Semiconductor photodetector

Abstract

To ensure the coverage of an insulating film.SOLUTION: A semiconductor photodetector includes a substrate 10, a mesa structure 14 on the substrate 10, which is composed of multiple layers including an upper layer and a lower layer, in which the upper layer is a light absorbing layer 16, and the lower layer is a wide band gap layer 18 with a band gap wide enough not to absorb light, and an insulating film 26 covering the side surface of the mesa structure 14, and each of the multiple layers is composed of a single crystal of a III-V group semiconductor, the upper surface is the (100) plane, and the upper surface of the wide band gap layer 18 is shaped to include a pair of vertices V in the [0-11] direction and the [01-1] direction on the circumference of the smallest inclusive circle C.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a semiconductor light-receiving element. [Background technology]

[0002] As transmission speeds in optical communications increase, optical modules are required to have high-speed response. A semiconductor photodetector with excellent high-speed response has a mesa structure shaped like a truncated cone (Patent Document 1). The mesa structure consists of multiple stacked semiconductor layers and is covered with an insulating film (Patent Document 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-075479 [Patent Document 2] Japanese Patent Publication No. 2022-114411 Summary of the Invention [Problem to be solved by the invention]

[0004] When anisotropic etching is applied to the mesa structure during the formation process, it can take on an inverted truncated cone shape. This results in an inverted tapered side surface, which can reduce the coverage of the insulating film and lead to reduced reliability and performance.

[0005] An object of the present invention is to ensure the coverage of the insulating film. [Means for solving the problem]

[0006] The semiconductor light receiving element comprises a substrate, a mesa structure on the substrate, the mesa structure being made up of a plurality of layers including an upper layer and a lower layer, the upper layer being a light absorbing layer, and the lower layer being a wide band gap layer having a band gap wide enough not to absorb the light, and an insulating film covering a side surface of the mesa structure, wherein each of the plurality of layers is made of a single crystal of a III-V group semiconductor, has an upper surface in the (100) plane, and the upper surface of the wide band gap layer is formed in a plane that least encloses a pair of vertices in the [0-11] direction and the [01-1] direction. Containing A shape that is contained on the circumference of a circle. [Brief explanation of the drawings]

[0007]

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[0008] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Elements with the same reference numerals in all the drawings have the same or equivalent functions, and their repeated explanation will be omitted. Note that the size of the figures does not necessarily correspond to the magnification.

[0009] [First embodiment] Fig. 1 is a plan view of a semiconductor light receiving element according to a first embodiment, Fig. 2 is an enlarged cross-sectional view of the semiconductor light receiving element taken along line II-II of Fig. 1, Fig. 3 is an enlarged cross-sectional view of the semiconductor light receiving element taken along line III-III of Fig. 1.

[0010] The semiconductor photodetector is compatible with wavelength bands used in optical communications, etc. The semiconductor photodetector is a front-illuminated type semiconductor photodetector in which signal light is incident from the front, such as a PIN type photodetector having a structure in which an intrinsic semiconductor layer is inserted between a p-type semiconductor layer and an n-type semiconductor layer, but may also be an avalanche photodiode (APD).

[0011] [substrate] The semiconductor light receiving element has a substrate 10. The substrate 10 is made of a single crystal of a III-V group semiconductor (e.g., InP doped with Fe), and has a (100) plane represented by Miller indices as its upper surface. A first contact layer 12 is provided on the substrate 10. The first contact layer 12 is a semiconductor layer of a first conductivity type (e.g., n-type).

[0012] [Mesa structure] The semiconductor light receiving element has a mesa structure 14 on a substrate 10. Signal light is incident from the top surface of the mesa structure 14. The mesa structure 14 is disposed on the substrate 10 (more specifically, on the first contact layer 12). The mesa structure 14 is in contact with the first contact layer 12 and is electrically connected thereto.

[0013] The mesa structure 14 is composed of multiple layers. Each of the multiple layers is made of a single crystal of a III-V semiconductor and has a (100) plane as its upper surface. The multiple layers include an upper layer and a lower layer. The upper layer is not the uppermost layer, but it may be the uppermost layer.

[0014] [Upper layer] The upper layer of the mesa structure 14 is a light absorption layer 16. The absorption layer 16 is made of InGaAs. Light entering the mesa structure 14 is incident on the absorption layer 16, absorbed, and converted into electricity. The absorption layer 16 converts the signal light into an electrical signal. The absorption layer 16 may be either an intrinsic semiconductor layer or a conductive semiconductor layer, or a combination of the two. An intrinsic semiconductor may be not only a semiconductor with no polarity at all, but also a semiconductor that does not contain any intentional additives to impart polarity, that is, a semiconductor that contains a trace amount of additive at the background level.

[0015] The upper surface of the absorbing layer 16 is formed such that a pair of vertices V in the [0-11] direction and the [01-1] direction (opposite each other along the first direction D1) are enclosed by a minimum envelope. Containing It is a shape that is included on the circumference of circle C. The angle between each of the pair of vertices V is 135 degrees or less. Vertex V includes not only the point where the tips of two straight lines meet, but also the point where two curved lines meet.

[0016] The upper surface of the absorption layer 16 has a pair of tips in the

[0011] direction and the [0-1-1] direction (opposite to each other along a second direction D2 perpendicular to the first direction D1) arranged in a minimum envelope. Containing The shape is included inside the circle C. The upper surface of the absorption layer 16 has a shape including a pair of arcs that are convex in the

[0011] direction and the [0-1-1] direction (second direction D2).

[0017] [Lower layer] The lower layer of the mesa structure 14 is a wide bandgap layer 18, which has a bandgap wide enough not to absorb light. The wide bandgap layer 18 has a wider bandgap than the absorption layer 16, and does not absorb light that has passed through the absorption layer 16 (i.e., incident light). The wide bandgap layer 18 is an intrinsic semiconductor and is made of any of InAlGaAs, InAlAs, and InP.

[0018] The wide band gap layer 18 is thicker than the absorption layer 16. When a voltage is applied, the wide band gap layer 18 and the absorption layer 16 are depleted to form a depletion layer. The presence of the wide band gap layer 18 makes it possible to increase the thickness of the depletion layer, thereby reducing parasitic capacitance and enabling high-speed operation.

[0019] The upper surface of the wide band gap layer 18 is formed by a pair of vertices V in the [0-11] direction and the [01-1] direction (first direction D1) in a minimum enclosing manner. Containing It is a shape that is included on the circumference of circle C. The angle between the pair of vertices V is 135 degrees or less.

[0020] In the process of forming the mesa structure 14, the semiconductor layer is grown as a crystal and then etched through a mask. Because etching is dependent on the crystal orientation, crystal planes appear, and the side surfaces in the first direction D1 become inversely tapered. If the mask has a circular planar shape, the side surfaces become inversely tapered even in a direction slightly deviated from the first direction D1, and the inversely tapered surface becomes wider.

[0021] In this embodiment, the planar shape has a vertex V in the first direction D1, so the side surfaces slightly shifted from the first direction D1 also become forward tapered or vertical surfaces. As a result, the side surfaces in the first direction D1 do not become reverse tapered surfaces, but become vertical or forward tapered surfaces. Even if the vertex V is the intersection of two curves, the side surfaces in the first direction D1 are small, so no reverse tapered surfaces appear.

[0022] The upper surface of the wide band gap layer 18 has a pair of tips in the

[0011] direction and the [0-1-1] direction (second direction D2) that are spaced apart by a minimum envelope.Containing Its shape is included inside circle C. Since the capacitance of a semiconductor light-receiving element is proportional to the area of ​​the depleted layer, reducing the area of ​​mesa structure 14 in plan view suppresses an increase in parasitic capacitance and enables support for high-speed operation.

[0023] The upper surface of wide band gap layer 18 has a shape including a pair of arcs convex in the

[0011] direction and the [0-1-1] direction (second direction D2). The outer shape of the upper surface of wide band gap layer 18 coincides with the lower surface of absorption layer 16.

[0024] Top Layer The uppermost layer of the multiple layers is the second contact layer 20, which is a semiconductor layer (eg, InGaAs layer) of a second conductivity type (eg, p-type) with a wide band gap so as not to absorb incident light.

[0025] The upper surface of the second contact layer 20 is formed by a minimum enclosing pair of vertices V in the [0-11] direction and the [01-1] direction (first direction D1). Containing It is a shape that is included on the circumference of circle C. The angle between the pair of vertices V is 135 degrees or less.

[0026] The upper surface of the second contact layer 20 has a pair of tips in the

[0011] direction and the [0-1-1] direction (second direction D2) that are spaced apart by a minimum envelope. Containing The shape is included inside the circle C. The upper surface of the second contact layer 20 has a shape including a pair of arcs convex in the

[0011] direction and the [0-1-1] direction (second direction D2). The lower surface of the second contact layer 20 coincides with the upper surface of the absorption layer 16 in outline.

[0027] In this embodiment, the multiple layers included in the mesa structure 14 are configured with only the minimum necessary elements, but other layers may also be included. For example, the multiple layers may include an etch stop layer between the first contact layer 12 and the wide band gap layer 18, or an InAlGaAs cap layer between the absorption layer 16 and the second contact layer 20.

[0028] [Convex structure] A first protruding structure 22 is provided above the substrate 10. The first protruding structure 22 is made up of multiple layers and has the same layer structure as the mesa structure 14 except that the bottom layer is the same layer as the first contact layer 12. However, the planar shape is different.

[0029] A second protruding structure 24 is provided above the substrate 10. The second protruding structure 24 has the same layer structure as the first protruding structure 22. The mesa structure 14, the first protruding structure 22, and the second protruding structure 24 can be formed by growing the above-mentioned layer structure using an MBE (Molecular Beam Epitaxy) apparatus and then separating them from each other using lithography techniques.

[0030] [Insulating film] The semiconductor light-receiving element has an insulating film 26 that covers the side surfaces of the mesa structure 14. The insulating film 26 covers and protects the mesa structure 14, the first convex structure 22, the second convex structure 24, and the exposed surfaces (e.g., the entire surfaces) of the substrate 10. The insulating film 26 is a passivation film, and is an oxide film or a nitride film, such as a silicon oxide film or a silicon nitride film. The insulating film 26 is formed on a portion of the upper surface of the first contact layer 12, and a first through-hole 28 is formed therein. The insulating film 26 is not formed on a portion of the upper surface of the mesa structure 14, and thereby a second through-hole 30 is formed therein.

[0031] The insulating film 26 (passivation film) can protect the semiconductor that constitutes the mesa structure 14 and reduce leakage current. In this embodiment, the side surface of the mesa structure 14 is not an inverted tapered surface, so that the insulating film 26 has good coverage, resulting in high reliability and characteristics of the semiconductor light-receiving element.

[0032] [Electrode pattern] The semiconductor light receiving element has an electrode pattern 32. The electrode pattern 32 includes a first electrode 34. The first electrode 34 is disposed on one surface of the substrate 10. A plurality of portions of the first electrode 34 are integral with each other.

[0033] The first electrode 34 includes a mesa electrode 36 on the top surface of the mesa structure 14. The outer shape of the top surface of the mesa electrode 36 is circular, but it may have a shape that follows the shape of the mesa structure 14. The mesa electrode 36 and the second contact layer 20 are connected via a second through hole 30 in the insulating film 26. The mesa electrode 36 contacts (is physically and electrically connected to) the upper surface of the second contact layer 20. The mesa electrode 36 has an opening 38 in plan view. The opening 38 has a shape that allows signal light to be incident thereon. The opening 38 is circular. The mesa electrode 36 is ring-shaped in plan view, but may also be C-shaped with some parts not connected.

[0034] The first electrode 34 includes a first external electrode 40 (e.g., a pad). The first external electrode 40 is disposed so as to cover the upper surface of the first protruding structure 22, and is adapted to be bonded with a wire (not shown) for electrical connection to the outside (e.g., a transimpedance amplifier). The first external electrode 40 is located on the insulating film 26.

[0035] The first electrode 34 includes a first connection electrode 42 that connects the first external electrode 40 and the mesa electrode 36. The width of the first connection electrode 42 perpendicular to the extension direction is narrower than the widths of both the first external electrode 40 and the mesa electrode 36. The first connection electrode 42 extends from the mesa electrode 36 in the

[0011] direction or the [0-1-1] direction (second direction D2). Because the side surface of the mesa structure 14 is a forward tapered surface in this direction, the first connection electrode 42 will not be broken.

[0036] The electrode pattern 32 includes a second electrode 44. The second electrode 44 is disposed on one surface of the substrate 10. Multiple portions of the second electrode 44 are integral. The second electrode 44 includes a pair of second external electrodes 46. The first external electrode 40 is located between the pair of second external electrodes 46. The second external electrode 46 includes a region (e.g., a pad) disposed on the upper surface of the second convex structure 24 and a region on the side surface of the second convex structure 24. The second electrode 44 includes a second connection electrode 48 connecting the pair of second external electrodes 46. The second connection electrode 48 contacts the first contact layer 12 inside the first through hole 28 in the insulating film 26. By applying a voltage between the first electrode 34 and the second electrode 44, light (optical signal) incident on the mesa structure 14 is absorbed, and an electrical signal is obtained.

[0037] [Modification of the first embodiment] 4 is a plan view of a semiconductor light receiving element according to a modification of the first embodiment. The upper surface of the wide band gap layer 18 is formed by a minimum encapsulation of a pair of vertices V′ in the

[0011] direction and the [0-1-1] direction (second direction D2). Containing The shape is included on the circumference of the circle C'. The top surface of the wide band gap layer 18 is polygonal (for example, a regular octagon).

[0038] In this way, the upper surface may have a shape made up of only straight lines. The angle θ of the vertex V' (the angle between the two straight lines) is preferably 135 degrees or less. If the angle is greater than this, the shape of the upper surface will become closer to a circle, and there is a risk of an inverted tapered surface appearing.

[0039] The upper surfaces of the layers above the wide band gap layer 18 (the uppermost layer and the absorption layer 16) are arranged in a minimum enclosing manner with a pair of vertices V' in the [0-11] direction and the [01-1] direction (first direction D1). Containing The shape is included on the circumference of the circle C'. The top surface of the wide band gap layer 18 coincides with the bottom surface of the absorption layer 16 in outline.

[0040] [Second embodiment] Fig. 5 is a plan view of a semiconductor light receiving element according to a second embodiment, Fig. 6 is an enlarged cross-sectional view of the semiconductor light receiving element of Fig. 5 taken along line VI-VI, and Fig. 7 is an enlarged cross-sectional view of the semiconductor light receiving element of Fig. 5 taken along line VII-VII.

[0041] The mesa structure 214 has a two-tier structure including an upper mesa structure 250 and a lower mesa structure 252. The upper mesa structure 250 includes an absorption layer 216 and a second contact layer 220. The lower mesa structure 252 includes a wide bandgap layer 218.

[0042] The upper surface of the upper mesa structure 250 is circular. That is, the upper surfaces of the layers above the wide band gap layer 218 (the uppermost layer and the absorption layer 216) are also circular. Therefore, the side surface of the upper mesa structure 250 includes an inversely tapered surface. The upper surface of the wide band gap layer 218 protrudes from the absorption layer 216.

[0043] The capacitance of a semiconductor light-receiving element is proportional to the area of ​​the depletion layer, and the beam shape of incident light is generally circular. Therefore, to ensure light-receiving efficiency while avoiding the addition of excess capacitance, the area of ​​the depletion layer should be circular. The depletion layers are the absorption layer 216 and the wide bandgap layer 218, which are included in the upper mesa structure 250 and the lower mesa structure 252, respectively.

[0044] However, if the top surfaces of both the upper mesa structure 250 and the lower mesa structure 252 are circular, both side surfaces will have inverse tapered surfaces, which will have a significant impact on the coverage of the insulating film 226. The first embodiment solves this problem, but the top surfaces will be larger than the beam shape of the incident light, which is disadvantageous in terms of capacitance.

[0045] Therefore, in this embodiment, the upper surface of the lower mesa structure 252 has the same shape as the upper surface of the wide band gap layer 218 of the first embodiment, while the upper surface of the upper mesa structure 250 is circular to suppress an increase in capacitance. As a result, although an inversely tapered surface appears, an inversely tapered surface does not appear on the side surface of the lower mesa structure 252, thereby reducing the possibility of a decrease in coverage of the insulating film 226.

[0046] Wide band gap layer 218 is a layer disposed to reduce capacitance, and tends to be thicker than other layers (e.g., absorption layer 216). If the side surface of a thick layer becomes an inversely tapered surface, the coverage of insulating film 226 is significantly reduced, so the upper surface of lower mesa structure 252 including wide band gap layer 218 is not circular.

[0047] The thickness of the depletion layer is limited by the impurity concentration, and the lower the impurity concentration, the thicker the depletion layer becomes. In other words, if a certain impurity concentration is contained, the thickness of the depletion layer is effectively limited no matter how thick the layer is formed.

[0048] Since the impurity concentration can be lower in InP than in InAlGaAs, a layer formed of InP can effectively have a thicker depletion layer than a layer formed of InAlGaAs. Therefore, if the wide band gap layer 218 is formed thick using InP, the depleted region can be correspondingly widened. If a thick wide band gap layer 218 is formed, the reverse tapered surface becomes wider, which reduces the coverage of the insulating film 226. However, according to this embodiment, the coverage of the insulating film 226 can also be ensured. In other respects, the contents described in the first embodiment are applicable.

[0049] [Modification of the second embodiment] 8 is a plan view of a semiconductor light receiving element according to a modification of the second embodiment. The upper surface of the wide band gap layer 218 is formed by a minimum encapsulation of a pair of vertices V′ in the

[0011] direction and the [0-1-1] direction (second direction D2). Containing The shape is included on the circumference of circle C'. The top surface of wide band gap layer 218 is polygonal (for example, rhombus or regular octagon).

[0050] The other points are the same as those of the second embodiment. The upper surface of the wide band gap layer 218 is formed by dividing a pair of vertices V' in the [0-11] direction and the [01-1] direction (first direction D1) into a minimum encapsulation. ContainingThe shape is included on the circumference of circle C'. The top surfaces of the layers above wide band gap layer 218 (the uppermost layer and absorption layer 216) are circular. The top surface of wide band gap layer 218 protrudes from absorption layer 216.

[0051] [Third embodiment] Fig. 9 is a plan view of a semiconductor light receiving element according to a third embodiment, Fig. 10 is an enlarged cross-sectional view of the semiconductor light receiving element of Fig. 9 taken along line XX, Fig. 11 is an enlarged cross-sectional view of the semiconductor light receiving element of Fig. 9 taken along line XI-XI.

[0052] The mesa structure 314 has a two-tiered structure including an upper mesa structure 350 and a lower mesa structure 352. The top surface of the wide bandgap layer 318 protrudes from the absorption layer 316. The top surfaces of the upper mesa structure 350 and the lower mesa structure 352 are similar in shape but different in size. Alternatively, the top surface of the upper mesa structure 350 may be diamond-shaped and the top surface of the lower mesa structure 352 may be octagonal, for example.

[0053] The upper surface of the upper mesa structure 350 is not circular, but has a vertex V in the first direction D1. Specifically, the upper surfaces of the layers (the uppermost layer and the absorption layer 316) above the wide band gap layer 318 are arranged in a shape that has a minimum periphery including a pair of vertices V1 in the [0-11] direction and the [01-1] direction (first direction D1). Containing The shape is included on the circumference of the circle C1. Therefore, the side surface of the upper mesa structure 350 does not include an inversely tapered surface, and therefore the coverage of the insulating film 326 is excellent.

[0054] The contents described in the first embodiment are applicable to other points. The upper surface of the wide band gap layer 318 is formed by a pair of vertices V2 in the [0-11] direction and the [01-1] direction (first direction D1) in a minimum enclosing manner. Containing It is a shape that is included on the circumference of circle C2.

[0055] [Fourth embodiment] Fig. 12 is a plan view of a semiconductor light receiving element according to a fourth embodiment. Fig. 13 is an enlarged cross-sectional view of the semiconductor light receiving element of Fig. 12 taken along line XIII-XIII. Fig. 14 is an enlarged cross-sectional view of the semiconductor light receiving element of Fig. 2 taken along line XIV-XIV.

[0056] The substrate 410 has a shape that allows signal light to be incident from the side opposite to the mesa structure 414. A lens 454 is formed on the back surface of the substrate 410. The lens 454 is configured to collect light incident from the outside. The semiconductor light receiving element is a back-illuminated semiconductor light receiving element in which signal light is incident from the back. In other respects, the details described in the first embodiment are applicable.

[0057] A first contact layer 412 is provided on the upper surface of the substrate 410. The first contact layer 412 is a semiconductor layer of a first conductivity type (e.g., n-type). A mesa structure 414 is disposed on the upper surface of the substrate 410 (specifically, on top of the first contact layer 412). The mesa structure 414 is in contact with and electrically connected to the first contact layer 412.

[0058] Light entering the mesa structure 414 is incident on the absorption layer 416, where it is absorbed and converted into electricity. The absorption layer 416 may be either an intrinsic semiconductor layer or a conductive semiconductor layer, or a combination of both. In this example, the absorption layer 416 is made of InGaAs.

[0059] The wide bandgap layer 418 is a semiconductor layer having a bandgap wider than that of the absorption layer 416 and wide enough not to absorb incident light. The wide bandgap layer 418 is made of an intrinsic semiconductor, which is InAlGaAs, but may also be InP.

[0060] The second contact layer 420 is an InGaAs layer, which is a semiconductor layer of a second conductivity type (e.g., p-type). A depletion layer is formed in the wide band gap layer 418 and the absorption layer 416 when a voltage is applied. The presence of the wide band gap layer 418 thickens the depletion layer, reducing parasitic capacitance and enabling high-speed operation.

[0061] The protruding structure 458 has the same layer structure as the mesa structure 414. The mesa structure 414 and the protruding structure 458 can be formed by growing the above-described layer structure using an MBE (Molecular Beam Epitaxy) apparatus and then separating them from each other using lithography techniques.

[0062] The insulating film 426 covers and protects the exposed surfaces (e.g., the entire surfaces) of the mesa structure 414, the protruding structure 458, and the first contact layer 412. The insulating film 426 is a passivation film and is an oxide film or a nitride film, such as a silicon oxide film or a silicon nitride film. The insulating film 426 has a first through-hole 428 in a portion of the upper surface of the first contact layer 412. The insulating film 426 has a second through-hole 430 in a portion of the upper surface of the mesa structure 414.

[0063] The semiconductor light-receiving element has an external electrode 456. The external electrode 456 is arranged so as to cover the upper surface and part of the side surface of the convex structure 458. The external electrode 456 and the first contact layer 412 are connected via a first through-hole 428 in the insulating film 426.

[0064] The semiconductor light-receiving element has a mesa electrode 436. The mesa electrode 436 is arranged in a circular shape on part of the upper surface of the mesa structure 414. The mesa electrode 436 and the second contact layer 420 are connected via a second through-hole 430 in the insulating film 426.

[0065] The mesa structure 414 has a shape having a vertex V in the first direction D1 in plan view. The plane of the mesa structure 414 is a plane that is formed by a minimum encapsulation of a pair of vertices V in the [0-11] direction and the [01-1] direction. Containing The shape is included on the circumference of the circle C. The mesa structure 414 has no vertex V in the second direction D2 and is in the shape of an arc.

[0066] In this embodiment, since no reverse tapered surface is formed on the side surface of the mesa structure 414, the coverage of the insulating film 426 covering the side surface of the mesa structure 414 is improved, and as a result, reliability can be ensured. Furthermore, since a thick wide band gap layer 418 can be employed, high-speed operation can be achieved.

[0067] As a modification, the top surfaces of the layers above wide band gap layer 418 (the uppermost layer and absorption layer 416) may be circular, forming mesa structure 414 in a two-tiered structure. Alternatively, the top surface of wide band gap layer 418 may have a shape that combines straight lines and arcs, or a polygon such as an octagon or a diamond.

[0068] The present invention is not limited to the above-described embodiments and various modifications are possible. For example, the configurations described in the embodiments can be replaced with substantially the same configurations, configurations that achieve the same effects, or configurations that can achieve the same objectives.

[0069] [Outline of the embodiment] (1) A mesa structure 14 is provided on the substrate 10 and is composed of a plurality of layers including an upper layer and a lower layer, the upper layer being a light absorbing layer 16, and the lower layer being a wide band gap layer 18 having a band gap wide enough not to absorb the light, and an insulating film 26 covering a side surface of the mesa structure 14, wherein each of the plurality of layers is made of a single crystal of a III-V group semiconductor, has a (100) plane as an upper surface, and the upper surface of the wide band gap layer 18 is formed in a plane that least encloses a pair of vertices V in the [0-11] direction and the [01-1] direction. Containing A semiconductor light-receiving element whose shape is included on the circumference of circle C.

[0070] Since there are pairs of vertices V in the [0-11] direction and the [01-1] direction, it is difficult to form an inversely tapered surface, and therefore coverage of the insulating film 26 can be ensured.

[0071] (2) The semiconductor light receiving element according to (1), wherein each angle of the pair of vertices V is 135 degrees or less.

[0072] (3) The semiconductor light receiving element according to (1) or (2), wherein the upper surface of the wide band gap layer 18 has a pair of tips in the

[0011] direction and the [0-1-1] direction, which are arranged in the minimum envelope. Containing A semiconductor photodetector whose shape is included inside circle C.

[0073] (4) A semiconductor light receiving element according to (3), wherein the upper surface of the wide band gap layer 18 has a shape including a pair of arcs convex in the

[0011] direction and the [0-1-1] direction, respectively.

[0074] (5) The semiconductor light receiving element according to (1) or (2), wherein the upper surface of the wide band gap layer 18 has a pair of vertices V' in the

[0011] direction and the [0-1-1] direction, which are arranged within the minimum envelope. Containing A semiconductor light receiving element having a shape that is included on the circumference of circle C'.

[0075] (6) The semiconductor light-receiving element according to (5), wherein the upper surface of the wide band gap layer 18 is polygonal.

[0076] (7) The semiconductor light receiving element according to any one of (1) to (6), wherein the upper surface of the layer above the wide band gap layer 18 is formed by a minimum enclosing pair of vertices V in the [0-11] direction and the [01-1] direction. Containing A semiconductor light-receiving element whose shape is included on the circumference of circle C.

[0077] (8) A semiconductor photodetector according to any one of (1) to (7), wherein the upper surface of the wide band gap layer 18 coincides with the lower surface of the absorption layer 16 in external shape.

[0078] (9) The semiconductor light-receiving element according to any one of (1) to (6), wherein the upper surface of the layer above the wide band gap layer 218 is circular.

[0079] (10) The semiconductor light-receiving element according to any one of (1) to (8), wherein the upper surface of the wide band gap layer 218 protrudes from the absorption layer 216.

[0080] (11) A semiconductor photodetector according to any one of (1) to (10), further comprising an electrode pattern 32, the electrode pattern 32 including a mesa electrode 36 on the upper surface of the mesa structure 14.

[0081] (12) A semiconductor photodetector as described in (11), wherein the electrode pattern 32 further includes a connection electrode connected to the mesa electrode 36, and the connection electrode extends in the

[0011] direction or the [0-1-1] direction.

[0082] (13) The semiconductor light-receiving element according to (11) or (12), wherein the mesa electrode 36 has an opening 38 in a plan view.

[0083] (14) The semiconductor light receiving element according to (13), wherein the opening 38 has a shape that allows signal light to enter.

[0084] (15) The semiconductor light receiving element according to (14), wherein the opening 38 is circular.

[0085] (16) The semiconductor light-receiving element according to (15), wherein the mesa electrode 36 is ring-shaped in a plan view.

[0086] (17) A semiconductor light receiving element according to any one of (1) to (12), wherein the substrate 410 has a shape that allows signal light to be incident from the side opposite to the mesa structure 414.

[0087] (18) The semiconductor light-receiving element according to any one of (1) to (17), wherein the wide band gap layer 18 is thicker than the absorption layer 16.

[0088] (19) The semiconductor light-receiving element according to any one of (1) to (18), wherein the wide band gap layer 18 is made of any one of InAlGaAs, InAlAs, and InP.

[0089] (20) The semiconductor light-receiving element according to any one of (1) to (19), wherein the absorption layer 16 is made of InGaAs. [Explanation of symbols]

[0090] 10 substrate, 12 first contact layer, 14 mesa structure, 16 absorption layer, 18 wide band gap layer, 20 second contact layer, 22 first convex structure, 24 second convex structure, 26 insulating film, 28 first through hole, 30 second through hole, 32 electrode pattern, 34 first electrode, 36 mesa electrode, 38 opening, 40 first external electrode, 42 first connecting electrode, 44 second electrode, 46 second external electrode, 48 second connecting electrode, 214 mesa structure, 216 absorption layer, 218 wide band gap layer, 220 second contact layer, 226 insulating film, 250 upper mesa structure, 252 lower mesa structure, 314 mesa structure, 316 absorption layer, 318 wide band gap layer, 326 insulating film, 350 upper mesa structure, 352 lower mesa structure, 410 substrate, 412 First contact layer, 414, mesa structure, 416, absorption layer, 418, wide band gap layer, 420, second contact layer, 426, insulating film, 428, first through hole, 430, second through hole, 436, mesa electrode, 454, lens, 456, external electrode, 458, convex structure, C minimum envelope Containing Circle, C1 minimum hull Containing Circle, C2 minimum hull Containing Circle, D1 first direction, D2 second direction, V vertex, V1 vertex, V2 vertex.

Claims

1. A substrate; a mesa structure on the substrate, the mesa structure being composed of a plurality of layers including an upper layer and a lower layer, the upper layer being a light absorbing layer, and the lower layer being a wide band gap layer having a band gap wide enough not to absorb the light; an insulating film covering a side surface of the mesa structure; Equipped with Each of the plurality of layers is made of a single crystal of a III-V group semiconductor, and has a (100) plane as an upper surface, The upper surface of the wide band gap layer has a shape that includes a pair of vertices in the [0-11] direction and the [01-1] direction on the circumference of a smallest inclusive circle.

2. 2. The semiconductor light-receiving element according to claim 1, The angle between the pair of vertices is 135 degrees or less.

3. 2. The semiconductor light-receiving element according to claim 1, The upper surface of the wide band gap layer has a shape that includes a pair of tips in the [011] direction and the [0-1-1] direction inside the minimum inclusive circle.

4. 4. The semiconductor light-receiving element according to claim 3, The semiconductor light-receiving element has an upper surface of the wide band gap layer that has a shape including a pair of arcs that are convex in the [011] direction and a pair of arcs that are convex in the [0-1-1] direction.

5. 2. The semiconductor light-receiving element according to claim 1, The semiconductor light-receiving element has a shape in which the upper surface of the wide band gap layer includes a pair of vertices in the [011] direction and the [0-1-1] direction on the circumference of the smallest inclusive circle.

6. 6. The semiconductor light-receiving element according to claim 5, The semiconductor light-receiving element has a polygonal top surface of the wide band gap layer.

7. 2. The semiconductor light-receiving element according to claim 1, The upper surface of the layer above the wide band gap layer has a shape that includes a pair of vertices in the [0-11] direction and the [01-1] direction on the circumference of a smallest inclusive circle.

8. 2. The semiconductor light-receiving element according to claim 1, The semiconductor light-receiving element has an upper surface of the wide band gap layer that coincides with a lower surface of the absorption layer in terms of outer shape.

9. 2. The semiconductor light-receiving element according to claim 1, The upper surface of the layer above the wide band gap layer is circular.

10. 2. The semiconductor light-receiving element according to claim 1, The upper surface of the wide band gap layer protrudes from the absorption layer.

11. 2. The semiconductor light-receiving element according to claim 1, further comprising an electrode pattern; The electrode pattern includes a mesa electrode on the top surface of the mesa structure.

12. 12. The semiconductor light-receiving element according to claim 11, the electrode pattern further includes a connection electrode connected to the mesa electrode; The connection electrodes extend in the [011] direction or the [0-1-1] direction.

13. 12. The semiconductor light-receiving element according to claim 11, The mesa electrode has an opening in a plan view.

14. 14. The semiconductor light-receiving element according to claim 13, The opening is a semiconductor light receiving element having a shape that allows signal light to enter.

15. 15. The semiconductor light-receiving element according to claim 14, The opening is a circular semiconductor light receiving element.

16. 16. The semiconductor light-receiving element according to claim 15, The mesa electrode is a semiconductor light-receiving element having a ring shape in a plan view.

17. 2. The semiconductor light-receiving element according to claim 1, The substrate is a semiconductor light-receiving element having a shape that allows signal light to be incident from the side opposite to the mesa structure.

18. 2. The semiconductor light-receiving element according to claim 1, The wide band gap layer is thicker than the absorption layer.

19. 2. The semiconductor light-receiving element according to claim 1, The wide band gap layer is made of any one of InAlGaAs, InAlAs, and InP.

20. 2. The semiconductor light-receiving element according to claim 1, The absorption layer is a semiconductor light-receiving element made of InGaAs.

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