Semiconductor light receiving element and method for manufacturing semiconductor light receiving element

Abstract

The semiconductor light receiving element (50) is a semiconductor light receiving element in which a multiplication layer (2), an electric field control layer (3), a light absorption layer (4) and a window layer (5) are sequentially formed on a semiconductor substrate (1), and a p-type region (6) is formed on the window layer (5). The p-type region (6) has a first p-type portion (14) and a second p-type portion (15) having a current multiplication factor based on incident light greater than that of the first p-type portion (14). The first p-type portion (14) is formed in the central portion of the p-type region (6) including a central axis (21c) perpendicular to the semiconductor substrate (1), and the second p-type portion (15) is formed on the outer periphery of the central portion in a radial direction relative to the central axis (21c).

Description

Technical Field

[0001] The present application relates to a semiconductor light receiving element and a method for manufacturing the semiconductor light receiving element. Background Art

[0002] As a semiconductor light receiving element used for optical communication, etc., an avalanche photodiode (APD) which is a type of photodiode (PD) is often used. Photodiodes and avalanche photodiodes are appropriately marked as PD and APD, respectively. In APD, the electric field strength in the multiplication layer is increased by applying a voltage, thereby generating avalanche multiplication, which can amplify carriers. In other words, since it is possible to amplify the carriers reaching the inner multiplication layer among the carriers generated in the light absorption layer by the incident light, it has the characteristic of being able to improve the S / N ratio as a receiver. Therefore, APD is often used, especially for long-distance communication purposes.

[0003] APDs for optical communication applications can be roughly divided into two types based on the materials used in the multiplication layer. Figure 3 In the patent document 1, an APD (first APD) using InP for the multiplication layer is disclosed. Figure 1 , discloses an APD (second APD) using a material containing Al (aluminum) such as InAlAs for the multiplication layer. InAlAs is also described as AlInAs. Figure 3 The first APD disclosed is a device that stacks an n-type InP layer, an n-type light absorption layer, an n-type multiplication layer, and an n-type InP layer in sequence on an n-type InP substrate, and forms a p+ region on the InP layer on the surface side (the side opposite to the InP substrate), and forms a guard ring portion (guard ring) as a p- region on the periphery of the p+ region. For an APD whose multiplication layer is InP, if the electric field strength of the multiplication layer increases, the holes reaching the multiplication layer from the light absorption layer can be multiplied. That is, the APD whose multiplication layer is InP is a hole multiplication type. The guard ring is to prevent edge breakdown such as a sharp multiplication at the outer side, i.e., the end of the p+ region, or to function as a current path when penetration (reach-through) occurs at the end of the p+ region before the center of the p+ region when the input light increases instantaneously, thereby preventing damage caused by current concentration in the p+ region.

[0004] Patent Document 1 Figure 1The second APD disclosed has an n-type InP layer, an n-type multiplication layer, an n-type light absorption layer and an n-type InP layer stacked in sequence on an n-type InP substrate, a p+ region is formed in the InP layer on the surface side, and a guard ring portion (guard ring) as a p- region is formed on the periphery of the p+ region. The APD whose multiplication layer is Al-based is an electron multiplying type. Compared with holes, electrons have a smaller effective mass and move faster, so compared with hole multiplying APDs, electron multiplying APDs can foresee high-speed and low-noise operation. Therefore, with the increase in the bit rate required for semiconductor photosensitive elements for optical communications, electron multiplying APDs are widely used.

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 02-010780 ( Figure 1 , Figure 3 )

[0006] In Patent Document 1 Figure 1 In the disclosed electron multiplying APD (second APD), the multiplication layer is located below the light absorbing layer (on the semiconductor substrate side), and the structure is different from the hole multiplying APD (first APD) in which the multiplication layer is located above the light absorbing layer (on the side opposite to the semiconductor substrate). Figure 1 For the disclosed electron multiplying APD, the multiplication layer is located between the semiconductor substrate and the light absorbing layer, and the depth of the guard ring portion as the p- region is the same as the depth of the p+ region (p-type region) formed in the light receiving region for incident light to pass through, and the guard ring portion does not reach the multiplication layer. In addition, in Patent Document 1, there is no mention of the function of the guard ring portion in the electron multiplying APD (second APD). The guard ring portion in the electron multiplying APD (second APD) cannot perform the same function as the guard ring portion of the hole multiplying APD (first APD) with a different structure.

[0007] Regarding Patent Document 1 Figure 1 In the disclosed electron multiplying APD, the p+ region (p-type region) is surrounded by the p- region, and the multiplication rate based on light incidence near the center of the p+ region (p-type region) becomes high. Usually, in order to make the light incident on the light receiving region of the APD have the highest density in the center of the light receiving region, the position of the optical fiber that propagates the light and the APD is adjusted. Therefore, the patent document 1 Figure 1 In the disclosed electron multiplying APD, when strong light suddenly enters the p-type region of the light receiving region, the carriers generated in the center of the p-type region are greatly multiplied due to the synergistic effect of the multiplication layer being located between the semiconductor substrate and the light absorbing layer and the high multiplication rate in the center of the p-type region, and the photocurrent flowing in the center of the p-type region increases excessively. Figure 1The disclosed electron multiplying APD has a problem in that when strong light is incident on the p-type region of the light receiving region, the photocurrent excessively increases in the center of the p-type region, and the APD generates heat, which easily deteriorates the characteristics. Summary of the invention

[0008] An object of the technology disclosed in the present specification is to provide a semiconductor light-receiving element capable of suppressing degradation of characteristics even when excessive light is incident on a p-type region formed in a light-receiving region for incident light.

[0009] The semiconductor light receiving element of an example disclosed in the present application specification has a semiconductor substrate in which a multiplication layer, an electric field control layer, a light absorption layer and a window layer are sequentially formed, and a p-type region is formed in the window layer. The p-type region has a first p-type portion and a second p-type portion whose multiplication rate of current based on incident light is greater than that of the first p-type portion. The first p-type portion is formed in the central portion of the p-type region including a central axis perpendicular to the semiconductor substrate, and the second p-type portion is formed on the outer periphery of the central portion in the radial direction relative to the central axis.

[0010] A semiconductor light-receiving element as an example disclosed in the present application specification has a p-type region having a first p-type portion formed in a central portion and a second p-type portion at the periphery of the central portion having a current multiplication factor based on incident light greater than that of the first p-type portion. Therefore, even if excessive light is incident on the p-type region formed in the light-receiving region where the incident light is received, degradation of characteristics can be suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a cross-sectional view schematically showing the structure of the first semiconductor light-receiving element according to the first embodiment.

[0012] Figure 2 Yes means Figure 1 A graph showing the calculation results of the breakdown voltage and penetration voltage of a semiconductor light-receiving element.

[0013] Figure 3 Yes means Figure 1 Graph of the current characteristics of a semiconductor light-receiving element.

[0014] Figure 4 It is a cross-sectional view showing a schematic structure of a semiconductor light-receiving element of a comparative example.

[0015] Figure 5 Yes means Figure 4 Graph of the current characteristics of a semiconductor light-receiving element.

[0016] Figure 6 It is to form Figure 1 A diagram for explaining the diffusion process of a p-type region.

[0017] Figure 7 It is to form Figure 1 A diagram for explaining the diffusion process of a p-type region.

[0018] Figure 8 This is a cross-sectional view schematically showing the structure of the second semiconductor light-receiving element according to the first embodiment.

[0019] Fig. 9 This is a cross-sectional view schematically showing the structure of the third semiconductor light-receiving element according to the first embodiment.

[0020] Fig.10 This is a cross-sectional view schematically showing the structure of the fourth semiconductor light-receiving element according to the first embodiment.

[0021] Fig.11 This is a cross-sectional view showing a schematic structure of a semiconductor light-receiving element according to the second embodiment.

[0022] Fig.12 This is a cross-sectional view showing a schematic structure of another semiconductor light-receiving element according to the second embodiment.

[0023] Fig.13 This is a cross-sectional view showing a schematic structure of a semiconductor light-receiving element according to the third embodiment.

[0024] Fig.14 This is a cross-sectional view showing a schematic structure of another semiconductor light-receiving element according to the third embodiment.

[0025] Fig.15 This is a cross-sectional view showing a schematic structure of a semiconductor light-receiving element according to a fourth embodiment.

[0026] Fig.16 This is a cross-sectional view showing a schematic structure of another semiconductor light-receiving element according to the fourth embodiment.

[0027] Fig.17 This is a cross-sectional view showing a schematic structure of a semiconductor light-receiving element according to the fifth embodiment.

[0028] Fig.18 This is a cross-sectional view showing a schematic structure of another semiconductor light-receiving element according to the fifth embodiment. DETAILED DESCRIPTION

[0029] Implementation Method 1

[0030] The semiconductor light receiving element 50 according to Embodiment 1 will be described with reference to the drawings. The same reference numerals are given to the same or corresponding components, and repeated description may be omitted. Figure 1 This is a cross-sectional view schematically showing the structure of the first semiconductor light-receiving element according to the first embodiment. Figure 2 Yes means Figure 1The figure shows the calculation results of the breakdown voltage and reach-through voltage of the semiconductor light-receiving element. Figure 3 Yes means Figure 1 Graph of the current characteristics of a semiconductor light-receiving element. Figure 4 is a cross-sectional view showing a schematic structure of a semiconductor light-receiving element of a comparative example, Figure 5 Yes means Figure 4 Graph of the current characteristics of a semiconductor light-receiving element. Figure 6 , Figure 7 It is to form Figure 1 A diagram for explaining the diffusion process of a p-type region. Figure 8 is a cross-sectional view showing a schematic structure of a second semiconductor light-receiving element according to Embodiment 1, Fig. 9 This is a cross-sectional view schematically showing the structure of the third semiconductor light-receiving element according to the first embodiment. Fig.10 This is a cross-sectional view showing a simplified structure of the fourth semiconductor light-receiving element according to Embodiment 1. On the surface of an n-type InP substrate, i.e., a semiconductor substrate 1, a multiplication layer 2 of n-type AlInAs containing Al (aluminum), an electric field control layer 3 of p-type InP, a light absorption layer 4 of n-type InGaAs, and a window layer 5 of n-type InP are sequentially stacked. A p-type region 6 is formed in a portion of the window layer 5, and a vertical structural region including the p-type region 6 is set as a light-receiving region 22. Figure 1 In FIG. 1 , the light receiving region 22 is a region from the dotted line 21 a to the dotted line 21 e , and the surface shape of the p-type region 6 is, for example, a circle.

[0031] A passivation film 8 such as SiN and SiO2 is formed on the surface of the window layer 5 (the surface on the opposite side to the semiconductor substrate 1), and an anode electrode 7 is formed on the surface of the p-type region 6. The p-type region 6 is electrically connected to the anode electrode 7. A cathode electrode 9 and an anti-reflection film 10 are formed on the back side of the semiconductor substrate 1. The back side of the semiconductor substrate 1 is electrically connected to the cathode electrode 9. The shape of the cathode electrode 9 (back side shape) observed from the back side of the semiconductor light receiving element 50 is, for example, a rectangle, and a circular opening 20 is formed therein, and an anti-reflection film 10 is formed on the back side of the semiconductor substrate 1 inside the opening 20. The back side shape of the anti-reflection film 10 is circular. Figure 1 , an example is shown in which the radial outer periphery of the p-type region 6 with respect to the central axis 21 c coincides with the radial outer periphery of the antireflection film 10 . Figure 1 The semiconductor light receiving element 50 shown is a back-illuminated avalanche photodiode in which light is incident from the back side of the semiconductor substrate 1 .

[0032] The multiplication layer 2, the electric field control layer 3, the light absorption layer 4 and the window layer 5 are epitaxial layers formed by using a MOCVD (Metal Organic Chemical Vapor Deposition) device, an MBE (Molecular Beam Epitaxy) device, etc. The passivation film 8 is formed by using a vapor deposition device, a sputtering device, a CVD (Chemical Vapor Deposition) device, etc., and is formed by using photolithography technology and etching technology. The anode electrode 7 and the cathode electrode 9 are formed by using a vapor deposition device, a sputtering device, etc., and are formed by using photolithography technology and etching technology. The anti-reflection film 10 is formed by using a sputtering device, a vapor deposition device, a CVD device, an MBE device, etc.

[0033] The p-type region 6 is formed above the interface between the light absorbing layer 4 and the window layer 5, that is, inside the window layer 5 separated from the interface. The p-type region 6 includes a first p-type portion 14 having a shallow depth in the stacking direction of the epitaxial layer, and a second p-type portion 15 having a deeper depth in the stacking direction of the epitaxial layer than the first p-type portion 14. The second p-type portion 15 extends further toward the semiconductor substrate 1 than the first p-type portion 14. In addition, the second p-type portion 15 is formed at the outermost peripheral portion in the radial direction of the p-type region 6. The diffusion fronts of the first p-type portion 14 and the second p-type portion 15 are both located above the interface between the light absorbing layer 4 and the window layer 5, and are formed inside the window layer 5 separated from the interface between the light absorbing layer 4 and the window layer 5. The diffusion front refers to the boundary in the depth direction between the portion where the dopant is diffused and the portion where the dopant is not diffused when the dopant is diffused from the surface of the epitaxial layer (the surface where the diffusion source of the dopant enters).

[0034] The surface shape of the first p-type portion 14 is circular, and the surface shape of the second p-type portion 15 is a ring shape surrounding the outer circumference of the first p-type portion 14. The diffusion front of the second p-type portion 15 becomes deepest at the position indicated by the dotted lines 21b and 21d. The dotted line 21c is the central axis of the p-type region 6, and represents the central axis of the light receiving region 22. The central axis 21c is perpendicular to the semiconductor substrate 1, and light enters the semiconductor light receiving element 50, for example, parallel to the central axis 21c. For the distance between the diffusion front of the first p-type portion 14 and the diffusion front of the second p-type portion 15, that is, the diffusion front difference d1, as long as there is a difference, for example, it is greater than 1nm and less than 100nm. The carrier concentration (impurity concentration) of the p-type region 6 is, for example, about 5×10 17 cm -3 The diffusion front difference d1 can also be referred to as the difference in distance between the end portion of the first p-type portion 14 closest to the semiconductor substrate 1 and the end portion of the second p-type portion 15 closest to the semiconductor substrate 1 in the direction of the central axis 21 c .

[0035] By making the diffusion front of the second p-type portion 15 deeper than the diffusion front of the first p-type portion 14, which is the center of the p-type region 6 including the central axis 21c, it is possible to give a difference in the breakdown voltage (Vbr) and the penetration voltage (Vre) of the APD in the center and the periphery of the p-type region 6, that is, the center and the periphery of the light receiving region 22. Figure 2 , Figure 3 , the characteristics of the first p-type portion 14 and the second p-type portion 15 are described. Figure 2 The calculation results of breakdown voltage (Vbr), penetration voltage (Vre), and multiplication rate are shown in FIG. Figure 3 , the current characteristics of the semiconductor light receiving element 50 are schematically shown. Figure 3 In the figure, the horizontal axis and vertical axis are voltage and current respectively. Figure 2 As shown, the breakdown voltage (Vbr), the penetration voltage (Vre), and the multiplication rate of the first p-type portion 14 are 35.16V, 15.78V, and 6.7, respectively. The breakdown voltage (Vbr), the penetration voltage (Vre), and the multiplication rate of the second p-type portion 15 are 33.46V, 14.60V, and 9.6, respectively. The multiplication rate based on light incidence is the ratio of the current I0 before avalanche multiplication occurs to the current I1 in the state where avalanche multiplication occurs, and is represented by I1 / I0. Figure 2 The values ​​of the multiplication factors shown are values ​​obtained when a reverse bias of 30 V is applied between the anode electrode 7 and the cathode electrode 9 . Figure 3 V1 shown is an operating voltage of the semiconductor light receiving element 50, which is 30V, for example.

[0036] Figure 3 The current characteristic 25 is the current characteristic of the central portion of the first p-type portion 14, Figure 3 The current characteristic 26 is the current characteristic of the second p-type portion 15. Figure 3 As shown, the current-voltage characteristics are different between the center of the light receiving region 22 and the periphery of the light receiving region 22, and the multiplication rate when the same voltage is applied also changes. Therefore, for the semiconductor light receiving element 50 of embodiment 1, even if the applied voltage between the anode electrode 7 and the cathode electrode 9 is the same, the multiplication rate can be changed between the center of the light receiving region 22 and the periphery of the light receiving region 22. Specifically, when a constant applied voltage is applied between the anode electrode 7 and the cathode electrode 9, the center of the light receiving region 22, i.e., the first p-type portion 14, is in a state with a low multiplication rate compared to the periphery of the light receiving region 22, i.e., the second p-type portion 15. The multiplication rate, as described above, indicates the increase ratio of the current generated by the input of light, i.e., how many times the carriers are multiplied for output. A large multiplication rate means that even if the light input is the same, the photocurrent flowing is also large.

[0037] As described above, the positions of the optical fiber and the APD that propagate the light are usually adjusted in such a way that the light incident on the light receiving area 22 of the APD has the highest density in the center of the light receiving area 22. Therefore, when light is input, the light density is high in the center of the light receiving area 22, especially the center indicated by the dotted line 21c, so a large number of carriers are generated in the center of the light receiving area 22, and as a result, the current flowing in the center of the light receiving area 22 increases. This phenomenon is particularly significant in the center indicated by the dotted line 21c. Therefore, in the case of excessive light input, the photocurrent flowing in the center of the light receiving area 22 increases, and heat is generated along with the increase in photocurrent, and sometimes the characteristics are degraded. However, for the semiconductor light receiving element 50 of embodiment 1, since the multiplication rate of the central portion of the light receiving region 22, i.e., the first p-type portion 14, is lower than that of the peripheral portion of the light receiving region 22, i.e., the second p-type portion 15, the photocurrent flowing in the second p-type portion 15 of the light receiving region 22 increases, and the photocurrent flowing in the first p-type portion 14 of the light receiving region 22 decreases. Even if an overcurrent is generated, the photocurrent is difficult to concentrate on the first p-type portion 14 of the light receiving region 22, and the characteristic degradation caused by heat can be suppressed.

[0038] The current characteristics of the semiconductor light receiving element 60 of the comparative example in which the guard ring 64 is formed will be described. Figure 4 The semiconductor light receiving element 60 shown in the figure has an electric field control layer 3 formed on the surface of the light absorption layer 4, a multiplication layer 62 and a window layer 5 formed on the surface of the electric field control layer 3, and a guard ring 64 formed on the outer periphery of the first p-type portion 14. Figure 1 The semiconductor light receiving element 50 of the comparative example is different. The back side (semiconductor substrate 1 side) of the first p-type portion 14 is in contact with the n-type multiplication layer 62. The diffusion front edge of the guard ring 64 is deepest at the position indicated by the dotted lines 21b and 21d. The multiplication layer 62 of the semiconductor light receiving element 60 of the comparative example is InP, and the impurity concentration of the guard ring 64 is lighter than that of the first p-type portion 14. Even if light is incident directly below the guard ring 64 of the semiconductor light receiving element 60 of the comparative example, avalanche multiplication will not occur, so the guard ring 64 acts like a PD without avalanche multiplication.

[0039] exist Figure 5 , the current characteristics of the semiconductor light receiving element 60 of the comparative example are schematically shown. Figure 5 In the figure, the horizontal axis is voltage and the vertical axis is current respectively. Figure 5 The current characteristic 27 is a current characteristic of the central portion of the first p-type portion 14, Figure 5 The current characteristic 28 is the current characteristic of the guard ring 64. Figure 5As shown, the semiconductor light receiving element 60 of the comparative example is structured as follows: the photocurrent of the outer portion of the light receiving region 22, i.e., the guard ring 64, is smaller than the photocurrent of the central portion of the light receiving region 22, and the multiplication rate of the outer portion of the light receiving region 22, i.e., the guard ring 64, is lower than the multiplication rate of the central portion of the light receiving region 22. In addition, since avalanche multiplication does not occur directly below the guard ring 64, the multiplication rate of the outer portion of the light receiving region 22 is 1. Therefore, the current characteristics of the central portion and the outer portion of the light receiving region 22 in the semiconductor light receiving element 60 of the comparative example become opposite to the current characteristics of the central portion and the outer portion of the light receiving region 22 in the semiconductor light receiving element 50 of the first embodiment. As such, the guard ring 64 in the semiconductor light receiving element 60 of the comparative example in which the multiplication layer 62 is InP and the outer portion of the light receiving region 22, i.e., the second p-type portion 15 in the semiconductor light receiving element 50 of the first embodiment, have different functions.

[0040] Therefore, the semiconductor light receiving element 60 of the comparative example cannot achieve the following effect of the semiconductor light receiving element 50 of the first embodiment: even if strong light is incident on the light receiving region 22 and an overcurrent is generated, the photocurrent flowing in the second p-type portion 15 of the light receiving region 22 is greater than the photocurrent flowing in the first p-type portion 14 of the light receiving region 22, and therefore it is difficult to concentrate on the first p-type portion 14 of the light receiving region 22, and the degradation of characteristics due to heat can be suppressed. When strong light is incident on the light receiving region 22 and an overcurrent is generated, the semiconductor light receiving element 60 of the comparative example is different from the semiconductor light receiving element 50 of the first embodiment, and therefore heat is generated with the increase in the photocurrent, and sometimes the characteristics are degraded. The semiconductor light receiving element 60 of the comparative example needs to reduce the driving voltage or the intensity of the incident light compared with the semiconductor light receiving element 50 of the first embodiment.

[0041] The semiconductor light receiving element 50 of the first embodiment can make the multiplication rate of the central part (first p-type part 14) of the light receiving region 22 with high light density lower than that of the peripheral part (second p-type part 15) of the light receiving region 22, thereby suppressing excessive multiplication in the central part (first p-type part 14) of the light receiving region 22 when excessive light is input, and suppressing the degradation of characteristics due to heat. Even if strong light is incident on the light receiving region 22 and an overcurrent is generated, the characteristics of the semiconductor light receiving element 50 of the first embodiment will not be degraded, that is, the overcurrent tolerance or light excessive input tolerance is high, so the life is longer than the semiconductor light receiving element 60 of the comparative example. In addition, since the semiconductor light receiving element 50 of the first embodiment has high overcurrent tolerance or light excessive input tolerance, it can increase the operating voltage V1 compared with the semiconductor light receiving element 60 of the comparative example and operate with high sensitivity.

[0042] In addition, even if the operating voltage V1 is lowered to reduce the overall multiplication rate, the degradation of characteristics caused by heat can be suppressed. However, in this case, there is a problem that the photocurrent of the entire light receiving area 22 is reduced, and the receiving sensitivity is deteriorated. In contrast, since the multiplication rate of the peripheral part of the light receiving area 22 is high, the total amount of photocurrent flowing in the entire light receiving area 22 is almost not reduced even if the operating voltage V1 is lowered, and it is difficult to produce the degradation of characteristics caused by the reduction of photocurrent. That is, even if the operating voltage V1 is lowered, the semiconductor light receiving element 50 of embodiment 1 can suppress the degradation of characteristics caused by the reduction of photocurrent compared with the semiconductor light receiving element 60 of the comparative example.

[0043] use Figure 6 , Figure 7 An example of a method for forming the p-type region 6 is described. The p-type region 6 is formed, for example, by two diffusion steps. The p-type region 6 is a region obtained by diffusion of a p-type dopant such as Zn (zinc) or Be (beryllium). The p-type dopant used for the p-type region 6 may also be a dopant other than Zn or Be. However, the p-type dopant used for the p-type region 6 is preferably Zn. When the p-type dopant is Zn, it is easy to increase the carrier concentration (impurity concentration) of the p-type region 6, and the controllability of the diffusion front is good, so it is suitable for forming the structure of the p-type region 6 of embodiment 1, that is, a structure in which the diffusion front of the second p-type portion 15 is deeper than the diffusion front of the first p-type portion 14. When the p-type dopant is Zn (zinc), the p-type region 6 is a region obtained by diffusion of Zn (zinc).

[0044] Figure 6 The figure shows a state where after the multiplication layer 2, the electric field control layer 3, the light absorption layer 4, and the InP window layer 5 are sequentially stacked on the surface of the semiconductor substrate 1 to form a stack (after the stack formation step), an anti-diffusion mask 24 is formed, and a p-type dopant is diffused from the opening 29 of the anti-diffusion mask 24 to form the second p-type portion 15. The opening 29 of the anti-diffusion mask 24 is formed in a ring shape. After the second p-type portion 15 is formed in the window layer 5, the second p-type portion 15 is removed. Figure 6 The anti-diffusion mask 24 shown in FIG. Figure 7 The anti-diffusion mask 24 is shown reformed. Figure 7 The illustrated anti-diffusion mask 24 is formed so that the opening 29 coincides with the outer periphery of the second p-type portion 15. The p-type dopant is diffused from the opening 29 of the anti-diffusion mask 24, and the first p-type portion 14 is formed. Figure 6 The second p-type portion forming step of forming the second p-type portion 15 of the p-type region is shown. Figure 7The first p-type portion forming step is shown in which the first p-type portion 14 of the p-type region 6 is formed after the second p-type portion forming step. The concentration of the p-type dopant is high on the surface side of the second p-type portion 15. In addition, in each figure showing a cross section, the expansion caused by the diffusion of the second p-type portion 15 in the horizontal direction (direction parallel to the semiconductor substrate 1) is omitted. Figure 4 The guard ring 64 also omits the expansion caused by diffusion in the horizontal direction (the direction parallel to the semiconductor substrate 1 ).

[0045] It can also be between the p-type region 6 and the anode electrode 7, such as Figure 8 As shown, a contact layer 18 of AlGaInAs, InGaAsP, InGaAs, etc., or a combination thereof, is provided to reduce contact resistance. In addition, in order to alleviate band discontinuity, band discontinuity relaxation layers 17a, 17b, 17c, and 17d using InGaAsP, AlGaInAs, etc. may be provided at the interface portion of each epitaxial layer. The band discontinuity relaxation layer 17a is formed between the semiconductor substrate 1 and the multiplication layer 2, and the band discontinuity relaxation layer 17b is formed between the multiplication layer 2 and the electric field control layer 3. The band discontinuity relaxation layer 17c is formed between the electric field control layer 3 and the light absorption layer 4, and the band discontinuity relaxation layer 17d is formed between the light absorption layer 4 and the window layer 5.

[0046] like Fig. 9 As shown, cathode electrode 9 may not be arranged on the back surface of semiconductor substrate 1 , but may be arranged on the front surface side of window layer 5 similarly to anode electrode 7 . Fig. 9 The third semiconductor light receiving element 50 of the embodiment 1 shown in the figure comprises: a groove portion 13 which penetrates the window layer 5, the light absorption layer 4, the electric field control layer 3 and the multiplication layer 2 and reaches the semiconductor substrate 1; a cathode electrode 9 which is connected to the semiconductor substrate 1; and an insulating film 12 which insulates the cathode electrode 9 from the window layer 5, the light absorption layer 4, the electric field control layer 3 and the multiplication layer 2. Fig. 9 , an example is shown in which the antireflection film 10 is not formed on the back surface of the semiconductor substrate 1 in the light receiving region 22, and the passivation film 8 is not formed in the region outside the light receiving region 22 in the window layer 5 where the cathode electrode 9 is not formed. Figure 1 , Figure 8 The semiconductor light receiving element 50 may not have the passivation film 8 and the anti-reflection film 10. In addition, the semiconductor light receiving element 50 may have the passivation film 8 formed on the side surface of the epitaxial layer.

[0047] The semiconductor light receiving element 50 is not limited to the back-incident type. Fig.10 As shown, it can also be a surface-incident avalanche photodiode. Fig.10 The fourth semiconductor light receiving element 50 of the first embodiment shown in FIG. Figure 1The first semiconductor light receiving element 50 of the first embodiment is different in the following aspects. For the fourth semiconductor light receiving element 50, the cathode electrode 9 is formed on the back side of the semiconductor substrate 1, the anode electrode 7 is annular, and an anti-reflection film 16 is formed on the surface area of ​​the window layer 5 where the anode electrode 7 is not formed. For the fourth semiconductor light receiving element 50, the area of ​​the opening 30 of the anode electrode 7, that is, the opening area, is the light receiving area 22. Fig.10 In FIG. 1 , the light receiving region 22 is the range of the dotted lines 23 a to 23 b. The fourth semiconductor light receiving element 50 has the same structure of the p-type region 6 as the first semiconductor light receiving element 50 , and thus has the same effects as the first semiconductor light receiving element 50 .

[0048] In addition, the carrier concentration (impurity concentration) of the p-type region 6 is about 5×10 17 cm -3 For example, the carrier concentration (impurity concentration) of the p-type region 6 is preferably 1×10 18 cm -3 The carrier concentration of the light absorbing layer 4 is usually 1×10 16 cm -3 If the carrier concentration of the p-type region 6 is low, the width of the depletion region becomes unstable, and therefore the difference between the multiplication rate of the second p-type portion 15 and the multiplication rate of the first p-type portion 14 cannot be achieved with high accuracy. 17 cm -3 In the case of , the difference between the multiplication rate of the second p-type portion 15 and the multiplication rate of the first p-type portion 14 can be achieved with high accuracy. In addition, if the carrier concentration (impurity concentration) of the p-type region 6 is 1×10 18 cm -3 As described above, the difference between the multiplication rate of second p-type portion 15 and the multiplication rate of first p-type portion 14 can be realized with higher accuracy.

[0049] In the semiconductor light-receiving element 50 of the first embodiment, since the carrier concentration (impurity concentration) of the p-type region 6 is about 5×10 17 cm -3 , so the depletion layer width when bias is applied can be determined with high accuracy, and the effect of the first semiconductor light receiving element 50 can be stably obtained. In addition, for the semiconductor light receiving element 50 of the first embodiment, the carrier concentration (impurity concentration) in the p-type region 6 is 1×10 18 cm -3 In the above case, the depletion layer width during bias application can be determined with higher accuracy, and the effect of the first semiconductor light receiving element 50 can be obtained more stably.

[0050] The example of forming the p-type region 6 by two diffusion steps has been described, but a single diffusion step may be used. Figure 6 The central portion of the anti-diffusion mask 24 , that is, the portion that prevents the formation of the first p-type portion 14 , is changed to a diffusion control mask having a slow diffusion rate of the p-type dopant, thereby forming the first p-type portion 14 simultaneously with the second p-type portion 15 .

[0051] In addition, as long as the light absorption layer 4 is a material that generates carriers when light is incident, in other words, a material with a small band gap relative to the incident light, it is not limited to InGaAs, and it may be InGaAsP, InGaAsSb, etc., or a combination thereof. As long as the window layer 5 is a material that does not generate carriers when light is incident, in other words, a material with a large band gap relative to the incident light, AlInAs, AlGaInAs, InGaAsP, etc., or a combination thereof may be used. The electric field control layer 3 is not limited to InP, and it may also be formed using AlInAs. In addition, as long as the characteristics required for APD operation can be obtained, any material may be used for each epitaxial layer, and the material of each epitaxial layer is not limited to the material used for description.

[0052] As described above, the semiconductor light receiving element 50 of the first embodiment is a semiconductor light receiving element in which the multiplication layer 2, the electric field control layer 3, the light absorption layer 4, and the window layer 5 are formed in order on the semiconductor substrate 1, and the p-type region 6 is formed on the window layer 5. The p-type region 6 includes the first p-type portion 14 and the second p-type portion 15 having a larger multiplication rate of current based on incident light than the first p-type portion 14. The first p-type portion 14 is formed in the central portion of the p-type region 6 including the central axis 21c perpendicular to the semiconductor substrate 1, and the second p-type portion 15 is formed on the periphery of the central portion in the radial direction relative to the central axis 21c. Since the semiconductor light receiving element 50 of the first embodiment includes the first p-type portion 14 formed in the central portion and the second p-type portion 15 having a larger multiplication rate of current based on incident light than the first p-type portion 14 on the periphery of the central portion, even if excessive light is incident on the p-type region 6 formed in the light receiving region 22 into which light is incident, it is possible to suppress degradation of characteristics.

[0053] The semiconductor light receiving element manufacturing method of the first embodiment is a semiconductor light receiving element manufacturing method for manufacturing a semiconductor light receiving element 50, the semiconductor light receiving element 50 includes a semiconductor substrate 1, a multiplication layer 2, an electric field control layer 3, a light absorption layer 4, and a window layer 5, and a p-type region 6 having a first p-type portion 14 and a second p-type portion 15 having a larger multiplication rate of current based on incident light than the first p-type portion 14 is formed on the window layer 5. The semiconductor light receiving element manufacturing method of the first embodiment includes the following steps: a step of sequentially forming the multiplication layer 2, the electric field control layer 3, the light absorption layer 4, and the window layer 5 on the semiconductor substrate 1; a first p-type portion forming step of forming the first p-type portion 14 of the p-type region 6; and a second p-type portion forming step of forming the second p-type portion 15 of the p-type region 6 after the first p-type portion forming step. The semiconductor light-receiving element manufacturing method of embodiment 1 can manufacture a semiconductor light-receiving element 50 in which the p-type region 6 has a first p-type portion 14 formed in the central portion, and a second p-type portion 15 at the periphery of the central portion, the multiplication factor of the current based on incident light being larger than that of the first p-type portion 14. Therefore, it is possible to manufacture a semiconductor light-receiving element 50 in which characteristic degradation can be suppressed even if excessive light is incident on the p-type region 6 formed in the light-receiving region 22 for incident light.

[0054] In addition, the method for manufacturing a semiconductor light receiving element of the first embodiment includes the following steps: a step of sequentially stacking a multiplication layer 2, an electric field control layer 3, a light absorption layer 4, and a window layer 5 on a semiconductor substrate 1 to form a stacked body; a first p-type portion forming step of forming a first p-type portion 14 of a p-type region 6; and a second p-type portion forming step of forming a second p-type portion 15 of the p-type region 6 after the first p-type portion forming step. The method for manufacturing a semiconductor light receiving element of the first embodiment can manufacture a semiconductor light receiving element 50 in which the p-type region 6 has a first p-type portion 14 formed in the center and a second p-type portion 15 at the periphery of the center having a larger multiplication rate of current based on incident light than the first p-type portion 14, and therefore can manufacture a semiconductor light receiving element 50 in which characteristic degradation can be suppressed even when excessive light is incident on the p-type region 6 formed in the incident light receiving region 22.

[0055] Implementation Method 2

[0056] Fig.11 is a cross-sectional view showing a schematic structure of a semiconductor light-receiving element according to Embodiment 2. Fig.122 is a cross-sectional view showing a schematic structure of another semiconductor light-receiving element involved in Embodiment 2. The semiconductor light-receiving element 50 of Embodiment 2 is different from the semiconductor light-receiving element 50 of Embodiment 1 in that the diffusion front edge of the second p-type portion 15 of the p-type region 6 is formed inside the light-absorbing layer 4, that is, the second p-type portion 15 is formed extending to the inside of the light-absorbing layer 4. The other structures are the same as those of the semiconductor light-receiving element 50 of Embodiment 1. The semiconductor light-receiving element 50 of Embodiment 2 is similar to the semiconductor light-receiving element 50 of Embodiment 1, in that the diffusion front edge of the first p-type portion 14 of the p-type region 6 is formed inside the window layer 5 separated from the interface between the light-absorbing layer 4 and the window layer 5. Fig.11 The semiconductor light receiving element 50 shown is a back-illuminated avalanche photodiode. Fig.12 The semiconductor light-receiving element 50 shown is a surface-incident avalanche photodiode.

[0057] Since the semiconductor light receiving element 50 of the second embodiment has a band gap difference between the light absorbing layer 4 and the window layer 5, similarly to the semiconductor light receiving element 50 of the first embodiment, when a reverse bias is applied between the anode electrode 7 and the cathode electrode 9, the band gap difference acts as a potential barrier for holes generated in the light absorbing layer 4. That is, holes generated in the light absorbing layer 4 are difficult to flow to the first p-type portion 14 due to the band gap difference between the light absorbing layer 4 and the window layer 5. When the second p-type portion 15 is formed to a position inside the light absorbing layer 4 relative to the interface between the light absorbing layer 4 and the window layer 5, there is no connection portion between the light absorbing layer 4 and the window layer 5 in the portion where the second p-type portion 15 is connected to the light absorbing layer 4, and the band gap between the second p-type portion 15 and the light absorbing layer 4 becomes lower than the band gap between the light absorbing layer 4 and the window layer 5 below the first p-type portion 14. In this case, for holes generated in the light absorbing layer 4, it is easier to move to the second p-type portion 15 where a large number of carriers are formed as holes in the light absorbing layer 4 than to move from the light absorbing layer 4 to the window layer 5 because the potential barrier is small. Therefore, holes generated in the light absorbing layer 4 tend to flow to the second p-type portion 15 formed inside the light absorbing layer 4 with a small potential barrier. In other words, holes generated in the light absorbing layer 4 flow through the second p-type portion 15 of the p-type region 6. This means that the photocurrent flowing in the first p-type portion 14 of the light receiving region 22 is reduced, that is, the photocurrent flowing in the central portion of the light receiving region 22 is reduced.

[0058] Since the second p-type portion 15 of the p-type region 6 is formed to a position on the inner side of the light absorbing layer 4 relative to the interface between the light absorbing layer 4 and the window layer 5, the semiconductor light receiving element 50 of the second embodiment can suppress the degradation of characteristics compared with the semiconductor light receiving element 50 of the first embodiment even if excessive light enters the p-type region 6 formed in the light receiving region 22. More detailed description. In the semiconductor light receiving element 50 of the second embodiment, when light enters the p-type region 6 formed in the light receiving region 22, the photocurrent flowing in the second p-type portion 15 is always greater than the photocurrent flowing in the first p-type portion 14. Even when excessive light enters the p-type region 6, the photocurrent flowing in the second p-type portion 15 of the light receiving region 22 increases. Therefore, even if an overcurrent is generated, the photocurrent is difficult to concentrate on the first p-type portion 14 of the light receiving region 22, and the degradation of characteristics caused by heat can be suppressed compared with the semiconductor light receiving element 50 of the first embodiment.

[0059] As described above, the semiconductor light receiving element 50 of the second embodiment has the same effect as the semiconductor light receiving element 50 of the first embodiment because the p-type region 6 has the first p-type portion 14 and the second p-type portion 15 whose diffusion front is deeper than the first p-type portion 14. In addition, in the semiconductor light receiving element 50 of the second embodiment, since the second p-type portion 15 of the p-type region 6 is formed to the inner side of the light absorbing layer 4 than the interface between the light absorbing layer 4 and the window layer 5, even if an overcurrent is generated, the photocurrent is less likely to be concentrated on the first p-type portion 14 of the light receiving region 22 than in the semiconductor light receiving element 50 of the first embodiment, and the characteristic degradation due to heat generation can be suppressed.

[0060] Implementation 3

[0061] Fig.13 is a cross-sectional view showing a schematic structure of a semiconductor light-receiving element according to Embodiment 3. Fig.14 2 is a cross-sectional view showing a schematic structure of another semiconductor light-receiving element involved in Embodiment 3. The semiconductor light-receiving element 50 of Embodiment 3 is different from the semiconductor light-receiving element 50 of Embodiment 1 in that the second p-type portion 15 of the p-type region 6 is formed in a ring shape between the radial outer periphery and the center (central axis 21c) of the p-type region 6. In addition, for the semiconductor light-receiving element 50 of Embodiment 3, it can be said that the first p-type portion 14 is also formed on the radial outer periphery of the second p-type portion 15, or it can be said that the second p-type portion 15 is formed on the side closer to the central axis 21c than the radial outermost periphery of the p-type region 6. The other structures are the same as those of the semiconductor light-receiving element 50 of Embodiment 1. The outer periphery of the p-type region 6 is the portion where the dotted line 21a passes and the portion where the dotted line 21e passes, and the center of the p-type region 6 is the portion where the dotted line 21c passes. Fig.13The semiconductor light receiving element 50 shown is a back-illuminated avalanche photodiode. Fig.14 The semiconductor light-receiving element 50 shown is a surface-incident avalanche photodiode.

[0062] The semiconductor light receiving element 50 of the third embodiment is similar to the semiconductor light receiving element 50 of the first embodiment. Since the p-type region 6 has the first p-type portion 14 and the second p-type portion 15 whose diffusion front is deeper than the first p-type portion 14, the semiconductor light receiving element 50 of the third embodiment has the same effect as the semiconductor light receiving element 50 of the first embodiment.

[0063] In addition, in the semiconductor light receiving element 50 of the third embodiment, the outer periphery of the p-type region 6, that is, the outer periphery of the first p-type portion 14, is separated from the outer periphery of the second p-type portion 15, and the distance between the imaginary line 21a passing through the outer periphery of the p-type region 6 and the imaginary line 21b passing through the deepest diffusion front edge of the second p-type portion 15, that is, the deepest portion distance l1, is longer than that of the semiconductor light receiving element 50 of the first embodiment. Similarly, in the semiconductor light receiving element 50 of the third embodiment, the distance between the imaginary line 21e passing through the outer periphery of the p-type region 6 and the imaginary line 21d passing through the deepest diffusion front edge of the second p-type portion 15, that is, the deepest portion distance l1, is longer than that of the semiconductor light receiving element 50 of the first embodiment. Since the deepest distance l1 of the semiconductor light receiving element 50 of the third embodiment is longer than that of the semiconductor light receiving element 50 of the first embodiment, the shape of the outer periphery of the p-type region 6, that is, the region of the dotted line 21a to the dotted line 21b and the region of the dotted line 21d to the dotted line 21e, can be smoother than that of the semiconductor light receiving element 50 of the first embodiment, and the electric field concentration in the outer periphery of the p-type region 6 can be reduced compared with the semiconductor light receiving element 50 of the first embodiment. If the shape of the outer periphery of the p-type region 6 is considered in terms of curvature, the semiconductor light receiving element 50 of the third embodiment can make the curvature of the outer periphery of the p-type region 6 smaller than that of the semiconductor light receiving element 50 of the first embodiment.

[0064] Since the outer peripheral shape of the p-type region 6 of the semiconductor light receiving element 50 of the third embodiment is gentler than that of the semiconductor light receiving element 50 of the first embodiment, edge breakdown at the end of the light receiving region 22 can be suppressed compared to the semiconductor light receiving element 50 of the first embodiment.

[0065] Implementation 4

[0066] Fig.15 is a cross-sectional view showing a schematic structure of a semiconductor light-receiving element according to Embodiment 4. Fig.161 is a cross-sectional view showing a schematic structure of another semiconductor light receiving element involved in Embodiment 4. The semiconductor light receiving element 50 of Embodiment 4 is different from the semiconductor light receiving element 50 of Embodiment 3 in that the diffusion front edge of the second p-type portion 15 of the p-type region 6 is formed inside the light absorbing layer 4. The other structures are the same as those of the semiconductor light receiving element 50 of Embodiment 3. Fig.15 The semiconductor light receiving element 50 shown is a back-illuminated avalanche photodiode. Fig.16 The semiconductor light receiving element 50 shown is a surface-incident avalanche photodiode. The semiconductor light receiving element 50 of the fourth embodiment is a combination of the structure of the semiconductor light receiving element 50 of the third embodiment and the structure of the semiconductor light receiving element 50 of the second embodiment.

[0067] Similar to the semiconductor light receiving element 50 of the first embodiment, the semiconductor light receiving element 50 of the fourth embodiment has the same effect as the semiconductor light receiving element 50 of the first embodiment because the p-type region 6 has the first p-type portion 14 and the second p-type portion 15 whose diffusion front is deeper than the first p-type portion 14. In addition, similar to the semiconductor light receiving element 50 of the third embodiment, the semiconductor light receiving element 50 of the fourth embodiment has the outer periphery of the p-type region 6, that is, the outer periphery of the first p-type portion 14 and the outer periphery of the second p-type portion 15 separated, and the deepest distance l1 is longer than that of the semiconductor light receiving element 50 of the first embodiment, so that the shape of the outer periphery of the p-type region 6 can be made gentler than that of the semiconductor light receiving element 50 of the first embodiment, and the electric field concentration at the outer periphery of the p-type region 6 can be reduced compared with the semiconductor light receiving element 50 of the first embodiment.

[0068] Furthermore, similarly to the semiconductor light receiving element 50 of the second embodiment, the semiconductor light receiving element 50 of the fourth embodiment can form a path for the photocurrent to flow easily in a portion that is not the center of the light receiving region 22 because the diffusion front edge of the second p-type portion 15 of the p-type region 6 is formed inside the light absorbing layer 4. Therefore, in the semiconductor light receiving element 50 of the fourth embodiment, the multiplication rate of the center portion of the light receiving region 22 (the first p-type portion 14 on the inner side of the second p-type portion 15) is lower than that of the semiconductor light receiving element 50 of the third embodiment, and even if an overcurrent is generated, the photocurrent is less likely to be concentrated on the first p-type portion 14 of the light receiving region 22 than in the semiconductor light receiving element 50 of the third embodiment, and the characteristic degradation due to heat can be suppressed.

[0069] Since the semiconductor light receiving element 50 of embodiment 4 is formed by combining the structure of the semiconductor light receiving element 50 of embodiment 3 with the structure of the semiconductor light receiving element 50 of embodiment 2, when excessive light enters the p-type region 6, it is possible to suppress the edge breakdown at the end of the light receiving region 22 while suppressing the degradation of characteristics due to heat.

[0070] Implementation method 5

[0071] Fig.17 is a cross-sectional view showing a schematic structure of a semiconductor light-receiving element according to Embodiment 5. Fig.18 1 is a cross-sectional view showing a schematic structure of another semiconductor light-receiving element according to Embodiment 5. The semiconductor light-receiving element 50 according to Embodiment 5 is different from the semiconductor light-receiving element 50 according to Embodiment 1 in that the distance between the diffusion front edge of the first p-type portion 14 and the diffusion front edge of the second p-type portion 15, i.e., the diffusion front difference is a diffusion front difference d2 of 100 nm or more. The other structures are the same as those of the semiconductor light-receiving element 50 according to Embodiment 1. Fig.17 The semiconductor light receiving element 50 shown is a back-illuminated avalanche photodiode. Fig.18 The semiconductor light receiving element 50 shown is a surface-incident avalanche photodiode. When the distance between the diffusion front edge of the first p-type portion 14 and the diffusion front edge of the second p-type portion 15, i.e., the diffusion front difference, is 100 nm or more, in one example of calculation, the multiplication factor of the central portion of the light receiving region 22 (the first p-type portion 14 on the inner side of the second p-type portion 15) can be reduced from 9.6 to 6.7, and the photocurrent flowing in the central portion of the light receiving region 22 can be reduced by about 30%.

[0072] Since the semiconductor light receiving element 50 of the fifth embodiment has a diffusion front difference, i.e., a distance between the diffusion front edge of the first p-type portion 14 and the diffusion front edge of the second p-type portion 15, of 100 nm or more, it is possible to achieve a difference in the multiplication rate between the center portion and the multiplication rate of the peripheral portion in the light receiving region 22 more stably than the semiconductor light receiving element 50 of the first embodiment. If the structure in which the diffusion front difference, i.e., the distance between the diffusion front edge of the first p-type portion 14 and the diffusion front edge of the second p-type portion 15 is set to 100 nm or more is applied to the semiconductor light receiving element 50 of the third embodiment, it is possible to achieve a difference in the multiplication rate between the center portion and the multiplication rate of the peripheral portion in the light receiving region 22 more stably than the semiconductor light receiving element 50 of the third embodiment.

[0073] In addition, the structure in which the distance between the diffusion front edge of the first p-type portion 14 and the diffusion front edge of the second p-type portion 15, i.e., the diffusion front difference, is set to 100 nm or more can also be applied to the semiconductor light receiving element 50 of Embodiment 2 and the semiconductor light receiving element 50 of Embodiment 4. In this case, the difference between the multiplication rate of the central portion and the multiplication rate of the peripheral portion in the light receiving region 22 can be stably achieved.

[0074] The semiconductor light receiving element 50 of the fifth embodiment is similar to the semiconductor light receiving element 50 of the first embodiment, because the p-type region 6 includes the first p-type portion 14 and the second p-type portion 15 whose diffusion front is deeper than the first p-type portion 14, and thus the same effect as the semiconductor light receiving element 50 of the first embodiment is achieved. Furthermore, the semiconductor light receiving element 50 of the fifth embodiment has a diffusion front difference, i.e., a distance between the diffusion front of the first p-type portion 14 and the diffusion front of the second p-type portion 15, of 100 nm or more, and thus the difference between the multiplication rate of the center portion and the multiplication rate of the peripheral portion in the light receiving region 22 can be achieved more stably than the semiconductor light receiving element 50 of the first embodiment.

[0075] In addition, although the present application records various illustrative embodiments and examples, the various features, methods and functions recorded in one or more embodiments are not limited to application to specific embodiments, and can be applied to the embodiments alone or in various combinations. Therefore, countless variations that are not illustrated can be imagined within the technical scope disclosed in the present application specification. For example, it includes the case where at least one structural element is deformed, added or omitted, and it also includes the case where at least one structural element is extracted and combined with the structural elements of other embodiments.

[0076] Description of Reference Numerals

[0077] 1…semiconductor substrate, 2…multiplication layer, 3…electric field control layer, 4…light absorption layer, 5…window layer, 6…p-type region, 14…first p-type portion, 15…second p-type portion, 21c…dashed line (central axis), 50…semiconductor light receiving element, d1…diffusion front edge difference (differential distance), d2…diffusion front edge difference (differential distance).

Claims

1. A semiconductor light receiving element, wherein a multiplication layer, an electric field control layer, a light absorption layer and a window layer are sequentially formed on a semiconductor substrate, and a p-type region is formed in the window layer. It is characterized in that The p-type region includes a first p-type portion and a second p-type portion having a current multiplication rate greater than that of the first p-type portion due to incident light. The first p-type portion is formed in a central portion of the p-type region including a central axis perpendicular to the semiconductor substrate. The second p-type portion is formed on the outer periphery of the central portion in the radial direction relative to the central axis. The first p-type portion and the second p-type portion are connected to each other.

2. The semiconductor light receiving element according to claim 1, wherein: The second p-type portion extends toward the semiconductor substrate further than the first p-type portion.

3. The semiconductor light receiving element according to claim 1 or 2, characterized in that: The second p-type portion is formed to extend into the interior of the light absorbing layer.

4. The semiconductor light receiving element according to claim 1 or 2, characterized in that: The second p-type portion is formed at the outermost peripheral portion in the radial direction of the p-type region.

5. The semiconductor light receiving element according to claim 1 or 2, characterized in that: The first p-type portion is further formed on the radial outer periphery of the second p-type portion.

6. The semiconductor light receiving element according to claim 1 or 2, characterized in that: The second p-type portion is formed on the central axis side relative to the radially outermost peripheral portion of the p-type region, and extends toward the semiconductor substrate side relative to the outermost peripheral portion.

7. The semiconductor light receiving element according to claim 1 or 2, characterized in that: The multiplication layer contains aluminum.

8. The semiconductor light receiving element according to claim 1 or 2, characterized in that: The p-type region contains zinc.

9. The semiconductor light receiving element according to claim 1 or 2, characterized in that: The p-type region is a region obtained by diffusion of zinc.

10. The semiconductor light receiving element according to claim 1 or 2, characterized in that: A difference distance between an end portion of the first p-type portion closest to the semiconductor substrate and an end portion of the second p-type portion closest to the semiconductor substrate in the central axis direction is 100 nm or more.

11. The semiconductor light receiving element according to claim 1 or 2, characterized in that: The impurity concentration of the p-type region is 1×10 18 cm -3 above.

12. A method for manufacturing a semiconductor light-receiving element, comprising manufacturing the semiconductor light-receiving element according to any one of claims 1 to 11, It is characterized in that Include: The step of sequentially forming the multiplication layer, the electric field control layer, the light absorption layer and the window layer on the semiconductor substrate; A second p-type portion forming step of forming the second p-type portion of the p-type region; and After the second p-type portion forming step, a first p-type portion forming step of forming the first p-type portion of the p-type region is performed. The first p-type portion and the second p-type portion are connected to each other.

13. A method for manufacturing a semiconductor light-receiving element, comprising manufacturing a semiconductor light-receiving element, the semiconductor light-receiving element comprising a semiconductor substrate, a multiplication layer, an electric field control layer, a light absorption layer, and a window layer, wherein a p-type region having a first p-type portion and a second p-type portion having a larger multiplication rate of current based on incident light than that of the first p-type portion is formed in the window layer, It is characterized in that Include: The step of sequentially stacking the multiplication layer, the electric field control layer, the light absorption layer and the window layer on the semiconductor substrate to form a stacked body; A second p-type portion forming step of forming the second p-type portion of the p-type region; and After the second p-type portion forming step, a first p-type portion forming step of forming the first p-type portion of the p-type region is performed. The first p-type portion and the second p-type portion are connected to each other.

14. The method for manufacturing a semiconductor light-receiving element according to claim 13, wherein: The first p-type portion forming step and the second p-type portion forming step diffuse zinc into the stacked body.

15. The method for manufacturing a semiconductor light-receiving element according to claim 13 or 14, characterized in that: The second p-type portion is formed to extend into the interior of the light absorbing layer.

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