JP2005217195A - Optical semiconductor device, and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical semiconductor device in which the mutual diffusion of a p-type dopant and an iron atom is reduced, and to provide a method for manufacturing the optical semiconductor device. <P>SOLUTION: The optical semiconductor device 1 comprises a carbon-doped first cladding layer 3, a second cladding layer 5, an active layer 7, and a buried region 9. The active layer 7 is provided between the first cladding layer 3 and the second cladding layer 5. The buried region 9 is provided so that current is confined to the active layer 7. The buried region 9 contains an iron-doped InP layer 11. The iron-doped InP layer 11 has high resistance so that current is confined to the active layer 7. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical semiconductor device and a method for manufacturing the optical semiconductor device.

  Reference 1 (Japanese Patent Laid-Open No. 9-214045) describes a semiconductor laser. In this semiconductor laser, an Fe-doped InP buried layer is provided so as to bury a mesa stripe including an active layer, and an Fe diffusion prevention layer is provided between the Fe-doped InP buried layer and the mesa stripe. The Fe diffusion preventing layer prevents a decrease in resistivity of the Fe-doped InP buried layer and also prevents a decrease in impurity concentration of the p-type InP layer.

  Reference 2 (Japanese Patent Laid-Open No. 8-255950) describes an embedded semiconductor laser. The buried semiconductor laser is a semiconductor laser including a mesa portion including a quantum well active layer formed on an InP substrate and a buried portion that embeds a side surface of the mesa portion. In the buried portion, a p-InP layer, An InGaAlAs layer having a larger band gap than InP, a semi-insulating InP layer, and an n-InP layer are sequentially provided. This embedded semiconductor laser keeps the resistivity of the semi-insulating InP layer high, has a small leakage current, and can operate up to a high output.

Document 3 (Japanese Patent Laid-Open No. 2001-352131) describes a semi-insulating buried ridge structure. In the semi-insulating buried ridge structure, a plurality of InAlAs and / or InGaAlAs layers are used to prevent direct contact between the cladding layer and the active layer and between the current blocking layer and the active layer.
Japanese Patent Laid-Open No. 9-214045 JP-A-8-255950 JP 2001-352131 A

  In the semiconductor elements described in these documents, a zinc element having a large diffusion coefficient is used as a p-type conductivity impurity. In addition, a semiconductor layer (hereinafter referred to as a diffusion prevention layer) that prevents the buried region from contacting the mesa stripe is provided between the buried region and the mesa stripe. According to this diffusion prevention layer, interdiffusion between the p-type conductivity impurity and the iron element is reduced.

  The semiconductor elements used in these elements inevitably require a diffusion prevention layer. However, there is a demand for an optical semiconductor device that does not use a diffusion prevention layer.

  Accordingly, the present invention has been made in view of the above matters, and an optical semiconductor device in which interdiffusion between p-type conductivity type impurities and iron atoms is reduced, and a method of manufacturing the optical semiconductor device. The purpose is to provide.

  According to one aspect of the present invention, an optical semiconductor device includes: (a) a semiconductor mesa provided on a substrate; and (b) a buried region provided on the substrate and embedding the semiconductor mesa. Includes a first cladding layer, a second cladding layer, and an active layer, and the active layer is provided between the first cladding layer and the second cladding layer, and the embedded The region includes a semiconductor layer to which at least an iron element is added, and the first cladding layer is made of a III-V compound semiconductor to which a carbon element is added and which contains an arsenic element.

  Since the carbon element is added to the first cladding layer of this optical semiconductor device and the iron element is added to the buried layer, the mutual diffusion of the carbon element and the iron element is reduced. The carrier concentration of the first cladding layer does not decrease. In addition, it is possible to suppress a decrease in resistance of the semiconductor layer to which iron in the embedded region is added. Furthermore, it is possible to suppress an increase in the resistance of the first cladding layer.

  According to another aspect of the present invention, an optical semiconductor device includes: (a) a semiconductor mesa provided on a substrate; and (b) a buried region provided on the substrate and embedding the semiconductor mesa. The mesa includes a first cladding layer, a second cladding layer, and an active layer, and the active layer is provided between the first cladding layer and the second cladding layer, The buried region includes at least a semiconductor layer to which an iron element is added, and the active layer includes a region of a III-V compound semiconductor to which a carbon element is added and which contains an arsenic element.

  Since the active layer of this optical semiconductor device includes a region of a III-V compound semiconductor containing arsenic element to which carbon element is added, interdiffusion of carbon element and iron element is reduced. The carrier concentration in the III-V compound semiconductor region does not decrease. In addition, it is possible to suppress a decrease in the resistance of the buried region. Furthermore, an increase in the resistance of the III-V compound semiconductor region can be suppressed. In this optical semiconductor device, since the active layer includes the semiconductor region to which the carbon element is added, the characteristics of the optical semiconductor device can be improved.

  According to still another aspect of the present invention, an optical semiconductor device includes: (a) a semiconductor mesa provided on a substrate; and (b) an embedded region provided on the substrate and embedding the semiconductor mesa. The semiconductor mesa includes a first cladding layer, a second cladding layer, an optical confinement layer, and an active layer, and the active layer is interposed between the first cladding layer and the second cladding layer. The buried region includes a semiconductor layer to which at least an iron element is added, and the optical confinement layer includes a III-V compound semiconductor to which a carbon element is added and which contains an arsenic element. Features.

  Since the carbon confinement layer is added to the optical confinement layer of this optical semiconductor device and the iron element is added to the buried layer, the mutual diffusion of the carbon element and the iron element is reduced. The carrier concentration of the optical confinement layer does not decrease. In addition, it is possible to suppress a decrease in the resistance of the buried region. Furthermore, it is possible to suppress an increase in the resistance of the optical confinement layer. According to the optical confinement layer to which the carbon element is added, the characteristics of the optical semiconductor device can be improved.

  In the optical semiconductor device of the present invention, the semiconductor layer in the buried region is preferably made of an InP semiconductor.

  Since the carbon element is added to the semiconductor layer of this optical semiconductor device, it is possible to suppress a decrease in the resistance of the InP semiconductor region to which the iron element is added.

  When a carbon element is added to the InP semiconductor, it shows n conductivity type. However, when a carbon element is added as an impurity to a III-V compound semiconductor containing an arsenic element as in the present invention, the carbon element exhibits a p-type conductivity type. This carbon element has a remarkably small diffusion coefficient compared with the zinc (Zn) element conventionally used as an impurity of a p-type conductivity type.

  In the optical semiconductor device of the present invention, the III-V compound semiconductor is preferably at least one of an AlGaInAs semiconductor and an AlInAs semiconductor.

  In this optical semiconductor device, when an AlGaInAs semiconductor layer and an AlInAs semiconductor layer are used, it is possible to prevent the dopant from diffusing into the buried region.

  The optical semiconductor device of the present invention further includes a third cladding layer provided on the first cladding layer and the buried region, and the third cladding layer includes an arsenic element to which a carbon element is added. It is preferable to consist of a III-V compound semiconductor.

  Since the carbon element is added to the third cladding layer of this optical semiconductor device, it is possible to suppress a decrease in the resistance of the buried region to which the iron element is added.

  In the optical semiconductor device of the present invention, it is preferable that the III-V compound semiconductor of the third cladding layer is at least one of an AlGaInAs semiconductor and an AlInAs semiconductor.

  In this optical semiconductor device, when an AlGaInAs semiconductor layer and an AlInAs semiconductor layer are used, it is possible to prevent the dopant from diffusing into the buried region.

  In the optical semiconductor device of the present invention, the active layer has a multiple quantum well structure including a well layer and a barrier layer, and the barrier layer is doped with an AlGaInAs semiconductor to which a carbon element is added and a carbon element. It is preferably made of at least one of AlInAs semiconductors.

  In this optical semiconductor device, since the barrier layer includes a semiconductor region to which a carbon element is added, high-speed operation characteristics of the optical semiconductor device can be improved.

  According to another aspect of the present invention, a method of manufacturing an optical semiconductor device includes: (a) forming a III-V compound semiconductor layer to which a carbon element is added using a halogen compound containing a carbon element; And (b) forming a buried region to which an iron element is added after the step of forming the III-V compound semiconductor layer, wherein the III-V compound semiconductor layer includes an AlGaInAs semiconductor layer and an AlInAs semiconductor layer. At least one of them.

  In this method, since the buried region to which the iron element is added is formed on the semiconductor layer to which the carbon element is added, it is possible to suppress a decrease in the resistance of the buried region to which the iron element is added.

  According to still another aspect of the present invention, a method of manufacturing an optical semiconductor device includes: (a) a step of forming a buried region to which an iron element is added; and (b) a carbon after forming the buried region. A step of forming a III-V compound semiconductor layer to which a carbon element is added using a halogen compound containing an element, wherein the III-V compound semiconductor layer is at least one of an AlGaInAs semiconductor layer and an AlInAs semiconductor layer .

  In this method, since the semiconductor layer to which the carbon element is added is formed on the buried region to which the iron element is added, it is possible to suppress a decrease in the resistance of the buried region to which the iron element is added.

As described above, according to the present invention, an optical semiconductor device in which interdiffusion between p-type conductivity impurities and iron is reduced is provided, and a method for manufacturing the optical semiconductor device is provided. .

  The above and other objects, features, and advantages of the present invention will become more readily apparent from the following detailed description of preferred embodiments of the present invention, which proceeds with reference to the accompanying drawings.

  The knowledge of the present invention can be easily understood by considering the following detailed description with reference to the accompanying drawings shown as examples. Subsequently, embodiments of the optical semiconductor device and the method for manufacturing the optical semiconductor device of the present invention will be described with reference to the accompanying drawings. Where possible, the same parts are denoted by the same reference numerals.

(First embodiment)
FIG. 1 is a cross-sectional view showing an optical semiconductor device according to the present embodiment. The optical semiconductor device 1 includes a carbon-doped first cladding layer 3, a second cladding layer 5, an active layer 7, and a buried region 9. The active layer 7 is provided between the first cladding layer 3 and the second cladding layer 5. The embedded region 9 is provided so as to embed a semiconductor mesa. The semiconductor mesa includes a first cladding layer 3, a second cladding layer 5, and an active layer 7. The buried region 9 includes an iron-doped III-V compound semiconductor layer 11. In the iron-doped III-V compound semiconductor layer 11, the iron-doped III-V compound semiconductor layer 11 has a high resistance, and can confine current in, for example, the active layer 7b. Since the first cladding layer 3 of the optical semiconductor device 1 is carbon-doped, it is possible to suppress a decrease in the resistance of the iron-doped III-V compound semiconductor layer 11.

  Since the first cladding layer 3 of this optical semiconductor device is doped with carbon element and the buried layer 9 is doped with iron element, mutual diffusion of carbon element and iron element is reduced. Since the diffusion of the iron element into the first cladding layer 3 can be reduced, the carrier concentration of the first cladding layer 3 does not decrease. Moreover, since the fall of the carbon concentration of the 1st cladding layer 3 is suppressed, it can suppress that the resistance of the 1st cladding layer 3 raises. Further, the diffusion of the iron element from the semiconductor layer 11 in the buried region 9 can be reduced and the diffusion of the carbon element from the first cladding layer 3 can be suppressed, so that the resistance of the buried region 9 can be prevented from decreasing. .

  In one embodiment, the first cladding layer 3 is made of a p-type III-V compound semiconductor, the second cladding layer 5 is made of an n-type III-V compound semiconductor, and the active layer 7 is made of an undoped III-V compound semiconductor. Become. In the optical semiconductor device 1 of the preferred embodiment, the iron-doped III-V compound semiconductor layer 11 in the buried region 9 preferably includes an iron-doped InP layer. Since the first cladding layer of this optical semiconductor device is carbon-doped, it is possible to suppress a decrease in resistance to the iron-doped InP layer. In the optical semiconductor device 1 of the preferred embodiment, the first cladding layer 3 can be made of a III-V compound semiconductor doped with carbon element and containing arsenic element.

  The optical semiconductor device 1 includes a support base 13. The first cladding layer 3, the second cladding layer 5, the active layer 7 and the buried region 9 are provided on the support base 13. For example, an InP semiconductor substrate or a GaAs semiconductor substrate can be used as the support base 13, but the present invention is not limited to this. The active layer 7 can be made of an InGaAsP semiconductor. The active layer 7 may have a quantum well structure, and the quantum well structure includes, for example, a well layer made of InGaAsP semiconductor and a barrier layer made of InGaAsP semiconductor.

  In the optical semiconductor device 1 of one embodiment, the first cladding layer 3, the second cladding layer 5, the active layer 7 and the buried region 9 have a mesa shape provided on the support base 13, for example, The mesa 17 can have a stripe shape. The width of the stripe is, for example, about 1.5 micrometers.

  In the optical semiconductor device 1, the first cladding layer 3 is preferably made of a III-V compound semiconductor containing arsenic (As), and carbon serves as a p-type dopant. In a preferred embodiment, the first cladding layer 3 can be made of, for example, at least one of an AlGaInAs semiconductor, an AlInAs semiconductor, and an InGaAsP semiconductor. These semiconductor materials can provide optical confinement and a potential barrier to the active layer 7, and carbon acts as a p-type dopant. Thereby, it is possible to prevent the resistance of the buried region 9 from being lowered due to the diffusion of the p-type dopant in the first cladding layer 3.

  The optical semiconductor device 1 can further include a third cladding layer 19, and the third cladding layer 19 is provided on the first cladding layer 3 and the buried region 9. The third cladding layer 19 is provided to confine light in the active layer. The conductivity type of the third cladding layer 19 is the same as the conductivity type of the first cladding layer 3.

  The optical semiconductor device 1 can further include a contact layer 21. The third cladding layer 19 is provided between the contact layer 21 and the buried region 9 and the mesa 17. In a preferred embodiment, the contact layer 21 has a band gap that is smaller than the band gap of the third cladding layer 21. Further, a dopant is added to the contact layer 21 at a high concentration, and the dopant concentration of the contact layer 21 is higher than the dopant concentration of the third cladding layer 21. The contact layer 21 is preferably doped with carbon. The contact layer 21 is preferably made of a III-V compound semiconductor containing arsenic, and a carbon dopant serves as a p-type dopant.

  In the optical semiconductor device 1, the buried region 9 can include a semiconductor layer 23 provided between the buried layer 11 and the third cladding layer 19. The semiconductor layer 23 has a conductivity type different from that of the third cladding layer 19 and is provided to prevent carriers (holes) flowing from the p-type cladding layer 19 into the buried layer 11.

  In the optical semiconductor device 1, the mesa region 25, the cladding layer 19, and the contact layer 21 have a mesa shape provided on the support base 13. For example, the mesa region 25 has a stripe shape. Can do. The width of the stripe of the mesa 25 is, for example, about 10 micrometers.

  The optical semiconductor device 1 can include an insulating film 26 provided on one surface 13 a of the support base 13 and the mesa 25. For example, the insulating film 26 may be made of an insulating silicon inorganic compound.

  The optical semiconductor device 1 can have an electrode 27 electrically connected to the contact layer 21. The electrode 27 is in ohmic contact with the contact layer 21 through the opening of the insulating film 26. The optical semiconductor device 1 also has an electrode 31 provided on another surface 13 b of the support base 13.

  As described above, according to the optical semiconductor device 1 of the present embodiment, there is provided an optical semiconductor device in which interdiffusion between p-type conductivity impurities and iron atoms is reduced without using a diffusion prevention layer. The

  FIG. 2 is a drawing showing an optical semiconductor device according to another embodiment. The optical semiconductor device 1 a has a third cladding layer 29 instead of the third cladding layer 19. The third cladding layer 29 is preferably made of a III-V compound semiconductor containing arsenic (not containing phosphorus as a constituent element). The carbon dopant acts as a p-type dopant in the arsenic III-V compound semiconductor.

  Since the third cladding layer 29 of this optical semiconductor device is doped with carbon element and the buried layer 9 is doped with iron element, the mutual diffusion of carbon element and iron element is reduced. Since the diffusion of the iron element into the third cladding layer 29 can be reduced, the carrier concentration of the third cladding layer 29 does not decrease. In addition, since the decrease in the carbon concentration of the third cladding layer 29 is suppressed, it is possible to suppress an increase in the resistance of the third cladding layer 29. Further, the diffusion of the iron element from the semiconductor layer 11 in the buried region 9 can be reduced and the diffusion of the carbon element from the third cladding layer 29 can be suppressed, so that the resistance of the buried region 9 can be prevented from decreasing. .

As an example,
First cladding layer 3: p-type AlGaInAs semiconductor (carbon doped)
Carrier concentration: 5 × 10 17 cm −3
Second cladding layer 5: n-type InP semiconductor (silicon doped)
Carrier concentration: 8 × 10 17 cm −3
Active layer 7: MQW of GaInAsP / GaInAsP
Buried layer 11: iron-doped InP
Thickness: about 1.5 micrometers Semiconductor layer 23: Silicon-doped InP semiconductor
Carrier concentration: 2 × 10 18 cm −3
Thickness: about 0.2 micrometers Third cladding layer 29: p-type AlInAs semiconductor (carbon doped)
Carrier concentration: 1 × 1018 cm−3
Thickness: about 1.5 micrometers Support base 13: n-type InP single crystal substrate contact layer 21: carbon-doped GaInAs semiconductor
Carrier concentration: 1 x 1020 cm-3
Thickness: about 0.5 micrometer insulating film 26: silicon oxide electrode 27: anode electrode electrode 31: cathode electrode.

  FIG. 3 shows an optical semiconductor device in which a p-type cladding layer is added with a zinc dopant. In the optical semiconductor device 41, an InGaAsP active layer 47 is provided between the zinc-doped InP semiconductor layer 43 and the silicon-doped InP semiconductor layer 45. The buried region 49 includes an iron-doped InP layer 51 and a silicon-doped InP semiconductor layer 53. The first cladding layer 43 is doped with zinc. Since zinc added to the zinc-doped InP semiconductor layer 43 diffuses into the iron-doped InP layer 51, the resistance of the iron-doped InP layer 51 decreases. Further, the iron dopant in the InP layer 51 diffuses into the p-type InP semiconductor layer 43 due to the diffusion of zinc. Due to these mutual diffusions, the resistance of the iron-doped InP layer 51 is further reduced. The InP semiconductor layer 55 is also doped with zinc. Since zinc added to the InP semiconductor layer 55 diffuses into the iron-doped InP layer 51, the resistance of the iron-doped InP layer 51 decreases.

  As described above, according to the optical semiconductor device 1a of the present embodiment, an optical semiconductor device is provided in which interdiffusion between p-type conductivity impurities and iron atoms is reduced without using a diffusion prevention layer. The

(Second Embodiment)
FIG. 4A illustrates an optical semiconductor device according to the second embodiment. The optical semiconductor device 1b includes an optical confinement (SCH) layer 33a. The optical confinement layer 33 a is provided between the active layer 7 b and the first cladding layer 3. The optical confinement layer 33a can be made of a III-V compound semiconductor in which carbon is doped in part or in whole. In the optical semiconductor device 1b shown in FIG. 4A, the layered region is doped with carbon.

  Similar to the optical semiconductor device 1, in the optical semiconductor device 1 b, the active layer 7 b is provided between the first cladding layer 3 and the second cladding layer 5. The embedded region 9 is provided so as to embed a semiconductor mesa. This semiconductor mesa includes a first cladding layer 3, a second cladding layer 5, an optical confinement layer 33a, and an active layer 7b. The buried region 9 includes an iron-doped III-V compound semiconductor layer 11. The iron-doped III-V compound semiconductor layer 11 has a high resistance, and can confine a current in, for example, the active layer 7b.

  Since the optical confinement layer 33a of this optical semiconductor device is doped with carbon element, and the buried region 9 is doped with iron element, the mutual diffusion of carbon element and iron element is reduced. Since the diffusion of the iron element into the light confinement layer 33a can be reduced, the carrier concentration of the light confinement layer 33a does not decrease. Moreover, since the fall of the carbon concentration of the light confinement layer 33a is suppressed, it can suppress that resistance of the light confinement layer 33a raises. Furthermore, the diffusion of the iron element from the semiconductor layer 11 in the buried region 9 can be reduced, and the diffusion of the carbon element from the light confinement layer 33a can be suppressed, so that the resistance of the buried region 9 can be prevented from decreasing.

  According to the light confinement layer 33a to which this carbon element is added, the characteristics of the optical semiconductor device 1b can be improved.

  In a preferred embodiment, in a preferred embodiment, the optical confinement layer 33a can include a region of a III-V compound semiconductor doped with a carbon element. This III-V compound semiconductor region is a III-V compound semiconductor containing an arsenic element. The optical confinement layer 33a is preferably made of, for example, at least one of a carbon-doped AlGaInAs semiconductor and a carbon-doped AlInAs semiconductor. According to the carbon-doped optical confinement layer 33a, in the optical semiconductor device 1b, the electrical resistance of the path through which carriers (for example, holes) flow to the active layer 3b can be reduced. In addition, heat generated by the optical semiconductor device 1b can be reduced. The optical semiconductor device 1 b can further include an optical confinement layer 33 b provided between the active layer 3 b and the second cladding layer 5. The active layer 3b includes well layers 35a, 35b, 35c, 35d and barrier layers 37a, 37b, 37c, 37d, 37d, 37e. The well layers 35a to 35d and the barrier layers 37a to 37e are alternately arranged.

  As shown in FIG. 4A, if the optical semiconductor device 1b has the first cladding layer 3 to which the carbon element is added, the iron atoms and the first cladding contained in the buried region 9 The interdiffusion of carbon atoms in the layer 3 is reduced. Since the diffusion of the iron element into the first cladding layer 3 can be reduced, the carrier concentration of the first cladding layer 3 does not decrease. Moreover, since the fall of the carbon concentration of the 1st cladding layer 3 is suppressed, it can suppress that the resistance of the 1st cladding layer 3 raises. Further, the diffusion of the iron element from the semiconductor layer 11 in the buried region 9 can be reduced and the diffusion of the carbon element from the first cladding layer 3 can be suppressed, so that the resistance of the buried region 9 can be prevented from decreasing. .

  Similar to the optical semiconductor device 1, the optical semiconductor device 1 b can include, for example, a semiconductor layer 23, a third cladding layer 29, a support base 13, a contact layer 21, and an insulating film 26. The electrode 27 and the electrode 31 can be provided.

  As described above, according to the optical semiconductor device 1b of the present embodiment, an optical semiconductor device in which interdiffusion between p-type conductivity type impurities and iron atoms is reduced without using a diffusion prevention layer is provided. The

(Third embodiment)
FIG. 4B is a diagram illustrating an example of an optical semiconductor device according to the third embodiment. Similar to the optical semiconductor device 1, in the optical semiconductor device 1 c, the active layer 7 b is provided between the first cladding layer 3 and the second cladding layer 5. The buried region 9 is provided so as to bury a semiconductor mesa including the first cladding layer 3, the second cladding layer 5, and the active layer 7b. The buried region 9 includes an iron-doped III-V compound semiconductor layer 11. The iron-doped III-V compound semiconductor layer 11 has a high resistance, and can confine a current in, for example, the active layer 7b. The active layer 7c of the optical semiconductor device 1c can include a region of a III-V compound semiconductor to which a carbon element is added. The active layer 7c of this optical semiconductor device includes a semiconductor region to which a carbon element is added, and since the iron element is added to the buried layer, the mutual diffusion of the carbon element and the iron element is reduced. The carrier concentration of the semiconductor layer in the active layer 7c does not decrease. In addition, it is possible to suppress a decrease in the resistance of the buried region. Furthermore, it is possible to suppress an increase in resistance of the semiconductor layer in the active layer 7c.

  In a preferred embodiment, the active layer 7c may include at least one of an AlGaInAs semiconductor region to which carbon element is added and an AlInAs semiconductor region to which carbon element is added.

  As shown in FIG. 4B, the active layer 3c has a multiple quantum well structure. The active layer 3c includes well layers 45a, 45b, 45c, 45d and barrier layers 47a, 47b, 47c, 47d, 47d, 47e arranged between the first cladding layer 3 and the second cladding layer 5. . The well layers 45a to 45d and the barrier layers 47a to 47e are alternately arranged. The well layers 45a to 45d are formed to be undoped semiconductor layers. At least one of the barrier layers 47a to 47e is preferably doped with carbon. In a preferred embodiment, all barrier layers 47a to 47e are doped with carbon, as in the optical semiconductor device 1c shown in FIG. 4B. By adding carbon to some or all of the barrier layers 47a to 47e, the differential gain is improved, the relaxation oscillation frequency is increased, and the resistance of the buried region is suppressed from decreasing.

  The optical semiconductor device 1c can include an optical confinement layer 49a provided between the first cladding layer 3 and the active layer 3c, and is provided between the second cladding layer 5 and the active layer 3c. The optical confinement layer 49b may be included. In the preferred embodiment, some or all of the light confinement layer 49a is doped with carbon. In addition, the optical semiconductor device 1c can include an optical confinement layer 49a doped with carbon in part or in whole, thereby reducing heat generation of the optical semiconductor device.

  Further, as shown in FIG. 4B, if the optical semiconductor device 1c has the first cladding layer 3 to which the carbon element is added, the iron atoms contained in the buried region 9 and the first Interdiffusion of carbon atoms in the cladding layer 3 is reduced. Since the diffusion of the iron element into the first cladding layer 3 can be reduced, the carrier concentration of the first cladding layer 3 does not decrease. Moreover, since the fall of the carbon concentration of the 1st cladding layer 3 is suppressed, it can suppress that the resistance of the 1st cladding layer 3 raises. Further, the diffusion of the iron element from the semiconductor layer 11 in the buried region 9 can be reduced and the diffusion of the carbon element from the first cladding layer 3 can be suppressed, so that the resistance of the buried region 9 can be prevented from decreasing. .

  Similar to the optical semiconductor device 1, the optical semiconductor device 1 c can include, for example, the semiconductor layer 23, the third cladding layer 29, the support base 13, and the contact layer 21, and further includes the insulating film 26. The electrode 27 and the electrode 31 can be provided.

  Although some embodiments have already been described, it is also possible to obtain modified optical semiconductor devices that combine these embodiments. For example, an optical semiconductor device according to one modified example has optical confinement doped with carbon. And a barrier layer doped with carbon.

  As described above, according to the optical semiconductor device 1c of the present embodiment, there is provided an optical semiconductor device in which interdiffusion between p-type conductivity impurities and iron atoms is reduced without using a diffusion prevention layer. The

(Fourth embodiment)
FIG. 5A, FIG. 5B, and FIG. 5C are drawings showing a method of manufacturing an optical semiconductor device according to the second embodiment. 6 (A), 6 (B), and 6 (c) are drawings showing a method of manufacturing an optical semiconductor device according to the second embodiment. FIGS. 7A and 7B are views showing a method of manufacturing an optical semiconductor device according to the second embodiment.

  As shown in FIG. 5A, a substrate 51 is prepared. The substrate 51 can be a III-V compound semiconductor substrate, for example, an n-type InP substrate. Next, a plurality of III-V compound semiconductor films are formed on the main surface 51 a of the substrate 51. This formation is performed using, for example, a metal organic chemical vapor deposition method. In this embodiment, an n-type III-V compound semiconductor film 53, an active layer 55, and a carbon-doped III-V arsenic compound semiconductor film 57 are sequentially deposited on the substrate 51. The n-type III-V compound semiconductor film 53 can be, for example, a silicon-doped InP semiconductor film, the active layer 55 can be an undoped InGaAsP semiconductor film 55, and the III-V arsenic compound semiconductor film 57 can be, for example, The p-type AlGaInAs semiconductor film and the p-type AlInAs semiconductor film can be at least one of them. The carbon-doped III-V arsenic compound semiconductor film 57 can be formed using a halogen compound containing a carbon element such as CBr4 as a dopant source. The characteristics of this halogen compound (including CBr4) are, for example, as follows. Good control of carbon concentration. The concentration can be controlled from a low concentration to a high concentration. It is possible to add a high concentration of carbon. CBr4 is suitable for forming a high-concentration p-conductivity type carbon-doped AlGaInAs semiconductor film and carbon-doped AlInAs semiconductor film. The oxygen concentration of this film is lower than that of a film formed using a zinc dopant.

  As shown in FIG. 5B, a mask layer 59 for forming a mesa is formed. The mask layer 59 can be made of an insulating film such as a silicon nitride film. Using the mask layer 59, the carbon-doped III-V compound semiconductor film 57, the undoped InGaAsP semiconductor film 55, and the n-type III-V compound semiconductor film 53 are sequentially etched to obtain a carbon-doped III-V arsenic compound semiconductor layer 57a, An active layer 55a and an n-type III-V compound semiconductor layer 53a are formed. As a result, the mesa 60 including the carbon-doped III-V arsenic compound semiconductor layer 57a, the active layer 55a, and the n-type III-V arsenic compound semiconductor layer 53a is formed.

  As shown in FIG. 5C, an iron-doped buried layer 61 is formed on the semiconductor surface using a mask layer 59. As a result, an iron-doped first buried film 61 is formed on the carbon-doped III-V arsenic compound semiconductor layer 57a, and is also formed on the active layer 55a, the n-type III-V compound semiconductor layer 53a, and the substrate 51. The Next, a silicon-doped second buried film 63 is formed. The second buried film 63 can be, for example, an n-type InP semiconductor film. The iron-doped buried film 61 can be, for example, an iron-doped InP semiconductor film. Thereafter, the mask layer 59 is removed.

  In this method, since the iron-doped buried film 61 is formed on the carbon-doped semiconductor layer 57a, the resistance of the iron-doped buried film 61 can be suppressed from decreasing.

  As shown in FIG. 6A, after the silicon-doped second buried film 63 is formed, the carbon-doped III-V compound semiconductor film 65 is formed on the silicon-doped second buried film 63 using CBr4. To form. As the III-V compound semiconductor film 65, for example, at least one of an AlGaInAs semiconductor film and an AlInAs semiconductor film can be used.

  In this method, since the carbon-doped III-V compound semiconductor film 65 is formed on the iron-doped buried film, it is possible to suppress a decrease in the resistance of the iron-doped buried film.

  Next, another p-type III-V compound semiconductor film 67 for forming a contact layer is formed on the III-V compound semiconductor film 65. The III-V compound semiconductor film 67 can be doped with, for example, carbon, and can be, for example, a GaInAs semiconductor film.

  As shown in FIG. 6B, a mask layer 69 for forming a mesa is formed. The mask layer 69 can be made of an insulating film such as a silicon nitride film. Using the mask layer 69, the p-type III-V compound semiconductor film 67, the carbon-doped III-V compound semiconductor film 65, the second buried film 63 and the first buried film 61 are sequentially etched to form the p-type III A -V compound semiconductor layer 67a, a carbon-doped III-V compound semiconductor layer 65a, a second buried layer 63a, and a first buried layer 61a are formed. Thus, the mesa 70 including the p-type III-V compound semiconductor layer 67a, the carbon-doped III-V compound semiconductor layer 65a, the second buried layer 63a, the first buried layer 61a, and the mesa 60 is formed. Thereafter, the mask layer 69 is removed.

  As shown in FIG. 7A, an insulating film 71 is formed over the mesa 70 and the substrate 51. As the insulating film 71, for example, a silicon oxide film can be used.

  As shown in FIG. 7B, an electrode 73 is formed after an opening is formed in the insulating film 71 over the mesa 70. The electrode 73 is formed on the insulating film 71 and the opening 71a. In addition, an electrode 75 is formed on the back surface of the substrate 51. Based on the above method, the optical semiconductor device described in the first to third embodiments can be manufactured.

  As described above, according to the method of manufacturing the optical semiconductor device of the present embodiment, an optical semiconductor device in which interdiffusion of p-type dopant and iron atoms is reduced without using a diffusion prevention layer is formed. .

  In an optical semiconductor device such as a semiconductor laser for communication, the cladding material is an InP semiconductor, and carbon does not act as a p-type dopant in the InP semiconductor. In the optical semiconductor device and the manufacturing method thereof according to the present embodiment, since the carbon-doped semiconductor region is in contact with the iron-doped p-type semiconductor region, as a result, the diffusion distance of the carbon dopant is small. Moreover, mutual diffusion between zinc and iron does not occur.

  In the optical semiconductor device and the manufacturing method thereof according to the present embodiment, the case where an InP substrate is used as the III-V compound semiconductor substrate has been described, but a GaAs substrate may be used. When a GaAs substrate is used, the carbon-doped III-V arsenic compound semiconductor layer can be, for example, an AlGaAs semiconductor film. The iron-doped buried film can be a GaInP semiconductor film.

  While the principles of the invention have been illustrated and described in the preferred embodiments, it will be appreciated by those skilled in the art that the invention can be modified in arrangement and detail without departing from such principles. The present invention is not limited to the specific configuration disclosed in the present embodiment, and an optical semiconductor device according to the present invention includes, for example, a laser diode, a semiconductor optical amplifier, a semiconductor optical modulator, a semiconductor optical switch, and a semiconductor optical switch. It can be used for an optical semiconductor integrated device. Further, the optical semiconductor device according to the present invention may be a surface emitting optical semiconductor device such as a light emitting diode and a vertical cavity semiconductor light emitting element. We therefore claim all modifications and changes that come within the scope and spirit of the following claims.

FIG. 1 is a cross-sectional view showing an optical semiconductor device according to the present embodiment. FIG. 2 is a view showing a modification of the optical semiconductor device according to the first embodiment. FIG. 3 shows an optical semiconductor device in which a p-type cladding layer is added with a zinc dopant. FIG. 4A and FIG. 4B are drawings showing a modification of the optical semiconductor device according to the present embodiment. FIG. 5A, FIG. 5B, and FIG. 5C are drawings showing a method of manufacturing an optical semiconductor device according to the second embodiment. 6A and 6B are diagrams illustrating a method of manufacturing an optical semiconductor device according to the second embodiment. FIGS. 7A and 7B are views showing a method of manufacturing an optical semiconductor device according to the second embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1a, 1b, 1c ... Optical semiconductor device, 3 ... 1st clad layer, 5 ... 2nd clad layer, 7 ... Active layer, 11 ... Embedded layer, 13 ... Support base | substrate, 23 ... III-V compound semiconductor Layer 29... Third cladding layer 13 support substrate 17 25 mesa 21 contact layer 23 III-V compound semiconductor layer 27 insulating film 27 anode electrode 31 cathode electrode 51 ... substrate, 53 ... n-type III-V arsenic compound semiconductor film, 55 ... active layer, 57 ... carbon-doped III-V arsenic compound semiconductor film, 59 ... mask layer, 57a ... carbon-doped III-V arsenic compound semiconductor layer, 55a ... Active layer, 53a ... n-type III-V compound semiconductor layer, 60 ... mesa, 61 ... iron-doped buried film, 61a ... first buried layer, 63 ... second buried film, 63a ... second buried layer , 65 ... III-V conversion of carbon dope Semiconductor semiconductor film, 65a ... carbon-doped III-V compound semiconductor layer, 67 ... p-type III-V compound semiconductor film, 67a ... p-type III-V compound semiconductor layer, 69 ... mask layer, 70 ... mesa, 71 ... insulation Membrane 73 ... Electrode 75 ... Electrode

Claims (10)

A semiconductor mesa provided on the substrate;
An embedded region provided on the substrate and embedded in the semiconductor mesa,
The semiconductor mesa includes a first cladding layer, a second cladding layer, and an active layer,
The active layer is provided between the first cladding layer and the second cladding layer,
The buried region includes a semiconductor layer to which at least an iron element is added,
An optical semiconductor device, wherein the first cladding layer is made of a III-V compound semiconductor to which a carbon element is added and which contains an arsenic element. A semiconductor mesa provided on the substrate;
An embedded region provided on the substrate and embedded in the semiconductor mesa,
The semiconductor mesa includes a first cladding layer, a second cladding layer, and an active layer,
The active layer is provided between the first cladding layer and the second cladding layer,
The buried region includes a semiconductor layer to which at least an iron element is added,
The active layer includes a region of a III-V compound semiconductor to which an elemental carbon is added and which contains an arsenic element. A semiconductor mesa provided on the substrate;
An embedded region provided on the substrate and embedded in the semiconductor mesa,
The semiconductor mesa includes a first cladding layer, a second cladding layer, an optical confinement layer, and an active layer,
The active layer is provided between the first cladding layer and the second cladding layer,
The buried region includes a semiconductor layer to which at least an iron element is added,
The optical confinement layer is made of a III-V compound semiconductor to which an elemental carbon is added and which contains an arsenic element.   4. The optical semiconductor device according to claim 1, wherein the semiconductor layer in the buried region is made of an InP semiconductor.   5. The optical semiconductor device according to claim 1, wherein the III-V compound semiconductor is at least one of an AlGaInAs semiconductor and an AlInAs semiconductor. A third clad layer provided on the first clad layer and the buried region;
The third clad layer according to any one of claims 1 to 4, wherein the third cladding layer is made of a III-V compound semiconductor to which an elemental carbon is added and which contains an arsenic element. Optical semiconductor device.   The optical semiconductor device according to claim 6, wherein the III-V compound semiconductor of the third cladding layer is at least one of an AlGaInAs semiconductor and an AlInAs semiconductor. The active layer has a multiple quantum well structure including a well layer and a barrier layer,
8. The light according to claim 1, wherein the barrier layer is made of at least one of an AlGaInAs semiconductor to which a carbon element is added and an AlInAs semiconductor to which a carbon element is added. Semiconductor device. A method of manufacturing an optical semiconductor device, comprising:
Forming a III-V compound semiconductor layer to which a carbon element is added using a halogen compound containing a carbon element;
Forming a buried region to which an iron element is added after the step of forming the III-V compound semiconductor layer,
The III-V compound semiconductor layer is at least one of an AlGaInAs semiconductor layer and an AlInAs semiconductor layer. A method of manufacturing an optical semiconductor device, comprising:
Forming a buried region doped with iron element;
Forming a III-V compound semiconductor layer to which a carbon element is added using a halogen compound containing a carbon element after forming the buried region;
The III-V compound semiconductor layer is at least one of an AlGaInAs semiconductor layer and an AlInAs semiconductor layer.

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