JP2011258691A - Light-receiving element array - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light-receiving element array in which optical crosstalk can be minimized by additionally forming an isolation trench having a V-shaped cross-section in a conventional epitaxial structure.SOLUTION: The light-receiving element array 1 has a first conductivity type semiconductor substrate 2, a first conductivity type light-receiving layer 4 formed on the surface side of the semiconductor substrate 2, a first conductivity type window layer 5 formed on the surface side of the light-receiving layer, a plurality of second conductivity type regions 6 formed in a state of penetrating the window layer and plunging into the surface side of the light-receiving layer and formed separately as one-dimensional or two-dimensional arrangement, and a plurality of first electrodes 7 provided at least partially on the surface of the plurality of second conductivity type regions 6, respectively. In a plurality of regions between the arrays formed by a plurality of arrays consisting of the plurality of second conductivity type regions 6, first isolation trenches 10 having a V-shaped cross-section open to the surface side are provided to penetrate at least the window layer 5 and the light-receiving layer 4.

Description

  The present invention relates to a light receiving element array, and relates to a light receiving element array for optical communication or one-dimensional or two-dimensional sensor capable of suppressing optical crosstalk.

Conventionally, various light receiving element arrays for optical communication or one-dimensional and two-dimensional sensors have been put to practical use. The light receiving element array includes, for example, an upper surface incident type in which light is incident from the upper surface side of the array, and a lower surface incident type in which light is incident from the lower surface side of the array.
Here, FIG. 8 shows a general structure of a top-illuminated light receiving element array, and FIG. 9 shows a general structure of a bottom-illuminated light receiving element array.

  In order to manufacture the light receiving element arrays 21 and 21A shown in FIGS. 8 and 9, the n type InP buffer layer 23, the n type InGaAs light receiving layer 24, and the n type InP window are first formed on the n type InP semiconductor substrate 22. Layers 25 are epitaxially grown in this order. Next, by photolithography, a plurality of openings are provided on the n-type InP window layer 25 at a constant pitch so as to be one-dimensional or two-dimensional, and Zn is diffused into each of the plurality of openings to form p-type. Region 26 is formed. Thereby, a pn junction 31 is formed from each of the plurality of p-type regions 26 and the n-type InGaAs light receiving layer 24, and the pn structure photodiodes are arranged one-dimensionally or two-dimensionally.

Next, for example, in the case of the top-illuminated light receiving element array 21 shown in FIG. 8, a p-type electrode 27 is partially provided on the upper surface of each p-type region 26, and the p-type electrode 27 in the p-type region 26 is excluded. An antireflection film 32 is provided on the remaining upper surface and the upper surface of the window layer 25, and a common n-type electrode 28 is formed over the entire back surface of the n-type InP substrate 22.
In the case of the bottom-illuminated light receiving element array 21A shown in FIG. 9, a p-type electrode 27A is partially provided on the upper surface of each p-type region 26, and the p-type region 26 is surrounded by the upper surface of the window layer 25. A plurality of n-type electrodes 28 </ b> A that are C-type and slit-shaped are provided, and an antireflection film 33 is formed on the back surface of the n-type InP substrate 22.

  Incidentally, in the conventional light receiving element array 21 of FIG. 8, the light receiving elements are not separated. For this reason, when light incident on the vicinity of the pn junction 31 (depletion layer) of the light receiving element generates carriers of electron-hole pairs, some of the generated carriers pass through the light receiving layer 24 by lateral diffusion. There is a possibility of moving to the vicinity of the pn junction 31 of the adjacent light receiving element. At this time, there is a problem that the characteristics of the light receiving element array are deteriorated because a photocurrent flows to an adjacent light receiving element due to the moved carrier and electrical crosstalk occurs.

  As means for solving the electrical crosstalk problem, in Patent Document 1, trench grooves each having a depth reaching the vicinity of the n-type InP substrate from the upper surface of the window layer are provided between the light receiving elements. Since the light receiving elements are physically separated by the trench, carrier movement can be prevented and electrical crosstalk can be suppressed. Each trench groove may be embedded with a semiconductor material in order to prevent deterioration of the pn junction.

  Here, the optical crosstalk will be described based on the light receiving element array 21B of FIG. The light is guided to the optical fiber, condensed by the lens, and vertically incident on the light receiving element array 21B. However, a part of the light may be incident obliquely without being perpendicularly incident on the light receiving surface. . This obliquely incident light becomes leakage light if it is transmitted without being absorbed by the light receiving layer 24, and is reflected on the lower surface of the light receiving element and incident near the pn junction of the adjacent light receiving element, or the upper surface and the lower surface of the light receiving element. May be incident near the pn junction 31 of the adjacent light receiving element. Thus, the leaked light incident near the adjacent pn junction forms carriers of electron-hole pairs and generates a photocurrent. This is called optical crosstalk.

  For this reason, in the structure in which the trench groove is provided between the light receiving elements, even if the electrical crosstalk can be reduced, it cannot be said that the optical crosstalk is sufficiently suppressed. That is, when the leakage light repeats multiple reflections between the upper surface and the lower surface of the light receiving element, the trench groove is vertically elongated, so that the leakage light does not strike the trench groove but is incident on the adjacent pn junction. There is a possibility that. Even if light is incident perpendicularly to the light receiving surface, a part of the light is transmitted through the light receiving layer, is irregularly reflected at the boundary surface between the semiconductor substrate and the electrode, and the light is subjected to multiple reflections so that the pn of the adjacent light receiving element is obtained. In some cases, the light enters the vicinity of the junction.

  As means for solving the above optical crosstalk, a light receiving element array as disclosed in Patent Documents 2 and 3 is disclosed. That is, in Patent Document 2, a light absorbing layer is provided between the light receiving layer and the bottom of the light receiving element, and in Patent Document 3, a light absorbing layer is provided between the light receiving layer and the upper surface of the light receiving element. Since this light absorption layer is formed of a material having a band gap energy smaller than that of incident light, leakage light transmitted through the light receiving layer can be absorbed and attenuated, and optical crosstalk can be suppressed. .

JP 2001-144278 A JP 2005-251890 A JP 2005-259829 A

  However, in the optical crosstalk suppressing means described in Patent Documents 2 and 3, a process for growing a light absorption layer in addition to the conventional epistructure shown in FIGS. Necessary. Therefore, the manufacturing cost of the light receiving element array increases. Furthermore, since the light transmitted through the light receiving layer and incident on the light absorbing layer is converted into heat and photocurrent, there arises a problem that the characteristics of the light receiving element are deteriorated such as an increase in dark current and a decrease in response speed.

  The light receiving element array of Patent Document 3 has a structure in which a light absorption layer is grown on an InP window layer. However, when performing a process of forming a p-type region by general Zn diffusion, It is necessary to make the diffusion region deeper than before. For this reason, the p-type region expands in the horizontal direction. The enlargement of the p-type region causes a problem that the characteristics of the light receiving element are deteriorated, such as an increase in dark current and a decrease in response speed, as in the above problem.

  An object of the present invention is to provide a light receiving element array capable of suppressing optical crosstalk by additionally forming a V-shaped separation groove in a conventional epi structure.

  The light receiving element array according to claim 1 includes a first conductive type semiconductor substrate, a first conductive type light receiving layer formed on the surface side of the semiconductor substrate, and a first conductive type light receiving layer formed on the surface side of the light receiving layer. A plurality of second conductivity type regions formed in a state of penetrating to the surface side of the light receiving layer through the window layer and spaced apart as a one-dimensional or two-dimensional array, and A plurality of inter-array regions formed by a plurality of arrays of the plurality of second conductivity type regions in a light receiving element array having a plurality of first electrodes respectively provided on at least a part of the surface of the plurality of second conductive regions. In addition, a first separation groove having a V-shaped cross section opened at least on the surface side having a depth penetrating the window layer and the light receiving layer is provided.

  The light receiving element array according to claim 6 is a first conductive type semiconductor substrate, a first conductive type light receiving layer formed on the surface side of the semiconductor substrate, and a first conductive type light receiving layer formed on the surface side of the light receiving layer. A plurality of second conductivity type regions formed in a state of penetrating to the surface side of the light receiving layer through the window layer and spaced apart as a one-dimensional or two-dimensional array, and In a light receiving element array having a plurality of first electrodes respectively provided on at least a part of the surfaces of the plurality of second conductive regions, the plurality of first separation grooves having an inverted V-section opened to the back side of the semiconductor substrate It is characterized by providing each.

  According to the first aspect of the present invention, in the light receiving element array, a surface having a depth penetrating at least the window layer and the light receiving layer in a plurality of inter-array regions formed by the plurality of arrays of the plurality of second conductivity type regions. Since the first separation groove having a V-shaped cross section that is open on the side is provided, the first separation groove having the V-shaped cross section can be obtained even when obliquely incident light, leaked light that repeats multiple reflections, or irregularly reflected light is generated. The groove can efficiently reflect in the horizontal direction or the horizontal direction separated from the adjacent p-type region to reduce the incidence of leaked light to the adjacent pn junction, thereby suppressing optical crosstalk. can do.

  According to the sixth aspect of the present invention, in the light receiving element array, since the plurality of first V-shaped first separation grooves opened on the back surface side of the semiconductor substrate are provided, Even when obliquely incident light, leaky light that repeats multiple reflections, or diffused leaked light occurs, the light is efficiently reflected in the horizontal direction or the horizontal direction that is separated from the adjacent p-type region, and is adjacent. By reducing the light incident on the pn junction, optical crosstalk can be suppressed.

In addition to the above configuration of claim 1, the following various configurations may be adopted.
(1) A buffer layer of a first conductivity type is provided between the semiconductor substrate and the light receiving layer.
(2) One or more second electrodes are provided on the back surface of the semiconductor substrate.
(3) A second electrode is provided on the surface of each first separation groove.
(4) A slit-shaped second separation groove having a depth penetrating at least the window layer and the light-receiving layer is provided in a plurality of inter-array regions formed by a plurality of arrays composed of the plurality of second conductivity type regions, A second electrode is formed on the surface of these second separation grooves.

In addition to the above-described configuration of the sixth aspect, the following various configurations may be employed.
(5) A buffer layer of a first conductivity type is provided between the semiconductor substrate and the light receiving layer.
(6) A second electrode is formed on the back surface of the semiconductor substrate.
(7) Slit-like second separation grooves each having a depth penetrating the window layer and the light receiving layer are provided in a plurality of inter-array regions formed by a plurality of arrays composed of the plurality of second conductivity type regions. A second electrode is formed on the surface of the second separation groove.

3 is an enlarged cross-sectional view of a main part of the light receiving element array according to Embodiment 1. FIG. 6 is an enlarged cross-sectional view of a main part of a light receiving element array according to Embodiment 2. FIG. 6 is an enlarged cross-sectional view of a main part of a light receiving element array according to Example 3. FIG. 10 is an enlarged cross-sectional view of a main part of a light receiving element array according to Example 4. FIG. FIG. 10 is an enlarged cross-sectional view of a main part of a light receiving element array according to Example 5. 10 is an enlarged cross-sectional view of a main part of a light receiving element array according to Example 6. FIG. 10 is an enlarged cross-sectional view of a main part of a light receiving element array according to Example 7. FIG. It is a principal part expanded sectional view of the light receiving element array which concerns on a prior art example. It is a principal part expanded sectional view of the light receiving element array which concerns on a prior art example. It is explanatory drawing of optical crosstalk.

  Hereinafter, modes for carrying out the present invention will be described based on examples.

First, the overall structure of the light receiving element array 1 will be described.
As shown in FIG. 1, the light receiving element array 1 is applied to an application for receiving light of a plurality of wavelengths projected from an optical fiber for optical multiplex communication. This light receiving element array 1 is a top-incident type light receiving element array. The light receiving element array 1 includes an n-type InP semiconductor substrate 2 (first conductivity type semiconductor substrate) and an n-type InP buffer layer 3 (first conductivity type buffer layer) formed on the surface side of the semiconductor substrate 2. An n-type InGaAs light-receiving layer 4 (first-conductivity-type light-receiving layer) formed on the surface side of the buffer layer 3, and an n-type InP window layer 5 (first first-layer) formed on the surface side of the light-receiving layer 4. A plurality of p-type regions 6 (second conductivity type regions), a plurality of p-type electrodes 7 (first electrodes), and a common n-type electrode 8 ( A second electrode), a plurality of V-shaped first separation grooves 10 and the like.

  Note that the light receiving element array 1 in FIG. 1 only shows a part of the entire configuration, and may be a one-dimensional light receiving element array in which a plurality of light receiving elements are arranged one-dimensionally. A two-dimensional light receiving element array in which the light receiving elements are arranged in a matrix may be used. The number of light receiving elements is preferably a power of 2, such as 4, 8, 16,..., But is not particularly limited. In this embodiment, “n-type” corresponds to the first conductivity type, and “p-type” corresponds to the second conductivity type. Note that the light receiving element arrays 1A to 1F shown in FIG. 2 and subsequent figures also show only a part of the entire configuration, as in FIG.

  As shown in FIG. 1, the plurality of p-type regions 6 are formed so as to penetrate the window layer 5 and enter the surface side portion of the light receiving layer 4 and are separated as a one-dimensional or two-dimensional array arrangement. It is formed in a shape. The plurality of p-type regions 6 are each formed in a circular shape in plan view, but are not particularly limited to a circular shape, and may be formed in a square shape in plan view or a rectangular shape in plan view.

  A pn junction 11 is formed at the boundary between the p-type region 6 and the light receiving layer 4 and at the boundary between the p-type region 6 and the window layer 5. A depletion layer is formed in the vicinity of the pn junction 11, and light is incident on the depletion layer to generate carriers of electron-hole pairs.

  Each p-type electrode 7 is formed on a part of the surface of the p-type region 6. Each p-type electrode 7 is insulated from the window layer 5 by an antireflection film 12. The n-type electrode 8 is provided over the entire back surface of the semiconductor substrate 2.

  In order to reduce the surface reflection of the light receiving element array 1 and increase the transmittance, the antireflection film 12 and the window layer 5 and the remaining surface of the plurality of p-type regions 6 except for the plurality of p-type electrodes 7. And the surfaces of the plurality of first separation grooves 10 are provided.

  As shown in FIG. 1, the first separation groove 10 is formed in a V-shaped cross section, and is provided open on the surface side in a plurality of inter-array regions formed by a plurality of arrays composed of a plurality of p-type regions 6. ing. The first separation groove 10 is provided at a depth that reaches the semiconductor substrate 2 through the window layer 5, the light receiving layer 4, and the buffer layer 3 (a depth that is about ½ of the total thickness of the light receiving element array 1). ing. The apex angle of the first separation groove 10 is formed to be about 70 degrees. It is desirable that the first separation groove 10 has a depth that penetrates at least the window layer 5 and the light receiving layer 4, and in this case, optical crosstalk can be sufficiently suppressed. Further, the first separation groove 10 may be formed so as to be embedded with a semiconductor material.

Next, a method for manufacturing the light receiving element array 1 will be described.
First, the n-type InP buffer layer 3, the n-type InGaAs light receiving layer 4, and the n-type InP window layer 5 are successively grown on the n-type InP semiconductor substrate 2 in this order by MOCVD or the like. Next, a plurality of openings are formed on the n-type InP window layer 5 at a constant pitch one-dimensionally or two-dimensionally by photolithography. Then, Zn is diffused into each of the plurality of openings to form a plurality of p-type regions 6. At this time, the plurality of openings are formed so as to be arranged in a direction perpendicular to the (01-1) plane of the semiconductor crystal of the window layer 5.

  Next, in order to form the first separation groove 10 having a V-shaped cross section, an insulating film such as SiN is formed on the upper surface of the window layer by CVD or the like, and the first separation groove 10 is formed by photolithography and etching. The portion of the insulating film to be removed is removed. Thereafter, anisotropic wet etching is performed with a solution containing about several percent of bromine in methanol to form a first separation groove 10 having a V-shaped cross section.

  Next, the insulating film on the light receiving surface is removed by etching, and an insulating film such as SiN is formed by CVD or the like so that the film thickness becomes a non-reflective condition, and the antireflection film 12 is provided. Then, a p-type electrode 7 made of, for example, AuZn is formed so as to penetrate the antireflection film 12 on at least a part of the upper surface of the p-type region 6, and the entire back surface of the n-type InP semiconductor substrate 2 is made of, for example, AuGeNi. A common n-type electrode 8 is formed.

  Thus, since the window layer 5 on the upper side of the light receiving element array 1 is an n-type InP layer, the cross section V can be obtained by performing anisotropic wet etching using a solution containing about several percent of bromine in methanol. A first separation groove 10 of the mold can be formed. It is possible to perform the anisotropic wet etching as described above even with odorous acid or a solution in which hydrogen peroxide is mixed with odorous acid, but there is no particular limitation here.

  When the anisotropic wet etching is performed, the crystal facet differs depending on the plane index of the semiconductor substrate 2 and the etching solution used. When an etching solution containing about several percent bromine in methanol is used for the (100) plane InP layer, the groove width decreases in the depth direction with respect to the direction perpendicular to the (01-1) plane. Such a forward mesa surface is formed, and with respect to the direction perpendicular to the (0-1-1) plane, a reverse mesa surface is formed such that the groove width increases in the depth direction.

Next, the operation and effect of the light receiving element array 1 of the present invention will be described.
First, in this light receiving element array 1, a common n-type electrode 8 is connected to a positive electrode, a plurality of p-type electrodes 7 are connected to corresponding negative electrodes, and the light receiving element array 1 is connected so as to be in a reverse bias state. . In this state, a p-side depletion layer is formed on the p-type region 6 side, and an n-side depletion layer is formed on the light receiving layer 4 side.

  Next, when light is incident on the upper surface side of the light receiving element array 1, the light is incident on the depletion layer of the pn junction 11 through the antireflection film 12 and the p-type region 6. Hole pair carriers are generated. Then, a photocurrent is generated when holes generated mainly in the n-side depletion layer move to the p-type region 6.

  However, most of the light incident on the pn junction 11 is incident at an angle close to perpendicular to the light receiving surface (upper surface), but a part of the light may be incident obliquely. When this obliquely incident light passes through the light receiving layer 4 and becomes leakage light, it moves in the direction of the adjacent pn junction 11 while repeating multiple reflections between the upper surface and the lower surface of the light receiving element array 1. At this time, the first separation groove 10 having a V-shaped cross section is provided so as to penetrate the light receiving layer 4 between the pn junctions 11 of the light receiving element array 1. Is reflected in a horizontal direction or a horizontal direction that is separated from the adjacent p-type region 6 and re-enters the vicinity of the pn junction 11.

  Even if the light is incident perpendicular to the light receiving surface, a part of the light is transmitted without being absorbed by the light receiving layer 4 and becomes leaked light. This leaked light is the lower surface of the light receiving element array 1. May cause irregular reflection. At this time, the leaked light moves in the direction of the adjacent pn junction 11 while repeating multiple reflections between the upper surface and the lower surface of the light receiving element array 1, but the leaked light is leaked by the inclined surface of the first separation groove 10. The light is reflected substantially in the horizontal direction with respect to the incident direction, and is incident again on the vicinity of the pn junction 11.

  In this manner, in the light receiving element array 1, at least the surface side having a depth penetrating the window layer 5 and the light receiving layer 4 is opened to a plurality of inter-array regions formed by a plurality of p-type regions 6. Since the first V-shaped first separation grooves 10 are provided, even if the first V-shaped first separation grooves 10 generate obliquely incident light, multiple reflection leaked light, or irregularly reflected leak light. The optical crosstalk is suppressed by efficiently reflecting in the horizontal direction separated from the adjacent p-type region 6 in the horizontal direction or the horizontal direction close to the horizontal and reducing the incident of the leaked light to the adjacent pn junction 11. be able to.

  Further, since the first separation groove 10 is formed to a depth penetrating the light receiving layer 4, carriers generated in the depletion layer are prevented from moving to the adjacent pn junction 11 due to lateral diffusion, and are adjacent to each other. Electrical crosstalk with the pn junction 11 can be suppressed. A top-illuminated type light-receiving element array 1 in which a plurality of p-type electrodes 7 and a common n-type electrode 8 are formed on the opposing surface and a first separation groove 10 having a V-shaped cross section is formed on the top surface side can be provided. .

  In the following, various embodiments in which the light receiving element array 1 is partially changed and various embodiments in which these embodiments are partially changed will be described, but the same components as those in the preceding embodiments are described. The description will be omitted, and only different components will be described.

  As shown in FIG. 2, the light receiving element array 1 </ b> A of the present example is partially formed on the back surface of the semiconductor substrate 2 in place of the n-type electrode 8 provided on the entire back surface of the semiconductor substrate 2 of the first embodiment. An n-type electrode 8A is provided, and an insulating film 13 is formed on the remaining back surface of the semiconductor substrate 2 excluding the plurality of n-type electrodes 8A. Therefore, the leaked light that is incident from the upper surface and transmitted through the light receiving layer 4 is reflected in a horizontal direction or a horizontal direction that is separated from the adjacent p-type region 6 along the locus of the solid line shown in FIG. . In this case, the top-illuminated light-receiving element array 1 in which a plurality of p-type electrodes 7 and a plurality of n-type electrodes 8A are formed on the front and back facing surfaces and the first separation groove 10 having a V-shaped cross section is formed on the upper surface side. Can be provided.

  In this light receiving element array 1, an insulating film is formed instead of the antireflection film 12 on the upper surface of the p-type region 6 and the window layer 5, and an antireflection film is formed instead of the insulating film 13 on the back surface of the semiconductor substrate 2. By doing so, you may comprise the light receiving element array which can inject from a lower surface side. At this time, the leaked light that is incident from the lower surface and is not absorbed by the light receiving layer 4 is a horizontal direction or a horizontal direction that is separated from the adjacent p-type region 6 along the locus of the two-dot chain line shown in FIG. Reflected in the direction. In this case, it is possible to provide a bottom-illuminated type light receiving element array in which a first separation groove 10 having a V-shaped cross section is formed on the top surface side.

  As shown in FIG. 3, in the light receiving element array 1B of this embodiment, instead of the antireflection film 12 on the surface of each first separation groove 10 of the first embodiment, an n-type electrode 8B (V-shaped cross section) A second electrode) is provided. An antireflection film 12B is formed on the surface of the p-type region 6 excluding the p-type electrode 7 and on the surface of the window layer 5 excluding the n-type electrode 8B. An n-type electrode 8 is formed over the entire back surface of the semiconductor substrate 2 as in the first embodiment. Therefore, a top-surface incident type light receiving element array 1B is provided in which a plurality of p-type electrodes 7 and a plurality of n-type electrodes 8B are formed on the same surface side, and a first separation groove 10 having a V-shaped cross section is formed on the top surface side. be able to.

  In this light receiving element array 1B, an insulating film is formed in place of the antireflection film 12B on the upper surface of the p-type region 6 and the window layer 5, and the n-type electrode 8 on the entire back surface of the semiconductor substrate 2 is replaced or p-type. A light receiving element array that can be incident from the back surface side may be formed by forming an antireflection film instead of the n-type electrode 8 corresponding to the region 6. In this case, it is possible to provide a bottom-illuminated type light receiving element array in which a first separation groove 10 having a V-shaped cross section is formed on the top surface side.

  As shown in FIG. 4, in the light receiving element array 1 </ b> C of the present embodiment, the slit-shaped second separation having a depth penetrating the window layer 5, the light receiving layer 4, and the buffer layer 3 corresponding to the plurality of p-type regions 6. A groove 15 is formed, and an n-type electrode 8 </ b> C is formed on the surface of the slit-shaped second separation groove 15. The slit-shaped second separation groove 15 is formed in a C shape or a circular shape in plan view so as to surround the p-type region. An antireflection film 12C is formed on the surface of the first separation groove 10 and the window layer excluding the p-type region 6 and the n-type electrode 8C excluding the p-type electrode 7. An n-type electrode 8 is formed over the entire back surface of the semiconductor substrate 2 as in the first embodiment. Therefore, an upper surface in which a plurality of p-type electrodes 7 and a plurality of n-type electrodes 8C are formed on the same surface side, and a V-shaped first separation groove 10 and a slit-shaped second separation groove 15 are formed on the upper surface side. An incident type light receiving element array 1C can be provided.

  In this light receiving element array 1C, an insulating film is formed instead of the antireflection film 12C on the surface of the p-type region 6, the window layer 5 and the first separation groove 10, and the n-type electrode 8 on the entire back surface of the semiconductor substrate 2 is formed. Alternatively, an antireflection film may be formed instead of the n-type electrode 8 corresponding to the p-type region 6 to form a lower surface side light receiving element array that can enter from the lower surface side. In this case, it is possible to provide a bottom-illuminated type light receiving element array in which the first separation groove 10 having a V-shaped cross section and the second separation groove 15 having a slit shape are formed on the upper surface side.

First, the overall configuration of the light receiving element array 1D will be described.
As shown in FIG. 5, the light receiving element array 1D is a bottom surface incident type light receiving element array. The light receiving element array 1D includes an n-type InP semiconductor substrate 2, an n-type InP buffer layer 3 formed on the surface side of the semiconductor substrate 2, and an n-type InGaAs light-receiving layer formed on the surface side of the buffer layer 3. 4 and an n-type InP window layer 5 formed on the surface side of the light receiving layer 4 are sequentially laminated. A plurality of p-type regions 6, a plurality of p-type electrodes 7, a plurality of n-type electrodes 8 </ b> D, a plurality of inverted V-shaped first separation grooves 14, a plurality of slit-shaped second separation grooves 15, etc. Is provided.

  The plurality of p-type regions 6 are formed in a state of penetrating the window layer 5 and entering the surface side portion of the light receiving layer 4 and are formed in a spaced manner as a one-dimensional or two-dimensional array. The plurality of p-type electrodes 7 are respectively provided on at least a part of the surfaces of the plurality of p-type regions 6. The p-type electrode 7 is insulated from the window layer 5 by the insulating film 13D. A pn junction 11 is formed at each boundary between the plurality of p-type regions 6 and the light receiving layer 4. In this embodiment, the p-type electrode 7 is partially provided in the p-type region. However, the p-type electrode 7 may be provided over the entire surface of the p-type region 6 so as not to be in electrical contact with the window layer 5.

  The first separation groove 14 is formed in an inverted V-shaped cross section on the back side of a plurality of inter-array regions formed by a plurality of arrays composed of a plurality of p-type regions 6, and is provided open on the back side of the semiconductor substrate 2. ing. The apex angle of the first separation groove 14 is formed to be about 70 degrees. The antireflection film 12 </ b> D is provided over the entire back surface of the semiconductor substrate 2 including the back surfaces of the plurality of first separation grooves 14.

  The second separation groove 15 is formed in a slit shape. The second separation groove 15 is formed in a C-shape or a circular shape in plan view so as to surround the p-type region 6 in a plurality of inter-array regions formed by a plurality of arrays composed of the plurality of p-type regions 6. The second separation groove 15 is provided at a depth that penetrates the window layer 5, the light receiving layer 4, and the buffer layer 3. The n-type electrode 8D is formed in a U-shaped cross section on the surface of each second separation groove 15. An insulating film 13D is formed on the upper surface of the p-type region 6 excluding the p-type electrode 7 and the upper surface of the window layer 5 excluding the n-type electrode 8D. The second separation groove 15 desirably penetrates at least the window layer 5 and the light receiving layer 4. A structure in which a semiconductor material is embedded in the first and second separation grooves 14 and 15 may be employed.

Next, functions and effects of the light receiving element array 1D of the present invention will be described.
First, when light is incident on the lower surface side of the light receiving element array 1D in the reverse bias state, this light is transmitted through the antireflection film 12D, the semiconductor substrate 2, and the buffer layer 3, and is incident on the depletion layer of the pn junction 11. Then, carriers of electron-hole pairs are generated in this depletion layer. Then, a photocurrent is generated when holes generated mainly in the n-side depletion layer move to the p-type region 6.

  However, most of the light incident on the pn junction 11 is incident at an angle close to perpendicular to the light receiving surface (lower surface), but some of the light may be incident obliquely. When this obliquely incident light becomes leaked light without being absorbed by the light receiving layer 4, it moves in the direction of the adjacent pn junction 11 while repeating multiple reflections between the upper surface and the lower surface of the light receiving element array 1D. Since the first separation groove 14 having an inverted V-shaped cross section is provided between the pn junctions 11 of the light receiving element array 1D, the inclined surface of the first separation groove 14 causes a leak along a two-dot chain line shown in FIG. The light is reflected in the horizontal direction that is separated from the adjacent p-type region 6 or in the lateral direction close to the horizontal direction.

  Even when light is incident perpendicular to the light receiving surface, a part of the light is transmitted without being absorbed by the light receiving layer and becomes leaked light. This leaked light is reflected on the upper surface of the light receiving element array 1D. There is a possibility of irregular reflection. At this time, the leaked light moves in the direction of the adjacent pn junction 11 while repeating multiple reflection between the upper surface and the lower surface of the light receiving element array 1D. However, the leaked light is leaked by the inclined surface of the first separation groove 14. The light is reflected in the horizontal direction that is separated from the adjacent p-type region 6 or in the lateral direction close to the horizontal direction.

  As described above, in the light receiving element array 1D, the plurality of first V-shaped first separation grooves 14 opened on the back surface of the semiconductor substrate 2 are provided, so that light incident obliquely by the first separation grooves 14 is provided. The light that repeats multiple reflections in the vertical direction and the irregularly reflected leakage light are efficiently reflected in the horizontal direction or the horizontal direction that is separated from the adjacent p-type region 6, and the light incident on the adjacent pn junction 11 is reflected. By reducing it, optical crosstalk can be suppressed.

  In addition, the slit-shaped second separation groove 15 prevents carriers generated in the depletion layer from moving to the adjacent pn junction 11 due to lateral diffusion, thereby preventing electrical crosstalk between the adjacent pn junctions 11. Can be suppressed. Furthermore, it is possible to provide a bottom-illuminated light-receiving element array 1D in which the inverted V-shaped first separation groove 14 is formed on the bottom surface side.

Next, a modified example in which the fifth embodiment is partially modified will be described.
In the light receiving element array 1 </ b> D shown in FIG. 5, an n-type electrode is formed instead of the antireflection film 12 </ b> D on the entire back surface of the semiconductor substrate 2, and an antireflection film is substituted for the p-type region 6 and the insulating film 13 </ b> D on the upper surface of the window layer 5. By forming a film, a top-illuminated light-receiving element array that can be incident from the top surface side may be configured. At this time, the leaked light that is incident from the upper surface and transmitted through the light receiving layer 4 is reflected in the horizontal direction along the locus of the solid line shown in FIG. In this case, it is possible to provide a top-illuminated type light receiving element array in which the inverted first V-shaped separation groove 14 is formed on the lower surface side and the slit-shaped second separation groove 15 is formed on the upper surface side.

  As shown in FIG. 6, in the light receiving element array 1 </ b> E of the present embodiment, the plurality of first separation grooves 14 </ b> E are located below each pn junction 11 and open to the back side of the semiconductor substrate 2. Each is provided. An n-type electrode 18 is formed over the entire back surface of the semiconductor substrate 2 including the back surface of the first separation groove 14E, and the upper surface remaining of the p-type region 6 excluding the p-type electrode 7 and the upper surface of the window layer 5 excluding the n-type electrode 8D. An antireflection film 12E is formed in the remaining part. Other configurations are the same as those in the fifth embodiment. Therefore, it is possible to provide the top-illuminated type light receiving element array 1E in which the inverted V-shaped first separation grooves 14E are formed below the pn junction 11, respectively. The configuration in which the plurality of first separation grooves 14E are formed below the pn junctions 11 can be applied to the configurations of the following embodiments. Limited.

  As shown in FIG. 7, in the light receiving element array 1 </ b> F of the present embodiment, an antireflection film 12 </ b> F is partially formed in a portion corresponding to each p-type region 6 on the back surface of the semiconductor substrate 2. Instead of the n-type electrode 8D formed on the surface of the second separation groove 15, an n-type electrode 8F is provided on the remaining back surface of the semiconductor substrate 2 including the back surface of the plurality of first separation grooves 14 except for the antireflection film 12F. ing. The insulating film 13F is formed on the surface of the p-type region 6 excluding the p-type electrode 7, the surface of the window layer 5, and the surface of the second separation groove 15. Therefore, the bottom-illuminated light receiving element array 1F in which a plurality of p-type electrodes 7 and n-type electrodes 8F are formed on the opposing surface, the first separation groove 14 is formed on the lower surface side, and the second separation groove 15 is formed on the upper surface side. Can be provided.

  In this light receiving element array 1F, an n-type electrode is formed instead of the antireflection film 12F on the back surface side of the semiconductor substrate 2, and an insulating film 13F on the surface of the p-type region 6, the window layer 5, and the second separation groove 15 is formed. Alternatively, an antireflection film may be formed to constitute a light receiving element array that can be incident from the upper surface side. In this case, it is possible to provide an upper surface incident type light receiving element array in which the first separation groove 14 is formed on the lower surface side and the second separation groove 15 is formed on the upper surface side.

Here, the example which changes the said Example partially is demonstrated.
[1] In the above embodiment, a semi-insulating substrate (Si-InP substrate) can be adopted instead of the n-side InP semiconductor substrate. In this case, an n + type InP layer is formed instead of the n-side InP buffer layer.
[2] In the above embodiment, the first conductivity type is “n-type” and the second conductivity type is “p-type”. Conversely, the first conductivity type is “p-type”. The light receiving element array may be manufactured so that the second conductivity type is “n-type”.
[3] In addition, those skilled in the art can implement the present invention in various forms added with various modifications without departing from the spirit of the present invention, and the present invention includes such modifications. is there.

  The present invention can be used for various light receiving element arrays for optical communication, one-dimensional or two-dimensional sensors, and various light receiving element arrays used for other applications.

1, 1A to 1F Light receiving element array 2 Semiconductor substrate 3 Buffer layer 4 Light receiving layer 5 Window layer 6 p-type region 7 p-type electrode 8, 8A to 8D n-type electrode 10, 14, 14E First separation groove 11 pn junction 15 1st 2 separation grooves

Claims (9)

A first conductivity type semiconductor substrate, a first conductivity type light-receiving layer formed on the surface side of the semiconductor substrate, a first conductivity type window layer formed on the surface side of the light-receiving layer, and penetrating through the window layer A plurality of second conductivity type regions formed so as to protrude into the surface side of the light receiving layer and spaced apart as a one-dimensional or two-dimensional array, and the surfaces of the plurality of second conductive regions In a light receiving element array having a plurality of first electrodes provided at least in part,
A first separation groove having a V-shaped cross section opened to a surface side having a depth penetrating at least the window layer and the light receiving layer in a plurality of inter-array regions formed by a plurality of arrays of the plurality of second conductivity type regions. Respectively,
A light receiving element array.   The light receiving element array according to claim 1, wherein a buffer layer of a first conductivity type is provided between the semiconductor substrate and the light receiving layer.   The light receiving element array according to claim 1, wherein one or a plurality of second electrodes are provided on a back surface of the semiconductor substrate.   The light receiving element array according to claim 1, wherein a second electrode is provided on a surface of each of the first separation grooves.   A plurality of inter-array regions formed by the plurality of arrays of the plurality of second conductivity type regions are provided with slit-shaped second separation grooves each having a depth penetrating at least the window layer and the light-receiving layer. The light receiving element array according to claim 1, wherein a second electrode is formed on a surface of the two separation grooves. A first conductivity type semiconductor substrate, a first conductivity type light-receiving layer formed on the surface side of the semiconductor substrate, a first conductivity type window layer formed on the surface side of the light-receiving layer, and penetrating through the window layer A plurality of second conductivity type regions formed so as to protrude into the surface side of the light receiving layer and spaced apart as a one-dimensional or two-dimensional array, and the surfaces of the plurality of second conductive regions In a light receiving element array having a plurality of first electrodes provided at least in part,
A plurality of first V-shaped first separation grooves opened on the back side of the semiconductor substrate,
A light receiving element array.   The light receiving element array according to claim 6, wherein a buffer layer of a first conductivity type is provided between the semiconductor substrate and the light receiving layer.   The light receiving element array according to claim 6 or 7, wherein a second electrode is formed on a back surface of the semiconductor substrate.   Slit-like second separation grooves each having a depth penetrating the window layer and the light-receiving layer are provided in a plurality of inter-array regions formed by a plurality of arrays of the plurality of second conductivity type regions, respectively. The light receiving element array according to claim 6 or 7, wherein a second electrode is formed on a surface of the separation groove.