Semiconductor light receiving element

Abstract

A semiconductor light-receiving element (1) is provided with: a surface (1a) on which light is incident; a first semiconductor layer (21) of a first conductivity type; a second semiconductor layer (22) of the first conductivity type, which is laminated on the first semiconductor layer (21) on the surface (1a) side of the first semiconductor layer (21), and which has a band gap energy greater than the band gap energy of the first semiconductor layer (21); and a doped region (30) that is formed so as to extend from the surface (1a) toward the second semiconductor layer (22) and reach at least the inside of the second semiconductor layer (22), and that has a second conductivity type different from the first conductivity type. The thickness (T22) of the second semiconductor layer (22) in a first direction (Z) intersecting the surface (1a) is smaller than the thickness of the first semiconductor layer (21) in the first direction (Z), the doped region (30) includes a plurality of portions (31) facing each other with a gap (30 g) therebetween when viewed from the first direction (Z), and the width (G30) of the gap (30 g) is larger than the thickness (T22) of the second semiconductor layer (22) in the first direction (Z).

Description

Technical Field

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

[0002] Patent document 1 describes a light receiving element. The light receiving element includes: a light absorbing layer that absorbs incident light and converts it into an electrical signal; a covering layer formed on the light incident side of the light absorbing layer and having an energy band gap larger than that of the light absorbing layer; and a contact layer formed around the light receiving surface of the covering layer and made of the same material as the light absorbing layer and thicker than the covering layer. In addition, in the light receiving element, a P is formed by doping impurities at a high concentration near the interface between the light absorbing layer and the covering layer, and in the covering layer and the contact layer. + type of high impurity concentration region.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2001-177142 Summary of the invention

[0006] Problems to be solved by the invention

[0007] In the light receiving element described in Patent Document 1, a high-concentration impurity region is formed over the entire light receiving surface in the light absorbing layer and the cover layer. In this case, light of a wavelength absorbed in the high-concentration impurity region is not extracted as a signal, so there is a concern that loss will occur and sensitivity will decrease.

[0008] An object of the present invention is to provide a semiconductor light-receiving element capable of suppressing a decrease in sensitivity.

[0009] Technical means of solving problems

[0010] The semiconductor light-receiving element of the present invention is [1] "a semiconductor light-receiving element, comprising: a surface for receiving incident light; a first semiconductor layer of a first conductivity type; a second semiconductor layer of the first conductivity type stacked on the first semiconductor layer on the surface side of the first semiconductor layer and having a band gap energy greater than that of the first semiconductor layer; and an impurity doped region of a second conductivity type different from the first conductivity type formed in a manner extending from the surface toward the second semiconductor layer and at least reaching the interior of the second semiconductor layer, wherein the thickness of the second semiconductor layer in a first direction intersecting the surface is thinner than the thickness of the first semiconductor layer in the first direction, and the impurity doped region, as viewed from the first direction, includes a plurality of portions facing each other with a gap therebetween, and the width of the gap is greater than the thickness of the second semiconductor layer in the first direction".

[0011] In the semiconductor light-receiving element of the above-mentioned [1], a second semiconductor layer of the first conductive type having a large band gap energy is stacked on a first semiconductor layer of the first conductive type, and a doped region of the second conductive type extending from the surface receiving incident light toward the second semiconductor layer is formed. Moreover, the doped region includes a plurality of portions facing each other across a gap when viewed from a first direction intersecting the surface. Therefore, light incident on the gap of the doped region can be taken out as a signal without being absorbed in the doped region. Therefore, a decrease in sensitivity is suppressed. In particular, according to the understanding of the inventors of the present invention, if the width of the gap is greater than the thickness of the second semiconductor layer, the decrease in sensitivity can be further suppressed.

[0012] The semiconductor light-receiving element of the present invention may also be [2] "a semiconductor light-receiving element as described in [1] above, wherein the above-mentioned multiple parts of the above-mentioned doping region include at least one pair of extension parts extending in the same direction when viewed from the above-mentioned first direction, and the width of the above-mentioned gap is the interval between the above-mentioned pair of extension parts". According to the semiconductor light-receiving element of [2], a structure that can suppress the decrease in sensitivity can be easily and reliably constructed.

[0013] The semiconductor light-receiving element of the present invention may also be [3] "a semiconductor light-receiving element as described in [1] or [2] above, wherein the doped region extends from the second semiconductor layer toward the first semiconductor layer and reaches the interior of the first semiconductor layer." According to the semiconductor light-receiving element of [3], the doped region may also be constructed in this way.

[0014] The semiconductor light receiving element of the present invention may also be [4] "a semiconductor light receiving element as described in any one of the above [1] to [3], wherein a recess is formed on the surface, and a light receiving portion is formed in an area overlapping with the bottom surface of the recess when viewed from the first direction." According to the semiconductor light receiving element [4], the area corresponding to the bottom surface of the recess is used as the light receiving portion. Thus, the light receiving portion is protected from contact and is not easily damaged.

[0015] The semiconductor light receiving element of the present invention may also be [5] "a semiconductor light receiving element as described in [4] above, wherein the doped region is exposed on the side of the recess". According to the semiconductor light receiving element of [5], light incident on the gap between the portion of the doped region exposed on the side of the recess and the portion opposite to the portion can also be extracted as a signal. As a result, the decrease in sensitivity can be more reliably suppressed. In addition, in this case, the doped region includes a portion formed from the side of the recess to the top surface of the recess (the region of the predetermined recess on the surface). Compared with the portion of the doped region formed on the bottom side of the recess, this portion has a thicker portion with a higher impurity concentration on the surface side. Therefore, contact with the electrode can be achieved in this portion and the contact resistance can be reduced.

[0016] The semiconductor light-receiving element of the present invention may also be [6] "a semiconductor light-receiving element as described in any one of [1] to [5] above, comprising a third semiconductor layer of the first conductive type stacked on the second semiconductor layer on the surface side of the second semiconductor layer". According to the semiconductor light-receiving element [6], by using a material having a larger band gap energy than the first semiconductor layer and the third semiconductor layer as the second semiconductor layer, dark current and absorption can be reduced, thereby achieving further reduction in loss.

[0017] The semiconductor light-receiving element of the present invention may also be [7] "a semiconductor light-receiving element as described in [6] above, wherein the semiconductor light-receiving element comprises a fourth semiconductor layer of the first conductive type stacked on the third semiconductor layer on the surface side of the third semiconductor layer". According to the semiconductor light-receiving element of [7], since the fourth semiconductor layer has the function of protecting the third semiconductor layer, the material of the third semiconductor layer can be selected from materials including materials that are relatively easy to oxidize such as aluminum, etc., thereby increasing the freedom of material selection for the third semiconductor layer.

[0018] The semiconductor light-receiving element of the present invention may also be [8] "a semiconductor light-receiving element as described in any one of [1] to [7] above, wherein the first semiconductor layer contains InGaAs and the second semiconductor layer contains InP or InAsP".

[0019] The semiconductor light-receiving element of the present invention may also be [9] "a semiconductor light-receiving element as described in [6] or [7] above, wherein the first semiconductor layer contains InAsSb or InAs, the second semiconductor layer contains AlInAsSb, and the third semiconductor layer contains InAsSb or InPSb".

[0020] The semiconductor light-receiving element of the present invention may also be

[10] "a semiconductor light-receiving element as described in [7] above, wherein the first semiconductor layer contains InGaAs, the second semiconductor layer contains InP or InAsP, the third semiconductor layer contains InGaAs, and the fourth semiconductor layer contains InP or InAsP".

[0021] Effects of the Invention

[0022] According to the present invention, it is possible to provide a semiconductor light-receiving element capable of suppressing a decrease in sensitivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram showing the semiconductor light-receiving element of this embodiment.

[0024] Figure 2 Yes means Figure 1The diagram shows the operation of the semiconductor light receiving element.

[0025] Figure 3 This is a diagram showing one process of a method for manufacturing a semiconductor light-receiving element.

[0026] Figure 4 This is a diagram showing one process of a method for manufacturing a semiconductor light-receiving element.

[0027] Figure 5 This is a diagram showing one process of a method for manufacturing a semiconductor light-receiving element.

[0028] Figure 6 It is a schematic cross-sectional view of a semiconductor light-receiving element according to a modified example.

[0029] Figure 7 It is a schematic top view of a semiconductor light-receiving element according to a modified example.

[0030] Figure 8 It is a schematic top view of a semiconductor light-receiving element according to a modified example. DETAILED DESCRIPTION

[0031] Hereinafter, a semiconductor light-receiving element according to an embodiment will be described with reference to the accompanying drawings. In the description of each figure, the same symbols are sometimes used to mark the same or equivalent elements, and repeated descriptions are omitted. In addition, in each figure, a rectangular coordinate system defined by the X-axis, Y-axis, and Z-axis is sometimes illustrated.

[0032] Figure 1 It is a schematic diagram showing the semiconductor light-receiving element of this embodiment. Figure 1 (a) is a top view, Figure 1 (b) is along Figure 1 The cross-sectional view of the Ib-Ib line. Figure 1 As shown, the semiconductor light receiving element 1 includes a first semiconductor portion 10, a second semiconductor portion 20, electrodes 41, 42, and a protective film F. The semiconductor light receiving element 1 has a surface 1a and a back surface 1b on the opposite side of the surface 1a. In the semiconductor light receiving element 1, for example, the surface 1a is a light incident surface. The first semiconductor portion 10 includes the back surface 1b, and the second semiconductor portion 20 includes the surface 1a. That is, the second semiconductor portion 20 is stacked on the first semiconductor portion 10 on the surface 1a side.

[0033] The first semiconductor portion 10 includes a plurality of semiconductor layers stacked along a first direction (here, the Z-axis direction) intersecting the surface 1a. The plurality of semiconductor layers include, for example, a substrate (not shown), a buffer layer (not shown), and a light absorbing layer (first semiconductor layer) 21 stacked in order from the back surface 1b side.

[0034] The substrate is, for example, made of a first conductivity type (eg, n +The buffer layer is composed of, for example, InP of the first conductivity type (e.g., n + The buffer layer 21 is composed of InP of the first conductivity type (e.g., n-type or n-type). As an example, the buffer layer has a thickness of about 0.5 μm to 2.0 μm in the first direction. The light absorption layer 21 contains, for example, InGaAs of the first conductivity type (composed of InGaAs). As an example, the light absorption layer 21 has a thickness of about 1.5 μm to 5 μm in the first direction.

[0035] The second semiconductor portion 20 includes a first covering layer (second semiconductor layer) 22, a semiconductor layer (third semiconductor layer) 23, and a second covering layer (fourth semiconductor layer) 24, which are sequentially stacked along the first direction from the first semiconductor portion 10 side. The first covering layer 22 is stacked on the light absorbing layer 21 on the surface 1a side of the light absorbing layer 21, and has an interface with the light absorbing layer 21. The semiconductor layer 23 is stacked on the first covering layer 22 on the surface 1a side of the first covering layer 22, and has an interface with the first covering layer 22. The second covering layer 24 is stacked on the semiconductor layer 23 on the surface 1a side of the semiconductor layer 23, and has an interface with the semiconductor layer 23.

[0036] The first cladding layer 22 has a band gap energy greater than the band gap energy of the light absorbing layer 21 and the semiconductor layer 23. The first cladding layer 22, for example, includes InP (composed of InP) of the first conductivity type (for example, n-type). As an example, the first cladding layer 22 has a thickness T22 of about 0.1 μm in the first direction. The thickness T22 of the first cladding layer 22 in the first direction is thinner than the thickness of the light absorbing layer 21 in the first direction. The semiconductor layer 23, for example, includes InGaAs (composed of InGaAs) of the first conductivity type (for example, n-type). As an example, the semiconductor layer 23 has a thickness of about 0.05 μm to 0.3 μm in the first direction. The second cladding layer 24, for example, includes InP (composed of InP) of the first conductivity type (for example, n-type). As an example, the second cladding layer 24 has a thickness of about 0.2 μm to 2.0 μm in the first direction.

[0037] Here, a recess 50 is formed on the surface 1a. As an example, the surface 1a is circular when viewed from the first direction (that is, the outer shape of the semiconductor light receiving element 1 is circular), and the recess 50 is a circle concentric with the surface 1a when viewed from the first direction. The recess 50 has a bottom surface 50i and a side surface 50s connecting the bottom surface 50i and the surface 1a. The recess 50 penetrates the second covering layer 24 and the semiconductor layer 23. Therefore, at the bottom surface 50i of the recess 50, the first covering layer 22 is exposed (that is, the surface of the first covering layer 22 constitutes the bottom surface 50i).

[0038] In other words, the first semiconductor portion 10 and the second semiconductor portion 20 have a first region A overlapping with the bottom surface 50i of the recess 50 as viewed from the first direction and a second region B outside the first region A, and the semiconductor layer 23 and the second cover layer 24 are formed only in the second region B outside the recess 50. In the semiconductor light receiving element 1, the first region A overlapping with the bottom surface 50i of the recess 50 as viewed from the first direction is relatively thin and serves as a light receiving portion 55 that receives incident light and generates an electrical signal.

[0039] The protective film F is provided in a manner covering the surface 1a, the side surface 50s of the recess 50, and the bottom surface 50i of the recess 50. The protective film F may also function as an anti-reflection film. In the protective film F, a through hole Fh is formed in the second region B, and the second cover layer 24 is exposed from the through hole Fh. The electrode 41 is formed on the back surface 1b and is in contact with the first semiconductor portion 10 (e.g., substrate). The electrode 42 is formed on the protective film F and is in contact with the second cover layer 24 via the through hole Fh.

[0040] The semiconductor light receiving element 1 has a doped region 30. The doped region 30 is formed as a region of the second conductivity type (e.g., p-type) by doping impurities (e.g., Zn) in the second semiconductor portion 20 and the first semiconductor portion 10. The doped region 30 can be, for example, a diffusion region formed by doping impurities from the surface 1a side using thermal diffusion. Alternatively, the doped region 30 can also be formed by doping impurities by ion implantation. The doped region 30 is formed in a manner extending from the surface 1a to the first covering layer 22 side and reaching at least the inside of the first covering layer 22. Here, the doped region 30 extends from the first covering layer 22 to the light absorbing layer 21 side and reaches the inside of the light absorbing layer 21.

[0041] More specifically, the doped region 30 is formed in the first region A on a portion of the first covering layer 22 and the light absorbing layer 21 on the first covering layer 22 side, and in the second region B on a portion of the second covering layer 24, the semiconductor layer 23, the first covering layer 22, and the light absorbing layer 21 on the first covering layer 22 side. The through hole Fh of the protective film F is formed on the doped region 30, and the electrode 42 is in contact with the doped region 30 in the second covering layer 24 (is electrically connected to the doped region 30).

[0042] The doping region 30 includes a plurality of portions 31 that are opposite to each other when viewed from the first direction. A gap 30g is interposed between the portions 31 that are opposite to each other. The width G30 of the gap 30g is greater than the thickness T22 of the first covering layer 22. The plurality of portions 31 include a group (at least one pair) of first extension portions 31a that extend in the same direction and another group (at least one pair) of second extension portions 31b that extend in the same direction in a direction different from the first extension portions 31a. Here, the first extension portion 31a extends in the X-axis direction, and the second extension portion 31b extends in the Y-axis direction.

[0043] The gap 30g is a gap between the first extension parts 31a adjacent to each other and a gap between the second extension parts 31b adjacent to each other. In addition, here, the width of the gap between the first extension parts 31a and the width of the gap between the second extension parts 31b are substantially the same, but when they are different from each other, the smaller one of them can be made larger than the thickness T22 of the first covering layer 22 as the width G30. In addition, when the width G30 changes along the extension direction of the first extension part 31a or the second extension part 31b, its minimum value or average value can be made larger than the thickness T22.

[0044] The first extension portion 31a and the second extension portion 31b are arranged in a lattice shape by crossing each other. The first extension portion 31a and the second extension portion 31b are connected to the outer edge portion 32 of the doped region 30 at both ends in their respective extension directions and are integrated. Here, the electrode 42 is provided in contact with the outer edge portion 32, and the first extension portion 31a and the second extension portion 31b are also electrically connected to the electrode 42.

[0045] The outer edge portion 32 is formed across the boundary between the first region A and the second region B. That is, the outer edge portion 32 includes a relatively thick portion located outside the recess 50 and a relatively thin portion located inside the recess 50. Thus, the outer edge portion 32 is exposed at the side surface 50s of the recess 50 (constituting the side surface 50s). That is, the doped region 30 is exposed at the side surface 50s of the recess 50.

[0046] Thus, in the semiconductor light-receiving element 1, the doped region 30 includes a plurality of portions 31 of the second conductivity type that are opposed to each other across the gap 30g when viewed from the first direction, and thus, PDs (Photo Diodes) are formed between each of the plurality of portions 31 and the semiconductor regions of the first conductivity type (mainly the light-absorbing layer 21 and the first covering layer 22) that are adjacent to each of the plurality of portions 31. Therefore, in the semiconductor light-receiving element 1, PDs are formed in the first direction for each of the plurality of portions 31, and a plurality of PDs are also formed and dispersedly arranged in a plane intersecting the first direction.

[0047] In the semiconductor light receiving element 1 as described above, Figure 2 As shown, when a voltage is applied to the electrodes 41 and 42, an electric field EF is formed in the first semiconductor portion 10 and the second semiconductor portion 20. In this state, when a certain light L1 is incident on a portion 31 of the doped region 30 and is absorbed, the light L1 cannot be taken out as a signal because an electric field is not applied to the doped region 30. On the other hand, when another light L2 is not absorbed by the doped region 30 but absorbed by the light absorbing layer 21, it is taken out as a signal because an electric field is applied.

[0048] Furthermore, when another light L3 is incident between the portions 31 of the doped region 30 (e.g., the gap 30g), that is, when it is absorbed by the first covering layer 22, the PD formed in the plane intersecting the first direction is absorbed by the portion 31 and the first covering layer 22 and is taken out as a signal. Furthermore, when the light L3 is incident between the portions 31 of the doped region 30, that is, when it is absorbed by the light absorbing layer 21, the PD formed in the first direction is absorbed by the portion 31 and the light absorbing layer 21 and is taken out as a signal. In this way, in the semiconductor light receiving element 1, the light absorbed by the first covering layer 22, which has not been taken out as a signal, can also be taken out as a signal.

[0049] Next, a method for manufacturing the semiconductor light-receiving element 1 will be described. Figures 3 to 5 FIG. 1 is a diagram showing a process of a method for manufacturing a semiconductor light-receiving element. In the method, Figure 3 As shown in (a), first, the doped region 30 is formed in the first semiconductor portion 10 and the second semiconductor portion 20. In the case where the doped region 30 is formed by thermal diffusion, first, after forming a first mask having an opening corresponding to the pattern of the doped region 30 on the surface 1a of the second semiconductor portion 20, impurities are doped to form the doped region 30 in the first semiconductor portion 10 and the second semiconductor portion 20. Thereafter, the first mask is removed.

[0050] Then, if Figure 3 As shown in (b), a second mask M for etching is formed on the surface 1a. Then, as Figure 4 As shown in (a) of FIG. 1 , a recess 50 is formed on the surface 1 a by etching using the second mask M. More specifically, first, the second cover layer 24 is selectively etched and removed using the second mask M. Then, the semiconductor layer 23 is selectively etched and removed using the second mask M.

[0051] Thus, the concave portion 50 is formed in such a manner that the first covering layer 22 is exposed in the region exposed from the second mask M, and a relatively thin portion 31 of the doped region 30 is formed. In addition, in the region covered by the second mask M, the semiconductor layer 23, the second covering layer 24, and a portion of the relatively thick outer edge portion 32 of the doped region 30 remain. In this way, the semiconductor layer 23 can be selectively etched in such a manner that only the relatively thin first covering layer 22 remains in the concave portion 50 as a covering layer on the light absorbing layer 21. Thereafter, as shown in FIG. Figure 4 As shown in (b), the second mask M is removed.

[0052] Then, if Figure 5 As shown in (a) of FIG. 5 , a protective film F is formed so as to cover the surface 1a, the side surface 50s of the recess 50, and the bottom surface 50i of the recess 50. Then, as shown in FIG. Figure 5As shown in (b), a through hole Fh is formed in the protective film F, and an electrode 42 is provided so as to be in contact with the doped region 30 via the through hole Fh. Together with this, an electrode 41 is provided on the back surface 1b. Thus, the semiconductor light receiving element 1 is obtained.

[0053] As described above, in the semiconductor light receiving element 1, the first conductive type light absorbing layer 21 is stacked with the first conductive type first covering layer 22 having a large band gap energy, and the second conductive type doping region 30 is formed from the surface 1a receiving the incident light to the first covering layer 22 side. Furthermore, the doping region 30 includes a plurality of portions 31 opposite to each other across the gap 30g as viewed from the first direction intersecting the surface 1a. Therefore, light incident on the gap 30g of the doping region 30 can be taken out as a signal without being absorbed in the doping region 30. Therefore, a decrease in sensitivity is suppressed. In particular, according to the knowledge of the inventors of the present invention, when the width of the gap 30g is greater than the thickness T22 of the first covering layer 22, a decrease in sensitivity can be further suppressed.

[0054] Furthermore, in the semiconductor light-receiving element 1, the plurality of portions 31 of the doped region 30 include at least one pair of first extension portions 31a (and second extension portions 31b (hereinafter the same)) extending in the same direction when viewed from the first direction, and the width of the gap 30g is the interval between the pair of first extension portions 31a. Thus, a structure capable of suppressing a decrease in sensitivity can be easily and reliably formed.

[0055] Furthermore, in the semiconductor light receiving element 1, the doped region 30 extends from the first cladding layer 22 toward the light absorbing layer 21 and reaches the inside of the light absorbing layer 21. In the semiconductor light receiving element 1, the doped region 30 may also be configured in this way.

[0056] In the semiconductor light receiving element 1, the recess 50 is formed on the surface 1a, and the light receiving portion 55 is formed in a region overlapping with the bottom surface 50i of the recess 50 as viewed from the first direction. Thus, the light receiving portion 55 can be protected from contact and is not easily damaged.

[0057] In addition, in the semiconductor light receiving element 1, the doped region 30 is exposed on the side 50s of the recess 50, so the light incident on the gap between the portion of the doped region 30 exposed on the side 50s of the recess 50 (here, the outer edge portion 32) and the portion 31 opposite to the portion can also be taken out as a signal. As a result, the decrease in sensitivity can be more reliably suppressed. In addition, the doped region 30 includes a portion (the above-mentioned relatively thick portion in the outer edge portion 32) formed from the side 50s of the recess 50 to the top surface of the recess 50 (the region of the predetermined recess 50 on the surface 1a). Compared with the portion 31 of the doped region 30 formed on the bottom surface 50i side of the recess 50, the portion has a thicker portion with a higher impurity concentration on the surface 1a side. Therefore, the contact resistance can be reduced by obtaining contact with the electrode 42 at this portion.

[0058] In addition, the semiconductor light-receiving element 1 includes a first conductive type semiconductor layer 23 stacked on the first covering layer 22 on the surface 1a side of the first covering layer 22. Therefore, by using a material having a larger band gap energy than the light-absorbing layer 21 and the semiconductor layer 23 as the first covering layer 22, dark current and absorption can be reduced, thereby achieving further reduction in loss.

[0059] In addition, the semiconductor light-receiving element 1 includes a second cover layer 24 of the first conductivity type stacked on the semiconductor layer 23 on the surface 1a side of the semiconductor layer 23. Therefore, the second cover layer 24 has a function of protecting the semiconductor layer 23, so as the material of the semiconductor layer 23, for example, a material including a material that is relatively easy to oxidize such as aluminum can be selected, and the freedom of material selection for the semiconductor layer 23 is improved.

[0060] The above embodiment describes one aspect of the present invention. Therefore, the semiconductor light receiving element of the present invention may be an element obtained by arbitrarily modifying the above-mentioned semiconductor light receiving element 1. Next, modification examples will be described.

[0061] [First Modification]

[0062] Figure 6 (a) is a schematic cross-sectional view showing a semiconductor light-receiving element 1A according to a first modification. Figure 6 The semiconductor light receiving element 1A shown in (a) has a second semiconductor portion 20A instead of the second semiconductor portion 20 , which is different from the semiconductor light receiving element 1 . The second semiconductor portion 20A includes only a single cover layer (second semiconductor layer) 25 , which is different from the second semiconductor portion 20 .

[0063] The covering layer 25 is stacked on the light absorbing layer 21 on the surface 1a side of the light absorbing layer 21, and has an interface with the light absorbing layer 21. The covering layer 25 contains InP (composed of InP) of the first conductivity type (e.g., n-type). In the semiconductor light receiving element 1A, the doped region 30 is also formed in a manner extending from the surface 1a to the covering layer 25 side and at least reaching the inside of the covering layer 25. More specifically, the doped region 30 extends from the covering layer 25 to the light absorbing layer 21 side and reaches the inside of the light absorbing layer 21. In this way, in the semiconductor light receiving element 1A, the semiconductor layer 23 and the second covering layer 24 may not be provided on the light absorbing layer 21. According to such a semiconductor light receiving element 1A, the same effect as that of the semiconductor light receiving element 1 can be achieved, and the semiconductor stacking structure on the light absorbing layer 21 is simplified. In addition, according to the semiconductor light receiving element 1A, by etching under time control, etc., it is possible to perform etching even in a material that is difficult to selectively etch, and it is possible to thin film without depending on the material. In this case, the width G30 of the gap 30 g can be set larger than the thickness of the relatively thin portion of the cover layer 25 located in the recess 50 .

[0064] [Second Modification]

[0065] Figure 6 (b) is a schematic cross-sectional view showing a semiconductor light-receiving element 1B according to a second modification. Figure 6 The semiconductor light-receiving element 1B shown in (b) is different from the semiconductor light-receiving element 1 in that it has a second semiconductor portion 20B instead of the second semiconductor portion 20 and in the materials of each layer. The second semiconductor portion 20B has a single covering layer (second semiconductor layer) 26 instead of the first covering layer 22 and a semiconductor layer (third semiconductor layer) 27 instead of the semiconductor layer 23, which are different from the second semiconductor portion 20.

[0066] In the semiconductor light receiving element 1B, the material of the first semiconductor portion 10 includes InAsSb. More specifically, in the semiconductor light receiving element 1B, at least the light absorbing layer 21 includes a first conductivity type (e.g., n-type and n-type). + The cover layer 26 is stacked on the light absorbing layer 21 on the surface 1a side and has an interface with the light absorbing layer 21. The cover layer 26 contains AlInAsSb (composed of AlInAsSb) of the first conductivity type (e.g., n-type). In addition, the semiconductor layer 27 contains InAsSb (composed of InAsSb) of the first conductivity type (e.g., n-type).

[0067] In the semiconductor light receiving element 1B, the doped region 30 is also formed in a manner extending from the surface 1a to the cover layer 26 side and at least reaching the inside of the cover layer 26. More specifically, the doped region 30 extends from the cover layer 26 to the light absorbing layer 21 side and reaches the inside of the light absorbing layer 21. In this way, in the semiconductor light receiving element 1B, it is also possible not to have the second cover layer 24 on the light absorbing layer 21. In this case, the same effect as the semiconductor light receiving element 1 can be achieved, and the semiconductor stacking structure on the light absorbing layer 21 is simplified. According to such a semiconductor light receiving element 1B, the same effect as the semiconductor light receiving element 1 can also be achieved, and the semiconductor stacking structure on the light absorbing layer 21 is simplified. In addition, according to the semiconductor light receiving element 1B, in the case where there is a material that can be selectively etched and has a wide band gap, the cover layer itself can be omitted. As a result, the loss in the light receiving portion can be reduced, and the contact resistance can be reduced by using a material that narrows the band gap at the contact portion of the cover layer.

[0068] [Third Modification]

[0069] Figure 7 (a) is a schematic plan view showing a semiconductor light receiving element 1C according to a third modification. Figure 7 The semiconductor light receiving element 1C shown in (a) is different from the semiconductor light receiving element 1 in the shape of the doped region 30 when viewed from the first direction.

[0070] In the semiconductor light receiving element 1C, the plurality of portions 31 of the doped region 30 have a third extension portion 31c extending in a circular ring shape when viewed from the first direction. The third extension portion 31c is in a circular ring shape concentric with the outer edge portion 32 when viewed from the first direction. Therefore, here, the third extension portion 31c and the outer edge portion 32 constitute a pair of extension portions extending in the same direction (circumferential direction). Therefore, a gap 30g is formed between the third extension portion 31c and the outer edge portion 32, and at least the width G30 (radial dimension) of the gap 30g is greater than the thickness T22 of the first covering layer 22.

[0071] In addition, in the semiconductor light-receiving element 1C, the plurality of portions 31 of the doped region 30 include a fourth extension portion 31d extending in one direction (here, the X-axis direction) intersecting the first direction and a fifth extension portion 31e extending in another direction (here, the Y-axis direction) intersecting the first direction. The fourth extension portion 31d and the fifth extension portion 31e intersect each other. Here, the intersection of the fourth extension portion 31d and the fifth extension portion 31e is substantially consistent with the center of the third extension portion 31c and the outer edge portion 32. The fourth extension portion 31d and the fifth extension portion 31e are connected to the outer edge portion 32 at both ends in their respective extension directions. In addition, the third extension portion 31c is connected to the outer edge portion 32 via the fourth extension portion 31d and the fifth extension portion 31e by connecting to them.

[0072] The width of the gap between the fourth extension portion 31d and the fifth extension portion 31e, that is, the width of the region surrounded by the fourth extension portion 31d, the fifth extension portion 31e, and the third extension portion 31c, varies at each position in the plane intersecting the first direction, but as an example, the average value thereof may be larger than the thickness T22. According to such a semiconductor light receiving element 1C, the same effect as that of the semiconductor light receiving element 1 can be achieved. In addition, according to the semiconductor light receiving element 1C, a design having a slit (gap 30g) in a circular shape can be easily performed, and a design that maximizes the relationship between the doped region 30 and the slit by combination can also be performed.

[0073] [Fourth Modification]

[0074] Figure 7 (b) is a schematic plan view showing a semiconductor light receiving element 1D according to a fourth modification. Figure 7 The semiconductor light receiving element 1D shown in (b) is different from the semiconductor light receiving element 1 in that it has a rectangular outer shape when viewed from the first direction and in the shape of the doped region 30 when viewed from the first direction.

[0075] In the semiconductor light receiving element 1D, the plurality of portions 31 of the doped region 30 include a pair of sixth extension portions 31f extending in a direction (here, the Y-axis direction) intersecting the first direction. The sixth extension portions 31f extend in the same direction as each other. Therefore, a gap 30g is formed between the sixth extension portions 31f, and at least the width G30 of the gap 30g is greater than the thickness T22 of the first covering layer 22. In addition, in the semiconductor light receiving element 1D, a pair of outer edge portions 32 also extend in the same direction as the sixth extension portion 31f. Therefore, the gap between one outer edge portion 32 and the sixth extension portion 31f adjacent to the one outer edge portion 32 can also be greater than the thickness T22 as the gap 30g.

[0076] Furthermore, in the semiconductor light receiving element 1D, the doped region 30 includes a single seventh extension portion 31h extending in another direction (here, the X-axis direction). The seventh extension portion 31h is connected to the outer edge portion 32 at both ends of the extension direction. The sixth extension portion 31f is connected to the seventh extension portion 31h, thereby being connected to the outer edge portion 32 via the seventh extension portion 31h. According to such a semiconductor light receiving element 1D, the same effect as that of the semiconductor light receiving element 1 can be achieved. Furthermore, in the semiconductor light receiving element 1D, as Figure 8 As shown, it is easy to arrange a plurality of them in an array.

[0077] like Figure 8 As shown in FIG. 1 , in the case of forming a structure in which a plurality of semiconductor light receiving elements 1D are arranged in an array, as an example, at positions corresponding to the semiconductor light receiving elements 1D, the semiconductor light receiving elements 1D can be provided with a plurality of semiconductor light receiving elements 1D. Figure 3After forming the doped region 30 as shown, that is, after Figure 4 When forming the recessed portion 50 as shown, etching is performed integrally over a plurality of semiconductor light receiving elements 1D (that is, the second mask M may not be disposed between adjacent semiconductor light receiving elements 1D). In this case, recessed portions 50 facing each other are integrally formed between adjacent semiconductor light receiving elements 1D. Figure 8 In FIG. 1 , the protective film F is omitted from illustration, and the bottom surface 50 i of the recessed portion 50 (the surface of the first cover layer 22 ) is shown.

[0078] On the other hand, when performing etching to form the recessed portion 50, the recessed portion 50 may be formed individually between the plurality of semiconductor light receiving elements 1D by providing the second mask M between the adjacent semiconductor light receiving elements 1D. In this case, the recessed portions 50 facing each other between the adjacent semiconductor light receiving elements 1D are separated from each other with the surface 1a (relatively thick portion of the second semiconductor portion 20) remaining without being etched therebetween.

[0079] [Other Modifications]

[0080] The above describes the embodiment and multiple variations, but the semiconductor light receiving element of the present invention is not limited to the semiconductor light receiving elements 1 to 1D described above, and further variations can be applied. For example, in the above embodiment and variations, the material of the light absorbing layer 21 is not limited to InGaAs and InAsSb, and various semiconductors containing In, P, Al, As, Sb, and Ga, such as InAs, GaAs, GaN, and InGaN, can be used.

[0081] The materials of the first covering layer 22 , the second covering layer 24 , and the covering layers 25 and 26 are not limited to InP and AlInAsSb, and various semiconductors including In, P, Al, As, Sb, and G, such as InAsP, AlInP, AllnAsP, InPSb, and GaN, can also be used.

[0082] Furthermore, in the above embodiment, the case where the doped region 30 reaches the inside of the light absorbing layer 21 is described, but the doped region 30 may not reach the inside of the light absorbing layer 21 .

[0083] In addition, in the semiconductor light receiving element 1C of the third variant, the doped region 30 may include a plurality of (concentric) third extensions 31c having different diameters, and a gap 30g larger than the thickness T22 is defined between them. Furthermore, in the semiconductor light receiving element 1C, an undoped region (in other words, a region other than the doped region 30 (hereinafter the same)) may be provided in such a manner that the annular third extension 31c and the outer edge 32 are divided into a plurality of arc-shaped portions. In this case, as an example, the third extension 31c and the outer edge 32 may be divided into four arc-shaped portions by providing one undoped linear region extending on the fourth extension 31d and another undoped linear region extending on the fifth extension 31e.

[0084] In addition, in the semiconductor light receiving element 1D of the fourth variant, the doped region 30 may also include more than three sixth extension portions 31f, and the number of the sixth extension portions 31f may also be one. When the number of the sixth extension portion 31f is one, a gap 30g is formed between the sixth extension portion 31f and the outer edge portion 32, and its width may be greater than the thickness T22. In addition, in the semiconductor light receiving element 1D, the doped region 30 may not include the sixth extension portion 31f. In this case, the gap between the pair of outer edge portions 32 is the gap 30g, and its width may be greater than the thickness T22. Furthermore, in the semiconductor light receiving element 1D, the doped region 30 may also include more than two seventh extension portions 31h. In addition, in the semiconductor light receiving element 1D, the outer edge portion 32 may be only one.

[0085] Furthermore, in the semiconductor light receiving element 1D, various deformations including the above deformations can be arbitrarily combined and applied, and in this case, the positions of the sixth extension portion 31f and the seventh extension portion 31h can be arbitrarily set. For example, in the case where the doping region 30 of the semiconductor light receiving element 1D does not include the sixth extension portion 31f, that is, in the case where two seventh extension portions 31h are included, the two seventh extension portions 31h can be respectively arranged in a manner that the ends in the extension direction of the outer edge portion 32 (here, the Y-axis direction) are connected to each other, and as a whole, the doping region 30 is a rectangular ring shape when viewed from the first direction. Alternatively, in the case where the sixth extension portion 31f is not included, that is, in the case where one seventh extension portion 31h is included, the one seventh extension portion 31h can be arranged in a manner that the centers in the extension direction of the outer edge portion 32 are connected to each other, and as a whole, the doping region 30 is an H-shaped when viewed from the first direction.

[0086] The structures of the semiconductor light receiving elements 1 to 1D may be partially interchangeable. For example, the pattern of the doped region 30 of the semiconductor light receiving elements 1C and 1D may be used as the doped region 30 of the semiconductor light receiving element 1A or the semiconductor light receiving element 1B.

[0087] Explanation of symbols

[0088] 1, 1A, 1B, 1C, 1D...semiconductor light receiving element, 1a...surface, 21...light absorption layer (1st semiconductor layer), 22...1st covering layer (2nd semiconductor layer), 23, 27...semiconductor layer (3rd semiconductor layer), 24...2nd covering layer (4th semiconductor layer), 25, 26...covering layer (2nd semiconductor layer), 30...doped region, 30g...gap, 31...portion, 31a...1st extension portion (extension portion), 31b...2nd extension portion (extension portion), 31c...3rd extension portion (extension portion), 31f...6th extension portion (extension portion), 50...recessed portion, 50i...bottom surface, 50s...side surface, 55...light receiving portion.

Claims

1. A semiconductor light receiving element, characterized in that: include: The surface on which light is incident; a first semiconductor layer of a first conductivity type; a second semiconductor layer of the first conductivity type stacked on the first semiconductor layer on the surface side of the first semiconductor layer and having a band gap energy larger than that of the first semiconductor layer; and a doped region having a second conductivity type different from the first conductivity type, formed so as to extend from the surface toward the second semiconductor layer and reach at least the interior of the second semiconductor layer, The thickness of the second semiconductor layer in a first direction intersecting the surface is thinner than the thickness of the first semiconductor layer in the first direction, The doped region includes a plurality of portions facing each other with a gap therebetween when viewed from the first direction. A width of the gap is greater than a thickness of the second semiconductor layer in the first direction.

2. The semiconductor light-receiving element according to claim 1, wherein: The plurality of portions of the doped region include at least one pair of extension portions extending in the same direction when viewed from the first direction, The width of the gap is the interval between the pair of extensions.

3. The semiconductor light-receiving element according to claim 1, wherein: The doped region extends from the second semiconductor layer toward the first semiconductor layer and reaches the inside of the first semiconductor layer.

4. The semiconductor light receiving element according to claim 1, wherein: A recess is formed on the surface, A light receiving portion is formed in a region overlapping with a bottom surface of the recessed portion when viewed from the first direction.

5. The semiconductor light-receiving element according to claim 4, wherein: The doped region is exposed at a side surface of the recess.

6. The semiconductor light-receiving element according to claim 1, wherein: The method includes a third semiconductor layer of the first conductivity type stacked on the second semiconductor layer on the surface side of the second semiconductor layer.

7. The semiconductor light-receiving element according to claim 6, wherein: The method includes a fourth semiconductor layer of the first conductivity type stacked on the third semiconductor layer on the surface side of the third semiconductor layer.

8. The semiconductor light-receiving element according to claim 1, wherein: The first semiconductor layer contains InGaAs, The second semiconductor layer contains InP or InAsP.

9. The semiconductor light-receiving element according to claim 6, wherein: The first semiconductor layer contains InAsSb or InAs, The second semiconductor layer contains AlInAsSb, The third semiconductor layer contains InAsSb or InPSb.

10. The semiconductor light receiving element according to claim 7, wherein: The first semiconductor layer contains InGaAs, The second semiconductor layer contains InP or InAsP, The third semiconductor layer contains InGaAs, The fourth semiconductor layer contains InP or InAsP.

Images