Semiconductor light-receiving element and optical device

Abstract

A semiconductor light-receiving element includes a substrate including a first surface and a second surface opposite 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 having a light-receiving portion that receives the incidence of light from the second surface side via the lens and a light-absorbing layer that includes at least a part of 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 different from the first conductivity type in the semiconductor mesa.

Description

Technical Field

[0001] This disclosure relates to a semiconductor light-receiving element and an optical device. Background Technology

[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 a surface opposite to the light-incident side of the n-type semiconductor substrate and includes a light-absorbing layer. The lens is disposed on the light-incident side surface of the n-type semiconductor substrate. The lens is positioned directly above the mesa of the light-receiving region.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2011-124450 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] However, in the aforementioned technical fields, further high speeds are desired, such as operating speeds exceeding 50 GHz. In this case, to improve responsiveness, it is desirable to thin the light-absorbing layer. However, if the light-absorbing layer is thinned, a decrease in sensitivity may become a problem.

[0008] Therefore, the purpose of this disclosure is to provide a semiconductor light-receiving element and an optical device that can improve sensitivity.

[0009] means for solving problems

[0010] The semiconductor light-receiving element disclosed herein is [1] "a semiconductor light-receiving element comprising: a substrate having a first surface and a second surface opposite to the first surface; a semiconductor mesa disposed on the first surface; a lens disposed on the second surface; and a first electrode and a second electrode disposed on the first surface and connected to the semiconductor mesa, the semiconductor mesa having: a light-receiving portion receiving incident light from the second surface via the lens; and a light-absorbing layer at least a portion of which is contained 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, 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, and, when viewed from a first direction intersecting the first surface of the substrate, the center of the light-receiving portion being offset relative to the center of the lens along a second direction intersecting the first direction, and when viewed from the first direction, the distance from the center of the lens along the second direction to the center of the light-receiving portion being greater than the distance from the center of the light-receiving portion along the second direction to the end of the light-receiving portion.

[0011] In this semiconductor light-receiving element, a semiconductor mesa comprising 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 to the first surface of the substrate. The light-receiving portion receives light incident from the second surface of the substrate via the lens. Furthermore, when viewed from a first direction intersecting the first surface of the substrate, the center of the light-receiving portion is offset relative to the center of the lens along a second direction intersecting the first direction. Therefore, light is incident obliquely onto the light-receiving portion and the light-absorbing layer according to the lens offset (distance between centers), ensuring that the optical path length is greater than or equal to the thickness of the light-absorbing layer. In particular, when viewed from the first direction, the lens offset is greater than the distance from the center of the light-receiving portion to its end. Therefore, a longer optical path length in the light-absorbing layer can be ensured, improving sensitivity.

[0012] The semiconductor light-receiving element disclosed herein may also be, [2] "the semiconductor light-receiving element according to [1], wherein a protrusion protrudes from the first surface, and the first electrode or the second electrode extends from the connection area with the semiconductor mesa to the top surface opposite to the first surface of the protrusion." In this case, by configuring the semiconductor light-receiving element such that the first surface of the substrate faces the external device, and using the area on the top surface of the protrusion of the first electrode or the second electrode as a connection terminal with the external device, it is possible to connect to the external device while protecting the semiconductor mesa. In addition, when the connection terminal of the first electrode or the second electrode is located between a connection member such as a solder bump, the height of the connection member can be suppressed only by the amount of the height of the protrusion.

[0013] The semiconductor light-receiving element disclosed herein can also be [3] "the semiconductor light-receiving element according to [2], wherein the protrusion includes a first protrusion and a second protrusion, the first electrode extends from the connection area with the semiconductor mesa to a first top surface opposite to the first surface of the first protrusion, and the second electrode extends from the connection area with the semiconductor mesa to a second top surface opposite to the first surface of the second protrusion." In this case, by configuring the semiconductor light-receiving element such that the first surface of the substrate faces the external device, and using the areas on the top surfaces of the first and second protrusions of the first and second electrodes as connection terminals with the external device, it is possible to connect to the external device while protecting the semiconductor mesa. In addition, when the connection terminals of the first and second electrodes are located between solder bumps or other connection members, the height of the connection member can be suppressed only by the amount of the height of the first and second protrusions.

[0014] The semiconductor light-receiving element disclosed herein may also be [4] "the semiconductor light-receiving element according to [2] or [3], wherein the protrusion is composed of a semiconductor laminate." In this case, the protrusion can be formed by a semiconductor manufacturing process.

[0015] The semiconductor light-receiving element disclosed herein may also be [5] "a semiconductor light-receiving element according to any one of [1] to [4], wherein, when viewed from the first direction, the distance from the center of the lens along the second direction to the center of the light-receiving portion is greater than the distance from the center of the light-absorbing layer along the second direction to the end of the light-absorbing layer." In this case, by more reliably ensuring a longer optical path length in the light-absorbing layer, sensitivity can be reliably improved.

[0016] The semiconductor light-receiving element disclosed herein can also be [6] "a semiconductor light-receiving element according to any one of [1] to [5], wherein, when viewed from the first direction, at least a portion of the light-absorbing layer overlaps with the lens." In this case, excessive offset of the lens relative to the light-receiving portion can be avoided. As a result, although the incident angle of light relative to the light-absorbing layer is limited, the error caused by the thickness of the substrate at the spot position of the incident light is reduced, and centering is easier.

[0017] The semiconductor light-receiving element disclosed herein can also be [7] "a semiconductor light-receiving element according to any one of [1] to [6], wherein, when viewed from the first direction, the entire light-absorbing layer overlaps with the lens." In this case, excessive offset of the lens relative to the light-receiving portion can be reliably avoided. As a result, although the incident angle of light relative to the light-absorbing layer is limited, errors caused by the thickness of the substrate at the spot position of the incident light can be reliably suppressed, and centering is easier.

[0018] The semiconductor light-receiving element disclosed herein may also be [8] "a semiconductor light-receiving element according to any one of [1] to [7], wherein the first electrode and the second electrode each have terminal regions that serve as connection terminals for connection to an external device, and the terminal regions do 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, the adverse effects of pressure applied from the second surface side to the terminal regions of the first electrode and the second electrode on the lens can be avoided.

[0019] The semiconductor light-receiving element disclosed herein may also be [9] "a semiconductor light-receiving element according to any one of [2] to [4], wherein, when viewed from the first direction, the protrusion does not overlap with the lens." In this case, when the semiconductor light-receiving element is mounted on an external device from the first surface side, the adverse effects of pressure applied to the protrusion from the second surface side on the lens can be avoided.

[0020] The semiconductor light-receiving element disclosed herein may also be

[10] "a semiconductor light-receiving element according to any one of [1] to [9], wherein a recess is formed in the substrate toward the first surface, and the second surface is the bottom surface of the recess." In this case, a lens is disposed on the bottom surface of the recess. As a result, damage to the lens surface or the adhesion of foreign matter can be prevented.

[0021] The semiconductor light-receiving element disclosed herein can also be

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

[10] , wherein the inner side surface of the recess is inclined relative to the first direction in such a way that the recess widens as it moves further away from the bottom surface." In this case, the wall portion of the recess (the portion having the inner side surface) is less likely to obstruct light incident obliquely onto the lens. Therefore, the effective area of ​​the lens can be increased.

[0022] The semiconductor light-receiving element disclosed herein may also be

[12] "a semiconductor light-receiving element according to any one of [1] to

[11] , wherein, when viewed from the first direction, the distance between one end of the lens and the other end opposite to that end is more than 5 times the distance between one end of the light-receiving portion and the other end opposite to that end." In this case, the effective area of ​​the lens can be increased.

[0023] The semiconductor light-receiving element disclosed herein may also be

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

[12] , wherein the thickness of the light-absorbing layer is 1.2 μm or less." In this case, high-speed readout is possible (achieving high speed).

[0024] The optical device involved in this disclosure

[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, the semiconductor light-receiving element being arranged such that its first surface faces the surface of the amplifier, and being electrically connected to the amplifier via connecting members respectively provided on the first electrode and the second electrode."

[0025] This optical device includes the aforementioned semiconductor light-receiving element. Therefore, sensitivity can be improved. Furthermore, in this optical device, the semiconductor light-receiving element is arranged such that the first surface of the substrate faces the surface of the amplifier, and is electrically connected to the amplifier via connecting members respectively provided on the first electrode and the second electrode. That is, the semiconductor light-receiving element is directly provided to the amplifier via the first electrode and the second electrode on the first surface side and the connecting member (e.g., solder bump). As a result, for example, compared to the case where the semiconductor light-receiving element is mounted on a sub-mount and the sub-mount is connected to the amplifier via a wire, the inductance of the sub-mount and the wire 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 less inductance deviation can be achieved.

[0026] Invention Effects

[0027] According to this disclosure, a semiconductor light-receiving element and an optical device that can improve sensitivity can be provided. Attached Figure Description

[0028] Figure 1 This is a schematic side view of an optical device according to one embodiment.

[0029] Figure 2 yes Figure 1 A schematic top view of the semiconductor light-receiving element shown.

[0030] Figure 3 It is along Figure 2 A schematic cross-sectional view of line III-III.

[0031] Figure 4 It is along Figure 2 A schematic cross-sectional view of line IV-IV.

[0032] Figure 5 This is a schematic cross-sectional view showing the semiconductor light-receiving element involved in the modified example.

[0033] Figure 6 This is a cross-sectional view showing the semiconductor light-receiving element involved in other variations. Detailed Implementation

[0034] Hereinafter, an embodiment of the semiconductor light-receiving element and optical device according to this disclosure will be described in detail with reference to the accompanying drawings. Furthermore, in the figures, the same or equivalent elements are labeled with the same reference numerals, and repeated descriptions are sometimes omitted. Additionally, in the figures, a rectangular coordinate system is sometimes shown, consisting of 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 both the first direction D1 and the second direction D2.

[0035] Figure 1 This is a schematic side view illustrating an optical device according to one embodiment. For example... Figure 1 As shown, the optical device 100 includes a semiconductor light-receiving element 1. As an example, the optical device 100 can receive light L in the optical communication bands of 1.3μm (O-band (Original-band)), 1.55μm (C-band (Conventional-band)) and 1.6μm (L-band (Long-wavelength-band)), and can convert the light into an electrical signal and output it.

[0036] The 1.3μm band refers to, for example, a wavelength range of 1.26μm or higher and 1.36μm or lower. The 1.55μm band refers to, for example, a wavelength range of 1.53μm or higher and 1.56μm or lower. The 1.6μm band refers to, for example, a wavelength range of 1.565μm or higher and 1.625μm or lower. Furthermore, the light L in a communication band refers to light that has a peak value within the wavelength range of any of the above bands (i.e., wavelengths other than the peak value may also be outside the wavelength range of the above bands).

[0037] Therefore, the semiconductor light-receiving element 1 can be an element that targets the aforementioned wavelength band, or it can be an element that receives incident light L of at least one wavelength band belonging to that wavelength band and generates an electrical signal based on the incident light. The semiconductor light-receiving element 1 is mounted on a transimpedance amplifier (TIA) A (amplifier, external device) via connecting parts A3 and A4 such as solder bumps.

[0038] More specifically, the semiconductor light-receiving element 1 is arranged such that each of 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 is opposite to each of 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 via connecting members A3 and A4 between each of the first electrode 40 and the second electrode 50 and each of the electrode pads A1 and A2. Thus, in this embodiment, the semiconductor light-receiving element 1 is mounted to the transimpedance amplifier A via flip-chip bonding.

[0039] As an example, light L is guided by an optical fiber (not shown) and passes through a substrate 10 (see reference 10) formed on the semiconductor light-receiving element 1. Figure 3 , Figure 4 The lens RL (etc.) is directed toward the semiconductor stack 20 (refer to) formed on the semiconductor light-receiving element 1. Figure 3 , Figure 4 The light-receiving portion 30 (etc.) focuses the light. That is, in this embodiment, the semiconductor light-receiving element 1 is configured as a back-side incident type element that receives incident light L from the substrate 10 side toward the semiconductor stack 20. More specifically, the semiconductor light-receiving element 1 receives incident light L from the back-side 10r side (described later), and the light L is guided from the substrate 10 side to the semiconductor stack 20.

[0040] As described later, in the semiconductor light-receiving element 1, the lens RL is offset relative to the light-receiving portion 30 along the second direction D2. Therefore, light L is incident at an angle relative to the lens RL and the light-receiving portion 30. The electrical signal generated by the semiconductor light-receiving element 1 corresponding to the incident 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.

[0041] Figure 2 yes Figure 1 A schematic top view of the semiconductor light-receiving element shown. Figure 3 As along Figure 2 Schematic cross-sectional view of line III-III Figure 2 , Figure 3 As shown, the semiconductor light-receiving element 1 includes a substrate 10, a semiconductor stack 20, a first electrode 40, and a second electrode 50.

[0042] The substrate 10 comprises a semi-insulating semiconductor. Here, the substrate 10 is, for example, a semi-insulating semiconductor substrate made of InP. The substrate 10 includes a surface (first surface) 10a and a back surface 10r opposite to the surface 10a. A first direction D1 is a direction that intersects (orthogonally) the surface 10a and the back surface 10r. Viewed from a second direction D2 that intersects (orthogonally) the first direction D1, the substrate 10 includes a plurality of regions RA, RB, and RC arranged sequentially along the surface 10a and the back surface 10r. Region RB is the region between region RA and region RC. More specifically, region RB includes a central region RB1 and regions RB2 located on both sides of region RB1 (regions RA and RC sides).

[0043] 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 portion 30 is formed on the bottom surface 10b (the second surface opposite to the surface 10a) of the recess 10C. Therefore, the back surface 10r and the bottom surface 10b of the substrate 10 are the incident surfaces of light L. The lens RL is formed in such a way that it partially overlaps with region RB2 with region RB1 as the center.

[0044] A semiconductor stack 20 is formed on a substrate 10. More specifically, the semiconductor stack 20 is formed on a surface 10a in region RB of the substrate 10. The semiconductor stack 20 includes a back surface 20b on the substrate 10 side and a surface 20a on the opposite side of the substrate 10. The semiconductor stack 20 includes a buffer layer 21, a buffer layer 22, a capacitance reduction layer 23, a light absorption layer 24, a capping layer 25, and a contact layer 26 sequentially stacked from the substrate 10 side. Here, the back surface 20b of the semiconductor stack 20 is the side opposite to the light absorption layer 24 in the buffer layer 21 and is in contact with the surface 10a of the substrate 10. The surface 20a of the semiconductor stack 20 is the side opposite to the light absorption layer 24 in the contact layer 26.

[0045] Buffer layer 21 has a first conductivity type (in this case, N-type, for example, N). +(Type). The buffer layer 21 is provided in such a way that region RB1 is set as the center and region RB2 is repeated. The layers other than the buffer layer 21 of the semiconductor stack 20 (buffer layer 22, capacitance reduction layer 23, light absorption layer 24, cover layer 25, and contact layer 26) are provided on the region that repeats region RB1 in the buffer layer 21. Therefore, the buffer layer 21 has a portion 21p exposed from the layers other than the buffer layer 21 of the semiconductor stack 20 and the protective film 60 described later. The semiconductor stack 20 constitutes a semiconductor mesa M containing a compound semiconductor. In the semiconductor light-receiving element 1, a connection to the first electrode 40 is formed in this portion 21p of the buffer layer 21. That is, the first electrode 40 is connected to the region (portion 21p) of the first conductivity type of the semiconductor stack 20 (semiconductor mesa M). The buffer layer 21 contains, for example, InP, and as an example, contains N. + -InP.

[0046] Buffer layer 22 has a first conductivity type (in this case, N-type, for example, N). + (Type). Buffer layer 22, for example, contains InP or InGaAsP, and as an example, is composed of N... + -InP or N + -InGaAsP structure. Buffer layer 21 and buffer layer 22 constitute the first semiconductor layer S1 (here, of the first conductivity type) located between substrate 10 and light-absorbing layer 24.

[0047] The carrier concentration of buffer layer 22 is higher than that of capacitance reduction layer 23, which will be described later. As an example, the carrier concentration of buffer layer 22 is 5 × 10⁻⁶. 16 cm -3 Above and 5×10 18 cm -3 The thickness of the buffer layer 22 is, for example, 0.5 μm or more and 2.5 μm or less.

[0048] Additionally, buffer layers 21 and 22 can also function as strain mitigation layers by having a lattice constant between the lattice constant of the substrate 10 and the lattice constant of the light-absorbing layer 24. That is, the semiconductor stack 20 may include a plurality of strain mitigation layers (stepped layers) arranged such that the lattice constant gradually approaches the lattice constant of the light-absorbing layer 24 as it moves from the substrate 10 toward the light-absorbing layer 24.

[0049] The capacitance reduction layer 23 has a first conductivity type (in this case, N-type, for example, N). + (Type). The capacitance reduction layer 23 may contain, for example, any one of InP, InGaAsP, InAsP, and AlInGaAs. As an example, it is composed of N... - -InP、N - -InGaAsP,N --InAsP and N - - It can be constructed from any of Al, In, GaAs. The capacitance reduction layer 23 is located between the first semiconductor layer S1 and the light absorption layer 24. Here, the capacitance reduction layer 23 is in contact with the first semiconductor layer S1 and the light absorption layer 24.

[0050] The light-absorbing layer 24 has a first conductivity type (in this case, N-type, for example, N). - (Type). Here, the light absorption layer 24 is made of N. - -In x Ga 1-x The light-absorbing layer 24 is composed of As. The In composition x can also be 0.55 or more (and less than 1). In this case, as an example, the In composition x is 0.59. In addition, the thickness of the light-absorbing layer 24 (the thickness along the stacking direction of the semiconductor stack 20) ​​is 0.3 μm or more and 1.2 μm or less, as an example, 1.0 μm or less, and as another example, 0.75 μm or less. The thickness of the light-absorbing layer 24 is 0.7 μm as an example here. In addition, the band gap of the light-absorbing layer 24 is, for example, in the range of 0.72 eV or less, and contains Al, P, Sb, N, and other materials (for example, it can also be a mixed absorption layer of InGaAs and such materials). In this case, as an example, the light-absorbing layer 24 can be composed of 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.

[0051] Here, the capacitance reduction layer 23 has a higher carrier concentration than the light absorption layer 24. As an example, the carrier concentration of the capacitance reduction layer 23 is 1.5 × 10⁻⁶. 14 cm -3 Above and 3×10 16 cm -3 The impurity concentration of the light absorption layer 24 is 1×10⁻⁶. 14 cm -3 Above and 6×10 15 cm -3 Furthermore, the capacitance reduction layer 23 has a larger band gap than the light absorption layer 24. As described above, the band gap of the light absorption layer 24 is below 0.72 eV, and the band gap of the capacitance reduction layer 23 is greater than 0.72 eV, which can be set to a range of below 1.35 eV.

[0052] As the capacitance reduction layer 23, it is required that the carrier concentration be higher than that of the light absorption layer 24, as described above, and that it be depleted when a bias voltage is applied. The reason for this is that, as described above, the capacitance reduction layer 23 has a larger band gap than the light absorption layer 24. Therefore, when the carrier concentration is low, a potential barrier is formed in the conduction band. The large potential barrier hinders the movement of carriers and may prevent them from being properly extracted.

[0053] Furthermore, as a capacitance reduction layer 23, it needs to be depleted when a bias voltage is applied; therefore, its upper limit for carrier concentration can be set to 6.0 × 10⁻⁶ as described above. 15 cm -3 Furthermore, the capacitance reduction layer 23 can be composed of elements that do not absorb incident light (i.e., have a wider bandgap than the light absorption layer 24). This is because if incident light is absorbed in the capacitance reduction layer 23, charge carriers are generated within it. These charge carriers are extracted as signals from the capacitance reduction layer 23 via the light absorption layer 24, thus becoming slow charge carriers and potentially degrading the responsiveness. As an example, the sensitivity wavelength region of the capacitance reduction layer 23 can be set to below 1.31 μm.

[0054] By setting the relationship between the capacitance reduction layer 23 and the light absorption layer 24 as described above, the capacitance can be reduced without reducing the carrier response. As an example, the thickness of the capacitance reduction layer 23 can be set to be 0.1 μm or more and 3.0 μm or less.

[0055] Furthermore, in the semiconductor light-receiving element 1, the light-absorbing layer 24 is a single layer. A single layer means that the light-absorbing layer 24 does not have a stacked structure composed of two or more layers with different compositions or properties. More specifically, a single layer means, for example, that it does not have a superlattice structure formed by repeatedly stacking multiple layers with different compositions.

[0056] The capping layer 25 has a first conductivity type (in this case, N-type, for example, N). - (Type). The capping layer 25, for example, contains InP or InGaAsP. As an example, the capping layer 25 is composed of N... - -InP or N - The capping layer 25 is composed of InGaAsP. The carrier concentration of the capping layer 25 is, for example, 1 × 10⁻⁶. 14 cm -3 Above and 1×10 16 cm -3 The thickness of the capping layer 25 is, for example, 0.1 μm or more and 0.5 μm or less.

[0057] Contact layer 26 has a first conductivity type (in this case, N-type, for example, N). - (Type). Contact layer 26, for example, contains InGaAs, and as an example, is composed of N...- It is composed of InGaAs. The carrier concentration of the contact layer 26 is, for example, 1 × 10⁻⁶. 14 cm -3 Above and 1×10 16 cm -3 The thickness of the contact layer 26 is, for example, 0.1 μm or more and 0.2 μm or less.

[0058] In the semiconductor stack 20, a second conductivity type (here, P-type, as an example, P) is formed. + The second region 27 (of type 24) is formed, for example, by thermal diffusion or ion implantation. The second region 27 extends from the surface 20a of the semiconductor stack 20 toward the substrate 10. Here, the second region 27 is formed such that it extends from the contact layer 26 through the capping layer 25 to the light-absorbing layer 24. In this way, the capping layer 25 and the contact layer 26 constitute a second semiconductor layer S2 located on the side opposite to the substrate 10 relative to the light-absorbing layer 24. The second semiconductor layer S2 includes a second region 27 (of type 24) that forms a PN junction with the light-absorbing layer 24. The second region 27 and the light-absorbing layer 24 together constitute a light-receiving portion 30 included in the semiconductor mesa M. The light-receiving portion 30 is the portion of the semiconductor mesa M that overlaps with the second region 27 when viewed from the first direction D1.

[0059] Here, the second region 27 (i.e., the light-receiving portion 30) is formed in a portion (e.g., including a central portion) of the width direction (the direction intersecting the first direction D1) of the semiconductor mesa M. Therefore, the semiconductor mesa M includes a third region 28 of a first conductivity type surrounding the second region 27 when viewed from the first direction D1. In addition, a portion of the central side of the light-absorbing layer 24 is included in the light-receiving portion 30.

[0060] Alternatively, the second region 27 may extend inside the light-absorbing layer 24. In this case, the light-absorbing layer 24 includes a fifth region 27a of a second conductivity type, which is an extension of the second region 27, and a first region 24a of a 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 within a range of 0.2 μm on the side of the capping layer 25 in the light-absorbing layer 24. That is, in this example, inside the light-absorbing layer 24, a first region 24a with a thickness of about 0.5 μm and a fifth region 27a with a thickness of 0.2 μm are included, forming their boundary. In the fifth region 27a, P + In the case of the P-type, as an example, the carrier concentration is 1 × 10⁻⁶. 17 cm -3 The following locations.

[0061] On the other hand, when the second region 27 does not reach the interior of the light-absorbing layer 24, the entire light-absorbing layer 24 becomes the first region 24a of the first conductivity type. Furthermore, in this embodiment, N... + Type refers to N-type carrier concentration of 1×10⁻⁶. 17 cm -3 That's all. N - The type refers to the N-type carrier concentration of 3.0 × 10⁻⁶. 16 cm -3 The following means with N + The type is relatively low. Additionally, P... + Type refers to the P-type where the carrier concentration is 1×10⁻⁶. 17 cm -3 above.

[0062] 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 stack 20 and the side surface 20s of the semiconductor stack 20 extending from the periphery of the surface 20a toward the substrate 10 are covered by the protective film 60. On the other hand, the remaining portion of the surface 20a of the semiconductor stack 20, here the surface of the second region 27, is exposed from the protective film 60. Furthermore, a second electrode 50 is formed on the portion of the surface 20a exposed from the protective film 60, and a bond 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 portion (second region 27) of the semiconductor stack 20 located on the side opposite to the light-absorbing layer 24 and the substrate 10.

[0063] In other words, the second electrode 50 is connected to the region of the second conductivity type (second region 27) in the semiconductor mesa M. On the other hand, the first electrode 40 is connected to the portion 21p of the first conductivity type in the semiconductor stack 20 located on the substrate 10 side relative to the light absorption layer 24 (the portion of the buffer layer 21 exposed from the protective film 60).

[0064] Figure 4 It is along Figure 2 A schematic cross-sectional view of line IV-IV. Figure 4 The orthogonal coordinate system shown and along Figure 2 The cross-section of line IV-IV corresponds to the cross-section containing the second direction D2 and the first direction D1. Furthermore, in Figure 4 In, along relative to Figure 2 The diagram of the portion of the IV-IV line inclined in the second direction D2 is omitted, as are the lens, the recess, and a portion of the first electrode 40.

[0065] like Figure 2 , Figure 4As shown, the semiconductor light-receiving element 1 has protrusions. 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 protrude 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 composed of a semiconductor laminate. More specifically, the first protrusion C1 and the second protrusion C2 are composed of the same semiconductor layer as the semiconductor laminate 20. That is, the first protrusion C1 and the second protrusion C2 are semiconductor mesa containing a compound semiconductor. The first protrusion C1 and the second protrusion C2 are covered by a protective film 60.

[0066] The first electrode 40 extends from the connection region (part 21p) with the semiconductor stack 20 (i.e., the semiconductor mesa M) to the first top surface C1s on the side opposite to the surface 10a of the first protrusion C1. The portion of the first electrode 40 located on the first top surface C1s is configured as a terminal region (electrode pad) 40p that serves as a connection terminal to 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.

[0067] The second electrode 50 extends from the connection region (second region 27) with the semiconductor stack 20 (i.e., semiconductor mesa M) to the second top surface C2s on the side opposite to the surface 10a of the second protrusion C2. The portion of the second electrode 50 located on the second top surface C2s is designated as a terminal region (electrode pad) 50p, which becomes a connection terminal to 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.

[0068] In this way, in the optical device 100, the semiconductor light-receiving element 1 is arranged with its surface 10a facing the surface of the transimpedance amplifier A, and is electrically connected to the transimpedance amplifier A via connecting members A3 and A4 respectively provided on the first electrode 40 and the second electrode 50. As described above, in the semiconductor light-receiving element 1, the first electrode 40 or the second electrode 50 extends from the top surface opposite to the surface 10a of the protrusion from the connection area with the semiconductor mesa M.

[0069] In addition, such as Figure 2 As shown, the semiconductor light-receiving element 1 includes a pair of first protrusions C1 arranged such that they sandwich the second protrusion C2 along a third direction D3. Figure 4The diagram shows only one first protrusion C1. The first electrode 40 extends from one first protrusion C1 to another first protrusion C1 via a connection region (part 21p) with the semiconductor mesa M. Furthermore, terminal regions 40p are formed on the first top surfaces C1s of each pair of first protrusions C1.

[0070] Furthermore, the semiconductor light-receiving element 1 includes a pair of third protrusions C3 arranged along a 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 containing the same semiconductor layer as the semiconductor stack 20. In this case, the third protrusions C3 are semiconductor mesa containing a compound semiconductor. An electrode Md is formed on the top surface of the pair of third protrusions C3 opposite to the surface 10a of the substrate 10. The electrode Md is not electrically connected to the semiconductor mesa M, the first electrode 40, the second electrode 50, or other semiconductor layers and electrodes; instead, it is dummy (virtual electrode, virtual pad). The semiconductor light-receiving element 1 is rectangular when viewed from the first direction D1, and the pair of first protrusions C1 and the pair of third protrusions C3 are arranged at the four corners of the semiconductor light-receiving element 1. In this way, by including the dummy third protrusions C3 in the semiconductor light-receiving element 1, the connection area with the transimpedance amplifier A becomes four or more locations, achieving stabilization during flip-chip bonding.

[0071] Here, as Figure 4 As shown, in the semiconductor light-receiving element 1, when viewed from the first direction D1, the center of the light-receiving portion 30 of the semiconductor mesa M is offset relative to the center of the lens RL along the second direction D2 (consistent with respect to the third direction D3). When viewed from the first direction D1, the distance OA from the center of the lens RL along the second direction D2 to the center of the light-receiving portion 30 is greater than the distance O1 from the center of the light-receiving portion 30 along the second direction D2 to the end of the light-receiving portion 30. Therefore, the light-receiving portion 30 receives incident light L from the back surface 10r side via the lens RL at an angle relative to the first direction D1. Furthermore, the light-absorbing layer 24 absorbs the light L incident at an angle relative to the thickness direction (first direction D1) of the light-absorbing layer 24.

[0072] The second electrode 50 extends from the connection region (second region 27) with the semiconductor mesa M in a direction opposite to the offset direction (in this case, the negative direction of the second direction D2) relative to the light-receiving portion 30 of the lens RL (i.e., the positive direction of the second direction D2), reaching 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) relative to the light-receiving portion 30 of the lens RL.

[0073] In this embodiment, in the second direction D2, the light-absorbing layer 24 is larger than the light-receiving portion 30, but the distance OA is greater than the distance O2 from the center to the end of the light-absorbing layer 24. On the other hand, in this embodiment, when viewed from the first direction D1, a portion of the light-absorbing layer 24 (and the light-receiving portion 30) overlaps with the lens RL. Furthermore, 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 consequently, the first protrusion C1 and the second protrusion C2 do not overlap with the lens RL.

[0074] Furthermore, the center of each of the light-receiving portion 30, the light-absorbing layer 24, and the lens RL is its own center of gravity. Also, 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 that end can be more than five times the distance T1 between one end of the light-receiving portion 30 and the other end opposite to that end.

[0075] Furthermore, as described above, a recess 10C is formed on the back surface 10r of the substrate 10, recessed towards the surface 10a, and a lens RL is formed on the bottom surface 10b of this recess 10C. The inner surface 10Cs of the recess 10C are inclined relative to the first direction D1 such that the recess 10C widens as it moves away from the bottom surface 10b. The entire lens RL is located within the recess 10C (and does not protrude from the back surface 10r).

[0076] As explained 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 side 10r of the substrate 10. The light-receiving portion 30 receives light L incident via the lens RL from the back side 10r of the substrate 10. Moreover, when viewed from the first direction D1, the center of the light-receiving portion 30 is offset relative to the center of the lens RL along the second direction D2. Therefore, the light L is incident obliquely into the light-absorbing layer 24 according to the offset of the lens RL (the distance OA between the centers), and the optical path length can be ensured to be greater than or equal to the thickness of the light-absorbing layer 24. In particular, when viewed from the first direction D1, the offset of the lens RL is greater than the distance O1 from the center of the light-receiving portion 30 to the end of the light-receiving portion 30. Therefore, a longer optical path length in the light-absorbing layer 24 can be ensured, and the sensitivity can be improved.

[0077] Furthermore, the semiconductor light-receiving element 1 according to this embodiment has 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 the connection region (part 21p) with the semiconductor mesa M to the first top surface C1s of the first protrusion C1, and the second electrode 50 extends from the connection region (second region 27) with the semiconductor mesa M to the second top surface C2s of the second protrusion C2. Therefore, by arranging the semiconductor light-receiving element 1 with the surface 10a side of the substrate 10 facing the transimpedance amplifier A (external device), and using the areas on the top surfaces of the first protrusion C1 and the second protrusion C2 of the first electrode 40 and the second electrode 50 as connection terminals with the transimpedance amplifier A, the semiconductor mesa M can be protected and the connection with the transimpedance amplifier A can be made. Furthermore, when the connection terminals of the first electrode 40 and the second electrode 50 are positioned between the connection members A3 and A4 such as solder bumps, the height of the connection members A3 and A4 can be suppressed by the amount of the height of the first protrusion C1 and the second protrusion C2.

[0078] Furthermore, in the semiconductor light-receiving element 1 according to this embodiment, the first protrusion C1 and the second protrusion C2 (i.e., protrusions) are composed of a semiconductor laminate. Therefore, the first protrusion C1 and the second protrusion C2 can be formed by semiconductor manufacturing processes.

[0079] 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 longer optical path length in the light-absorbing layer 24, the sensitivity can be reliably improved.

[0080] Furthermore, in the semiconductor light-receiving element 1 according to this embodiment, when viewed from the first direction D1, a portion of the light-absorbing layer 24 overlaps with the lens RL. Therefore, excessive offset of the lens RL relative to the light-receiving portion 30 can be avoided. As a result, although the incident angle of light L relative to the light-absorbing layer 24 is limited, the error caused by the thickness of the substrate 10 at the incident light spot position is reduced, making centering easier.

[0081] 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 and 50p that serve as connection terminals to the transimpedance amplifier A. Furthermore, when viewed from the first direction D1, the terminal regions 40p and 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 surface 10a side, the adverse effects of pressure applied from the back side 10r to the terminal regions 40p and 50p of the first electrode 40 and the second electrode 50 on the lens RL can be avoided.

[0082] Furthermore, in the semiconductor light-receiving element 1 according to this embodiment, when viewed from the first direction D1, the first protrusion C1 and the second protrusion C2 (i.e., the protrusions) do not overlap with the lens RL. Therefore, when the semiconductor light-receiving element 1 is mounted on the transimpedance amplifier A from the surface 10a side, the adverse effects of the pressure applied to the first protrusion C1 and the second protrusion C2 from the back side 10r side on the lens RL can be avoided.

[0083] Furthermore, in the semiconductor light-receiving element 1 according to this embodiment, a recess 10C is formed on the substrate 10 that is recessed toward the surface 10a, and the lens RL is disposed on the bottom surface 10b of the recess 10C in the back surface 10r of the substrate 10. Therefore, it is possible to prevent damage to the surface of the lens RL or the adhesion of foreign matter.

[0084] Furthermore, in the semiconductor light-receiving element 1 according to this embodiment, the inner surface 10Cs of the recess 10C is inclined relative to the first direction D1 in such a way that the recess 10C expands further away from the bottom surface 10b. Therefore, the wall portion of the recess 10C (the portion having the inner surface 10Cs) is less likely to obstruct the light L incident obliquely onto the lens RL. Therefore, the effective area of ​​the lens RL can be increased.

[0085] 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 that end can be more than 5 times the distance T1 between one end of the light-receiving portion 30 and the other end opposite to that end. In this case, the effective area of ​​the lens RL can be increased.

[0086] Furthermore, in the semiconductor light-receiving element 1 according to this embodiment, the thickness of the light-absorbing layer 24 can be 1.2 μm or less. In this case, high-speed readout is possible (achieving high speed).

[0087] 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. Moreover, the semiconductor light-receiving element 1 is arranged 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 connection members A3 and A4 provided on the first electrode 40 and the second electrode 50, respectively.

[0088] The optical device 100 includes the aforementioned semiconductor light-receiving element 1. Therefore, sensitivity can be improved. Furthermore, in this optical device 100, the semiconductor light-receiving element 1 is arranged 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 parts 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 provided to the transimpedance amplifier A via the first electrode 40 and the second electrode 50 on the surface 10a and the connecting parts A3 and A4 (e.g., solder bumps). As a result, for example, compared to the case where the semiconductor light-receiving element 1 is mounted on a sub-mount and the sub-mount is connected to the transimpedance amplifier A via wires, the inductance of the sub-mount and the wires can be removed 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, an optical device 100 with less inductance deviation can be achieved.

[0089] The above embodiments illustrate one aspect of the semiconductor light-receiving element and optical device involved in this disclosure. Therefore, the semiconductor light-receiving element and optical device involved in this disclosure are not limited to the above embodiments and can be arbitrarily modified. Next, modified examples will be described.

[0090] Figure 5 This is a schematic cross-sectional view showing the semiconductor light-receiving element involved in the modified example. Figure 5 The cross section is equivalent to along Figure 2 The cross-section of line III-III. In Figure 5 In the example shown, the second semiconductor layer S2 (i.e., the capping layer 25 and the contact layer 26) is configured as a second conductivity type (here, P-type, as an example, P). + The second semiconductor layer S2 is composed 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-absorbing layer 24.

[0091] In this case, the second region 27 of the second conductivity type does not extend into the interior of the light-absorbing layer 24. However, in this case, the second region 27 may also contain a second conductivity type (here, P-type, as an example) stacked on the light-absorbing layer 24. +Other light-absorbing layers 27b of the first conductivity type. Light-absorbing layer 27b is located on the opposite side of capacitance reduction layer 23 relative to light-absorbing layer 24. In this case, the entire light-absorbing layer 24 forms the first region 24a of the first conductivity type. Light-absorbing layer 27b can be made of the same material as the light-absorbing layer 24 described above, for example, containing InGaAs, or, as an example, P… + -InGaAs composition.

[0092] The thickness of the light absorption layer 27b can be thicker or thinner than the thickness of the light absorption layer 24. When the thickness of the light absorption layer 27b is thinner than the thickness of the light absorption layer 24, an improvement in response speed can be achieved. Furthermore, in... Figure 5 In the example shown, contact with the second electrode 50 is achieved in the contact layer 26, but by providing a second conductive light absorption layer 27b, contact with the second electrode 50 can also be achieved in the light absorption layer 27b.

[0093] As mentioned above, in Figure 5 In the example shown, the second region 27 is formed over the entire semiconductor mesa M in a direction intersecting the first direction D1. In other words, the entire light-absorbing layer 24 is contained within the light-receiving portion 30. Therefore, in Figure 5 In the example shown, in the direction intersecting the first direction D1, the width of the light-receiving portion 30 is the same as the width of the light-absorbing layer 24. Figure 5 In the example shown, the light-receiving portion 30 and the lens RL are also offset along the second direction D2. However, in this case, the distance O1 from the center of the light-receiving portion 30 to its end along the second direction D2 coincides with the distance O2 from the center of the light-absorbing layer 24 to its end along the second direction D2. Therefore, in this case, when viewed from the first direction D1, a portion of the light-receiving portion 30 overlapping with the lens RL is synonymous with a portion of the light-absorbing layer 24 overlapping with the lens RL.

[0094] Figure 6 This is a cross-sectional view showing the semiconductor light-receiving element involved in other variations. Figure 6 The cross section is equivalent to along Figure 2 The cross-section of line III-III. In Figure 6 In the example shown, buffer layer 21 and buffer layer 22 have a second conductivity type (in this case, P-type, e.g., P235). + (Type). Buffer layer 21, for example, contains InP, as an example, composed of P. + -InP is used. Buffer layer 22 contains, for example, InP or InGaAsP, as an example, composed of P + -InP or P + -InGaAsP composition.

[0095] In addition, Figure 6 In the example shown, the cover layer 25 and the contact layer 26 have a first conductivity type (in this case, N-type, e.g., N0). + (Type). The capping layer 25, for example, contains InP or InGaAsP. As an example, the capping layer 25 is composed of N... + -InP or N + -InGaAsP is composed. Contact layer 26, for example, contains InGaAs, and as an example, is composed of N... + It is composed of InGaAs. The conductivity of the capacitance reduction layer 23 and the light absorption layer 24 is the same as in the above embodiment.

[0096] Like this, in Figure 6 In the example shown, the first semiconductor layer S1 has a second conductivity type, and the second semiconductor layer S2 has a first conductivity type. Furthermore, the capacitance reduction layer 23 is located between the light absorption 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 absorption layer 24.

[0097] In this way, the capacitance reduction layer 23 is located in one of the semiconductor layers, the first semiconductor layer S1 and the second semiconductor layer S2 (as described in the above embodiments and...). Figure 5 In the example, the first semiconductor layer S1 is used. Figure 6 In the example, this is between the second semiconductor layer S2 and the light-absorbing layer 24. Furthermore, the other semiconductor layer in the first semiconductor layer S1 and the second semiconductor layer S2 (as described in the above embodiment and...) Figure 5 In the example, it is the second semiconductor layer S2, in Figure 6 In the example, the first semiconductor layer S1) includes a second region 27 of the second conductivity type that forms a PN junction with the light absorption layer 24 (first region 24a).

[0098] In addition, Figure 6 In this example, the buffer layer 22 includes a first layer 22a extending from region RB1 of the substrate 10 to region RB2, 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 sequentially starting 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, where the portion 22p is connected to the first electrode 40.

[0099] As mentioned above, in Figure 6 In the example shown, the second region 27 is also formed over the entire semiconductor mesa M in a direction intersecting the first direction D1. In other words, the entire light-absorbing layer 24 is included in the light-receiving portion 30. Therefore, in Figure 6 In the example shown, with Figure 5Similarly, in the example shown, the width of the light-receiving portion 30 is the same as the width of the light-absorbing layers 24 and 27b in the direction intersecting the first direction D1. Figure 6 In the example shown, the light-receiving portion 30 and the lens RL are also offset along the second direction D2. However, in this case, the distance O1 from the center of the light-receiving portion 30 along the second direction D2 to its end coincides with the distance O2 from the center of the light-absorbing layer 24 along the second direction D2 to its end. Therefore, in this case, when viewed from the first direction D1, a portion of the light-receiving portion 30 overlapping with the lens RL is synonymous with a portion of the light-absorbing layer 24 overlapping with the lens RL.

[0100] Next, other variations will be described. In the semiconductor light-receiving element 1 according to the above embodiment, 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 relative to the light-receiving portion 30 can be reliably avoided. As a result, although the incident angle of light L relative to the light-absorbing layer 24 is limited, errors caused by the thickness of the substrate 10 at the spot position of the incident light can be reliably suppressed, and centering is easier.

[0101] Furthermore, in the semiconductor light-receiving element 1 according to the above embodiment, an example is shown where the centers of the light-receiving portion 30 and the light-absorbing layer 24 are offset relative to the center of the lens RL in the second direction D2 and coincide in the third direction D3. However, the centers of the light-receiving portion 30 and the light-absorbing layer 24 may also be offset relative to the center of the lens RL in the third direction D3 in addition to the second direction D2. 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 can be set in a manner greater than the shortest distance among the distances from the center of the light-receiving portion 30 in any direction to the end of the light-receiving portion 30, or it can be set in a manner greater than at least one of the distance O1 from the center of the light-receiving portion 30 in the second direction D2 to the end of the light-receiving portion 30 and the distance from the center of the light-receiving portion 30 in the third direction D3 to the end of the light-receiving portion 30. The positional relationship of the light-absorbing layer 24 is also the same.

[0102] That is, in this case, when viewed from the first direction D1, the distance OA can be set in a manner that is greater than the shortest distance among the distances from the center of the light-absorbing layer 24 to the end of the light-absorbing layer 24 in any direction, or it can be set in a manner that is greater 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.

[0103] Furthermore, in the above embodiment, the first protrusion C1 and the second protrusion C2 (and consequently the third protrusion C3 (hereinafter the same)) are illustrated as being constructed from a semiconductor laminate. However, the first protrusion C1 and the second protrusion C2 may also have other structures. For example, the first protrusion C1 and the second protrusion C2 may also be constructed from a metal or an insulator. When the first protrusion C1 and the second protrusion C2 are constructed from a metal, each of the first electrode 40 and the second electrode 50 is configured to be locally thicker, thereby enabling the construction of the first protrusion C1 and the second protrusion C2. Alternatively, when the first protrusion C1 and the second protrusion C2 are constructed from an insulator, the first protrusion C1 and the second protrusion C2 can be constructed by locally thickening the insulating film such as the protective film 60.

[0104] Alternatively, when the first protrusion C1 and the second protrusion C2 are formed by a semiconductor stack, the portions corresponding to the first protrusion C1 and the second protrusion C2 may not be etched during the etching of the semiconductor layer used to form the semiconductor mesa M, leaving them as residues, thereby forming the first protrusion C1 and the second protrusion C2. Alternatively, the first protrusion C1 and the second protrusion C2 may be formed by stacking a semiconductor layer on the surface 10a of the substrate 10 after the etching used to form the semiconductor mesa M.

[0105] Furthermore, the semiconductor mesa M, the first protrusion C1, and the second protrusion C2 are not limited to being formed completely independently by forming grooves between each other to reach the surface 10a of the substrate 10. For example, the semiconductor mesa M, the first protrusion C1, and the second protrusion C2 may also be configured to be insulated from each other and embedded therein.

[0106] Alternatively, the first protrusion C1 and the second protrusion C2 can be formed as a single mesa. The first protrusion C1 and the second protrusion C2 can be configured as different mesas, and a portion of the semiconductor layer closer to the substrate 10 can be shared between them. Furthermore, the semiconductor mesa M (i.e., the semiconductor stack 20) ​​and the first protrusion C1 and / or the second protrusion C2 can be formed as a single mesa, or the semiconductor mesa M and the first protrusion C1 and / or the second protrusion C2 can be configured as different mesas, and a portion of the semiconductor layer closer to the substrate 10 can be shared between them.

[0107] On the other hand, when the P-type electrode and the N-type semiconductor layer constituting the semiconductor mesa M (semiconductor stack 20) ​​are close to each other (for example, when only the protective film 60 is present), electrostatic capacitance may be generated between them, resulting in a slower response speed (although it is assumed that the same applies between the N-type electrode and the P-type semiconductor layer, the impact is smaller since the N-type electrode is set as GND). Therefore, by separating the semiconductor mesa M and the protrusions (first protrusion C1 and second protrusion C2), the area where electrodes of different conductivity types and semiconductor layers are close only through the protective film 60 is reduced, resulting in a faster response speed.

[0108] In the above embodiments, the semiconductor mesa M, which includes the light-absorbing layer 24 and the light-absorbing layer 24, was described as containing a compound semiconductor. However, the light-absorbing layer 24 may also be made of a non-compound semiconductor, such as silicon or germanium. Furthermore, the semiconductor mesa M may also be made of a non-compound semiconductor, such as silicon or germanium. Additionally, the semiconductor light-receiving element 1 may not have the first protrusion C1 and the second protrusion C2, and the substrate 10 may not have a recess 10C formed therein.

[0109] Explanation of reference numerals in the attached figures

[0110] 1… Semiconductor light-receiving element, 10… Substrate, 10a… Surface (first surface), 10b… Bottom surface (second surface), 10C… Recess, 10Cs… Inner surface, 24… Light-absorbing layer, 30… Light-receiving part, 40… First electrode, 40p, 50p… Terminal area, 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, wherein, have: A substrate comprising a first surface and a second surface opposite to the first surface; A semiconductor mesa is disposed on the first surface; A lens, which is disposed on the second surface; and The first electrode and the second electrode are disposed on the first surface side and connected to the semiconductor mesa. The semiconductor mesa has: A light-receiving portion that receives incident light from the second surface side via the lens; and A light-absorbing layer, at least a portion of which is included in the light-receiving portion, absorbs the light. The first electrode is connected to a region of a first conductivity type in the semiconductor mesa. The second electrode is connected to a region of the semiconductor mesa with a second conductivity type that is different from the first conductivity type. Viewed from a first direction intersecting the first surface of the substrate, the center of the light-receiving portion is offset relative to the center of the lens along a second direction intersecting the first direction. When viewed from the first direction, the distance from the center of the lens to the center of the light-receiving part along the second direction is greater than the distance from the center of the light-receiving part to the end of the light-receiving part along the second direction.

2. The semiconductor light-receiving element according to claim 1, wherein, It has a protrusion that protrudes from the first surface. The first electrode or the second electrode extends from the connection region with the semiconductor mesa to the top surface of the protrusion opposite to the 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 the connection region with the semiconductor mesa to the first top surface opposite the first surface of the first protrusion. The second electrode extends from the connection region with the semiconductor mesa to the second top surface opposite to the first surface of the second protrusion.

4. The semiconductor light-receiving element according to claim 2 or 3, wherein, The protrusion is composed of a semiconductor stack.

5. The semiconductor light-receiving element according to 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 the 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, When viewed from the first direction, at least a portion of the light-absorbing layer overlaps with the lens.

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

8. The 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 region that serves as a connection terminal to an external device. 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, When viewed from the first direction, the protrusion does not overlap with the lens.

10. The semiconductor light-receiving element according to any one of claims 1 to 9, wherein, A recessed portion is formed in the substrate that is recessed toward the first surface. The second surface is the bottom surface of the recess.

11. The semiconductor light-receiving element according to claim 10, wherein, The inner side of the recess is inclined relative to the first direction in such a way that the recess widens as it moves further away from the bottom surface.

12. The 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 to that end is more than 5 times the distance between one end of the light-receiving part and the other end opposite to that end.

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

14. An optical device, wherein, have: The semiconductor light-receiving element according to any one of claims 1 to 13; and An amplifier that receives the input of the electrical signal generated by the semiconductor photosensitive element. The semiconductor light-receiving element is arranged with its first surface facing the surface of the amplifier, and is electrically connected to the amplifier via connecting members respectively provided on the first electrode and the second electrode.

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