Photodiode

Abstract

To provide a photodiode with high detection speed.SOLUTION: A photodiode 10 includes a first semiconductor part 111, which is a band-shaped region consisting of a first semiconductor that is a p-type or n-type semiconductor and a second semiconductor part 112, which is a band-shaped region wider than the first semiconductor part, consisting of a second semiconductor of the opposite type to the first semiconductor and having a lower carrier concentration than the first semiconductor, three or more alternating strips of which are arranged side by side in the width direction.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a photodiode. [Background technology]

[0002] A photodiode is a semiconductor diode that acts as a light detection element, and is an element that has a pn junction, which is a p-type semiconductor and an n-type semiconductor joined together, similar to a normal semiconductor diode (for passing current only in a specific direction), but is provided with a structure for capturing light (such as a window or a connection part for optical fiber). Instead of a pn junction, there are also photodiodes that have a pin junction, which sandwiches an i-type semiconductor (intrinsic semiconductor) or a p-type or n-type semiconductor with a lower carrier concentration than the p-type and n-type semiconductors between the p-type and n-type semiconductors. In photodiodes with these structures, a depletion layer with almost no carriers (electrons and holes) is formed near the boundary of the pn junction or pin junction. When light is incident on a photodiode, pairs of electrons and holes that become carriers are generated, and these carriers move due to the electric field, generating a photocurrent. By detecting this photocurrent, the incidence of light on the photodiode is detected.

[0003] Patent Document 1 discloses a photodiode in which the boundary between a p-type semiconductor region (p-type region) and an n-type semiconductor region (n-type region) is comb-shaped instead of straight, and the p-type regions and n-type regions are arranged alternately in parallel. This makes it possible to increase the area for detecting light and to improve sensitivity. Non-Patent Document 1 also discloses a photodiode in which an i-type semiconductor region (i-type region) is arranged at the boundary between each of the comb-shaped pn regions. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-219453 A [Non-patent literature]

[0005] [Non-Patent Document 1] Chong LI and 5 others, "Grating-enabled high-speed high-efficiency surface-illuminated silicon photodiodes", Optics Express, (USA), Optical Society of America, January 21, 2021, Vol. 29, No. 3, pp. 3458-3464. Summary of the Invention [Problem to be solved by the invention]

[0006] Carriers generated by the incidence of light drift and move at high speed in the depletion layer due to the electric field. However, in regions with high carrier concentration, the movement speed of minority carriers (holes in n-type regions, electrons in p-type regions) among the carriers generated by the incidence of light is slower than in the depletion layer. This is the reason why it takes time (slow detection speed) from the time light is incident until the photocurrent is detected (and thus the incidence of light is detected).

[0007] An object of the present invention is to provide a photodiode having a high detection speed. [Means for solving the problem]

[0008] In order to solve the above problems, the photodiode according to the present invention comprises: A first semiconductor portion which is a strip-shaped region made of a first semiconductor which is a p-type semiconductor or an n-type semiconductor; a second semiconductor portion which is a strip-shaped region having a width greater than that of the first semiconductor portion and which is made of a second semiconductor having a type opposite to that of the first semiconductor and a carrier concentration lower than that of the first semiconductor; It is characterized by having three or more light receiving sections arranged alternately in the width direction.

[0009] Here, the "semiconductor of the opposite type to the first semiconductor" in the second semiconductor refers to an n-type semiconductor when the semiconductor constituting the first semiconductor is a p-type semiconductor, and refers to a p-type semiconductor when the semiconductor constituting the first semiconductor is an n-type semiconductor.

[0010] The light receiving section in the photodiode according to the present invention has three or more first semiconductor sections and three or more second semiconductor sections arranged alternately in the width direction, and therefore has at least three semiconductor sections (a general term for the first semiconductor section and the second semiconductor section) arranged in the order of "first semiconductor section-second semiconductor section-first semiconductor section" or "second semiconductor section-first semiconductor section-second semiconductor section". In other words, there are two or more boundaries between the first semiconductor section and the second semiconductor section. Of course, it may have four or more semiconductor sections (i.e., three or more boundaries).

[0011] The boundary between the first semiconductor portion and the second semiconductor portion may be a straight line, or may have a long line length such as a comb-tooth or saw-tooth shape. The multiple boundaries may all have the same shape, or may each be different.

[0012] In the photodiode of the present invention, there are multiple first semiconductor sections or second semiconductor sections, and the semiconductor sections of the same type (i.e., the first semiconductor sections or the second semiconductor sections) may be electrically connected to each other in series or in parallel.

[0013] According to the photodiode of the present invention, the light receiving section includes a first semiconductor section and a second semiconductor section made of an opposite type semiconductor and having a lower carrier concentration and a wider width, so that the distance traveled by minority carriers, which move slowly, is shorter in the first semiconductor section, which has a higher carrier concentration and a narrower width, thereby making it possible to increase the detection speed of the photocurrent. As a result, for example, when the photodiode of the present invention is used as a light receiving element in an optical communication system, the transmission speed can be increased (the amount of data that can be received per unit time can be increased).

[0014] In addition, by making the width of the second semiconductor section, which has a lower carrier concentration, wider than that of the first semiconductor section, the width over which the depletion layer is formed is increased, and the capacitance of the photodiode can be reduced, which makes it possible to increase the upper limit of the frequency of light that can be detected, thereby widening the usable band (range of light frequencies). This also contributes to increasing the transmission speed in optical data transmission.

[0015] Since the second semiconductor portion has a lower carrier concentration than the first semiconductor portion, the second semiconductor portion can be regarded as a region of the pin junction made of an i-type semiconductor. In this case, the first semiconductor portion can be regarded as one of the regions of the pin junction made of a p-type semiconductor and the region made of an n-type semiconductor. The other of these two regions can be a region of the second semiconductor portion near a connection point with a wiring for extracting current. If the electrical resistance of such a region near the connection point is too high, current will not flow through the wiring, so it is preferable to dope the region with more dopant impurities than the other regions of the second semiconductor portion.

[0016] In the photodiode according to the present invention, the area of ​​the light receiving portion can be increased because a total of three or more strip-shaped first and second semiconductor portions are arranged in the width direction. For example, the light receiving portion can be configured to have a size large enough to include a circle with a diameter of 30 μm or more. This makes it possible to reliably receive (detect) optical signals transmitted through a multimode optical fiber that has a larger core diameter than a single-mode optical fiber that is commonly used in optical data transmission.

[0017] In the photodiode according to the present invention, the thickness of the light receiving portion can be set to 5 μm or less, which makes it easier to form a depletion layer throughout the entire thickness direction, thereby making it possible to increase the carrier movement speed.

[0018] In the photodiode according to the present invention, the width of the second semiconductor portion may be 2 μm or more. By widening the width of the second semiconductor portion in this manner, the capacitance of the photodiode can be made sufficiently small and the upper limit of the frequency of light that can be detected can be made sufficiently high, thereby enabling the transmission speed in optical data transmission to be sufficiently high.

[0019] On the other hand, the width of the first semiconductor portion can be 1 / 2 or less of the width of the second semiconductor portion (1 μm or less when the width of the second semiconductor portion is 2 μm or more as described above). This makes it possible to narrow the area occupied by the first semiconductor portion when forming the light receiving portion within a predetermined region, thereby ensuring a sufficient width for the second semiconductor portion. Also, the travel distance of minority carriers in the first semiconductor portion can be shortened.

[0020] In the photodiode according to the present invention, a grating may be provided on the surface of the light receiving section. As a result, most of the light incident on the surface of the light receiving section is diffracted by the grating when it enters the inside of the light receiving section, and travels with a component in a direction perpendicular to the thickness direction (in-plane direction) in the light receiving section, so that the optical path length in the light receiving section can be lengthened, and light exceeding the critical angle is totally reflected and confined in the light receiving section, so that the optical path length in the light receiving section can be further lengthened. Therefore, the probability that light is converted into carriers is increased, and the light detection sensitivity can be increased. In addition, since it is possible to suppress the incident light from passing through the thickness direction of the light receiving section without contributing to carrier formation, the thickness of the light receiving section can be made thinner, which also contributes to making the carrier movement speed faster.

[0021] Whether the grating is provided on the surface or side of the light receiving section, the direction of the grooves of the grating may be parallel or perpendicular to the direction in which the bands of the first semiconductor section and the second semiconductor section extend, or may even be inclined (neither parallel nor perpendicular) to the direction in which the bands extend.

[0022] In the photodiode according to the present invention, a part of the second semiconductor section may include a high-concentration region having a higher carrier concentration than the other part of the second semiconductor section. By connecting conductors to the high-concentration region of the second semiconductor section and the first semiconductor section, respectively, it is possible to detect the current flowing between them. In this case, the high-concentration region corresponds to the region opposite the first semiconductor section, out of the region made of p-type semiconductor and the region made of n-type semiconductor in the pin junction.

[0023] In the photodiode according to the present invention, a light shielding portion for shielding light to be detected may be provided on the surface of the first semiconductor portion. This can suppress the generation of minority carriers in the first semiconductor portion. Therefore, it is possible to suppress the waveform of the detected current from becoming dull due to the overlap of a current due to majority carriers and carriers (both electrons and holes) in the depletion layer generated in the second semiconductor portion and a current due to minority carriers having a slower moving speed than the majority carriers and the carriers. When a high concentration region is provided in the second semiconductor portion, it is preferable to provide a light shielding portion on the surface of the high concentration region as well. The material of the light shielding portion may be any of a conductor, a semiconductor, and an insulator, but by using a conductor, the light shielding portion can also be used as a shield to prevent electromagnetic waves from entering from the outside as noise. Effect of the Invention

[0024] According to the present invention, a photodiode with a high detection speed can be obtained. [Brief description of the drawings]

[0025] [Figure 1] 1A is a cross-sectional view showing a first embodiment of a photodiode according to the present invention, and FIG. 1B is a top view showing a semiconductor portion thereof. [Diagram 2] FIG. 4 is a top view showing a modified example of the light receiving section in the first embodiment. [Diagram 3] FIG. 4 is a schematic diagram showing that the photodiode of the first embodiment is regarded as a plurality of individual photodiodes connected in parallel. [Figure 4]5A is a cross-sectional view showing a photodiode according to a second embodiment, and FIG. 5B is a top view showing a light receiving portion thereof. [Diagram 5] FIG. 11 is a top view showing a modified example of the light receiving section in the second embodiment. [Figure 6] FIG. 11 is a cross-sectional view showing a configuration having a grating according to a modified example of the second embodiment. [Figure 7] 13A is a cross-sectional view showing a photodiode according to a third embodiment, and FIG. 13B is a top view showing a light receiving portion thereof. [Figure 8] FIG. 11 is a cross-sectional view showing a photodiode according to a fourth embodiment. [Figure 9] FIG. 13 is a cross-sectional view showing a photodiode according to a modified example of the fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] An embodiment of a photodiode according to the present invention will be described with reference to FIGS.

[0027] (1) First embodiment 1 shows a photodiode 10 according to the first embodiment. The photodiode 10 has a substrate 191, an insulator layer 192 made of an insulator formed on the surface of the substrate 191, a light receiving portion 11 provided on the surface of the insulator layer 192, and a surface layer 193 provided so as to cover the light receiving portion 11.

[0028] The material of the substrate 191 may be, for example, silicon (Si). The material of the insulator layer 192 may be, for example, silicon oxide (SiO2). A known material, SOI (Silicon On Insulator) wafer, may be used as a combination of the silicon substrate 191 and the silicon oxide insulator layer 192. The materials of the substrate 191 and the insulator layer 192 are not limited to this example. The substrate 191 may be made of any material, regardless of whether it is conductive or not, and the insulator layer 192 may be made of any material, so long as it is an insulator. When the substrate 191 made of an insulator is used, the insulator layer 192 may not be provided separately.

[0029] The surface layer 193 is provided to prevent the wiring and the like described below from corroding, and to transmit the light to be detected and introduce it to the light receiving unit 11. The material of the surface layer 193 is an insulator that is transmittable by the light to be detected.

[0030] The light receiving section 11 includes a plurality of strip-shaped (linear) first semiconductor sections 111 made of a first semiconductor that is an n-type semiconductor, and a plurality of strip-shaped (linear) second semiconductor sections 112 made of a second semiconductor that is a p-type semiconductor (opposite type to the first semiconductor). These first semiconductor sections 111 and second semiconductor sections 112 are arranged alternately in the width direction of the strip. Note that, in the present invention, a minimum of three first semiconductor sections 111 and second semiconductor sections 112 are required, so one of the first semiconductor sections 111 and the second semiconductor sections 112 may be only one (in this case, the other may be two).

[0031] The carrier (hole) concentration in the p-type semiconductor of the second semiconductor portion 112 is lower than the carrier (electron) concentration in the n-type semiconductor of the first semiconductor portion 111. For example, the first semiconductor and the second semiconductor can be silicon doped with a donor and an acceptor, or gallium arsenide (GaAs) doped with a donor and an acceptor.

[0032] There is a bond at the boundary between adjacent first semiconductor portions 111 and second semiconductor portions 112. Since there are a total of three or more first semiconductor portions 111 and second semiconductor portions 112, there are a total of two or more such boundaries.

[0033] The width W2 of the second semiconductor portion 112 (the size in the direction perpendicular to the direction in which the band extends, or in the width direction of the band) is wider than the width W1 of the first semiconductor portion 111. In this embodiment, W1=0.3 μm and W2=3 μm (for convenience of illustration in FIG. 1, the width of the first semiconductor portion 111 is drawn wider than it actually is). These widths are not limited to the above example as long as W2>W1, but it is preferable that W1 be 1 μm or less in order to sufficiently shorten the moving distance of carriers in the first semiconductor portion 111, and it is preferable that W2 be 2 μm or more in order to sufficiently reduce the electrostatic capacitance of the photodiode.

[0034] The length L of the band of the first semiconductor portion 111 and the second semiconductor portion 112 is 50 μm in this embodiment, but is not limited to this example. However, the length L is preferably 30 μm or more. In addition, the entire width of the light receiving portion 11 is preferably 30 μm or more. By making both the length L and the entire width 30 μm or more, the light receiving portion 11 can include a circular area 91 with a diameter of 30 μm or more, so that an optical signal transmitted through a multimode optical fiber that is generally used in optical data transmission can be reliably incident, and this optical signal can be reliably detected.

[0035] The thickness t of the light receiving section 11 is set to 0.2 μm in this embodiment, but is not limited to this example. However, it is preferable that the thickness t is set to 5 μm or less in order to easily form a depletion layer over the entire thickness direction.

[0036] The first semiconductor portion 111 and the second semiconductor portion 112 are preferably formed by epitaxial growth on the upper surface of the insulator layer 192. In this case, the insulator layer 192 may be made of a single crystal, or may be formed by oxidizing the surface of the substrate 191 made of a single crystal, or the like.

[0037] In this embodiment, an n-type semiconductor is used for the first semiconductor portion 111 and a p-type semiconductor is used for the second semiconductor portion 112, but a p-type semiconductor may be used for the first semiconductor portion 111 and an n-type semiconductor may be used for the second semiconductor portion 112. In this case, the carrier (electron) concentration in the n-type semiconductor of the second semiconductor portion 112 is made lower than the carrier (hole) concentration in the p-type semiconductor of the first semiconductor portion 111.

[0038] A first wiring (first wiring portion) 121 is connected in parallel to the multiple first semiconductor portions 111, and a second wiring (second wiring portion) 122 is connected in parallel to the multiple second semiconductor portions 112. For these wirings, conductors separate from the first semiconductor portion 111 and the second semiconductor portion 112 can be used as shown in FIG.

[0039] A high-concentration region 113 having a higher carrier (electron) concentration than the other portions of the second semiconductor portion 112 is formed near the connection portion of the second semiconductor portion 112 with the second wiring portion 122. The carrier concentration in the high-concentration region 113 may be the same as the carrier concentration of the first semiconductor in the first semiconductor portion 111, or may be higher or lower than that. The high-concentration region 113 can be produced, for example, by forming a thin film in the region that will become the second semiconductor portion 112, and then irradiating the high-concentration region 113 with ions that will be acceptors so that the concentration in the high-concentration region 113 is higher than that in the other portions of the second semiconductor portion 112. The high-concentration region 113 has a lower electrical resistivity than the other portions of the second semiconductor portion 112. Since the carrier concentration in the first semiconductor portion 111 is higher than that in the second semiconductor portion 112, such a high-concentration region is not formed in the first semiconductor portion 111.

[0040] Alternatively, as shown in Fig. 2, the first wiring portion 121A may be formed integrally with the first semiconductor portion 111 by using the same first semiconductor as the first semiconductor portion 111, and the second wiring portion 122A may be formed integrally with the second semiconductor portion 112 by using the same second semiconductor as the second semiconductor portion 112. In the example of Fig. 2, the first wiring portion 121A and the first semiconductor portions 111, and the second wiring portion 122A and the second semiconductor portions 112 each have a comb-like shape. In this case, the second wiring portion 122A is a high-concentration region having a higher carrier (electron) concentration than the second semiconductor portion 112.

[0041] 1(b) and 2, the photodiode 10 of the first embodiment having n first semiconductor parts 111 and n second semiconductor parts 112 can be regarded as 2n photodiodes (referred to as individual photodiodes 101) connected in parallel, each having the first semiconductor part 111 as one electrode, the high concentration region as the other electrode, and the second semiconductor part 112 as a dielectric inserted between the electrodes. The capacitance C0 of each individual photodiode 101 is expressed as C0=εLt / (W2 / 2), where ε is the dielectric constant of the second semiconductor, and W2 / 2 is the thickness of the dielectric between the electrodes, assuming half the width of the second semiconductor part 112. The capacitance C of the entire photodiode 10 is the sum of the capacitances C0 of the individual photodiodes 101, and is therefore C=2n×εLt / (W2 / 2).

[0042] For example, silicon (dielectric constant ε ≒ 1×10 -10In the case where the photodiode 10 has 15 first semiconductor parts 111 and 15 second semiconductor parts 112 made of 1000 fF each (n=15) and has the above-mentioned dimensions (W1=0.3 μm, W2=3 μm, L=50 μm, t=0.2 μm), the capacitance C of the entire photodiode 10 is about 20 fF. The smaller the capacitance of the photodiode, the higher the upper limit of the detectable light frequency can be, and the wider the usable band (range of light frequency), so that the transmission speed (amount of data that can be transmitted per unit time) in optical data transmission can be increased. In general, if the capacitance of the photodiode is 200 fF or less, data can be transmitted at a speed of 20 Gbps or more, so that the transmission speed can be sufficiently increased by setting the capacitance C of the entire photodiode 10 to a small value of about 20 fF as in the above example.

[0043] The photodiode 10 of the first embodiment is used in the same manner as a conventional photodiode. During use, in order to form a large depletion layer, a reverse bias voltage may be applied so that the side of the first semiconductor portion 111 and the second semiconductor portion 112 made of an n-type semiconductor is positive and the side of the first semiconductor portion 111 made of a p-type semiconductor is negative, or the photodiode 10 may be used without applying such a reverse bias voltage. In either case, when light passes through the surface layer 193 and enters the light receiving portion 11, pairs of electrons and holes that become carriers are generated, and the photocurrent that flows due to the movement of these carriers is detected through the first wiring portion 121 (121A) and the second wiring portion 122 (122A), thereby detecting the incidence of light.

[0044] According to the photodiode 10 of the first embodiment, by using the light receiving section 11 including the first semiconductor section 111 and the second semiconductor section 112 made of a semiconductor of the opposite type to the first semiconductor section 111 and having a lower carrier concentration and a wider width, the distance traveled by the minority carriers, which have a slower moving speed, is shortened in the first semiconductor section 111, which has a higher carrier concentration and a narrower width, and the detection speed of the photocurrent can be increased. On the other hand, by making the width of the second semiconductor section 112, which has a lower carrier concentration, wider than the first semiconductor section 111, the width in which the depletion layer is formed is increased, and the electrostatic capacitance can be reduced, so that the upper limit of the frequency of the light that can be detected can be increased, and the usable band can be widened. Furthermore, since three or more strip-shaped first semiconductor sections 111 and second semiconductor sections 112 are lined up in the width direction, the region for detecting light can be prevented from becoming narrow.

[0045] (2) Second embodiment FIG. 4 shows a photodiode 20 of the second embodiment. In this photodiode 20, a grating 21 is formed on the surface (surface on the surface layer 193 side) of the light receiving portion 11A. The configuration of the light receiving portion 11A is the same as the configuration of the light receiving portion 11 in the first embodiment, except that the grating 21 is formed. That is, the light receiving portion 11A is composed of a first semiconductor, which is an n-type semiconductor, and a second semiconductor portion 112A, which is a p-type semiconductor (opposite type to the first semiconductor) and has a lower carrier density than the first semiconductor, and is wider than the first semiconductor portion 111A, arranged alternately in a total of three or more. Although not shown in FIG. 4, the second embodiment also has wiring and high concentration regions similar to those of the first embodiment. Also, the first semiconductor portion 111A and the second semiconductor portion 112A can be modified in various ways similar to those of the first embodiment.

[0046] The grating 21 has grooves 211 formed on the surface of the light receiving section 11 and arranged parallel to each other, and ridges 212 between adjacent grooves 211. In the example shown in FIG. 4, a grating having grooves 211 and ridges 212 with a rectangular cross section perpendicular to the grooves 211 is used, but a grating having another shape such as a triangle may be used. In the example shown in FIG. 4, the grooves 211 and ridges 212 are provided parallel to the direction in which the bands of the first semiconductor section 111 and the second semiconductor section 112 extend, but they may be provided in a direction perpendicular to those bands (FIG. 5), or in a direction inclined to those bands (a direction that is neither parallel nor perpendicular). The cross-sectional shape of the grooves 211 and ridges 212 is not limited to the rectangular shape shown in FIG. 4(a).

[0047] In the example of Fig. 4, the grating 21 is formed on the surface of the light receiving section 11A, but as shown in Fig. 6, a separate grating 21A may be provided on the surface of the light receiving section 11 (where no grating is formed) similar to that of the first embodiment. The material of the grating 21A has a refractive index different from that of the surface layer 193 and transmits light to be detected. In this example, too, the extending direction of the grooves 211A and the peaks 212A and the cross-sectional shapes of the grooves 211A and the peaks 212A are not limited to the rectangular shape shown in Fig. 6.

[0048] When using the photodiode 20 of the second embodiment, a reverse bias voltage may or may not be applied, as in the first embodiment. When light is incident through the surface layer 193, it is diffracted by the grating 21 (21A). As a result, the light travels with a component parallel to each layer (such as the surface layer 193) in the light receiving section 11A (11), and the optical path length in the light receiving section 11A (11) can be lengthened. In addition, light exceeding the critical angle is totally reflected and confined in the light receiving section 11A (11), so that the optical path length in the light receiving section 11A (11) can be further lengthened. As a result, the probability that light is converted into carriers increases, so that the light detection sensitivity can be increased. Accordingly, it is possible to suppress the incident light from passing through the light receiving section 11A (11) in the thickness direction without contributing to carrier formation, and therefore the thickness of the light receiving section 11A (11) can be made thinner, which also contributes to making the carrier movement speed faster.

[0049] (3) Third embodiment 7 shows a photodiode 30 of the third embodiment. This photodiode 30 has a structure in which a substrate 191, an insulator layer 192, a light receiving portion 31, and a surface layer 193 are laminated in this order. The substrate 191, the insulator layer 192, and the surface layer 193 have the same configurations as those in the photodiode 10 of the first embodiment, and therefore detailed description thereof will be omitted.

[0050] The light receiving section 31 has a strip-shaped first semiconductor section 311 made of a first semiconductor which is an n-type semiconductor, a strip-shaped second semiconductor section 312 made of a second semiconductor which is a p-type semiconductor and has a carrier (hole) concentration lower than the carrier (electron) concentration of the first semiconductor, and a strip-shaped third semiconductor section 313 made of a third semiconductor which is a p-type semiconductor and has a carrier (hole) concentration higher than the second semiconductor (which may be the same as the carrier concentration of the first semiconductor, or may be higher or lower). The third semiconductor section 313 has a role similar to that of the high concentration region 113 in the first embodiment, so there is no need to provide the high concentration region 113 in the third embodiment.

[0051] The light receiving section 31 is made up of a plurality of sets of first semiconductor section 311-second semiconductor section 312-third semiconductor section 313-second semiconductor section 312 arranged in the width direction. This configuration can be considered as the first semiconductor section 311 and the second semiconductor section 312 arranged alternately in the width direction, with the third semiconductor section 313 formed in a part of the second semiconductor section 312. When manufacturing the photodiode 30, a method can be used in which a thin film is formed by combining a section that will become the third semiconductor section 313 and the sections on both sides that will become the second semiconductor sections 312, and then irradiating the former section and the latter section with ions that will become acceptors so that they have different carrier concentrations.

[0052] The width of the second semiconductor portion 312 is wider than the widths of the first semiconductor portion 311 and the third semiconductor portion 313. In this embodiment, the widths of the first semiconductor portion 311 and the third semiconductor portion 313 are each 1 μm, and the width of the second semiconductor portion 312 is 3 μm, but this is not limited to this example.

[0053] The first and second semiconductors may each be made of silicon or gallium arsenide doped with a donor and an acceptor, as in the first embodiment, and the third semiconductor may also be made of a similar material.

[0054] A first wiring portion 321 is connected in parallel to the multiple first semiconductor portions 311, and a second wiring portion 322 is connected in parallel to the multiple third semiconductor portions 312.

[0055] In the photodiode 30 of the third embodiment, the first semiconductor portion 311 and the third semiconductor portion 313 function as electrodes of the photodiode. A depletion layer is formed mainly in the vicinity of the boundary between the second semiconductor portion 312 and the first semiconductor portion 311. The operation of this photodiode 30 is similar to that of the photodiode 10 of the first embodiment.

[0056] (4) Fourth embodiment 8 shows a photodiode 40 of the fourth embodiment. This photodiode 40 has a substrate 191, an insulator layer 192, a light receiving portion 11, and a surface layer 193 similar to those of the photodiode 10 of the first embodiment, and further has a light shielding portion 41 on the surface of the light receiving portion 11 (between the light receiving portion 11 and the surface layer 193) facing the first semiconductor portion 111. The light shielding portion 41 is a thin-film member, and is made of a material that is a conductor and does not transmit light to be detected. Note that the material of the light shielding portion 41 may be any material that does not transmit light to be detected, and its electrical characteristics may be other than the conductor exemplified here. The light shielding portion 41 is not provided on the portion facing the second semiconductor portion 112.

[0057] In the photodiode 40 of the fourth embodiment, of the light incident through the surface layer 193, light that is incident directly above the first semiconductor portion 111 is blocked by the light-shielding portion 41 and does not enter the first semiconductor portion 111. On the other hand, light that is incident directly above the second semiconductor portion 112 enters the second semiconductor portion 112 and contributes to carrier generation. By preventing light from entering the first semiconductor portion 111 in this way, it is possible to suppress the generation of minority carriers (holes in the example of this embodiment) that move slowly in the first semiconductor portion 111, which has a high carrier concentration, and to prevent the waveform of the detected current from becoming dull.

[0058] Furthermore, when a light-shielding portion 41 made of a conductor is used, the light-shielding portion 41 can be used as a shield that prevents electromagnetic waves from entering from the outside as noise.

[0059] 9 shows a photodiode 40A according to a modification of the fourth embodiment. This photodiode 40A further includes a light-shielding portion 41A on the surface of the light-receiving portion 31 in a portion facing the first semiconductor portion 311 and the third semiconductor portion 313, in addition to the photodiode 30 according to the third embodiment. This makes it possible to suppress the generation of minority carriers (holes in the first semiconductor portion 311 and electrons in the third semiconductor portion 313) that move slowly in the first semiconductor portion 311 and the third semiconductor portion 313, which have a high carrier concentration, as in the above-described photodiode 40. In this case, too, by using a conductive material for the light-shielding portion 41A, it is possible to use it as a shield that prevents electromagnetic waves from entering from the outside as noise.

[0060] Although a number of embodiments and modifications of the photodiode according to the present invention have been described above, the present invention is not limited to these embodiments and modifications, and further modifications are possible.

[0061] In addition, the above-described embodiments and their modified examples can be appropriately combined. For example, the photodiode 40 of the third embodiment does not have a grating, but the photodiode 40 of the third embodiment may have a grating similar to that used in the second embodiment.

[0062] [Aspects] It will be apparent to those skilled in the art that the above-described exemplary embodiments are illustrative of the following aspects.

[0063] (Item 1) A photodiode according to one aspect of the present invention comprises: A first semiconductor portion which is a strip-shaped region made of a first semiconductor which is a p-type semiconductor or an n-type semiconductor; a second semiconductor portion which is a strip-shaped region having a width greater than that of the first semiconductor portion and which is made of a second semiconductor having a type opposite to that of the first semiconductor and a carrier concentration lower than that of the first semiconductor; It has three or more light receiving sections arranged alternately in the width direction.

[0064] (Item 2) The photodiode according to item 2 is the photodiode according to item 1, wherein the light receiving portion has a size capable of containing a circle having a diameter of 30 μm or more.

[0065] (Item 3) The photodiode according to item 3 is the photodiode according to item 1 or 2, in which a grating is formed on a surface of the light receiving portion.

[0066] (Item 4) The photodiode according to item 4 is the photodiode according to any one of items 1 to 3, further comprising a high concentration region in a part of the second semiconductor portion, the high concentration region having a higher carrier concentration than other parts of the second semiconductor portion.

[0067] (Item 5) The photodiode according to item 5 is the photodiode according to items 1 to 4, wherein the light receiving portion has a thickness of 5 μm or less.

[0068] (Item 6) The photodiode according to item 6 is the photodiode according to items 1 to 5, wherein the width of the second semiconductor portion is 2 μm or more.

[0069] (Item 7) The photodiode according to item 7 is the photodiode according to items 1 to 6, wherein the width of the first semiconductor portion is equal to or less than half the width of the second semiconductor portion.

[0070] (Item 8) The photodiode according to item 8 is the photodiode according to items 1 to 7, further comprising a light shielding portion on a surface of the first semiconductor portion that shields light to be detected.

[0071] (Item 9) The photodiode according to item 9 is the photodiode according to item 4, further comprising a light shielding portion for shielding light to be detected on surfaces of the first semiconductor portion and the high-concentration region.

[0072] (Item 10) The photodiode according to item 10 is the photodiode according to item 8 or 9, wherein the light-shielding portion is made of a conductor. [Explanation of symbols]

[0073] 10, 20, 30, 40, 40A...Photodiode 101…Individual photodiode 11, 11A, 31... Light receiving section 111, 111A, 311...First semiconductor part 112, 112A, 312...Second semiconductor part 113...High concentration area 121, 121A, 321...1st wiring section 122, 122A, 322...2nd wiring section 191... Circuit board 192...insulating layer 193…Surface layer 21, 21A…Grating 211, 211A…Grating grooves 212, 212A...Grating Mountain 313…Third Semiconductor Department 41, 41A…shading part

Claims

1. A first semiconductor portion which is a strip-shaped region made of a first semiconductor which is a p-type semiconductor or an n-type semiconductor; a second semiconductor portion which is a strip-shaped region having a width greater than that of the first semiconductor portion and which is made of a second semiconductor which is an opposite type semiconductor to the first semiconductor and has a lower carrier concentration than the first semiconductor; A photodiode having three or more light receiving sections arranged alternately in the width direction.

2. 2. The photodiode according to claim 1, wherein the light receiving portion has a size capable of containing a circle with a diameter of 30 μm or more.

3. 3. The photodiode according to claim 1, wherein a grating is formed on a surface of the light receiving portion.

4. 3. The photodiode according to claim 1, wherein a part of the second semiconductor portion comprises a high concentration region having a carrier concentration higher than that of another part of the second semiconductor portion.

5. 3. The photodiode according to claim 1, wherein the light receiving portion has a thickness of 5 μm or less.

6. 3. The photodiode according to claim 1, wherein the second semiconductor portion has a width of 2 μm or more.

7. 3. The photodiode according to claim 1, wherein the width of the first semiconductor portion is equal to or smaller than half the width of the second semiconductor portion.

8. The photodiode according to claim 1 , further comprising a light shielding portion on a surface of the first semiconductor portion, the light shielding portion shielding light to be detected.

9. The photodiode according to claim 4 , further comprising a light shielding portion for shielding light to be detected on surfaces of the first semiconductor portion and the high concentration region.

10. The photodiode according to claim 8 , wherein the light shielding portion is made of a conductor.

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