JP2012248587A - Semiconductor light-receiving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly reliable and compact semiconductor light-receiving device exhibiting a stable light monitor function easily at a low cost.SOLUTION: The semiconductor light-receiving device comprises a photodiode region 10 connected to a ridge type slab waveguide region 30 guiding light, and provided on the same substrate as the ridge type slab waveguide region 30 in order to absorb the incident light. The photodiode region 10 has a layer structure formed of the same semiconductor composition as the ridge type slab waveguide region 30, and includes an upper electrode 16 provided above an upper clad layer of the photodiode region 10. The core layer of the photodiode region 10 forms an orbital absorption layer 11 which absorbs the incident light while guiding and orbiting, and the end 16a of the upper electrode 16 is located on the inside of the end 11a of the absorption layer 11.

Description

  The present invention relates to a semiconductor light-receiving device, and more particularly to a semiconductor light-receiving device that forms a photodiode for detecting the waveguide light intensity of an optical waveguide semiconductor device.

  Optical waveguide semiconductor devices are integrated devices that have built-in optical signal processing functions from single-function devices represented by conventional semiconductor laser diodes, due to recent progress in crystal growth technology and high-precision processing technology. Development is progressing.

  In order to integrate semiconductor functional elements, it is necessary to couple each functional element with an optical waveguide, and it is important to reduce propagation loss and coupling loss between functional elements as much as possible.

  The semiconductor optical waveguide basically has a multilayer structure composed of a light confinement structure using a difference in refractive index, generally called a slab waveguide structure. This is mainly formed by a core layer with a high refractive index through which light propagates and a cladding layer with a low refractive index formed around it, and the light propagating by this refractive index difference is centered on the core layer in the center. To make it progress. Here, a ridge slab waveguide as an example of a slab waveguide structure will be described with reference to FIGS. As shown in these drawings, the ridge-type slab waveguide 100 includes a core layer 101, and a lower cladding layer 102 and an upper cladding layer 103 formed on the lower and upper portions of the core layer 101, respectively. Has a ridge structure with a predetermined width. That is, a ridge portion 104 having a predetermined width is formed in the upper cladding layer 103. Due to the difference in refractive index of these layers 101, 102, and 103 and the ridge portion 104, the light 130 incident from one end face 100 a of the ridge slab waveguide 100 propagates in the region 105 immediately below the ridge portion 104 in the core layer 101. The light is emitted from the other end face 100 b of the ridge type slab waveguide 100.

  Here, the semiconductor composition of the core layer and the cladding layer in the ridge slab waveguide described above is determined to be a material in which the band gap energy wavelength of the semiconductor is shorter than the wavelength of the propagating light. This is because as the wavelength of light approaches the band gap energy wavelength of the semiconductor, light absorption by the semiconductor occurs and propagation loss increases. In the waveguide part where light propagation loss is reduced and the light is propagated, the semiconductor core layer and the guide layer (the layer in which the core layer is sandwiched between the upper and lower layers) has a band gap energy wavelength longer than the wavelength of the light. It is necessary to form with the composition which has.

  On the other hand, a photodiode is generally used as a device for measuring the intensity of light. Since a photodiode absorbs light and converts it into an electrical signal, a semiconductor with a band gap energy wavelength longer than the wavelength of light is used as the semiconductor composition of the absorption region, unlike the semiconductor composition that forms an optical waveguide. .

  In order to measure the light intensity propagating in the optical waveguide, in general, in order to increase the light absorption efficiency of the photodiode portion, the photodiode region is formed on the same substrate with a semiconductor material having a composition different from that of the waveguide. In addition, an element manufacturing process such as crystal growth is required separately from the waveguide portion (see, for example, Non-Patent Document 1 below). Here, a conventional waveguide photodiode in which a photodiode portion is formed on the same substrate as the ridge slab waveguide having the above-described configuration will be described with reference to FIGS. 4 (a), 4 (b), and 4 (c). As shown in these figures, the waveguide photodiode is provided in contact with the ridge slab waveguide 100 on the same substrate as the lower cladding layer 102 (substrate) of the ridge slab waveguide 100 forming the waveguide portion. The photodiode portion 110 is provided. The photodiode portion 110 includes an absorption layer 111 provided on the lower cladding layer 102, an upper cladding layer 113 provided on the absorption layer 111, and an electrode 116 (upper electrode) provided on the upper cladding layer 113. Is provided. The absorption layer 111 has the same thickness as the core layer 101 of the ridge slab waveguide 100 and is formed with a composition different from that of the core layer 101. In the absorption layer 111 of the photodiode portion 110, the light incident on the photodiode portion 110 is absorbed by the region 115 facing the region 105 where the light of the waveguide portion 100 propagates.

  As described above, in order to form semiconductor regions having different compositions on the same substrate, it is necessary to perform a semiconductor epitaxial growth step a plurality of times and to repeat a crystal growth step and a step of processing into a desired shape. Therefore, it is necessary to note that the manufacturing process becomes complicated, and the previously formed semiconductor layer undergoes a thermal process that is heated to the temperature of crystal growth again, resulting in deterioration and modification of characteristics.

  On the other hand, light absorption can be increased by applying an electric field to the semiconductor layer. This is called the Franz-Keldish effect, and the band of the conduction band 151 and the valence band 152 is inclined by the electric field applied to the semiconductor as shown in FIG. Can also cause absorption. When no electric field is applied, as shown in FIG. 5A, the bands of the conduction band 141 and the valence band 142 are not inclined and no absorption occurs for light smaller than the band gap energy. Become.

  In order to obtain a sufficient increase in absorption coefficient by applying an electric field, it is necessary to form the band gap energy wavelength of the semiconductor core layer without applying an electric field from a semiconductor having a composition sufficiently close to the wavelength of light. In this case, the fluctuation of the absorption coefficient also occurs even when no electric field is applied due to temperature fluctuations, etc., so that the propagation loss increases in the waveguide portion that guides light, resulting in deterioration of characteristics. End up. Therefore, it is necessary for the optical waveguide to reduce the propagation loss due to absorption by separating the band gap energy wavelength and the light wavelength to some extent, and a photodiode having an absorption layer with such a semiconductor composition has sufficient light. In order to cause absorption, it is necessary to apply a large electric field or to have a sufficient element length.

  However, when the electric field applied in the reverse direction of the semiconductor is increased, it is necessary to consider reliability problems such as formation of a local leakage current path and deterioration of the semiconductor layer due to a strong electric field. In particular, the application of a strong electric field at the side wall tends to cause breakdown and failure, so a structure that reduces the electric field strength near the surface is required. For example, in an avalanche photodiode that operates in a state where a strong electric field is applied, an inclined mesa structure or a guard ring structure is used. For example, as illustrated in FIG. 6, the semiconductor device 120 having the inclined mesa structure includes an absorption layer 121, a lower cladding layer 122, an upper cladding layer 123, and an upper electrode 126, and the width of the absorption layer 121 is directed from the upper side to the lower side. Are gradually formed. That is, the side wall portions 121a and 121b of the absorption layer 121 are formed in an inclined shape. However, in the waveguide type photodiode, since the width of the surface electrode is determined by the waveguide width, it is difficult to form a sufficient area, and it is difficult to incorporate such a shape for electric field relaxation.

  Further, in order to increase the light receiving sensitivity as a photodiode, it is necessary to lengthen the absorption region. However, in the integrated device, the area occupied by the element increases, resulting in a demerit in element design.

  From the above viewpoint, the light intensity detection by the conventional waveguide type device can be performed by using the semiconductor composition of the absorption layer in the absorption region forming the photodiode portion and the semiconductor composition of the core layer in the waveguide region forming the waveguide portion. It was necessary to compose with something different.

H. Nakamura, M. Shishikura, S. Tanaka, Y. Matsuoka, T. Ono, T. Miyazaki, S. Tsuji, "High Responsivity, Low Dark Current, and Highly Reliable Operation of InGaAlAs Waveguide Photodiodes for Optical Hybrid Integration", IEICE Trans. Electron., Vol. E80-C, No. 1,, p.41-46, January 1997

  If a slab waveguide structure with a small propagation loss can be used as an optical waveguide as it is as a photodiode, it is not necessary to form a semiconductor layer structure having a different composition, and the cost required for this can be reduced.

  However, with the slab waveguide structure, it is necessary to increase the applied electric field because the light absorption coefficient is small even if a photodiode is formed. In this case, in view of reliability such as failure due to a high electric field in the sidewall portion of the waveguide Is concerned about the problem. In addition, in order to obtain a sufficient current due to light absorption, it is necessary to lengthen the waveguide photodiode portion that becomes the absorption region, which causes restrictions on the degree of freedom of the arrangement of the photodiode in the integrated device, In addition, it becomes a problem in miniaturization of the device.

  In view of the above, the present invention has been made to solve the above-described problems, has low cost and high reliability, easily expresses a stable light monitoring function, and is small in size. An object of the present invention is to provide a semiconductor light receiving device.

A semiconductor light-receiving device according to the present invention that solves the above-described problems is connected to a ridge-type slab waveguide region where light is guided, and is provided on the same substrate as the ridge-type slab waveguide region. A semiconductor light receiving device including a photodiode region to absorb, wherein the photodiode region has a layer structure formed of the same semiconductor composition as that of the ridge-type semiconductor slab waveguide, and an upper portion of an upper cladding layer of the photodiode region. An upper electrode provided on the photodiode region, wherein the core layer of the photodiode region forms a circular absorption layer in which the incident light is absorbed while being guided around, and an end portion of the upper electrode is the absorption It is characterized by being arranged inside the end of the layer.
The ridge slab waveguide region includes a core layer, a lower clad layer, and an upper clad layer. The upper clad layer has a ridge structure, and a region immediately below the ridge portion of the upper clad layer in the core layer emits light. A wave guiding region is formed.

  A semiconductor light-receiving device according to the present invention that solves the above-described problems is the semiconductor light-receiving device according to the above-described invention, wherein the absorption layer is formed in a circular shape or a polygonal shape.

  A semiconductor light-receiving device according to the present invention that solves the above-described problems is the semiconductor light-receiving device according to the above-described invention, wherein the absorption layer is wider than a portion of the ridge-type slab waveguide region where the light is guided. It is characterized by being.

  A semiconductor light-receiving device according to the present invention that solves the above-described problems is the semiconductor light-receiving device according to the above-described invention, wherein the absorption layer and the semiconductor slab waveguide region are connected in a tangential direction of the absorption layer. It is characterized by.

  According to the semiconductor light receiving device of the present invention, the layer structure of the ridge slab waveguide region and the photodiode region is formed by forming a layer structure in which the photodiode region is formed with the same semiconductor composition as the ridge slab waveguide region. The same crystal growth process can be used. Thereby, the manufacturing process is simplified, and high reliability can be realized at low cost. The core layer in the photodiode region forms a circular absorption layer in which incident light is guided around the inside and absorbed while rotating, so that the absorption layer can be downsized, that is, the semiconductor light receiving device can be downsized. . By arranging the end of the upper electrode on the inner side of the end of the absorption layer, it is possible to easily and stably monitor the light without forming a local leakage current path or causing deterioration of the semiconductor layer due to a strong electric field. Function can be expressed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory view of a semiconductor light receiving device according to a first embodiment of the present invention, FIG. 1 (a) shows a plan view thereof, FIG. 1 (b) shows a side view thereof, and FIG. The cc cross section in (a) is shown. FIGS. 2A and 2B are explanatory views of a semiconductor light receiving device according to a second embodiment of the present invention, FIG. 2A showing the plane thereof, FIG. 2B showing the side surface thereof, and FIG. The cc cross section in (a) is shown. It is explanatory drawing of the conventional ridge type slab waveguide, Comprising: The cross section is shown to Fig.3 (a), and the side is shown to FIG.3 (b). It is explanatory drawing of the conventional waveguide type photodiode, Comprising: The side surface is shown to Fig.4 (a), the bb cross section of Fig.4 (a) is shown, and Fig.4 (c) is shown. The cc cross section of Fig.4 (a) is shown. It is a figure for demonstrating the light absorption of a semiconductor layer, Comprising: The case where an electric field is not applied is shown to Fig.5 (a), and the case at the time of an electric field application is shown in FIG.5 (b). It is sectional drawing of the semiconductor device of the conventional inclination mesa structure.

  Hereinafter, one embodiment for implementing a semiconductor light receiving device according to the present invention will be described.

  The photodiode constituting the semiconductor light receiving device according to the present embodiment has a layer structure formed of the same semiconductor composition as the semiconductor slab waveguide through which light is guided. In other words, the core layer of the semiconductor slab waveguide (optical waveguide) is used as it is as the absorption layer (core layer) of the photodiode. As a result, the regrowth process and selective growth process for forming the light absorption layer of the photodiode with a semiconductor of another composition can be omitted, thereby reducing the manufacturing cost and the influence of the thermal history during the regrowth process. Can be eliminated.

  When a semiconductor layer having such a composition of the core layer of the semiconductor slab waveguide is used as the absorption layer (core layer) of the photodiode, the absorption coefficient is small, so that a sufficient length (size) is required. If this is a straight waveguide structure, the area occupied by the photodiode portion will be larger than that of the conventional photodiode portion. Therefore, in the slab waveguide structure, a polygon or a polygon whose interior angle is the total reflection angle is used. Shape. The light incident on the photodiode part circulates around the inner circumference of the circular waveguide or circulates around the circular waveguide forming the photodiode while being reflected by the side wall (side wall surface) having a total reflection angle. Keep doing. This makes it possible to obtain a sufficient length effectively, and incident light can be absorbed by the absorption layer and converted into electricity. In this way, the incident light can be absorbed by the absorption layer of the photodiode portion of the circular waveguide type, so that it is linear with respect to the light propagation direction and has the same semiconductor composition as the core layer of the waveguide. Compared with the case where the absorption layer of the diode portion is formed, the size can be reduced to about 1/10.

  Further, it is necessary to increase the applied electric field to this region. The conventional waveguide type photodiode has an elongated shape along the propagation direction in order to maintain the waveguide structure. When a strong electric field is applied to the photodiode, the electric field concentrates on the side wall portion of the waveguide. Reliability problems such as increased leakage current on the surface and electrical failure have occurred. Here, when the absorption layer has a circular waveguide structure, a sufficient area for electrode formation can be secured in the central portion of the waveguide. Therefore, it is not necessary to form an electrode up to the vicinity of the end face of the waveguide, and by forming the electrode in the central portion sufficiently away from the end face, it is possible to alleviate electric field concentration near the end face.

  In this way, it is possible to apply a relatively large electric field to the photodiode portion of the slab waveguide structure while maintaining high reliability.

  A semiconductor light receiving device according to a first embodiment of the present invention will be described with reference to FIGS. 1 (a), 1 (b) and 1 (c). In FIG. 1A, the ridge portion in the semiconductor slab waveguide region is omitted.

  As shown in FIGS. 1A, 1B, and 1C, the semiconductor device constituting the semiconductor light receiving device according to the present embodiment is connected to a ridge slab waveguide region 30 through which light is guided, and The photodiode region 10 is provided on the lower cladding layer 32 that is the same substrate as the ridge-type slab waveguide region 30 and absorbs incident light.

  The ridge-type slab waveguide region 30 includes a core layer 31, and a lower clad layer 32 and an upper clad layer 33 provided on the lower and upper portions of the core layer 31, respectively, and the upper clad layer 33 has a predetermined width. Has a mold structure. That is, a ridge portion 34 having a predetermined width is formed in the upper cladding layer 33. In the ridge slab waveguide region 30 having such a configuration, light is guided through a region immediately below the ridge portion 34 in the core layer 31.

  The photodiode region 10 has a layer structure formed of the same semiconductor composition as that of the ridge type slab waveguide region 30. The photodiode region 10 includes an absorption layer (core layer) 11 provided on the lower cladding layer 32 and an upper cladding layer 13 provided on the absorption layer 11, and the upper cladding layer 13 has a predetermined width. Has a mold structure. A ridge portion 14 having a predetermined width is formed in the upper cladding layer 13. An upper electrode (metal electrode) 16 for extracting a light absorption current is formed on the ridge portion 14. That is, the upper cladding layer 13 and the upper cladding layer 33, and the absorption layer 11 and the core layer 31 are formed with the same semiconductor composition. In the absorption layer 11, the incident light is absorbed while being guided. Further, among the electrodes for applying the electric field, for example, an n-type doped conductive semiconductor layer is formed on the entire surface below the layer structure, and is located at a position different from the absorption layer 11, that is, in the photodiode region 10. A lower electrode (metal pad) 17 is formed at a position away from directly below the upper electrode 16 below the lower cladding layer 32.

  The absorption layer 11 and the upper cladding layer 13 are formed in a cylindrical shape, and the peripheral wall portion 11a of the absorption layer 11 and the peripheral wall portion 13a of the upper cladding layer 13 are circular in plan. The upper electrode 16 is formed in the same circular shape as the ridge portion 14. That is, the upper electrode 16 is disposed at the center of the absorption layer 11, and the peripheral wall portion (end portion) 16 a of the upper electrode 16 is disposed at a position shifted inward from the side wall portion 11 a of the absorption layer 11. As a result, the electric field strength in the vicinity of the peripheral wall portion 11a of the absorption layer 11 can be reduced, and breakage due to leak path formation or electric field concentration when an electric field is applied can be prevented.

  In the semiconductor light receiving device configured as described above, the light 51 guided through the ridge slab waveguide region 30 is a photodiode region having the same layer structure as the ridge slab waveguide region 30 from the ridge slab waveguide region 30. 10 is incident. Here, the light 52 incident on the photodiode region 10 circulates in the circular shape of the absorption layer 11 while propagating along the inner periphery of the absorption layer 11 forming the circularly processed waveguide portion. In the side wall portion 11a of the absorption layer 11 forming the waveguide portion, the propagating light 52 circulates without being emitted outside the absorption layer 11 due to the difference in refractive index between the semiconductor and air. That is, the absorption layer 11 has a circular shape.

  As described above, by forming the upper electrode 16 on the ridge portion 14, an electric field can be applied to the upper and lower sides of the circumferential absorption layer 11. That is, an electric field can be applied to the absorption layer 11 (core layer) by applying a bias voltage to the upper electrode 16 and the lower electrode 17. The electric field applied up and down increases the absorption coefficient of the semiconductor, and light is absorbed by the semiconductor to generate electron-hole pairs. The generated carriers are carried to the electrode by the electric field and taken out as current.

  Therefore, the light 52 that circulates around the absorption layer 11 is gradually absorbed and converted into an electric signal, and thus is not directly transmitted to the outside as light.

  As described above, according to the semiconductor light receiving device according to the present embodiment, the absorption layer 11 in the photodiode region 10 has the same layer structure as the ridge-type slab waveguide region by forming a circular shape in which light circulates. Therefore, the size can be reduced to 1/10 or less as compared with a photodiode in which an absorption layer is provided in a straight line. That is, the size of the semiconductor light receiving device can be reduced. Furthermore, since the photodiode region 10 can be formed in a small size, it is possible to contribute to an improvement in design flexibility of the integrated device.

  Further, by forming a layer structure in which the photodiode region 10 is formed with the same semiconductor composition as the ridge slab waveguide region 30, the layer structure of the ridge slab waveguide region 30 and the photodiode region 10 can be formed in the same crystal growth process. Can be produced.

  Therefore, by using the semiconductor light receiving device according to the present embodiment, it is possible to use the regrowth process and the selective growth process associated with the formation of the light absorption layer for the photodiode region as compared with the conventional semiconductor waveguide photodiode. Since it is not necessary and it is not necessary to consider the influence of the thermal history due to these, it is possible to easily incorporate a stable and stable optical monitor function into a semiconductor waveguide device at a low cost.

  Since the absorption layer 11 is wider than the portion of the ridge slab waveguide region 30 where light is guided, the light intensity is increased when light enters the photodiode region 10 from the ridge slab waveguide region 30. A high portion (the central portion of light) propagates in the circulation direction in the absorption layer 11, and a portion where the light intensity is low (outside portion of the light) spreads in the absorption layer 11, but the periphery in the absorption layer 11 Propagate in the direction. Thereby, the possibility that the light 52 that has entered the photodiode region 10 is emitted to the ridge-type slab waveguide region 30 is reduced.

  When the absorption layer 11 and the ridge slab waveguide region 30 are connected in a tangential direction in the plane of the absorption layer 11, the light 52 incident on the photodiode region 10 circulates in the photodiode region 10. Thereby, the possibility that the light 52 that has entered the photodiode region 10 is emitted to the ridge-type slab waveguide region 30 is reduced.

A semiconductor light receiving device according to a second embodiment of the present invention will be described with reference to FIGS. 2 (a), 2 (b) and 2 (c). In FIG. 2A, the ridge portion in the semiconductor slab waveguide region is omitted.
The semiconductor light-receiving device according to this example is obtained by changing the form of the photodiode region included in the semiconductor light-receiving device according to the above-described first example, and other than that, the semiconductor according to the above-described first example The configuration is the same as that of the light receiving device, and the operational effects are also the same. Therefore, only the parts different from the semiconductor light receiving device according to the first embodiment will be described here. In the present embodiment, the same components as those in the semiconductor light receiving device according to the first embodiment are denoted by the same reference numerals.

  As shown in FIGS. 2A, 2B, and 2C, the semiconductor device constituting the semiconductor light receiving device according to this embodiment is connected to a ridge slab waveguide region 30 through which light is guided, and A photodiode region 20 is provided on the lower clad layer 32, which is the same substrate as the ridge-type slab waveguide region 30, and absorbs incident light.

  The photodiode region 20 has a layer structure formed of the same semiconductor composition as that of the ridge type slab waveguide region 30. The photodiode region 20 includes an absorption layer (core layer) 21 provided on the lower cladding layer 32 and an upper cladding layer 23 provided on the absorption layer 21, and the upper cladding layer 23 has a predetermined width. Has a mold structure. A ridge portion 24 having a predetermined width is formed in the upper cladding layer 23. An upper electrode (metal electrode) 26 for taking out the light absorption current is formed on the ridge portion 24. That is, the upper clad layer 23 and the upper clad layer 33, and the absorption layer 21 and the core layer 31 are formed with the same semiconductor composition. In the absorption layer 21, the incident light is absorbed while being guided. Further, among the electrodes for applying an electric field, for example, an n-type doped conductive semiconductor layer is formed on the entire surface below the layer structure, and is located at a position different from the absorption layer 21, that is, in the photodiode region 20. A lower electrode (metal pad) 27 is formed at a position away from directly below the upper electrode 26 under the lower clad 32.

  The absorbing layer 21 and the upper cladding layer 23 are formed in a regular octagonal columnar shape, and the peripheral wall portion 21a of the absorbing layer 21 and the peripheral wall portion 23a of the upper cladding layer 23 form a regular octagonal shape in a plane. The upper electrode 26 is formed in the same regular octagon shape as the ridge portion 24. That is, the upper electrode 26 is disposed at the center of the absorption layer 21, and the peripheral wall portion (end portion) 26 a of the upper electrode 26 is disposed at a position shifted inward from the side wall portion 21 a of the absorption layer 21. As a result, the electric field strength in the vicinity of the peripheral wall portion 21a of the absorption layer 21 can be reduced, and breakdown due to leakage path formation or electric field concentration when an electric field is applied can be prevented.

  In the semiconductor light receiving device having the above-described configuration, the light 61 guided through the ridge slab waveguide region 30 passes from the ridge slab waveguide region 30 to the photodiode region 20 having the same layer structure as the ridge slab waveguide region 30. Will be incident. Here, the light 62 incident on the photodiode region 20 propagates while totally reflecting the inner circumference of the absorption layer 21 forming the regular octagonal waveguide portion, and goes around the regular octagonal shape of the absorption layer 21. become. In the side wall portion 21a of the absorption layer 21 forming the waveguide portion, the propagating light 62 circulates without being emitted outside the absorption layer 21 due to the difference in refractive index between the semiconductor and air. That is, the absorption layer 21 has a circular shape.

  As described above, by forming the upper electrode 26 on the ridge portion 24, an electric field can be applied to the upper and lower sides of the circumferential absorption layer 21. That is, by applying a bias voltage to the upper electrode 26 and the lower electrode 27, an electric field can be applied to the absorption layer 21 (core layer). The electric field applied up and down increases the absorption coefficient of the semiconductor, and light is absorbed by the semiconductor to generate electron-hole pairs. The generated carriers are carried to the electrode by the electric field and taken out as current.

  Therefore, since the light 62 circulating around the absorption layer 21 is gradually absorbed and converted into an electric signal, it is not transmitted to the outside as it is.

  As described above, according to the semiconductor light receiving device according to the present embodiment, the absorption layer 21 in the photodiode region 20 has a circular shape in which light circulates, and thus is the same as in the case of the first embodiment described above. Compared with a photodiode having the same layer structure as that of the ridge-type slab waveguide region and having an absorption layer provided in a straight line, the size can be reduced to one tenth or less. That is, the size of the semiconductor light receiving device can be reduced. Further, since the photodiode region 20 can be formed in a small size, it can contribute to an improvement in the degree of freedom in designing an integrated device.

  Further, by forming a layer structure in which the photodiode region 20 is formed with the same semiconductor composition as the ridge slab waveguide region 30, the layer structure of the ridge slab waveguide region 30 and the photodiode region 20 can be formed in the same crystal growth process. Can be produced.

  Therefore, by using the semiconductor light receiving device according to the present embodiment, it is possible to use the regrowth process and the selective growth process associated with the formation of the light absorption layer for the photodiode region as compared with the conventional semiconductor waveguide photodiode. Since it is not necessary and it is not necessary to consider the influence of the thermal history due to these, it is possible to easily incorporate a stable and stable optical monitor function into a semiconductor waveguide device at a low cost.

  Since the absorption layer 21 is wider than the portion of the ridge-type slab waveguide region 30 where light is guided, the light intensity is increased when light enters the photodiode region 20 from the ridge-type slab waveguide region 30. A high part (the center part of light) propagates in the circulation direction in the absorption layer 21, and a part with a low light intensity (outer part of the light) spreads in the absorption layer 21, but is surrounded in the absorption layer 21. Propagate in the direction. Thereby, the possibility that the light 62 that has entered the photodiode region 20 is emitted to the ridge-type slab waveguide region 30 is reduced.

  The absorption layer 21 and the ridge-type slab waveguide region 30 are connected in a tangential direction in the plane of the absorption layer 21, so that the extending direction of the semiconductor slab waveguide region 30 and the side wall portion 21 a of the absorption layer 21 that forms the front face thereof are formed. When the light 62 that has an obtuse angle and is incident on the photodiode region 20 is reflected by the side wall portion 21a of the absorption layer 21, the light 62 circulates in the absorption layer 21 without propagating to the slab waveguide region 30. Thereby, the possibility that the light 62 that has entered the photodiode region 20 is emitted to the ridge-type slab waveguide region 30 is reduced.

  In the above description, the semiconductor light-receiving device including the absorption layer 11 having a circular shape in the plane and the semiconductor light-receiving device including the absorption layer 21 having a regular octagonal shape in the plane have been described, but light incident on the absorption layer circulates. For example, a semiconductor light-receiving device including an absorption layer having an elliptical shape on a plane, or a semiconductor light-receiving device including an absorption layer having a polygonal shape other than a regular octagonal shape on a plane can be used. In addition, when the absorption layer is a quadrangular shape, the absorption layer is wider in a plane than the portion where the light propagates in the ridge type slab waveguide region so that the light incident in the absorption layer spreads to the surroundings, The photodiode region may be arranged so that an acute angle or an obtuse angle is formed between the extending direction of the ridge-type slab waveguide region and the side wall portion of the absorption layer facing the extending direction of the ridge-type semiconductor slab waveguide.

  In the above, the semiconductor light receiving device including the absorption layer 11 of the photodiode region 10 formed wider than the portion of the ridge slab waveguide region 30 where the light 51 propagates, and the light 61 in the ridge slab waveguide region 30 propagates. The semiconductor light receiving device having the photodiode region 20 formed wider than the portion to be described has been described. However, the absorption layer of the photodiode region formed narrower than the portion in which the light propagates in the ridge slab waveguide region is provided. It is also possible to provide a semiconductor light receiving device. That is, the absorption layer in the photodiode region may have any shape that allows the incident light to circulate inside.

  In the above, the semiconductor light receiving device in which the ridge slab waveguide region 30 and the photodiode region 10 are connected in the tangential direction in the plane of the absorption layer 11, and the ridge slab waveguide region 30 and the photodiode region 20 are the absorption layer 21. The semiconductor light-receiving device connected in the tangential direction in the plane of the semiconductor device has been described. However, the ridge-type slab waveguide region and the photodiode region are not limited to the tangential direction in the plane of the absorption layer and are connected in other places. It is also possible to do.

  The present invention relates to a semiconductor light receiving device, which is low-cost, highly reliable, easily expresses a stable optical monitoring function, and can be downsized, which is extremely useful in the optical communication industry and the like. Can be used.

DESCRIPTION OF SYMBOLS 10 Photodiode area | region 11 Absorption layer 13 Upper clad layer 14 Ridge part 16 Upper electrode 17 Lower electrode 20 Photodiode area 21 Absorption layer 23 Upper clad layer 24 Ridge part 26 Upper electrode 27 Lower electrode 30 Ridge-type slab waveguide area 31 Core layer 32 Lower clad layer 33 Upper clad layer 34 Ridge portion 51 Light guided through waveguide region 52 Light propagated through photodiode region 61 Light guided through waveguide region 62 Light propagated through photodiode region

Claims (4)

A semiconductor light receiving device that includes a photodiode region that is connected to a ridge slab waveguide region where light is guided and is provided on the same substrate as the ridge slab waveguide region and absorbs incident light,
The photodiode region has a layer structure formed of the same semiconductor composition as the ridge-type slab waveguide region, and includes an upper electrode provided on the upper cladding layer of the photodiode region,
The core layer of the photodiode region forms a circular absorption layer in which the incident light is absorbed while being guided around the inside,
The semiconductor light-receiving device, wherein an end portion of the upper electrode is disposed inside an end portion of the absorption layer. The semiconductor light-receiving device according to claim 1,
The semiconductor light-receiving device, wherein the absorption layer is formed in a circular shape or a polygonal shape. The semiconductor light-receiving device according to claim 1 or 2,
The semiconductor light-receiving device, wherein the absorption layer is wider than a portion where the light is guided in the ridge-type slab waveguide region. The semiconductor light-receiving device according to claim 3,
The semiconductor light receiving device, wherein the absorption layer and the ridge slab waveguide region are connected in a tangential direction of the absorption layer.

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