Semiconductor light-receiving device and optical device

Abstract

To provide a semiconductor light-receiving element that can improve sensitivity, and an optical device.SOLUTION: A semiconductor light-receiving element 1 includes a substrate 10, a semiconductor mesa M that is provided on a front surface 10a of the substrate 10, and a lens RL that is provided on a back surface 10r side of the substrate 10. The semiconductor mesa M has a light-receiving part 30 that receives incidence of light L through the lens RL from the back surface 10r side, and a light absorption layer 24 that absorbs the light L. When viewed from a first direction D1 intersecting with the front surface 10a of the substrate 10, a center of the light-receiving part 30 is offset along a second direction D2 intersecting with the first direction D1 with respect to a center of the lens RL. When viewed from the first direction D1, a distance OA from the center of the lens RL to the center of the light-receiving part 30 along the second direction D2 is greater than a distance O1 from the center of the light-receiving part 30 to an end part of the light-receiving part 30 along the second direction D2.SELECTED DRAWING: Figure 4

Description

Technical Field

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

Background Art

[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 to the light incident side, and includes a light absorption layer. The lens is provided on the surface of the n-type semiconductor substrate on the light incident side. The lens is arranged so as to be located directly above the mesa of the light receiving region.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In recent years, in the above technical field, further speeding up of the operating speed exceeding, for example, 50 GHz has been desired. In this case, it is desirable to reduce the thickness of the light absorption layer in order to improve the responsiveness. However, when the light absorption layer is thinned, a decrease in sensitivity may become a problem.

[0005] Therefore, an object of the present invention is to provide a semiconductor light receiving element and an optical device capable of improving sensitivity.

Means for Solving the Problems

[0006] The semiconductor light receiving element according to the present invention includes: [1] 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; a first electrode and a second electrode provided on the first surface side and connected to the semiconductor mesa. The semiconductor mesa has a light receiving portion that receives light incident from the second surface side through the lens, and a light absorption layer at least partially included in the light receiving portion and that absorbs the light. The first electrode is connected to a region of the first conductivity type in the semiconductor mesa, and the second electrode is connected to a region of a second conductivity type different from the first conductivity type in the semiconductor mesa. When viewed from a first direction intersecting the first surface of the substrate, the center of the light receiving portion is offset along a second direction intersecting the first direction with respect to the center of the lens. 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 receiving portion along the second direction to the end of the light receiving portion. It is a "semiconductor light receiving element".

[0007] In this semiconductor light receiving element, a semiconductor mesa including a light receiving portion and a light absorption layer is provided on the first surface of the substrate, and a lens is provided on the second surface opposite to the first surface of the substrate. The light receiving portion receives light incident from the second surface side of the substrate through the lens. Then, when viewed from a first direction intersecting the first surface of the substrate, the center of the light receiving portion is offset along a second direction intersecting the first direction with respect to the center of the lens. For this reason, light is incident obliquely on the light receiving portion and the light absorption layer according to the offset amount (distance between centers) of the lens, and an optical path length can be ensured to be equal to or greater than the thickness of the light absorption layer. In particular, when viewed from the first direction, the offset amount of the lens is made larger than the distance from the center of the light receiving portion to the end of the light receiving portion. Therefore, a longer optical path length can be ensured in the light absorption layer, and the sensitivity can be improved.

[0008] The semiconductor light-receiving element according to the present invention may be the one described in [2], "comprising a protruding portion protruding from the first surface, wherein the first electrode or the second electrode extends from the connection region with the semiconductor mesa to the top surface on the side opposite to the first surface of the protruding portion" as described in [1] above. In this case, by arranging the semiconductor light-receiving element with the first surface side of the substrate facing the external device and using the region on the top surface of the protruding portion of the first electrode or the second electrode as a connection terminal with the external device, connection with the external device can be achieved while protecting the semiconductor mesa. Further, when a connection member such as a solder bump is interposed between the connection terminals of the first electrode or the second electrode, the height of the connection member can be suppressed by the height of the protruding portion.

[0009] The semiconductor light-receiving element according to the present invention may be the one described in [3], "wherein the protruding portion includes a first protruding portion and a second protruding portion, the first electrode extends from the connection region with the semiconductor mesa to the first top surface on the side opposite to the first surface of the first protruding portion, and the second electrode extends from the connection region with the semiconductor mesa to the second top surface on the side opposite to the first surface of the second protruding portion" as described in [2] above. In this case, by arranging the semiconductor light-receiving element with the first surface side of the substrate facing the external device and using the regions on the top surfaces of the first protruding portion and the second protruding portion of the first electrode and the second electrode as connection terminals with the external device, connection with the external device can be achieved while protecting the semiconductor mesa. Further, when a connection member such as a solder bump is interposed between the connection terminals of the first electrode and the second electrode, the height of the connection member can be suppressed by the height of the first protruding portion and the second protruding portion.

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

[0011] The semiconductor light receiving element according to the present invention may be the one described in "[5] 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 absorption layer along the second direction to the end of the light absorption layer, the semiconductor light receiving element according to any one of [1] to [4] above". In this case, by more surely ensuring a longer optical path length in the light absorption layer, the sensitivity can be surely improved.

[0012] The semiconductor light receiving element according to the present invention may be the one described in "[6] When viewed from the first direction, at least a part of the light absorption layer overlaps with the lens, the semiconductor light receiving element according to any one of [1] to [5] above". In this case, it is possible to avoid excessive offset of the lens with respect to the light receiving portion. As a result, although the incident angle of light with respect to the light absorption layer is limited, the error due to the thickness of the substrate at the spot position of the incident light becomes small, and it becomes easier to align the center.

[0013] The semiconductor light receiving element according to the present invention may be the one described in "[7] When viewed from the first direction, the entire light absorption layer overlaps with the lens, the semiconductor light receiving element according to any one of [1] to [6] above". In this case, it is surely possible to avoid excessive offset of the lens with respect to the light receiving portion. As a result, although the incident angle of light with respect to the light absorption layer is limited, the error due to the thickness of the substrate at the spot position of the incident light is surely suppressed, and it becomes even easier to align the center.

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

[0015] The semiconductor light-receiving element according to the present invention may be the one described in any of [2] to [4] above, where "when viewed from the first direction, the protruding portion does not overlap with the lens". In this case, when mounting the semiconductor light-receiving element on an external device from the first surface side, it is possible to avoid the adverse effect of the pressure applied to the protruding portion from the second surface side on the lens.

[0016] The semiconductor light-receiving element according to the present invention may be the one described in any of [1] to [9] above, where "a concave portion that is recessed on the first surface side is formed in the substrate, and the second surface is the bottom surface of the concave portion". In this case, the lens will be provided on the bottom surface of the concave portion. As a result, it is possible to prevent the surface of the lens from being scratched or foreign matter from adhering.

[0017] The semiconductor light-receiving element according to the present invention may be the one described in

[10] above, where "the inner surface of the concave portion is inclined with respect to the first direction such that the concave portion expands as it moves away from the bottom surface". In this case, the wall portion of the concave portion (the portion having the inner surface) is less likely to interfere with the light obliquely incident on the lens. Therefore, it is possible to increase the effective area of the lens.

[0018] The semiconductor light-receiving element according to the present invention may be the one described in any of [1] to

[11] above, where "when viewed from the first direction, the distance between one end of the lens and the other end on the opposite side of the one end is 5 times or more the distance between one end of the light-receiving portion and the other end on the opposite side of 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 invention may be the one described in any of [1] to

[12] above, where "the thickness of the light absorption layer is 1.2 μm or less". In this case, high-speed reading becomes possible (high-speed operation is achieved).

[0020] The optical device according to the present invention is an "optical device comprising a semiconductor light receiving element described in 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 such that the first surface faces the surface of the amplifier, and is electrically connected to the amplifier via connection members provided on each of the first electrode and the second electrode."

[0021] This optical device includes the above-described semiconductor light receiving element. Therefore, the sensitivity can be improved. Further, 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 connection members provided on each of the first electrode and the second electrode. That is, the semiconductor light receiving element is directly provided to the amplifier by the first electrode and the second electrode on the first surface side and the connection member (for example, solder bump). As a result, for example, compared with the case where the semiconductor light receiving element is mounted on a submount and the submount and the amplifier are connected by a wire, the inductance of the submount and the wire can be excluded from the inductance between the semiconductor light receiving element and the amplifier. Therefore, by adjusting the inductance of the wiring in the semiconductor light receiving element, it is possible to realize an optical device with less inductance variation.

Advantages of the Invention

[0022] According to the present invention, it is possible to provide a semiconductor light receiving element and an optical device capable of improving sensitivity.

Brief Description of the Drawings

[0023]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

[0024] Hereinafter, an embodiment of a semiconductor light receiving element and an optical device according to the present invention will be described in detail with reference to the drawings. In each figure, the same or corresponding elements are denoted by the same reference numerals, and redundant descriptions may be omitted. In addition, each figure may show a rectangular 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 an embodiment. As shown in FIG. 1, the optical device 100 includes a semiconductor light receiving element 1. The optical device 100 can be, for example, for light L in a wavelength band for optical communication 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 be for converting the light into an electrical signal and outputting it.

[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 greater than 1.565 μm and 1.625 μm or less. Further, the light L in the wavelength band for communication is light having a peak within the wavelength range of any of the above wavelength bands (that is, 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 targeted at the above wavelength band, and may be configured to receive the incidence of light L having a wavelength belonging to at least one wavelength band in the wavelength band and generate an electrical signal in response to the incident light. The semiconductor light receiving element 1 is mounted on a transimpedance amplifier A (amplifier, external device) via connection members A3 and A4 such as solder bumps, for example.

[0028] More specifically, in the semiconductor light receiving element 1, 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 are arranged so as to face the electrode pads A1 and A2 of the transimpedance amplifier A, respectively. In that 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. Thus, in the present 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 condensed by a lens RL formed on a substrate 10 (see FIGS. 3, 4, etc.) of the semiconductor light receiving element 1 toward a light receiving portion 30 formed in a semiconductor stacked portion 20 (see FIGS. 3, 4, etc.) of the semiconductor light receiving element 1. That is, in the present embodiment, the semiconductor light receiving element 1 is configured as a back surface incident type element that receives the incidence of light L from the substrate 10 side toward the semiconductor stacked portion 20. More specifically, the semiconductor light receiving element 1 receives the incidence of light L from the back surface 10r side described later, and the light L is guided from the substrate 10 side to the semiconductor stacked portion 20.

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

[0031] Figure 2 is a schematic plan view of the semiconductor light receiving element shown in Figure 1. Figure 3 is a schematic cross-sectional view taken along line III-III of Figure 2. As shown in Figures 2 and 3, the semiconductor light receiving element 1 includes a substrate 10, a semiconductor stacked portion 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 on the opposite side of the front surface 10a. The 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, region RB, and region 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 central region RB1 and regions RB2 located on both sides of the region RB1 (the region RA, RC sides).

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

[0034] The semiconductor stack 20 is formed on the substrate 10. More specifically, the semiconductor stack 20 is formed on the surface 10a in the 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 side opposite to the substrate 10. The semiconductor stack 20 includes a buffer layer 21, a buffer layer 22, a capacitance reduction layer 23, an optical absorption layer 24, a cap layer 25, and a contact layer 26 laminated in order from the substrate 10 side. Here, the back surface 20b of the semiconductor stack 20 is the surface on the side opposite to the optical absorption layer 24 in the buffer layer 21 and is in contact with the surface 10a of the substrate 10. Further, the surface 20a of the semiconductor stack 20 is the surface on the side opposite to the optical absorption layer 24 in the contact layer 26.

[0035] The buffer layer 21 has a first conductivity type (here, N-type, and as an example, N + -type). The buffer layer 21 is provided so as to overlap with the region RB2 centering on the region RB1. The layers other than the buffer layer 21 in the semiconductor stack 20 (the buffer layer 22, the capacitance reduction layer 23, the optical absorption layer 24, the cap layer 25, and the contact layer 26) are provided on the region overlapping with the 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 in the semiconductor stack 20 and the protective film 60 described later, and the semiconductor stack 20 constitutes 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 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, is made of N + -InP.

[0036] The buffer layer 22 has a first conductivity type (here, N-type, and as an example, N + -type). The buffer layer 22 contains, for example, InP or InGaAsP and, as an example, is N + -InP or N +It is made of InGaAsP. 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 the buffer layer 22 is higher than that of the capacitance reduction layer 23 described later. As an example, the carrier concentration of the buffer layer 22 is 5×10 16 cm -3 or more and 5×10 18 cm -3 or less. The thickness of the buffer layer 22 is, for example, 0.5 μm or more and 2.5 μm or less.

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

[0039] The capacitance reduction layer 23 has the first conductivity type (here N-type, and as an example N - -type). The capacitance reduction layer 23 includes, for example, any one of InP, InGaAsP, InAsP, and AlInGaAs. As an example, it is made of any one of N - -InP, N - -InGaAsP, N - -InAsP, and N - -AlInGaAs. 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.

[0040] The light absorption layer 24 has the first conductivity type (here N-type, and as an example N - -type). Here, the light absorption layer 24 is N - -In x Ga 1-xIt consists of As. The In composition x of the light absorption layer 24 may be 0.55 or more (and less than 1). In this case, as an example, the In composition x is 0.59. Also, the thickness of the light absorption layer 24 (the thickness along the stacking direction of the semiconductor stacked portion 20) is 0.3 μm or more and 1.2 μm or less, desirably 1.0 μm or less, and more desirably 0.75 μm or less. Here, the thickness of the light absorption layer 24 is, as an example, 0.7 μm. Note that the light absorption layer 24 may contain Al, P, Sb, N, and other materials within a range where the bandgap is, for example, 0.72 eV or less (for example, it may be an absorption layer of a mixed crystal of InGaAs and the said material). In this case, as an example, the light absorption layer 24 may consist of InGaAsP, AlGaInAs, InGaAsSb, or InGaAsN. The ratio of Al, P, Sb, and N (or other materials) mixed in InGaAs can be, for example, 5% or less, or 10% or less.

[0041] Here, the carrier reduction layer 23 has a carrier concentration higher than that of the light absorption layer 24. As an example, the carrier concentration of the carrier reduction layer 23 is 1.5×10 14 cm -3 or more and 3×10 16 cm -3 and the impurity concentration of the light absorption layer 24 is 1×10 14 cm -3 or more and 6×10 15 cm -3 or less. Also, the carrier reduction layer 23 has a bandgap larger than that of the light absorption layer 24. When the bandgap of the light absorption layer 24 is 0.72 eV or less as described above, the bandgap of the carrier reduction layer 23 can be larger than 0.72 eV and in the range of 1.35 eV or less.

[0042] As the capacitance reduction layer 23, it is required that the carrier concentration is higher than that of the light absorption layer 24 as described above and that it is depleted when a bias is applied. The reason is that, as described above, since the capacitance reduction layer 23 has a larger bandgap than the light absorption layer 24, when the carrier concentration is low, a barrier is formed in the conduction band, and there is a risk that the movement of carriers with a large barrier is inhibited and they cannot be suitably extracted.

[0043] In addition, as the capacitance reduction layer 23, since it is necessary to be depleted when a bias is applied, the upper limit of its carrier concentration is 6.0×10 15 cm -3 as described above, which is preferably the case. Furthermore, as the capacitance reduction layer 23, it is desirable that the composition does not absorb incident light (that is, the bandgap is wider than that of the light absorption layer 24). This is because if the capacitance reduction layer 23 absorbs incident light, carriers are generated in the capacitance reduction layer 23. Since the carriers are taken out as a signal from the capacitance reduction layer 23 through the light absorption layer 24, they become slow carriers, which may deteriorate the responsiveness characteristics. As an example, the sensitivity wavelength range of the capacitance reduction layer 23 can be 1.31 μm or less.

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

[0045] In the semiconductor light receiving element 1, the light absorption layer 24 is a single layer. The fact that the light absorption layer 24 is a single layer means that the light absorption layer 24 does not have a stacked structure in which two or more layers having different compositions or characteristics are stacked. More specifically, the fact that the light absorption layer 24 is a single layer means that, for example, it does not have a superlattice structure formed by repeatedly stacking a plurality of layers having different compositions.

[0046] The cap layer 25 has a first conductivity type (here, N-type, and as an example, N -It has a (type). The cap layer 25 contains, for example, InP or InGaAsP. As an example, the cap layer 25 is made of N - -InP or N - -InGaAsP. The carrier concentration of the cap layer 25 is, for example, 1×10 14 cm -3 or more and 1×10 16 cm -3 or less. The thickness of the cap layer 25 is, for example, 0.1 μm or more and 0.5 μm or less.

[0047] The contact layer 26 has a first conductivity type (here it is an N-type, and as an example, N - -type). The contact layer 26 contains, for example, InGaAs, and as an example, it is made of N - -InGaAs. The carrier concentration of the contact layer 26 is, for example, 1×10 14 cm -3 or more and 1×10 16 cm -3 or less. The thickness of the contact layer 26 is, for example, 0.1 μm or more and 0.2 μm or less.

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

[0049] Here, the second region 27 (i.e., the light-receiving portion 30) is formed in a part (for example, a part including the center) in the width direction of the semiconductor mesa M (the direction intersecting the first direction D1). 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. Also, a part on the center side of the light absorption layer 24 is included in the light-receiving portion 30.

[0050] Note that the second region 27 may extend inside the light absorption layer 24. In this case, the light absorption layer 24 includes a fifth region 27a of the second conductivity type that is an extending portion of the second region 27 and a first region 24a of the first conductivity type other than the fifth region 27a. In this case, assuming that the thickness of the light absorption 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 absorption layer 24. That is, in this example, inside the light absorption layer 24, a first region 24a having a thickness of about 0.5 μm and a fifth region 27a having a thickness of 0.2 μm are included, and a boundary therebetween is formed. When the fifth region 27a is of the P + type, its end is, as an example, a position where the P-type carrier concentration is 1×10 17 cm -3 or less.

[0051] On the other hand, when the second region 27 does not reach inside the light absorption layer 24, the entire light absorption layer 24 becomes a first region 24a of the first conductivity type. In this embodiment, the N + type means that the N-type carrier concentration is 1×10 17 cm -3 or more. The N - type means that the N-type carrier concentration is 3.0×10 16 cm -3 or less and is relatively low compared to the N+ type. Also, the P + type means that the P-type carrier concentration is 1×10 17 cm -3 or more.

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

[0053] In other words, the second electrode 50 is connected to the second conductivity type region (second region 27) in the semiconductor mesa M. On the other hand, the first electrode 40 is connected to the first conductivity type portion 21p (the portion of the buffer layer 21 exposed from the protective film 60) of the semiconductor stack portion 20 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 of FIG. 2. The orthogonal 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 along line IV-IV of FIG. 2. Further, in FIG. 4, in the cross-section along the portion inclined with respect to the second direction D2 of line IV-IV of FIG. 2, illustration of the lens and the recess, and partial omission of the first electrode 40 are made.

[0055] As shown in FIGS. 2 and 4, the semiconductor light receiving element 1 has a protruding portion. More specifically, the semiconductor light receiving element 1 includes a first protruding portion C1 and a second protruding portion C2 as the protruding portions. The first protruding portion C1 and the second protruding portion C2 project from the surface 10a of the substrate 10. In the present embodiment, the first protruding portion C1 and the second protruding portion C2 (i.e., the protruding portions) are composed of a semiconductor laminate. More specifically, the first protruding portion C1 and the second protruding portion C2 are composed of semiconductor layers similar to the semiconductor laminated portion 20. That is, the first protruding portion C1 and the second protruding portion C2 are semiconductor mesas including a compound semiconductor. The first protruding portion C1 and the second protruding portion C2 are covered with a protective film 60.

[0056] The first electrode 40 extends from the connection region (portion 21p) with the semiconductor laminated portion 20 (i.e., the semiconductor mesa M) to the first top surface C1s on the side opposite to the surface 10a of the first protruding portion 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 the connection region (second region 27) with the semiconductor laminated portion 20 (i.e., the semiconductor mesa M) to the second top surface C2s on the side opposite to the surface 10a of the second protruding portion 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] As described above, in the optical device 100, the semiconductor light-receiving element 1 is arranged such that the surface 10a 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. 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 on the side opposite to the surface 10a of the protruding portion.

[0059] As shown in FIG. 2, the semiconductor light-receiving element 1 includes a pair of first protruding portions C1 arranged so as to sandwich the second protruding portion C2 along the third direction D3. Only one of the first protruding portions C1 is shown in FIG. 4. The first electrode 40 extends from one of the first protruding portions C1 to the other first protruding portion C1 via a connection region (portion 21p) with the semiconductor mesa M. Terminal regions 40p are formed on the first top surfaces C1s of the pair of first protruding portions C1, respectively.

[0060] Further, the semiconductor light-receiving element 1 includes a pair of third protruding portions C3 arranged along the third direction D3. The third protruding portion C3 projects from the surface 10a of the substrate 10. The third protruding portion C3 can be, for example, a semiconductor laminate including a semiconductor layer similar to the semiconductor laminate portion 20. In this case, the third protruding portion C3 is a semiconductor mesa including a compound semiconductor. Electrodes Md are formed on the top surfaces of the pair of third protruding portions C3 on the side opposite to the surface 10a of the substrate 10. The electrodes Md are 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 are regarded as dummies (dummy electrodes, dummy pads). The semiconductor light-receiving element 1 is formed in a rectangular shape when viewed from the first direction D1, and the above-described pair of first protruding portions C1 and the pair of third protruding portions C3 are arranged at the four corners of the semiconductor light-receiving element 1. As described above, in the semiconductor light-receiving element 1, by providing the dummy third protruding portion C3, the connection regions with the transimpedance amplifier A are four or more, and stabilization during flip-chip bonding is achieved.

[0061] Here, as shown in FIG. 4, 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 along the second direction D2 with respect to the center of the lens RL (the third direction D3 is the same). 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 larger 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. Thereby, the light-receiving portion 30 receives light L obliquely with respect to the first direction D1 from the back surface 10r side through the lens RL. Further, the light absorption layer 24 absorbs the light L incident obliquely with respect to the thickness direction (the first direction D1) of the light absorption layer 24.

[0062] The second electrode 50 extends from the connection region (the second region 27) with the semiconductor mesa M in the direction opposite to the offset direction of the light-receiving portion 30 with respect to the lens RL (here, the negative direction of the second direction D2), that is, in the positive direction of the second direction D2, and reaches the second top surface C2s of the second protrusion C2 to form the 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 portion 30 with respect to the lens RL.

[0063] In the present embodiment, in the second direction D2, the light absorption layer 24 is larger than the light-receiving portion 30, but the distance OA is made even larger than the distance O2 from the center to the end of the light absorption layer 24. On the other hand, in the present embodiment, when viewed from the first direction D1, a part of the light absorption layer 24 (and further the light-receiving portion 30) overlaps the lens RL. Also, in the present 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 the lens RL, and further, the first protrusion C1 and the second protrusion C2 do not overlap the lens RL, respectively.

[0064] Note that the centers of the light receiving portion 30, the light absorption layer 24, and the lens RL each include the case where they are the respective centers of gravity. Also, when viewed from the first direction D1, for example, with respect to the second direction D2, the distance TL between one end of the lens RL and the other end on the opposite side of 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 on the opposite side of the one end.

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

[0066] As described above, in the semiconductor light receiving element 1 according to the present embodiment, a semiconductor mesa M including a light receiving portion 30 and a light absorption 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 the incidence of light L incident from the back surface 10r side of the substrate 10 through the lens RL. Then, when viewed from the first direction D1, the center of the light receiving portion 30 is offset along the second direction D2 with respect to the center of the lens RL. For this reason, light L is incident obliquely on the light absorption layer 24 according to the offset amount (distance OA between the centers) of the lens RL, and an optical path length can be ensured that is equal to or greater than the thickness of the light absorption layer 24. In particular, when viewed from the first direction D1, the offset amount of the lens RL is made larger 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 can be ensured in the light absorption layer 24, and the sensitivity can be improved.

[0067] In addition, the semiconductor light receiving element 1 according to the present embodiment includes a first protruding portion C1 and a second protruding portion C2 (i.e., protruding portions) protruding from the surface 10a of the substrate 10. The first electrode 40 extends from the connection region (portion 21p) with the semiconductor mesa M to the first top surface C1s of the first protruding portion 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 protruding portion 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 regions on the top surfaces of the first protruding portion C1 and the second protruding portion C2 of the first electrode 40 and the second electrode 50 as connection terminals with the transimpedance amplifier A, it is possible to connect to the transimpedance amplifier A while protecting the semiconductor mesa M. Further, when connection members A3 and 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 connection members A3 and A4 can be suppressed by the height of the first protruding portion C1 and the second protruding portion C2.

[0068] In addition, in the semiconductor light receiving element 1 according to the present embodiment, the first protruding portion C1 and the second protruding portion C2 (i.e., protruding portions) are made of a semiconductor laminate. Therefore, the first protruding portion C1 and the second protruding portion C2 can be provided by a semiconductor manufacturing process.

[0069] In addition, in the semiconductor light receiving element 1 according to the present embodiment, 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 larger than the distance O2 from the center of the light absorption layer 24 along the second direction D2 to the end of the light absorption layer 24. Therefore, by more surely ensuring the optical path length in the light absorption layer 24, the sensitivity can be surely improved.

[0070] Also, in the semiconductor light receiving element 1 according to the present embodiment, as viewed from the first direction D1, a part of the light absorption layer 24 overlaps with the lens RL. Therefore, it is possible to avoid excessive offset of the lens RL with respect to the light receiving portion 30. As a result, although the incident angle of the light L with respect to the light absorption layer 24 is limited, the error due to the thickness of the substrate 10 of the spot position of the incident light is reduced, and it becomes easier to align the center.

[0071] In the semiconductor light receiving element 1 according to the present 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. And, as viewed from the first direction D1, the terminal regions 40p and 50p do not overlap with the lens RL. Therefore, when mounting the semiconductor light receiving element 1 on the transimpedance amplifier A from the surface 10a side, it is possible to avoid the adverse effect of the pressure applied to the terminal regions 40p and 50p of the first electrode 40 and the second electrode 50 from the back surface 10r side on the lens RL.

[0072] Also, in the semiconductor light receiving element 1 according to the present embodiment, as viewed from the first direction D1, the first protruding portion C1 and the second protruding portion C2 (i.e., the protruding portions) do not overlap with the lens RL. Therefore, when mounting the semiconductor light receiving element 1 on the transimpedance amplifier A from the surface 10a side, it is possible to avoid the adverse effect of the pressure applied to the first protruding portion C1 and the second protruding portion C2 from the back surface 10r side on the lens RL.

[0073] Also, in the semiconductor light receiving element 1 according to the present embodiment, a concave portion 10C that is recessed on the surface 10a side is formed in the substrate 10, and the lens RL is provided on the bottom surface 10b of the concave portion 10C of the back surface 10r of the substrate 10. Therefore, it is possible to prevent the surface of the lens RL from being scratched or foreign matter from adhering.

[0074] In the semiconductor light receiving element 1 according to the present embodiment, the inner surface 10Cs of the recess 10C is inclined with respect to the first direction D1 such that the recess 10C expands as it moves 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 that obliquely enters the lens RL. For this reason, it becomes possible to increase the effective area of the lens RL.

[0075] In the semiconductor light receiving element 1 according to the present embodiment, when viewed from the first direction D1, the distance TL between one end of the lens RL and the other end on the opposite side of the one end may be 5 times or more the distance T1 between one end of the light receiving portion 30 and the other end on the opposite side of 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 the present embodiment, the thickness of the light absorption layer 24 may be 1.2 μm or less. In this case, high-speed reading becomes possible (high speed is achieved).

[0077] Furthermore, the optical device 100 according to the present embodiment includes the semiconductor light receiving element 1 and a transimpedance amplifier A that receives the input of the electrical signal generated by the semiconductor light receiving element 1. 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.

[0078] This optical device 100 includes the above-described semiconductor light-receiving element 1. Therefore, the sensitivity can be improved. Further, 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 connection members A3 and A4 provided on each of the first electrode 40 and the second electrode 50. That is, the semiconductor light-receiving element 1 is directly provided on the transimpedance amplifier A by the first electrode 40 and the second electrode 50 on the surface 10a and the connection members A3 and A4 (for example, solder bumps). As a result, compared with the case where the semiconductor light-receiving element 1 is mounted on a submount and the submount and the transimpedance amplifier A are connected by wires, the inductance of the submount and the 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 in the semiconductor light-receiving element 1, it is possible to realize an optical device 100 with less inductance variation.

[0079] The above embodiments have described one aspect of the semiconductor light-receiving element and the optical device according to the present invention. Therefore, the semiconductor light-receiving element and the optical device according to the present invention are not limited to the above embodiments and can be arbitrarily modified. Subsequently, modification examples will be described.

[0080] FIG. 5 is a schematic cross-sectional view showing a semiconductor light-receiving element according to a modification example. The cross-section of FIG. 5 corresponds to the cross-section along line III-III of FIG. 2. In the example shown in FIG. 5, the entire second semiconductor layer S2 (that is, the cap layer 25 and the contact layer 26) is a second region 27 of the second conductivity type (here, P-type, and P+ type as an example). That is, the second semiconductor layer S2 consists 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 inside the light absorption layer 24. However, in this case, the second region 27 may include another light absorption layer 27b of the second conductivity type (here P-type, for example P+ type) laminated on the light absorption layer 24. The light absorption layer 27b is located on the side opposite to the capacitance reduction layer 23 with respect to the light absorption layer 24. In this case, the entire light absorption layer 24 becomes the first region 24a of the first conductivity type. The light absorption layer 27b can be composed of the same material as the above-described material of the light absorption layer 24, but includes, for example, InGaAs and consists of P+-InGaAs as an example.

[0082] The thickness of the light absorption layer 27b may 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 the response speed can be achieved. Also, in the example shown in FIG. 5, contact with the second electrode 50 is made in the contact layer 26, but by providing the light absorption layer 27b of the second conductivity type, it is also possible to make contact with the second electrode 50 in this light absorption 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 a direction intersecting the first direction D1. In other words, the entire light absorption layer 24 is included in the light receiving portion 30. Therefore, in the example shown in FIG. 5, in the direction intersecting the first direction D1, the width of the light receiving portion 30 coincides with the width of the light absorption layer 24. Also in the example shown in FIG. 5, the light receiving portion 30 and the lens RL are offset along the second direction D2. In this case, however, the distance O1 from the center to the end of the light receiving portion 30 along the second direction D2 and the distance O2 from the center to the end of the light absorption layer 24 along the second direction D2 are the same as each other. Therefore, in this case, when viewed from the first direction D1, a part of the light receiving portion 30 overlapping the lens RL is synonymous with a part of the light absorption layer 24 overlapping the lens RL.

[0084] FIG. 6 is a cross-sectional view showing a semiconductor light-receiving element according to another modified example. The cross-section of FIG. 6 corresponds to the cross-section along line III-III in FIG. 2. In the example shown in FIG. 6, buffer layer 21 and buffer layer 22 have a second conductivity type (here, P-type, for example, P + -type). Buffer layer 21 contains, for example, InP and, as an example, consists of P + -InP. Buffer layer 22 contains, for example, InP or InGaAsP and, as an example, consists of P + -InP or P + -InGaAsP.

[0085] Also, in the example shown in FIG. 6, cap layer 25 and contact layer 26 have a first conductivity type (here, N-type, for example, N + -type). Cap layer 25 contains, for example, InP or InGaAsP. As an example, cap layer 25 consists of N + -InP or N + -InGaAsP. Contact layer 26 contains, for example, InGaAs and, as an example, consists of N + -InGaAs. The conductivity types of capacitance reduction layer 23 and light absorption layer 24 are the same as those in the above embodiment.

[0086] Thus, in the example shown in FIG. 6, the first semiconductor layer S1 has a second conductivity type, and the second semiconductor layer S2 has a first conductivity type. And capacitance reduction layer 23 is located between 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 light absorption layer 24.

[0087] Thus, the capacitance reduction 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 absorption layer 24. Further, the other semiconductor layer 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 conductivity type second region 27 that forms a PN junction with the light absorption layer 24 (the first region 24a).

[0088] In the example of FIG. 6, the buffer layer 22 includes a first layer 22a provided across the regions RB1 to RB2 of the substrate 10 and a second layer 22b formed on the region RB1 and not reaching the 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 the portion 22p.

[0089] As described above, also in the example shown in FIG. 6, 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 absorption layer 24 is included in the light receiving portion 30. Therefore, in the example shown in FIG. 6, similar to the example shown in FIG. 5, in the direction intersecting the first direction D1, the width of the light receiving portion 30 coincides with the widths of the light absorption layers 24 and 27b. Also in the example shown in FIG. 6, the light receiving portion 30 and the lens RL are offset along the second direction D2. In this case, however, the distance O1 from the center to the end of the light receiving portion 30 along the second direction D2 and the distance O2 from the center to the end of the light absorption layer 24 along the second direction D2 are the same as each other. Therefore, in this case, when viewed from the first direction D1, a part of the light receiving portion 30 overlapping the lens RL is synonymous with a part of the light absorption layer 24 overlapping the lens RL.

[0090] Next, other modifications will be described. In the semiconductor light receiving element 1 according to the above embodiment, the case where a part of the light absorption layer 24 overlaps with the lens RL as viewed from the first direction D1 has been exemplified. However, in the semiconductor light receiving element 1, the entire light absorption layer 24 may overlap with the lens RL as viewed from the first direction D1. In this case, it is surely possible to avoid excessive offset of the lens RL with respect to the light receiving portion 30. As a result, although the incident angle of the light L with respect to the light absorption layer 24 is limited, an error due to the thickness of the substrate 10 of the spot position of the incident light is surely suppressed, and it becomes easier to align the center.

[0091] Further, in the semiconductor light receiving element 1 according to the above embodiment, the case where the centers of the light receiving portion 30 and the light absorption layer 24 are offset in the second direction D2 with respect to the center of the lens RL and coincide in the third direction D3 has been exemplified. However, the centers of the light receiving portion 30 and the light absorption layer 24 may be offset not only in the second direction D2 but also in the third direction D3 with respect to the center of the lens RL. In that 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 larger than the shortest distance among the distances from the center of the light receiving portion 30 to the end of the light receiving portion 30 in any direction, or may be set to be larger 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 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 absorption 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 among the distances from the center of the light absorption layer 24 to the end of the light absorption 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 absorption layer 24 to the end of the light absorption layer 24 in the second direction D2 and the distance from the center of the light absorption layer 24 to the end of the light absorption layer 24 in the third direction D3.

[0093] In the above-described embodiment, the case where the first protruding portion C1 and the second protruding portion C2 (and further the third protruding portion C3 (the same shall apply hereinafter)) are made of a semiconductor laminate has been exemplified. However, the first protruding portion C1 and the second protruding portion C2 may have other structures. For example, the first protruding portion C1 and the second protruding portion C2 may be formed of metal or an insulator. When the first protruding portion C1 and the second protruding portion C are formed of metal, each of the first electrode 40 and the second electrode 50 can be configured to be partially thick, thereby forming the first protruding portion C1 and the second protruding portion C2. Alternatively, when the first protruding portion C1 and the second protruding portion C2 are formed of an insulator, the first protruding portion C1 and the second protruding portion C2 can be formed by partially thickening an insulating film such as the protective film 60.

[0094] Also, when the first protruding portion C1 and the second protruding portion C2 are formed of a semiconductor laminate, the first protruding portion C1 and the second protruding portion C2 may be formed by leaving the portions corresponding to the first protruding portion C1 and the second protruding portion C2 of the semiconductor layer unetched during the etching of the semiconductor layer for forming the semiconductor mesa M. Alternatively, after the etching for forming the semiconductor mesa M, the first protruding portion C1 and the second protruding portion C2 may be formed by separately laminating a semiconductor layer on the surface 10a of the substrate 10.

[0095] Also, the semiconductor mesa M, the first protruding portion C1, and the second protruding portion C2 are not limited to the case where they are completely independently formed by forming grooves reaching the surface 10a of the substrate 10 between them. For example, the semiconductor mesa M, the first protruding portion C1, and the second protruding portion C2 may be configured to be embedded while being insulated from each other.

[0096] Alternatively, the first protrusion C1 and the second protrusion C2 may be formed as one mesa, or the first protrusion C1 and the second protrusion C2 may be configured as separate mesas while a part of the semiconductor layer closer to the substrate 10 is shared between them. Further, the semiconductor mesa M (i.e., the semiconductor stacked portion 20) and the first protrusion C1 and / or the second protrusion C2 may be formed as one mesa, or the semiconductor mesa M and the first protrusion C1 and / or the second protrusion C2 may be configured as separate mesas while a part of the semiconductor layer closer to the substrate 10 is shared between them.

[0097] On the other hand, when an electrode connected to the P-type and the N-type semiconductor layer constituting the semiconductor mesa M (semiconductor stacked portion 20) are close to each other (for example, when only the protective film 60 is interposed), there is a possibility that a capacitance is generated between them and the response speed becomes slow (although the same is considered to be the case between the N-type electrode and the P-type semiconductor layer, the influence of the N-type electrode is small because it is grounded). Therefore, by separating the semiconductor mesa M and the protrusions (the first protrusion C1 and the second protrusion C2), the area where the electrodes of different conductivity types and the semiconductor layer are close to each other only through the protective film 60 is reduced, and an effect of increasing the response speed can be obtained.

[0098] In the above embodiment, the case where the light absorption layer 24 and the semiconductor mesa M including the light absorption layer 24 contain a compound semiconductor has been described. However, the light absorption layer 24 may be composed of a semiconductor that is not a compound such as silicon or germanium. Also, the semiconductor mesa M may be composed of a semiconductor that is not a compound such as silicon or germanium. Further, the semiconductor light receiving element 1 may not include the first protrusion C1 and the second protrusion C2, or the recess 10C may not be formed in the substrate 10.

Description of Reference Numerals

[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 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; A first electrode and a second electrode provided on the first surface side and connected to the semiconductor mesa; Comprising: The semiconductor mesa: A light receiving portion that receives light incident through the lens from the second surface side; A light absorption layer at least partially included in the light receiving portion and absorbing the light; Having: The first electrode is connected to a region of the first conductivity type in the semiconductor mesa; The second electrode is connected to a region of a second conductivity type different from the first conductivity type in the semiconductor mesa; When viewed from a first direction intersecting the first surface of the substrate, the center of the light receiving portion is offset along a second direction intersecting the first direction with respect to the center of the lens; 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 receiving portion along the second direction to the end of the light receiving portion; A semiconductor light receiving element.

2. Comprising a protruding portion protruding from the first surface; The first electrode or the second electrode extends from a connection region with the semiconductor mesa to the top surface on the side opposite to the first surface of the protruding portion; The semiconductor light receiving element according to Claim 1.

3. The protruding portion includes a first protruding portion and a second protruding portion; The first electrode extends from a connection region with the semiconductor mesa to the first top surface on the side opposite to the first surface of the first protruding portion; The second electrode extends from a connection region with the semiconductor mesa to the second top surface on the side opposite to the first surface of the second protruding portion; The semiconductor light receiving element according to Claim 2.

4. The protruding portion is made of a semiconductor laminate; The semiconductor light receiving element according to Claim 2.

5. 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 absorption layer along the second direction to the end of the light absorption layer; The semiconductor light receiving element according to Claim 1.

6. When viewed from the first direction, at least a part of the light absorption layer overlaps the lens; The semiconductor light receiving element according to Claim 1.

7. When viewed from the first direction, the entire light absorption layer overlaps the lens; The semiconductor light receiving element according to Claim 1.

8. The first electrode and the second electrode each have a terminal region that serves as a connection terminal to an external device. When viewed from the first direction, the terminal region does not overlap with the lens. The semiconductor light receiving element according to claim 1.

9. When viewed from the first direction, the protruding portion does not overlap with the lens. The semiconductor light receiving element according to claim 2.

10. A recess that is recessed on the first surface side is formed in the substrate. The second surface is the bottom surface of the recess. The semiconductor light receiving element according to claim 1.

11. The inner surface of the recess is inclined with respect to the first direction such that the recess expands as it moves away from the bottom surface. The semiconductor light receiving element according to claim 10.

12. When viewed from the first direction, the distance between one end of the lens and the other end on the opposite side of the one end is 5 times or more the distance between one end of the light receiving portion and the other end on the opposite side of the one end. The semiconductor light receiving element according to claim 1.

13. The thickness of the light absorption layer is 1.2 μm or less. The semiconductor light receiving element according to claim 1.

14. A semiconductor light receiving element according to any one of claims 1 to 13, an amplifier that receives an input of an electrical signal generated by the semiconductor light receiving element, comprising: The semiconductor light receiving element is arranged such that the first surface faces the surface of the amplifier, and is electrically connected to the amplifier via connection members provided on each of the first electrode and the second electrode. Optical device.

Images