JP2013171920A - Semiconductor light-receiving element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor light-receiving element which can re-collect light which was not absorbed in a light-receiving region with high collection efficiency in the light-receiving region to photoelectrically convert the re-collected light.SOLUTION: A semiconductor light-receiving element 10 of a present embodiment comprises: a semiconductor substrate 20; a light-receiving part 30 which is arranged on a top face of the semiconductor substrate 20 and on which light is incident; and a reflection part 40 arranged under the semiconductor substrate 20 for reflecting light transmitted through the light-receiving part 30. In this case, the reflection part 40 is arranged at a position where a reflection light spot size φr of light reflected by the reflection part 40 and incident upon the light-receiving part 30 again is not more than an incident light spot size φi of light incident upon the light-receiving part 30.

Description

  The present invention relates to a semiconductor light receiving element used in optical communication, optical information processing, and the like, and more particularly to a semiconductor light receiving element in which a light absorption layer is formed thin.

  Semiconductor light receiving elements have been put to practical use as high sensitivity light receivers for optical communication and optical information processing. The semiconductor light receiving element is particularly used as a high sensitivity light receiver for communication light having a wavelength of 1.3 μm or 1.55 μm for large-capacity long-distance optical communication.

  However, when the light absorption layer is thinned to 2 μm or less for the purpose of high-speed response characteristics and high light input resistance characteristics, the quantum efficiency of the semiconductor light receiving element is lowered. In particular, communication light with a wavelength of 1.55 μm has a large decrease in quantum efficiency, and sufficient sensitivity may not be obtained.

  Therefore, Patent Document 1 discloses a semiconductor light receiving element in which a curved reflection layer is disposed below a semiconductor substrate. A cross-sectional view of the semiconductor light-receiving element of Patent Document 1 is shown in FIG. In the semiconductor light receiving element 900 shown in FIG. 10, light that has not been subjected to photoelectric conversion in the light receiving region 920 is reflected by a curved reflective layer 930 disposed below the semiconductor substrate 910 and is incident on the light receiving region 920 again. And photoelectrically converted.

JP 2001-308366 A

  Here, the incident light may be incident on the light receiving area in the vertical direction or may be incident on the light receiving area at an angle. In the semiconductor light receiving element 900 of Patent Document 1, light incident in the vertical direction on the light receiving region 920 can be reflected by the curved reflective layer 930 and condensed again on the light receiving region 920. On the other hand, the light incident obliquely cannot be collected effectively.

  In view of the above problems, an object of the present invention is to provide a semiconductor light receiving element capable of photoelectrically converting light that has not been absorbed in the light receiving region into the light receiving region with a high light collection rate.

  In order to achieve the above object, a semiconductor light receiving device according to the present invention includes a semiconductor substrate, a light receiving portion that is disposed on the upper surface of the semiconductor substrate, and a light that is incident on the lower side of the semiconductor substrate and transmits light transmitted through the light receiving portion. A reflecting portion that reflects. Here, the reflection part is arranged at a position where the reflected light spot size of the light reflected by the reflection part and incident again on the light receiving part is equal to or smaller than the incident light spot size of light incident on the light receiving part.

  The semiconductor light-receiving element according to the present invention can photoelectrically convert light that has not been absorbed in the light-receiving region by re-condensing it in the light-receiving region with a high light collection rate.

1 is a cross-sectional view of a semiconductor light receiving element 10 according to a first embodiment of the present invention. It is sectional drawing of the semiconductor light receiving element 100 which concerns on the 2nd Embodiment of this invention. It is a figure which shows the relationship between incident light spot size (phi) i and reflected light spot size (phi) r. It is a manufacturing-process figure of the semiconductor light receiving element 100 which concerns on the 2nd Embodiment of this invention. It is sectional drawing of another semiconductor light receiving element 100B which concerns on the 2nd Embodiment of this invention. It is sectional drawing of 100 C of semiconductor light receiving elements which concern on the 3rd Embodiment of this invention. It is sectional drawing of another semiconductor light receiving element 100D which concerns on the 3rd Embodiment of this invention. It is sectional drawing of the semiconductor light receiving element 100E which concerns on the 4th Embodiment of this invention. It is a manufacturing-process figure of the semiconductor light receiving element 100E which concerns on the 4th Embodiment of this invention. FIG. 10 is a cross-sectional view of a semiconductor light receiving element 900 of Patent Document 1.

(First embodiment)
The semiconductor light receiving element according to the first embodiment will be described. A cross-sectional view of the semiconductor light receiving element according to this embodiment is shown in FIG. In FIG. 1, a semiconductor light receiving element 10 according to this embodiment includes a semiconductor substrate 20, a light receiving unit 30, and a reflecting unit 40.

  The semiconductor substrate 20 is formed by laminating a plurality of layers on the upper surface of the first conductivity type semiconductor layer. The light receiving unit 30 is disposed on the upper surface of the semiconductor substrate 20. The light receiving unit 30 includes a second conductivity type impurity region and absorbs incident light to convert it into an electrical signal. The reflection unit 40 is disposed below the semiconductor substrate 20 and reflects light that has not been absorbed by the light receiving unit 30.

  In the semiconductor light receiving element 10 according to the present embodiment, the reflection unit 40 has a reflected light spot size φr of light that is reflected by the reflection unit 40 and reenters the light reception unit 30, and an incident light spot of light that enters the light reception unit 30. It arrange | positions in the position used as size φi or less. Specifically, the reflecting unit 40 is disposed on the focal position F where the light incident on the boundary of the incident light spot size φi is collected or on the light receiving unit 30 side from the focal position F.

  By disposing the reflection portion 40 at a position where the reflected light spot size φr is equal to or smaller than the incident light spot size φi, the reflected light can be condensed and photoelectrically converted to the light receiving portion 30 with a high condensing rate. Therefore, the semiconductor light receiving element 10 according to the present embodiment can photoelectrically convert light that has not been absorbed by the light receiving unit 30 by refocusing on the light receiving unit 30 with a high light collection rate.

  Here, the reflected light spot size φr varies depending on the design parameters of the optical system for making light incident on the semiconductor light receiving element 10, the thickness of the semiconductor substrate 20, the refractive index of the semiconductor substrate 20, and the like. Therefore, it is desirable to determine the position of the reflection unit 40 in conjunction with optimization of the design of the entire optical receiver including the semiconductor light receiving element.

(Second Embodiment)
A second embodiment will be described. FIG. 2 shows a cross-sectional view of the semiconductor light receiving element according to this embodiment. In FIG. 2, the semiconductor light receiving element 100 according to the present embodiment includes a semiconductor substrate 200, a light receiving unit 300, and a reflective film 400.

  The semiconductor substrate 200 is formed by laminating a plurality of layers on the upper surface of the first conductivity type semiconductor layer. In the semiconductor substrate 200, for example, an n-type InP buffer layer, an InGaAsP light absorption layer, an n-type InP electric field relaxation layer, an n-type InP window layer, and the like are sequentially formed on the upper surface of an n-type InP substrate as a first conductivity type semiconductor layer. It is formed by stacking. In addition, a light receiving unit 300 is disposed in a light receiving region in the upper surface of the semiconductor substrate 200, and a hole 210 is formed at a position facing the light receiving unit 300 on the lower surface of the semiconductor substrate 200. The hole 210 will be described later.

  The light receiving unit 300 includes a second conductivity type impurity region. The light receiving unit 300 is disposed in the upper surface of the semiconductor substrate 200 and absorbs incident light to convert it into an electrical signal. The light receiving unit 300 is formed by injecting a p-type impurity such as Zn into the light receiving region of the semiconductor substrate 200.

  The reflective film 400 is disposed on the lower surface of the semiconductor substrate 200 and the side surfaces and the bottom surface of the hole 210, and is incident on the light receiving unit 300 and reflects light that has not been absorbed by the light receiving unit 300. As the reflective film 400, for example, a metal thin film can be applied.

  The hole 210 will be described. The hole portion 210 is formed by removing a position corresponding to the light receiving portion 300 on the lower surface of the semiconductor substrate 200 in a concave shape. In the present embodiment, the depth d of the hole 210 is set so that the bottom surface of the hole 210, that is, the reflective film 400 is positioned at the focal position F of the light incident on the boundary of the incident light spot size φi of the light receiving unit 300. Designed. In this case, an incident light spot size φi that is a spot size when light is incident on the light receiving unit 300, and a reflected light spot size that is a spot size when light reflected by the reflective film 400 is incident on the light receiving unit 300 again. φr matches. By disposing the reflective film 400 at the focal position F of incident light, the light reflected by the reflective film 400 is condensed in the region of the light receiving unit 300 with a high condensing rate.

  Here, the incident light spot size φi indicates a range of a region where incident light enters the light receiving unit 300. On the other hand, the reflected light spot size φr refers to a range defined by the position when the light incident on the boundary of the incident light spot size φi is reflected by the reflective film 400 and reenters the light receiving unit 300. 3A to 3E show the relationship between the incident light spot size φi and the reflected light spot size φr.

  As shown in FIG. 3A, when the reflected light spot size φr is larger than the incident light spot size φi, a part of the light incident on the light receiving portion from an oblique direction and reflected by the reflecting film is retransmitted to the light receiving portion. The light is not condensed and the photoelectric conversion efficiency is lowered. On the other hand, in the case of the semiconductor light receiving element 100 shown in FIGS. 3B to 3E, the reflected light spot size φr is equal to or smaller than the incident light spot size φi, so that the light reflected by the reflective film is high. The light is condensed again on the light receiving portion with the light collection rate. Accordingly, the photoelectric conversion efficiency is improved.

  Next, a method for manufacturing the semiconductor light receiving element 100 according to this embodiment will be described. A manufacturing process of the semiconductor light receiving element 100 according to this embodiment is shown in FIG.

  As shown in FIG. 4A, first, an n-type InP buffer layer, an InGaAsP light absorption layer, an n-type InP electric field relaxation layer, an n-type InP window layer, and the like are sequentially stacked on an n-type InP substrate to form a semiconductor. A substrate 200 is formed. Then, a second conductivity type impurity region is formed by diffusing or ion-implanting a p-type impurity, for example, Zn in the light receiving region of the InP window layer of the semiconductor substrate 200. Further, a guard ring (not shown) is formed around the second conductivity type impurity region by, for example, diffusing or ion-implanting Be to form the light receiving unit 300.

  Next, as shown in FIG. 4B, the lower region of the light receiving portion 300 of the semiconductor substrate 200 is removed by using a photolithography method, a semiconductor etching method, or the like to form a hole 210. Here, the hole 210 is formed at a depth d at which the bottom surface of the hole 210 is located at the focal position F of incident light incident from the light receiving unit 300. When the bottom surface of the hole 210 is located at the focal position F, the incident light spot size φi and the reflected light spot size φr coincide with each other.

  Further, as shown in FIG. 4C, the reflective film 400 is formed on the entire lower surface of the substrate 200 including the side surface and the bottom surface of the hole 210 by, for example, vapor deposition of TiPtAu, and the semiconductor according to the present embodiment. The light receiving element 100 is formed.

  The semiconductor light receiving element 100 formed as described above converts incident light into an electrical signal in the light receiving unit 300. On the other hand, incident light that has not been converted into an electrical signal reaches the reflective film 400. The incident light that has reached the reflective film 400 is retransmitted to the light receiving unit 300 with a high light collection rate because the reflective film 400 is disposed at a position where the incident light spot size φi and the reflected light spot size φr coincide with each other. It is condensed and photoelectrically converted. Accordingly, the photoelectric conversion efficiency is improved.

  In the semiconductor light receiving element 100 formed as described above, the hole 210 is formed in the semiconductor substrate 200, and the reflective film 400 is disposed in the hole 210. In this case, the depth d of the hole 210 can be designed separately from the thickness of the semiconductor substrate 200. For example, for the convenience of designing the entire optical receiver, even when the focal position of the incident light comes near the light receiving unit 300, the depth d of the hole 210 may be designed in accordance with the focal position F. The thickness of 200 can be kept thick. Therefore, the mechanical strength of the semiconductor light receiving element 100 can be maintained.

  Here, generally, when incident light is concentrated in a narrow area, the photocurrent density in that area increases. When the photocurrent density is high, it is difficult to extract the generated carriers, and the frequency response is deteriorated. Therefore, it is desirable to reduce the photocurrent density by dispersing incident light as much as possible throughout the light receiving unit 300B. When the total incident light power is determined, the incident light spot size φi is increased and the incident light is dispersed throughout the light receiving unit 300B, thereby reducing the deterioration of the frequency response due to the increase in photocurrent density. FIG. 5 shows a cross-sectional view of the semiconductor light receiving element when the incident light spot size φi is increased.

  The incident light spot size φi of the semiconductor light receiving element 100B shown in FIG. 5 is larger than the incident light spot size φi of the semiconductor light receiving element 100 shown in FIG. Therefore, when the total incident light power is determined, the incident light is dispersed throughout the light receiving unit 300B, and deterioration of frequency response due to an increase in photocurrent density can be reduced.

  However, when the incident light spot size φi is increased, the virtual focal position F of the incident light is separated from the light receiving unit 300B, and the light collection rate is reduced due to scattering or the like. Therefore, in the semiconductor light receiving element 100B shown in FIG. 5, the reflection film 400 is positioned so that the depth d ′ of the hole 210B formed in the semiconductor substrate 200B is at the focal position F of the light incident from the light receiving unit 300. The depth d was designed to be larger than the designed depth d. In this case, it can reduce that a condensing rate falls by scattering etc.

  When the bottom surface of the hole 210B is positioned closer to the light receiving unit 300B than the focal position F, the reflected light spot size φr is smaller than the incident light spot size φi. Generally, when the reflected light spot size φr is small, the power of the light reflected by the reflective film and incident on the light receiving unit again is lower than the power of the light directly incident on the light receiving unit from the incident optical system. However, the increase in photocurrent density due to the concentration of reflected light can be ignored.

  As described above, in the semiconductor light receiving element 100B shown in FIG. 5, since the incident light spot size φi is increased, the incident light is dispersed throughout the light receiving unit 300B, and the deterioration of the frequency response due to the increase in photocurrent density is reduced. be able to. In addition, the depth d ′ of the hole 210B is designed to be larger than the depth d when the reflective film 400 is designed to be positioned at the focal position F of the light incident from the light receiving unit 300. A decrease in the light collection rate can be reduced. Further, since the reflected light spot size φr is smaller than the incident light spot size φi, the light reflected by the reflective film 400B is condensed on the light receiving unit 300B with a high condensing rate and is photoelectrically converted. Therefore, the photoelectric conversion efficiency can be improved.

(Third embodiment)
A third embodiment will be described. FIG. 6 shows a cross-sectional view of the semiconductor light receiving element according to this embodiment. In FIG. 6, a semiconductor light receiving element 100C according to this embodiment includes a semiconductor substrate 200C, a light receiving unit 300C, and a reflective film 400C.

  The semiconductor substrate 200C is formed by stacking a plurality of layers on the upper surface of the first conductivity type semiconductor layer. The light receiving unit 300C includes a second conductivity type impurity region and absorbs incident light to convert it into an electrical signal. The reflective film 400C is disposed on the lower surface of the semiconductor substrate 200 and reflects light that has not been absorbed by the light receiving unit 300C.

  In the present embodiment, the thickness t of the semiconductor substrate 200C is designed to be equal to the distance from the light receiving unit 300C to the focal length F of light incident on the light receiving unit 300C (hereinafter referred to as the focal length). ing. The thickness t of the semiconductor substrate 200C is designed to be about 100 to 200 μm, for example, equivalent to the focal length.

  Here, the focal length is determined from the design of the entire optical receiver including the incident optical system. The focal length is adjusted by, for example, arranging a high refractive index layer, a micro lens, or the like on the upper surface of the light receiving unit 300C, adjusting the area of the light receiving unit 300C, or adjusting the refractive index of the semiconductor substrate 200. be able to. The focal length can be adjusted to a desired value by adjusting the incident condition of light incident on the semiconductor light receiving element 100C.

  In the semiconductor light receiving element 100C according to the present embodiment, the reflective film 400C is disposed at the focal position F of the incident light by adjusting the thickness t of the semiconductor substrate 200C to a value equivalent to the focal length of the incident light. In this case, an incident light spot size φi that is a spot size when light is incident on the light receiving unit 300C, and a reflected light spot size that is a spot size when light reflected by the reflective film 400C is incident on the light receiving unit 300C again. φr matches. Therefore, the light reflected by the reflective film 400C is condensed on the light receiving unit 300C with a high condensing rate.

  As described above, the semiconductor light receiving element 100 </ b> C according to the present embodiment can condense reflected light on the light receiving unit 300 </ b> C with a high light collection rate and perform photoelectric conversion, thereby improving the photoelectric conversion efficiency. Furthermore, since the semiconductor light receiving element 100C according to the present embodiment does not need to form a hole or the like in the semiconductor substrate 200C, the manufacturing cost can be reduced.

  Here, when the total incident light power is determined, it is desirable to increase the incident light spot size φi in order to reduce the deterioration of the frequency response due to the increase in the photocurrent density. FIG. 7 shows a cross-sectional view of the semiconductor light receiving element when the incident light spot size φi is designed to be large.

  The incident light spot size φi of the semiconductor light receiving element 100D shown in FIG. 7 is larger than the incident light spot size φi of the semiconductor light receiving element 100C shown in FIG. Therefore, when the total incident light power is determined, the incident light is dispersed throughout the light receiving unit 300D, and deterioration of the frequency response due to the increase in photocurrent density can be reduced.

  However, when the incident light spot size φi is increased, the virtual focal position F of the incident light is separated from the light receiving unit 300D, and the light collection rate is reduced due to scattering or the like. Therefore, in the semiconductor light receiving element 100D shown in FIG. 7, the thickness t ′ of the semiconductor substrate 200D is designed to be smaller than the thickness t when the reflective film is designed to be positioned at the focal position F. In this case, it can reduce that a condensing rate falls by scattering etc.

  When the reflective film 400D is positioned closer to the light receiving unit 300D than the focal position F, the reflected light spot size φr is smaller than the incident light spot size φi. Also in this case, the light reflected by the reflective film 400D is condensed on the light receiving unit 300D with a high condensing rate. Therefore, the reflected light can be efficiently received again by the light receiving unit 300D and subjected to photoelectric conversion, and the photoelectric conversion efficiency can be improved. Furthermore, since the semiconductor light receiving element 100D according to the present embodiment does not need to form a hole or the like in the semiconductor substrate 200D, the manufacturing cost can be reduced.

(Fourth embodiment)
A fourth embodiment will be described. FIG. 8 shows a cross-sectional view of the semiconductor light receiving element according to this embodiment. In FIG. 8, a semiconductor light receiving element 100E according to this embodiment includes a semiconductor substrate 200E, a light receiving unit 300E, and a reflective film 400E.

  The semiconductor substrate 200E is formed by stacking a plurality of layers on the upper surface of the first conductivity type semiconductor layer. A light receiving portion 300E is disposed in the light receiving region on the upper surface of the semiconductor substrate 200E, and a hole 210E is formed at a position facing the light receiving portion 300E on the lower surface of the semiconductor substrate 200E. The hole 210E will be described later.

  The light receiving unit 300E includes a second conductivity type impurity region, absorbs incident light, and converts it into an electrical signal. The reflective film 400E is disposed on the lower surface of the semiconductor substrate 200E and the side surfaces and the bottom surface of the hole 210E, and reflects light incident on the light receiving unit 300E and not absorbed by the light receiving unit 300E toward the light receiving unit 300E. . As the reflective film 400E, for example, a metal thin film can be applied.

  The hole 210E will be described. The hole 210E is formed by removing the position corresponding to the light receiving part 300E on the lower surface of the semiconductor substrate 200E in a concave shape. Furthermore, the bottom surface of the hole 210E is processed into a spherical shape. In the present embodiment, the hole 210E is designed so that the focal position F of the incident light incident from the light receiving unit 300E matches the geometric center O of the spherical bottom surface of the hole 210E.

  In this case, an incident light spot size φi that is a spot size when light is incident on the light receiving unit 300E, and a reflected light spot size that is a spot size when light reflected by the reflective film 400E is incident on the light receiving unit 300E again. φr matches. By making the focal position F of the incident light coincide with the geometric center O of the spherical bottom surface, the light reflected by the reflective film 400E is collected again at the focal position F (geometric center O). The light is condensed on the light receiving unit 300E with a high light collection rate.

  Next, a method for manufacturing the semiconductor light receiving element 100E according to this embodiment will be described. FIG. 9 shows a manufacturing process of the semiconductor light receiving element 100E according to this embodiment.

  In FIG. 9A, as in the second embodiment, an n-type InP buffer layer, an InGaAsP light absorption layer, an n-type InP electric field relaxation layer, and an n-type InP window layer are formed on a first conductivity type semiconductor substrate. Etc. are sequentially stacked to form a semiconductor substrate 200E, and a second conductivity type impurity region is formed in a part of the InP window layer of the semiconductor substrate 200E to form a light receiving portion 300E. Further, the region below the light receiving portion 300E of the semiconductor substrate 200E is removed by using a photolithography method, a semiconductor etching method, or the like to form the hole portion 210E.

  Next, as shown in FIG. 9B, a mesa-like structure is formed on the bottom surface of the hole 210E of the semiconductor substrate 200E by using a photolithography method or a semiconductor etching method. Further, the back surface of the device is covered with a resist film except for the concave portion including the mesa structure by using a photolithography method.

  In this state, as shown in FIG. 9C, the entire mesa structure is etched by wet etching to form a spherical shape, and the resist is removed. In the hole 210E forming process, the mesa structure forming process, and the mesa structure etching process, the focal position F of incident light and the geometric center O of the spherical bottom surface of the hole 210E Adjust so that they match.

  Finally, as shown in FIG. 9D, the reflective film 400E is formed by, for example, vapor-depositing TiPtAu on the lower surface of the semiconductor substrate 200E and the side surfaces and the bottom surface of the hole 210E. The semiconductor light receiving element 100E is obtained.

  In the semiconductor light receiving element 100E formed as described above, in the hole 210E, the focal position F of the incident light incident from the light receiving unit 300E matches the geometric center O of the spherical bottom surface of the hole 210E. Designed to be. In this case, incident light that has not been absorbed by the light receiving unit 300E but has passed through the focal position F and reached the reflective film 400E is reflected by the reflective film 400E and collected again at the focal position F, and then has a high light collection rate. Is condensed on the light receiving unit 300E. Therefore, the reflected light can be efficiently received again by the light receiving unit 300E and subjected to photoelectric conversion, and the photoelectric conversion efficiency is improved.

  In addition, the reflective film 400E is not disposed at the focal position F of the incident light, but the reflective film 400E is disposed on a spherical surface with the focal position F of the incident light as the geometric center O, thereby reflecting the light receiving unit 300E and the reflection. The distance from the film 400E can be increased, and the thickness of the semiconductor substrate 200E below the light receiving portion 300E can be increased. Therefore, the mechanical strength of the semiconductor substrate 200E can be increased.

  Note that the present invention is not limited to the above-described embodiment, and any design change or the like within a range not departing from the gist of the present invention is included in the present invention.

DESCRIPTION OF SYMBOLS 10 Semiconductor light receiving element 20 Semiconductor substrate 30 Light receiving part 40 Reflecting part 100, 100B, 100C, 100D, 100E Semiconductor light receiving element 200, 200B, 200C, 200D, 200E Semiconductor substrate 210, 210B, 210E Hole part 300, 300B, 300C, 300D , 300E light receiving part 400, 400B, 400C, 400D, 400E reflective film 900 semiconductor light receiving element 910 semiconductor substrate 920 light receiving area 930 reflective layer

Claims (5)

A semiconductor substrate;
A light receiving portion disposed on an upper surface of the semiconductor substrate and receiving light;
A reflective portion that is disposed below the semiconductor substrate and reflects light transmitted through the light receiving portion;
With
The reflection part is disposed at a position where a reflected light spot size of light reflected by the reflection part and incident again on the light receiving part is equal to or smaller than an incident light spot size of light incident on the light receiving part. Semiconductor light receiving element. 2. The semiconductor light receiving element according to claim 1, wherein the reflecting portion is disposed at a focal position of light incident on a boundary of the incident light spot size or at a light receiving portion side with respect to the focal position. The semiconductor substrate includes a hole formed below and facing the light receiving unit,
The bottom surface of the hole is located closer to the light receiving unit than the focal position or the focal position,
The reflecting portion is disposed on the bottom surface of the hole portion,
The semiconductor light receiving element according to claim 2. The thickness of the semiconductor substrate is not more than the distance from the light receiving unit to the focal position,
The reflective portion is disposed on a lower surface of the semiconductor substrate.
The semiconductor light receiving element according to claim 2. The semiconductor substrate includes a hole formed below and facing the light receiving unit,
The bottom surface of the hole is formed in a curved shape whose center coincides with the focal position,
The reflecting portion is disposed on the bottom surface of the hole portion,
The semiconductor light receiving element according to claim 2.

Images