Semiconductor light-receiving element and optical device

Abstract

Provided is a semiconductor light-receiving element comprising a substrate including a first surface and a second surface on the reverse side from the first surface, a semiconductor mesa provided on the first surface, a lens provided on the second surface, and a first electrode and a second electrode provided on the first surface side and connected to the semiconductor mesa, the semiconductor mesa including a light-receiving part that receives light incident from the second surface side through the lens, and a light absorption layer at least a part of which is included in the light-receiving part and absorbs light, the first electrode being connected to a region of a first conductivity type in the semiconductor mesa, and the second electrode being connected to a region of a second conductivity type different from the first conductivity type in the semiconductor mesa.

Description

Semiconductor light receiving element and optical device

[0001] The present disclosure relates to a semiconductor light receiving element and an optical device.

[0002] Patent Document 1 describes a semiconductor light-receiving element. This semiconductor light-receiving element includes an n-type semiconductor substrate, a lens, a mesa-shaped light-receiving region, a p-type electrode, and an n-type electrode. The light-receiving region is formed on the surface of the n-type semiconductor substrate opposite the light-incident side and includes a light-absorbing layer. The lens is provided on the light-incident surface of the n-type semiconductor substrate. The lens is positioned directly above the mesa of the light-receiving region.

[0003] JP 2011-124450 A

[0004] In recent years, in the above technical fields, there has been a demand for even faster operating speeds, for example, exceeding 50 GHz. In this case, it is desirable to reduce the thickness of the light absorption layer in order to improve response. However, reducing the thickness of the light absorption layer can cause a problem of reduced sensitivity.

[0005] Therefore, an object of the present disclosure is to provide a semiconductor light-receiving element and an optical device that can improve sensitivity.

[0006] The semiconductor light-receiving element according to the present disclosure is [1] "a semiconductor light-receiving element comprising: a substrate including a first surface and a second surface opposite to the first surface; a semiconductor mesa provided on the first surface; a lens provided on the second surface; and a first electrode and a second electrode provided on the first surface side and connected to the semiconductor mesa, wherein the semiconductor mesa has a light-receiving portion that receives light incident from the second surface side through the lens; and a light-absorbing layer at least a portion of which is included in the light-receiving portion and absorbs the light, the first electrode being connected to a region of a first conductivity type in the semiconductor mesa, and the second electrode being connected to a region of a second conductivity type in the semiconductor mesa that is different from the first conductivity type, when viewed from a first direction intersecting the first surface of the substrate, the center of the light-receiving portion is offset from the center of the lens along a second direction intersecting the first direction, when viewed from the first direction."

[0007] In this semiconductor light-receiving element, a semiconductor mesa including a light-receiving portion and a light-absorbing layer is provided on a first surface of a substrate, and a lens is provided on a second surface opposite the first surface of the substrate. The light-receiving portion receives light incident through the lens from the second surface of the substrate. When viewed from a first direction intersecting the first surface of the substrate, the center of the light-receiving portion is offset from the center of the lens along a second direction intersecting the first direction. Therefore, light is incident on the light-receiving portion and the light-absorbing layer obliquely according to the offset amount of the lens (the distance between the centers), thereby ensuring an optical path length greater than the thickness of the light-absorbing layer. In particular, when viewed from the first direction, the offset amount of the lens is greater than the distance from the center of the light-receiving portion to the edge of the light-receiving portion. This allows a longer optical path length in the light-absorbing layer to be ensured, thereby improving sensitivity.

[0008] The semiconductor light-receiving element according to the present disclosure may be [2] "the semiconductor light-receiving element according to the above [1], including a protrusion protruding from the first surface, wherein the first electrode or the second electrode extends from a connection region with the semiconductor mesa to a top surface of the protrusion opposite the first surface." In this case, the semiconductor light-receiving element is disposed with the first surface side of the substrate facing an external device, and a region on the top surface of the protrusion of the first electrode or the second electrode is used as a connection terminal with the external device, thereby enabling connection to the external device while protecting the semiconductor mesa. Furthermore, when a connection member such as a solder bump is interposed between the connection terminal of the first electrode or the second electrode, the height of the connection member can be reduced by the height of the protrusion.

[0009] The semiconductor light-receiving element according to the present disclosure may be [3] "the semiconductor light-receiving element according to the above [2], wherein the protrusion includes a first protrusion and a second protrusion, the first electrode extends from a connection region with the semiconductor mesa to a first top surface opposite the first surface of the first protrusion, and the second electrode extends from a connection region with the semiconductor mesa to a second top surface opposite the first surface of the second protrusion." In this case, the semiconductor light-receiving element is disposed with the first surface side of the substrate facing an external device, and regions on the top surfaces of the first protrusion and second protrusion of the first electrode and second electrode are used as connection terminals with the external device, thereby enabling connection to the external device while protecting the semiconductor mesa. Furthermore, when connecting members such as solder bumps are interposed between the connection terminals of the first electrode and second electrode, the height of the connecting members can be reduced by the height of the first protrusion and second protrusion.

[0010] The semiconductor light-receiving element according to the present disclosure may be [4] "the semiconductor light-receiving element according to the above [2] or [3], wherein the protrusion is made of a semiconductor laminate." In this case, the protrusion can be provided by a semiconductor manufacturing process.

[0011] The semiconductor light-receiving element according to the present disclosure may be [5] "the semiconductor light-receiving element according to any one of [1] to [4] above, in which, when viewed from the first direction, the distance from the center of the lens to the center of the light-receiving portion along the second direction is greater than the distance from the center of the light-absorbing layer to an end of the light-absorbing layer along the second direction." In this case, by more reliably ensuring a long optical path length in the light-absorbing layer, it is possible to reliably improve sensitivity.

[0012] The semiconductor light receiving element according to the present disclosure may be [6] "the semiconductor light receiving element according to any one of [1] to [5] above, in which at least a portion of the light absorbing layer overlaps with the lens when viewed from the first direction." In this case, excessive offset of the lens with respect to the light receiving section can be avoided. As a result, although the angle of incidence of light with respect to the light absorbing layer is limited, the error in the spot position of the incident light due to the thickness of the substrate is reduced, making alignment easier.

[0013] The semiconductor light receiving element according to the present disclosure may be [7] "the semiconductor light receiving element according to any one of [1] to [6] above, in which the entire light absorbing layer overlaps the lens when viewed from the first direction." In this case, excessive offset of the lens with respect to the light receiving section can be reliably prevented. As a result, although the angle of incidence of light with respect to the light absorbing layer is limited, errors in the spot position of the incident light due to the thickness of the substrate can be reliably suppressed, making alignment easier.

[0014] The semiconductor light-receiving element according to the present disclosure may be [8] "the semiconductor light-receiving element according to any one of [1] to [7] above, wherein the first electrode and the second electrode each have a terminal region that serves as a connection terminal with an external device, and the terminal region does not overlap with the lens when viewed from the first direction." In this case, when the semiconductor light-receiving element is mounted on an external device from the first surface side, it is possible to avoid adverse effects on the lens of pressure applied from the second surface side to the terminal regions of the first electrode and the second electrode.

[0015] The semiconductor light receiving element according to the present disclosure may be [9] "the semiconductor light receiving element according to any one of [2] to [4] above, in which the protrusion does not overlap the lens when viewed from the first direction." In this case, when the semiconductor light receiving element is mounted on an external device from the first surface side, it is possible to avoid adverse effects on the lens caused by pressure applied to the protrusion from the second surface side.

[0016] The semiconductor light receiving element according to the present disclosure may be

[10] "the semiconductor light receiving element according to any one of [1] to [9] above, wherein the substrate has a recess recessed toward the first surface, and the second surface is the bottom surface of the recess." In this case, the lens is provided on the bottom surface of the recess. As a result, scratches on the lens surface and adhesion of foreign matter can be prevented.

[0017] The semiconductor light-receiving element according to the present disclosure may be

[11] "the semiconductor light-receiving element according to the above

[10] , wherein the inner surface of the recess is inclined with respect to the first direction so that the recess becomes larger as it moves away from the bottom surface." In this case, the wall portion of the recess (the portion having the inner surface) is less likely to interfere with light that is obliquely incident on the lens. This makes it possible to increase the effective area of ​​the lens.

[0018] The semiconductor light receiving element according to the present disclosure may be

[12] "the semiconductor light receiving element according to any one of the above [1] to

[11] , wherein, when viewed from the first direction, the distance between one end of the lens and the other end opposite to the one end is five times or more the distance between one end of the light receiving portion and the other end opposite to the one end." In this case, the effective area of ​​the lens can be increased.

[0019] The semiconductor light receiving element according to the present disclosure may be

[13] "the semiconductor light receiving element according to any one of [1] to

[12] above, wherein the thickness of the light absorption layer is 1.2 μm or less." In this case, high-speed readout is possible (speeding up is achieved).

[0020] The optical device according to the present disclosure is

[14] "an optical device comprising a semiconductor light receiving element according to any one of [1] to

[13] above, and an amplifier that receives an input of an electrical signal generated by the semiconductor light receiving element, wherein the semiconductor light receiving element is arranged so that the first surface faces a surface of the amplifier, and is electrically connected to the amplifier via connecting members provided on each of the first electrode and the second electrode."

[0021] This optical device includes the semiconductor light-receiving element described above. Therefore, sensitivity can be improved. Furthermore, in this optical device, the semiconductor light-receiving element is disposed so that the first surface of the substrate faces the surface of the amplifier, and is electrically connected to the amplifier via connecting members provided on the first and second electrodes. That is, the semiconductor light-receiving element is directly mounted on the amplifier via connecting members (e.g., solder bumps) between the first and second electrodes on the first surface. As a result, compared to, for example, mounting the semiconductor light-receiving element on a submount and connecting the submount to the amplifier with wires, the inductance of the submount and wires can be eliminated from the inductance between the semiconductor light-receiving element and the amplifier. Therefore, by adjusting the inductance of the wiring within the semiconductor light-receiving element, an optical device with reduced inductance variation can be realized.

[0022] According to the present disclosure, it is possible to provide a semiconductor light-receiving element and an optical device that can improve sensitivity.

[0023] Fig. 1 is a schematic side view showing an optical device according to one embodiment. Fig. 2 is a schematic plan view of the semiconductor light-receiving element shown in Fig. 1. Fig. 3 is a schematic cross-sectional view taken along line III-III in Fig. 2. Fig. 4 is a schematic cross-sectional view taken along line IV-IV in Fig. 2. Fig. 5 is a schematic cross-sectional view showing a semiconductor light-receiving element according to a modified example. Fig. 6 is a cross-sectional view showing a semiconductor light-receiving element according to another modified example.

[0024] Hereinafter, an embodiment of a semiconductor light receiving element and an optical device according to the present disclosure will be described in detail with reference to the drawings. In each drawing, identical or corresponding elements are designated by the same reference numerals, and redundant description may be omitted. Each drawing may also show an orthogonal coordinate system including a first axis defining a first direction D1, a second axis defining a second direction D2 intersecting the first direction D1, and a third axis defining a third direction D3 intersecting the first direction D1 and the second direction D2.

[0025] Fig. 1 is a schematic side view showing an optical device according to one embodiment. As shown in Fig. 1, the optical device 100 includes a semiconductor light receiving element 1. The optical device 100 can be configured to receive light L in wavelength bands used for optical communications, such as the 1.3 µm band (O-band (Original-band)), the 1.55 µm band (C-band (Conventional-band)), and the 1.6 µm band (L-band (Long-wavelength-band)), and can convert the light into an electrical signal for output.

[0026] The 1.3 μm band is, for example, a wavelength range of 1.26 μm or more and 1.36 μm or less. The 1.55 μm band is, for example, a wavelength range of 1.53 μm or more and 1.565 μm or less. The 1.6 μm band is, for example, a wavelength range of more than 1.565 μm and 1.625 μm or less. Furthermore, light L in a communication wavelength band is light having a peak within the wavelength range of any of the above wavelength bands (i.e., wavelengths other than the peak may be outside the wavelength range of the above wavelength bands).

[0027] Therefore, the semiconductor light receiving element 1 may also be one that targets the above wavelength bands, and may be one that receives incident light L having a wavelength belonging to at least one of the wavelength bands and generates an electrical signal in response to the incident light. The semiconductor light receiving element 1 is mounted on a transimpedance amplifier (TIA) A (amplifier, external device) via connecting members A3 and A4 such as solder bumps.

[0028] More specifically, the semiconductor light-receiving element 1 is arranged such that the first electrode 40 and the second electrode 50 formed on the surface opposite to the light incident surface of the semiconductor light-receiving element 1 face the electrode pads A1 and A2 of the transimpedance amplifier A. In this state, the semiconductor light-receiving element 1 is connected to the transimpedance amplifier A by connection members A3 and A4 interposed between the first electrode 40 and the second electrode 50 and the electrode pads A1 and A2, respectively. As described above, in this embodiment, the semiconductor light-receiving element 1 is mounted on the transimpedance amplifier A by flip-chip bonding.

[0029] As an example, the light L is guided by an optical fiber (not shown) and is focused by a lens RL formed on the substrate 10 (see FIGS. 3 and 4 , etc.) of the semiconductor light receiving element 1 toward the light receiving portion 30 formed in the semiconductor laminate 20 (see FIGS. 3 and 4 , etc.) of the semiconductor light receiving element 1. That is, in this embodiment, the semiconductor light receiving element 1 is configured as a back-illuminated element that receives the light L from the substrate 10 side toward the semiconductor laminate 20. More specifically, the semiconductor light receiving element 1 receives the light L from the back surface 10r side, which will be described later, and the light L is guided from the substrate 10 side to the semiconductor laminate 20.

[0030] As will be described later, in the semiconductor light receiving element 1, the lens RL is offset in the second direction D2 with respect to the light receiving portion 30. Therefore, the light L is incident obliquely on the lens RL and the light receiving portion 30. An electrical signal generated by the semiconductor light receiving element 1 in response to the incidence of the light L is input to the transimpedance amplifier A, converted into a voltage signal by the transimpedance amplifier A, and then output to the outside.

[0031] Fig. 2 is a schematic plan view of the semiconductor light-receiving element shown in Fig. 1. Fig. 3 is a schematic cross-sectional view taken along line III-III in Fig. 2. As shown in Figs. 2 and 3, the semiconductor light-receiving element 1 includes a substrate 10, a semiconductor laminate 20, a first electrode 40, and a second electrode 50.

[0032] The substrate 10 includes a semi-insulating semiconductor. Here, the substrate 10 is, for example, a semi-insulating semiconductor substrate made of InP. The substrate 10 includes a front surface (first surface) 10a and a back surface 10r opposite the front surface 10a. A first direction D1 is a direction intersecting (orthogonal to) the front surface 10a and the back surface 10r. The substrate 10 includes a plurality of regions RA, RB, and RC arranged in order along the front surface 10a and the back surface 10r when viewed from a second direction D2 intersecting (orthogonal to) the first direction D1. The region RB is a region between the region RA and the region RC. More specifically, the region RB includes a region RB1 on the central side and a region RB2 located on both sides of the region RB1 (on the region RA and RC side).

[0033] Here, a recess 10C is formed on the back surface 10r of the substrate 10. A lens RL for focusing light L toward the light receiving unit 30 is formed on the bottom surface (second surface opposite to the front surface 10a) 10b of the recess 10C. Therefore, the back surface 10r and the bottom surface 10b of the substrate 10 are incident surfaces for light L. The lens RL is formed so as to partially overlap with region RB2, with region RB1 as the center.

[0034] The semiconductor laminate 20 is formed on the substrate 10. More specifically, the semiconductor laminate 20 is formed on the surface 10a in the region RB of the substrate 10. The semiconductor laminate 20 includes a back surface 20b on the substrate 10 side and a front surface 20a on the opposite side from the substrate 10. The semiconductor laminate 20 includes a buffer layer 21, a buffer layer 22, a capacitance-reducing layer 23, a light-absorbing layer 24, a cap layer 25, and a contact layer 26, which are stacked in this order from the substrate 10 side. Here, the back surface 20b of the semiconductor laminate 20 is the surface of the buffer layer 21 opposite the light-absorbing layer 24 and is in contact with the surface 10a of the substrate 10. The front surface 20a of the semiconductor laminate 20 is the surface of the contact layer 26 opposite the light-absorbing layer 24.

[0035] The buffer layer 21 is of a first conductivity type (here, N type, as an example, +The buffer layer 21 is provided so as to overlap with the region RB2, with the region RB1 as the center. The layers of the semiconductor laminate 20 other than the buffer layer 21 (the buffer layer 22, the capacitance-reducing layer 23, the light-absorbing layer 24, the cap layer 25, and the contact layer 26) are provided on the region of the buffer layer 21 that overlaps with the region RB1. Therefore, the buffer layer 21 has a portion 21p that is exposed from the layers of the semiconductor laminate 20 other than the buffer layer 21 and from the protective film 60 described below, and the semiconductor laminate 20 forms a semiconductor mesa M including a compound semiconductor. In the semiconductor light-receiving element 1, a junction with the first electrode 40 is formed at the portion 21p of the buffer layer 21. That is, the first electrode 40 is connected to the first conductivity type region (portion 21p) of the semiconductor laminate 20 (semiconductor mesa M). The buffer layer 21 includes, for example, InP, and as an example, N + - Made of InP.

[0036] The buffer layer 22 is of a first conductivity type (here, N type, as an example, + The buffer layer 22 includes, for example, InP or InGaAsP, and as an example, N + -InP or N + The buffer layer 21 and the buffer layer 22 constitute a first semiconductor layer S1 (here, of the first conductivity type) located between the substrate 10 and the light absorption layer 24.

[0037] The carrier concentration of buffer layer 22 is higher than the carrier concentration of capacitance-reducing layer 23, which will be described later. For example, the carrier concentration of buffer layer 22 is 5×10 １６ cm －３ 5x10 or more １８ cm －３ The thickness of the buffer layer 22 is, for example, not less than 0.5 μm and not more than 2.5 μm.

[0038] The buffer layers 21 and 22 may function as strain relaxation layers by having a lattice constant between that of the substrate 10 and that of the light absorbing layer 24. That is, the semiconductor laminate 20 may include a plurality of strain relaxation layers (step layers) arranged such that the lattice constant gradually approaches that of the light absorbing layer 24 from the substrate 10 toward the light absorbing layer 24.

[0039] The capacitance-reducing layer 23 is of a first conductivity type (here, N type, as an example, - The capacitance-reducing layer 23 includes, for example, any one of InP, InGaAsP, InAsP, and AlInGaAs. - - InP, N - -InGaAsP,N - - InAsP and N - The capacitance-reducing layer 23 is located between the first semiconductor layer S1 and the light-absorbing layer 24. Here, the capacitance-reducing layer 23 is in contact with the first semiconductor layer S1 and the light-absorbing layer 24.

[0040] The light absorbing layer 24 is of a first conductivity type (here, N type, as an example, - Here, the light absorbing layer 24 has an N － -In ｘ Ga １－ｘ The light absorbing layer 24 may be made of Al, P, Sb, N, or other materials having a band gap of, for example, 0.72 eV or less (e.g., an absorption layer of a mixed crystal of InGaAs and the material). In this case, the light absorbing layer 24 may be made of, for example, InGaAsP, AlGaInAs, InGaAsSb, or InGaAsN. In this case, the light absorbing layer 24 may be made of, for example, InGaAsP, AlGaInAs, InGaAsSb, or InGaAsN. The proportion of Al, P, Sb, and N (or other materials) mixed into InGaAs can be, for example, 5% or less, or 10% or less.

[0041] Here, capacitance-reducing layer 23 has a carrier concentration higher than the carrier concentration of light-absorbing layer 24. For example, the carrier concentration of capacitance-reducing layer 23 is 1.5×10 １４ cm －３ 3x10 or more １６ cm－３ The impurity concentration of the light absorption layer 24 is 1×10 １４ cm －３ 6 x 10 or more １５ cm －３ Furthermore, capacitance-reducing layer 23 has a band gap larger than the band gap of light-absorbing layer 24. When light-absorbing layer 24 has a band gap of 0.72 eV or less as described above, capacitance-reducing layer 23 can have a band gap in the range of more than 0.72 eV and 1.35 eV or less.

[0042] As described above, capacitance-reducing layer 23 is required to have a higher carrier concentration than light-absorbing layer 24 and to be depleted when a bias is applied. The reason for this is that, as described above, capacitance-reducing layer 23 has a larger band gap than light-absorbing layer 24, and if the carrier concentration is low, a barrier is created in the conduction band, which may hinder the movement of carriers with a large barrier and prevent them from being suitably extracted.

[0043] Furthermore, since capacitance-reducing layer 23 needs to be depleted when a bias is applied, the upper limit of the carrier concentration is set to 6.0×10 as described above. １５ cm －３ Furthermore, capacitance-reducing layer 23 may have a composition that does not absorb incident light (i.e., a band gap wider than that of light-absorbing layer 24). This is because if capacitance-reducing layer 23 absorbs incident light, carriers are generated in capacitance-reducing layer 23. These carriers are extracted as signals from capacitance-reducing layer 23 via light-absorbing layer 24, and therefore become slow carriers, which may deteriorate the response characteristics. As an example, the sensitivity wavelength range of capacitance-reducing layer 23 may be 1.31 μm or less.

[0044] In this way, by setting the relationship between capacitance-reducing layer 23 and light-absorbing layer 24 as described above, it is possible to reduce capacitance without reducing carrier response. The thickness of capacitance-reducing layer 23 can be set to be, for example, 0.1 μm or more and 3.0 μm or less.

[0045] In the semiconductor light-receiving element 1, the light-absorbing layer 24 is a single layer. The light-absorbing layer 24 being a single layer means that the light-absorbing layer 24 does not have a layered structure formed by stacking two or more layers with different compositions or properties. More specifically, the light-absorbing layer 24 being a single layer means that it does not have a superlattice structure formed by repeatedly stacking multiple layers with different compositions, for example.

[0046] The cap layer 25 is of a first conductivity type (here, N type, as an example, - The cap layer 25 may include, for example, InP or InGaAsP. － -InP or N - The cap layer 25 is made of InGaAsP. The carrier concentration of the cap layer 25 is, for example, 1×10 １４ cm －３ 1x10 or more １６ cm －３ The thickness of the cap layer 25 is, for example, not less than 0.1 μm and not more than 0.5 μm.

[0047] The contact layer 26 is of a first conductivity type (here, N type, as an example, － The contact layer 26 includes, for example, InGaAs. － The carrier concentration of the contact layer 26 is, for example, 1×10 １４ cm －３ 1x10 or more １６ cm －３ The thickness of the contact layer 26 is, for example, not less than 0.1 μm and not more than 0.2 μm.

[0048] In the semiconductor laminate portion 20, a second conductivity type (here, P type, as an example, +A second region 27 (here, of a second conductivity type) is formed on the semiconductor layer 20. The second region 27 can be formed by, for example, thermal diffusion, ion implantation, or the like. The second region 27 extends from the surface 20a of the semiconductor laminate 20 toward the substrate 10. Here, the second region 27 is formed so as to extend from the contact layer 26 through the cap layer 25 to the light absorbing layer 24. In this manner, the cap layer 25 and the contact layer 26 constitute a second semiconductor layer S2 located on the opposite side of the substrate 10 from the light absorbing layer 24. The second semiconductor layer S2 includes a second region 27 (here, of a second conductivity type) that forms a PN junction with the light absorbing layer 24. The second region 27, together with the light absorbing layer 24, constitutes a light receiving portion 30 included in the semiconductor mesa M. The light receiving portion 30 is a portion of the semiconductor mesa M that overlaps with the second region 27 when viewed from the first direction D1.

[0049] Here, the second region 27 (i.e., the light receiving portion 30) is formed in a portion (e.g., a portion including the center) in the width direction (direction intersecting the first direction D1) of the semiconductor mesa M. Therefore, here, the semiconductor mesa M includes a third region 28 of the first conductivity type that surrounds the second region 27 when viewed from the first direction D1. In addition, a portion of the light absorption layer 24 on the central side is included in the light receiving portion 30.

[0050] The second region 27 may extend into the light absorbing layer 24. In this case, the light absorbing layer 24 includes a fifth region 27a of the second conductivity type, which is an extension of the second region 27, and a first region 24a of the first conductivity type other than the fifth region 27a. In this case, if the thickness of the light absorbing layer 24 is, for example, 0.7 μm, the fifth region 27a can be formed in a range of 0.2 μm on the cap layer 25 side of the light absorbing layer 24. That is, in this example, the first region 24a with a thickness of about 0.5 μm and the fifth region 27a with a thickness of 0.2 μm are included inside the light absorbing layer 24, and a boundary between them is formed. If the fifth region 27a is P ＋ When the terminal is a P-type, for example, the P-type carrier concentration is 1×10 １７ cm －３ The position is as follows:

[0051] On the other hand, when the second region 27 does not reach the inside of the light absorbing layer 24, the entire light absorbing layer 24 becomes the first region 24a of the first conductivity type. + The type is an N-type carrier concentration of 1×10 １７ cm －３ This means that the number is equal to or greater than the number of － The N-type carrier concentration is 3.0 × 10 １６ cm －３ This means that the P + The P-type carrier concentration is 1×10 １７ cm －３ This means that it is more than or equal to this.

[0052] Here, the semiconductor light receiving element 1 includes a protective film 60. The protective film 60 is, for example, an insulating film. A portion of the surface 20a (top surface) of the semiconductor laminate 20 and a side surface 20s of the semiconductor laminate 20 extending from the periphery of the surface 20a toward the substrate 10 are covered by the protective film 60. Meanwhile, the remaining portion of the surface 20a of the semiconductor laminate 20, in this case the surface of the second region 27, is exposed from the protective film 60. A second electrode 50 is formed on the portion of the surface 20a exposed from the protective film 60, and a junction is formed between the second electrode 50 and the second region 27 (contact layer 26). That is, the second electrode 50 is connected to a second conductivity type portion (second region 27) of the semiconductor laminate 20 located on the opposite side of the light absorption layer 24 from the substrate 10.

[0053] In other words, the second electrode 50 is connected to a second conductivity type region (second region 27) in the semiconductor mesa M. On the other hand, the first electrode 40 is connected to a first conductivity type portion 21p (a portion of the buffer layer 21 exposed from the protective film 60) of the semiconductor laminate portion 20 that is located on the substrate 10 side with respect to the light absorption layer 24.

[0054] Fig. 4 is a schematic cross-sectional view taken along line IV-IV in Fig. 2. The Cartesian coordinate system shown in Fig. 4 corresponds to a cross-section including the second direction D2 and the first direction D1 in the cross-section taken along line IV-IV in Fig. 2. In Fig. 4, the lens and recesses are not shown, and a portion of the first electrode 40 is not shown in the cross-section taken along a portion of line IV-IV in Fig. 2 that is inclined with respect to the second direction D2.

[0055] 2 and 4, the semiconductor light receiving element 1 has a protrusion. More specifically, the semiconductor light receiving element 1 has a first protrusion C1 and a second protrusion C2 as protrusions. The first protrusion C1 and the second protrusion C2 are provided protruding from the surface 10a of the substrate 10. In this embodiment, the first protrusion C1 and the second protrusion C2 (i.e., the protrusions) are made of a semiconductor laminate. More specifically, the first protrusion C1 and the second protrusion C2 are made of the same semiconductor layer as the semiconductor laminate 20. In other words, the first protrusion C1 and the second protrusion C2 are semiconductor mesas including compound semiconductors. The first protrusion C1 and the second protrusion C2 are covered with a protective film 60.

[0056] The first electrode 40 extends from a connection region (portion 21p) with the semiconductor laminate 20 (i.e., semiconductor mesa M) to a first top surface C1s on the opposite side of the surface 10a of the first protrusion C1. The portion of the first electrode 40 located on the first top surface C1s is a terminal region (electrode pad) 40p that serves as a connection terminal with the transimpedance amplifier A. Therefore, when the semiconductor light receiving element 1 is mounted on the transimpedance amplifier A, the terminal region 40p is connected to the electrode pad A1 of the transimpedance amplifier A via the connection member A3.

[0057] The second electrode 50 extends from a connection region (second region 27) with the semiconductor laminate 20 (i.e., the semiconductor mesa M) to a second top surface C2s on the opposite side of the surface 10a of the second protrusion C2. The portion of the second electrode 50 located on the second top surface C2s is a terminal region (electrode pad) 50p that serves as a connection terminal with the transimpedance amplifier A. Therefore, when the semiconductor light receiving element 1 is mounted on the transimpedance amplifier A, the terminal region 50p is connected to the electrode pad A2 of the transimpedance amplifier A via the connection member A4.

[0058] Thus, in the optical device 100, the semiconductor light-receiving element 1 is disposed so that the surface 10a faces the surface of the transimpedance amplifier A, and is electrically connected to the transimpedance amplifier A via the connection members A3 and A4 provided on the first electrode 40 and the second electrode 50, respectively. As described above, in the semiconductor light-receiving element 1, the first electrode 40 or the second electrode 50 extends from the connection region with the semiconductor mesa M to the top surface of the protrusion on the side opposite the surface 10a.

[0059] 2, the semiconductor light receiving element 1 includes a pair of first protrusions C1 arranged along the third direction D3 to sandwich the second protrusion C2, and only one of the first protrusions C1 is shown in FIG. 4. The first electrode 40 extends from one of the first protrusions C1 to the other first protrusion C1 via a connection region (portion 21p) with the semiconductor mesa M. A terminal region 40p is formed on each of the first top surfaces C1s of the pair of first protrusions C1.

[0060] The semiconductor light-receiving element 1 also includes a pair of third protrusions C3 arranged along the third direction D3. The third protrusions C3 protrude from the surface 10a of the substrate 10. The third protrusions C3 may be, for example, a semiconductor stack including semiconductor layers similar to those of the semiconductor stack 20. In this case, the third protrusions C3 are semiconductor mesas including compound semiconductors. An electrode Md is formed on the top surface of the pair of third protrusions C3 opposite the surface 10a of the substrate 10. The electrode Md is not electrically connected to other semiconductor layers and electrodes, such as the semiconductor mesa M, the first electrode 40, and the second electrode 50, and is therefore a dummy (dummy electrode, dummy pad). The semiconductor light-receiving element 1 is formed in a rectangular shape when viewed from the first direction D1, and the pair of first protrusions C1 and the pair of third protrusions C3 are located at the four corners of the semiconductor light-receiving element 1. In this way, by providing the semiconductor light receiving element 1 with the dummy third protrusion C3, the number of connection regions with the transimpedance amplifier A becomes four or more, and stability is achieved during flip-chip bonding.

[0061] As shown in FIG. 4 , in the semiconductor light-receiving element 1, the center of the light-receiving portion 30 of the semiconductor mesa M is offset from the center of the lens RL in the second direction D2 when viewed from the first direction D1 (it is aligned with the center in the third direction D3). When viewed from the first direction D1, the distance OA from the center of the lens RL to the center of the light-receiving portion 30 along the second direction D2 is greater than the distance O1 from the center of the light-receiving portion 30 to the edge of the light-receiving portion 30 along the second direction D2. This allows light L to be incident on the light-receiving portion 30 from the rear surface 10r side through the lens RL at an angle oblique to the first direction D1. The light-absorbing layer 24 also absorbs light L incident obliquely with respect to the thickness direction (first direction D1) of the light-absorbing layer 24.

[0062] The second electrode 50 extends from the connection region (second region 27) with the semiconductor mesa M in the direction opposite to the offset direction of the light receiving unit 30 relative to the lens RL (here, the negative direction of the second direction D2) (i.e., the positive direction of the second direction D2), and reaches the second top surface C2s of the second protrusion C2 to form a terminal region 50p. Therefore, the length of the second electrode 50 in the second direction D2 is extended by at least the offset amount (distance OA) of the light receiving unit 30 relative to the lens RL.

[0063] In this embodiment, the light absorbing layer 24 is larger than the light receiving portion 30 in the second direction D2, but the distance OA is even larger than the distance O2 from the center of the light absorbing layer 24 to the end. Meanwhile, in this embodiment, a portion of the light absorbing layer 24 (and further the light receiving portion 30) overlaps with the lens RL when viewed from the first direction D1. Also, in this embodiment, when viewed from the first direction D1, the terminal region 40p of the first electrode 40 and the terminal region 50p of the second electrode 50 do not overlap with the lens RL, and furthermore, the first protrusion C1 and the second protrusion C2 do not overlap with the lens RL.

[0064] The centers of the light receiving unit 30, the light absorbing layer 24, and the lens RL may be their respective centers of gravity. When viewed from the first direction D1, for example, in the second direction D2, the distance TL between one end of the lens RL and the other end opposite to the one end may be five times or more the distance T1 between one end of the light receiving unit 30 and the other end opposite to the one end.

[0065] As described above, a recess 10C is formed on the rear surface 10r of the substrate 10 so as to be recessed toward the front surface 10a, and the lens RL is formed on the bottom surface 10b of the recess 10C. The inner surface 10Cs of the recess 10C is inclined with respect to the first direction D1 so that the recess 10C expands as it moves away from the bottom surface 10b. The entire lens RL is located within the recess 10C (it does not protrude from the rear surface 10r).

[0066] As described above, in the semiconductor light-receiving element 1 according to this embodiment, a semiconductor mesa M including a light-receiving portion 30 and a light-absorbing layer 24 is provided on the surface 10a of the substrate 10, and a lens RL is provided on the back surface 10r of the substrate 10. The light-receiving portion 30 receives light L incident on the back surface 10r of the substrate 10 through the lens RL. When viewed from the first direction D1, the center of the light-receiving portion 30 is offset from the center of the lens RL along the second direction D2. Therefore, the light L is incident on the light-absorbing layer 24 obliquely according to the offset amount of the lens RL (center-to-center distance OA), thereby ensuring an optical path length greater than the thickness of the light-absorbing layer 24. In particular, when viewed from the first direction D1, the offset amount of the lens RL is greater than the distance O1 from the center of the light-receiving portion 30 to the edge of the light-receiving portion 30. This allows a longer optical path length in the light-absorbing layer 24, thereby improving sensitivity.

[0067] The semiconductor light-receiving element 1 according to this embodiment also includes a first protrusion C1 and a second protrusion C2 (i.e., protrusions) protruding from the surface 10a of the substrate 10. The first electrode 40 extends from a connection region (portion 21p) with the semiconductor mesa M to reach a first top surface C1s of the first protrusion C1, and the second electrode 50 extends from a connection region (second region 27) with the semiconductor mesa M to reach a second top surface C2s of the second protrusion C2. Therefore, by placing the semiconductor light-receiving element 1 with the surface 10a of the substrate 10 facing a transimpedance amplifier A (external device) and using the regions on the top surfaces of the first protrusion C1 and second protrusion C2 of the first electrode 40 and second electrode 50 as connection terminals with the transimpedance amplifier A, connection to the transimpedance amplifier A can be made while protecting the semiconductor mesa M. Furthermore, when connecting members A3, A4 such as solder bumps are interposed between the connection terminals of the first electrode 40 and the second electrode 50, the height of the connecting members A3, A4 can be reduced by the height of the first protrusion C1 and the second protrusion C2.

[0068] In the semiconductor light receiving element 1 according to this embodiment, the first protrusion C1 and the second protrusion C2 (i.e., the protrusions) are made of a semiconductor laminate, and therefore the first protrusion C1 and the second protrusion C2 can be provided by the semiconductor manufacturing process.

[0069] Furthermore, in the semiconductor light receiving element 1 according to this embodiment, when viewed from the first direction D1, the distance OA from the center of the lens RL to the center of the light receiving portion 30 along the second direction D2 is greater than the distance O2 from the center of the light absorbing layer 24 to the end of the light absorbing layer 24 along the second direction D2. Therefore, by more reliably ensuring a long optical path length in the light absorbing layer 24, it is possible to reliably improve sensitivity.

[0070] Furthermore, in the semiconductor light receiving element 1 according to this embodiment, a portion of the light absorbing layer 24 overlaps with the lens RL when viewed from the first direction D1. This prevents the lens RL from being excessively offset with respect to the light receiving section 30. As a result, although the angle of incidence of the light L with respect to the light absorbing layer 24 is limited, the error in the spot position of the incident light due to the thickness of the substrate 10 is reduced, making alignment easier.

[0071] In the semiconductor light receiving element 1 according to this embodiment, the first electrode 40 and the second electrode 50 each have terminal regions 40p, 50p that serve as connection terminals with the transimpedance amplifier A. When viewed from the first direction D1, the terminal regions 40p, 50p do not overlap with the lens RL. Therefore, when the semiconductor light receiving element 1 is mounted on the transimpedance amplifier A from the front surface 10a side, it is possible to avoid adverse effects on the lens RL of pressure applied from the back surface 10r side to the terminal regions 40p, 50p of the first electrode 40 and the second electrode 50.

[0072] Furthermore, in the semiconductor light receiving element 1 according to this embodiment, the first protrusion C1 and the second protrusion C2 (i.e., the protrusions) do not overlap with the lens RL when viewed from the first direction D1. Therefore, when the semiconductor light receiving element 1 is mounted on the transimpedance amplifier A from the front surface 10a side, it is possible to avoid adverse effects on the lens RL of pressure applied to the first protrusion C1 and the second protrusion C2 from the back surface 10r side.

[0073] Furthermore, in the semiconductor light receiving element 1 according to this embodiment, a recess 10C recessed toward the front surface 10a is formed in the substrate 10, and the lens RL is provided on the bottom surface 10b of the recess 10C in the rear surface 10r of the substrate 10. This makes it possible to prevent scratches on the surface of the lens RL and the adhesion of foreign matter thereto.

[0074] Furthermore, in the semiconductor light receiving element 1 according to this embodiment, the inner surface 10Cs of the recess 10C is inclined with respect to the first direction D1 so that the recess 10C expands as it moves away from the bottom surface 10b. This makes it less likely that the wall portion of the recess 10C (the portion having the inner surface 10Cs) will obstruct the light L that is obliquely incident on the lens RL. This allows the effective area of ​​the lens RL to be increased.

[0075] Furthermore, in the semiconductor light receiving element 1 according to this embodiment, when viewed from the first direction D1, the distance TL between one end of the lens RL and the other end opposite to the one end may be five times or more the distance T1 between one end of the light receiving portion 30 and the other end opposite to the one end. In this case, the effective area of ​​the lens RL can be increased.

[0076] In the semiconductor light receiving element 1 according to this embodiment, the thickness of the light absorption layer 24 may be 1.2 μm or less, which enables high-speed readout (high speed is achieved).

[0077] Furthermore, the optical device 100 according to this embodiment includes a semiconductor light-receiving element 1 and a transimpedance amplifier A that receives an input of an electrical signal generated by the semiconductor light-receiving element 1. The semiconductor light-receiving element 1 is disposed so that the surface 10a of the substrate 10 faces the surface of the transimpedance amplifier A, and is electrically connected to the transimpedance amplifier A via connection members A3 and A4 provided on the first electrode 40 and the second electrode 50, respectively.

[0078] The optical device 100 includes the semiconductor light-receiving element 1 described above. Therefore, sensitivity can be improved. In addition, in the optical device 100, the semiconductor light-receiving element 1 is disposed such that the surface 10a of the substrate 10 faces the surface of the transimpedance amplifier A, and is electrically connected to the transimpedance amplifier A via connecting members A3 and A4 provided on the first electrode 40 and the second electrode 50, respectively. That is, the semiconductor light-receiving element 1 is directly connected to the transimpedance amplifier A via the first electrode 40 and the second electrode 50 on the surface 10a and the connecting members A3 and A4 (e.g., solder bumps). As a result, compared to, for example, mounting the semiconductor light-receiving element 1 on a submount and connecting the submount to the transimpedance amplifier A with wires, the inductance of the submount and wires can be excluded from the inductance between the semiconductor light-receiving element 1 and the transimpedance amplifier A. Therefore, by adjusting the inductance of the wiring within the semiconductor light-receiving element 1, it is possible to realize an optical device 100 with reduced inductance variation.

[0079] The above embodiment describes one aspect of the semiconductor light receiving element and optical device according to the present disclosure. Therefore, the semiconductor light receiving element and optical device according to the present disclosure are not limited to the above embodiment and may be modified as desired. Next, modified examples will be described.

[0080] FIG. 5 is a schematic cross-sectional view showing a semiconductor light-receiving element according to a modified example. The cross-section of FIG. 5 corresponds to the cross-section taken along line III-III in FIG. 2. In the example shown in FIG. 5, the entire second semiconductor layer S2 (i.e., the cap layer 25 and the contact layer 26) is made into a second region 27 of the second conductivity type (P type in this case, P+ type as an example). That is, the second semiconductor layer S2 is made of the second region 27. Such a second semiconductor layer S2 can be formed, for example, by epitaxially growing a semiconductor layer of the second conductivity type on the light absorption layer 24.

[0081] In this case, the second region 27 of the second conductivity type does not extend into the light absorbing layer 24. However, in this case, the second region 27 may include another light absorbing layer 27b of the second conductivity type (P type in this case, P+ type as an example) stacked on the light absorbing layer 24. The light absorbing layer 27b is located on the opposite side of the light absorbing layer 24 from the capacitance-reducing layer 23. In this case, the entire light absorbing layer 24 becomes the first region 24a of the first conductivity type. The light absorbing layer 27b may be made of the same material as the above-mentioned material of the light absorbing layer 24, including, for example, InGaAs, and is made of P+-InGaAs as an example.

[0082] The thickness of the light absorbing layer 27b may be thicker or thinner than the thickness of the light absorbing layer 24. When the thickness of the light absorbing layer 27b is thinner than the thickness of the light absorbing layer 24, the response speed is improved. In the example shown in Fig. 5, contact with the second electrode 50 is made at the contact layer 26, but by providing a light absorbing layer 27b of the second conductivity type, it is also possible to make contact with the second electrode 50 at this light absorbing layer 27b.

[0083] As described above, in the example shown in FIG. 5 , the second region 27 is formed over the entire semiconductor mesa M in the direction intersecting the first direction D1. In other words, the entire light absorption layer 24 is included in the light receiving unit 30. Therefore, in the example shown in FIG. 5 , the width of the light receiving unit 30 in the direction intersecting the first direction D1 is the same as the width of the light absorption layer 24. In the example shown in FIG. 5 , the light receiving unit 30 and the lens RL are offset along the second direction D2. However, in this case, the distance O1 from the center of the light receiving unit 30 to the end of the light receiving unit 30 along the second direction D2 is the same as the distance O2 from the center of the light absorption layer 24 to the end of the light receiving unit 30 along the second direction D2. Therefore, in this case, when viewed from the first direction D1, the overlap of a portion of the light receiving unit 30 with the lens RL is synonymous with the overlap of a portion of the light absorption layer 24 with the lens RL.

[0084] 6 is a cross-sectional view showing a semiconductor light-receiving element according to another modification. The cross section of FIG. 6 corresponds to the cross section taken along line III-III in FIG. 2. In the example shown in FIG. 6, the buffer layer 21 and the buffer layer 22 are of the second conductivity type (here, P type, for example, P +The buffer layer 21 includes, for example, InP. + The buffer layer 22 may be made of, for example, InP or InGaAsP. + -InP or P + - Made of InGaAsP.

[0085] In the example shown in FIG. 6, the cap layer 25 and the contact layer 26 are of the first conductivity type (here, N type, for example, N + The cap layer 25 includes, for example, InP or InGaAsP. + -InP or N + The contact layer 26 includes, for example, InGaAs. + The capacitance-reducing layer 23 and the light-absorbing layer 24 are made of InGaAs. The conductivity types of the capacitance-reducing layer 23 and the light-absorbing layer 24 are the same as those in the above embodiment.

[0086] 6, the first semiconductor layer S1 has the second conductivity type, and the second semiconductor layer S2 has the first conductivity type. The capacitance-reducing layer 23 is located between the light absorbing layer 24 and the second semiconductor layer S2. Therefore, in this example, the first semiconductor layer S1 includes a second region 27 of the second conductivity type that forms a PN junction with the light absorbing layer 24.

[0087] In this way, the capacitance-reducing layer 23 is located between one of the first semiconductor layer S1 and the second semiconductor layer S2 (the first semiconductor layer S1 in the above embodiment and the example of FIG. 5 , and the second semiconductor layer S2 in the example of FIG. 6 ) and the light absorbing layer 24. The other of the first semiconductor layer S1 and the second semiconductor layer S2 (the second semiconductor layer S2 in the above embodiment and the example of FIG. 5 , and the first semiconductor layer S1 in the example of FIG. 6 ) includes a second region 27 of the second conductivity type that forms a PN junction with the light absorbing layer 24 (first region 24 a).

[0088] 6 , the buffer layer 22 includes a first layer 22a provided across region RB1 and region RB2 of the substrate 10, and a second layer 22b formed on region RB1 but not reaching region RB2. The first layer 22a and the second layer 22b are stacked in this order from the substrate 10 side. The first layer 22a includes a portion 22p exposed from the semiconductor mesa M (i.e., the second layer 22b) and the protective film 60, and is connected to the first electrode 40 at this portion 22p.

[0089] As described above, in the example shown in FIG. 6 , the second region 27 is formed over the entire semiconductor mesa M in the direction intersecting the first direction D1. In other words, the entire light absorption layer 24 is included in the light receiving unit 30. Therefore, in the example shown in FIG. 6 , similar to the example shown in FIG. 5 , the width of the light receiving unit 30 in the direction intersecting the first direction D1 is the same as the width of the light absorption layers 24, 27b. In the example shown in FIG. 6 , the light receiving unit 30 and the lens RL are offset along the second direction D2. However, in this case, the distance O1 from the center of the light receiving unit 30 to the end of the light receiving unit 30 along the second direction D2 is the same as the distance O2 from the center of the light absorption layer 24 to the end of the light receiving unit 30 along the second direction D2. Therefore, in this case, when viewed from the first direction D1, the overlap of a portion of the light receiving unit 30 with the lens RL is synonymous with the overlap of a portion of the light absorption layer 24 with the lens RL.

[0090] Next, other modified examples will be described. In the semiconductor light receiving element 1 according to the above embodiment, a case has been illustrated in which a portion of the light absorbing layer 24 overlaps with the lens RL when viewed from the first direction D1. However, in the semiconductor light receiving element 1, the entire light absorbing layer 24 may overlap with the lens RL when viewed from the first direction D1. In this case, excessive offset of the lens RL with respect to the light receiving unit 30 can be reliably prevented. As a result, although the angle of incidence of the light L with respect to the light absorbing layer 24 is limited, errors in the spot position of the incident light due to the thickness of the substrate 10 are reliably suppressed, making alignment easier.

[0091] Furthermore, in the semiconductor light receiving element 1 according to the above embodiment, the centers of the light receiving portion 30 and the light absorbing layer 24 are offset from the center of the lens RL in the second direction D2 and coincide with each other in the third direction D3. However, the centers of the light receiving portion 30 and the light absorbing layer 24 may be offset from the center of the lens RL in both the second direction D2 and the third direction D3. In this case, when viewed from the first direction D1, the distance OA from the center of the lens RL to the center of the light receiving portion 30 may be set to be greater than the shortest distance from the center of the light receiving portion 30 to an end of the light receiving portion 30 in any direction, or may be set to be greater than at least one of the distance O1 from the center of the light receiving portion 30 to the end of the light receiving portion 30 in the second direction D2 and the distance O1 from the center of the light receiving portion 30 to the end of the light receiving portion 30 in the third direction D3. The same applies to the positional relationship with the light absorbing layer 24.

[0092] That is, in this case, when viewed from the first direction D1, the distance OA may be set to be larger than the shortest distance from the center of the light absorbing layer 24 to the end of the light absorbing layer 24 in any direction, or may be set to be larger than at least one of the distance O2 from the center of the light absorbing layer 24 to the end of the light absorbing layer 24 in the second direction D2 and the distance from the center of the light absorbing layer 24 to the end of the light absorbing layer 24 in the third direction D3.

[0093] Furthermore, in the above embodiment, the first protrusion C1 and the second protrusion C2 (and further the third protrusion C3 (the same applies below)) are made of a semiconductor laminate. However, the first protrusion C1 and the second protrusion C2 may have other structures. For example, the first protrusion C1 and the second protrusion C2 may be made of a metal or an insulator. When the first protrusion C1 and the second protrusion C2 are made of a metal, the first protrusion C1 and the second protrusion C2 can be formed by partially thickening the first electrode 40 and the second electrode 50, respectively. Alternatively, when the first protrusion C1 and the second protrusion C2 are made of an insulator, the first protrusion C1 and the second protrusion C2 can be formed by partially thickening an insulating film such as the protective film 60.

[0094] Furthermore, when the first protrusion C1 and the second protrusion C2 are formed from a semiconductor laminate, the first protrusion C1 and the second protrusion C2 may be formed by leaving portions of the semiconductor layer corresponding to the first protrusion C1 and the second protrusion C2 unetched when etching the semiconductor layer to form the semiconductor mesa M. Alternatively, the first protrusion C1 and the second protrusion C2 may be formed by separately laminating a semiconductor layer on the surface 10a of the substrate 10 after etching to form the semiconductor mesa M.

[0095] Furthermore, the semiconductor mesa M, the first protrusion C1, and the second protrusion C2 are not limited to being formed completely independently by forming a groove between them that reaches the surface 10a of the substrate 10. For example, the semiconductor mesa M, the first protrusion C1, and the second protrusion C2 may be configured to be embedded while being insulated from each other.

[0096] Alternatively, the first protruding portion C1 and the second protruding portion C2 may be formed as one mesa, or the first protruding portion C1 and the second protruding portion C2 may be configured as separate mesas, with a portion of the semiconductor layer closer to the substrate 10 being shared between them. Furthermore, the semiconductor mesa M (i.e., the semiconductor stack 20) ​​and the first protruding portion C1 and / or the second protruding portion C2 may be formed as one mesa, or the semiconductor mesa M and the first protruding portion C1 and / or the second protruding portion C2 may be configured as separate mesas, with a portion of the semiconductor layer closer to the substrate 10 being shared between them.

[0097] On the other hand, if an electrode connected to the P-type and an N-type semiconductor layer constituting the semiconductor mesa M (semiconductor laminate portion 20) are close to each other (for example, if only the protective film 60 is interposed), there is a risk that capacitance will be generated between them, slowing down the response speed (the same is thought to occur between an N-type electrode and a P-type semiconductor layer, but the N-type electrode is connected to GND, so the impact is small). Therefore, by separating the semiconductor mesa M from the protrusions (first protrusion C1 and second protrusion C2), the area where electrodes and semiconductor layers of different conductivity types are close to each other via only the protective film 60 is reduced, resulting in an effect of faster response speed.

[0098] In the above embodiment, the light absorption layer 24 and the semiconductor mesa M including the light absorption layer 24 include a compound semiconductor. However, the light absorption layer 24 may be made of a semiconductor that is not a compound, such as silicon or germanium. The semiconductor mesa M may also be made of a semiconductor that is not a compound, such as silicon or germanium. The semiconductor light receiving element 1 may not include the first protrusion C1 and the second protrusion C2, and the substrate 10 may not have a recess 10C formed therein.

[0099] 1...semiconductor light receiving element, 10...substrate, 10a...surface (first surface), 10b...bottom surface (second surface), 10C...recess, 10Cs...inner surface, 24...light absorption layer, 30...light receiving portion, 40...first electrode, 40p, 50p...terminal region, 50...second electrode, C1...first protrusion, C2...second protrusion, L...light, M...semiconductor mesa, RL...lens, O1, O2, OA...distance.

Claims

1. A semiconductor light-receiving element comprising: a substrate including a first surface and a second surface opposite to the first surface; a semiconductor mesa provided on the first surface; a lens provided on the second surface; and a first electrode and a second electrode provided on the first surface side and connected to the semiconductor mesa, wherein the semiconductor mesa has: a light-receiving portion that receives light from the second surface side through the lens; and a light-absorbing layer, at least a portion of which is included in the light-receiving portion and absorbs the light, wherein the first electrode is connected to a region of a first conductivity type in the semiconductor mesa, and the second electrode is connected to a region of a second conductivity type in the semiconductor mesa that is different from the first conductivity type, when viewed from a first direction intersecting the first surface of the substrate, a center of the light-receiving portion is offset from the center of the lens along a second direction intersecting the first direction, and when viewed from the first direction, a distance from the center of the lens to the center of the light-receiving portion along the second direction is greater than a distance from the center of the light-receiving portion to an end of the light-receiving portion along the second direction.

2. A semiconductor light receiving element as described in claim 1, further comprising a protrusion protruding from said first surface, said first electrode or said second electrode extending from a connection region with said semiconductor mesa to a top surface of said protrusion opposite said first surface.

3. The semiconductor light receiving element according to claim 2, wherein the protrusion includes a first protrusion and a second protrusion, the first electrode extends from a connection region with the semiconductor mesa to reach a first top surface of the first protrusion opposite the first surface, and the second electrode extends from a connection region with the semiconductor mesa to reach a second top surface of the second protrusion opposite the first surface.

4. The semiconductor light receiving element according to claim 2 or 3, wherein the protrusion is made of a semiconductor laminate.

5. A semiconductor light-receiving element described in any one of claims 1 to 4, wherein, when viewed from the first direction, the distance from the center of the lens to the center of the light-receiving portion along the second direction is greater than the distance from the center of the light-absorbing layer to an end of the light-absorbing layer along the second direction.

6. The semiconductor light receiving element according to any one of claims 1 to 5, wherein at least a portion of the light absorbing layer overlaps with a lens when viewed from the first direction.

7. The semiconductor light receiving element according to any one of claims 1 to 6, wherein the entire light absorbing layer overlaps with the lens when viewed from the first direction.

8. A semiconductor light receiving element according to any one of claims 1 to 7, wherein the first electrode and the second electrode each have a terminal area that serves as a connection terminal with an external device, and when viewed from the first direction, the terminal area does not overlap with the lens.

9. The semiconductor light receiving element according to any one of claims 2 to 4, wherein the protrusion does not overlap the lens when viewed from the first direction.

10. A semiconductor light receiving element according to any one of claims 1 to 9, wherein the substrate is formed with a recess recessed toward the first surface, and the second surface is a bottom surface of the recess.

11. The semiconductor light receiving element according to claim 10, wherein an inner side surface of the recess is inclined with respect to the first direction so that the recess becomes larger as it moves away from the bottom surface.

12. A semiconductor light-receiving element according to any one of claims 1 to 11, wherein when viewed from the first direction, the distance between one end of the lens and the other end opposite the one end is at least five times the distance between one end of the light-receiving portion and the other end opposite the one end.

13. The semiconductor light receiving element according to any one of claims 1 to 12, wherein the light absorbing layer has a thickness of 1.2 µm or less.

14. An optical device comprising: a semiconductor light receiving element according to any one of claims 1 to 13; and an amplifier that receives an input of an electrical signal generated by the semiconductor light receiving element, wherein the semiconductor light receiving element is arranged so that the first surface faces a surface of the amplifier and is electrically connected to the amplifier via connecting members provided on each of the first electrode and the second electrode.

Images