JP2019054029A - Optical receiver, balance-type optical receiver, manufacturing method of optical receiver - Google Patents

Abstract

To provide an optical receiver capable of preventing degradation in high speed characteristics in the case when, for example, when a large light intensity is input to the optical receiver.SOLUTION: An optical receiver 4 comprises: an input waveguide core layer 1; a guide waveguide core layer 2 communicating with the input waveguide core layer; and a light absorption layer 3 which is formed above the guide waveguide core layer at one side in a width direction with respect to the center position in the width direction of the input waveguide core layer.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a light receiver, a balanced light receiver, and a method for manufacturing the light receiver.

  As a waveguide type semiconductor light receiver, there is a light receiver including an optical waveguide and a light absorption layer.

Japanese Patent Laid-Open No. 4-2121209 JP 2000-292637 A JP 2012-199373 A Japanese Patent Laid-Open No. 5-160430

In a general light receiver, there is a peak of the light intensity distribution of input light at the center position in the width direction of the waveguide core layer constituting the optical waveguide, and the light intensity locally increases at this position. A light absorption layer is also provided at a position where the light intensity is locally increased.
For this reason, for example, when the input light intensity to the light receiver is large, a large number of photocarriers are generated in the absorption layer, and accumulated in the absorption layer, a shielding electric field is generated. As a result, the high-speed characteristics are deteriorated.

  An object of the present invention is to suppress the deterioration of high-speed characteristics even when the intensity of input light to a light receiver is large.

In one aspect, the light receiver includes an input waveguide core layer, a guide waveguide core layer connected to the input waveguide core layer, and one side in the width direction with respect to the center position in the width direction of the input waveguide core layer. And a light absorption layer provided above the guide waveguide core layer.
In one aspect, the balanced light receiver includes a first light receiver and a second light receiver, and the first light receiver is connected to the first input waveguide core layer and the first input waveguide core layer. The first light absorption provided on one side in the width direction with respect to the center position in the width direction of the one guide waveguide core layer and the first input waveguide core layer and above the first guide waveguide core layer A first electrode connected to one side in the thickness direction of the first light absorption layer, and a second electrode connected to the other side in the thickness direction of the first light absorption layer, The two light receivers are arranged in the width direction with respect to the center position in the width direction of the second input waveguide core layer, the second guide waveguide core layer connected to the second input waveguide core layer, and the second input waveguide core layer. One side, which is connected to the second light absorption layer provided above the second guide waveguide core layer and one side in the thickness direction of the second light absorption layer. A third electrode; a fourth electrode connected to the other side of the second light absorption layer in the thickness direction; and a signal line connected to the first electrode and the third electrode; A first ground line connected to the second ground line; and a second ground line connected to the fourth electrode.

  In one aspect, a method for manufacturing an optical receiver includes: a step of providing an input waveguide core layer and a guide waveguide core layer connected to the input waveguide core layer; and a center position in the width direction of the input waveguide core layer. And a step of providing a light absorption layer on one side in the width direction and above the guide waveguide core layer.

  As one aspect, even when the input light intensity to the light receiver is large, there is an effect that deterioration of high-speed characteristics can be suppressed.

(A), (B) is a schematic diagram which shows the structure of the light receiver concerning this embodiment, (A) is sectional drawing which follows the AA 'line of (B), (B) is a plane. FIG. (A)-(C) are the figures for demonstrating the setting of the angle of the diagonal side surface of the guide waveguide core layer with which the light receiver concerning this embodiment is equipped. (A) is a figure which shows the simulation result of the light intensity of the light receiver shown to FIG. 11 (A) and FIG.11 (B), (B) is the light intensity simulation result of the light receiver of this embodiment. FIG. It is a typical top view which shows the structure of the modification of the light receiver concerning this embodiment. (A)-(C) are the figures for demonstrating the effect by the structure of the modification of the light receiver concerning this embodiment. It is a typical top view which shows the structure of the other modification of the light receiver concerning this embodiment. (A), (B) is a schematic diagram which shows the structure of the other modification of the optical receiver concerning this embodiment, Comprising: (A) is sectional drawing which follows the AA 'line of (B). , (B) are plan views. (A)-(J) are typical sectional drawings for demonstrating the manufacturing method of the optical receiver concerning this embodiment. (A) is a schematic plan view showing a configuration of a balanced light receiver according to the present embodiment, and (B) is a diagram showing a circuit configuration. It is a typical top view which shows the structure of the transmitter / receiver to which the light receiver (balance type light receiver) concerning this embodiment is applied. (A) is a schematic plan view which shows the structure of a comparative example, (B) is typical sectional drawing which follows the AA 'line in (A). (A) is a schematic top view which shows the structure of another comparative example, (B) is typical sectional drawing which follows the BB 'line | wire in (A).

Hereinafter, with reference to FIGS. 1 to 12, a method for manufacturing a light receiver, a balanced light receiver, and a light receiver according to an embodiment of the present invention will be described with reference to the drawings.
The light receiver according to the present embodiment is a high-speed light receiver used for optical communication, for example, and is a waveguide type high-speed light receiver.
For example, as shown in FIGS. 1A and 1B, the light receiver of the present embodiment includes an input waveguide core layer 1, a guide waveguide core layer 2 connected to the input waveguide core layer 1, and a guide. And a light absorption layer 3 partially provided above the waveguide core layer 2. The core layer is also referred to as an optical waveguide layer. The light absorption layer is also referred to as a light receiving part.

In particular, the light absorption layer 3 is provided on one side in the width direction with respect to the center position in the width direction of the input waveguide core layer 1 and above the guide waveguide core layer 2.
That is, the light absorption layer 3 is provided at a position that does not straddle the center line of the fundamental mode incident on the input waveguide [indicated by symbol X in FIG. It is less than half the width of the portion connected to the input waveguide core layer 1 and is provided above the guide waveguide core layer 2 so as to extend along the light propagation direction.

  There is a peak of the light intensity distribution (propagation light distribution) of the input light on the center line of the fundamental mode incident on the input waveguide, that is, at the center position in the width direction of the input waveguide core layer 1, and the light intensity is locally growing. If the light absorption layer 3 is provided at this position, a large number of photocarriers are generated in the light absorption layer and accumulated in the light absorption layer, a shielding electric field is generated, and high-speed characteristics deteriorate. In order to suppress deterioration of the high-speed characteristics, the above-described configuration is employed. In FIG. 1B, the propagation light distribution is indicated by Y.

Thus, in order to suppress the deterioration of the high-speed characteristics, the position of the light absorption layer 3 is shifted to one side in the width direction with respect to the center position in the width direction of the input waveguide core layer 1, for example, a light receiver. Even when the input light intensity to 4 is increased, the high-speed characteristics can be maintained.
For example, in a balanced photoreceiver, when local light having a high light intensity is incident to achieve further low noise (that is, when the input light intensity to the photoreceiver is increased), a large number of photocarriers are generated in the light absorption layer. Generated and accumulated in the light absorption layer, a shielding electric field is generated. As a result, the response speed is lowered and the high-speed characteristics are deteriorated. By using the balance type light receiver [see, for example, FIG. 9A and FIG. 9B] by using it, it is possible to suppress deterioration of the high-speed characteristics and maintain the high-speed characteristics.

  In the present embodiment, as shown in FIG. 1B, the input waveguide core layer 1 is connected to the constant width portion 1A having a constant width and the constant width portion 1A, and from the constant width portion 1A side. And a tapered portion 1B having a width that increases toward the guide waveguide core layer 2 side. For this reason, the width of the portion of the guide waveguide core layer 2 connected to the input waveguide core layer 1 connected to the input waveguide core layer 1 is also widened.

In this way, by expanding the propagation light, it is possible to suppress the light intensity at the input end [incident end; left end in FIG. It is possible to reduce the density of photocarriers generated by the above.
As a result, even if the input light intensity to the light receiver 4 is increased, for example, a decrease in response speed due to accumulation of carriers can be suppressed and high-speed characteristics can be maintained.

  Further, as shown in FIG. 1B, the guide waveguide core layer 2 has a width that decreases from the input waveguide core layer 1 side to the opposite side. That is, the width of the guide waveguide core layer 2 decreases along the light propagation direction. Here, in the guide waveguide core layer 2, one side surface in the width direction is a side surface parallel to the light propagation direction, and the other side surface in the width direction is in the light propagation direction. Including diagonal sides.

  Thereby, the fall of a sensitivity can be suppressed. That is, not only light is incident from the incident end to the light absorption layer 3 extending in the light propagation direction, but also light reflected by the oblique side surface of the guide waveguide core layer 2 can be incident from the side. Since the light can be absorbed efficiently, the decrease in sensitivity is suppressed compared to the case where the width of the guide waveguide core layer 2 is not decreased along the light propagation direction and is constant. can do.

Further, as shown in FIGS. 1A and 1B, the guide waveguide core layer 2 includes a doping region 2A provided below the light absorption layer 3, an input waveguide core layer 1, and a doping region. And an undoped region 2B provided between the side portions of 2A. The entire input waveguide core layer 1 is an undoped region.
Thereby, the fall of a sensitivity can be suppressed. In other words, free carrier absorption (free carrier loss) that does not contribute to photocarriers can be suppressed, and a decrease in sensitivity can be suppressed as compared with a case where the entire region is a doping region.

In addition, a first electrode 5 connected to one side in the thickness direction of the light absorption layer 3 and a second electrode 6 connected to the other side in the thickness direction of the light absorption layer 3 are provided.
Here, as shown in FIG. 1A, the light absorption layer 3 includes a first conductivity type doping region 3A doped with the first conductivity type on the surface side.
The guide waveguide core layer 2 extends from the lower side of the light absorption layer 3 to one side in the width direction, and sandwiches the light absorption layer 3 with the second conductivity type doping region 2AX doped with the second conductivity type. Provided on the surface side of the undoped region 2B provided on the opposite side of one side and the portion extending to one side of the second conductivity type doping region 2AX, the second conductivity type at a higher concentration than the other portion And a high-concentration second conductivity type doping region 2AY.

The first electrode 5 is provided on the first conductivity type doping region 3A, and the second electrode 6 is provided on the high-concentration second conductivity type doping region 2AY.
Specifically, the input waveguide core layer 1 and the guide waveguide core layer 2 are silicon (Si) core layers (Si waveguide core layers).
The light absorption layer 3 is a Ge layer. The light absorption layer 3 may be a semiconductor light absorption layer containing Ge. Further, a passivation film (for example, Si film) 15 may be provided so as to cover the surface of the light absorption layer 3 [see, for example, FIG. 8J].

The light absorption layer 3 is provided with an n-type doping region (here, an n ⁺ -type doping region doped with an n-type impurity at a high concentration) as the first conductivity type doping region 3A. The region is an undoped region. In the case where the passivation film 15 covering the surface of the light absorption layer 3 is provided, an n-type doping region may be provided in the passivation film 15 as the first conductivity type doping region 3A [see, for example, FIG. 8J. ]. An n-side electrode is provided as the first electrode 5 on the n-type doping region 3A (here, n ⁺ -type doping region; first conductive semiconductor layer). That is, the n-side electrode 5 is provided on the n-type doping region 3 </ b> A (contact region) provided on the surface side of the light absorption layer 3.

The guide in the waveguide core layer 3, the second conductive type doped region 2AX, p ⁺ -type doped region is provided, as a high-concentration second conductivity-type doped region 2aY, p ⁺⁺ type doping region is provided The other region is an undoped region 2B. A p-side electrode is provided as the second electrode 6 on the p ⁺⁺ type doping region (second conductivity type semiconductor layer) 2AY. That is, the p-side electrode 6 is adjacent to the light absorption layer 3 on the p ⁺⁺ type doping region (contact region) 2AY provided on the surface side opposite to the undoped region 2B with the light absorption layer 3 interposed therebetween. Is provided.

Further, the periphery of these is covered with SiO ₂ cladding layers 9, 12, and 16 [see, for example, FIG. 8J].
That is, on the Si substrate 8, SiO ₂ cladding layer 9, Si core layer 1, SiO ₂ cladding 12 and 16 layers are laminated, Si core layer 1 and the SiO ₂ cladding layer 9,12,16 An input waveguide composed of the input waveguide core layer 1 and the clad layers 9, 12, 16 and the guide waveguide core layer 2 and the clad layers 9, 12, 16 A guide waveguide consisting of the above is configured [see, for example, FIG. 8J].

As described above, the light receiving device 4 is configured by monolithically integrating the semiconductor light receiving element 7 including the light absorption layer 3, the n-side electrode 5, and the p-side electrode 6 on the semiconductor optical waveguide. For this reason, the light receiver 4 of the present embodiment is a light receiver made of a semiconductor.
As shown in FIGS. 1A and 1B, the guide waveguide core layer 2 constituting the semiconductor optical waveguide is a region where the semiconductor light receiving element 7 is provided (light absorption layer 3, n-side electrode 5). And the periphery of the p-side electrode 6) is a doping region 2A, and the other region is an undoped region 2B.

  That is, the guide waveguide core layer 2 is provided with the doping region 2A partially along the light propagation direction on one side in the width direction, and compared with the case where the entire region is doped. The range of 2A is narrow, and the width of the doping region 2A [reference symbol B in FIG. 1A] with respect to the width of the guide waveguide core layer 2 [indicated by the arrow A in FIG. 1A] [Indicated by the arrow] is significantly narrower. Note that the width of the light absorption layer 3 [indicated by symbol C in FIG. 1A] is narrower than the width of the guide waveguide core layer 2 [indicated by symbol A in FIG. 1A]. .

Thereby, free carrier absorption (loss) which does not contribute to the photocarrier in the expanded propagation light can be suppressed to be small, and a decrease in sensitivity (light receiving sensitivity) can be suppressed.
In addition, when doping almost the entire guide waveguide core layer 2, the doping concentration is set as low as possible to suppress free carrier absorption as much as possible and suppress a decrease in sensitivity [for example, in FIG. see region indicated by p ⁺ ]. However, in this method, the sheet resistance between the light absorption layer 102 and the electrode 104 connected via the doping region 105 indicated by p ⁺ increases, the CR time constant increases, and the response speed decreases. For this reason, the high-speed characteristics are deteriorated.

  On the other hand, as described above, only the region where the semiconductor light-receiving element 7 is provided is the doped region 2A, and the other region is the undoped region 2B, thereby suppressing free carrier absorption and suppressing a decrease in sensitivity. can do. For this reason, the doping concentration in the doping region 2A can be set higher than in the case of doping almost the entire guide waveguide core layer 2 [see, for example, FIG. 11A and FIG. 11B]. A path through which carriers flow as current can be effectively shortened, and sheet resistance can be lowered. As a result, a decrease in response speed due to the CR time constant can be suppressed, and deterioration of high-speed characteristics can be suppressed.

As shown in FIG. 1B, the width of the guide waveguide core layer 2 on the other side of the region other than the region where the semiconductor light receiving element 7 is provided, that is, on the opposite side to the one side in the width direction, is It decreases along the light propagation direction.
As a result, the light reflected by the oblique side surface of the guide waveguide core layer 2 can also be incident on the light absorption layer 3 extending in the light propagation direction from the side, so that the light can be efficiently absorbed. Can be suppressed.

By the way, since the light receiver 4 of the present embodiment is configured as described above, the mode diameter of the light propagating through the preceding optical circuit is the same as the width of the optical waveguide (input waveguide and guide waveguide). In the region where the waveguide width is the same, it propagates like parallel light.
When reaching the light absorption layer 3 (light receiving portion), only a part of the light is absorbed at the incident end.
Further, since the width of the guide waveguide core layer 2 where the light receiving portion 3 is not formed decreases along the light propagation direction, the propagated light is reflected by the oblique side surface of the guide waveguide core layer 2, It is gradually absorbed from the side (side surface) of the light receiving unit 3.

Further, the angle θ of the oblique side surface of the guide waveguide core layer 2 may be set as follows. The guide waveguide core layer 2 is also referred to as a fan-type guide waveguide core layer.
Here, as shown in FIG. 2A, the light (light beam; plane wave) propagated in the fundamental mode is reflected at an angle φ ₁ on the oblique side surface of the guide waveguide core layer 2 (here, the Si layer). It is assumed that the light is incident on the light absorption layer 3 (here, the Ge layer) extending in the light propagation direction at an angle φ ₂ from the side.

FIG. 2 (B) shows the reflectance when entering from the Si waveguide core layer 2 to the SiO ₂ cladding layer by approximating light rays. In FIG. 2B, the solid line Rs indicates the reflectance of s-polarized light, and the solid line Rp indicates the reflectance of p-polarized light.
FIG. 2C shows the transmittance when entering the Ge layer 3 from the Si waveguide core layer 2 by approximating light rays. In FIG. 2C, the solid line Ts indicates the transmittance of s-polarized light, and the solid line Tp indicates the transmittance of p-polarized light.

As shown in FIG. 2 (B), the light having propagated is when entering the Si waveguide core layer 2 to the SiO ₂ cladding layer, so that the incident angle phi ₁ is reflected almost as long to about 37 ° or more.
For this reason, the incident angle φ ₁ with respect to the oblique side surface of the guide waveguide core layer 2 may be set to 37 ° or more (incident angle φ ₁ ≧ 37 °).
Here, since φ ₁ = 90 ° −θ, in order to satisfy the relationship of the incident angle φ ₁ ≧ 37 °, θ is set to 53 ° or less.

As shown in FIG. 2C, when the light reflected by the oblique side surface of the guide waveguide core layer 2 enters the Ge layer 3 from the Si waveguide core layer 2, the incident angle φ ₂ is about 45. If it is less than °, it is almost transparent.
For this reason, the incident angle φ ₂ when entering the light absorbing layer 3 from the side may be set to 45 ° or less (incident angle φ ₂ ≦ 45 °).

Here, in order to satisfy the relationship of the incident angle φ ₂ ≦ 45 °, θ is set to 22.5 ° or more.
From these results, it is preferable to set θ to 22.5 ° or more and 53 ° or less (22.5 ° ≦ θ ≦ 53 °).
Further, when a light intensity simulation was performed in order to confirm the effect of the light receiver 4 of the present embodiment, results as shown in FIGS. 3A and 3B were obtained.

Here, FIGS. 3A and 3B show a general light receiver having the structure shown in FIGS. 11A and 11B and the light receiver of the present embodiment [FIG. FIG. 1B shows the result of calculating the light intensity in each light receiver in order to confirm the light absorption in FIG.
3A shows the result of calculating the light intensity in a general light receiver having the structure shown in FIGS. 11A and 11B. FIG. The result of having calculated the light intensity in the light receiver [refer to Drawing 1 (A) and Drawing 1 (B)] of an embodiment is shown. Further, here, in order to clarify the difference, the comparison is made with the same light receiving area (the area of the upper surface of the light absorption layer; here 8 × 30 μm ² ). 3A and 3B, the arrow indicates the length of the light absorption layer, that is, the element length of the light receiving element.

As shown in FIGS. 3 (A) and 3 (B), the light propagating through the optical waveguide in any light receiver starts to be absorbed at the incident end of the light absorption layer (here, the Ge light receiving portion), The light intensity decreases as it propagates through the light receiving element.
First, in a general photodetector having the structure shown in FIGS. 11A and 11B, the light intensity decreases exponentially as shown in FIG. 3A, and the element length is about 30 μm. After propagating through the light, the light intensity decreased by 90% and the quantum efficiency was 90%.

In particular, in FIG. 3A, the dotted line portion has a large inclination, and most of the light is absorbed and a large number of photocarriers are generated in this region, that is, the incident end of the light absorption layer. Recognize.
On the other hand, in the light receiver of this embodiment [see FIGS. 1A and 1B], as shown in FIG. 3B, the light intensity decreases according to the distance, but FIG. 11), the light intensity is reduced by 75% after propagation through an element length of about 30 μm, and the quantum efficiency is 75%. It was.

  In particular, in FIG. 3B, the dotted line portion has a gentle slope, and light absorption at this region, that is, the incident end of the light absorption layer 3 is not abrupt, and there are few photocarriers generated. It can be seen that the generation of is suppressed to about half or less, and the cause of high-speed characteristic deterioration is suppressed. This is because the position of the light absorption layer 3 is shifted to one side in the width direction with respect to the center position in the width direction of the input waveguide core layer 2.

In addition, it can be seen that in the terminal region of the light absorption layer 3, the degree of decrease in light intensity is moderate, light is absorbed, and the decrease in sensitivity is suppressed. This is because the guide waveguide core layer 2 is narrowed from the input waveguide core layer 1 side to the opposite side.
In the light receiver of this embodiment [see FIGS. 1 (A) and 1 (B)], the quantum efficiency is lowered, but this is due to the angle (attenuation) of the oblique side surface of the guide waveguide core layer 2. Angle) or by optimizing the element width, element length, etc. of the light receiving element 7, the same level as that of a general light receiver having the structure shown in FIGS. 11 (A) and 11 (B). It is possible to achieve quantum efficiency.

  For example, the width of the input waveguide core layer 1 is increased to 18 μm, that is, the width of the portion connecting the input waveguide core layer 1 and the guide waveguide core layer 2 is 18 μm, and the light receiving unit 3 (Ge layer; light absorption layer) ) Is 4 μm and the length (element length) is 60 μm, the quantum efficiency is improved by increasing the element length. In this case, since the light receiving area is the same as the light intensity calculated in FIG. 3B, the element capacity is kept low, and both high speed and high efficiency (high sensitivity characteristics) are achieved.

The guide waveguide core layer 2 is not limited to the above-described configuration.
For example, as shown in FIG. 4, the guide waveguide core layer 2 has a width that decreases from the input waveguide core layer 1 side to the opposite side, and the width changes stepwise. Also good. That is, the guide waveguide core layer 2 may be configured such that the angle of the oblique side surface gradually changes and the width gradually decreases along the light propagation direction. Here, the angle of the oblique side surface of the guide waveguide core layer 2 is changed stepwise such as θ ₁ , θ ₂ , and θ ₃ (θ ₁ > θ ₂ > θ ₃ ).

With this configuration, the light incident from the side on the light absorption layer 3 (here, the Ge layer) can be spread along the length direction of the light absorption layer 3, and is concentrated and incident locally. Can be suppressed.
That is, as shown in FIG. 5A, when the angle of the oblique side surface of the guide waveguide core layer 2 is constant, the light is reflected by the oblique side surface of the guide waveguide core layer 2 and is laterally reflected by the light absorption layer 3. The light incident from the light enters the region surrounded by the dotted line in the figure.

  On the other hand, as shown in FIG. 5B, when the angle of the oblique side surface of the guide waveguide core layer 2 changes stepwise, the guide waveguide core layer where the angle changes stepwise. The light is reflected at different angles on the two oblique side surfaces, spreads along the length direction of the light absorption layer 3, and enters the light absorption layer 3 from the side. For this reason, the light incident on the light absorption layer 3 from the side enters the region surrounded by the dotted line in the figure, and the region where the light is incident widens along the length direction of the light absorption layer 3. . Thereby, it can suppress that light concentrates on the light absorption layer 3, and light enters.

Here, FIG. 5C shows the angles of the oblique side surfaces of the guide waveguide core layer 2 as θ ₁ = 20 °, θ ₂ = 15 °, θ ₃ = 10 ° (θ ₁ > θ ₂ > θ ₃ ). The result of the three-dimensional BPM (Beam Propagation Method) simulation in the case of changing as shown in FIG.
In FIG. 5C, the white frame is the light absorption layer 3 (here, the Ge layer), and there is no portion where the light incident on the light absorption layer 3 from the side is locally high in intensity. It can be seen that the light intensity is also suppressed in the absorption layer 3.

  For example, as shown in FIG. 6, the guide waveguide core layer 2 includes a width changing portion 2 </ b> X whose width is narrowed from the input waveguide core layer 1 side to the opposite side, and a width changing portion 2 </ b> X. It is good also as what is provided with the constant width part 2Y which continues and is constant in width. That is, the guide waveguide core layer 2 may have a constant width in parallel with the length direction of the light absorption layer 3 after its width decreases along the light propagation direction.

As a result, all the light incident on the light absorption layer 3 from the side can be sufficiently absorbed so that high quantum efficiency can be realized, and the sensitivity can be improved. In particular, in FIG. 6, light incident in the vicinity of the region surrounded by the dotted line also propagates in the light absorption layer 3 over a distance longer than the absorption length, so that high quantum efficiency can be realized and sensitivity can be improved. Can do.
For example, as shown in FIGS. 7A and 7B, the thickness (film thickness) of the portion of the guide waveguide core layer 2 where the high-concentration second conductivity type doping region 2AY is provided is set. It may be thinner than other parts. That is, the thickness of the p ⁺⁺ type doping region 2AY of the guide waveguide core layer 2 immediately below the p-side electrode 6 may be reduced to form a thin film p ⁺⁺ type Si layer.

  In this case, the guide waveguide core layer 2 is provided below the light absorption layer 3 and has a second conductivity type doping region 2AX doped to the second conductivity type and one of the width directions with respect to the light absorption layer 3. The high-concentration first layer is provided in a portion where the thickness on the side is thinner than the other portion so as to be continuous with the second-conductivity-type doping region 2AX and is doped to the second-conductivity type at a higher concentration than the second-conductivity-type doping region 2AX. A two-conductivity-type doping region 2AY and an undoped region 2B provided on the opposite side of one side with the light absorption layer 3 interposed therebetween are provided.

In this case, the width of the second conductivity type doping region 2AX [reference symbol B in FIG. 7A] with respect to the width of the guide waveguide core layer 2 [indicated by the arrow A in FIG. 7A]. [Indicated by the arrow] is significantly narrower. In addition, the width of the light absorption layer 3 [indicated by symbol C in FIG. 7A] is narrower than the width of the guide waveguide core layer 2 [indicated by symbol A in FIG. 7A]. .
For example, the p ⁺⁺ type doping region 2AY can be formed by half-etching the guide waveguide core layer 2 and doping this portion with a p-type impurity at a high concentration.

This makes it difficult for light propagating in the guide waveguide core layer 2 to leak into the high-concentration second conductivity type doping region 2AY (region with high carrier concentration), and loss in the high-concentration second conductivity type doping region 2AY. Can be reduced.
Next, a method for manufacturing the light receiver according to the present embodiment will be described.
The optical receiver manufacturing method according to the present embodiment includes a step of providing an input waveguide core layer 1 and a guide waveguide core layer 2 connected to the input waveguide core layer 1, and a center in the width direction of the input waveguide core layer 1. And a step of providing the light absorption layer 3 on one side in the width direction with respect to the position and above the guide waveguide core layer 2 [see, for example, FIGS. 8A to 8J].

Further, in the step of providing the guide waveguide core layer 2, it is preferable to provide the guide waveguide core layer 2 so that the width becomes narrower from the input waveguide core layer 1 side to the opposite side [for example, FIG. ), FIG. 1 (B)].
Further, in the step of providing the guide waveguide core layer 2, a doping region 2A is provided in the guide waveguide core layer 2 on one side in the width direction with respect to the center position in the width direction of the input waveguide core layer 1, and the input waveguide The guide waveguide core layer 2 between the core layer 1 and the side of the doping region 2A is an undoped region 2B, and in the step of providing the light absorption layer 3, the light absorption layer 3 may be provided above the doping region 2A. Preferred [see, for example, FIGS. 8A to 8J].

Further, in the step of providing the input waveguide core layer 1, the constant width portion 1 </ b> A having a constant width and the constant width portion 1 </ b> A are connected to the guide waveguide core layer 2 side from the constant width portion 1 </ b> A side. It is preferable to provide an input waveguide core layer 1 including a tapered portion 1B having a wider width [see, for example, FIGS. 1A and 1B].
Hereinafter, a specific example will be described with reference to FIGS. 8 (A) to 8 (J).

8A to 8J are cross-sectional views along the line AA ′ in FIG. 1B.
First, as shown in FIG. 8A, an SiO ₂ layer 12 is provided on an SOI substrate 11 on which an Si layer 10 is provided on an Si substrate 8 with a SiO ₂ layer 9 interposed therebetween, and a resist 13 is patterned. .
Next, as shown in FIG. 8B, using the resist pattern, etching is performed up to the Si layer 10 to form the Si waveguide core layer that becomes the input waveguide core layer 1 and the guide waveguide core layer 2. .

Next, as shown in FIG. 8C, a p-type impurity is doped into a part of the Si waveguide core layer to be the guide waveguide core layer 2 to form a p ⁺ -type doping region (p ⁺ layer; p ⁺ Type Si layer) 2AX is selectively formed. As a result, the doping region 2A and the undoped region 2B are formed in the Si waveguide core layer to be the guide waveguide core layer 2.
Next, as shown in FIG. 8D, a part of the p ⁺ -type doping region 2AX is selectively etched to reduce its thickness to about 100 nm, for example.

Next, as shown in FIG. 8E, the thinned p ⁺ -type doping region 2AX is further doped with a p-type impurity at a high concentration to form a p ^{+ +} -type doping region (p ^{+ +} layer; p ^{+ +} -type Si). Layer) 2AY is selectively formed.
Next, as shown in FIG. 8F, a selective growth window 14 is formed above the p ⁺ -type doping region 2AX.

Next, as shown in FIG. 8G, a Ge layer to be the light absorption layer 3 (light receiving layer; light receiving portion) is selectively grown on the p ⁺ -type doping region 2AX.
Next, as shown in FIG. 8H, a Si film 15 as a passivation film is formed so as to cover the surface of the Ge layer 3.
Next, as shown in FIG. 8 (I), an n ⁺ type doping region (n ⁺ layer; n ⁺ type Si layer) 3A is formed by doping the Si film 15 above the Ge layer 3 with an n type impurity. To do.

Next, as shown in FIG. 8 (J), after covering the whole with the SiO ₂ layer 16 and patterning, the n-side electrode 5 is formed on the n ⁺ -type doping region 3A, and the p ⁺ -type doping region 2AY is formed. A p-side electrode 6 is formed thereon.
In this way, the light receiver 4 of this embodiment can be manufactured.
By the way, the light receiver 4 configured as described above can be applied to a balanced light receiver.

  In this case, as shown in FIG. 9A, the balanced light receiver 17 has a structure in which two light receivers 4 (4A, 4B) configured as described above are arranged in parallel. One electrode (first electrode) 5A provided in the light receiver (first light receiver) 4A and one electrode (third electrode) 6B provided in the other light receiver (second light receiver) 4B are connected to the signal line 18 ( Here, the other electrode (second electrode) 6A provided in one light receiver 4A is connected to the ground line (first ground line) 19 and provided in the other light receiver 4B. The other electrode (fourth electrode) 5 </ b> B may be configured to be connected to the ground line (second ground line) 20. Here, bonding pads 21 to 23 are provided on the signal line 18 and the ground lines 19 and 20, respectively. The circuit configuration of the balance type light receiver 17 configured as described above is as shown in FIG.

  In this case, the balanced light receiver 17 includes the first light receiver 4A and the second light receiver 4B, and the first light receiver 4A is configured as described above, that is, the first input waveguide core layer and the first light receiver 4A. A first guide waveguide core layer continuous with the first input waveguide core layer, and a first guide waveguide core on one side in the width direction with respect to the center position in the width direction of the first input waveguide core layer. A first light absorption layer provided above the layer, a first electrode connected to one side in the thickness direction of the first light absorption layer, and the other side in the thickness direction of the first light absorption layer. The second light receiver 4B is configured as described above, that is, the second input waveguide core layer and the second input waveguide core layer connected to the second input waveguide core layer. The guide waveguide core layer and the second input waveguide core layer on one side in the width direction with respect to the center position in the width direction, the second guide A second light absorbing layer provided above the waveguide core layer; a third electrode connected to one side in the thickness direction of the second light absorbing layer; and the other in the thickness direction of the second light absorbing layer. A fourth electrode connected to the first electrode, a signal line connected to the first electrode and the third electrode, a first ground line connected to the second electrode, and a fourth electrode. Are connected to the second ground line.

The first guide waveguide core layer has a width that decreases from the first input waveguide core layer side to the opposite side, and the second guide waveguide core layer is the same as the second input waveguide core layer. The width is preferably narrower from the side toward the opposite side.
The first guide waveguide core layer is provided between the first doping region provided below the first light absorption layer, and the first input waveguide core layer and the side of the first doping region. And a second guide waveguide core layer including a second doping region provided below the second light absorption layer, a second input waveguide core layer, and a side portion of the second doping region. And a second undoped region provided between the two.

  The first input waveguide core layer is connected to a first constant width portion having a constant width and a first constant width portion, and from the first constant width portion side to the first guide waveguide core layer side. The second input waveguide core layer is connected to the second constant width portion having a constant width, the second constant width portion, and the second constant width portion. It is preferable to include a second taper portion having a width that increases from the constant width portion side toward the second guide waveguide core layer side.

By the way, a receiver or a transmitter / receiver can be configured as including the balance type light receiver 17 configured as described above, that is, the balance type light receiver 17 to which the light receiver 4 configured as described above is applied. .
For example, as shown in FIG. 10, a Si thin-line optical integrated circuit (Si optical waveguide) and the light receiver 4 (balanced light receiver 17) configured as described above are monolithically integrated on a Si substrate 30 and digitally integrated. A coherent transceiver 31 can be configured.

Here, the portion 36 functioning as a receiver includes four balanced light receivers 17A to 17D configured as described above, two 90 ° hybrid elements 32A and 32B, and one polarization beam splitter (PBS). An element 33 and one polarization rotation element 34 are provided, and these are connected by a Si optical waveguide 35.
The portion 37 functioning as a transmitter includes two IQ modulators 38 and 39, one polarization combiner element 40, and one polarization rotation element 41, which are connected by a Si optical waveguide 42. ing. Here, the two IQ modulators 38 and 39 are configured by connecting two silicon modulators (Mach-Zehnder modulators) 43A, 43B, 44A, and 44B in parallel, respectively.

The local light input through the optical fiber 45 and the lens 46 is branched into two through the mode conversion waveguide 47, one of which functions as a receiver 36 and the other as a transmitter. Input to part 37.
Further, in the portion 36 functioning as a receiver, the local light is further branched into two, and then input to each of the two 90 ° hybrid elements 32A and 32B.

  In addition, signal light (received signal) input through the optical fiber 48 and the lens 49 passes through the mode conversion waveguide 50, and is polarized by two polarization beams (TE polarized wave and The TM polarized light is input to one of the two 90 ° hybrid elements 32A and 32B, and the TM polarized light is converted into TE polarized light by the polarization rotating element 34. Is input to the other of the two 90 ° hybrid elements 32A and 32B.

In each of the two 90 ° hybrid elements 32A and 32B, the local light and the signal light are mixed and processed, and the light receivers are connected to the four output ports of the respective 90 ° hybrid elements 32A and 32B. It is converted into an electrical signal (photoelectric conversion) by 4A to 4H (here, Ge light receiver) and output.
Here, four balance type light receivers 17A to 17D are constituted by eight light receivers 4A to 4H, and four balance type light receivers 17A to 17D are connected to two 90 ° hybrid elements 32A and 32B. Electrical signals are output from the four balanced light receivers 17A to 17D.

In the portion 37 functioning as a transmitter, the local light is further branched into two, and then processed by the two IQ modulators 38 and 39 to be converted into independent QPSK signals (TE-polarized light).
One of these two QPSK signals is converted into TM polarized light by the polarization rotation element 41, and combined with the other TE polarized light by the polarization combiner element 40 (polarization multiplexing). Then, signal light (transmission signal) is output to the optical fiber 53 through the mode conversion waveguide 51 and the lens 52.

Therefore, according to the light receiving device, the balance type light receiving device, and the light receiving device manufacturing method according to the present embodiment, for example, when the input light intensity to the light receiving device is large, it is possible to suppress the deterioration of the high speed characteristics.
By the way, the reason why the above configuration is adopted is as follows.
Digital coherent transmission is considered to be a powerful communication method in the future high-speed and large-capacity optical network.

For example, there is a digital coherent optical receiver in which a phase heterodyne optical circuit and two balanced light receivers are integrated in an optical circuit unit.
Recently, research and development of a receiver in which a Si thin-line optical integrated circuit and a Ge light receiver are monolithically integrated on a Si substrate have been conducted.
The balanced light receiver can obtain a highly sensitive signal by detecting beat light with reference to the phase of signal light and local light.

In such a balanced light receiver, in order to realize further low noise, it is necessary to make local light having a strong light intensity incident on the light absorption layer (light receiving element) and detect the beat light.
However, when strong light is incident on the light absorption layer, a large number of photocarriers are generated in the light absorption layer and accumulated in the light absorption layer, thereby generating a shielding electric field, resulting in a decrease in response speed. It will be. That is, there is a problem that the high-speed characteristics deteriorate when the input light intensity to the light receiver increases.

Further, for example, in a light receiver as shown in FIGS. 11A and 11B, the width of the waveguide core layer 101 is increased at the light input portion 100 of the light receiver, as can be seen from FIG. 11A. In this way, the width of the propagation light is increased.
In this structure, it is considered that the influence of the above-described accumulation of photocarriers can be reduced by reducing the density of photocarriers generated in the light absorption layer 102 in the light receiver.

However, in this structure, although there is a difference corresponding to the width of the p ⁺ layer 103 and the p-side electrode 104 thereon, the width of the waveguide core layer 101 [indicated by reference sign B in FIG. The width of the light absorption layer 102 [indicated by symbol A in FIG. 11B] is similarly expanded. A doped region (p ⁻ layer) 105 doped with a p-type impurity is provided over almost the entire width of the expanded waveguide core layer 101. Note that an upper portion of the light absorption layer 102 is an n ⁺ layer 106, and an n-side electrode 107 is provided thereon.

For this reason, this dopant causes free carrier absorption that does not contribute to photocarriers, resulting in a problem that the light receiving sensitivity is reduced as a loss.
In order to suppress this free carrier absorption as much as possible, it is conceivable to set the doping concentration of the p-type impurity as low as possible.
However, in this case, sheet resistance is generated between the light absorption layer (light receiving portion) 102 and the p-side electrode 104, and the CR time constant increases, which causes a reduction in response speed.

12A and 12B, the light absorption layer 109 is provided on a part of the expanded waveguide core layer 108, and the width of the waveguide core layer 108 [ The width of the light absorption layer 109 [indicated by reference A in FIG. 12B] is narrower than that indicated by reference B in FIG. 12B (B> A). Note that a p ⁻ layer 111, a p ⁺ layer 112, and a p side electrode 113 are sequentially provided on the light absorption layer 109, and an n side electrode 114 is provided on an n ⁺ layer 110 described later.

As shown in FIG. 12A, the width of the waveguide core layer 108 is narrowed in the light propagation direction. This is because as the light propagates, the propagation light is collected as much as necessary in consideration of the fact that the intensity of the light decreases due to absorption by the light absorption layer 109.
However, even in this structure, as in the case of the light receiver as shown in FIGS. 12A and 12B, the entire waveguide core layer 108 is doped in the width direction to become an n ⁻ layer. Therefore, there is a problem that absorption that does not contribute to the photocarrier, that is, free carrier loss occurs in the spread propagation light. In particular, in this structure, an n ⁺ layer 110 is provided as shown in FIG. 12B to reduce the resistance. However, this problem becomes significant in the n ⁺ layer 110.

In addition, since the doping region (n ⁻ layer 108, n ⁺ layer 110) is also provided near the center where the intensity of the expanded propagation light is large, the influence of free carrier loss becomes large.
Therefore, in the present embodiment, the configuration as described above is adopted.
In addition, this invention is not limited to the structure described in embodiment mentioned above, A various deformation | transformation is possible in the range which does not deviate from the meaning of this invention.

Hereinafter, additional notes will be disclosed regarding the above-described embodiment.
(Appendix 1)
An input waveguide core layer;
A guide waveguide core layer connected to the input waveguide core layer;
A light receiver comprising: a light absorption layer provided on one side in the width direction with respect to the center position in the width direction of the input waveguide core layer and above the guide waveguide core layer.

(Appendix 2)
The light receiver according to appendix 1, wherein the guide waveguide core layer has a width that decreases from the input waveguide core layer side to the opposite side.
(Appendix 3)
The light receiver according to appendix 2, wherein the guide waveguide core layer has a width that changes stepwise.

(Appendix 4)
The guide waveguide core layer includes a width changing portion that is narrowed from the input waveguide core layer side to the opposite side, and a width constant portion that is continuous with the width changing portion and has a constant width. The light receiver according to claim 1, further comprising:
(Appendix 5)
The guide waveguide core layer includes a doping region provided below the light absorption layer, and an undoping region provided between the input waveguide core layer and a side portion of the doping region. The light receiver according to any one of appendices 1 to 4, which is characterized by the following.

(Appendix 6)
A first electrode connected to one side in the thickness direction of the light absorption layer;
The light receiver according to any one of appendices 1 to 5, further comprising a second electrode connected to the other side in the thickness direction of the light absorption layer.
(Appendix 7)
The light absorption layer includes a first conductivity type doping region doped to the first conductivity type on the surface side,
The guide waveguide core layer extends from the lower side of the light absorption layer to one side in the width direction, the second conductivity type doping region doped with the second conductivity type, and the one of the light absorption layers Provided on the surface side of the undoped region provided on the opposite side of the side and the portion extending to one side of the second conductivity type doping region, and doped to the second conductivity type at a higher concentration than the other portion. And a high concentration second conductivity type doping region,
A first electrode on the first conductivity type doping region;
The light receiver according to any one of appendices 1 to 4, further comprising a second electrode on the high-concentration second conductivity type doping region.

(Appendix 8)
The light absorption layer includes a first conductivity type doping region doped to the first conductivity type on the surface side,
The guide waveguide core layer is provided below the light absorption layer, has a second conductivity type doping region doped with a second conductivity type, and a thickness on one side in the width direction with respect to the light absorption layer. Is provided in a portion thinner than the other portion so as to be continuous with the second conductivity type doping region, and is doped to the second conductivity type at a higher concentration than the second conductivity type doping region. A region, and an undoped region provided on the opposite side of the one side across the light absorption layer,
A first electrode on the first conductivity type doping region;
The light receiver according to any one of appendices 1 to 4, further comprising a second electrode on the high-concentration second conductivity type doping region.

(Appendix 9)
The input waveguide core layer is connected to the constant width portion having a constant width and the constant width portion, and the width increases from the constant width portion side toward the guide waveguide core layer side. The optical receiver according to any one of appendices 1 to 8, further comprising a tapered portion.
(Appendix 10)
A first receiver;
A second receiver,
The first light receiver
A first input waveguide core layer;
A first guide waveguide core layer connected to the first input waveguide core layer;
A first light absorption layer provided on one side in the width direction with respect to the center position in the width direction of the first input waveguide core layer and above the first guide waveguide core layer;
A first electrode connected to one side in the thickness direction of the first light absorption layer;
A second electrode connected to the other side in the thickness direction of the first light absorption layer,
The second light receiver
A second input waveguide core layer;
A second guide waveguide core layer connected to the second input waveguide core layer;
A second light absorbing layer provided on one side in the width direction with respect to the center position in the width direction of the second input waveguide core layer and above the second guide waveguide core layer;
A third electrode connected to one side of the second light absorption layer in the thickness direction;
A fourth electrode connected to the other side in the thickness direction of the second light absorption layer,
Furthermore, a signal line to which the first electrode and the third electrode are connected;
A first ground line to which the second electrode is connected;
And a second ground line to which the fourth electrode is connected.

(Appendix 11)
The width of the first guide waveguide core layer is narrowed from the first input waveguide core layer side to the opposite side,
11. The balanced light receiver according to appendix 10, wherein the width of the second guide waveguide core layer is narrowed from the second input waveguide core layer side to the opposite side.

(Appendix 12)
The first guide waveguide core layer is provided between a first doping region provided below the first light absorption layer and between the first input waveguide core layer and a side portion of the first doping region. A first undoped region formed,
The second guide waveguide core layer is provided between a second doping region provided below the second light absorption layer, and a side portion of the second input waveguide core layer and the second doping region. The balanced light receiver according to appendix 10 or 11, further comprising a second undoped region.

(Appendix 13)
The first input waveguide core layer is connected to a first constant width portion having a constant width and the first constant width portion, and the first guide waveguide core layer from the first constant width portion side. A first taper portion that is wider toward the side of
The second input waveguide core layer is connected to a second constant width portion having a constant width and the second constant width portion, and the second guide waveguide core layer from the second constant width portion side. The balanced light receiver according to any one of appendices 10 to 12, further comprising a second taper portion having a width that increases toward the side.

(Appendix 14)
Providing an input waveguide core layer and a guide waveguide core layer connected to the input waveguide core layer;
A step of providing a light absorption layer on one side in the width direction with respect to the center position in the width direction of the input waveguide core layer and above the guide waveguide core layer. Production method.

(Appendix 15)
The supplementary note 14 is characterized in that, in the step of providing the guide waveguide core layer, the guide waveguide core layer is provided so that a width becomes narrower from the input waveguide core layer side toward the opposite side. A method of manufacturing a photoreceiver.
(Appendix 16)
In the step of providing the guide waveguide core layer, a doping region is provided in the guide waveguide core layer on one side in the width direction with respect to the center position in the width direction of the input waveguide core layer, and the input waveguide core layer And the guide waveguide core layer between the doped region and the side of the doped region as an undoped region,
16. The method of manufacturing a light receiver according to appendix 14 or 15, wherein, in the step of providing the light absorption layer, the light absorption layer is provided above the doping region.

(Appendix 17)
In the step of providing the input waveguide core layer, a constant width portion having a constant width and a width extending from the constant width portion side toward the guide waveguide core layer side are connected to the constant width portion. The method for manufacturing a light receiver according to any one of appendices 14 to 16, wherein an input waveguide core layer including a tapered portion that is wide is provided.

1 Input waveguide core layer (Si core layer; Si waveguide core layer)
1A Constant width portion 1B Taper portion 2 Guide waveguide core layer (Si core layer; Si waveguide core layer)
2A doping region 2AX second conductivity type doping region (p ⁺ type doping region; p ⁺ layer; p ⁺ type Si layer)
2AY high concentration second conductivity type doping region (p ⁺⁺ type doping region; p ⁺⁺ layer; p ⁺⁺ type Si layer)
2B Undoped region 3 Light absorption layer (Ge layer)
3A First conductivity type doping region (n ⁺ type doping region; n ⁺ layer; n ⁺ type Si layer)
4 Receiver 4A Receiver (first receiver)
4B receiver (second receiver)
4C-4H light receiver 5 1st electrode (n side electrode)
5A electrode (first electrode)
5B electrode (4th electrode)
6 Second electrode (p-side electrode)
6A electrode (second electrode)
6B electrode (third electrode)
7 Semiconductor light receiving element 8 Si substrate 9 SiO ₂ layer (cladding layer)
10 Si layer 11 SOI substrate 12 SiO ₂ layer (cladding layer)
13 Resist 14 Window 15 Passivation film (Si film)
16 SiO ₂ layer (cladding layer)
17, 17A to 17D Balanced light receiver 18 Signal line 19 Ground line (first ground line)
20 ground line (second ground line)
21-23 Bonding pad 30 Si substrate 31 Digital coherent transceiver 32A, 32B 90 ° hybrid element 33 Polarization beam splitter (PBS) element 34 Polarization rotation element 35 Si optical waveguide 36 Part functioning as receiver 37 Transmitter Functional parts 38, 39 IQ modulator 40 Polarization combiner element 41 Polarization rotation element 42 Si optical waveguide 43A, 43B Silicon modulator (Mach-Zehnder modulator)
44A, 44B Silicon modulator (Mach-Zehnder modulator)
45 Optical fiber 46 Lens 47 Mode conversion waveguide 48 Optical fiber 49 Lens 50 Mode conversion waveguide 51 Mode conversion waveguide 52 Lens 53 Optical fiber 100 Optical input part 101 Waveguide core layer 102 Light absorption layer 103 p ⁺⁺ layer 104 p side Electrode 105 doping region (p ⁺ layer)
106 n ⁺ layer 107 n-side electrode 108 waveguide core layer 109 light absorption layer 110 110
111 p ⁻ layer 112 p ⁺ layer 113 p side electrode 114 n side electrode

Claims (9)

An input waveguide core layer;
A guide waveguide core layer connected to the input waveguide core layer;
A light receiver comprising: a light absorption layer provided on one side in the width direction with respect to the center position in the width direction of the input waveguide core layer and above the guide waveguide core layer.   2. The light receiver according to claim 1, wherein the width of the guide waveguide core layer decreases from the input waveguide core layer side to the opposite side.   The optical receiver according to claim 2, wherein a width of the guide waveguide core layer is changed stepwise.   The guide waveguide core layer includes a width changing portion that is narrowed from the input waveguide core layer side to the opposite side, and a width constant portion that is continuous with the width changing portion and has a constant width. The light receiver according to claim 1, comprising:   The guide waveguide core layer includes a doping region provided below the light absorption layer, and an undoping region provided between the input waveguide core layer and a side portion of the doping region. The light receiver according to any one of claims 1 to 4, wherein the light receiver is characterized. The light absorption layer includes a first conductivity type doping region doped to the first conductivity type on the surface side,
The guide waveguide core layer is provided below the light absorption layer, has a second conductivity type doping region doped with a second conductivity type, and a thickness on one side in the width direction with respect to the light absorption layer. Is provided in a portion thinner than the other portion so as to be continuous with the second conductivity type doping region, and is doped to the second conductivity type at a higher concentration than the second conductivity type doping region. A region, and an undoped region provided on the opposite side of the one side across the light absorption layer,
A first electrode on the first conductivity type doping region;
The light receiver according to claim 1, further comprising a second electrode on the high-concentration second conductivity type doping region.   The input waveguide core layer is connected to the constant width portion having a constant width and the constant width portion, and the width increases from the constant width portion side toward the guide waveguide core layer side. The optical receiver according to claim 1, further comprising a tapered portion. A first receiver;
A second receiver,
The first light receiver
A first input waveguide core layer;
A first guide waveguide core layer connected to the first input waveguide core layer;
A first light absorption layer provided on one side in the width direction with respect to the center position in the width direction of the first input waveguide core layer and above the first guide waveguide core layer;
A first electrode connected to one side in the thickness direction of the first light absorption layer;
A second electrode connected to the other side in the thickness direction of the first light absorption layer,
The second light receiver
A second input waveguide core layer;
A second guide waveguide core layer connected to the second input waveguide core layer;
A second light absorbing layer provided on one side in the width direction with respect to the center position in the width direction of the second input waveguide core layer and above the second guide waveguide core layer;
A third electrode connected to one side of the second light absorption layer in the thickness direction;
A fourth electrode connected to the other side in the thickness direction of the second light absorption layer,
Furthermore, a signal line to which the first electrode and the third electrode are connected;
A first ground line to which the second electrode is connected;
And a second ground line to which the fourth electrode is connected. Providing an input waveguide core layer and a guide waveguide core layer connected to the input waveguide core layer;
A step of providing a light absorption layer on one side in the width direction with respect to the center position in the width direction of the input waveguide core layer and above the guide waveguide core layer. Production method.