Photodetector

Abstract

To provide a light detector that is suitable for measuring light with a long wavelength and is easily manufactured.SOLUTION: A light detector 10 comprises: a substrate 11 made of a p-type semiconductor or an n-type semiconductor; a light-shielding layer 12 that covers part or all of one surface of the substrate 11; a light introduction part 121 that is provided at a position other than a range covered by the light-shielding layer 12 on the one surface of the substrate 11 or provided on a side surface of the substrate 11; a charge capture part 13 that at the one surface and under the light-shielding layer 12, is provided apart from the light introduction part 121 and is made of a semiconductor of a type opposite to that of the substrate 11; and a measurement part 14 electrically connected to the charge capture part 13.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a photodetector, and more particularly to a device that uses semiconductors to detect light having a wavelength within a specific range. [Background technology]

[0002] Conventionally, photodetectors have been used that include a pn junction type semiconductor device in which a p layer made of a p-type semiconductor and an n layer made of an n-type semiconductor are joined together. For example, Patent Document 1 describes a photodetector in which a pn junction is formed by diffusing impurities from the surface of an n layer made of an n-type semiconductor to form a p layer made of a p-type semiconductor in a part of the surface side of the n layer.

[0003] When light is incident on the surface (incident surface) of the p-layer or n-layer of such a semiconductor device, the light is gradually absorbed as it travels through the semiconductor. If the intensity of the light at the incident surface is I0 and the depth from the incident surface is x, the intensity of the light at depth x, I(x), is expressed by the Beer-Lambert law as I(x) = I0·exp(-αx). Here, α is the absorption coefficient, and the shorter the wavelength of the light, the larger the absorption coefficient α. Therefore, the longer the wavelength of the light, the more likely it is that light will be absorbed deeper from the incident surface.

[0004] When light is absorbed by a semiconductor, electron-hole pairs are generated. Of these electrons and holes, those generated within the depletion layer of the p-n junction or within a certain distance (diffusion distance) from the depletion layer migrate to the n-layer and the holes to the p-layer, generating a photocurrent. Light incident on the semiconductor device is detected by detecting this photocurrent. Because of the relationship between the wavelength of light and the depth at which light absorption occurs, the deeper the p-n junction is located, the longer the wavelength of the detected light. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 55-017461 Summary of the Invention [Problem to be solved by the invention]

[0006] In order to detect long wavelength light in the photodetector described in Patent Document 1, it is necessary to thicken the p-layer so that the p-n junction is positioned deeper. However, in actual manufacturing, the range of depth that impurities can reach by diffusion is limited, making it difficult to thicken the p-layer.

[0007] The problem to be solved by the present invention is to provide a photodetector that is suitable for measuring light of long wavelengths and that is easy to manufacture. [Means for solving the problem]

[0008] In order to solve the above problems, the photodetector according to the present invention comprises: a) a substrate made of a p-type semiconductor or an n-type semiconductor; b) a light-shielding layer covering a part or all of one surface of the substrate; c) a light introducing portion provided on one surface of the substrate at a position other than the area covered with the light-shielding layer or on a side surface of the substrate; d) at least two charge trapping sections made of a semiconductor of the opposite type to that of the substrate, the charge trapping sections being spaced apart from the light introducing section and being disposed at different distances from the light introducing section on one surface of the substrate; e) a measuring unit electrically connected to the charge trapping unit; Equipped with before Telegraph Each of the load capturing sections is entirely located below the light blocking layer and spaced apart from the light introducing section. It is characterized by:

[0009] The "semiconductor of the opposite type to the substrate" in the charge trapping portion refers to an n-type semiconductor when the semiconductor constituting the substrate is a p-type semiconductor, and refers to a p-type semiconductor when the semiconductor constituting the substrate is an n-type semiconductor.

[0010] The light to be measured, which enters the substrate from the light introduction section, is gradually absorbed by the semiconductor of the substrate as it travels through the substrate, generating pairs of holes and electrons. Of the generated holes and electrons, the charges, which are minority carriers in the semiconductor of the substrate (electrons if the semiconductor of the substrate is p-type, and holes if it is n-type), move within the substrate. Of these minority carriers, those generated within a specified range from the charge trap section are captured by the charge trap section. The measurement section measures the current generated between the substrate and the charge trap section as a result of the charge being captured by the charge trap section, or the voltage of the charge trap section (the potential of the charge trap section, or the voltage between a reference position and the charge trap section).

[0011] If the distance from the point where light enters the substrate (incident position) is r, the intensity of the light being measured traveling through the substrate is expressed as I(r) = I0·exp(-αr), where α is the absorption coefficient determined by the wavelength and the substrate material. As mentioned above, the shorter the wavelength of light, the greater the absorption coefficient α, and therefore the light intensity I(r) attenuates more rapidly as the wavelength becomes shorter. Therefore, at a certain distance along the optical path within the substrate from the incident position, almost no light with wavelengths shorter than a certain wavelength reaches the substrate, and only light with wavelengths longer than that reaches the substrate. This long-wavelength light is absorbed, generating hole-electron pairs. This allows light with wavelengths longer than a predetermined wavelength to be detected, depending on the distance between the light entrance and the charge trap (if the charge trap is located on the first surface) or the distance between the position on the other surface facing the light entrance and the charge trap (if the charge trap is located on the second surface). When light of different wavelengths is incident at the same intensity, the longer the wavelength, the less the degree of light attenuation, and therefore the higher the detected intensity at the charge capture section, making it possible to identify the wavelength of the detected light.

[0012] As described above, in conventional photodetectors, the wavelength of detected light depends on the depth of the pn junction from the surface of the semiconductor layer, making it difficult to manufacture when the wavelength of the light to be measured is long. In contrast, according to the present invention, a charge trapping section is provided on the surface of the substrate and the light introducing section is provided at a different position. This allows the distance between the light introducing section and the charge trapping section to be set as desired, making it easy to manufacture a photodetector suitable for measuring light of long wavelengths. Furthermore, the photodetector according to the present invention has the advantage of being easy to manufacture even when measuring light of a relatively short wavelength.

[0013] The charge trapping section may be provided on the side of the substrate where the light-shielding layer is provided (the one surface), or on the opposite surface (the other surface). When a light introduction section is provided on the one surface and light is introduced in a direction oblique to the substrate, when measuring long-wavelength light, the depth at which charges are generated after traveling a long distance within the substrate is closer to the other surface than to the one surface. In such cases, it is preferable to provide the charge trapping section on the other surface, as this increases the detection intensity of the charges.

[0014] In the photodetector according to the present invention, rather than covering only a portion of the substrate surface with a light-shielding layer and providing a light introduction section in the non-light-shielding section, the entire substrate surface is covered with a light-shielding layer and a light introduction section is provided on the side of the substrate, which makes it easier to introduce light into the substrate at an angle close to parallel to the substrate. The closer the optical path in the substrate is to the substrate, the longer the optical path length in the substrate can be, enabling measurements at longer wavelengths.

[0015] In the photodetector of the present invention, it is preferable that at least two of the charge capture sections are provided on one surface below the light-shielding layer, or on the other surface of the substrate facing the light-shielding layer, at different distances from the light introducing section.

[0016] By providing at least two charge trapping units at different distances from the light introduction unit, light of two or more wavelengths can be distinguishably detected as described below. As described above, the light to be measured that enters the substrate from the light introduction unit is gradually absorbed by the semiconductor of the substrate as it travels through the substrate, generating pairs of holes and electrons. The generated holes and electrons, which are minority carriers, move within the substrate and are captured by the charge trapping unit closest to the location where the charge was generated. The measurement unit measures the current generated between the substrate and each charge trapping unit as each charge trapping unit captures the charge, or the voltage of each charge trapping unit (the potential of the charge trapping unit, or the voltage between the reference position and the charge trapping unit). As described above, the shorter the wavelength, the more rapidly the light intensity I(r) attenuates. Accordingly, the number of charges captured by the multiple charge trapping units and the current or voltage values ​​at each charge trapping unit measured by the measurement unit attenuate correspondingly as the wavelength of the light to be detected decreases and the distance from the incident position increases. Therefore, light of two or more wavelengths can be distinguishably detected based on the current or voltage values ​​at each charge trapping unit.

[0017] For example, preliminary experiments are performed for multiple light beams with known wavelengths, each with a different wavelength, to determine the degree of attenuation for each wavelength. The degree of attenuation is then compared with the measurement results for light with an unknown wavelength to determine the wavelength of the measured light. Based on this principle, if the light to be measured is monochromatic, the wavelength can be identified based on the degree of attenuation described above. Furthermore, if the light to be measured is a superposition of multiple wavelengths, the sum of the data obtained in the preliminary experiments for each wavelength can be determined for multiple examples with different intensity ratios (weighting) for each wavelength, and each of these examples can be compared with the measurement results for the light to be measured.

[0018] Patent Document 1 describes a method for manufacturing a photodetector having two pn junctions in the thickness direction of a substrate by two steps: forming an n-layer by epitaxial growth on a substrate made of a p-type semiconductor, and then forming a p-layer by diffusing impurities into the n-layer. In contrast, the photodetector of the present invention has two or more charge trapping units disposed on one or the other surface of the substrate, allowing the two or more charge trapping units to be fabricated in a single step. Thus, the photodetector of the present invention also has the advantage of simplifying the process for fabricating two or more charge trapping units.

[0019] The at least two charge trapping units are typically arranged side by side in one direction, which allows for suitable detection of light traveling in that direction or in a direction tilted from that direction toward a direction perpendicular to the substrate.

[0020] The at least two charge trapping units may be arranged side by side in two or more directions. In this configuration, by detecting light traveling in the two or more directions or in a direction inclined from each of the two or more directions to the direction perpendicular to the substrate, detection sensitivity can be increased when the intensity of each light is weak. Alternatively, in this case, by setting the distance between the position where the light enters the substrate and each charge trapping unit to a different value for each direction in which the charge trapping units are arranged, the relationship between this distance and the detected intensity can be obtained at finer intervals, thereby increasing measurement accuracy.

[0021] As described above, the at least two charge trapping portions can be arranged side by side in at least one direction.

[0022] Alternatively, the at least two charge trapping portions may be arranged without being aligned in one or more directions. For example, the charge trapping portions may be arranged in a spiral shape with the light introducing portion at the center.

[0023] On the other hand, even when measuring light of only one wavelength, two or more charge trapping units can be provided. That is, in the photodetector according to the present invention, two or more charge trapping units may be located at equal distances from the incident position. If the incident position is a point, multiple charge trapping units will be located on a circumference at a predetermined distance from the incident position. If the incident position is linear, multiple charge trapping units will be located on a line at a predetermined distance from the incident position. By using two or more charge trapping units in this way, measurement accuracy can be improved.

[0024] Furthermore, the photodetector according to the present invention can have the following additional features regardless of the number of charge trapping units.

[0025] In a case where only a portion of the substrate surface is covered with a light-shielding layer and a light introduction section is provided in the non-light-shielding portion of the surface, the light introduction section may further include a sunken portion in which a portion of the substrate is sunken from the surface. In a photodetector having such a sunken portion, light can be introduced into the substrate at an angle closer to parallel to the substrate by making light incident on the substrate from the sidewall of the sunken portion on the charge capture section side, thereby enabling measurements at long wavelengths.

[0026] The photodetector having the sunken portion may further include a reflector for reflecting light within the sunken portion. By appropriately setting the angle of the reflector, the angle of light incident on the substrate from the sidewall of the sunken portion can be appropriately set.

[0027] In the photodetector according to the present invention, the light introducing section may be provided with an incident direction adjusting section that selectively passes light incident on the substrate from a predetermined direction, thereby generating charges only on the optical path of light incident from the predetermined direction and preventing unnecessary charges from being generated at various positions within the substrate due to light being incident on the substrate from various directions, thereby improving measurement accuracy.

[0028] In the photodetector according to the present invention, some of the minority carriers generated in the substrate reach both sides of the charge trapping section (between the charge trapping section and the light introducing section, or on the side opposite the light introducing section as viewed from the charge trapping section) rather than reaching the charge trapping section. Such charges may end up being captured by the charge trapping section, even though they should not be captured by the charge trapping section. Furthermore, when two or more charge trapping sections are provided, minority carriers may be captured not only by the charge trapping section closest to the position where the hole-electron pair was generated, but also by nearby charge trapping sections that should not be captured by the charge trapping section. Such capture of minority carriers by charge trapping sections that should not be captured by the charge trapping section may result in a decrease in resolution.

[0029] Therefore, in the photodetector according to the present invention, a trap section made of the same type of semiconductor as the semiconductor of the charge trap section (an n-type semiconductor when the charge trap section is made of an n-type semiconductor, or a p-type semiconductor when the charge trap section is made of a p-type semiconductor) can be provided between the charge trap section and the light introducing section, and / or on the opposite side of the charge trap section from the light introducing section. When two or more charge trap sections are provided, a trap section can also be provided between two adjacent charge trap sections. By providing such a trap section, minority carriers that should not be captured by the charge trap section and that reach the position of the trap section rather than the position of the charge trap section can be removed by the trap section, thereby improving measurement accuracy.

[0030] On the other hand, the detection intensity can be increased by moving charges that reach both sides of the charge trapping section, rather than the charge trapping section, toward the charge trapping section. Therefore, the photodetector according to the present invention may include a block section between the charge trapping section and the light introducing section, and / or on the opposite side of the light introducing section from the charge trapping section. The block section is made of a semiconductor of the same type as the semiconductor of the substrate but with a higher impurity concentration than the semiconductor of the substrate. When two or more charge trapping sections are provided, a block section can also be provided between two adjacent charge trapping sections. By providing such a block section, charges, which are minority carriers in the semiconductor of the substrate, are subjected to a repulsive force from the block section toward the charge trapping section due to the potential generated by the block section, thereby increasing the charge captured by the charge trapping section. As a result, measurement accuracy can be improved. [Effects of the Invention]

[0031] According to the present invention, it is possible to obtain a photodetector that is suitable for measuring light of long wavelengths and is easy to manufacture. [Brief explanation of the drawings]

[0032] [Figure 1] 1 is a schematic configuration diagram showing a first embodiment of a photodetector according to the present invention. [Figure 2] FIG. 3 is a diagram showing the operation of the photodetector according to the first embodiment. [Figure 3] FIG. 2 is a diagram schematically showing the intensities of short-wavelength and long-wavelength light within a substrate. [Figure 4] FIG. 2 is a diagram schematically showing an example of the measured intensities of short-wavelength and long-wavelength light. [Figure 5] FIG. 4 is a diagram showing a modified example of the photodetector according to the first embodiment. [Figure 6] FIG. 10 is a partially enlarged view showing another modified example of the photodetector according to the first embodiment, which has a light-transmitting member. [Figure 7] FIG. 10 is a diagram showing another modified example of the photodetector according to the first embodiment, which has an incident direction selection filter. [Figure 8] FIG. 10 is a diagram showing another modified example of the photodetector of the first embodiment, which has a plurality of light introducing parts. [Figure 9] FIG. 2 is a schematic configuration diagram showing a second embodiment of a photodetector according to the present invention. [Figure 10] 8A to 8C are diagrams showing the operation of the photodetector according to the second embodiment. [Figure 11] FIG. 10 is a schematic configuration diagram showing a third embodiment of a photodetector according to the present invention. [Figure 12] 10A to 10C are diagrams showing the operation of the photodetector according to the third embodiment. [Figure 13] FIG. 10 is a schematic configuration diagram showing a fourth embodiment of a photodetector according to the present invention. [Figure 14] 10A to 10C are diagrams showing the operation of the photodetector according to the fourth embodiment. [Figure 15] FIG. 10 is a diagram showing a modified example of the photodetector according to the fourth embodiment. [Figure 16] FIG. 10 is a schematic configuration diagram showing a fifth embodiment of a photodetector according to the present invention. [Figure 17] FIG. 11 is a diagram showing the operation of the photodetector according to the fifth embodiment. [Figure 18] FIG. 13 is a diagram showing a modified example of the photodetector according to the fifth embodiment. [Figure 19] FIG. 10 is a schematic configuration diagram showing a sixth embodiment of a photodetector according to the present invention. [Figure 20] FIG. 13 is a diagram showing the operation of the photodetector according to the sixth embodiment. [Figure 21] FIG. 10 is a schematic configuration diagram showing a seventh embodiment of a photodetector according to the present invention. [Figure 22] FIG. 13 is a diagram showing the operation of the photodetector according to the seventh embodiment. [Figure 23] 5A and 5B are diagrams showing an example of a photodetector having only one charge trapping unit, as a modification of the first embodiment, and its operation. [Figure 24] FIG. 10 is a diagram showing an example in which the modification of the first embodiment having only one charge trapping unit is further modified. [Figure 25] FIG. 10 is a diagram showing an example in which an incident direction selection filter is provided in a modification of the first embodiment that includes only one charge trapping unit. [Figure 26] FIG. 10 is a diagram showing an example of a photodetector that is a further modification of the modification of the first embodiment, and that includes a plurality of light introducing parts, each of which includes only one charge capturing part. [Figure 27] FIG. 10 is a diagram showing an example of a photodetector having only one charge trapping unit, as a modification of the second embodiment, and its operation. [Figure 28] 10A and 10B are diagrams showing an example of a photodetector having only one charge trapping unit, as a modification of the third embodiment, and its operation. [Figure 29] 13 is a diagram showing an example of a photodetector having only one charge trapping unit, as a modification of the fourth embodiment, and its operation. FIG. [Figure 30] FIG. 10 is a diagram showing an example in which the modification of the fourth embodiment having only one charge trapping portion is further modified. [Figure 31] FIG. 13 is a diagram showing an example of a photodetector having only one charge trapping unit, as a modification of the fifth embodiment, and its operation. [Figure 32] FIG. 13 is a diagram showing an example of a photodetector that is a further modification of the modification of the fifth embodiment, and that includes a plurality of light introducing parts, each of which includes only one charge capturing part, and its operation. [Figure 33] FIG. 13 is a diagram showing an example of a photodetector having only one charge trapping unit, as a modification of the sixth embodiment, and its operation. [Figure 34] FIG. 13 is a diagram showing an example of a photodetector having only one charge trapping unit, as a modification of the seventh embodiment, and its operation. DETAILED DESCRIPTION OF THE INVENTION

[0033] An embodiment of a photodetector according to the present invention will be described with reference to Figures 1 to 34. Note that the terms "upper" and "lower" are used in the following description, but these terms are used for convenience to indicate the relative positional relationship of components within the photodetector, and do not limit the orientation of the photodetector when in use.

[0034] (1) First embodiment (1-1) Configuration of the photodetector according to the first embodiment As shown in FIG. 1, the photodetector 10 of the first embodiment includes a substrate 11, a light-shielding layer 12, a charge trapping section 13, and a measuring section 14.

[0035] The substrate 11 is made of a p-type semiconductor. As the p-type semiconductor of the substrate 11, for example, a well-known material in which Si or Ge is doped with a trivalent impurity can be used.

[0036] The light-shielding layer 12 is formed on the surface (top surface) of the substrate 11. However, there is a region (non-light-shielding portion) on the surface of the substrate 11 where the light-shielding layer 12 is not provided, and this region becomes the light entrance portion 121. The light-shielding layer 12 is made of a material such as a metal such as Al, Au, or Cu, or a resin such as polyimide. Although not shown in FIG. 1 , the light-shielding layer 12 may also be provided on the side or bottom surface of the substrate 11. This prevents erroneous detection due to light entering from the side or bottom surface of the substrate 11 other than the light entrance portion 121. On the other hand, if light is prevented from entering from the side or bottom surface of the substrate 11 by, for example, placing a shield on the side or bottom of the substrate 11 when using the photodetector 10, there is no need to provide the light-shielding layer 12 on these side or bottom surfaces.

[0037] The charge trapping sections 13 are made of an n-type semiconductor, and a plurality of them are arranged in one direction on the surface of the substrate 11 between the surface and a portion of the light-shielding layer 12 other than the light introducing section 121. That is, each charge trapping section 13 is arranged at a distance from the light introducing section 121. Note that in addition to the charge trapping sections 13 arranged at a distance from the light introducing section 121, a charge trapping section 13 may also be provided on the surface of the substrate 11 facing the light introducing section 121. Although five charge trapping sections 13 are shown in FIG. 1, the number of charge trapping sections 13 is not particularly limited as long as it is two or more. As the n-type semiconductor of the charge trapping section 13, for example, a well-known material in which Si or Ge is doped with a pentavalent impurity can be used.

[0038] The charge trapping sections 13 are made of an n-type semiconductor, and a plurality of them are arranged in one direction on the surface of the substrate 11 between the surface and the portion of the light-shielding layer 12 other than the light-introducing section 121. That is, each charge trapping section 13 is arranged at a distance from the light-introducing section 121. Although not included in the present invention,In addition to the charge trapping portion 13 arranged at a distance from the light introducing portion 121, a charge trapping portion 13 may be provided on the surface of the substrate 11 facing the light introducing portion 121. Although five charge trapping portions 13 are shown in Fig. 1, the number of charge trapping portions 13 is not particularly limited as long as it is two or more. As the n-type semiconductor of the charge trapping portion 13, for example, a well-known material in which Si or Ge is doped with a pentavalent impurity can be used.

[0039] The measurement units 14 are electrically connected to the plurality of charge trapping units 13, one for each. In this embodiment, an ammeter is used as the measurement unit 14, which detects the current flowing between the substrate 11 and each charge trapping unit 13 and introduced into the measurement unit 14. Instead of an ammeter, a voltmeter may be used as the measurement unit 14, which measures the potential of the charge trapping unit 13 or the voltage between the charge trapping unit 13 and another reference position. The potential or voltage of the charge trapping unit 13 is generated when charges flow into and accumulate in the charge trapping unit 13. Alternatively, integrated transistors used in image sensors or the like may be used as the measurement unit 14. The measurement unit 14 does not necessarily have to be located near the substrate 11; charges may be transferred to a measurement unit 14 located at a distance for measurement. The various examples of the measurement unit 14 described here can also be applied to the measurement units in the second to seventh embodiments described below.

[0040] (1-2) Operation of the photodetector of the first embodiment 2 to 4, the operation of the photodetector 10 of the first embodiment will be described. When using this photodetector 10, light L to be measured is made incident on the light introducing section 121 in a direction tilted at a predetermined angle θ (<90°) from the surface of the substrate 11. As a result, the light L is refracted at the surface of the substrate 11 and then travels through the substrate 11 at an angle tilted with respect to the surface of the substrate 11. During this time, the light L is gradually absorbed by the semiconductor of the substrate 11, thereby generating charges C consisting of electron-hole pairs.

[0041] If the intensity of light L on the surface of the substrate 11 is I0 and the distance traveled by light L within the substrate 11 is x, the light intensity I(x) at distance x can be expressed by the Beer-Lambert law as I(x) = I0 exp(-αx) using the absorption coefficient α. For example, if the p-type (or n-type) semiconductor constituting the substrate 11 is Si doped with impurities, the absorption coefficient α is 10,000 cm for green light with a wavelength of approximately 500 nm. -1 , and 3000 cm for red light with a wavelength of approximately 650 nm. -1 , and 1000 cm for near-infrared light with a wavelength of approximately 800 nm. -1 Using these absorption coefficients α, the distance x at which the intensity of the incident light is attenuated by 90% (to 10% of the intensity at the surface of the substrate 11) is calculated. 90 α=10000cm -1 In the case of α=3000cm, the -1 In the case of α=1000cm, it is approximately 8μm. -1 In this case, the wavelength is approximately 24 μm. That is, the shorter the wavelength of the light L, the more rapidly it attenuates, and the light L is less likely to be absorbed at positions farther from the light introducing part 121. In contrast, as the wavelength of the light L becomes longer, the attenuation becomes more gradual, and the light L is absorbed not only at positions close to the light introducing part 121 but also at positions farther from it.

[0042] The charge C generated by the absorption of light diffuses within the substrate 11, and minority carriers of the charge C in the substrate 11 (electrons if the substrate 11 is made of a p-type semiconductor, or holes if the substrate 11 is made of an n-type semiconductor) are captured by the charge trapping unit 13 closest to the position where they were generated (where the light was absorbed). The movement of charge from the substrate 11 to the charge trapping unit 13 is detected as a current or voltage by a measuring unit 14 connected to the charge trapping unit 13.

[0043] The shorter the wavelength of the light L to be measured traveling through the substrate 11, the more rapidly it is absorbed and attenuated by the semiconductor of the substrate 11. The longer the wavelength, the more gradually the light is absorbed by the semiconductor of the substrate 11, resulting in a longer distance (see FIG. 3). Therefore, the charge generated by light absorption by the semiconductor of the substrate 11 decreases with increasing distance from the light introducing section 121, and almost no charge is generated at a certain distance from the light introducing section 121. Therefore, the number of charges captured by the charge trapping section 13 and the current or voltage value of each charge trapping section 13 measured by the measuring section 14 decrease with increasing distance from the charge trapping section 13 closest to the light introducing section 121 (see FIG. 4). This decrease is more rapid as the wavelength of the light to be measured decreases. Therefore, light of two or more wavelengths can be distinguishably detected based on the current or voltage values ​​of these multiple charge trapping sections 13. The wavelength of the light L can be determined, for example, by comparing the results with the results of a preliminary experiment conducted using light of a known wavelength.

[0044] In the conventional photodetector described in Patent Document 1, the wavelength of light detected depends on the depth of the pn junction from the surface of the semiconductor layer, making it difficult to manufacture when the wavelength of the light to be measured is long. In contrast, photodetector 10 of this embodiment is easy to manufacture because charge trapping unit 13 is provided on the surface of substrate 11 regardless of the wavelength of light to be detected.

[0045] Furthermore, the photodetector 10 of this embodiment is easy to manufacture in that a plurality of charge trapping portions 13 can be fabricated simultaneously by using, for example, an impurity diffusion method.

[0046] (1-3) Modification of the photodetector according to the first embodiment 1, impurities are diffused from the surface of substrate 11 to form charge trapping portion 13 having an upper surface flush with the upper surface of substrate 11. On the other hand, as shown in Fig. 5, charge trapping portion 13 may be formed directly on the upper surface of substrate 11, so that the upper surface of substrate 11 and the lower surface of charge trapping portion 13 are flush with each other. Such charge trapping portion 13 can be fabricated by, for example, epitaxial growth, and is particularly suitable for use when charge trapping portion 13 is made of a compound semiconductor.

[0047] As shown in FIG. 6, the light introducing section 121 may be provided with a light-transmitting member 15 made of a material that transmits the light to be measured. Because the light-transmitting member 15 has a refractive index higher than that of air, light L is refracted at the boundary between the outside and the light-transmitting member 15 (light introducing section 121). As a result, the angle θ2 of light L relative to the perpendicular to the substrate 11 within the light-transmitting member 15 is larger than the angle θ1 before it enters the light-transmitting member 15. This reduces the amount of light L that collides with the sidewall of the light introducing section 121 and does not enter the substrate 11 (see the x mark in FIG. 6) compared to when the light-transmitting member 15 is not present. This increases the intensity of light L that enters the substrate 11, thereby improving resolution. The light-transmitting member 15 can be made of materials such as SiO2, SiN, and various resins.

[0048] 7, an incident direction adjustment unit 16 may be provided above the light introducing unit 121 (on the opposite side from the substrate 11). The incident direction adjustment unit 16 shown in FIG. 7 is an incident direction selection filter that has a hole tilted in a specific direction with respect to the surface of the substrate 11 and introduces into the light introducing unit 121 only light that is incident in a direction that can pass through the hole. The incident direction adjustment unit 16 generates charges only on the optical path of light L incident from the direction. This prevents unnecessary charges from being generated at various positions within the substrate due to light being incident on the substrate from various directions, thereby improving measurement accuracy. Note that instead of an incident direction selection filter, a lens may be disposed and its angle changed to adjust the traveling direction of the light.

[0049] 8, a plurality of light introduction sections (non-light-shielding sections) (two in the example of the figure, a first light introduction section 1211 and a second light introduction section 1212) may be provided on the surface of the substrate, and a plurality of charge trapping sections 13 may be provided in at least one direction from each light introduction section. In the example of Fig. 8, the distance between adjacent charge trapping sections 13 is a, the distance between the first light introduction section 1211 and the charge trapping section 13 closest thereto is b, and the distance between the second light introduction section 1212 and the charge trapping section 13 closest thereto is b+0.5a. As a result, charges generated by light incident from the first light introducing portion 1211 are captured by the charge capturing portions 13 that are distances b, b+a, and b+2a away from the first light introducing portion 1211, and charges generated by light incident from the second light introducing portion 1211 are captured by the charge capturing portions 13 that are distances b+0.5a, b+1.5a, and b+2.5a away from the second light introducing portion 1211. This allows for measurements to be performed similarly to when the charge capturing portions 13 are arranged at intervals of 0.5a, and therefore allows for higher resolution than when the charge capturing portions 13 are arranged at intervals of a in the photodetector 10 of the first embodiment as in this modification.

[0050] (2) Second embodiment (2-1) Configuration of the photodetector according to the second embodiment FIG. 9 shows a photodetector 20 according to the second embodiment. The photodetector 20 includes a substrate 21, a light-shielding layer 22, a charge trapping section 23, and a measurement section 24. The substrate 21 and the light-shielding layer 22 are configured similarly to the substrate 11 and the light-shielding layer 12 according to the first embodiment, and the light-shielding layer 22 is provided with a light-introducing section 221. A plurality of charge trapping sections 23 are arranged side by side on the surface (rear surface 212) of the substrate 21 opposite the surface 211 on which the light-shielding layer 22 is provided, at positions facing the light-shielding layer 22 (a portion without the light-introducing section 221). Therefore, each charge trapping section 23 is arranged at a distance from the region of the rear surface 212 that faces the light-introducing section 221. Similar to the charge trapping section 13 according to the first embodiment, the charge trapping section 23 is formed by diffusing impurities from the surface (rear surface 212) of the substrate 21. As in the modified example of the first embodiment, the charge trapping units 23 may be fabricated by epitaxial growth, etc. Each charge trapping unit 23 is connected to a measuring unit 24 similar to that in the first embodiment.

[0051] (2-2) Operation of the photodetector according to the second embodiment The operation of the photodetector 20 of the second embodiment will be described with reference to FIG. 10 . When using this photodetector 20, light L to be measured is incident on the light introducing section 221 in a direction inclined relative to the surface 211 of the substrate 21. As a result, the light L travels through the substrate 21 in a direction inclined relative to the surface 211 of the substrate 21, thus increasing in depth from the surface 211. As the light L travels through the substrate 21, it is gradually absorbed, thereby generating charges C consisting of electron-hole pairs. Of the generated electrons and holes, minority carriers of the substrate 21 (electrons in the example of FIG. 10 ) are captured by the charge capturing section 23 closest to the position where they were generated. As in the first embodiment, the current or voltage generated by this charge capture is measured by the measuring section 24, and light of two or more wavelengths can be distinguished and detected based on the values ​​of these currents or voltages.

[0052] In the photodetector 20 of the second embodiment, the charge trapping unit 23 is provided on the back surface 212 of the substrate 21, i.e., at a position deep from the front surface 211 on which the light L is incident, and is therefore suitable for trapping charges generated after the light L travels a relatively long distance as it travels deeper from the front surface 211. By detecting the light L that has traveled a long distance in this way, it is possible to distinguish and detect light with longer wavelengths. On the other hand, by thinning the substrate 21 in the configuration of the second embodiment, it is also possible to measure light with a relatively short wavelength (for example, visible light).

[0053] (3) Third embodiment (3-1) Configuration of the photodetector according to the third embodiment 11 shows a photodetector 30 according to the third embodiment. The photodetector 30 includes a substrate 31, a light-shielding layer 32, a charge capture unit 33, and a measurement unit 34. A side of the substrate 31 serves as a light introducing unit 321.

[0054] The substrate 31 is made of a p-type or n-type semiconductor (the former in FIG. 11 ) as in the first embodiment. The same p-type or n-type semiconductors as the substrate 11 and charge trapping portion 13 in the first embodiment can be used. The light-shielding layer 32 covers the entire surface of one of the substrates 31. When the substrate 31 is made of a p-type semiconductor, the charge trapping portion 33 is made of an n-type semiconductor, and when the substrate 31 is made of an n-type semiconductor, the charge trapping portion 33 is made of a p-type semiconductor. The material of the light-shielding layer 32 can be the same as that of the light-shielding layer 12 in the first embodiment.

[0055] A plurality of charge trapping sections 33 are provided on the surface of substrate 31, aligned in one direction. While FIG. 11 shows an example in which five charge trapping sections 33 are provided, the number of charge trapping sections 33 is not particularly limited as long as it is two or more. Furthermore, while FIG. 11 shows the upper surface of substrate 31 and the upper surface of charge trapping sections 33 at the same height, the upper surface of substrate 31 and the lower surface of charge trapping sections 33 may also be at the same height. Furthermore, while FIG. 11 shows the charge trapping sections 33 provided on the surface of substrate 31 on the light-shielding layer 32 side, they may also be provided on the surface (back surface) of substrate 31 on the opposite side. One measuring section 34 is provided for each of the plurality of charge trapping sections 33.

[0056] (3-2) Operation of the photodetector of the third embodiment The operation of the photodetector 30 of the third embodiment will be described with reference to FIG. 12 . When using this photodetector 30, light L to be measured is incident on the light introducing section 321 from the side of the substrate 31 in a direction parallel to the surface of the substrate 31. As a result, the light L travels through the substrate 31 in a direction parallel to the surface of the substrate 31. This is similar to the photodetector 10 of the first embodiment in that charges C are generated as the light L travels through the substrate 31, that minority carriers in the substrate 31 among the generated charges C are captured by the charge capturing section 33 closest to the position where the charges C were generated, that the movement of the charges C is detected as a current or a voltage by the measuring section 34, and that light of two or more wavelengths can be distinguishably detected based on the values ​​of the current or voltage.

[0057] The photodetector 30 of the third embodiment can make the light L travel in a direction parallel to the surface of the substrate 31, thereby lengthening the optical path of the light L. Therefore, the photodetector 30 of the second embodiment can increase the wavelength discrimination resolution.

[0058] (4) Fourth embodiment (4-1) Configuration of the photodetector according to the fourth embodiment FIG. 13 shows a photodetector 40 according to a fourth embodiment. The photodetector 40 includes a substrate 41, a light-shielding layer 42, a charge trapping unit 43, and a measurement unit 44. The substrate 41 includes a recessed portion 420, which is a portion of the upper surface of the substrate 41 dug downward. The light-shielding layer 42 is provided in a region of the upper surface of the substrate 41 closer to the charge trapping unit 43 than the recessed portion 420. The material of the light-shielding layer 42 can be the same as that of the light-shielding layer in the first and second embodiments. The configurations of the charge trapping unit 43 and the measurement unit 44 are similar to those in the first and second embodiments. The sidewall of the recessed portion 420 closer to the charge trapping unit 43 functions as a light entrance unit 421. In this embodiment, the recessed portion 420 has a trapezoidal cross section, and the lower base of the trapezoid is shorter than the upper base (the base closer to the surface of the substrate 41). The substrate 41 and the charge trapping unit 43 can be made of p-type and n-type semiconductors similar to those of the substrate and charge trapping unit in the first and second embodiments.

[0059] (4-2) Operation of the photodetector of the fourth embodiment The operation of the photodetector 40 of the fourth embodiment will be described with reference to FIG. 14 . When using this photodetector 40, light L to be measured is irradiated from above the substrate 41 onto the side wall of the sunken portion 420, which is the light introducing portion 421, closer to the charge trapping portion 43. The light L is refracted by the side wall and enters the substrate 41. As a result, the light L travels within the substrate 41 in a direction closer to parallel to the surface of the substrate 41 than the optical path outside the substrate 41. Similar to the photodetector 10 of the first embodiment, charges C are generated as the light L travels within the substrate 41, minority carriers in the substrate 41 among the generated charges C are captured by the charge trapping portion 43 closest to the position where the charges C were generated, the movement of the charges C is detected as a current or voltage by the measuring portion 44, and light of two or more wavelengths can be distinguishably detected based on the values ​​of the current or voltage.

[0060] According to the fourth embodiment of the photodetector 40, light L can be made to travel within the substrate 41 in a direction closer to parallel to the surface of the substrate 41 than the optical path outside the substrate 41, thereby making it possible to lengthen the optical path of light L and increase the wavelength discrimination resolution.

[0061] (4-3) Modification of the photodetector according to the fourth embodiment In the example shown in Fig. 13, the shape of the vertical cross section of the sunken portion 420 is a trapezoid, but the shape of the sunken portion is not limited to this. For example, as shown in Fig. 15, a sunken portion 420A having a triangular shape in vertical cross section may be provided on the surface of the substrate 41. In this case, the hypotenuse of the triangle of the sunken portion 420A becomes the light introducing portion 421A. Note that, although the shape of the vertical cross section of the sunken portion 420A is a right triangle in Fig. 15, it may be another type of triangle.

[0062] In addition, as in the first embodiment, the upper surface of the substrate 41 and the lower surface of the charge capture section 43 may be at the same height, a light-transmitting member may be provided within the light introducing sections 421 and 421A, and further, an incident direction selection filter may be provided above the sunken sections 420 and 420A.

[0063] (5) Fifth embodiment (5-1) Configuration of the photodetector of the fifth embodiment FIG. 16 shows a photodetector 50 according to a fifth embodiment. The photodetector 50 includes a substrate 51, a light-shielding layer 52, a charge trapping unit 53, and a measurement unit 54. The substrate 51 has a sunken portion 520 formed by digging down a portion of its upper surface. The configurations (including materials) of the substrate 51, the light-shielding layer 52, the charge trapping unit 53, and the measurement unit 54 are the same as those of the fourth embodiment. The sunken portion 520 has a vertical cross section in the shape of a right triangle, with the side closer to the charge trapping unit 53 perpendicular to the surface of the substrate 51 and the side opposite the charge trapping unit 53 as the hypotenuse. The side wall of the sunken portion 520 corresponding to the side closer to the charge trapping unit 53 of the right triangle functions as a light introducing portion 521. The side wall serving as the light introducing portion 521 may be slightly inclined from the direction perpendicular to the surface of the substrate 51. A reflecting portion 522 having a light-reflecting coating is formed on the hypotenuse, which is the side of the right triangle opposite the charge trapping unit 53.

[0064] (5-2) Operation of the photodetector of the fifth embodiment The operation of the photodetector 50 of the fifth embodiment will be described with reference to FIG. 17 . When using this photodetector 50, light L to be measured is irradiated from above the substrate 51 onto the reflector 522 in the sunken portion 520. The light L irradiated onto the reflector 522 is reflected by the reflector 522 and enters the light introducing portion 521, and then enters the substrate 51 from the light introducing portion 521. As a result, the light L travels within the substrate 51 in a direction closer to parallel to the surface of the substrate 51 than the optical path outside the substrate 51. Furthermore, by adjusting the angle of the reflector 522 or the angle at which the light L is incident on the reflector 522, it is possible to make the optical path within the substrate 51 parallel to the surface of the substrate 51, as shown in FIG. 17 . In the example of FIG. 17 , the reflecting surface of the reflector 522 is inclined by 45° with respect to the surface of the substrate 51, so that the light L incident on the reflector 522 in a direction perpendicular to the surface of the substrate 51 travels within the substrate 51 in a direction parallel to the surface of the substrate 51. Depending on the angle of the reflecting portion 522, the traveling direction of the light L within the substrate 51 may be slightly inclined with respect to the surface of the substrate 51.

[0065] The photodetector 10 of the first embodiment is similar in that electric charges C are generated as light L travels within the substrate 51, that minority carriers of the generated electric charges C in the substrate 51 are captured by the charge capture section 53 closest to the position where the electric charges C are generated, that the movement of the electric charges C is detected as a current or voltage by the measurement section 54, and that light of two or more wavelengths can be distinguishably detected based on the values ​​of the current or voltage.

[0066] According to the fifth embodiment of the photodetector 50, light L can be made to travel within the substrate 51 in a direction parallel to or close to the surface of the substrate 51, thereby making it possible to lengthen the optical path of light L and increase the wavelength discrimination resolution.

[0067] (5-3) Modification of the photodetector according to the fifth embodiment FIG. 18 shows a photodetector 50A, which is a modified example of the photodetector of the fifth embodiment. This photodetector 50A has a sunken portion 520A formed by digging down a portion of the upper surface of the substrate 51. The vertical cross section of the sunken portion 520A has an inverted M shape, which is the letter M turned upside down. One reflective portion is provided on each of the two slopes of the inverted M-shaped vertical cross section. Here, one reflective portion is referred to as a first reflective portion 522A, and the other reflective portion is referred to as a second reflective portion 522B. In the inverted M-shaped vertical cross section, the side wall facing the first reflective portion 522A is the first light introducing portion 521A, and the side wall facing the second reflective portion 522B is the second light introducing portion 521B.

[0068] On the surface (upper surface) of the substrate 51, a plurality of charge trapping units 53 are arranged in two directions from the sunken portion 520A. Specifically, on the side closer to the first light introducing portion 521A than the sunken portion 520A, a plurality of charge trapping units 53 are arranged in one direction so as to move away from the sunken portion 520A, and on the side closer to the second light introducing portion 521B than the sunken portion 520A, a plurality of charge trapping units 53 are arranged in the opposite direction (a direction 180° different) from the charge trapping units 53 on the first light introducing portion 521A side so as to move away from the sunken portion 520A. On the side closer to the first light introducing portion 521A, the charge trapping unit 53 closest to the first light introducing portion 521A is arranged at a position where the distance between the center (hereinafter simply referred to as "center") of the direction in which the plurality of charge trapping units 53 are arranged and the first light introducing portion 521A is L0. On the second light introducing section 521B side, the charge trapping section 53 closest to the second light introducing section 521B is disposed at a position where the distance between its center and the second light introducing section 521B is (L0 + L1 / 2). On both the first light introducing section 521A side and the second light introducing section 521B side, the distance between the centers of adjacent charge trapping sections 53 is L1. Therefore, when the first light introducing section 521A side and the second light introducing section 521B side are combined, the photodetector 50A includes a plurality of charge trapping sections 53 whose distances from the light introducing section (first light introducing section 521A or second light introducing section 521B) differ by L1 / 2.

[0069] Similar to the embodiments described above, a light-shielding layer 52 is provided on the surfaces of the substrate 51 and the charge trapping units 53, and a measuring unit 54 is provided in each charge trapping unit 53. The materials of the substrate 51, the charge trapping units 53, and the light-shielding layer 52 are similar to those in the embodiments described above.

[0070] According to the photodetector 50A of this modification, light L to be measured is irradiated from above the substrate 51 onto the first reflecting portion 522A and the second reflecting portion 522B in the sunken portion 520A, whereby the light L is reflected by the first reflecting portion 522A or the second reflecting portion 522B. The light reflected by the first reflecting portion 522A enters the substrate 51 through the first light introducing portion 521A, and the light reflected by the second reflecting portion 522B enters the substrate 51 through the second light introducing portion 521B, and travels within the substrate 51 in a direction parallel to or close to the surface of the substrate 51. The principle by which light L is detected is the same as that of the photodetector 50 of the fifth embodiment.

[0071] In this modified photodetector 50A, as described above, by arranging multiple charge trapping sections 53 on both the first light introducing section 521A side and the second light introducing section 521B side at an interval of L1, the distance between each of the multiple charge trapping sections 53 and the light introducing section (first light introducing section 521A or second light introducing section 521B) differs by L1 / 2, thereby enabling a higher wavelength discrimination resolution than when there is only one light introducing section and multiple charge trapping sections 53 are arranged at an interval of L1.

[0072] In this modification, the distances between charge trapping section 53 and first light introducing section 521A and second light introducing section 521B, as well as the spacing between charge trapping sections 53, are shown as examples and can be changed as appropriate depending on the wavelength of light to be measured. In addition, it is not essential that the spacing between charge trapping sections 53 be equal.

[0073] For example, the distance between first light introducing section 521A and the nearest charge trapping section 53 may be equal to the distance between second light introducing section 521B and the nearest charge trapping section 53, and further the distance between adjacent charge trapping sections 53 may be equal. This allows the light reflected by first reflecting section 522A and the light reflected by second reflecting section 522B to be measured under the same conditions, and by combining them, the measurement accuracy can be increased.

[0074] The direction in which the charge trapping units 53 are arranged is not limited to one direction in each embodiment and modification other than the modification shown in FIG. 18 , or two directions in the modification shown in FIG. 18 . For example, a polygonal pyramidal convex portion, such as a triangular or square pyramid, can be erected within the sunken portion, and a reflector can be provided on each of the multiple pyramidal faces of the polygonal pyramid (three faces for a triangular pyramid, four faces for a square pyramid), and the charge trapping units can be arranged in a direction away from each pyramidal face. This allows multiple charge trapping units to be arranged in a line in three or more directions. Alternatively, a conical convex portion can be erected in the center of a cylindrical sunken portion, and a reflector can be provided on the conical face of the convex portion, and multiple circular charge trapping units can be arranged concentrically with the cylinder of the sunken portion.

[0075] Furthermore, a conical protrusion may be provided at the center of the cylindrical recess, and a reflector may be provided on the conical surface of the protrusion, and multiple charge trapping units may be arranged in a spiral. This allows each charge trapping unit to be positioned at a different distance from the sidewall of the recess. In this case, the charge trapping units do not need to be aligned in one or more directions.

[0076] (6) Sixth embodiment (6-1) Configuration of the photodetector of the sixth embodiment FIG. 19 shows a photodetector 60 according to a sixth embodiment. The photodetector 60 includes a substrate 61, a light-shielding layer 62, a charge trapping section 63, a measurement section 64, and a trapping section 65. The configurations of the substrate 61, the light-shielding layer 62, the charge trapping section 63, and the measurement section 64 are the same as those in the first embodiment. Similarly to the first embodiment, a region on the surface of the substrate 61 is provided without the light-shielding layer 62, and this region serves as a light introducing section 621. The trapping section 65 is made of the same semiconductor type as the semiconductor of the charge trapping section 63 (an n-type semiconductor in this example) and is provided between adjacent charge trapping sections 63. The trapping section 65 is also provided outside the area where the multiple charge trapping sections 63 are arranged, specifically between the charge trapping section 63 closest to the light introducing section 621 and the light introducing section 621, and on the opposite side of the charge trapping section 63 farthest from the light introducing section 621. The measurement section 64 is not connected to the trapping section 65. It is to be noted that some of the multiple trapping sections 65 shown in this example may be omitted. In addition, in order to prevent the charge C (described later) captured by the trapping section 65 from overflowing to the substrate 61 side, it is preferable to provide the trapping section 65 with a discharge means for discharging the charge (for example, a means for grounding the trapping section 65).

[0077] (6-2) Operation of the photodetector of the sixth embodiment The operation of the photodetector 60 of the sixth embodiment will be described with reference to Figure 20. As with the photodetector 10 of the first embodiment, light L to be measured is made incident on the light introducing part 621 in a direction tilted at a predetermined angle from the surface of the substrate 61, whereby the light L travels through the substrate 61 and is gradually absorbed by the semiconductor of the substrate 61. This absorption of light generates electric charges C consisting of electron-hole pairs.

[0078] In this way, the charge C generated by light absorption moves (diffuses) within the substrate 61 with a certain degree of expansion. Therefore, there is a possibility that some of the charge C will be introduced into another charge trapping unit 63 rather than into the charge trapping unit 63 (nearest neighbor charge trapping unit) that is closest to the position where light absorption occurred. If some of the charge C is introduced into such an adjacent charge trapping unit 63, it will cause a decrease in measurement accuracy. Therefore, in the photodetector 60 of the sixth embodiment, a trapping unit 65 is provided between adjacent charge trapping units 63, so that the trapping unit 65 captures the charge C that moves closer to the adjacent charge trapping unit 63 than the nearest neighbor charge trapping unit. This prevents the charge C from being introduced into charge trapping units 63 other than the nearest neighbor charge trapping unit, thereby improving the wavelength discrimination resolution.

[0079] (7) Photodetector of Seventh Embodiment (7-1) Configuration of the photodetector of the seventh embodiment FIG. 21 shows a photodetector 70 according to a seventh embodiment. This photodetector 70 includes a substrate 71, a light-shielding layer 72, a light introducing portion 721, a charge trapping portion 73, and a measurement portion 74, similar to those of the photodetector 60 according to the sixth embodiment. Instead of the trapping portion 65 of the photodetector 60 according to the sixth embodiment, the photodetector 70 includes a block portion 75 made of a semiconductor (same p-type semiconductor) of the same type as the semiconductor of the substrate 71 (a p-type semiconductor in the example shown in FIG. 21) but with a higher impurity concentration. Block portions 75 are also provided outside the area where the multiple charge trapping portions 73 are arranged, specifically between the charge trapping portion 73 closest to the light introducing portion 721 and the light introducing portion 721, and on the opposite side of the charge trapping portion 73 farthest from the light introducing portion 721. The measurement portion 74 is not connected to the block portion 75. Note that some of the multiple block portions 75 shown in this example may be omitted.

[0080] (7-2) Operation of the photodetector of the seventh embodiment The operation of the photodetector 70 of the seventh embodiment will be described with reference to Fig. 22. As with the photodetector 60 of the sixth embodiment, light L to be measured is made incident on the light introducing part 721 in a direction tilted at a predetermined angle from the surface of the substrate 71, whereby the light L travels through the substrate 71 and is gradually absorbed by the semiconductor of the substrate 71. This absorption of light generates electric charges C consisting of electron-hole pairs.

[0081] As in the sixth embodiment, the charge C generated by light absorption moves (diffuses) within the substrate 71 with a certain degree of expansion, which may result in some of the charge C being introduced into other charge trapping sections 73 rather than the nearest charge trapping section. Therefore, in the photodetector 70 of the seventh embodiment, a block section 75 is provided between adjacent charge trapping sections 73, so that a repulsive force acts on minority carriers in the substrate 71 when the minority carriers approach the block section 75. This prevents charge C from being introduced into charge trapping sections 73 other than the nearest charge trapping section, thereby improving the wavelength discrimination resolution.

[0082] Some of the plurality of trap portions 65 and block portions 75 shown in the sixth and seventh embodiments may be omitted.

[0083] (8) Example with only one charge trap In each of the embodiments and modifications described above, a plurality of charge trapping units are provided, but the photodetector according to each of the embodiments and modifications may be provided with only one charge trapping unit.

[0084] For example, a photodetector 10A shown in FIG. 23 is the photodetector 10 of the first embodiment, except that the number of charge trapping units 13 and measuring units 14 is only one each.

[0085] When using this photodetector 10A, similar to the photodetector 10 of the first embodiment, light L to be measured is incident on the light introducing section 121 in a direction tilted at a predetermined angle θ (<90°) from the surface of the substrate 11. As a result, the light L is refracted at the surface of the substrate 11 and travels through the substrate 11 at an angle tilted relative to the surface of the substrate 11. During this travel, the light L is gradually absorbed by the semiconductor of the substrate 11, thereby generating charges C consisting of electron-hole pairs. The generated charges C diffuse within the substrate 11, and minority carriers generated within a predetermined range from the charge trapping section 13 are captured by the charge trapping section 13. The measuring section 14 measures the current or voltage generated between the substrate 11 and the charge trapping section 13 as a result of the charge trapping section 13 capturing the charges.

[0086] As described in the first embodiment, the charge generated by light absorption in the semiconductor of the substrate 11 decreases with increasing distance from the light introducing section 121 and is almost nonexistent at positions a certain distance from the light introducing section 121. Therefore, the number of charges captured by the charge trapping section 13 and the current or voltage value of each charge trapping section 13 measured by the measurement section 14 decrease with increasing distance from the charge trapping section 13 closer to the light introducing section 121. This decrease is more rapid as the wavelength of the light being measured becomes shorter. Therefore, only charges generated by light with a certain long wavelength are captured by the charge trapping section 13 located a predetermined distance from the light introducing section 121. This allows only light within a wavelength range longer than a predetermined wavelength corresponding to the distance between the light introducing section 121 and the charge trapping section 13 to be detected. The distance between the light introducing section 121 and the charge trapping section 13 (the predetermined distance) can be determined by the distance between the point of the light introducing section 121 closest to the charge trapping section 13 and the point of the charge trapping section 13 closest to the light introducing section 121. Alternatively, this distance may be defined by the distance between the center of gravity of the area of ​​the light introducing portion 121 and the center of gravity of the area of ​​the charge trapping portion 13, or the like.

[0087] Although this photodetector 10A cannot distinguish between two or more wavelengths of light and detect any of them, it can distinguish and detect light within a wavelength range longer than a predetermined wavelength from light with a wavelength shorter than the predetermined wavelength. According to this photodetector 10A, charge trapping portion 13 is provided on the surface of substrate 11 regardless of the wavelength of the light to be detected, making it easy to manufacture.

[0088] The predetermined distance can be determined by conducting a preliminary experiment using light within the wavelength range to be detected and light within a shorter wavelength range, so that the former is detected and the latter is (almost) not detected. This preliminary experiment can be performed using a configuration in which multiple charge trapping units 13 are arranged in a direction away from light introducing unit 121, as shown in Figure 1, and each charge trapping unit 13 is provided with one measuring unit 14. The optimal combination of charge trapping units 13 and measuring units 14 can be selected from these multiple combinations.

[0089] As in the first embodiment, even when the charge capture section 13 is formed directly on the upper surface of the substrate 11 so that the upper surface of the substrate 11 and the lower surface of the charge capture section 13 are at the same height (see Figure 24), or when an incident direction adjustment section 16 is provided in the light introduction section 121 (see Figure 25), it is possible to provide only one charge capture section 13 and one measurement section 14.

[0090] 26, a plurality of light introducing portions (non-light-shielding portions) may be provided on the surface of substrate 11 (first light introducing portion 1211 and second light introducing portion 1212 in the example of FIG. 26), and one pair of charge trapping portion 13 may be provided corresponding to each light introducing portion. In this case, by setting the distance c between first light introducing portion 1211 and the corresponding charge trapping portion 13 and the distance d between second light introducing portion 1212 and the corresponding charge trapping portion 13 to different values, the two charge trapping portions 13 will detect light within different wavelength ranges.

[0091] Furthermore, the photodetectors according to the second to seventh embodiments may also have only one charge trapping unit. For example, as in a photodetector 20A shown in FIG. 27, only one charge trapping unit 23 may be provided on the back surface 212 of the substrate 21, which is the surface opposite to the front surface 211 on which the light-shielding layer 22 is provided (corresponding to the second embodiment). In this case, the charge trapping unit 23 can detect only light within a wavelength range longer than a predetermined wavelength, which is determined according to the distance between the charge trapping unit 23 and a region (facing region 222) facing the light introducing unit 221 on the back surface 212. This distance can be determined by the distance between the point in the facing region 222 closest to the charge trapping unit 23 and the point in the region of the charge trapping unit 23 closest to the facing region 222. Alternatively, this distance may be determined by the distance between the center of gravity of the facing region 222 and the center of gravity of the region of the charge trapping unit 23, or the like.

[0092] Furthermore, as in the photodetector 30A shown in FIG. 28, when the side portion of the substrate 31 serves as the light introducing portion 321, only one charge trapping portion 33 may be provided (corresponding to the third embodiment).

[0093] Alternatively, as in a photodetector 40A shown in Fig. 29, a sunken portion 420 dug downward may be provided in a portion of the upper surface of a substrate 41, and only one charge trapping portion 43 may be provided, with the side wall of the sunken portion 420 closer to the charge trapping portion 43 serving as the light introducing portion 421 (corresponding to the fourth embodiment). The shape of the sunken portion is not limited to the example shown in Fig. 29. For example, as shown in Fig. 30, a sunken portion 420A having a triangular cross section may be used, with the hypotenuse of the triangle of the sunken portion 420A serving as the light introducing portion 421A.

[0094] 31, in an example in which a reflector 522 having a reflecting surface inclined at 45° with respect to the surface of the substrate 51 is provided in the sunken portion 520, only one charge trapping portion 53 may be provided on the surface of the substrate 51 facing the reflecting surface (corresponding to the fifth embodiment). In this way, light L incident on the reflector 522 in a direction perpendicular to the surface of the substrate 51 can be reflected by the reflector 522, and the light can travel within the substrate 51 in a direction parallel to the surface of the substrate 51. Alternatively, as shown in FIG. 32, one reflecting portion (first reflecting portion 522A and second reflecting portion 522B) may be provided on each of two slopes of the sunken portion 520A, which has an M-shaped cross section, and one charge trapping portion 53 may be provided on each side of this inverted M-shape.

[0095] 33 (corresponding to the sixth embodiment) using a trapping section 65, and a photodetector 70A (corresponding to the seventh embodiment) using a block section 75 shown in FIG. 34, it is also possible to provide only one charge trapping section 63, 73. In these cases, the trapping section 65 and / or the block section 75 are provided closer to the light introducing sections 621, 721 than the charge trapping sections 63, 73 or on the opposite side of the light introducing sections 621, 721 from the charge trapping sections 63, 73.

[0096] The present invention is not limited to the above-described embodiments and modifications, and the configurations of the embodiments and modifications can be appropriately combined, or further modifications can be made. [Explanation of symbols]

[0097] 10, 10A, 20, 20A, 30, 30A, 40, 40A, 50, 50A, 50B, 50C, 60, 60A, 70, 70A...Photodetector 11, 21, 31, 41, 51, 61, 71... PCB 211...One surface of the substrate 212...the other surface (back surface) of the substrate 12, 22, 32, 42, 52, 62, 72...light shielding layer 121, 221, 321, 421, 421A, 521, 621, 721...Light introduction part (non-shading part) 13, 23, 33, 43, 53, 63, 73...Charge trap section 14, 24, 34, 44, 54, 64, 74...Measuring part 15...Translucent member 16...Incidence direction adjustment section 420, 420A, 520, 520A…Sinking part 1211, 521A, 6211...1st light introduction section 1212, 521B, 6212...Second light introduction section 222…Opposing area 522...Reflector 522A…1st reflection section 522B…Second reflection section 65...Trap section 75...Block section

Claims

1. a) a substrate made of a p-type semiconductor or an n-type semiconductor; b) a light-shielding layer covering a part or all of one surface of the substrate; c) a light introducing portion provided on one surface of the substrate at a position other than the area covered with the light-shielding layer or on a side surface of the substrate; d) at least two charge trapping sections made of a semiconductor of the opposite type to that of the substrate, the charge trapping sections being provided on one surface of the substrate at different distances from the light introducing section; e) a measuring unit electrically connected to the charge trapping unit; Equipped with The entire charge trapping portion is located below the light-shielding layer and spaced apart from the light introducing portion. A photodetector device characterized by:

2. a) a substrate made of a p-type semiconductor or an n-type semiconductor; b) a light-shielding layer covering a part or all of one surface of the substrate; c) a light introducing portion provided on one surface of the substrate at a position other than the area covered with the light-shielding layer or on a side surface of the substrate; d) at least two charge trapping sections made of a semiconductor of the opposite type to that of the substrate, the charge trapping sections being provided on the other surface of the substrate at different distances from the light introducing section; e) a measuring unit electrically connected to the charge trapping unit; Equipped with The entire charge trapping portion is located below the light-shielding layer and spaced apart from the light introducing portion. A photodetector device characterized by:

3. 3. The photodetector according to claim 1, wherein the charge trapping portions are arranged side by side in at least one direction.

4. a) a substrate made of a p-type semiconductor or an n-type semiconductor; b) a light-shielding layer covering a portion of one surface of the substrate; c) a light introducing portion provided in a non-light-shielding portion that is a position other than the area covered with the light-shielding layer on one surface of the substrate, the light introducing portion having a sunken portion where a part of the substrate is sunken from the surface; d) at least two charge trapping sections made of a semiconductor of the opposite type to that of the substrate, the charge trapping sections being provided on one surface or the other surface of the substrate at different distances from the light introducing section; e) a measuring unit electrically connected to the charge trapping unit; Equipped with The entire charge trapping portion is located below the light-shielding layer and spaced apart from the light introducing portion. A photodetector device characterized by:

5. 5. The light detection device according to claim 4, further comprising a reflector within the recess.

6. 4. The photodetector according to claim 1, wherein one surface of the substrate is entirely covered with the light-shielding layer.

7. a) a substrate made of a p-type semiconductor or an n-type semiconductor; b) a light-shielding layer covering a part or all of one surface of the substrate; c) a light introducing section provided at a position on one surface of the substrate other than the area covered with the light-shielding layer or on a side surface of the substrate, the light introducing section including an incident direction selecting filter that selectively passes light incident on the substrate from directions within a predetermined range; d) at least two charge trapping sections made of a semiconductor of the opposite type to that of the substrate, the charge trapping sections being provided on one surface or the other surface of the substrate at different distances from the light introducing section; e) a measuring unit electrically connected to the charge trapping unit; Equipped with The entire charge trapping portion is located below the light-shielding layer and spaced apart from the light introducing portion. A photodetector device characterized by:

8. a) a substrate made of a p-type semiconductor or an n-type semiconductor; b) a light-shielding layer covering a part or all of one surface of the substrate; c) a light introducing portion provided on one surface of the substrate at a position other than the area covered with the light-shielding layer or on a side surface of the substrate; d) a charge trapping portion formed on one surface or the other surface of the substrate and made of a semiconductor of the opposite type to that of the substrate; e) a trap section made of the same type of semiconductor as that of the charge trap section, the trap section being provided between the charge trap section and the light introducing section and / or on the opposite side of the light introducing section as viewed from the charge trap section; f) a measuring unit electrically connected to the charge trapping unit; Equipped with The charge trapping portion is entirely located below the light-shielding layer and spaced apart from the light introducing portion. A photodetector device characterized by:

9. a) a substrate made of a p-type semiconductor or an n-type semiconductor; b) a light-shielding layer covering a part or all of one surface of the substrate; c) a light introducing portion provided on one surface of the substrate at a position other than the area covered with the light-shielding layer or on a side surface of the substrate; d) a charge trapping portion formed on one surface or the other surface of the substrate and made of a semiconductor of the opposite type to that of the substrate; e) a block portion made of a semiconductor of the same type as the semiconductor of the substrate but with a higher impurity concentration than the semiconductor of the substrate, the block portion being provided between the charge trap portion and the light entrance portion and / or on the opposite side of the light entrance portion as viewed from the charge trap portion; f) a measuring unit electrically connected to the charge trapping unit; Equipped with The charge trapping portion is entirely located below the light-shielding layer and spaced apart from the light introducing portion. A photodetector device characterized by:

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