LIGHT DETECTOR, LIGHT DETECTION SYSTEM, LIDAR DEVICE, AND MOBILE BODY

A light detector includes 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 located between the first semiconductor region and the semiconductor layer. The second semiconductor region is of the first conductivity type and contacts the first semiconductor region. The third semiconductor region is located between the second semiconductor region and the semiconductor layer. The third semiconductor region is of the second conductivity type. The fourth semiconductor region is located between the third semiconductor region and the semiconductor layer. The fourth semiconductor region is of the first conductivity type, and has a lower first-conductivity-type impurity concentration than a first-conductivity-type impurity concentration of the semiconductor layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2022-134853, filed on Aug. 26, 2022; the entire contents of which are incorporated herein by reference.

FIELD

Embodiments relate to a light detector, a light detection system, a lidar device, and a mobile body.

BACKGROUND

There is a light detector that detects light incident on a semiconductor region. It is desirable to improve the responsivity of the light detector.

DETAILED DESCRIPTION

A light detector according to one embodiment, includes 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 located between the first semiconductor region and the semiconductor layer. The second semiconductor region is of the first conductivity type and contacts the first semiconductor region. The third semiconductor region is located between the second semiconductor region and the semiconductor layer. The third semiconductor region is of the second conductivity type. The fourth semiconductor region is located between the third semiconductor region and the semiconductor layer. The fourth semiconductor region is of the first conductivity type. The fourth semiconductor region has a lower first-conductivity-type impurity concentration than a first-conductivity-type impurity concentration of the semiconductor layer.

Exemplary embodiments will now be described with reference to the drawings.

The drawings are schematic or conceptual; and the relationships between the thickness and width of portions, the proportional coefficients of sizes among portions, etc., are not necessarily the same as the actual values thereof. Furthermore, the dimensions and proportional coefficients may be illustrated differently among drawings, even for identical portions.

In the specification of the application and the drawings, components similar to those described in regard to a drawing thereinabove are marked with like reference numerals, and a detailed description is omitted as appropriate.

According to embodiments, a first conductivity type is one of a p-type or an n-type. A second conductivity type is the other of the p-type or the n-type. In the following description, the first conductivity type is the p-type, and the second conductivity type is the n-type.

FIG.1is a schematic cross-sectional view illustrating a light detector according to an embodiment.

As illustrated inFIG.1, the light detector101according to the embodiment includes a light-receiving element10(an element region) and a semiconductor layer21(a first semiconductor layer). In the example, the light detector101further includes an insulating layer30, a light concentrator40, an electrode50, and a structure part70. The light-receiving element10is located on the semiconductor layer21.

In the description of the embodiments, the direction from the semiconductor layer21toward the light-receiving element10is taken as a Z-axis direction (a first direction). A direction perpendicular to the Z-axis direction is taken as an X-axis direction (a second direction). The X-axis direction is parallel to the front surface of a semiconductor layer22. A direction perpendicular to the Z-axis direction and the X-axis direction is taken as a Y-axis direction (a third direction). In the description, the direction from the semiconductor layer21toward the light-receiving element10is called “up”, and the opposite direction is called “down”. These directions are based on the relative positional relationship between the semiconductor layer21and the light-receiving element10and are independent of the direction of gravity. “Up” corresponds to the side at which the light concentrator40is mounted and at which light is incident on the light detector.

The electrode50is, for example, a back electrode. The semiconductor layer21is located on the electrode50and is electrically connected with the electrode50. The semiconductor layer21is, for example, a semiconductor substrate of the first conductivity type. A semiconductor region14is located on the semiconductor layer21. The semiconductor region14is, for example, a portion of an epitaxial layer of the first conductivity type. The semiconductor region15is located on the semiconductor region14. The semiconductor region15is, for example, a portion of an epitaxial layer of the first conductivity type.

The light-receiving element10includes a first semiconductor region11, a second semiconductor region12, a third semiconductor region13, and the fourth semiconductor region14. The first semiconductor region11is of the second conductivity type. The first semiconductor region11is electrically connected with a first wiring part51described below via a contact64and an interconnect65. The first wiring part51is electrically connected with a pad55described below. The pad55is electrically connected with an external electronic device via a bonding wire, etc.

The second semiconductor region12is located between the first semiconductor region11and the semiconductor layer21. The second semiconductor region12is of the first conductivity type. The second semiconductor region12contacts the first semiconductor region11.

The third semiconductor region13is located between the second semiconductor region12and the semiconductor layer21. The third semiconductor region13is of the second conductivity type.

At least a portion of the fourth semiconductor region14is located between the third semiconductor region13and the semiconductor layer21. The fourth semiconductor region14is of the first conductivity type. The fourth semiconductor region14contacts the semiconductor layer21. In the example, the fourth semiconductor region14contacts the third semiconductor region13. The fourth semiconductor region14may not contact the third semiconductor region13.

In the example, the light-receiving element10further includes the fifth semiconductor region15. At least a portion of the fifth semiconductor region15is located between the second semiconductor region12and the third semiconductor region13. The fifth semiconductor region15is of the first conductivity type. The fifth semiconductor region15contacts the second and third semiconductor regions12and13. The fifth semiconductor region15is electrically connected with the second and third semiconductor regions12and13.

The first semiconductor region11of the second conductivity type is electrically connected with the pad55described below via the first wiring part51described below. The third semiconductor region13of the second conductivity type and the semiconductor regions12,14, and15of the first conductivity type are electrically connected with the electrode50via the semiconductor layer21.

The first to fifth semiconductor regions11to15are, for example, regions located in one semiconductor layer22(a second semiconductor layer). The semiconductor layer22is located on the semiconductor layer21(e.g., a substrate). The semiconductor layer22contacts the semiconductor layer21and is electrically connected with the semiconductor layer21. For example, the light-receiving element10(the first semiconductor region11, the second semiconductor region12, and the third semiconductor region13) is located inside the semiconductor layer22in which the fourth semiconductor region14and the fifth semiconductor region15are located.

A photodiode (a pixel) is formed of the first and second semiconductor regions11and12(and portions of the third to fifth semiconductor regions13to15). The photodiode (the light-receiving element10) includes a light-receiving surface10f. The light-receiving surface10fis the upper surface of the first semiconductor region11.

The structure part70is arranged with the light-receiving element10in a direction crossing the Z-axis direction. The structure part70is, for example, a structure body located inside a trench provided in the semiconductor layer22. The structure part70surrounds the light-receiving element10. The planar shape (the shape in the X-Y plane perpendicular to the Z-axis direction) of the structure part70is, for example, ring-shaped.

The structure part70includes a different material from the regions (the first to fifth semiconductor regions11to15) of the semiconductor layer22. The refractive index of the structure part70is different from the refractive indexes of the regions of the semiconductor layer22. The refractive index of the structure part70is different from the refractive index of the light-receiving element10. The structure part70is insulative. At least a portion of the trench interior (the structure part70) may be hollow.

For example, the depth of the structure part70(the trench) is deeper than the third semiconductor region13. In other words, the position in the Z-axis direction of the lower end of the structure part70is between the position in the Z-axis direction of the lower end of the third semiconductor region13and the position in the Z-axis direction of the semiconductor layer21(or the electrode50). The ring-shaped structure part70surrounds the third semiconductor region13. The length along the Z-axis direction of the structure part70(the depth of the trench) is, for example, not less than 5 μm and not more than 10 μm. The thickness of the semiconductor layer22is, for example, not less than 3 μm and not more than 30 μm.

In the example ofFIG.1, the fourth semiconductor region14includes a portion14a, a portion14b, and a portion14c. The portion14ais located between the third semiconductor region13and the semiconductor layer21in the Z-axis direction.

The portion14bis located between the third semiconductor region13and the structure part70in the X-axis direction (and directions in the X-Y plane). The portion14bcontacts the structure part70and the third semiconductor region13. For example, the portion14bsurrounds the third semiconductor region13at the inner side of the ring-shaped structure part70. The portion14bmay be omitted. In other words, the third semiconductor region13may contact the structure part70.

The portion14cis located at the outer side of the structure part70and contacts the structure part70. The portion14csurrounds the structure part70. In other words, the structure part70is located between the portion14cand the portion14band between the portion14cand the portion14a.

For example, the lower end of the structure part70contacts the fourth semiconductor region14. The portion14aat the inner side of the structure part70is continuous with the portion14cat the outer side of the structure part70via the portion of the semiconductor layer22below the structure part70.

In the example ofFIG.1, the fifth semiconductor region15includes a portion15a, a portion15b, a portion15c, and a portion15d. The portion15ais located between the second semiconductor region12and the third semiconductor region13.

The portion15bis located between the first semiconductor region11and the structure part70and between the second semiconductor region12and the structure part70. The portion15bcontacts the first semiconductor region11, the second semiconductor region12, and the structure part70. For example, the portion15bsurrounds the first semiconductor region11and the second semiconductor region12at the inner side of the ring-shaped structure part70.

The portion15cis located between the third semiconductor region13and the structure part70. The portion15ccontacts the third semiconductor region13and the structure part70. For example, the portion15csurrounds the third semiconductor region13at the inner side of the ring-shaped structure part70.

The portion15dis located at the outer side of the structure part70and contacts the structure part70. The portion15dsurrounds the structure part70. In other words, the structure part70is located between the portion15dand the portion15band between the portion15dand the portion15c. The portion15dat the outer side of the structure part70may be partitioned from the portions15a,15b, and15cat the inner side of the structure part70and separated from the portions15a,15b, and15cat the inner side of the structure part70by the structure part70.

The portion15band the portion15cmay be omitted. In other words, the first semiconductor region11, the second semiconductor region12, and the third semiconductor region13may contact the structure part70.

In the example, the fifth semiconductor region15contacts the fourth semiconductor region14. Specifically, the portion14bcontacts the portion15c; and the portion14ccontacts the portion15d.

For example, the planar shape of the third semiconductor region13may be wider than the planar shape of the first semiconductor region11and may be wider than the planar shape of the second semiconductor region12. For example, the length along the X-axis direction of the third semiconductor region13may be greater than the length along the X-axis direction of the first semiconductor region11and may be greater than the length along the X-axis direction of the second semiconductor region12.

However, the planar shapes are not limited thereto; the planar shape of the third semiconductor region13may be narrower than the planar shape of the first semiconductor region11and narrower than the planar shape of the second semiconductor region12. For example, the length along the X-axis direction of the third semiconductor region13may be equal to or less than the length along the X-axis direction of the first semiconductor region11and may be equal to or less than the length along the X-axis direction of the second semiconductor region12.

For example, the third semiconductor region13is located at the center of the light-receiving element10in the X-Y plane. For example, in the X-Y plane, the center position of the third semiconductor region13may match at least one of the center position of the first semiconductor region11, the center position of the second semiconductor region12, or the center position of the ring-shaped structure part70.

The insulating layer30is located on the semiconductor layer22and contacts, for example, the upper surface of the semiconductor layer22. The light concentrator40is located on the insulating layer30and contacts, for example, the upper surface of the insulating layer30. The light concentrator40is an upwardly convex lens (e.g., a microlens). The light concentrator40can concentrate the incident light. In other words, at least a portion of the incident light is refracted and caused to travel toward the light-receiving element10by the light concentrator40.

The incident light is, for example, near-infrared light. The wavelength of the near-infrared light is, for example, not less than 0.7 micrometers (μm) and not more than 2.5 μm. However, according to the embodiment, the incident light is not necessarily near-infrared light.

FIG.2is a schematic graph illustrating the distributions of the impurity concentrations in the light detector according to the embodiment.

FIG.2illustrates the impurity concentrations at the central portion of the light-receiving element10of the light detector101(the impurity concentrations along a single dot-dash line L1shown inFIG.1). The vertical axis ofFIG.2is an impurity concentration C (atoms per cubic centimeter (atoms/cm3)), and the horizontal axis ofFIG.2is a position Pz (μm) in the Z-axis direction. The position at which the value of the horizontal axis is zero is the position of the light-receiving surface10f; and the position moves downward as the value of the horizontal axis increases. InFIG.2, the first-conductivity-type impurity concentration is illustrated by a solid line; and the second-conductivity-type impurity concentration is illustrated by a dotted line.

As illustrated inFIG.2, the first-conductivity-type impurity concentration of the fourth semiconductor region14is less than the first-conductivity-type impurity concentration of the semiconductor layer21. For example, the first-conductivity-type impurity concentration of the fourth semiconductor region14monotonously increases in the direction from the fifth semiconductor region15toward the semiconductor layer21. The fourth semiconductor region14is, for example, a concentration transition region.

The first-conductivity-type impurity concentration of the fifth semiconductor region15is less than the first-conductivity-type impurity concentration of the second semiconductor region12and less than the first-conductivity-type impurity concentration of the fourth semiconductor region14. The first-conductivity-type impurity concentration of the light-receiving element10has a minimum in the fifth semiconductor region15. In other words, the fifth semiconductor region15is a region in which the first-conductivity-type impurity concentration has a minimum (e.g., a lowest value) in the range along the Z-axis direction from the second semiconductor region12to the semiconductor layer21.

For example, the impurity concentration distribution of the first conductivity type has a peak in the second semiconductor region12. In other words, in the example, the maximum value of the first-conductivity-type impurity concentration (a maximum impurity concentration C12) in the second semiconductor region12is the maximum value between an upper end12uof the second semiconductor region12and a lower end12dof the second semiconductor region12.

The first-conductivity-type impurity concentration of the semiconductor layer21is, for example, not less than 1.0×1018 (atoms/cm3) and not more than 1.0×1019 (atoms/cm3).

The first-conductivity-type impurity concentration of the second semiconductor region12is, for example, not less than 1.0×1016 (atoms/cm3) and not more than 1.0×1018 (atoms/cm3).

The first-conductivity-type impurity concentration of the fifth semiconductor region15is, for example, not less than 1.0×1013 (atoms/cm3) and not more than 1.0×1016 (atoms/cm3).

The second-conductivity-type impurity concentration of the third semiconductor region13is less than the second-conductivity-type impurity concentration of the first semiconductor region11.

The second-conductivity-type impurity concentration of the first semiconductor region11is, for example, not less than 1.0×1018 (atoms/cm3) and not more than 1.0×1021 (atoms/cm3).

The second-conductivity-type impurity concentration of the third semiconductor region13is, for example, not less than 1.0×1013 (atoms/cm3) and not more than 1.0×1016 (atoms/cm3).

As illustrated inFIG.2, for example, a concentration Cx is greater than a concentration Cp. The concentration Cx is the first-conductivity-type impurity concentration at the boundary between the third semiconductor region13and the fourth semiconductor region14. The concentration Cp is the first-conductivity-type impurity concentration of the fifth semiconductor region15. The concentration Cp is, for example, a minimum value (e.g., a lowest value) of the first-conductivity-type impurity concentration of the light-receiving element10.

The impurity concentration at the boundary between an n-type region and a p-type region is the impurity concentration at the position (the depth) at which the n-type impurity concentration and the p-type impurity concentration are the same between the n-type region and the p-type region. 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.

As illustrated inFIG.2, for example, a concentration Cy is greater than the concentration Cx. The concentration Cy is the first-conductivity-type impurity concentration at the boundary between the first semiconductor region11and the second semiconductor region12.

For example, the impurity concentration distribution of the second conductivity type has a peak in the third semiconductor region13. In other words, in the example, the maximum value of the second-conductivity-type impurity concentration (a maximum impurity concentration C13) of the third semiconductor region13is the maximum value between an upper end13uof the third semiconductor region13and a lower end13dof the third semiconductor region13. As illustrated inFIG.2, for example, the maximum impurity concentration C13is less than the maximum impurity concentration C12.

For example, the impurity concentrations of the semiconductor layer and the semiconductor regions are measured by SIMS (secondary ion mass spectrometry).

In the example, a thickness (a length along the Z-axis direction) T13of the third semiconductor region13is less than a thickness T12of the second semiconductor region12. For example, a thickness T15a(the thickness of the portion15a) of the fifth semiconductor region15is less than the thickness T13of the third semiconductor region13. For example, a thickness T14of the fourth semiconductor region14is greater than the thickness T12of the second semiconductor region12.

The thickness T12is, for example, not less than 1 μm and not more than 4 μm. The thickness T13is, for example, not less than 0.5 μm and not more than 4 μm. The thickness T14is, for example, not less than 1 μm and not more than 7 μm. The thickness T15ais, for example, not less than 0 μm and not more than 8 μm.

Materials of the components of the light detector101will now be described.

The semiconductor layer21and the semiconductor layer22(the first semiconductor region11, the second semiconductor region12, the third semiconductor region13, the fourth semiconductor region14, and the fifth semiconductor region15) include at least one semiconductor material selected from the group consisting of silicon, silicon carbide, gallium arsenide, and gallium nitride. For example, the semiconductor layer21and the semiconductor layer22include silicon. The first semiconductor region11and the third semiconductor region13each are obtained by implanting, for example, phosphorus, arsenic, or antimony as an n-type impurity into silicon. The second semiconductor region12is obtained by implanting, for example, boron as a p-type impurity into silicon.

The semiconductor layer22is, for example, an epitaxial layer formed on a substrate (the semiconductor layer21). For example, the first semiconductor region11, the second semiconductor region12, and the third semiconductor region13can be formed by ion implantation into an epitaxial layer that includes the fourth and fifth semiconductor regions14and15and is formed by epitaxial growth on the semiconductor layer21. For example, the third semiconductor region13is formed by implanting the second-conductivity-type impurity to overlap the fourth semiconductor region14in which the concentration of the first-conductivity-type impurity transitions. For example, the region of the epitaxial layer into which an impurity is not ion-implanted can be used to form the fifth semiconductor region15.

The structure part70includes a different material from the material of the semiconductor layer22(the light-receiving element10). Specifically, the structure part70includes an insulating material. For example, the structure part70includes silicon and one selected from the group consisting of oxygen and nitrogen. For example, the structure part70includes silicon oxide or silicon nitride. The structure part70may have a stacked structure.

The light concentrator40includes a light-transmissive material. For example, the light concentrator40includes a light-transmissive resin such as an acrylic resin, etc.

The insulating layer30includes, for example, a light-transmissive material. For example, the insulating layer30includes silicon and one selected from the group consisting of oxygen and nitrogen. For example, the insulating layer30includes at least one of silicon oxide or silicon nitride.

The electrode50includes, for example, at least one metal selected from the group consisting of titanium, tungsten, copper, gold, aluminum, indium, and tin. This is similar for a conductive part61, the pad55, and the wiring parts described below as well.

Operations of the light detector101will now be described.

The incident light that is incident on the upper surface of the light concentrator40from above is concentrated toward the light-receiving element10by the light concentrator40. The incident light that is incident on the upper surface of the light concentrator40passes through the light concentrator40and the insulating layer30and enters the light-receiving element10through the light-receiving surface10f.

For example, the light-receiving element10functions as a p-i-n diode or an avalanche photodiode. A charge is generated in the semiconductor layer22when the light is incident on the light-receiving element10. When the charge is generated, a current flows in the wiring parts and the like (e.g., the conductive part61, a quenching part63, and the first wiring part51described below) that are electrically connected with the first semiconductor region. The incidence of the light on the light-receiving element10can be detected by detecting the current flowing in the wiring parts and the like as an output.

The conductive part61and the electrode50drive the light-receiving element by applying a voltage to the first to fifth semiconductor regions11to15. The voltage can be applied to the light-receiving element10by controlling the potentials of the pad55and the electrode50. For example, a voltage can be applied between the first semiconductor region11and the second semiconductor region12, between the third semiconductor region13and the second semiconductor region12(or the fifth semiconductor region15), and between the third semiconductor region13and the fourth semiconductor region14by controlling the potential of the electrode50. For example, a negative voltage with respect to the pad55is applied to the electrode50. Thereby, a reverse voltage is applied between the first semiconductor region11and the fourth semiconductor region14. A reverse voltage that is greater than the breakdown voltage may be applied to the light-receiving element10(between the first semiconductor region11and the fourth semiconductor region14). In other words, the light-receiving element10may include an avalanche photodiode that operates in a Geiger mode. By operating in a Geiger mode, a pulse signal of a high multiplication factor (i.e., a high gain) is output. The light-receiving sensitivity of the light detector can be increased thereby.

For example, at the vicinity of the p-n junction formed between the first semiconductor region11and the second semiconductor region12of the light-receiving element10, a high electric field region is formed, and a multiplication region is formed in which avalanche amplification of carriers occurs. For example, if there are few crystal defects inside the semiconductor layer22, the charge that is generated inside the light-receiving element10is moved by drifting or diffusing into the multiplication region, and is amplified and detected.

A depletion layer is formed inside the light-receiving element10by the p-n junction. For example, the width in the vertical direction of the depletion layer is increased by the conductive part61and the electrode50applying a reverse voltage to the light-receiving element10.

For example, inside the light-receiving element10, the electric field intensity outside the depletion layer is less than the electric field intensity inside the depletion layer. It is considered that the movement speed of the charge generated inside the light-receiving element10is lower outside the depletion layer than inside the depletion layer. Therefore, for example, there are cases where the time until the charge generated outside the depletion layer moves to the first semiconductor region11side (the multiplication region) and is detected is greater than the time until the charge generated inside the depletion layer moves to the first semiconductor region11side (the multiplication region) and is detected. In other words, it is considered that the time until being detected as a current is different between the positions at which the charges are generated. It is considered that when the charge is generated outside the depletion layer, the time until being detected is long, and a lag component occurs in the detected current value. For example, there is a risk that the time from the photon being incident on the light-receiving element until being detected as a current may fluctuate. For example, when the light detector is used in a time-of-flight lidar device described below, there is a possibility that fluctuation (jitter) of the detection time may affect the ranging accuracy.

The depletion layer spreads from the p-n junction surface between the first semiconductor region11and the second semiconductor region12toward the fourth semiconductor region14. As described above, the first-conductivity-type impurity concentration of the fourth semiconductor region14is relatively high. It is therefore relatively difficult for the depletion layer to spread inside the fourth semiconductor region14. There are cases where the time until the charge generated in the fourth semiconductor region14is detected as a current is relatively long.

In contrast, according to the embodiment, the third semiconductor region13is provided in addition to the p-n junction between the first semiconductor region11and the second semiconductor region12. The responsivity of the detector can be improved thereby. For example, the depletion layer can be extended further toward the fourth semiconductor region14. In other words, the lower end of the depletion layer can be lower. For example, the depletion layer can be easily spread inside the fourth semiconductor region14. For example, the charge that is generated inside the depletion layer can drift due to the electric field of the depletion layer and can reach the first semiconductor region11side (the multiplication region) in a short travel time. For example, fluctuation of the time until the charge generated inside the light-receiving element10is detected as a current can be suppressed.

In the example, the third semiconductor region13contacts the fourth semiconductor region14. Thereby, for example, the depletion layer can be formed lower inside the fourth semiconductor region14. In other words, the depletion layer inside the fourth semiconductor region14can be extended.

The fifth semiconductor region15in which the first-conductivity-type impurity concentration is a minimum is located between the second semiconductor region12and the third semiconductor region13. The fifth semiconductor region15is easily depleted due to the relatively low impurity concentration. Thereby, for example, the depletion layer of the light-receiving element10can be wide in the vertical direction.

For example, the second-conductivity-type impurity concentration of the lower end13dof the third semiconductor region13(equal to the concentration Cx of the example ofFIG.2) is greater than the second-conductivity-type impurity concentration of the upper end13uof the third semiconductor region13(equal to the concentration Cp of the example ofFIG.2). By setting the second-conductivity-type impurity concentration to be high at a deeper position, for example, the depletion layer inside the fourth semiconductor region14can be extended further downward.

As described above with reference toFIG.2, the impurity concentration Cy of the first conductivity type at the boundary between the first semiconductor region11and the second semiconductor region12is greater than the impurity concentration Cx of the first conductivity type at the boundary between the third semiconductor region13and the fourth semiconductor region14. Thereby, for example, the depletion layer is caused to spread from the p-n junction surface between the first semiconductor region11and the second semiconductor region12toward the fourth semiconductor region14. For example, the electric field at the p-n junction surface vicinity between the first semiconductor region11and the second semiconductor region12becomes high, and the charge that is generated inside the light-receiving element10moves easily toward the first semiconductor region11side.

For example, the maximum value of the second-conductivity-type impurity concentration (a concentration C13) of the third semiconductor region13is less than the maximum value of the first-conductivity-type impurity concentration (a concentration C12) of the second semiconductor region12. Thereby, for example, the concentration Cy is easily set to be greater than the concentration Cx.

For example, as illustrated inFIG.1, a lower end Dd of a depletion layer D formed when the light-receiving element10operates is positioned inside the fourth semiconductor region14. An upper end Du of the depletion layer D formed when the light-receiving element10operates is positioned inside the first semiconductor region11. Thus, for example, the depletion layer continuously spreads from the first semiconductor region11to the fourth semiconductor region14. Because the depletion layer is wide, for example, the time until the charge generated inside the light-receiving element10is detected as a current can be shortened.

“When the light-receiving element operates” is the time at which the light-receiving element performs the operation of detecting light in the product including the light detector. For example, when the light-receiving element10operates, a voltage is applied between the first semiconductor region11and the fourth semiconductor region14by applying a prescribed voltage between the electrodes (between the conductive part61and the electrode50). When the light-receiving element10is an avalanche photodiode, the potential difference (the absolute value) between the electrodes is set to a value that is greater than the breakdown voltage. The potential difference may be, for example, a value that is about 5 V greater than the breakdown voltage. Thus, the lower end Dd of the depletion layer D is positioned inside the fourth semiconductor region14when the voltage is applied when operating. For example, the range (the position of the end portion) of the depletion layer can be estimated by a calculation such as a simulation or the like based on the impurity concentration distribution and voltage conditions when operating the light-receiving element. Or, the depletion layer width may be estimated based on the electrical capacitance of the light-receiving element; and the range of the depletion layer may be estimated based on the depletion layer width.

The third semiconductor region13is arranged with the structure part70in the X-axis direction. For example, the incidence of secondary photons and/or the movement of carriers into an adjacent light-receiving element10is suppressed by the structure part70at the vicinity of the depletion layer formed in the third semiconductor region13. For example, the increase of crosstalk noise can be suppressed even when the third semiconductor region13is provided and the depletion layer spreads.

FIG.3is a schematic cross-sectional view illustrating a light detector according to the embodiment.

FIG.3illustrates the light detector102according to the embodiment. In the example, multiple light-receiving elements10, multiple structure parts70, and multiple light concentrators40are arranged in the X-Y plane. The numbers of components are not limited thereto; the number of the light-receiving elements10, the number of the structure parts70, and the number of the light concentrators40each may be one or more. The planar shape of the third semiconductor region13and the thickness of the semiconductor layer22of the light detector102are different from those of the light detector101.

As illustrated inFIG.3, the third semiconductor region13includes multiple portions13aand multiple portions13b. The multiple second semiconductor regions12are located respectively on the multiple portions13a. The multiple first semiconductor regions11are located respectively on the multiple second semiconductor regions12. For example, the portion13ais surrounded with the ring-shaped structure part70. For example, the portion13acontacts the structure part70and the portion15aof the fifth semiconductor region15.

The portion13bis positioned between adjacent portions13a. For example, the portion13bis located at the outer side of the structure part70. For example, the portion13bcontacts the structure part70and the portion15dof the fifth semiconductor region15.

Thus, the third semiconductor region13and the fourth semiconductor region14may extend over the multiple light-receiving elements10. For example, the structure part70extends through the third semiconductor region13and reaches the fourth semiconductor region14. The portion13aand the portion13bof the third semiconductor region13may be partitioned by the structure part70. In other words, the portion13bmay be separated from the portion13a.

FIG.4is a schematic graph illustrating the distributions of the impurity concentrations in the light detector according to the embodiment.

FIG.4illustrates the impurity concentrations at the central portion of the light-receiving element10of the light detector102(the impurity concentrations along a single dot-dash line L2shown inFIG.3). Similarly toFIG.2,FIG.4illustrates the relationship between the impurity concentration C and the position Pz in the Z-axis direction; the first-conductivity-type impurity concentration is shown by a solid line; and the second-conductivity-type impurity concentration is shown by a dotted line. In the example as well, for example, the concentration Cx is greater than the concentration Cp; and the concentration Cy is greater than the concentration Cx.

For example, the thickness T15a(the thickness of the portion15a) of the fifth semiconductor region15between the second semiconductor region12and the third semiconductor region13is greater than the thickness T13of the third semiconductor region13. For example, the thickness of a region of the fifth semiconductor region15in which the first-conductivity-type impurity concentration is constant along the Z-axis direction is greater than the thickness T13of the third semiconductor region13. For example, the width in the vertical direction of the depletion layer can be increased by increasing the thickness of the fifth semiconductor region15that has a relatively low impurity concentration. For example, the sensitivity can be increased by making the fifth semiconductor region15thick.

The thickness T15aof the fifth semiconductor region15may be greater than the thickness T12of the second semiconductor region12and may be greater than the thickness T14of the fourth semiconductor region14. In the example, the thickness T15aof the fifth semiconductor region15is, for example, not less than 0.5 μm and not more than 25 μm.

When the thickness T15aof the fifth semiconductor region15is thick, for example, the third semiconductor region13may be formed by doping a portion of the semiconductor layer22with an impurity when epitaxially growing the semiconductor layer22on the semiconductor layer21.

In the example ofFIG.4, the second-conductivity-type impurity concentration of the third semiconductor region13is high is a region between the upper end13uand the lower end13dof the third semiconductor region13.

FIG.5is a schematic cross-sectional view illustrating a light detector according to the embodiment.

FIG.5illustrates the light detector103according to the embodiment. The thicknesses of the third and fifth semiconductor regions13and15of the light detector103are different from the light detector101.

In the example, the third semiconductor region13contacts the second semiconductor region12. In other words, a portion (the portion15a) of the fifth semiconductor region15may not be located between the second semiconductor region12and the third semiconductor region13.

FIG.6is a schematic graph illustrating the distributions of the impurity concentrations in the light detector according to the embodiment.

FIG.6illustrates the impurity concentrations at the central portion of the light-receiving element10of the light detector103(the impurity concentrations along a single dot-dash line L3shown inFIG.5). Similarly toFIG.2,FIG.6illustrates the relationship between the impurity concentration C and the position Pz in the Z-axis direction; the first-conductivity-type impurity concentration is shown by a solid line; and the second-conductivity-type impurity concentration is shown by a dotted line. In the example as well, for example, the concentration Cy is greater than the concentration Cx.

For example, the concentration Cx is greater than a concentration Cz. The concentration Cz is the first-conductivity-type impurity concentration at the boundary between the second semiconductor region12and the third semiconductor region13. The second-conductivity-type impurity concentration is relatively high at the boundary between the third semiconductor region13and the fourth semiconductor region14that has a high impurity concentration and is not easily depleted. Thereby, for example, the depletion layer inside the fourth semiconductor region14can be extended further downward.

FIG.7is a schematic cross-sectional view illustrating a light detector according to the embodiment.

FIG.7illustrates the light detector104according to the embodiment. The thickness of the fifth semiconductor region15and the location of the third semiconductor region13of the light detector104are different from those of the light detector101. In the example, the third semiconductor region13contacts the second semiconductor region12and is separated from the fourth semiconductor region14.

For example, the fifth semiconductor region15includes a portion15einstead of the portion15a. The portion15eis located between the third semiconductor region13and the fourth semiconductor region14. The portion15econtacts the third and fourth semiconductor regions13and14.

FIG.8is a schematic graph illustrating the distributions of the impurity concentrations in the light detector according to the embodiment.

FIG.8illustrates the impurity concentrations at the central portion of the light-receiving element10of the light detector104(the impurity concentrations along a single dot-dash line L4shown inFIG.7). Similarly toFIG.2,FIG.8illustrates the relationship between the impurity concentration C and the position Pz in the Z-axis direction; the first-conductivity-type impurity concentration is shown by a solid line; and the second-conductivity-type impurity concentration is shown by a dotted line.

As illustrated inFIG.8, the fifth semiconductor region15(the portion15e) in which the first-conductivity-type impurity concentration has a minimum is located between the third semiconductor region13and the fourth semiconductor region14. The fifth semiconductor region15has a low impurity concentration and is depleted relatively easily. For example, the width in the vertical direction of the depletion layer can be increased thereby.

In the example ofFIG.8, a concentration Cw is less than the concentration Cz. The concentration Cw is the first-conductivity-type impurity concentration at the boundary between the third semiconductor region13and the fifth semiconductor region15. The second-conductivity-type impurity concentration of the lower end13dof the third semiconductor region13may be less than the second-conductivity-type impurity concentration of the upper end13u.

For example, a thickness T15eof the fifth semiconductor region15(the thickness of the portion15e) is greater than the thickness T13of the third semiconductor region13. By making the fifth semiconductor region15thick, for example, the sensitivity can be increased. The thickness T15eof the fifth semiconductor region15may be greater than the thickness T12of the second semiconductor region12and may be greater than the thickness T14of the fourth semiconductor region14.

The thicknesses are not limited to those described above; according to the embodiment, the fifth semiconductor region15may include both the portion15abetween the second semiconductor region12and the third semiconductor region13and the portion15ebetween the third semiconductor region13and the fourth semiconductor region14. In other words, the third semiconductor region13may be separated from the second semiconductor region12and may be separated from the fourth semiconductor region14.

FIG.9is a schematic plan view illustrating another light detector according to the embodiment.

The light detector105illustrated inFIG.9includes multiple element structures similar to the structure described with reference toFIG.1, etc. The multiple element structures are arranged in an array configuration along the X-Y plane. For example, the multiple element structures are arranged periodically at a uniform pitch in the X-axis direction and the Y-axis direction. In other words, the light detector105includes the electrode50, the semiconductor layer21, the multiple light-receiving elements10, the multiple structure parts70, the multiple light concentrators40(the microlens array), and the insulating layer30. In the adjacent element structures, the electrodes50are continuous with each other; the semiconductor layers21are continuous with each other; the semiconductor layers22are continuous with each other; and the insulating layers30are continuous with each other.

As shown inFIG.9, the light detector105further includes the multiple first wiring parts51, a common line54, and the pad55(an electrode). One first wiring part51is electrically connected to the multiple light-receiving elements10that are arranged in the Y-axis direction. The multiple first wiring parts51that are arranged in the X-axis direction are electrically connected with the common line54. The common line54is electrically connected with not less than one pad55. A wiring part of an external device is electrically connected to the pad55.

FIG.10is a schematic plan view illustrating a portion of the light detector according to the embodiment.

FIG.11is a schematic cross-sectional view illustrating a portion of the light detector according to the embodiment.

FIG.10illustrates an enlarged region P of the light detector105shown inFIG.9. The light concentrator40and the insulating layer30are not illustrated inFIG.10.FIG.11shows an A4-A5cross section ofFIG.10.

As illustrated inFIG.10, the light-receiving element10includes a photodiode PD. For example, the photodiode PD is formed of the first semiconductor region11, the second semiconductor region12, the third semiconductor region13(the portion13a), the fourth semiconductor region (the portion14a), and the fifth semiconductor region (at least one of the portion15aor the portion15e).

The structure part70surrounds the light-receiving element10(the photodiode PD). In the example, the structure part70is substantially octagonal when viewed along the Z-axis direction. The multiple structure parts70respectively surround the multiple light-receiving elements10along the X-Y plane. For example, the planar shape in the X-Y plane of the structure part70is a polygonal ring shape. The structure part70may be quadrilateral when viewed from the Z-axis direction.

According to the embodiment, “ring-shaped” includes not only when the exterior shape of the planar shape when viewed from above is circular but also when the exterior shape is polygonal. “Polygonal” includes polygonal with curved (rounded) corners. In other words, “polygonal” may be a shape that includes multiple sides (straight lines) and curves connecting the sides to each other. “Ring-shaped” may include not only a continuous ring shape without breaks but also circular or polygonal (e.g., substantially C-shaped) having one or more breaks. For example, the structure part70may discontinuously surround the light-receiving element10when viewed from the Z-axis direction. In other words, when viewed from the Z-axis direction, the structure part70may not have a perfect ring structure and may have a partially open shape.

According to the embodiment, “surround” includes not only the case where an unbroken component continuously surrounds another component, but also the case where multiple components are separated from each other and arranged around the other component. For example, the other component can be considered to be surrounded with the multiple components when the other component is positioned inside a trajectory obtained by tracing along the multiple components. The other component can be considered to be surrounded with a circular shape or a polygon when the other component is positioned inside a circular shape or a polygon having one or more breaks when viewed in plan from above.

The structure part70can suppress the conduction and the optical interference between the adjacent light-receiving elements10. For example, the movement of secondary photons and carriers between the light-receiving elements10is suppressed by the structure part70. When secondary photons are generated by light being incident on the light-receiving element10, the secondary photons that travel toward the adjacent light-receiving elements10are reflected and refracted at the interface of the structure part70. Crosstalk noise can be reduced by providing the structure part70.

The multiple structure parts70are provided independently for each element. In other words, the multiple structure parts70are separated and do not physically contact each other. Compared to when one separation structure is located between the adjacent light-receiving elements10, the number of interfaces of the structure part70between the adjacent light-receiving elements10is increased. By increasing the number of interfaces, when secondary photons are generated in the light-receiving element10, the secondary photons that travel toward the adjacent light-receiving elements10are more easily reflected. Crosstalk noise can be further reduced thereby. An outer perimeter region (the portion15dof the fifth semiconductor region15) is positioned between two mutually-adjacent structure parts70. For example, the outer perimeter region extends in the Y-axis direction between the structure parts70that are adjacent in the X-axis direction. The outer perimeter region extends in the X-axis direction between the structure parts70that are adjacent in the Y-axis direction.

As illustrated inFIG.11, the structure part70may include a first insulating layer IL1and a second insulating layer IL2. The second insulating layer IL2is located between the first insulating layer IL1and the light-receiving element10and between the first insulating layer IL1and the semiconductor layer21. For example, the first insulating layer IL1and the second insulating layer IL2include silicon oxide; and the second insulating layer IL2has a dense structure compared to the first insulating layer IL1.

As illustrated inFIG.11, the fourth semiconductor region14may include a p-type semiconductor region23located between the semiconductor layer21and the structure part70in the Z-axis direction. For example, the p-type impurity concentration of the semiconductor region23is greater than the p-type impurity concentration of the portion14aor the portion14cof the fourth semiconductor region14.

The quenching part63is provided to suppress the continuation of avalanche breakdown when light is incident on the light-receiving element10and avalanche breakdown occurs. When avalanche breakdown occurs and a current flows in the quenching part63, a voltage drop that corresponds to the electrical resistance of the quenching part63occurs. The potential difference between the first semiconductor region11and the second semiconductor region12is reduced by the voltage drop; and the avalanche breakdown stops. The next light that is incident on the light-receiving element10can be detected thereby.

In the example, a quenching resistance is electrically connected to each light-receiving element10as the quenching part63. The resistance of the quenching part63is, for example, not less than 50 kΩ and not more than 6 MΩ. The quenching resistance includes, for example, polysilicon as a semiconductor material. An n-type impurity or a p-type impurity may be added to the quenching resistance.

For example, when viewed from the Z-axis direction, the quenching part63exists at a different position from the photodiode PD. For example, the quenching part63is arranged with the structure part70or the portion15dof the fifth semiconductor region15in the Z-axis direction. The quenching part63is electrically connected with the conductive part61. Thereby, one end of the quenching part63is electrically connected with the first semiconductor region11via the conductive part61. Multiple quenching parts63are included, and the multiple quenching parts63are electrically connected respectively with the multiple first semiconductor regions11. Another end of the quenching part63is electrically connected with the first wiring part51.

The multiple conductive parts61are connected respectively to the multiple light-receiving elements10. Each of the multiple conductive parts61includes the contact64and the interconnect65. The quenching part63is electrically connected with the first semiconductor region11via the contact64and the interconnect65, and is electrically connected with the first wiring part51via a contact66.

The contacts64and66include a metal material. For example, the contacts64and66include at least one selected from the group consisting of titanium, tungsten, copper, and aluminum. The contacts64and66may include a conductor made of a silicon compound or a nitride of at least one selected from the group consisting of titanium, tungsten, copper, and aluminum.

For example, the position in the Z-axis direction of the quenching part63is between the position in the Z-axis direction of the first semiconductor region11and the position in the Z-axis direction of the first wiring part51. One first wiring part51is electrically connected with the multiple photodiodes PD arranged in the Y-axis direction.

The electrical resistance of the quenching part63is greater than the electrical resistances of the contact64, the contact66, and the interconnect65. The quenching resistance includes polysilicon as a semiconductor material. An n-type impurity or a p-type impurity may be added to the quenching resistance.

For example, the insulating layer30includes first to fourth layers31to34. The first to third layers31to33are located between the fourth layer34and the multiple light-receiving elements10in the Z-axis direction. The first layer31and the second layer32are located between the third layer33and the multiple light-receiving elements10in the Z-axis direction. The first layer31is located between the second layer32and the multiple light-receiving elements10in the Z-axis direction.

The contacts64and66are surrounded with the first layer31, the second layer32, and the third layer33along the X-Y plane. A portion of the first layer31is located between the quenching part63and the portion15dof the fifth semiconductor region15in the Z-axis direction. The first wiring part51and the interconnect65are surrounded with the fourth layer34.

FIG.12is a schematic view illustrating an active quenching circuit.

In the light detector according to the embodiments described above, a resistor that generates a large voltage drop is included as the quenching part63. In the light detector according to embodiments, the control circuit and the switching element may be included instead of the resistor. In other words, an active quenching circuit for blocking the current is included as the quenching part63.

As shown inFIG.12, the active quenching circuit includes a control circuit CC and a switching array SWA. The control circuit CC includes a comparator, a control logic part, etc. The switching array SWA includes multiple switching elements SW. For example, at least a portion of the circuit elements included in the control circuit CC and the switching elements SW may be located on the semiconductor layer22or may be located on a circuit board other than the semiconductor layer22.

As shown inFIG.12, one switching element SW may be provided for one light-receiving element10(element region), or one switching element SW may be provided for multiple light-receiving elements10. For example, one switching element SW is located between one first semiconductor region11and the first wiring part51. Or, the switching element SW may be included in the first wiring part51. For example, the switching element SW may be located between the first wiring part51and the pad55.

FIG.13is a schematic view illustrating a lidar (Laser Imaging Detection and Ranging (LIDAR)) device according to the embodiment.

The embodiment is applicable to a long-distance subject detection system (LIDAR) or the like that includes a line light source and a lens. The lidar device5001includes a light-projecting unit T projecting laser light toward an object411, and a light-receiving unit R (also called a light detection system) receiving the laser light from the object411, measuring the time of the round trip of the laser light to and from the object411, and converting the time into a distance.

In the light-projecting unit T, a light source404emits light. For example, the light source404includes a laser light oscillator and produces laser light. A drive circuit403drives the laser light oscillator. An optical system405extracts a portion of the laser light as reference light, and irradiates the rest of the laser light on the object411via a mirror406. A mirror controller402projects the laser light onto the object411by controlling the mirror406. Herein, “project” means to cause the light to strike.

In the light-receiving unit R, a reference light detector409detects the reference light extracted by the optical system405. A light detector410receives the reflected light from the object411. A distance measuring circuit408measures the distance to the object411based on the reference light detected by the reference light detector409and the reflected light detected by the light detector410. An image recognition system407recognizes the object411based on the measurement results of the distance measuring circuit408.

The lidar device5001employs light time-of-flight ranging (Time of Flight) in which the time of the round trip of the laser light to and from the object411is measured and converted into a distance. The lidar device5001is applied to an automotive drive-assist system, remote sensing, etc. Good sensitivity is obtained particularly in the near-infrared region when the light detectors of the embodiments described above are used as the light detector410. Therefore, the lidar device5001is applicable to a light source of a wavelength band that is invisible to humans. For example, the lidar device5001can be used for obstacle detection for a mobile body.

FIG.14describes the detection of the detection object of the lidar device.

A light source3000emits light412toward an object600that is the detection object. A light detector3001detects light413that passes through the object600, is reflected by the object600, or is diffused by the object600.

For example, the light detector3001can realize highly-sensitive detection when the light detector according to the embodiment described above is used. It is favorable to provide multiple sets of the light detector410and the light source404and to preset the arrangement relationship in the software (which is replaceable with a circuit). For example, it is favorable for the arrangement relationship of the sets of the light detector410and the light source404to have uniform spacing. Thereby, an accurate three-dimensional image can be generated by the output signals of each light detector410complementing each other.

FIG.15is a schematic top view of a mobile body that includes the lidar device according to the embodiment.

In the example ofFIG.15, the mobile body is a vehicle. The vehicle700according to the embodiment includes the lidar devices5001at four corners of a vehicle body710. Because the vehicle according to the embodiment includes the lidar devices at the four corners of the vehicle body, the environment in all directions of the vehicle can be detected by the lidar device.

Other than the vehicle illustrated inFIG.15, the mobile body may be a drone, a robot, etc. The robot is, for example, an automated guided vehicle (AGV). By including the lidar devices at the four corners of such mobile bodies, the environment in all directions of the mobile body can be detected by the lidar devices.

According to embodiments, a light detector, a light detection system, a lidar device, and a mobile body can be provided in which the responsivity can be improved.

In the specification of the application, “perpendicular” refers to not only strictly perpendicular but also include, for example, the fluctuation due to manufacturing processes, etc. It is sufficient to be substantially perpendicular.

In this specification, being “electrically connected” includes not only the case of being connected in direct contact, but also the case of being connected via another conductive member, etc.

Embodiments may include the following configurations.

A light detector, comprising:a semiconductor layer of a first conductivity type; anda light-receiving element,the light-receiving element includinga first semiconductor region of a second conductivity type,a second semiconductor region located between the first semiconductor region and the semiconductor layer, the second semiconductor region being of the first conductivity type and contacting the first semiconductor region,a third semiconductor region located between the second semiconductor region and the semiconductor layer, the third semiconductor region being of the second conductivity type, anda fourth semiconductor region located between the third semiconductor region and the semiconductor layer, the fourth semiconductor region being of the first conductivity type and having a lower first-conductivity-type impurity concentration than a first-conductivity-type impurity concentration of the semiconductor layer.

The detector according to Configuration 1, further comprising:a structure part having a different refractive index from the light-receiving element,the third semiconductor region being arranged with the structure part in a direction orthogonal to a first direction,the first direction being from the semiconductor layer toward the light-receiving element.

The detector according to Configuration 1 or 2, whereina first-conductivity-type impurity concentration at a boundary between the first semiconductor region and the second semiconductor region is greater than a first-conductivity-type impurity concentration at a boundary between the third semiconductor region and the fourth semiconductor region.

The detector according to any one of Configurations 1 to 3, whereina maximum value of a second-conductivity-type impurity concentration in the third semiconductor region is less than a maximum value of a first-conductivity-type impurity concentration in the second semiconductor region.

The detector according to any one of Configurations 1 to 4, whereinthe third semiconductor region contacts the fourth semiconductor region.

The detector according to any one of Configurations 1 to 5, whereinthe light-receiving element further includes a fifth semiconductor region located between the second semiconductor region and the third semiconductor region,the fifth semiconductor region is of the first conductivity type, anda first-conductivity-type impurity concentration of the light-receiving element has a minimum in the fifth semiconductor region.

The detector according to Configuration 6, whereina first-conductivity-type impurity concentration at a boundary between the third semiconductor region and the fourth semiconductor region is greater than a first-conductivity-type impurity concentration in the fifth semiconductor region.

The detector according to any one of Configurations 1 to 5, whereinthe third semiconductor region contacts the second semiconductor region,the third semiconductor regions contacts the fourth semiconductor region, anda first-conductivity-type impurity concentration at a boundary between the third semiconductor region and the fourth semiconductor region is greater than a first-conductivity-type impurity concentration at a boundary between the third semiconductor region and the second semiconductor region.

The detector according to any one of Configurations 1 to 4, whereinthe light-receiving element further includes a fifth semiconductor region located between the third semiconductor region and the fourth semiconductor region,the fifth semiconductor region is of the first conductivity type, anda first-conductivity-type impurity concentration of the light-receiving element has a minimum in the fifth semiconductor region.

The detector according to any one of Configurations 1 to 9, whereina thickness of the third semiconductor region is less than a thickness of the second semiconductor region.

The detector according to Configuration 6 or 7, whereina 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.

The detector according to any one of Configurations 1 to 11, whereina depletion layer is formed in a range including a boundary between the first semiconductor region and the second semiconductor region when the light-receiving element operates, andan end portion of the depletion layer is positioned inside the fourth semiconductor region.

The detector according to any one of Configurations 1 to 12, further comprising:a resistor electrically connected with the light-receiving element, or a switching element electrically connected with the light-receiving element.

The detector according to any one of Configurations 1 to 13, whereinthe light-receiving element is a p-i-n diode or an avalanche photodiode.

The detector according to Configuration 14, whereinthe avalanche photodiode operates in a Geiger mode.

A light detection system, comprising:the detector according to any one of Configurations 1 to 15; anda distance measuring circuit calculating a time-of-flight of light based on an output signal of the detector.

A lidar device, comprising:a light source irradiating light on an object; andthe light detection system according to Configuration 16,the light detection system detecting light reflected by the object.

The device according to Configuration 17, further comprising:an image recognition system generating a three-dimensional image based on an arrangement relationship of the light source and the detector.

A mobile body, comprising:the device according to Configuration 17 or 18.

Hereinabove, exemplary embodiments of the invention are described with reference to specific examples. However, the embodiments of the invention are not limited to these specific examples. For example, one skilled in the art may similarly practice the invention by appropriately selecting specific configurations of components included in light detectors such as semiconductor layers, light-receiving elements, etc., from known art. Such practice is included in the scope of the invention to the extent that similar effects thereto are obtained.

Moreover, all light detectors, light detection systems, lidar devices and mobile bodies practicable by an appropriate design modification by one skilled in the art based on the light detectors, the light detection systems, the lidar devices and the mobile bodies described above as embodiments of the invention also are within the scope of the invention to the extent that the purport of the invention is included.