Photodetector, photodetection system, lidar device and moving object

Abstract

To provide a light detector, a light detection system, a lidar device, and a mobile body in which responsivity can be improved.SOLUTION: According to an embodiment, a light detector includes a semiconductor layer of a first conductivity type, and a light-receiving element. The light-receiving element includes a first semiconductor region, a second semiconductor region, a third semiconductor region, and a fourth semiconductor region. The first semiconductor region is of a second conductivity type. The second semiconductor region is provided between the first semiconductor region and the semiconductor layer. The second semiconductor region is in contact with the first semiconductor region. The second semiconductor region is of the first conductivity type. The third semiconductor region is provided between the second semiconductor region and the semiconductor layer. The third semiconductor region is of the second conductivity type. The fourth semiconductor region is provided between the third semiconductor region and the semiconductor layer. The fourth semiconductor region is of the first conductivity type. The fourth semiconductor region has lower first-conductivity-type impurity concentration than first-conductivity-type impurity concentration of the semiconductor layer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] Embodiments of the present invention relate to a photodetector, a photodetection system, a lidar device, and a moving object. [Background technology]

[0002] There are photodetectors that detect light incident on a semiconductor region, and there is a demand for improved response of the photodetectors. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-114728 Summary of the Invention [Problem to be solved by the invention]

[0004] Embodiments of the present invention provide a photodetector, a photodetection system, a lidar device, and a moving object that can improve response. [Means for solving the problem]

[0005] According to an embodiment of the present invention, there is provided a photodetector including a semiconductor layer and a light-receiving element. The semiconductor layer is of a first conductivity type. The light-receiving element includes a first semiconductor region, a second semiconductor region, a third semiconductor region, and a fourth semiconductor region. The first semiconductor region is of a second conductivity type. The second semiconductor region is provided between the first semiconductor region and the semiconductor layer. The second semiconductor region is in contact with the first semiconductor region. The second semiconductor region is of the first conductivity type. The third semiconductor region is provided between the second semiconductor region and the semiconductor layer. The third semiconductor region is of the second conductivity type. The fourth semiconductor region is provided between the third semiconductor region and the semiconductor layer. The fourth semiconductor region is of the first conductivity type. The impurity concentration of the first conductivity type in the fourth semiconductor region is lower than the impurity concentration of the first conductivity type in the semiconductor layer. [Brief explanation of the drawings]

[0006] [Figure 1] 1 is a schematic cross-sectional view illustrating a photodetector according to an embodiment. [Figure 2] 5 is a schematic graph illustrating the distribution of impurity concentrations in the photodetector according to the embodiment. FIG. [Figure 3] 1 is a schematic cross-sectional view illustrating a photodetector according to an embodiment. [Figure 4] 5 is a schematic graph illustrating the distribution of impurity concentrations in the photodetector according to the embodiment. FIG. [Figure 5] 1 is a schematic cross-sectional view illustrating a photodetector according to an embodiment. [Figure 6] 5 is a schematic graph illustrating the distribution of impurity concentrations in the photodetector according to the embodiment. FIG. [Figure 7] 1 is a schematic cross-sectional view illustrating a photodetector according to an embodiment. [Figure 8] 5 is a schematic graph illustrating the distribution of impurity concentrations in the photodetector according to the embodiment. FIG. [Figure 9] FIG. 10 is a schematic plan view illustrating another photodetector according to the embodiment. [Figure 10] FIG. 2 is a schematic plan view illustrating a part of a photodetector according to the embodiment. [Figure 11] FIG. 2 is a schematic cross-sectional view illustrating a part of a photodetector according to the embodiment. [Figure 12] FIG. 1 is a schematic diagram illustrating an active quench circuit. [Figure 13] FIG. 1 is a schematic diagram illustrating a LIDAR device according to an embodiment. [Figure 14] FIG. 10 is a diagram for explaining detection of a detection target by a LIDAR device. [Figure 15] 1 is a schematic top view of a moving body equipped with a lidar device according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0007] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The drawings are schematic or conceptual, and the relationship between the thickness and width of each part, the size ratio between parts, etc. are not necessarily the same as those in reality. Even when the same part is shown, the dimensions and ratios may be different depending on the drawing. In this specification and in each drawing, elements similar to those previously described with reference to the previous drawings are designated by the same reference numerals, and detailed descriptions thereof will be omitted where appropriate. In the embodiment, the first conductivity type is one of p-type and n-type. The second conductivity type is the other of p-type and n-type. In the following, a case where the first conductivity type is p-type and the second conductivity type is n-type will be described.

[0008] FIG. 1 is a schematic cross-sectional view illustrating a photodetector according to an embodiment. 1, a photodetector 101 according to the embodiment includes a light receiving element 10 (element region) and a semiconductor layer 21 (first semiconductor layer). In this example, the photodetector 101 further includes an insulating layer 30, a light collecting portion 40, an electrode 50, and a structural portion 70. The light receiving element 10 is provided on the semiconductor layer 21.

[0009] In the description of the embodiment, the direction from the semiconductor layer 21 toward the light receiving element 10 is referred to as the Z-axis direction (first direction). The direction perpendicular to the Z-axis direction is referred to as the X-axis direction (second direction). The X-axis direction is parallel to the surface of the semiconductor layer 22. The direction perpendicular to the Z-axis direction and the X-axis direction is referred to as the Y-axis direction (third direction). For the sake of explanation, the direction from the semiconductor layer 21 toward the light receiving element 10 is referred to as "up" and the opposite direction is referred to as "down". These directions are based on the relative positional relationship between the semiconductor layer 21 and the light receiving element 10 and are unrelated to the direction of gravity. "Up" corresponds to the side where the light collecting unit 40 is installed and where light is incident on the photodetector.

[0010] The electrode 50 is, for example, a back surface electrode. The semiconductor layer 21 is provided on the electrode 50 and is electrically connected to the electrode 50. The semiconductor layer 21 is, for example, a semiconductor substrate of a first conductivity type. The semiconductor region 14 is provided on the semiconductor layer 21. The semiconductor region 14 is, for example, a part of an epitaxially grown layer of the first conductivity type. The semiconductor region 15 is provided on the semiconductor region 14. The semiconductor region 15 is, for example, a part of an epitaxially grown layer of the first conductivity type.

[0011] The light receiving element 10 includes a first semiconductor region 11, a second semiconductor region 12, a third semiconductor region 13, and a fourth semiconductor region 14. The first semiconductor region 11 is of a second conductivity type. The first semiconductor region 11 is electrically connected to a first wiring 51 (described later) via a contact 64 and a connection wiring 65. The first wiring 51 is electrically connected to a pad 55 (described later). The pad 55 is electrically connected to an external electronic device via a bonding wire or the like.

[0012] The second semiconductor region 12 is provided between the first semiconductor region 11 and the semiconductor layer 21. The second semiconductor region 12 is of the first conductivity type. The second semiconductor region 12 is in contact with the first semiconductor region 11.

[0013] The third semiconductor region 13 is provided between the second semiconductor region 12 and the semiconductor layer 21. The third semiconductor region 13 is of the second conductivity type.

[0014] At least a portion of the fourth semiconductor region 14 is provided between the third semiconductor region 13 and the semiconductor layer 21. The fourth semiconductor region 14 is of the first conductivity type. The fourth semiconductor region 14 is in contact with the semiconductor layer 21. In this example, the fourth semiconductor region 14 is in contact with the third semiconductor region 13. The fourth semiconductor region 14 does not have to be in contact with the third semiconductor region 13.

[0015] In this example, the light receiving element 10 further includes a fifth semiconductor region 15. At least a portion of the fifth semiconductor region 15 is provided between the second semiconductor region 12 and the third semiconductor region 13. The fifth semiconductor region 15 is of the first conductivity type. The fifth semiconductor region 15 contacts each of the second semiconductor region 12 and the third semiconductor region 13. The fifth semiconductor region 15 is electrically connected to each of the second semiconductor region 12 and the third semiconductor region 13.

[0016] The first semiconductor region 11 of the second conductivity type is electrically connected to a pad 55 (described later) via a first wiring 51 (described later). The third semiconductor region 13 of the second conductivity type and the semiconductor regions 12, 14, and 15 of the first conductivity type are electrically connected to an electrode 50 via a semiconductor layer 21.

[0017] The first to fifth semiconductor regions 11 to 15 are regions provided in, for example, one semiconductor layer 22 (second semiconductor layer). The semiconductor layer 22 is provided on a semiconductor layer 21 (for example, a substrate). The semiconductor layer 22 is in contact with the semiconductor layer 21 and is electrically connected to the semiconductor layer 21. For example, the light receiving element 10 (first semiconductor region 11, second semiconductor region 12, third semiconductor region 13) is provided in the semiconductor layer 22 in which the fourth semiconductor region 14 and the fifth semiconductor region 15 are provided.

[0018] The first semiconductor region 11 and the second semiconductor region 12 (and parts of the third to fifth semiconductor regions 13 to 15) form a photodiode (pixel). The photodiode (light receiving element 10) has a light receiving surface 10f. The light receiving surface 10f is the upper surface of the first semiconductor region 11.

[0019] The structure 70 is aligned with the light receiving element 10 in a direction intersecting the Z-axis direction. The structure 70 is, for example, a structural element disposed inside a trench provided in the semiconductor layer 22. The structure 70 surrounds the light receiving element 10. The planar shape of the structure 70 (the shape in the XY plane perpendicular to the Z-axis direction) is, for example, annular.

[0020] The structural portion 70 contains a material different from that of each region (each of the first to fifth semiconductor regions 11 to 15) of the semiconductor layer 22. The refractive index of the structural portion 70 is different from that of each region of the semiconductor layer 22. The refractive index of the structural portion 70 is different from that of the light receiving element 10. The structural portion 70 is insulating. At least a portion of the inside of the trench (structural portion 70) may be hollow.

[0021] For example, the depth of the structural portion 70 (trench) is deeper than the third semiconductor region 13. In other words, the position in the Z-axis direction of the lower end of the structural portion 70 is between the position in the Z-axis direction of the lower end of the third semiconductor region 13 and the position in the Z-axis direction of the semiconductor layer 21 (or electrode 50). The annular structural portion 70 surrounds the third semiconductor region 13. The length along the Z-axis direction of the structural portion 70 (trench depth) is, for example, not less than 5 μm and not more than 10 μm. The thickness of the semiconductor layer 22 is, for example, not less than 3 μm and not more than 30 μm.

[0022] 1, the fourth semiconductor region 14 has a portion 14a, a portion 14b, and a portion 14c. The portion 14a is a portion provided between the third semiconductor region 13 and the semiconductor layer 21 in the Z-axis direction. Portion 14b is a portion provided between the third semiconductor region 13 and the structural portion 70 in the X-axis direction (and in the direction within the XY plane). Portion 14b contacts both the structural portion 70 and the third semiconductor region 13. Portion 14b surrounds the third semiconductor region 13, for example, inside the annular structural portion 70. Portion 14b may be omitted. That is, the third semiconductor region 13 may contact the structural portion 70. Portion 14c is provided outside structural portion 70 and is in contact with structural portion 70. Portion 14c surrounds structural portion 70. In other words, structural portion 70 is provided between portion 14c and portion 14b, and between portion 14c and portion 14a.

[0023] The lower end of the structural portion 70 contacts, for example, the fourth semiconductor region 14. An inner portion 14a of the structural portion 70 is continuous with an outer portion 14c of the structural portion 70 via a portion of the semiconductor layer 22 below the structural portion 70.

[0024] 1, the fifth semiconductor region 15 includes a portion 15a, a portion 15b, a portion 15c, and a portion 15d. The portion 15a is provided between the second semiconductor region 12 and the third semiconductor region 13. Portion 15b is a portion provided between the first semiconductor region 11 and the structural portion 70, and between the second semiconductor region 12 and the structural portion 70. Portion 15b contacts each of the first semiconductor region 11, the second semiconductor region 12, and the structural portion 70. Portion 15b surrounds the first semiconductor region 11 and the second semiconductor region 12, for example, inside the annular structural portion 70. The portion 15c is provided between the third semiconductor region 13 and the structure 70. The portion 15c contacts both the third semiconductor region 13 and the structure 70. The portion 15c surrounds the third semiconductor region 13, for example, inside the annular structure 70. Portion 15d is provided outside structural portion 70 and is in contact with structural portion 70. Portion 15d surrounds structural portion 70. In other words, structural portion 70 is provided between portion 15d and portion 15b, and between portion 15d and portion 15c. Outer portion 15d of structural portion 70 is separated by structural portion 70 from inner portions 15a, 15b, and 15c of structural portion 70, and may be separated from inner portions 15a, 15b, and 15c of structural portion 70. The portions 15b and 15c may be omitted. That is, the first semiconductor region 11, the second semiconductor region 12, and the third semiconductor region 13 may each be in contact with the structure .

[0025] In this example, the fifth semiconductor region 15 is in contact with the fourth semiconductor region 14. Specifically, the portion 14b is in contact with the portion 15c, and the portion 14c is in contact with the portion 15d.

[0026] For example, the planar shape of the third semiconductor region 13 may be wider than the planar shape of the first semiconductor region 11, and may be wider than the planar shape of the second semiconductor region 12. For example, the length of the third semiconductor region 13 along the X-axis direction may be longer than the length of the first semiconductor region 11 along the X-axis direction, and may be longer than the length of the second semiconductor region 12 along the X-axis direction. However, the present invention is not limited to this, and the planar shape of the third semiconductor region 13 may be narrower than the planar shape of the first semiconductor region 11 and narrower than the planar shape of the second semiconductor region 12. For example, the length of the third semiconductor region 13 along the X-axis direction may be equal to or less than the length of the first semiconductor region 11 along the X-axis direction and may be equal to or less than the length of the second semiconductor region 12 along the X-axis direction.

[0027] For example, in the XY plane, the third semiconductor region 13 is provided in the center of the light receiving element 10. For example, in the XY plane, the central position of the third semiconductor region 13 may coincide with at least one of the central position of the first semiconductor region 11, the central position of the second semiconductor region 12, and the central position of the annular structure 70.

[0028] The insulating layer 30 is provided on the semiconductor layer 22 and is in contact with, for example, the upper surface of the semiconductor layer 22. The light-collecting portion 40 is provided on the insulating layer 30 and is in contact with, for example, the upper surface of the insulating layer 30. The light-collecting portion 40 is an upwardly convex lens (for example, a microlens). The light-collecting portion 40 is capable of collecting incident light. In other words, the light-collecting portion 40 refracts at least a portion of the incident light and causes it to travel toward the light-receiving element 10.

[0029] The incident light is, for example, near-infrared light. The wavelength of near-infrared light is, for example, 0.7 micrometers (μm) or more and 2.5 μm or less. However, in the embodiment, the incident light does not necessarily have to be near-infrared light.

[0030] FIG. 2 is a schematic graph illustrating the distribution of impurity concentrations in the photodetector according to the embodiment. 2 shows the impurity concentration (the impurity concentration along the dashed line L1 shown in FIG. 1) at the center of the light receiving element 10 of the photodetector 101. The vertical axis of FIG. 2 represents the impurity concentration C (atoms per cubic centimeter (atoms / cm 3 )), and the horizontal axis in Figure 2 represents the position Pz (μm) in the Z-axis direction. The position where the value on the horizontal axis is zero is the position of the light-receiving surface 10f, and as the value on the horizontal axis increases, it moves downward. In Figure 2, the impurity concentration of the first conductivity type is represented by a solid line, and the impurity concentration of the second conductivity type is represented by a dotted line.

[0031] 2, the impurity concentration of the first conductivity type in the fourth semiconductor region 14 is lower than the impurity concentration of the first conductivity type in the semiconductor layer 21. The impurity concentration of the first conductivity type in the fourth semiconductor region 14 increases, for example, monotonically, as it approaches the semiconductor layer 21 from the fifth semiconductor region 15. The fourth semiconductor region 14 is, for example, a concentration transition region.

[0032] The impurity concentration of the first conductivity type in the fifth semiconductor region 15 is lower than the impurity concentration of the first conductivity type in the second semiconductor region 12, and is lower than the impurity concentration of the first conductivity type in the fourth semiconductor region 14. The impurity concentration of the first conductivity type in the light receiving element 10 is minimal in the fifth semiconductor region 15. That is, the fifth semiconductor region 15 is a region in the range from the second semiconductor region 12 to the semiconductor layer 21 along the Z-axis direction where the impurity concentration of the first conductivity type is minimal (for example, minimum).

[0033] For example, the distribution of the impurity concentration of the first conductivity type in the second semiconductor region 12 has a peak. That is, in this example, the maximum value of the impurity concentration of the first conductivity type in the second semiconductor region 12 (maximum impurity concentration C12) is a local maximum value between the upper end 12u of the second semiconductor region 12 and the lower end 12d of the second semiconductor region 12.

[0034] The impurity concentration of the first conductivity type in the semiconductor layer 21 is, for example, 1.0×10 18 (atoms / cm 3 ) or more than 1.0 × 10 19 (atoms / cm 3 ) is as follows. The impurity concentration of the first conductivity type in the second semiconductor region 12 is, for example, 1.0×10 16 (atoms / cm 3 ) or more than 1.0 × 10 18 (atoms / cm 3 ) is as follows. The impurity concentration of the first conductivity type in the fifth semiconductor region 15 is, for example, 1.0×10 13 (atoms / cm 3 ) or more than 1.0 × 1016 (atoms / cm 3 ) is as follows.

[0035] The concentration of the second conductivity type impurities in the third semiconductor region 13 is lower than the concentration of the second conductivity type impurities in the first semiconductor region 11.

[0036] The impurity concentration of the second conductivity type in the first semiconductor region 11 is, for example, 1.0×10 18 (atoms / cm 3 ) or more than 1.0 × 10 21 (atoms / cm 3 ) is as follows. The impurity concentration of the second conductivity type in the third semiconductor region 13 is, for example, 1.0×10 13 (atoms / cm 3 ) or more than 1.0 × 10 16 (atoms / cm 3 ) is as follows.

[0037] 2, for example, the concentration Cx is higher than the concentration Cp. The concentration Cx is the impurity concentration of the first conductivity type at the boundary between the third semiconductor region 13 and the fourth semiconductor region 14. The concentration Cp is the impurity concentration of the first conductivity type in the fifth semiconductor region 15. The concentration Cp is, for example, the minimum value (e.g., the smallest value) of the impurity concentration of the first conductivity type in the light receiving element 10.

[0038] The impurity concentration at the boundary between the n-type region and the p-type region is the impurity concentration at the position (depth) between the n-type region and the p-type region where the n-type impurity concentration and the p-type impurity concentration are the same. In other words, the n-type impurity concentration and the p-type impurity concentration are the same at the boundary between the n-type region and the p-type region.

[0039] 2, for example, the concentration Cy is higher than the concentration Cx. The concentration Cy is the impurity concentration of the first conductivity type at the boundary between the first semiconductor region 11 and the second semiconductor region 12.

[0040] For example, the distribution of the impurity concentration of the second conductivity type in the third semiconductor region 13 has a peak. That is, in this example, the maximum value of the impurity concentration of the second conductivity type in the third semiconductor region 13 (maximum impurity concentration C13) is a local maximum value between the upper end 13u of the third semiconductor region 13 and the lower end 13d of the third semiconductor region 13. As shown in FIG. 2, for example, the maximum impurity concentration C13 is lower than the maximum impurity concentration C12.

[0041] The impurity concentration in each semiconductor region and semiconductor layer is measured by, for example, SIMS (Secondary Ion Mass Spectrometry).

[0042] In this example, the thickness T13 (length along the Z-axis direction) of the third semiconductor region 13 is thinner than the thickness T12 of the second semiconductor region 12. For example, the thickness T15a (thickness of the portion 15a) of the fifth semiconductor region 15 is thinner than the thickness T13 of the third semiconductor region 13. For example, the thickness T14 of the fourth semiconductor region 14 is thicker than the thickness T12 of the second semiconductor region 12.

[0043] The thickness T12 is, for example, 1 μm or more and 4 μm or less. The thickness T13 is, for example, 0.5 μm or more and 4 μm or less. The thickness T14 is, for example, 1 μm or more and 7 μm or less. The thickness T15a is, for example, 0 μm or more and 8 μm or less.

[0044] The materials of the components of the photodetector 101 will now be described. The semiconductor layer 21 and the semiconductor layer 22 (first semiconductor region 11, second semiconductor region 12, third semiconductor region 13, fourth semiconductor region 14, and fifth semiconductor region 15) contain at least one semiconductor material selected from the group consisting of silicon, silicon carbide, gallium arsenide, and gallium nitride. For example, the semiconductor layer 21 and the semiconductor layer 22 contain silicon. Each of the first semiconductor region 11 and the third semiconductor region 13 is obtained by implanting, for example, phosphorus, arsenic, or antimony into silicon as an n-type impurity. The second semiconductor region 12 is obtained by implanting, for example, boron into silicon as a p-type impurity. The semiconductor layer 22 is, for example, an epitaxial layer formed on a substrate (semiconductor layer 21). For example, the first semiconductor region 11, the second semiconductor region 12, and the third semiconductor region 13 can be formed by ion implantation in an epitaxial layer including a fourth semiconductor region 14 and a fifth semiconductor region 15 formed by epitaxial growth on the semiconductor layer 21. For example, the third semiconductor region 13 is formed by implanting impurities of the second conductivity type so as to overlap the fourth semiconductor region 14, where the concentration of the impurities of the first conductivity type transitions. For example, a region of the epitaxial layer into which impurities are not ion-implanted can be the fifth semiconductor region 15. The structure 70 includes a material different from the material of the semiconductor layer 22 (light receiving element 10). Specifically, the structure 70 includes an insulating material. For example, the structure 70 includes one selected from the group consisting of oxygen and nitrogen, and silicon. For example, the structure 70 includes silicon oxide or silicon nitride. The structure 70 may have a stacked structure. A light-transmitting material is used for the light-collecting portion 40. For example, the light-collecting portion 40 includes a light-transmitting resin such as an acrylic resin. The insulating layer 30 is made of, for example, an optically transparent material. For example, the insulating layer 30 includes silicon and one selected from the group consisting of oxygen and nitrogen. For example, the insulating layer 30 includes at least one of silicon oxide and silicon nitride. The electrode 50 contains at least one metal selected from the group consisting of titanium, tungsten, copper, gold, aluminum, indium, and tin, for example. The same applies to the conductive portion 61, pad 55, and each wiring, which will be described later.

[0045] The operation of the photodetector 101 will now be described. Incident light incident on the upper surface of the light-collecting portion 40 from above is collected by the light-collecting portion 40 toward the light-receiving element 10. The incident light incident on the upper surface of the light-collecting portion 40 passes through the light-collecting portion 40 and the insulating layer 30, and enters the light-receiving element 10 from the light-receiving surface 10f.

[0046] For example, the light receiving element 10 functions as a PiN diode or an avalanche photodiode. When light is incident on the light receiving element 10, an electric charge is generated in the semiconductor layer 22. When the electric charge is generated, a current flows through wiring electrically connected to the first semiconductor region (for example, a conductive portion 61, a quench portion 63, and a first wiring 51, which will be described later). By detecting the current flowing through the wiring as an output, the incidence of light on the light receiving element 10 can be detected.

[0047] The conductive portion 61 and the electrode 50 apply voltages to the first to fifth semiconductor regions 11 to 15 to drive the light-receiving element. A voltage can be applied to the light-receiving element 10 by controlling the potentials of the pad 55 and the electrode 50, respectively. For example, by controlling the potential of the electrode 50, a voltage can be applied between the first semiconductor region 11 and the second semiconductor region 12, between the third semiconductor region 13 and the second semiconductor region 12 (or the fifth semiconductor region 15), and between the third semiconductor region 13 and the fourth semiconductor region 14. For example, a negative voltage is applied to the electrode 50 with respect to the pad 55. This applies a reverse voltage between the first semiconductor region 11 and the fourth semiconductor region 14. A reverse voltage exceeding the breakdown voltage may be applied to the light-receiving element 10 (between the first semiconductor region 11 and the fourth semiconductor region 14). That is, the light-receiving element 10 may include an avalanche photodiode operating in Geiger mode. By operating in Geiger mode, a pulsed signal is output with a high multiplication factor (i.e., high gain), which improves the light-receiving sensitivity of the photodetector.

[0048] For example, a high electric field region is formed in the vicinity of the pn junction formed by the first semiconductor region 11 and the second semiconductor region 12 of the photodetector 10, forming a multiplication region where avalanche amplification of carriers occurs. For example, if there are few crystal defects in the semiconductor layer 22, the charges generated in the photodetector 10 move to the multiplication region by drift or diffusion, where they are amplified and detected.

[0049] A depletion layer is formed by a pn junction in the light receiving element 10. For example, by applying a reverse voltage to the light receiving element 10 by the conductive portion 61 and the electrode 50, the width of the depletion layer in the vertical direction increases.

[0050] For example, within the light-receiving element 10, the electric field strength outside the depletion layer is lower than the electric field strength within the depletion layer. The movement speed of charges generated within the light-receiving element 10 is considered to be slower outside the depletion layer than within the depletion layer. Therefore, for example, the time it takes for charges generated outside the depletion layer to move to the first semiconductor region 11 (the multiplication region) and be detected may be longer than the time it takes for charges generated within the depletion layer to move to the first semiconductor region 11 (the multiplication region) and be detected. That is, the time it takes for charges to be detected as a current may vary depending on the location where the charges are generated. When charges are generated outside the depletion layer, the time it takes for the charges to be detected is long, and a delayed component may be generated in the detected current value. For example, there is a risk of variation in the time from when a photon is incident on the light-receiving element to when it is detected as a current. For example, when a photodetector is used in a time-of-flight LIDAR device (described later), variations in detection time (jitter) may affect the ranging accuracy.

[0051] The depletion layer spreads from the pn junction surface between the first semiconductor region 11 and the second semiconductor region 12 toward the fourth semiconductor region 14. As described above, the concentration of impurities of the first conductivity type in the fourth semiconductor region 14 is relatively high. Therefore, the depletion layer does not spread easily within the fourth semiconductor region 14. It may take a relatively long time for the charges generated in the fourth semiconductor region 14 to be detected as a current.

[0052] In contrast, in the embodiment, a third semiconductor region 13 is provided in addition to the pn junction between the first semiconductor region 11 and the second semiconductor region 12. This can improve the responsiveness of the detector. For example, the depletion layer can be extended further toward the fourth semiconductor region 14. That is, the bottom end of the depletion layer can be positioned further downward. For example, the depletion layer can be made to spread more easily within the fourth semiconductor region 14. For example, charges generated within the depletion layer drift due to the electric field of the depletion layer and can move toward the first semiconductor region 11 (the multiplication region) in a short travel time. For example, it can suppress variations in the time it takes for charges generated within the light receiving element 10 to be detected as a current.

[0053] In this example, the third semiconductor region 13 contacts the fourth semiconductor region 14. This allows, for example, a depletion layer to be formed further downward in the fourth semiconductor region 14. In other words, the depletion layer in the fourth semiconductor region 14 can be extended.

[0054] A fifth semiconductor region 15, in which the concentration of first conductivity type impurities is minimal, is provided between the second semiconductor region 12 and the third semiconductor region 13. The fifth semiconductor region 15 has a relatively low impurity concentration and is therefore easily depleted. This allows, for example, the depletion layer in the light receiving element 10 to be widened in the vertical direction.

[0055] For example, the impurity concentration of the second conductivity type at the lower end 13d of the third semiconductor region 13 (same as concentration Cx in the example of FIG. 2) is higher than the impurity concentration of the second conductivity type (same as concentration Cp in the example of FIG. 2) at the upper end 13u of the third semiconductor region 13. By increasing the impurity concentration of the second conductivity type at a deeper position, for example, the depletion layer in the fourth semiconductor region 14 can be extended further downward.

[0056] 2, the impurity concentration Cy of the first conductivity type at the boundary between the first semiconductor region 11 and the second semiconductor region 12 is higher than the impurity concentration Cx of the first conductivity type at the boundary between the third semiconductor region 13 and the fourth semiconductor region 14. As a result, for example, a depletion layer spreads from the pn junction surface between the first semiconductor region 11 and the second semiconductor region 12 toward the fourth semiconductor region 14. For example, the electric field near the pn junction surface between the first semiconductor region 11 and the second semiconductor region 12 becomes stronger, and charges generated in the light receiving element 10 tend to move toward the first semiconductor region 11.

[0057] For example, the maximum value of the second conductivity type impurity concentration (concentration C13) in the third semiconductor region 13 is lower than the maximum value of the first conductivity type impurity concentration (concentration C12) in the second semiconductor region 12. This makes it easier to make the concentration Cy higher than the concentration Cx, for example.

[0058] 1, the lower end Dd of the depletion layer D formed during operation of the light receiving element 10 is located within the fourth semiconductor region 14. The upper end Du of the depletion layer D formed during operation of the light receiving element 10 is located within the first semiconductor region 11. In this manner, the depletion layer extends continuously, for example, from the first semiconductor region 11 to the fourth semiconductor region 14. The wide depletion layer can shorten the time it takes for charges generated within the light receiving element 10 to be detected as a current, for example.

[0059] The term "operation of the light-receiving element" refers to the time when the light-receiving element detects light in a product including a photodetector. For example, when the light-receiving element 10 is in operation, a predetermined voltage is applied between the electrodes (between the conductive portion 61 and the electrode 50), thereby applying a voltage between the first semiconductor region 11 and the fourth semiconductor region 14. If the light-receiving element 10 is an avalanche photodiode, the potential difference (absolute value) between the electrodes is set to a value greater than the breakdown voltage. This potential difference may be, for example, approximately 5 V greater than the breakdown voltage. When the operating voltage is applied in this manner, the lower end Dd of the depletion layer D is located within the fourth semiconductor region 14. The extent (position of the end) of the depletion layer can be estimated by calculation, such as simulation, based on the impurity concentration distribution in the light-receiving element and the voltage conditions during operation. Alternatively, the depletion layer width may be estimated based on the electrical capacitance of the light-receiving element, and the extent of the depletion layer may be estimated from the depletion layer width.

[0060] The third semiconductor region 13 is aligned with the structure 70 in the X-axis direction. For example, near the depletion layer formed in the third semiconductor region 13, the structure 70 suppresses the movement of carriers to the adjacent light receiving element 10 and the incidence of secondary photons. For example, even if the depletion layer expands due to the provision of the third semiconductor region 13, an increase in crosstalk noise can be suppressed.

[0061] FIG. 3 is a schematic cross-sectional view illustrating the photodetector according to the embodiment. 3 shows a photodetector 102 according to an embodiment. In this example, a plurality of light receiving elements 10, a plurality of structural portions 70, and a plurality of light collecting portions 40 are arranged in the XY plane. However, the number of light receiving elements 10, the number of structural portions 70, and the number of light collecting portions 40 may each be one or more. The photodetector 102 differs from the photodetector 101 in the planar shape of the third semiconductor region 13 and the thickness of the semiconductor layer 22.

[0062] 3, the third semiconductor region 13 includes a plurality of portions 13a and a plurality of portions 13b. A plurality of second semiconductor regions 12 are provided on each of the plurality of portions 13a. A plurality of first semiconductor regions 11 are provided on each of the plurality of second semiconductor regions 12. The portion 13a is, for example, a portion surrounded by a ring-shaped structural portion 70. For example, the portion 13a contacts the structural portion 70 and the portion 15a of the fifth semiconductor region 15.

[0063] The portion 13b is located between the adjacent portions 13a. The portion 13b is, for example, a portion provided outside the structure 70. For example, the portion 13b contacts the structure 70 and the portion 15d of the fifth semiconductor region 15.

[0064] In this way, the third semiconductor region 13 and the fourth semiconductor region 14 may be provided so as to extend across a plurality of light-receiving elements 10. The structure 70 may, for example, penetrate the third semiconductor region 13 and reach the fourth semiconductor region 14. The portion 13a and the portion 13b of the third semiconductor region 13 may be separated by the structure 70. In other words, the portion 13b may be separated from the portion 13a.

[0065] FIG. 4 is a schematic graph illustrating the distribution of impurity concentrations in the photodetector according to the embodiment. Fig. 4 shows the impurity concentration at the center of the light receiving element 10 of the photodetector 102 (the impurity concentration along the dashed-dotted line L2 shown in Fig. 3). Similar to Fig. 2, Fig. 4 shows the relationship between the impurity concentration C and the position Pz in the Z-axis direction, with the impurity concentration of the first conductivity type indicated by a solid line and the impurity concentration of the second conductivity type indicated by a dotted line. In this example, for example, the concentration Cx is higher than the concentration Cp, and the concentration Cy is higher than the concentration Cx.

[0066] For example, a thickness T15a (thickness of portion 15a) of the fifth semiconductor region 15 between the second semiconductor region 12 and the third semiconductor region 13 is thicker than a thickness T13 of the third semiconductor region 13. For example, the thickness of a region of the fifth semiconductor region 15 where the impurity concentration of the first conductivity type is constant along the Z-axis direction is thicker than the thickness T13 of the third semiconductor region 13. By making the fifth semiconductor region 15, which has a relatively low impurity concentration, thick, it is possible to increase the vertical width of the depletion layer, for example. By making the fifth semiconductor region 15 thick, it is possible to improve sensitivity, for example.

[0067] The thickness T15a of the fifth semiconductor region 15 may be thicker than the thickness T12 of the second semiconductor region 12, and may be thicker than the thickness T14 of the fourth semiconductor region 14. In this example, the thickness T15a of the fifth semiconductor region 15 is, for example, not less than 0.5 μm and not more than 25 μm.

[0068] When the thickness T15a of the fifth semiconductor region 15 is large, the third semiconductor region 13 may be formed, for example, by doping impurities into a portion of the semiconductor layer 22 when the semiconductor layer 22 is epitaxially grown on the semiconductor layer 21.

[0069] In the example of FIG. 4, the third semiconductor region 13 has a high concentration of the second conductivity type impurity between the upper end 13u and the lower end 13d of the third semiconductor region 13.

[0070] FIG. 5 is a schematic cross-sectional view illustrating the photodetector according to the embodiment. 5 shows a photodetector 103 according to the embodiment. The photodetector 103 differs from the photodetector 101 in the thicknesses of the third semiconductor region 13 and the fifth semiconductor region 15. In this example, the third semiconductor region 13 contacts the second semiconductor region 12. In other words, a part of the fifth semiconductor region 15 (portion 15a) does not have to be provided between the second semiconductor region 12 and the third semiconductor region 13.

[0071] FIG. 6 is a schematic graph illustrating the distribution of impurity concentrations in the photodetector according to the embodiment. Fig. 6 shows the impurity concentration at the center of the light receiving element 10 of the photodetector 103 (the impurity concentration along the dashed-dotted line L3 shown in Fig. 5). Similar to Fig. 2, Fig. 6 shows the relationship between the impurity concentration C and the position Pz in the Z-axis direction, with the impurity concentration of the first conductivity type indicated by a solid line and the impurity concentration of the second conductivity type indicated by a dotted line. In this example, for example, the concentration Cy is higher than the concentration Cx.

[0072] For example, the concentration Cx is higher than the concentration Cz. The concentration Cz is the concentration of the first conductivity type impurity at the boundary between the second semiconductor region 12 and the third semiconductor region 13. The concentration of the second conductivity type impurity is relatively high at the boundary between the fourth semiconductor region 14, which has a high impurity concentration and is less likely to be depleted, and the third semiconductor region 13. This allows, for example, the depletion layer in the fourth semiconductor region 14 to extend further downward.

[0073] FIG. 7 is a schematic cross-sectional view illustrating the photodetector according to the embodiment. 7 shows a photodetector 104 according to the embodiment. The photodetector 104 differs from the photodetector 101 in the thickness of the fifth semiconductor region 15 and the arrangement of the third semiconductor region 13. In this example, the third semiconductor region 13 contacts the second semiconductor region 12 and is spaced apart from the fourth semiconductor region 14.

[0074] For example, the fifth semiconductor region 15 includes a portion 15e instead of the portion 15a. The portion 15e is provided between the third semiconductor region 13 and the fourth semiconductor region 14. The portion 15e contacts both the third semiconductor region 13 and the fourth semiconductor region 14.

[0075] FIG. 8 is a schematic graph illustrating the distribution of impurity concentrations in the photodetector according to the embodiment. Fig. 8 shows the impurity concentration (the impurity concentration along the dashed dotted line L4 shown in Fig. 7) at the center of the light receiving element 10 of the photodetector 104. Like Fig. 2, Fig. 8 shows the relationship between the impurity concentration C and the position Pz in the Z-axis direction, with the impurity concentration of the first conductivity type indicated by a solid line and the impurity concentration of the second conductivity type indicated by a dotted line.

[0076] 8, a fifth semiconductor region 15 (portion 15e) in which the concentration of first conductivity type impurities is minimal is provided between the third semiconductor region 13 and the fourth semiconductor region 14. The fifth semiconductor region 15 has a low impurity concentration and is relatively easy to deplete. This allows, for example, the vertical width of the depletion layer to be increased.

[0077] 8, the concentration Cw is lower than the concentration Cz. The concentration Cw is the concentration of the first conductivity type impurity at the boundary between the third semiconductor region 13 and the fifth semiconductor region 15. The concentration of the second conductivity type impurity at the lower end 13d of the third semiconductor region 13 may be lower than the concentration of the second conductivity type impurity at the upper end 13u.

[0078] For example, the thickness T15e of the fifth semiconductor region 15 (the thickness of the portion 15e) is thicker than the thickness T13 of the third semiconductor region 13. The thickness of the fifth semiconductor region 15 can improve the sensitivity, for example. The thickness T15e of the fifth semiconductor region 15 may be thicker than the thickness T12 of the second semiconductor region 12 or may be thicker than the thickness T14 of the fourth semiconductor region 14.

[0079] Not limited to the above, in the embodiment, the fifth semiconductor region 15 may include both the portion 15a between the second semiconductor region 12 and the third semiconductor region 13 and the portion 15e between the third semiconductor region 13 and the fourth semiconductor region 14. In other words, the third semiconductor region 13 may be separated from the second semiconductor region 12 and the fourth semiconductor region 14.

[0080] FIG. 9 is a schematic plan view illustrating another photodetector according to the embodiment. The photodetector 105 shown in FIG. 9 includes a plurality of element structures similar to the structure described with reference to FIG. 1 and the like. The plurality of element structures are arranged in an array along the XY plane. The plurality of element structures are arranged periodically, for example, at equal pitches in the X-axis direction and the Y-axis direction. That is, the photodetector 105 includes an electrode 50, a semiconductor layer 21, a plurality of light receiving elements 10, a plurality of structural portions 70, a plurality of light collecting portions 40 (microlens arrays), and an insulating layer 30. With respect to adjacent element structures, the electrodes 50 are continuous with each other, the semiconductor layers 21 are continuous with each other, the semiconductor layers 22 are continuous with each other, and the insulating layers 30 are continuous with each other.

[0081] 9, the photodetector 105 further includes a plurality of first wirings 51, a common wiring 54, and a pad 55 (electrode). One first wiring 51 is electrically connected to a plurality of light receiving elements 10 arranged in the Y-axis direction. A plurality of first wirings 51 arranged in the X-axis direction are electrically connected to a common wiring 54. The common wiring 54 is electrically connected to one or more pads 55. The pad 55 is electrically connected to wiring of an external device.

[0082] FIG. 10 is a schematic plan view illustrating a part of the photodetector according to the embodiment. FIG. 11 is a schematic cross-sectional view illustrating a part of the photodetector according to the embodiment. Fig. 10 shows an enlarged view of region P of the photodetector 105 shown in Fig. 9. The light collecting portion 40 and the insulating layer 30 are omitted from Fig. 10. Fig. 11 shows a cross section taken along the line A4-A5 of Fig. 10. 10, the light receiving element 10 includes a photodiode PD. The photodiode PD is formed by, for example, a first semiconductor region 11, a second semiconductor region 12, a third semiconductor region 13 (portion 13a), a fourth semiconductor region (portion 14a), and a fifth semiconductor region (at least one of portion 15a and portion 15e).

[0083] The structure 70 surrounds the light receiving element 10 (photodiode PD). In this example, the structure 70 is substantially octagonal when viewed along the Z-axis direction. Each of the multiple structure 70 is provided so as to surround each of the multiple light receiving elements 10 along the XY plane. For example, the planar shape of the structure 70 in the XY plane is a polygonal ring. The structure 70 may also be rectangular when viewed from the Z-axis direction.

[0084] In the embodiments, the term "annular" refers not only to a circular shape when viewed from above, but also to a polygonal shape. The term "polygonal" includes polygons with curved (rounded) corners. That is, a polygon may have multiple sides (straight lines) and curves connecting the sides. The term "annular" does not only refer to a continuous, uninterrupted annular shape, but also to a circular or polygonal shape (e.g., a substantially C-shape) with one or more interruptions. For example, the structure 70 may discontinuously surround the light receiving element 10 when viewed from the Z-axis direction. In other words, the structure 70 may not be a complete annular structure when viewed from the Z-axis direction, but may have an open shape. In the embodiments, "surrounding" refers not only to a case where a certain component continuously surrounds another component without interruption, but also to a case where a plurality of components that are spaced apart from one another are arranged side by side around the other component. For example, if the other component is located inside a path obtained by tracing the plurality of components, the other component can be considered to be surrounded by the plurality of components. If the other component is located inside a circle or polygon with one or more interruptions in a plan view from above, the other component can be considered to be surrounded by the circle or polygon.

[0085] The structure 70 can suppress electrical conduction and optical interference between adjacent light-receiving elements 10. For example, the structure 70 can suppress the movement of secondary photons and carriers between the light-receiving elements 10. When light is incident on a light-receiving element 10 and secondary photons are generated, the secondary photons traveling to an adjacent light-receiving element 10 are reflected and refracted at the interface of the structure 70. The provision of the structure 70 can reduce crosstalk noise.

[0086] The multiple structures 70 are provided independently for each element. That is, the multiple structures 70 are not in physical contact with each other and are separated. Compared to when a single isolation structure is provided between adjacent light-receiving elements 10, the number of interfaces of the structures 70 between adjacent light-receiving elements 10 is increased. Due to the increased number of interfaces, when secondary photons are generated in a light-receiving element 10, secondary photons traveling toward the adjacent light-receiving element 10 are more likely to be reflected. This further reduces crosstalk noise. Between two adjacent structures 70, an outer periphery region (portion 15d of the fifth semiconductor region 15) is located. For example, the outer periphery region extends in the Y-axis direction between the structures 70 adjacent in the X-axis direction. The outer periphery region extends in the X-axis direction between the structures 70 adjacent in the Y-axis direction.

[0087] 11, the structure 70 may include a first insulating layer IL1 and a second insulating layer IL2. The second insulating layer IL2 is provided between the first insulating layer IL1 and the light receiving element 10, and between the first insulating layer IL1 and the semiconductor layer 21. For example, the first insulating layer IL1 and the second insulating layer IL2 contain silicon oxide, and the second insulating layer IL2 has a denser structure than the first insulating layer IL1.

[0088] 11, the fourth semiconductor region 14 may include a p-type semiconductor region 23 provided between the semiconductor layer 21 and the structural portion 70 in the Z-axis direction. For example, the p-type impurity concentration in the semiconductor region 23 is higher than the p-type impurity concentration in the portion 14a or the portion 14c of the fourth semiconductor region 14.

[0089] The quench portion 63 is provided to suppress the continuation of avalanche breakdown when light is incident on the light receiving element 10 and avalanche breakdown occurs. When avalanche breakdown occurs and current flows through the quench portion 63, a voltage drop occurs according to the electrical resistance of the quench portion 63. The voltage drop reduces the potential difference between the first semiconductor region 11 and the second semiconductor region 12, and the avalanche breakdown stops. This allows the next light incident on the light receiving element 10 to be detected.

[0090] In this example, a quench resistor is electrically connected to each light receiving element 10 as the quench section 63. The resistance of the quench section 63 is, for example, 50 kΩ or more and 6 MΩ or less. The quench resistor includes, for example, polysilicon as a semiconductor material. The quench resistor may be doped with n-type impurities or p-type impurities.

[0091] For example, when viewed from the Z-axis direction, the quench portion 63 is located at a position different from the photodiode PD. For example, the quench portion 63 is aligned with the structural portion 70 or the portion 15d of the fifth semiconductor region 15 in the Z-axis direction. The quench portion 63 is electrically connected to the conductive portion 61. As a result, one end of the quench portion 63 is electrically connected to the first semiconductor region 11 via the conductive portion 61. A plurality of quench portions 63 are provided, and each of the plurality of quench portions 63 is electrically connected to a corresponding one of the plurality of first semiconductor regions 11. The other end of the quench portion 63 is electrically connected to the first wiring 51.

[0092] Each of the plurality of conductive portions 61 is connected to each of the plurality of light receiving elements 10. Each of the plurality of conductive portions 61 includes a contact 64 and a connection wiring 65. The quench portion 63 is electrically connected to the first semiconductor region 11 via the contact 64 and the connection wiring 65, and is electrically connected to the first wiring 51 via the contact 66.

[0093] The contacts 64 and 66 include a metal material. For example, the contacts 64 and 66 include at least one selected from the group consisting of titanium, tungsten, copper, and aluminum. The contacts 64 and 66 may also include a conductor made of a nitride or silicon compound of at least one selected from the group consisting of titanium, tungsten, copper, and aluminum.

[0094] For example, the position of the quench portion 63 in the Z-axis direction is between the position of the first semiconductor region 11 in the Z-axis direction and the position of the first wiring 51 in the Z-axis direction. One first wiring 51 is electrically connected to multiple photodiodes PD lined up in the Y-axis direction.

[0095] The electrical resistance of the quench portion 63 is greater than the electrical resistance of each of the contact 64, the contact 66, and the connection wiring 65. The quench resistor includes polysilicon as a semiconductor material. The quench resistor may be doped with n-type impurities or p-type impurities.

[0096] For example, the insulating layer 30 includes first to fourth layers 31 to 34. The first to third layers 31 to 33 are provided between the plurality of light receiving elements 10 and the fourth layer 34 in the Z-axis direction. The first layer 31 and the second layer 32 are provided between the plurality of light receiving elements 10 and the third layer 33 in the Z-axis direction. The first layer 31 is provided between the plurality of light receiving elements 10 and the second layer 32 in the Z-axis direction.

[0097] The contacts 64 and 66 are surrounded by the first layer 31, the second layer 32, and the third layer 33 along the XY plane. A part of the first layer 31 is provided between the portion 15d of the fifth semiconductor region 15 and the quench portion 63 in the Z-axis direction. The first wiring 51 and the connection wiring 65 are surrounded by the fourth layer 34.

[0098] FIG. 12 is a schematic diagram illustrating an active quench circuit. In the photodetectors according to the embodiments described above, a resistor that generates a large voltage drop is provided as the quench unit 63. In the photodetectors according to the embodiments, a control circuit and a switching element may be provided instead of the resistor. That is, an active quench circuit for cutting off current is provided as the quench unit 63.

[0099] 12, the active quench circuit includes a control circuit CC and a switching array SWA. The control circuit CC includes a comparator, a control logic unit, etc. The switching array SWA includes a plurality of switching elements SW. For example, at least some of the circuit elements included in the control circuit CC and the switching elements SW may be provided on the semiconductor layer 22, or may be provided on a circuit board separate from the semiconductor layer 22.

[0100] 12, one switching element SW may be provided for one light receiving element 10 (element region), or one switching element SW may be provided for multiple light receiving elements 10. For example, one switching element SW is provided between one first semiconductor region 11 and the first wiring 51. Alternatively, the switching element SW may be provided in the first wiring 51. For example, the switching element SW may be provided between the first wiring 51 and the pad 55.

[0101] FIG. 13 is a schematic diagram illustrating a LIDAR (Laser Imaging Detection and Ranging) device according to the embodiment. This embodiment is configured with a line light source and a lens and can be applied to a long-range object detection system (LIDAR), etc. The LIDAR device 5001 includes a light projection unit T that projects laser light toward an object 411, and a light receiving unit R (also called a light detection system) that receives the laser light from the object 411, measures the time it takes for the laser light to travel to and from the object 411, and converts it into distance.

[0102] In the light-projecting unit T, a light source 404 emits light. For example, the light source 404 includes a laser oscillator and emits laser light. A drive circuit 403 drives the laser oscillator. An optical system 405 extracts a portion of the laser light as reference light, and irradiates the remaining laser light onto an object 411 via a mirror 406. A mirror controller 402 controls the mirror 406 to project the laser light onto the object 411. Here, "projecting light" means to apply light.

[0103] In the light receiving unit R, a reference light photodetector 409 detects the reference light extracted by the optical system 405. A photodetector 410 receives reflected light from an object 411. A distance measurement circuit 408 measures the distance to the object 411 based on the reference light detected by the reference light photodetector 409 and the reflected light detected by the photodetector 410. An image recognition system 407 recognizes the object 411 based on the result of measurement by the distance measurement circuit 408.

[0104] The LIDAR device 5001 employs an optical time-of-flight ranging method that measures the time it takes for laser light to travel to and from the target 411 and converts the time into distance. The LIDAR device 5001 is applied to in-vehicle drive-assist systems, remote sensing, and the like. When the photodetector of the above-described embodiment is used as the photodetector 410, it exhibits good sensitivity, particularly in the near-infrared region. This makes it possible for the LIDAR device 5001 to be applied to a light source in a wavelength band invisible to humans. The LIDAR device 5001 can be used, for example, for obstacle detection for moving objects.

[0105] FIG. 14 is a diagram for explaining detection of a detection target by a LIDAR device. A light source 3000 emits light 412 toward an object 600 to be detected. A photodetector 3001 detects light 413 that is transmitted through, reflected from, or diffused by the object 600.

[0106] For example, when the photodetector 3001 is the photodetector according to the present embodiment described above, high-sensitivity detection can be achieved. It is preferable to provide a plurality of sets of photodetectors 410 and light sources 404, and to set their layout relationship in advance in software (also possible with a circuit). It is preferable that the layout relationship of the sets of photodetectors 410 and light sources 404 be, for example, equidistant. This allows the output signals of the respective photodetectors 410 to complement each other, thereby generating an accurate three-dimensional image.

[0107] FIG. 15 is a schematic top view of a moving body equipped with a LIDAR device according to an embodiment. 15, the moving body is a car. Vehicle 700 according to this embodiment is equipped with LIDAR devices 5001 at the four corners of vehicle body 710. By providing LIDAR devices at the four corners of the vehicle body, the vehicle according to this embodiment can detect the environment in all directions of the vehicle using the LIDAR devices.

[0108] The moving object may be a drone, a robot, or the like, in addition to the car shown in Figure 15. The robot may be, for example, an automated guided vehicle (AGV). By providing LIDAR devices at the four corners of these moving objects, the LIDAR devices can detect the environment in all directions around the moving object.

[0109] According to the embodiments, it is possible to provide a photodetector, a photodetection system, a LIDAR device, and a moving object that can improve responsiveness.

[0110] In this specification, "vertical" does not only mean strictly vertical, but also includes variations in the manufacturing process, for example, and may mean substantially vertical. In this specification, "electrically connected" includes not only connection through direct contact but also connection via other conductive members.

[0111] Embodiments may include the following features. (Configuration 1) a semiconductor layer of a first conductivity type; A light receiving element, a first semiconductor region of a second conductivity type; a second semiconductor region of the first conductivity type provided between the first semiconductor region and the semiconductor layer and in contact with the first semiconductor region; a third semiconductor region of the second conductivity type provided between the second semiconductor region and the semiconductor layer; a fourth semiconductor region of the first conductivity type provided between the third semiconductor region and the semiconductor layer, the fourth semiconductor region having a first conductivity type impurity concentration lower than a first conductivity type impurity concentration in the semiconductor layer; a light receiving element including A photodetector comprising: (Configuration 2) Further comprising a structure having a refractive index different from that of the light receiving element, 2. The photodetector of claim 1, wherein the third semiconductor region is aligned with the structure in a direction perpendicular to a first direction from the semiconductor layer toward the light receiving element. (Configuration 3) 3. The photodetector according to configuration 1 or 2, wherein the impurity concentration of the first conductivity type at the boundary between the first semiconductor region and the second semiconductor region is higher than the impurity concentration of the first conductivity type at the boundary between the third semiconductor region and the fourth semiconductor region. (Configuration 4) 4. The photodetector according to any one of configurations 1 to 3, wherein the maximum value of the concentration of the second conductivity type impurities in the third semiconductor region is lower than the maximum value of the concentration of the first conductivity type impurities in the second semiconductor region. (Configuration 5) 5. The photodetector according to any one of configurations 1 to 4, wherein the third semiconductor region is in contact with the fourth semiconductor region. (Configuration 6) the light receiving element is provided between the second semiconductor region and the third semiconductor region and includes a fifth semiconductor region of a first conductivity type; 6. The photodetector according to any one of configurations 1 to 5, wherein the impurity concentration of the first conductivity type in the light receiving element is minimized in the fifth semiconductor region. (Configuration 7) 7. The photodetector according to configuration 6, wherein a concentration of the first conductivity type impurity at the boundary between the third semiconductor region and the fourth semiconductor region is higher than a concentration of the first conductivity type impurity in the fifth semiconductor region. (Configuration 8) the third semiconductor region is in contact with the second semiconductor region, The photodetector according to any one of configurations 1 to 5, wherein the impurity concentration of the first conductivity type at the boundary between the third semiconductor region and the fourth semiconductor region is higher than the impurity concentration of the first conductivity type at the boundary between the third semiconductor region and the second semiconductor region. (Configuration 9) the light receiving element is provided between the third semiconductor region and the fourth semiconductor region and includes a fifth semiconductor region of a first conductivity type; 5. The photodetector according to any one of configurations 1 to 4, wherein the impurity concentration of the first conductivity type in the light receiving element is minimized in the fifth semiconductor region. (Configuration 10) 10. The photodetector according to any one of configurations 1 to 9, wherein the third semiconductor region is thinner than the second semiconductor region. (Configuration 11) 8. The photodetector of claim 6 or 7, wherein a thickness of the fifth semiconductor region between the second semiconductor region and the third semiconductor region is greater than a thickness of the third semiconductor region. (Configuration 12) A photodetector according to any one of configurations 1 to 11, wherein, during operation of the light receiving element, an end of a depletion layer formed in a range including the boundary between the first semiconductor region and the second semiconductor region is located within the fourth semiconductor region. (Configuration 13) 13. The photodetector according to any one of configurations 1 to 12, further comprising a resistor electrically connected to the light receiving element, or a switching element electrically connected to the light receiving element. (Configuration 14) 14. The photodetector according to any one of configurations 1 to 13, wherein the light receiving element is a PiN diode or an avalanche photodiode. (Configuration 15) 15. The photodetector of claim 14, wherein the avalanche photodiode operates in Geiger mode. (Configuration 16) The photodetector according to any one of configurations 1 to 15, a distance measurement circuit that calculates a time of flight of light from the output signal of the photodetector; An optical detection system comprising: (Configuration 17) a light source that irradiates light onto an object; 17. A light detection system according to configuration 16 for detecting light reflected by the object; A lidar device comprising: (Configuration 18) 18. The LIDAR device of claim 17, further comprising an image recognition system that generates a three-dimensional image based on the positional relationship between the light source and the photodetector. (Configuration 19) A moving body equipped with the LIDAR device according to aspect 17 or 18.

[0112] The embodiments of the present invention have been described above with reference to specific examples. However, the present invention is not limited to these specific examples. For example, the specific configurations of the elements, such as the semiconductor layers and light-receiving elements, included in the photodetector are within the scope of the present invention as long as a person skilled in the art can implement the present invention in a similar manner and obtain similar effects by appropriately selecting them from known ranges.

[0113] Any combination of two or more elements of each embodiment to the extent technically possible is also included within the scope of the present invention as long as it encompasses the gist of the present invention.

[0114] In addition, all photodetectors, photodetection systems, LIDAR devices, and moving bodies that can be implemented by a person skilled in the art by appropriately modifying the design based on the photodetectors, photodetection systems, LIDAR devices, and moving bodies described above as embodiments of the present invention also fall within the scope of the present invention, as long as they include the gist of the present invention.

[0115] In addition, within the scope of the concept of the present invention, a person skilled in the art may come up with various modifications and alterations, and it will be understood that these modifications and alterations also fall within the scope of the present invention.

[0116] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0117] 10...light receiving element, 10f...light receiving surface, 11...first semiconductor region, 12...second semiconductor region, 12d...lower end, 12u...upper end, 13...third semiconductor region, 13a, 13b...portion, 13d...lower end, 13u...upper end, 14...fourth semiconductor region, 14a, 14b, 14c, 14d...portion, 15...fifth semiconductor region, 15a, 15b, 15c, 15d, 15e...portion, 21...semiconductor layer, 22...semiconductor layer, 23...semiconductor region, 30...insulating layer, 31-34...first to fourth layers, 40...light collecting portion, 50...electrode, 51...first wiring, 54...common wiring, 55...pad, 61...conductive portion, 63...quench portion, 64...contact, 65...connecting wiring, 66...contact, 70...structural part, 101 to 105...photodetector, 402...mirror controller, 403...drive circuit, 404...light source, 405...optical system, 406...mirror, 407...image recognition system, 408...distance measurement circuit, 409...reference light photodetector, 410...photodetector, 411...target object, 412, 413...light, 600...object, 700...vehicle, 710...vehicle body, 3000...light source, 3001...photodetector, 5001...lidar device, C12, C13...concentration, CC...control circuit, Cp, Cw, Cx, Cy, Cz...concentration, D...depletion layer, Dd...lower end, Du...upper end, IL1...first insulating layer, IL2...second insulating layer, PD...photodiode, R...receiving unit, SW...switching element, SWA...switching array, T...emitting unit, T12, T13, T14, T15a, T15e...thickness

Claims

1. A photodetector comprising a semiconductor layer of a first conductivity type, which is one of p-type and n-type, and a light-receiving element, The light receiving element is a first semiconductor region of a second conductivity type, which is the other of p-type and n-type; a second semiconductor region of the first conductivity type provided between the first semiconductor region and the semiconductor layer and in contact with the first semiconductor region; a third semiconductor region of the second conductivity type provided between the second semiconductor region and the semiconductor layer; a fourth semiconductor region of the first conductivity type provided between the third semiconductor region and the semiconductor layer, the fourth semiconductor region having a first conductivity type impurity concentration lower than a first conductivity type impurity concentration in the semiconductor layer; Including, the third semiconductor region is provided at the center of the light receiving element in a plane perpendicular to a first direction from the semiconductor layer toward the light receiving element, In the plane, a center position of the third semiconductor region coincides with at least one of a center position of the first semiconductor region and a center position of the second semiconductor region; a depletion layer extending continuously from the first semiconductor region to the fourth semiconductor region when the light receiving element is in operation;

2. Further comprising a structure having a refractive index different from that of the light receiving element, The photodetector according to claim 1 , wherein the third semiconductor region is aligned with the structure in a direction perpendicular to a first direction from the semiconductor layer toward the light receiving element.

3. 2. The photodetector according to claim 1, wherein a concentration of impurities of the first conductivity type at a boundary between the first semiconductor region and the second semiconductor region is higher than a concentration of impurities of the first conductivity type at a boundary between the third semiconductor region and the fourth semiconductor region.

4. 2. The photodetector according to claim 1, wherein a maximum value of the impurity concentration of the second conductivity type in said third semiconductor region is lower than a maximum value of the impurity concentration of the first conductivity type in said second semiconductor region.

5. The photodetector of claim 1 , wherein the third semiconductor region is in contact with the fourth semiconductor region.

6. the light receiving element is provided between the second semiconductor region and the third semiconductor region and includes a fifth semiconductor region of a first conductivity type; 6. The photodetector according to claim 1, wherein the impurity concentration of the first conductivity type in said light receiving element is minimum in said fifth semiconductor region.

7. 7. The photodetector according to claim 6, wherein a concentration of the impurity of the first conductivity type at the boundary between said third semiconductor region and said fourth semiconductor region is higher than a concentration of the impurity of the first conductivity type in said fifth semiconductor region.

8. the third semiconductor region is in contact with the second semiconductor region, 6. The photodetector according to claim 1, wherein a concentration of impurities of the first conductivity type at a boundary between the third semiconductor region and the fourth semiconductor region is higher than a concentration of impurities of the first conductivity type at a boundary between the third semiconductor region and the second semiconductor region.

9. the light receiving element is provided between the third semiconductor region and the fourth semiconductor region and includes a fifth semiconductor region of a first conductivity type; 5. The photodetector according to claim 1, wherein the impurity concentration of the first conductivity type in the light receiving element is minimized in the fifth semiconductor region.

10. 6. The photodetector according to claim 1, wherein the thickness of said third semiconductor region is thinner than the thickness of said second semiconductor region.

11. The photodetector according to claim 6 , wherein a thickness of the fifth semiconductor region between the second semiconductor region and the third semiconductor region is greater than a thickness of the third semiconductor region.

12. A photodetector according to any one of claims 1 to 5, wherein, during operation of the light receiving element, an end of a depletion layer formed in a range including the boundary between the first semiconductor region and the second semiconductor region is located within the fourth semiconductor region.

13. 6. The photodetector according to claim 1, further comprising a resistor electrically connected to the light receiving element, or a switching element electrically connected to the light receiving element.

14. 6. The photodetector according to claim 1, wherein the light receiving element is a PiN diode or an avalanche photodiode.

15. The photodetector of claim 14 , wherein the avalanche photodiode operates in Geiger mode.

16. A photodetector according to any one of claims 1 to 5; a distance measurement circuit that calculates a time of flight of light from the output signal of the photodetector; An optical detection system comprising:

17. a light source that irradiates light onto an object; 17. The light detection system of claim 16, which detects light reflected from the object; A lidar device comprising:

18. The LIDAR device according to claim 17 , further comprising an image recognition system that generates a three-dimensional image based on the relative positions of the light source and the photodetector.

19. A moving object equipped with the LIDAR device according to claim 17.

20. A photodetector comprising a semiconductor layer of a first conductivity type, which is one of p-type and n-type, and a light-receiving element, The light receiving element is a first semiconductor region of a second conductivity type, which is the other of p-type and n-type; a second semiconductor region of the first conductivity type provided between the first semiconductor region and the semiconductor layer and in contact with the first semiconductor region; a third semiconductor region of the second conductivity type provided between the second semiconductor region and the semiconductor layer; a fourth semiconductor region of the first conductivity type provided between the third semiconductor region and the semiconductor layer, the fourth semiconductor region having a first conductivity type impurity concentration lower than a first conductivity type impurity concentration in the semiconductor layer; Including, the third semiconductor region is in contact with the second semiconductor region, an impurity concentration of the first conductivity type at a boundary between the first semiconductor region and the second semiconductor region is higher than an impurity concentration of the first conductivity type at a boundary between the third semiconductor region and the fourth semiconductor region; a depletion layer extending continuously from the first semiconductor region to the fourth semiconductor region when the light receiving element is in operation;

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