Optical devices

Abstract

This optical device comprises: a semiconductor layer (102) which is constituted by a group III-V compound semiconductor and which is formed on a cladding layer (101); and a light-receiving element (152) which is formed on the semiconductor layer (102) and which is for monitoring a semiconductor laser (151) and the oscillation light of the semiconductor laser (151). The following are constituted from the same group III-V compound semiconductor (InGaAsp): a first p-contact layer (106) and a first n-contact layer (107) of the semiconductor laser (151); and a second p-contact layer (114), a second n-contact layer (115), and a light absorbing layer (118) of the light receiving element (152).

Description

Technical Field

[0001] The present invention relates to an optical device including a light-emitting element and a light-receiving element.

Background Art

[0002] Due to the explosive increase in network traffic volume accompanying the spread of the Internet, the high speed and large capacity of optical fiber transmission have been continuously improved. In optical devices such as optical transceivers used in optical communication, waveguide-type semiconductor lasers are used and have continued to develop as light source devices supporting optical fiber communication. In this type of optical device, a waveguide-type light-receiving element for monitoring the output light of the semiconductor laser is integrated. In such a light-receiving element for monitoring, it is important to form an absorption layer from a compound semiconductor having a high absorption coefficient in the communication wavelength band.

[0003] On the other hand, since the light-receiving element is integrated with the light-emitting element, in an optical waveguide structure having an absorption layer as a core, it is preferable in terms of manufacturing to use the compound semiconductor constituting the light-emitting element as the core material. However, the compound semiconductor constituting the light-emitting element naturally has a high transmittance in the communication wavelength band and is not suitable for the light-receiving element. The compound semiconductor used for the active layer of the semiconductor laser has a lower absorption coefficient in the C band and the O band than the compound semiconductor used for the light absorption layer of the light-receiving element, and high light-receiving sensitivity cannot be obtained.

[0004] Therefore, in the portion of the light-receiving element, once the layer of the compound semiconductor for forming the light-emitting element is removed, and a compound semiconductor layer having a high absorption coefficient in the communication wavelength band is formed again. Also, the integration of the light-emitting element and the light-receiving element is realized by so-called hybrid integration.

Prior Art Documents

Non-Patent Documents

[0005]

Non-Patent Document 1

[0006] However, the conventional manufacturing method described above had the problem of high costs associated with integrating the light-emitting element and the light-receiving element.

[0007] This invention was made to solve the above-mentioned problems, and aims to enable the integration of a light-emitting element and a light-receiving element without increasing costs. [Means for solving the problem]

[0008] The optical device according to the present invention comprises a semiconductor layer made of a III-V compound semiconductor formed on a cladding layer, a waveguide-type semiconductor laser formed on the semiconductor layer, and a waveguide-type photodetector for monitoring the oscillating light of the semiconductor laser, wherein the semiconductor laser comprises a core-shaped active layer embedded in the semiconductor layer and extending in a predetermined direction, a p-type first p semiconductor region and an n-type first n semiconductor region formed on the active layer of the semiconductor layer, a first p electrode formed on the first p semiconductor region, a first n electrode formed on the first n semiconductor region, and a portion formed between the first p semiconductor region and the first p electrode. The photodetector comprises a first p contact layer and a first n contact layer formed between a first n semiconductor region and a first n electrode, and the photodetector comprises a non-doped i semiconductor region formed in the semiconductor layer and extending in a predetermined direction, a p-type second p semiconductor region and an n-type second n semiconductor region formed in the semiconductor layer on either side of the i semiconductor region, a second p electrode formed on the second p semiconductor region, a second n electrode formed on the second n semiconductor region, a second p contact layer formed between the second p semiconductor region and the second p electrode, a second n contact layer formed between the second n semiconductor region and the second n electrode, and on the i semiconductor region Contact The device comprises a formed light-absorbing layer, and the first p-contact layer, first n-contact layer, second p-contact layer, second n-contact layer, and light-absorbing layer are composed of the same III-V compound semiconductor. [Effects of the Invention]

[0009] As described above, according to the present invention, the first p-contact layer and first n-contact layer of the semiconductor laser, the second p-contact layer and second n-contact layer of the photodetector, and the light-absorbing layer are made from the same III-V compound semiconductor, so that the light-emitting element and the photodetector can be integrated without increasing costs. [Brief explanation of the drawing]

[0010] [Figure 1A] Figure 1A is a plan view showing the configuration of an optical device according to Embodiment 1 of the present invention. [Figure 1B]Figure 1B is a cross-sectional view showing a partial configuration of an optical device according to Embodiment 1 of the present invention. [Figure 1C] Figure 1C is a cross-sectional view showing a partial configuration of an optical device according to Embodiment 1 of the present invention. [Figure 1D] Figure 1D is a distribution diagram showing the distribution of light intensity in the photodetector 152 of the optical device according to Embodiment 1 of the present invention. [Figure 2A] Figure 2A is a cross-sectional view showing a partial configuration of an optical device according to Embodiment 2 of the present invention. [Figure 2B] Figure 2B is a distribution diagram showing the distribution of light intensity in the photodetector element 152a of the optical device according to Embodiment 2 of the present invention. [Figure 3A] Figure 3A is a cross-sectional view showing a partial configuration of an optical device according to Embodiment 3 of the present invention. [Figure 3B] Figure 3B is a distribution diagram showing the distribution of light intensity in the photodetector element 152b of the optical device according to Embodiment 3 of the present invention. [Figure 4A] Figure 4A is a cross-sectional view showing a partial configuration of an optical device according to Embodiment 4 of the present invention. [Figure 4B] Figure 4B is a distribution diagram showing the distribution of light intensity in the photodetector element 152c of the optical device according to Embodiment 4 of the present invention. [Figure 5A] Figure 5A is a cross-sectional view showing a partial configuration of another optical device according to an embodiment of the present invention. [Figure 5B] Figure 5B is a distribution diagram showing the distribution of light intensity in the photodetector element 152d of another optical device according to an embodiment of the present invention. [Figure 6A] Figure 6A is a cross-sectional view showing a partial configuration of another optical device according to an embodiment of the present invention. [Figure 6B] Figure 6B is a distribution diagram showing the distribution of light intensity in the photodetector element 152e of another optical device according to an embodiment of the present invention. [Modes for carrying out the invention]

[0011] Hereinafter, an optical device according to an embodiment of the present invention will be described.

[0012] [Embodiment 1] First, an optical device according to Embodiment 1 of the present invention will be described with reference to FIGS. 1A, 1B, 1C, and 1D. Note that FIG. 1 C shows a cross section taken along line aa' of FIG. 1A. Also, FIG. 1 B shows a cross section taken along line bb' of FIG. 1A.

[0013] This optical device includes a semiconductor layer 102 made of a III-V compound semiconductor formed on a cladding layer 101, and a semiconductor laser 151 formed in the semiconductor layer 102 and a light receiving element 152 for monitoring the oscillation light of the semiconductor laser 151. Each of the semiconductor laser 151 and the light receiving element 152 has a waveguide type. Also, the semiconductor laser 151 and the light receiving element 152 are optically connected by a connecting optical waveguide 153.

[0014] The semiconductor laser 151 is, for example, a well-known laterally current-injected type semiconductor laser, and first includes a core-shaped active layer 103 embedded in a semiconductor layer 102 made of a III-V compound semiconductor such as InP. The active layer 103 can be composed of, for example, InGaAs. Also, the active layer 103 can have a multiple quantum well structure. ]>

[0015] Further, the optical waveguide formed by the active layer 103 includes a p-type first p semiconductor region 104 and an n-type first n semiconductor region 105 formed so as to sandwich the active layer 103 in a direction perpendicular to the waveguide direction. In this example, the first p semiconductor region 104 and the first n semiconductor region 105 are arranged in a state of sandwiching the active layer 103 in a direction parallel to the plane of the cladding layer 101 (laterally current-injected type). <(

[0016] The first p-semiconductor region 104 is composed of a III-V compound semiconductor (InP) doped with p-type impurities, and the first n-semiconductor region 105 is composed of a III-V compound semiconductor (InP) doped with n-type impurities. These are formed by doping the semiconductor layer 102 with the corresponding impurities. The region of the semiconductor layer 102 in which the active layer 103 is embedded is undoped.

[0017] Furthermore, the first p electrode 108 and the first n electrode 109 are ohmic connected to the first p semiconductor region 104 and the first n semiconductor region 105 via the first p contact layer 106 and the first n contact layer 107. The first p contact layer 106 and the first n contact layer 107 are composed of a III-V compound semiconductor doped with a high concentration of the corresponding impurities. For example, the first p contact layer 106 and the first n contact layer 107 are composed of InGaAs. The semiconductor laser 151 configured in this way is a semiconductor laser in which the diffraction grating formed on the active layer 103 has a distributed Bragg reflection structure.

[0018] Laser oscillation is obtained by injecting current into the active layer 103 of the semiconductor laser 151, which constitutes this semiconductor laser, via the first p electrode 108 and the first n electrode 109. The laser light produced by this laser oscillation is output to the connecting optical waveguide 153, guided, and received by the photodetector 152. The connecting optical waveguide 153 consists of a connecting core 102a formed on the cladding layer 101. The connecting core 102a is formed by patterning the semiconductor layer 102 between the semiconductor laser 151 and the photodetector 152.

[0019] The light-receiving element 152 comprises an undoped i-semiconductor region 111 formed in the semiconductor layer 102 and extending in a predetermined direction, and a p-type second p-semiconductor region 112 and an n-type second n-semiconductor region 113 formed in the semiconductor layer 102 on either side of the i-semiconductor region 111. The second p-semiconductor region 112 is composed of a III-V compound semiconductor (InP) doped with p-type impurities, and the second n-semiconductor region 113 is composed of a III-V compound semiconductor (InP) doped with n-type impurities. These are formed by doping the semiconductor layer 102 with the corresponding impurities.

[0020] Furthermore, the second p electrode 116 and the second n electrode 117 are ohmic-connected to the second p semiconductor region 112 and the second n semiconductor region 113 via the second p contact layer 114 and the second n contact layer 115. The second p contact layer 114 and the second n contact layer 115 are composed of a III-V compound semiconductor doped with a high concentration of the corresponding impurities. For example, the second p contact layer 114 and the second n contact layer 115 are composed of InGaAs.

[0021] Furthermore, the photodetector 152 includes a light-absorbing layer 118 formed on the i-semiconductor region 111. The light-absorbing layer 118 is made of, for example, InGaAsP. In this example, the light-absorbing layer 118 is formed integrally with the second p-contact layer 114 and the second n-contact layer 115. For example, the second p-contact layer 114, the second n-contact layer 115, and the light-absorbing layer 118 can be formed by doping each of the regions flanking the light-absorbing layer 118 in the same InGaAsP layer with the corresponding impurities. As shown in the light intensity distribution (simulation) in the photodetector 152 in Figure 1D, it can be seen that light absorption occurs in the light-absorbing layer 118.

[0022] The light-receiving element 152 has a lateral pin junction formed by an i-semiconductor region 111, a second p-semiconductor region 112 sandwiching it, and an n-type second n-semiconductor region 113. By applying a reverse bias with the second p-electrode 116 and the second n-electrode 117, it operates as a photodiode.

[0023] As described above, the optical device according to Embodiment 1 is characterized in that the first p-contact layer 106, the first n-contact layer 107, the second p-contact layer 114, the second n-contact layer 115, and the light absorption layer 118 are all made of the same III-V compound semiconductor (for example, InGaAsP or InGaAs).

[0024] According to Embodiment 1, the semiconductor laser 151 and the photodetector 152 have the same layer structure, except for the active layer 103 and the diffraction grating. For example, the semiconductor laser 151 and the photodetector 152 share a common semiconductor layer 102 made of InP. Furthermore, the first p-contact layer 106, the first n-contact layer 107, the second p-contact layer 114, the second n-contact layer 115, and the light absorption layer 118 are formed from the same III-V compound semiconductor (InGaAsP or InGaAs) layer formed in contact with the semiconductor layer 102.

[0025] As a result, according to Embodiment 1, the semiconductor laser 151 and the photodetector 152 can be integrated at low cost and in a simple manner without using additional processes such as crystal regrowth.

[0026] For example, an active layer 103 and a semiconductor layer 102 are formed on a cladding layer 101 by embedded regrowth, and a diffraction grating is formed on the active layer 103. Then, a connecting core 102a is formed by known photolithography and etching techniques. Next, a first p semiconductor region 104 and a second p semiconductor region 112 are formed simultaneously by selective doping, and a first n semiconductor region 105 and a second n semiconductor region 113 are formed simultaneously by selective doping. At the same time, an undoped i semiconductor region 111 is formed.

[0027] Next, layers of III-V compound semiconductor (InGaAsP or InGaAs) to serve as contact layers are formed on the semiconductor layer 102 in which each region has been formed. Then, by selective doping, each p-type contact layer is formed simultaneously, and each n-type contact layer is also formed simultaneously. At the same time, a light absorption layer 118 is formed. After this, predetermined contact layers are separated by known photolithography and etching techniques.

[0028] As described above, except for the formation of the active layer and the diffraction grating, each layer constituting the semiconductor laser 151 and each layer constituting the photodetector 152 can be formed simultaneously.

[0029] [Embodiment 2] Next, an optical device according to Embodiment 2 of the present invention will be described with reference to Figures 2A and 2B. Similar to Embodiment 1 described above, the optical device according to Embodiment 2 comprises a semiconductor layer 102 made of a III-V compound semiconductor formed on a cladding layer 101, a semiconductor laser (not shown) formed on the semiconductor layer 102, and a photodetector 152a for monitoring the oscillating light of the semiconductor laser.

[0030] In Embodiment 2, all components except the light-receiving element 152a are the same as in Embodiment 1 described above, and therefore, the explanation is omitted.

[0031] The light-receiving element 152a according to Embodiment 2 comprises an i-semiconductor region 111 formed on the semiconductor layer 102, a second p-semiconductor region 112 and a second n-semiconductor region 113 formed on either side of the i-semiconductor region 111 of the semiconductor layer 102, a second p-contact layer 114, a second n-contact layer 115, and a second p-electrode 116 and a second n-electrode 117. These configurations are the same as those in Embodiment 1.

[0032] In Embodiment 2, a core layer 119 extending in the same direction as the i-semiconductor region 111 is formed on the i-semiconductor region 111 via a light-absorbing layer 118. The core layer 119 can be made of the same III-V compound semiconductor (InP) as the semiconductor layer 102.

[0033] In Embodiment 2, which includes a core layer 119, it functions as a rib-type waveguide, allowing for a propagation mode in which light is more strongly confined at the location where the core layer 119 is formed. As a result, compared to Embodiment 1, the amount of light confined to the light-absorbing layer 118 at the location where the core layer 119 is formed can be increased, as shown in the light intensity distribution at the photodetector 152a in Figure 2B.

[0034] [Embodiment 3] Next, an optical device according to Embodiment 3 of the present invention will be described with reference to Figures 3A and 3B. Similar to Embodiment 2 described above, the optical device according to Embodiment 3 comprises a semiconductor layer 102 made of a III-V compound semiconductor formed on a cladding layer 101, a semiconductor laser (not shown) formed on the semiconductor layer 102, and a photodetector 152b for monitoring the oscillating light of the semiconductor laser.

[0035] In Embodiment 3, everything except the light-receiving element 152b is the same as in Embodiment 2 described above, so the explanation will be omitted.

[0036] In Embodiment 3, as in Embodiment 2, a core layer 119 extending in the same direction as the i-semiconductor region 111 is formed on the i-semiconductor region 111 via a light-absorbing layer 118. Furthermore, in Embodiment 3, a light-absorbing layer 118a is formed separately from the second p-semiconductor region 112 and the second n-semiconductor region 113. The light-absorbing layer 118a is formed in the region directly beneath the core layer 119.

[0037] In Embodiment 3, which includes a core layer 119 and a separate light-absorbing layer 118a, it functions as a rib-type waveguide, allowing for a propagation mode in which light is more strongly confined at the location where the core layer 119 is formed. As a result, compared to Embodiment 1, the amount of light confinement to the light-absorbing layer 118a at the location where the core layer 119 is formed can be increased, as shown in the light intensity distribution in the photodetector element 152b in Figure 3B.

[0038] [Embodiment 4] Next, an optical device according to Embodiment 4 of the present invention will be described with reference to Figures 4A and 4B. Similar to Embodiment 2 described above, the optical device according to Embodiment 4 comprises a semiconductor layer 102 made of a III-V compound semiconductor formed on a cladding layer 101, a semiconductor laser (not shown) formed on the semiconductor layer 102, and a photodetector 152c for monitoring the oscillating light of the semiconductor laser.

[0039] In Embodiment 4, the components are the same as in Embodiment 2 described above, except for the light-receiving element 152c, so the explanation will be omitted.

[0040] In Embodiment 4, as in Embodiment 2, a core layer 119 extending in the same direction as the i-semiconductor region 111 is formed on the i-semiconductor region 111 via a light-absorbing layer 118b. Furthermore, in Embodiment 4, the light-absorbing layer 118b is formed integrally with the second p-contact layer 114 and is separated from the second n-semiconductor region 113. In Embodiment 4, the second n-semiconductor region 113 is formed only in the region directly beneath the second n-electrode 117.

[0041] In Embodiment 4, the second n semiconductor region 113 is separated from the light absorption layer 118b and formed away from the core layer 119 and the i semiconductor region 111. Therefore, since no holes are generated in the second n semiconductor region 113 due to light absorption, high-speed operation can be expected. In Embodiment 4 as well, as shown in the light intensity distribution in the photodetector 152c in Figure 4B, high light confinement is achieved in the light absorption layer 118a at the location where the core layer 119 is formed.

[0042] Incidentally, as shown in Figure 5A, the photodetector 152d can be configured such that a light absorption layer 118a is formed separately from the second p semiconductor region 112 and the second n semiconductor region 113, and no core layer is formed. In this configuration as well, the separated light absorption layer 118a functions as a rib-type waveguide, so a propagation mode can be achieved in which light is confined to the light absorption layer 118a (Figure 5B).

[0043] Furthermore, as shown in Figure 6A, the light-absorbing layer 118c can be formed integrally with the second n contact layer 115, resulting in a photodetector 152e that is separated from the second p semiconductor region 114. The second p semiconductor region 114 is formed only in the region directly beneath the second p electrode 116. Even with this configuration, a propagation mode can be achieved in which light is confined to the light-absorbing layer 118c sandwiched between the core layer 119 and the i semiconductor region 111 (Figure 6B).

[0044] As described above, according to the present invention, the first p-contact layer and first n-contact layer of the semiconductor laser, the second p-contact layer and second n-contact layer of the photodetector, and the light-absorbing layer are made from the same III-V compound semiconductor, so that the light-emitting element and the photodetector can be integrated without increasing costs.

[0045] It should be noted that the present invention is not limited to the embodiments described above, and it is clear that many modifications and combinations can be implemented within the technical concept of the present invention by those with ordinary skill in the art. [Explanation of symbols]

[0046] 101...Cladding layer, 102...Semiconductor layer, 102a...Connecting core, 103...Active layer, 104...First p-semiconductor region, 105...First n-semiconductor region, 106...First p-contact layer, 107...First n-contact layer, 108...First p-electrode, 109...First n-electrode, 111...i-semiconductor region, 112...Second p-semiconductor region, 113...Second n-semiconductor region, 114...Second p-contact layer, 115...Second n-contact layer, 116...Second p-electrode, 117...Second n-electrode, 118...Optical absorption layer, 151...Semiconductor laser, 152...Photodetector, 153...Connecting optical waveguide.

Claims

1. A semiconductor layer made of a III-V compound semiconductor formed on a cladding layer, The semiconductor layer comprises a waveguide-type semiconductor laser formed on the semiconductor layer and a waveguide-type photodetector for monitoring the light emitted by the semiconductor laser. The aforementioned semiconductor laser is A core-shaped active layer is formed embedded in the semiconductor layer and extends in a predetermined direction, A p-type first p semiconductor region and an n-type first n semiconductor region are formed in the portion of the semiconductor layer that sandwiches the active layer, A first p electrode formed on the first p semiconductor region, A first n electrode formed on the first n semiconductor region, A first p contact layer formed between the first p semiconductor region and the first p electrode, A first n contact layer formed between the first n semiconductor region and the first n electrode, Equipped with, The light-receiving element comprises an undoped i-semiconductor region formed in the semiconductor layer and extending in a predetermined direction, A p-type second p-semiconductor region and an n-type second n-semiconductor region are formed in the portions of the aforementioned semiconductor layer that sandwich the i-semiconductor region, A second p electrode formed on the aforementioned second p semiconductor region, A second n electrode formed on the second n semiconductor region, A second p contact layer formed between the second p semiconductor region and the second p electrode, A second n contact layer formed between the second n semiconductor region and the second n electrode, A light-absorbing layer formed in contact with the i-semiconductor region and Equipped with, The first p-contact layer, the first n-contact layer, the second p-contact layer, the second n-contact layer, and the light-absorbing layer are composed of the same III-V compound semiconductor. The i-semiconductor region comprises a core layer formed on the i-semiconductor region via the light-absorbing layer, and extending in the same direction as the i-semiconductor region. The optical device is characterized in that the core layer is composed of the same III-V compound semiconductor as the semiconductor layer.

2. In the optical device according to claim 1, The optical device is characterized in that the light-absorbing layer is formed integrally with the second p contact layer and the second n contact layer.

3. In the optical device according to claim 1, The optical device is characterized in that the light-absorbing layer is formed integrally with the second p-contact layer.

4. In the optical device according to any one of claims 1 to 3, The semiconductor layer is composed of InP, The first p contact layer, the first n contact layer, the second p contact layer, the second n contact layer, and the light absorption layer are composed of InGaAsP or InGaAs. An optical device characterized by the following features.

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