JP2005260109A - Optical semiconductor element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an SIBH (insulating buried heterostructure) type optical semiconductor element which can eliminate dopant inter-diffusion between a p-type semiconductor layer forming part of a mesa and a semi-insulating burial layer for the mesa to be buried therein and thus can maintain an excellent characteristic. <P>SOLUTION: In the buried heterostructure type optical semiconductor element, a mesa structure formed in a semiconductor layer structure on a substrate is buried with a semiconductor layer. The semiconductor element comprises a C-doped, p-type InAlAs cladding layer 16 included in the mesa structure, and an Fe-doped, semi-insulating InP buried layer 18 in which a region of the side surface of the mesa structure corresponding to at least the C-doped, p-type InAlAs cladding layer 16 is buried. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical semiconductor element used for optical communication, for example, an optical semiconductor element such as a semi-insulating buried heterostructure (SIBH) type semiconductor laser or an optical modulator.

  In general, when a semiconductor laser or an optical modulator is manufactured, in order to improve element characteristics and reliability, a heterostructure in which a side surface of a mesa obtained by processing a laminated required semiconductor layer into a stripe is embedded with a semiconductor layer is often used.

  FIG. 5 is a front view of a principal part showing a conventional SIBH type semiconductor laser in which a mesa is embedded with a semi-insulating semiconductor layer. Such a SIBH type semiconductor laser can reduce the device capacity as compared with the pn buried type. Therefore, it is frequently used for high-speed operation.

  In the figure, 1 is an n-type (100) InP substrate, 2 is an n-type InP first cladding layer, 3 is an InGaAsP first optical guide layer, 4 is an InGaAsP-MQW (multiple quantum wells) active layer, and 5 is an InGaAsP. Second light guide layer, 6 is a Zn-doped p-type InP second cladding layer, 7 is a Zn-doped p-type InGaAs contact layer, 8 is a Fe-doped semi-insulating InP buried layer, 9 is a p-side electrode, and 10 is an n-side electrode Respectively.

In order to manufacture the SIBH type semiconductor laser shown in FIG. 5, the steps described below are employed. That is,
(1) An n-type InP first clad layer 2 having a thickness of 0.5 μm is formed on an n-type (100) InP substrate 1 by applying a metalorganic vapor phase epitaxy (MOVPE) method. 1 μm undoped In _0.85 Ga _0.15 As _0.33 P _0.67 first light guide layer 3, 5 nm thick undoped In _0.87 Ga _0.13 As _0.60 P _0.40 well layer with 10 layers and 10 nm thick undoped In _0.85 Ga _0.15 As _0.33 InGaAsP-MQW active layer 4 in which 11 P _0.67 barrier layers are alternately arranged, undoped In _0.85 Ga _0.15 As _0.33 P _0.67 second light guide layer 5 having a thickness of 0.1 μm, p having a thickness of 1.5 μm A type InP second cladding layer 6 and a p-type In _0.53 Ga _0.47 As contact layer 7 having a thickness of 0.5 μm are sequentially grown. In this case, Zn is used for the p-type dopant.

(2)
Next, a chemical vapor deposition (CVD) method is applied to form an insulating film such as SiO ₂ on the contact layer 7, and the insulating film is patterned by photolithography and etching. An insulating film mask having a stripe extending in the [011] direction is formed.

(3)
Next, etching reaching the first cladding layer 2 from the contact layer 7 exposed on both sides of the insulating mask of the stripe is performed to form a mesa stripe.

(4)
Next, an MOVPE method is applied to form an Fe-doped semi-insulating InP buried layer 8 on both sides of the mesa stripe, thereby realizing an optical confinement and current confinement structure.

(5)
Thereafter, the striped insulating film mask is removed, and a p-side electrode and an n-side electrode are formed to complete a SIBH type semiconductor laser.

  By the way, in this SIBH type semiconductor laser, as described above, Zn is used for the p-type impurity in the p-type InP second cladding layer 6 and the p-type InGaAs contact layer 7, and the adjacent semi-insulating material is used. The conductive InP buried layer 8 is doped with Fe in order to make InP semi-insulating.

  In such a configuration, abnormal interdiffusion of Fe and Zn is likely to occur between the Fe-doped semi-insulating InP buried layer 8 and the p-type InP second cladding layer 6 or the p-type InGaAs contact layer 7. Is known (see, for example, Non-Patent Document 1).

  Therefore, in the SIBH type semiconductor laser shown in FIG. 5, a part of the Fe-doped semi-insulating InP buried layer 8 becomes p-type, leading to an increase in leakage current and an increase in parasitic capacitance, thereby degrading element characteristics. There's a problem.

  In recent years, attempts have been made to use ruthenium (Ru) as a dopant for making InP semi-insulating, and it has been found that no interdiffusion of dopant occurs between Ru-doped InP and Zn-doped InP. In order to solve this problem of abnormal interdiffusion, semiconductor lasers and optical modulators using Ru-doped semi-insulating InP as buried layers have been proposed (see, for example, Non-Patent Documents 2 and 3).

  However, in the known technique, Zn having a large diffusion coefficient is used as a p-type dopant in a p-type semiconductor layer such as a p-type InP layer or a p-type InGaAs layer, so that an impurity concentration profile in the p-type semiconductor layer. Is difficult to control precisely.

  By the way, it is not restricted to a SIBH type semiconductor laser and an optical modulator having a similar structure, but the relationship between the semiconductor layer constituting the mesa and the buried layers provided on both sides of the semiconductor layer, the dopant for the semiconductor layer constituting the mesa, and the buried layer Various studies have been made on the dopants for and the like, and many inventions have been proposed.

  For example, a semiconductor laser element is known in which a Zn-doped p-type AlGaAs layer is used as a part of a semiconductor layer constituting a mesa, and this mesa is embedded with n-type AlGaAs (see, for example, Patent Document 1). Patent Document 1 discloses the use of C-doped p-type AlGaAs as a cladding layer, although it is not an element constituting a mesa.

  A compound semiconductor device having a structure in which a C-doped p-type AlGaAs layer is used as a part of a semiconductor layer constituting a mesa and the mesa is embedded with an n-GaAs layer is known (for example, Patent Document 2).

  Similarly, a semiconductor laser element is also known in which a C-doped p-type GaAs layer is used as a part of a semiconductor layer constituting a mesa and the mesa is embedded with a pn buried layer (see, for example, Patent Document 3). .

  There is also known a III-V group compound semiconductor light-emitting device in which a C-doped p-type AlGaInP layer is used as a part of a semiconductor layer constituting a mesa and the mesa is embedded with an n-type GaAs layer (see, for example, Patent Document 4). reference.).

Regardless of any of the known examples described above and the known examples omitted here, the dopant introduced into a part of the semiconductor layer constituting the mesa and the semi-insulating semiconductor layer in which the mesa is embedded It is recognized that there is no awareness of the relationship between the dopants to be introduced into the material, or that there is no knowledge about selection of the best combination.
JP 2001-144383 A JP-A-9-199425 JP 2001-345518 A JP-A-10-308551 E. W. A. Young et al, Applied Physics Letters 56, (1990) 146). A. Dadgar et. al. , Applied Physics Letters 73, (1998) 3878). S. Kondo et. al. , Jpn. J. et al. Appl. Phys. 41, (2002) 1171) K. Kurihara et. al, Indium Phosphide and Related Materials Conference Proc. 2003, WA 2.6

  According to the present invention, there is provided a SIBH type optical semiconductor element which has no dopant interdiffusion between the p-type semiconductor layer constituting a part of the mesa and the semi-insulating embedded layer which embeds the mesa, and thus can maintain excellent characteristics. Try to provide.

  In an optical semiconductor device according to the present invention, an embedded heterostructure type optical semiconductor device in which a mesa structure formed in a semiconductor stacked structure on a group III-V semiconductor substrate is embedded with a semiconductor layer is provided. Carbon (C) -doped p-type III-V semiconductor layer (for example, C-doped p-type InAlAs cladding layer 16, C-doped p-type InGaAs contact layer 17) and at least the C-doped side surface of the mesa structure It is basically provided with a semi-insulating semiconductor layer (for example, Fe-doped semi-insulating InP buried layer 18) that fills the region of the p-type III-V semiconductor layer.

  By adopting the above means, the leakage current to the semi-insulating buried layer can be reduced and the parasitic capacitance can be reduced. Further, since C is used as the dopant of the p-type semiconductor layer, high concentration doping is possible. In addition, it is possible to precisely control the concentration profile, and the basic characteristics of the device are improved as compared with the case where a conventional Zn-doped p-type semiconductor layer is used. For example, a semiconductor laser can contribute to higher output, and an optical modulator can contribute to higher speed.

  In the optical semiconductor device of the present invention, in the SIBH type optical semiconductor device such as a semiconductor laser or an optical modulator, a p-type semiconductor layer constituting a part of the mesa and a semi-insulating buried layer adjacent thereto are appropriately doped. By adopting a simple means for selecting a combination, the mutual diffusion of the dopants is suppressed, and it is possible to prevent the device characteristics from deteriorating, such as an increase in leakage current and an increase in parasitic capacitance. In this case, all the dopants to be selectively used are known, but the object can be achieved for the first time by the combination according to the present invention.

  Specifically, in a buried heterostructure optical semiconductor device in which a mesa structure formed in a semiconductor stacked structure on a group III-V semiconductor substrate is embedded with a semiconductor layer, the mesa structure includes a C-doped p-type III-V. It is possible to adopt a configuration in which a group semiconductor layer is included and at least a region of the C-doped p-type III-V group semiconductor layer is buried with a semi-insulating semiconductor layer among the side surfaces of the mesa structure.

  Further, in a buried heterostructure optical semiconductor device in which a mesa structure formed in a semiconductor stacked structure on an InP substrate is embedded with a semiconductor layer, a C-doped p-type semiconductor layer is included in the mesa structure, and the mesa structure Of these, at least the region of the C-doped p-type semiconductor layer may be buried with an Fe-doped semi-insulating InP layer.

  Further, in a buried heterostructure optical semiconductor device in which a mesa structure formed in a semiconductor stacked structure on an InP substrate is embedded with a semiconductor layer, the mesa structure includes a C-doped p-type InAlAs layer or a p-type InGaAlAs layer. In addition, it is possible to adopt a configuration in which at least the regions of the C-doped p-type InAlAs layer and the p-type InGaAlAs layer are buried with an Fe-doped semi-insulating InP layer in the side surface of the mesa structure.

  Further, in a buried heterostructure optical semiconductor device in which a mesa structure formed in a semiconductor stacked structure on an InP substrate is embedded with a semiconductor layer, a C-doped p-type semiconductor layer is included in the mesa structure, and the mesa structure It is possible to adopt a configuration in which at least a region of the C-doped p-type semiconductor layer is buried with a Ru-doped semi-insulating InP layer.

  Further, in a buried heterostructure optical semiconductor device in which a mesa structure formed in a semiconductor stacked structure on an InP substrate is embedded with a semiconductor layer, the mesa structure includes a C-doped p-type InAlAs layer or a p-type InGaAlAs layer. In addition, a configuration in which at least the regions of the C-doped p-type InAlAs layer and the p-type InGaAlAs layer among the side surfaces of the mesa structure are embedded with a Ru-doped semi-insulating InP layer can be employed.

  In general, among p-type dopants used for III-V group semiconductors, C is known to have low diffusivity, and there are examples of p-type InAlAs layers used in semiconductor lasers using InP substrates. (For example, refer nonpatent literature 4).

  However, since the semiconductor laser is a ridge type and not a buried type, an abnormal interdiffusion between C and the semi-insulating dopant occurs when the C-doped p-type semiconductor layer contacts the semi-insulating semiconductor layer. It is thought that it was not possible to know whether or not this would occur.

  The present inventor conducted SIMS (secondary mass spectroscopy) analysis on many samples having a structure in which a C-doped p-type III-V semiconductor layer and a semi-insulating semiconductor layer are stacked.

  In particular, the analysis was repeated for the structure in which the C-doped p-type InAlAs layer and the Fe-doped semi-insulating InP layer were laminated and the structure in which the C-doped p-type InAlAs layer and the Ru-doped semi-insulating InP layer were laminated. Fe and found that no anomalous interdiffusion occurs between C and Ru, and based on the results, the optical semiconductor device of the present invention with reduced leakage current and parasitic capacitance to the semi-insulating semiconductor layer was obtained. It has been made.

FIG. 1 is a diagram showing a SIMS analysis result of a C-doped InAlAs layer / Fe-doped InP layer laminated structure, specifically, a C-doped p-type InAlAs layer (C concentration: 5 × 10 ¹⁸ cm ⁻³ , layer Thickness: 2 μm) and Fe doped semi-insulating InP layer (Fe concentration: 6 × 10 ¹⁶ cm ⁻³ , layer thickness 0.8 μm) stacked on a (100) InP substrate C and Fe concentration profiles Was obtained by SIMS analysis.

As is apparent from the figure, the C concentration changes sharply at the interface between the C-doped InAlAs layer and the Fe-doped InP layer, and is 10 ¹⁶ cm ⁻³ or less in the Fe-doped InP layer. That is, it can be seen that C does not diffuse into the Fe-doped InP layer. The Fe concentration is segregated by about 1 × 10 ¹⁸ cm ⁻³ at the interface between the Fe-doped InP layer and the C-doped InAlAs layer, but it is 5 × 10 ¹⁵ cm ⁻³ or less in the C-doped InAlAs layer. That is, abnormal Fe diffusion into a p-type semiconductor layer having a concentration (5 to 10) × 10 ¹⁶ cm ⁻³ as reported in the combination of the Fe-doped InP layer and the Zn-doped InP layer in Non-Patent Document 1 is It has not occurred. Therefore, no anomalous interdiffusion occurs between C and Fe.

FIG. 2 is a diagram showing a SIMS analysis result of a C-doped InAlAs layer / Ru-doped InP layer laminated structure, specifically, a C-doped p-type InAlAs layer (C concentration: 7 × 10 ¹⁸ cm ⁻³ , layer Thickness: 1.9 μm) and a Ru-doped semi-insulating InP layer (Ru concentration: 1 × 10 ¹⁷ cm ⁻³ , layer thickness: 0.7 μm) stacked on a (100) InP substrate. This is obtained by SIMS analysis of the concentration profile.

As is apparent from the figure, the C concentration changes sharply at the interface between the C-doped InAlAs layer and the Ru-doped InP layer, and is about 3 × 10 ¹⁶ cm ⁻³ in the Ru-doped InP layer. That is, it can be seen that C does not diffuse into the Ru-doped InP layer. Anyone in the C concentration profile generated from the surface side depends on the knock-on of the surface adhesion C. The Ru concentration also changes sharply at the interface between the Ru-doped InP layer and the C-doped InAlAs layer, and is 1 × 10 ¹⁵ cm ⁻³ or less in the C-doped InAlAs layer. That is, Ru does not diffuse into the C-doped InAlAs layer. Therefore, no anomalous interdiffusion occurs between C and Ru.

  FIG. 3 is a cutaway front view showing the structure of the optical semiconductor device of the first embodiment of the present invention, that is, a semiconductor laser. In FIG. 3, 11 is an n-type (100) InP substrate, and 12 is n Type InP first cladding layer, 13 is an InGaAlAs first optical guide layer, 14 is an InGaAlAs-MQW active layer, 15 is an InGaAlAs second optical guide layer, 16 is a C-doped p-type InAlAs second cladding layer, and 17 is a C-doped p A type InGaAs contact layer, 18 is a Fe-doped semi-insulating InP buried layer, 19 is a p-side electrode, and 20 is an n-side electrode.

In order to fabricate the semiconductor laser of Example 1 seen in FIG. 3, the steps described below are employed. That is,
(1) Applying the MOVPE method, an n-type InP first cladding layer 12 having a thickness of 0.5 μm on an n-type (100) InP substrate 11, an n-type In _0.52 Ga _0.11 As _0.37 As having a thickness of 0.1 μm One light guide layer 13, 10 nm thick undoped In _0.67 Ga _0.17 Al _0.16 As well layers and 10 nm thick undoped In _0.52 Ga _0.11 Al _0.37 As barrier layers are alternately stacked. InGaAlAs-MQW active layer 14, undoped In _0.52 Ga _0.11 Al _0.37 As second light guide layer 15 having a thickness of 0.1 μm, C-doped p-type In _0.52 Al _0.48 As second cladding layer 16 having a thickness of 1.5 μm, thickness A 0.5 μm thick C-doped p-type In _0.53 Ga _0.47 As contact layer 17 is grown in order. The hole concentration in the C-doped p-type In _0.52 Al _0.48 As second cladding layer 16 is 5 × 10 ¹⁷ cm ^{−3 in} the range of 0.5 μm from the active layer 14 side, and the remaining layer thickness In the range of 1 μm, it was 1 × 10 ¹⁹ cm ⁻³ .

(2)
Next, a CVD method is applied to deposit an insulating film made of SiO ₂ on the contact layer 17, and the insulating film is patterned by photolithography and etching, for example, with a width of about 011 extending in the [011] direction. An insulating film mask having a 2 μm stripe is formed.

(3)
Next, dry etching reaching the first cladding layer 12 from the contact layer 17 exposed on both sides of the insulating mask of the stripe is performed to form a mesa stripe.

(4)
Next, the surface of the first cladding layer 12 extending on the side surfaces of the mesa stripe and on both sides of the mesa stripe is subjected to a surface treatment for removing dry etching damage, and then the MOVPE method is applied to the mesa stripe. An Fe-doped semi-insulating InP buried layer 18 is formed on both sides of the stripe to realize an optical confinement / current confinement structure.

(5)
Thereafter, the striped insulating film mask is removed, and a p-side electrode 19 made of Au / Zn / Au and an n-side electrode 20 made of AuGe are formed, thereby completing the SIBH type semiconductor laser shown in FIG.

  In the semiconductor laser obtained in this way, since the interdiffusion of the dopant does not occur between the C-doped p-type InAlAs second cladding layer 16 and the Fe-doped semi-insulating InP buried layer 18 that are in contact with each other over a wide area. When compared with the conventional Zn-doped p-type InP cladding layer, the leakage current to the semi-insulating InP buried layer is reduced.

In addition, since the C-doped p-type InAlAs second cladding layer 16 is used, a high-concentration p-type doping of 3 × 10 ¹⁸ cm ⁻³ or more, which was difficult with the conventional Zn-doped p-type InP cladding layer, becomes possible. Therefore, since the series resistance in the cladding layer can be reduced, the element resistance of the optical semiconductor element can be reduced.

  In addition, since C has low diffusivity, it is possible to precisely control a desired hole concentration profile in the p-type semiconductor layer even when doped at a high concentration. The optical loss can be reduced.

  From the above, this semiconductor laser has little leakage current and heat generation even when operating at a large current, so that, for example, device characteristics such as optical output are better than those of a conventional SIBH type semiconductor laser.

  In the semiconductor laser of Example 1, C-doped p-type InGaAs is used as the material of the contact layer 17, but this may be replaced with Zn-doped p-type InGaAs.

  Further, although C-doped p-type InAlAs is used as the material of the second cladding layer 16, this may be replaced with C-doped p-type InGaAlAs.

  Further, although undoped InGaAlAs is used as the material of the second light guide layer 15, this may be replaced with C-doped p-type InGaAlAs.

  Further, the InGaAlAs barrier layer in the active layer 14 may be doped with C.

  The MQW active layer 14 is composed of an InGaAlAs well layer and an InGaAlAs barrier layer, but may be composed of an undoped InGaAsP well layer and an undoped InGaAsP barrier layer.

  Further, although Fe-doped semi-insulating InP is used as the material of the buried layer 18, this may be replaced with Ru-doped semi-insulating InP.

  FIG. 4 is a cutaway front view showing the structure of the optical semiconductor element of the second embodiment of the present invention, that is, the optical modulator. In FIG. 4, 21 is an n-type (100) InP substrate, 22 is n-type InP first cladding layer, 23 is InGaAlAs (well layer) / InAlAs (barrier layer) -MQW light absorption layer, 24 is a C-doped p-type InAlAs second cladding layer, 25 is a C-doped p-type InGaAs contact layer, 26 Denotes a Ru-doped semi-insulating InP buried layer, 27 denotes a p-side electrode, and 28 denotes an n-side electrode.

  Since this optical modulator is fabricated by almost the same procedure as the semiconductor laser of Example 1, much explanation is not required, but the MQW light absorption layer 23 is an undoped InGaAlAs well having a tensile strain of 0.3% and a layer thickness of 10 nm. The strain compensation MQW is configured by alternately laminating 10 layers of layers and 11 layers of undoped InAlAs barrier layers having a compressive strain of 0.3% and a layer thickness of 10 nm.

  Further, a C-doped p-type InAlAs second clad layer 24 having a layer thickness of 1.5 μm and a C-doped p-type InGaAs contact layer 25 having a layer thickness of 0.5 μm are stacked on the strain-compensated MQW light absorption layer 23, and a mesa stripe is formed. Is buried with a Ru-doped semi-insulating InP buried layer 26.

  In this optical modulator, since the interdiffusion of dopant does not occur between the C-doped p-type InAlAs second cladding layer 24 and the Ru-doped semi-insulating InP buried layer 26 that are in contact with each other over a wide area, the conventional Zn-doped Compared to an optical modulator having a p-type cladding layer, the parasitic capacitance can be reduced, so that the element capacitance is also reduced.

  Further, since C having low diffusibility is used as the dopant of the p-type cladding InAlAs second cladding layer 24, the diffusion of the p-type dopant into the MQW light absorption layer 23 hardly occurs.

  From the above, it is possible to improve the high-speed modulation characteristics as compared with a conventional optical modulator having a Zn-doped p-type InP cladding layer.

  In the optical modulator of the second embodiment, C-doped p-type InGaAs is used as the material of the contact layer 25, but this may be replaced with Zn-doped p-type InGaAs.

  Further, although C-doped p-type InAlAs is used as the material of the second cladding layer 24, it may be replaced with C-doped p-type InGaAlAs.

  Further, although undoped InAlAs is used as the material of the barrier layer in the MQW light absorption layer 23, it may be replaced with undoped InGaAlAs.

  The MQW light absorption layer 23 is composed of an undoped InGaAlAs well layer and an undoped InAlAs barrier layer, but may be composed of an undoped InGaAsP well layer and an undoped InGaAsP barrier layer.

  Further, although Ru-doped semi-insulating InP is used as the material of the buried layer 26, this may be replaced with Fe-doped semi-insulating InP.

  In the present invention, in addition to the above embodiments, the semiconductor laser of Embodiment 1 and the optical modulator of Embodiment 2 can be integrated to form an optical semiconductor device, or can be applied to a light receiving device or the like.

It is a diagram showing the SIMS analysis result of a C dope InAlAs layer / Fe dope InP layer laminated structure. It is a diagram showing the SIMS analysis result of a C dope InAlAs layer / Ru dope InP layer laminated structure. It is a principal part cutting front view showing the structure of the optical semiconductor element of Example 1 in this invention, ie, a semiconductor laser. It is a principal part cutting front view showing the structure of the optical semiconductor element of Example 2 in this invention, ie, an optical modulator. It is a principal part cutting front view showing the conventional SIBH type | mold semiconductor laser which embedded the mesa with the semi-insulating semiconductor layer.

Explanation of symbols

11 n-type (100) InP substrate 12 n-type InP first cladding layer 13 InGaAlAs first optical guide layer 14 InGaAlAs-MQW active layer 15 InGaAlAs second optical guide layer 16 C-doped p-type InAlAs second cladding layer 17 C-doped p Type InGaAs contact layer 18 Fe-doped semi-insulating InP buried layer 19 p-side electrode 20 n-side electrode

Claims (5)

In a buried heterostructure optical semiconductor device in which a mesa structure formed in a semiconductor stacked structure on a group III-V semiconductor substrate is buried with a semiconductor layer,
A carbon (C) -doped p-type group III-V semiconductor layer included in the mesa structure;
An optical semiconductor element comprising: a semi-insulating semiconductor layer that fills at least a region of the C-doped p-type III-V semiconductor layer in the side surface of the mesa structure. 2. The optical semiconductor device according to claim 1, wherein the III-V semiconductor substrate is made of InP and the semi-insulating semiconductor layer is made of Fe-doped InP. At least a part of the C-doped p-type III-V semiconductor layer included in the mesa structure is a p-side cladding layer made of InAlAs or InGaAlAs, and the semi-insulating semiconductor layer made of Fe-doped InP. The optical semiconductor device according to claim 1, wherein the optical semiconductor device is a material. 2. The optical semiconductor device according to claim 1, wherein the III-V semiconductor substrate is made of InP and the semi-insulating semiconductor layer is made of Ru-doped InP. At least a part of the C-doped p-type III-V semiconductor layer included in the mesa structure is a p-type cladding layer made of InAlAs or InGaAlAs, and the semi-insulating semiconductor layer made of Ru-doped InP. The optical semiconductor device according to claim 1, wherein the optical semiconductor device is a material.

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