first and second surfaces, and a wavelength of the photoluminescence light longer than the wavelength of the light provided on the window. A semiconductor optical integrated device comprising a light absorption layer containing a first semiconductor. 2. The semiconductor optical integrated device according to claim 1, wherein the light absorption layer is provided on at least one of an upper surface and a side surface of the window portion. 3. The semiconductor modulation element section according to claim 1, further comprising a semiconductor modulation element section provided so as to modulate the light from the semiconductor light emitting element section and allow the modulated light to enter the first surface. Semiconductor integrated device. 4. The semiconductor light emitting device section includes a first contact layer and a first contact layer provided on the first contact layer.
And a second contact layer and a second contact layer,
2. The semiconductor optical integrated device according to claim 3, further comprising a second electrode provided on the contact layer, wherein the first and second contact layers include the first semiconductor. 5. The semiconductor according to claim 1, further comprising a semiconductor film made of a second semiconductor capable of transmitting the light, between the light absorption layer and the window portion. Optical integrated device. 6. The semiconductor light emitting device section comprises Ga _x In _1-x A
s _y P _1-y (0 <x <1, 0 <y <1) has an active layer containing a semiconductor, the window portion contains an InP semiconductor, and the light absorption layer has a Ga _x
The semiconductor optical integrated device according to claim 1, comprising an In _1-x As _y P _1-y (0 <x <1, 0 <y ≦ 1) semiconductor. 7. The semiconductor optical integrated device according to claim 1, further comprising an antireflection film provided on the second surface. 8. The semiconductor optical integrated device according to claim 7, wherein the antireflection film has a reflectance of 1% or less.