CN114759052A

CN114759052A - Photodetector unit, operating method thereof, electronic device and pixel unit

Info

Publication number: CN114759052A
Application number: CN202210400072.XA
Authority: CN
Inventors: 潘立阳; 孙科阳; 王喆垚
Original assignee: Tsinghua University
Current assignee: Tsinghua University
Priority date: 2022-04-15
Filing date: 2022-04-15
Publication date: 2022-07-15

Abstract

A photodetector unit, a method of operating the same, and an electronic device and a pixel unit including the photodetector unit. The light detector unit comprises a control circuit and a light sensing device coupled with the control circuit; the photosensitive device includes: a semiconductor substrate including a main surface; a gate insulating layer disposed on the main surface; a main gate, a first side gate, and a second side gate adjacently disposed on the gate insulating layer; and a first electrode, a second electrode, a third electrode, and a fourth electrode disposed on the main surface. The photodetector unit further includes a first selection transistor, a second selection transistor, and a reset transistor, and source and drain electrodes of these transistors are electrically connected to a corresponding one of the plurality of electrodes of the light sensing device, respectively. The light detector unit can quickly enter a light sensing mode and can realize quick switching between a plurality of sensing modes.

Description

Photodetector unit, operating method thereof, electronic device and pixel unit

Technical Field

Embodiments of the present disclosure relate to a light detector unit, a method of operating the same, and an electronic device including the light detector unit.

Background

In the field of light detection, existing photodetectors include photodiode-based detectors, Avalanche Photodiode (APD) based detectors, and phototransistor-based detectors. Photodiode-based detectors, such as Complementary Metal Oxide Semiconductor (CMOS) sensors, present significant challenges in the field of light detection due to the low quantum efficiency of photodiode detectors for light detection. APDs can achieve high sensitivity due to the internal gain due to avalanche breakdown. The operating voltage of the APD is high and a quenching circuit is required. Due to the restriction of factors such as circuit complexity, noise and power consumption, the difficulty in realizing the APD imaging array is high. The operating voltage of the phototriode is low and no avalanche noise is introduced compared to APDs. However, the current gain of the phototriode is affected by the operating point, and the current gain obtained when the light intensity is small is very limited.

In addition, the difference between the strongest illumination and the weakest illumination which can be seen in nature is very large, the difference of the illumination values of the scene from the strongest to the weakest reaches more than 8 orders of magnitude, and the dynamic range is converted to exceed 160 dB. The dynamic range of a common image sensor is usually only 70-80dB, which is a big difference compared with a natural scene. The instantaneous dynamic range of the human eye exceeds 100dB and the dynamic range through the adaptation process can approach or exceed that of natural scenes. Therefore, in general, a picture taken by a digital device is obviously different from a scene actually seen by a person, and characteristics such as adaptive adjustment of human eyes are far better than those of an electronic image sensor. Moreover, wide dynamic range imaging can provide more details and light-dark contrast than the traditional imaging result, and has wide requirements in the fields of automobile safety, industrial manufacturing, aerospace, astronomical research and the like.

Disclosure of Invention

At least one embodiment of the present disclosure provides a photodetector unit that includes a control circuit and a photosensitive device coupled to the control circuit. The light detector unit can quickly enter a light sensing mode and can realize quick switching between a plurality of sensing modes.

For example, in a photodetector cell provided by at least one embodiment of the present disclosure, the photosensitive device includes a semiconductor substrate including a main surface, the main surface includes a first region and a second region disposed adjacent to each other and having different doping types, a third region and a fifth region formed in the first region, and a fourth region and a sixth region formed in the second region, wherein the third region has the same doping type as the second region and has a first interval with the second region, the fourth region has the same doping type as the first region and has a second interval with the first region, the fifth region has the same doping type as the first region and is on a side of the third region facing away from the second region, the sixth region has the same doping type as the second region and is on a side of the fourth region facing away from the first region, and the first interval and the second interval form a channel region of a thyristor. The photosensitive device further includes a gate insulating layer disposed on the main surface. The photosensitive device further includes a main gate, a first side gate and a second side gate adjacently disposed on the gate insulating layer, wherein the main gate is at least partially disposed corresponding to the channel region in a direction perpendicular to the main surface, the first side gate is at least partially disposed corresponding to the first space in the direction perpendicular to the main surface and insulated from the main gate, and the second side gate is at least partially disposed corresponding to the second space in the direction perpendicular to the main surface and insulated from the main gate. The photosensitive device further includes a first electrode disposed on the main surface and in electrical contact with the third region, a second electrode disposed on the main surface and in electrical contact with the fourth region, a third electrode disposed on the main surface and corresponding to the fifth region in a direction perpendicular to the main surface, and a fourth electrode disposed on the main surface and corresponding to the fourth electrode of the sixth region in a direction perpendicular to the main surface.

For example, in a photodetector unit provided in at least one embodiment of the present disclosure, the light sensing device further includes: a first sidewall insulating layer insulating the main gate from the first sidewall gate; a second side wall insulating layer arranged on the main surface and adjacent to the first side grid, wherein the first side wall insulating layer at least partially covers the side surface of the first side grid adjacent to the second side wall insulating layer; a third sidewall insulating layer insulating the main gate from the second sidewall gate; and a fourth sidewall insulating layer disposed on the main surface and adjacent to the second side gate, and the third sidewall insulating layer at least partially covers a side surface of the second side gate adjacent to the fourth sidewall insulating layer.

For example, in a photodetector unit provided in at least one embodiment of the present disclosure, the light sensing device further includes: a first trench isolation region located in the first region and separating the third region and the fifth region by the first trench isolation region; and a second trench isolation region located in the second region and separating the fourth region and the sixth region from each other through the second trench isolation region.

For example, in the photodetector unit provided by at least one embodiment of the present disclosure, in the photosensitive device, the doping concentrations of the fourth region and the fifth region are respectively greater than the doping concentration of the first region; the doping concentration of the third region and the doping concentration of the sixth region are respectively greater than that of the second region.

For example, in the photodetector unit provided in at least one embodiment of the present disclosure, in the photosensitive device, the first region, the fourth region, and the fifth region are P-type doped regions; the second region, the third region and the sixth region are N-type doped regions.

For example, in a photodetector cell provided in at least one embodiment of the present disclosure, the control circuit includes a first selection transistor and a second selection transistor. The first source drain electrode of the first selection transistor is electrically connected with the first electrode of the photosensitive device, and the second source drain electrode of the first selection transistor is electrically connected with the third electrode of the photosensitive device; and a first source drain electrode of the second selection transistor is electrically connected with a second electrode of the photosensitive device, and a second source drain electrode of the second selection transistor is electrically connected with a fourth electrode of the photosensitive device.

For example, in a photodetector cell provided by at least one embodiment of the present disclosure, the control circuit further includes a reset transistor. The first source drain electrode of the reset transistor is electrically connected with the second electrode of the photosensitive device and the first source drain electrode of the second selection transistor, and the second source drain electrode of the reset transistor is configured to be electrically connected with the first power supply voltage end.

For example, in the photodetector unit provided in at least one embodiment of the present disclosure, the first source-drain electrode of the first selection transistor is electrically connected to the first electrode and is further configured to be electrically connected to the second power supply voltage terminal.

For example, in a photodetector unit provided in at least one embodiment of the present disclosure, the main gate, the first side gate, and the second side gate of the light sensing device are configured to respective specific levels.

At least one embodiment of the present disclosure provides a method of operating any of the above-described photodetector units. The method comprises the following steps: the first electrode and the third electrode of the photosensitive device are in short circuit, the second electrode and the fourth electrode of the photosensitive device are in short circuit, and the second electrode and the fourth electrode are suspended; and disconnecting the first electrode and the third electrode of the photosensitive device from the short circuit, and disconnecting the second electrode and the fourth electrode of the photosensitive device from the short circuit, so that the photosensitive device enters a first light detection mode.

For example, in an operation method provided in at least one embodiment of the present disclosure, controlling the photosensitive device to perform the light detection includes: and applying a control voltage to the first side grid electrode of the photosensitive device so that the photosensitive device is started in the process of light incidence.

For example, in an operation method provided in at least one embodiment of the present disclosure, controlling the photosensitive device to perform the light detection further includes: the moment when the photosensitive device is turned on during the incident of light is recorded.

For example, in an operation method provided in at least one embodiment of the present disclosure, before shorting the second electrode to the fourth electrode and suspending the second electrode and the fourth electrode, the method further includes: the second electrode and the fourth electrode are shorted and connected to a first power supply voltage to perform reset.

For example, in another operation method provided in at least one embodiment of the present disclosure, the operating the control circuit to select the light detection mode of the light sensing device includes: and the first electrode is in short circuit with the third electrode, the second electrode is in short circuit with the fourth electrode, and the second electrode and the fourth electrode are suspended, so that the photosensitive device enters a second optical detection mode.

For example, in another operation method provided by at least one embodiment of the present disclosure, the operating the control circuit to select a light detection mode of the light sensing device includes: and disconnecting the first electrode from the third electrode, short-circuiting the second electrode with the fourth electrode, and suspending the second electrode and the fourth electrode so that the photosensitive device enters a third light detection mode.

At least one embodiment of the present disclosure also provides an electronic device including any one of the above-described photodetector units.

At least one embodiment of the present disclosure also provides a pixel unit including any one of the above-mentioned photodetector units.

For example, at least one embodiment of the present disclosure provides a pixel unit further including a sampling unit, wherein the sampling unit samples the light sensing signal received from the light detector unit.

Drawings

To more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings of the embodiments will be briefly introduced below, and it is apparent that the drawings in the following description only relate to some embodiments of the present disclosure and do not limit the present disclosure.

FIG. 1A shows a simplified schematic of the structure of a typical thyristor;

FIG. 1B shows a schematic diagram of a current-voltage characteristic curve and corresponding states of the thyristor of FIG. 1A;

FIG. 2 illustrates a schematic structural view of a photosensitive device according to at least one embodiment of the present disclosure;

FIG. 3 illustrates a schematic circuit diagram of a photodetector cell including the photo-sensing device of FIG. 2 in accordance with at least one embodiment of the present disclosure;

fig. 4A and 4B illustrate schematic diagrams of the operating principle of a photodetector unit according to at least one embodiment of the present disclosure;

FIG. 5 illustrates a graph of the timing of turn-on of a photosensitive device in a photodetector cell in accordance with at least one embodiment of the present disclosure versus incident optical power density;

FIG. 6A illustrates a workflow diagram of a sampling unit and a photodetector unit in accordance with at least one embodiment of the present disclosure;

fig. 6B illustrates a circuit configuration schematic of a pixel cell according to at least one embodiment of the present disclosure;

fig. 7A illustrates signal readout paths of linear and logarithmic sampling patterns of a sampling cell in accordance with at least one embodiment of the present disclosure; and

fig. 7B shows incident optical power density versus output voltage for the two signal readout paths in fig. 7A.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present disclosure more apparent, the technical solutions of the embodiments of the present disclosure will be described clearly and completely with reference to the drawings of the embodiments of the present disclosure. It is to be understood that the described embodiments are only a few embodiments of the present disclosure, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the described embodiments of the disclosure without any inventive step, are within the scope of protection of the disclosure.

Unless otherwise defined, technical or scientific terms used herein shall have the ordinary meaning as understood by one of ordinary skill in the art to which this disclosure belongs. The use of "first," "second," and the like in this disclosure is not intended to indicate any order, quantity, or importance, but rather is used to distinguish one element from another. The word "comprising" or "comprises", and the like, means that the element or item listed before the word covers the element or item listed after the word and its equivalents, but does not exclude other elements or items. The terms "connected" or "coupled" and the like are not restricted to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "upper", "lower", "left", "right", and the like are used merely to indicate relative positional relationships, and when the absolute position of the object being described is changed, the relative positional relationships may also be changed accordingly.

The present disclosure is illustrated by the following specific examples. Detailed descriptions of known functions and known components may be omitted in order to keep the following description of the embodiments of the present disclosure clear and concise. When any component of an embodiment of the present disclosure appears in more than one drawing, that component is represented by the same or similar reference numeral in each drawing.

Generally, an image sensor is intended to obtain as large a dynamic range as possible, for which on the one hand the lowest light intensity that can be detected by the pixel cell is optimized and on the other hand the highest light intensity that can be detected by the pixel cell is increased. In recent years, the dynamic range of image sensors is expanded, and much attention is paid to the improvement of the highest detectable light intensity. The minimum detectable light intensity is directly related to the amplification characteristics of the device and the noise level of the system. In the current research on improving the dynamic range of the image sensor, a solution for expanding the lowest light intensity of the pixel and improving the highest light intensity of the pixel is needed.

A Thyristor (Thyristor) is a semiconductor device having a four-layer PNPN structure, and by virtue of its small dark current in the off-state, the Thyristor is considered as a potential light-sensing device and is increasingly focused on application in photodetectors.

Fig. 1A shows a simplified schematic of the structure of a typical thyristor. Fig. 1B shows a schematic diagram of the current-voltage (I-V) characteristic curve and the corresponding state of the thyristor of fig. 1A.

Fig. 1A shows a four-layer PNPN structure of a thyristor, with junctions J1, J2, J3 between pairs of adjacent NP layers, respectively, and cathodes and anodes respectively connected to the N + layer and the P + layer on both sides. As shown in fig. 1B, when a forward voltage is applied across the anode and cathode of the thyristor of fig. 1A (i.e., a positive potential on the anode of the thyristor), the thyristor of fig. 1A may have four states: an off state (state I), a feedback amplified state (state II), a negative resistance state (state III), and an on state (state IV), wherein the off state and the on state are stable states.

When the thyristor is in the off state, the emitter junctions J1 and J3 on both sides in fig. 1A are forward biased, the junction J2 in the middle is reverse biased, and the voltage applied at the anode falls almost entirely on the junction J2 in the middle, so the current is smaller in this state. When the thyristor is in the on-state, i.e., corresponding to the low voltage and low resistance segments of the forward portion of the I-V characteristic shown in fig. 1B, junctions J1, J3 and the middle junction J2 in fig. 1A are all biased forward. Since the thyristor can realize the mutual conversion between the off-state and the on-state through the optical signal, in the field of photoelectric detection, the thyristor is generally used as an optical switch, and the characteristic that the dark current in the off-state is small is utilized for photoelectric detection. However, thyristors in the off state have poor sensitivity to light and are difficult to switch quickly to the on state.

In addition, the negative resistance state of the thyristor between the off-state and the on-state is an unstable transition. The transition point between the off-state and the negative resistance state is a switching point, and in the feedback amplification state near the switching point, the thyristor having the PNPN structure can be abstractly understood as two transistors coupled to each other. When the applied forward voltage rises, the positive feedback function between the two triodes is gradually enhanced, so that the amplification effect of the thyristor on external signals is also enhanced continuously, and the thyristor working near a switch point has strong sensitivity to external physical signals such as light, temperature and the like. However, considering the unstable negative resistance state of the thyristor in the static characteristic and the bias inconsistency caused by the factors of the process, the temperature and the like, the thyristor in the conventional sense cannot be biased to the reset induction mode near the switch point quickly for photoelectric detection.

To address the above issues, at least one embodiment of the present disclosure provides a photodetector unit including a control circuit and a photosensitive device coupled to the control circuit, the photosensitive device including a thyristor, the control circuit being configured to control an operation of the photosensitive device. In at least some embodiments of the present disclosure, the photodetector unit can enter the light sensing mode quickly (e.g., perform dim light sensing), can enable fast switching between multiple sensing modes, and further can enable a wide dynamic range under multi-mode conditions.

In a photodetector cell provided by at least one embodiment of the present disclosure, a photosensitive device coupled to a control circuit includes a semiconductor substrate including a major surface, the major surface including first and second regions disposed adjacent to each other and having different doping types, third and fifth regions formed in the first region, and fourth and sixth regions formed in the second region, wherein the third and second regions have the same doping type and a first spacing from the second region, the fourth and first regions have the same doping type and a second spacing from the first region, the fifth and first regions have the same doping type and are on a side of the third region facing away from the second region, the sixth region has the same doping type as the second region and is on a side of the fourth region facing away from the first region, and the first and second spacings form a channel region of a thyristor.

The photosensitive device further includes a gate insulating layer disposed on the main surface.

The photosensitive device further includes a main gate, a first side gate and a second side gate adjacently disposed on the gate insulating layer, wherein the main gate is at least partially disposed corresponding to the channel region in a direction perpendicular to the main surface, the first side gate is at least partially disposed corresponding to the first space in the direction perpendicular to the main surface and insulated from the main gate, and the second side gate is at least partially disposed corresponding to the second space in the direction perpendicular to the main surface and insulated from the main gate.

The photosensitive device further includes a first electrode disposed on the main surface and in electrical contact with the third region, a second electrode disposed on the main surface and in electrical contact with the fourth region, a third electrode disposed on the main surface and corresponding to the fifth region in a direction perpendicular to the main surface, and a fourth electrode disposed on the main surface and corresponding to the fourth electrode of the sixth region in a direction perpendicular to the main surface.

Any embodiment of the present disclosure also provides an operating method of the above-mentioned light detector unit, so as to detect incident light. Any embodiment of the present disclosure also provides a pixel unit or an electronic device including the above-described photodetector unit.

Some embodiments of the disclosure are described in detail below with reference to the accompanying drawings.

Fig. 2 illustrates a schematic diagram of a structure 100 of a photosensitive device according to at least one embodiment of the present disclosure.

As shown in fig. 2, photosensitive device 100 can include a semiconductor substrate including a major surface 101, for example, a silicon substrate, such as a pure monocrystalline silicon substrate or a doped monocrystalline silicon substrate. The main surface 101 may comprise a first region 102 and a second region 103 arranged adjacently and having different doping types, wherein the first region 102 has a third region 104 and a fifth region 106 formed therein and the second region 103 has a fourth region 105 and a sixth region 107 formed therein. As shown in FIG. 2, the third region 104 has a first spacing d from the second region 103₁The fourth region 105 has a second spacing d from the first region 102₂A fifth zone 106 on the side 103 of the third zone 104 facing away from the second zone, a sixth zone 107 on the side of the fourth zone 206 facing away from the first zone 102, and a first spacing d₁At a second spacing d from₂Together forming the channel region of the thyristor.

For example, in some embodiments, the first region 102, the fourth region 105, and the fifth region 106 may have the same doping type; correspondingly, the second region 103, the third region 104 and the sixth region 107 may have the same further doping type. For example, the doping types of the first region 102, the fourth region 105, and the fifth region 106 may be N-type (e.g., doping phosphorus (P) or arsenic (As)), and the doping types of the second region 103, the third region 104, and the sixth region 107 are P-type (e.g., doping boron (B)), where the photosensitive device 100 is a P-type photosensitive device; alternatively, the doping type of the first region 102, the fourth region 105 and the fifth region 106 may be P-type, and the doping type of the second region 103, the third region 104 and the sixth region 107 is N-type, in which case the photosensitive device 100 is an N-type photosensitive device. The present disclosure does not limit the arrangement of the above doping types.

For example, in some embodiments, the doping concentration of the fourth region 105 and the fifth region 106 may be respectively greater than the doping concentration of the first region 102, for example, the fourth region 105 may be a heavily doped region having a doping concentration greater than the doping concentration of the first region 102. In still other embodiments, the doping concentration of the third region 104 and the sixth region 107 may be respectively greater than the doping concentration of the second region 103, for example, the third region 104 may be a heavily doped region having a doping concentration greater than the doping concentration of the second region 103.

For example, in some embodiments, the main surface 101 may include a first trench isolation region 131 in the first region 102 and a second trench isolation region 132 in the second region 103, wherein the third region 104 and the fifth region 106 are separated by the first trench isolation region 131, and the fourth region 105 and the sixth region 107 are separated by the second trench isolation region 132. However, in other embodiments, the first trench isolation region 131 and the second trench isolation region 132 shown in fig. 2 may not be included in the main surface 101.

As shown in fig. 2, the light sensing device 100 may further include a gate insulating layer 111 disposed on the main surface 101, and a main gate 112, a first side gate 117, and a second side gate 114 adjacently disposed on the gate insulating layer 111 and insulated from each other. The gate insulating layer 111 may be, for example, silicon oxide, silicon nitride, silicon oxynitride, or the like. The main gate 112 may be disposed at least partially corresponding to the channel region in a direction perpendicular to the main surface 101, and the first side gate 117 may be disposed at least partially corresponding to the first interval d in the direction perpendicular to the main surface 101₁In this arrangement, the second side gate 114 may at least partially correspond to the second spacing d in a direction perpendicular to the main surface₂And (4) setting. Thereby, the main gate 112, the first side gate 117, and the second side gate 114 correspond to the channel region as a whole, and the conductive state of the channel region may be controlled by applying voltage signals to the main gate 112, the first side gate 117, and the second side gate 114, respectively. For example, the main gate 112, the first side gate 117, and the second side gate 114 may be polysilicon electrodes, metalized electrodes (e.g., tungsten silicide), or metal electrodes, etc.

For example, in some embodiments, the photosensitive device 100 may further include a first sidewall insulating layer 116 to insulate the main gate 112 from the first sidewall gate 117. The light sensing device 100 may include a third sidewall insulating layer 113 to insulate the main gate 112 from the second sidewall gate 114.

In addition, in some embodiments, the photosensitive device 100 may further include a second sidewall insulating layer 118 disposed on the main surface 101 and adjacent to the first sidewall insulating layer 117, and a side of the first sidewall insulating layer 117 adjacent to the second sidewall insulating layer 118 is at least partially covered by the first sidewall insulating layer 116. The photosensitive device 100 may further include a fourth sidewall insulating layer 115 disposed on the main surface 101 and adjacent to the second side gate 114, and a side of the second side gate 114 adjacent to the fourth sidewall insulating layer 115 is at least partially covered with the third sidewall insulating layer 113.

As shown in fig. 2, the photosensitive device 100 may further include a first electrode 121, a second electrode 122, a third electrode 123, and a fourth electrode 124 disposed on the main surface 101. In some embodiments, the first electrode 121 may be in direct or indirect electrical contact with the third region 104, the second electrode 122 may be in direct or indirect electrical contact with the fourth region 105, the third electrode 123 may correspond to the fifth region 106 in a direction perpendicular to the main surface 101, and be in direct or indirect electrical contact with the fifth region 106; the fourth electrode 124 may correspond to the sixth region 107 in a direction perpendicular to the main surface 101, in direct or indirect electrical contact with the sixth region 107. The first electrode 121, the second electrode 122, the third electrode 123, and the fourth electrode 124 may be, for example, a polysilicon electrode, a metalized electrode (e.g., tungsten silicide), a metal electrode, or the like.

In another example of this embodiment, the semiconductor substrate may further include a semiconductor base, for example, the first region 102 in fig. 2 or the like may be formed on the semiconductor base, in which case the first region 102 is a well region formed on the base, and the second region 103 is a well region formed on the base or a well region formed in the first region 102 or the like. For example, the semiconductor substrate has the same doping type as the first region 102, e.g., the doping concentration is less than that of the first region 102.

The photosensitive device has strong control capability on the current carrier of the channel region, thereby having the capability of fast switching on and switching off. A photodetector unit including a photosensitive device (e.g., the photosensitive device 100 of fig. 2) having the above-described structural features will be described in detail below with reference to fig. 3.

Fig. 3 illustrates a schematic circuit structure diagram of a photodetector cell 200 including the photo-sensing device 100 of fig. 2 according to at least one embodiment of the present disclosure.

As shown in fig. 3, the photodetector unit 200 may include the photosensitive device 100 of fig. 2. In some embodiments, the light detector unit 200 may further comprise a control circuit, and the light sensing device 100 is coupled to the control circuit. The control circuit is configured to control the operation of the light-sensing device 100, including the establishment of the operating state and the switching of the operating mode of the light-sensing device 100, according to one or more control signals.

As shown in fig. 3, the control circuit of the photodetector cell 200 may include a first switching element, such as a first selection transistor M1, wherein a first source-drain of the first selection transistor M1 may be configured to be electrically connected to the first electrode 121 of the light sensing device 100, and a second source-drain of the first selection transistor M1 may be configured to be electrically connected to the third electrode 123 of the light sensing device 100. In some embodiments, the first source-drain of the first selection transistor M1 and the first electrode 121 of the light sensing device 100 may also be configured to be electrically connected with a second power supply voltage terminal VSS, wherein the first electrode 121 of the light sensing device 100 is electrically connected with the second power supply voltage terminal VSS, so that the light sensing device 100 can convert a received optical signal into an electrical signal. In some embodiments, the first selection transistor M1 may be an N-type transistor, such as an NMOS transistor.

As shown in fig. 3, the control circuit of the photo-detector unit 200 may further include a second switching element, such as a second selection transistor M2, wherein a first source-drain electrode of the second selection transistor M2 is configured to be electrically connected to the second electrode 122 of the light-sensing device 100, and a second source-drain electrode of the second selection transistor M2 is configured to be electrically connected to the fourth electrode 124 of the light-sensing device 100. In some embodiments, the second selection transistor M2 may be a P-type transistor, such as a PMOS transistor.

As shown in fig. 3, the control circuit of the light detector unit 200 may further include a third switching element, such as a reset transistor M3, wherein a first source-drain electrode of the reset transistor M3 is configured to be electrically connected to the second electrode 122 of the light sensing device 100 and the first source-drain electrode of the second selection transistor M2, and a second source-drain electrode of the reset transistor M3 is configured to be electrically connected to the first power supply voltage terminal VDD. In some embodiments, the reset transistor M3 may be a P-type transistor, such as a PMOS transistor. For example, the voltage of the first power supply voltage terminal VDD is higher than the second power supply voltage terminal VSS; for example, the first power voltage terminal VDD is 3V, and the second power voltage terminal VSS is a ground terminal.

According to at least one embodiment of the present disclosure, the first selection transistor M1 and the second selection transistor M2 as shown above may be used to control the operation mode of the light sensing device 100, for example, to establish or cancel the light detection mode of the light detector cell 200. Specifically, the gate of the first selection transistor M1 may be connected to a corresponding signal line to receive the light mode setting signal SEL1, and the gate of the second selection transistor M2 may be connected to a corresponding signal line to receive the light mode setting signal SEL 2. The reset transistor M3 as shown above may be used for the reset operation of the light sensing device 100. Specifically, the gate of the reset transistor M3 may be connected to a corresponding signal line to receive the reset signal RST.

As shown in FIG. 3, in the photo-detector unit 200, the main gate 112 of the photo-sensing device 100 may receive the voltage signal V_GThe first side gate 117 can receive a voltage signal V_G1The second side gate 114 can receive a voltage signal V_G2. In some embodiments, the main gate 112, the first side gate 117, and the second side gate 114 may be configured to respective specific levels. For example, the voltage signal V to which the main gate 112 is connected_GMay be configured to the level of the first power supply voltage terminal VDD of 1/2, the voltage signal V to which the first side gate 117 is connected_G1Can be configured to the level of the first power supply voltage terminal VDD and the voltage signal V to which the second side gate 114 is connected_G2May be configured to 0.6V.

The following will explain in detail an operation method and an operation principle of the light detector unit provided by at least one embodiment of the present disclosure with reference to fig. 4A and 4B and further with reference to fig. 2 and 3.

Fig. 4A and 4B illustrate schematic diagrams of the operating principle of a photodetector unit according to at least one embodiment of the present disclosure.

As shown in fig. 4A, fig. 4A shows that the photodetector unit may include a reset mode and a sensing mode in operation, wherein during the sensing mode, a state I ', a state II ', and a state IV ' may be further included. The reset mode, state I ', state II', and state IV 'shown in fig. 4A correspond to the reset mode, state I', state II ', and state IV' in fig. 4B, respectively. For example, in some embodiments, when a photodetector cell is in a reset mode, it is indicated that the photodetector cell is in an off state, and the photodetector cell may be reset to an initial state; when the light detector unit is in the state I', the light detector unit is in a super-off state; when the light detector unit is in the state II', the light detector unit is in a feedback amplification state; when the photo detector unit is in state IV', which indicates that the photo detector unit is in an on-state, these states and the transitions between them will be further described below.

Next, the photosensitive device is an N-type photosensitive device, the first selection transistor M1 is an NMOS transistor, the second selection transistor M2 is a PMOS transistor, and the reset transistor M3 is a PMOS transistor. As shown in fig. 4A, when the reset signal RST is set low, the mode setting signal SEL1 is set high, and the mode setting signal SEL2 is set low, the photosensitive device is in a reset mode, which may include a reset state and a diode state, for example. Specifically, referring to fig. 4A, when the reset signal RST is set low, the mode setting signal SEL1 is set high, and the mode setting signal SEL2 is set low, the photosensitive device is in a reset mode, resetting the photosensitive element to an initial state by applying the first power voltage VDD to the second electrode 122 and the fourth electrode for a subsequent duty cycle; thereafter, for example, when the reset signal RST is set high, the mode setting signal SEL1 is set high, and the mode setting signal SEL2 is set low, the light sensing device is in a diode state and thus can be used for sensing light. The photosensitive device may enter a sensing mode (i.e., a photo detection mode) when the reset signal RST is asserted high, the mode set signal SEL1 is asserted low, and the mode set signal SEL2 is asserted high.

For example, in conjunction with the photodetector cell 200 shown in FIG. 3, V in FIG. 4A_npRefers to the PN junction voltage, V, formed in the photo-sensing device 100_aRefers to the end of the second electrodePressure, V_p-baseRefers to the terminal voltage of the third electrode, and V_n-baseRefers to the terminal voltage of the fourth electrode. When the reset signal RST is set low, the reset transistor M3 is turned on. The mode set signal SEL1 is asserted high and the mode set signal SEL2 is asserted low to keep the first and second select transistors M1 and M2 turned on, thereby switching on at V_np＝V_aThe photosensitive device 100 is brought into a reset state in a reset mode; on this basis, the reset signal RST can then be set high and the photosensitive device 100 can enter a diode state in the reset mode.

When the reset signal RST is set high, the reset transistor M3 is turned off. The mode setting signal SEL1 is set low and the mode setting signal SEL2 is set high to keep the first and second selection transistors M1 and M2 off so that the light sensing device 100 can enter a light sensing mode, where V is at the beginning of the reset transistor M3 being off and the mode setting signal SEL1 being set low and the mode setting signal SEL2 being set high, i.e., the light detector cell is in a super-OFF state_np>V_a(ii) a And when the light sensing device 100 enters the light detection mode with the first selection transistor M1 and the second selection transistor M2 kept turned off, V at this time_np≈V_a。

Specifically, when the light sensing device 100 in fig. 3 (i.e., the light sensing device 100 of fig. 2) is an N-type light sensing device, the first selection transistor M1 is an N-type transistor, the second selection transistor M2 is a P-type transistor, and the reset transistor M3 is a P-type transistor, the first selection transistor M1 and the second selection transistor M2 may be kept turned on while the mode setting signal SEL1 is set high and the mode setting signal SEL2 is set low. In this case, the first electrode 121 and the third electrode 123 of the light sensing device 100 are short-circuited and connected to a low potential, and the second electrode 122 and the fourth electrode 124 of the light sensing device 100 are short-circuited and connected to a high potential, for example, the second electrode 122 and the fourth electrode 124 of the light sensing device 100 are suspended, and at this time, the light sensing device 100 may be regarded as a reverse biased PN junction, so that the light sensing device 100 may be operated as a general photodiode to perform light sensing.

In some embodiments, before the second electrode 122 of the photosensitive device 100 is shorted with the fourth electrode 124 and the second electrode 122 and the fourth electrode 124 are floated, as described above, the photosensitive device 100 may be reset by shorting the second electrode 122 of the photosensitive device 100 with the fourth electrode 124 and connecting the second electrode 122 and the fourth electrode 124 with a first power supply voltage (e.g., the first power supply voltage terminal VDD shown in fig. 3).

The first and second selection transistors M1 and M2 may be kept off while the mode setting signal SEL1 is set low and the mode setting signal SEL2 is set high. In this case, the first electrode 121 and the third electrode 123 of the photosensitive device 100 are disconnected from the short, and the second electrode 122 and the fourth electrode 124 of the photosensitive device 100 are disconnected from the short, since the parasitic capacitance at the second electrode 122 of the photosensitive device 100 may be larger than that at the fourth electrode 124 because, for example, an induced capacitance is added at the second electrode 122, the potential of the second region 103 (shown in fig. 2) of the photosensitive device 100 is larger than that of the fourth region 105 according to a capacitive bootstrap effect, so that the potential of the second region 103 and the fourth region 105 formed between the second region 103 and the fourth region 105 keeps being reversely biased, thereby bringing the photosensitive device 100 into a super off state (state I' shown in fig. 4A and 4B). At this time, the light sensing device 100 may enter a light detection mode, i.e., a sensing mode as shown in fig. 4A.

For example, in some embodiments, applying a control voltage to at least one gate of the photosensitive device 100, e.g., the first side gate 117, during the photosensitive device 100 entering the light detection mode, may cause the photosensitive device 100 to turn on during the light incidence.

Specifically, for example, when a suitable positive voltage is applied to the first side gate 117 of the photosensitive device 100 as a control voltage, minority carrier electrons in the first region 101 of the photosensitive device 100 accumulate in the main surface 101 under the first sidewall insulating layer 116 and form an inversion layer, thereby forming a pull-down current from the first region 102 to the first electrode 121, so that the PN junction formed between the first region 102 and the fourth region 105 described above changes from reverse bias to forward bias. At this time, the photosensitive device 100 may enter a feedback amplification state (state II 'shown in fig. 4A and 4B), and after a period of time, the photosensitive device 100 enters an on state (state IV' shown in fig. 4A and 4B).

When the photodetector unit 200 detects light, that is, when light is incident on the photosensitive device 100, referring to the photosensitive device 100 shown in fig. 2, photo-generated carriers may be generated at a reverse biased PN junction between the first region 102 and the second region 103 of the photosensitive device 100, where holes may drift into the first region 102 under the action of an electric field and be blocked by a barrier of an emitter junction (i.e., a PN junction between the first region 102 and the second region 103), so that a portion of the holes are trapped in the first region 102 and form an excess positive charge, so that the emitter junction barrier is lowered, thereby causing an increase in electron injection from the third region 104 to the second region 103; at the same time, electrons drift into the second region 103 under the action of the electric field and are blocked by the barrier of the emitter junction, so that a portion of the electrons is trapped in the second region 103 and form an excess of negative charges, so that the barrier of the emitter junction is lowered, thereby causing an increase in hole injection from the fourth region 105 into the first region 102. Thereby, a current positive feedback can be formed inside the photosensitive device 100, so that the photosensitive device 100 in an on state is quickly turned on in a short time. In some embodiments, sensing of incident light with a low optical power density may be achieved by detecting the moment of turning on the light sensing device 100 to quantitatively characterize the incident light power density.

In other words, the light detector unit 200 as described above can not only realize general light detection by the above-mentioned operation method, but further, can realize faint light sensing by recording the time when the light sensing device 100 is turned on during the incident of light, and quantitatively characterize the incident light power density (i.e., light intensity) by detecting the time when the light sensing device is turned on, for example, convert into a digital value for subsequent processing.

Fig. 5 illustrates a graph of the timing of turn-on of a photosensitive device in a photodetector cell in accordance with at least one embodiment of the present disclosure versus incident optical power density.

As shown in fig. 5, the photosensitive device (e.g., the photosensitive device 100 of fig. 2 and/or fig. 3) in the photodetector unit according to at least one embodiment of the present disclosure may be determined to be in the photosensitive device 100 at different incident light power densities (P)The time corresponding to the voltage dip and/or the current peak, i.e. the time of turning on the light sensing device 100, is detected, wherein the origin of coordinates 0 in fig. 5 corresponds to the time when the reset RST in fig. 4A is started. As can be seen from fig. 5, the higher the incident light power density, the earlier the light receiving device 100 is turned on. Specifically, as shown in FIG. 5, when the incident light power density is 1.5X 10^-6At the earliest, the photosensitive device 100 is turned on at about 1.5 × 10^-2About a second; when the incident light power density is 2 x 10^-8When the light sensing device 100 is turned on, the timing of the turn-on is about 1.2 × 10^-1At second, it is clearly later than when the incident light power density is 1.5X 10^-6The moment of turn-on of the photosensitive device 100. It can be seen that, since the turn-on time of the photosensitive device 100 is related to the incident light power density, by recording the turn-on time of the photosensitive device 100 in the process of light incidence, the detection and sensing of light with different intensities can be realized, and especially according to at least one embodiment of the present disclosure, the light power density can be less than 1 × 10 for the turn-on time of the photosensitive device 100^-7The low light is detected and sensed.

In addition, as described above, the light detector unit according to at least one embodiment of the present disclosure may perform both micro light sensing and light sensing as a general photodiode or triode, and thus, at least one embodiment of the present disclosure also provides a method of operating the light detector unit between a plurality of modes. This will be described below with reference to fig. 3.

For example, in some embodiments, placing the mode set signal SEL1 high and the mode set signal SEL2 low keeps the first select transistor M1 and the second select transistor M2 on; the reset signal RST is set low to keep the reset transistor M3 turned on to effect a reset of the photodetector cell 200. In this case, if only the reset signal RST is set high and the reset transistor M3 is turned off, the photodetector cell 200 may enter the diode mode. At this time, the mode setting signal SEL1 is set low and the mode setting signal SEL2 is set high, the first selection transistor M1 and the second selection transistor M2 are kept turned off, and the light detector unit 200 may enter the light detection mode, for example, the light sensing may be performed by controlling the operating state of the light sensing device 100, so that the conversion from the diode to the light sensing of the light detector unit 200 is realized.

However, for the photodetector cell 200 after reset, it is not necessary to enter the diode mode. For example, in other embodiments, after implementing the resetting of the photo-detector unit 200 as described above, the reset signal RST may be directly set high, and the mode setting signal SEL1 may be set low and the mode setting signal SEL2 may be set high, i.e., the reset transistor M3 is turned off and the first and second selection transistors M1 and M2 are kept off, then the photo-detector unit 200 may directly enter the photo-detection mode. Alternatively, the photodetector cell 200 that enters the diode mode may be directly reset, rather than having to enter the photodetection mode, in other words, the photodetector cell 200 may be directly reset by setting the reset signal RST low when the photodetector cell 200 is in the diode mode.

In addition, as described above, the photodetector unit according to at least one embodiment of the present disclosure may perform both micro light sensing and photo sensing as a general phototransistor, and thus, at least one embodiment of the present disclosure also provides a method of operating the photodetector unit between a plurality of modes. This will be described below with reference to fig. 3.

For example, in some embodiments, both the mode set signal SEL1 and the mode set signal SEL2 are asserted low, keeping the first select transistor M1 off and the second select transistor M2 on; the reset signal RST is set low to keep the reset transistor M3 turned on to effect a reset of the photodetector cell 200. In this case, if only the reset signal RST is set high and the reset transistor M3 is turned off, the photodetector cell 200 may enter a triode mode. At this time, the mode setting signal SEL1 is set to be low and the mode setting signal SEL2 is set to be high, the first selection transistor M1 and the second selection transistor M2 are kept to be turned off, and the light detector unit 200 may enter the light detection mode, for example, the light sensing device 100 may be controlled to perform dim light sensing, so that the conversion from the triode sensing to the dim light sensing of the light detector unit 200 is realized.

Based on the above method, the light detector unit 200 can operate between multiple modes, and in some embodiments, can expand the lowest light intensity that can be detected by the pixel, and can also improve the highest light intensity that can be detected by the pixel, thereby having a wider application range. It should be understood that the above description of switching between different modes is merely exemplary, and that there is no necessarily sequential relationship between the modes.

Also disclosed in at least one embodiment of the present disclosure is an electronic device comprising the above-described light detector unit 200 for light detection. For example, the electronic device may be a light sensitive element, such as an image sensor, and may comprise one or more photo detector units 200, e.g. in case of a plurality of photo detector units 200, the photo detector units 200 may be arranged in an array, whereby detection of light incident patterns may be achieved, e.g. capturing image signals, thereby for imaging, in combination with a color filter array, and also for capturing color images.

Also disclosed in at least one embodiment of the present disclosure is a pixel cell, for example for use in an image sensor, comprising the above-described photodetector cell 200 for photodetection. The pixel cell further comprises a sampling unit for sampling the photosensitive device 100 of the light detector unit 200. For example, the sampling unit comprises a sampling circuit that is operable between a plurality of modes to sample the light detector cell 200 in different modes. The working principle of a pixel unit comprising a photo detector unit and a sampling unit will be briefly described below in connection with fig. 6A and 6B.

Fig. 6A illustrates a workflow diagram of the photodetector unit 200 and the sampling unit 600 according to at least one embodiment of the present disclosure. As described above, when the light is detected by the light detector unit 200, that is, when light is incident to the light sensing device 100 of the light detector unit 200, a positive feedback of current can be formed inside the light sensing device 100 and the light sensing device can be turned on quickly in a short time. As shown in fig. 3, the light detector unit 200 may transmit a light sensing signal to the sampling unit 600 when the light sensing device 100 is turned on. Upon receiving the light sensing signal from the light detector unit 200, the sampling unit 600 may generate a corresponding sampling signal based on the received light sensing signal. By the information of the sampling signal outputted from the sampling unit 600, the turn-on time of the photosensitive device 100 of the photo-detector unit 200 can be derived, and thus the power density of the light detected by the photo-detector unit 200 can be obtained. The sampled signal is, for example, further processed (e.g., analog-to-digital converted, etc.) for other operations (forming an image), e.g., the power density of the incident light may correspond to the gray scale of the image pixels.

Fig. 6B illustrates a circuit structure schematic diagram of a pixel unit 60 according to at least one embodiment of the present disclosure. The photo detector unit of the pixel unit is photo-sensitive between a plurality of modes, and the sampling unit is correspondingly operable between the plurality of modes for sampling the photo detector unit in the different modes.

As shown in fig. 6B, the pixel unit 60 includes the photodetector unit 200 and the sampling unit 600 shown in fig. 3. The circuit structure of the light detector unit 200 can be referred to the above description, and is not described herein again. The sampling unit 600 includes a mode selection transistor M4, a switching transistor M5, a first source follower transistor M6, a second readout selection transistor M7, a second source follower transistor M8, and a first readout selection transistor M9.

In some embodiments, the mode selection transistor M4 may act as a mode switching gating device for the sampling unit 600 for switching of the sampling mode, such that the sampling unit 600 may perform sampling of different modes depending on the switching of the photodetector cell 200 between different modes. For example, in the embodiment shown in FIG. 6B, the source of the mode select transistor M4 is connected to the second electrode 122 of the photo-sensing device 100 of the photo-detector cell 200 and is configured to receive the photo-sensing signal V from the photo-sensing device 100_aAnd its drain is electrically connected to the first source-drain of the first source follower transistor M6, and its gate is configured to receive the mode selection signal MS.

In some embodiments, the switching transistor M5 may be implemented as a switching device in the sampling unit 600 with its gate configured toReceiving a light-sensitive signal V from a photodetector unit_aIts drain may be electrically connected to a supply voltage VDD, for example, to the first supply voltage terminal VDD, and its source may be connected to the drain of the first source follower transistor M6. As shown in FIG. 6B, the gate of the switching transistor M5 may be electrically connected to the second electrode 122 of the photo sensing device 100 to receive the photo sensing signal V_a。

In some embodiments, the first source follower transistor M6 and the second source follower transistor M8 may be used as source-drain followers in the sampling unit 600, and the voltages output at their sources may respectively follow the voltage signal variation applied from their gates. For example, the gate of the first source follower transistor M6 is configured to receive the first voltage control signal WL3, i.e., the first source follower transistor M6 is used as a follower following the first voltage control signal WL 3; the source of the first source follower transistor M6 is electrically connected to the gate of the second source follower transistor M8, in which case the capacitance voltage at the gate of the second source follower transistor M8 may vary with the first voltage control signal WL3 received at the gate of the first source follower transistor M6, and therefore the gate capacitance of the second source follower transistor M8 may serve as a sampling capacitor to collect the photo-sensing signal received by the sampling unit 600.

In some examples, the drain of the second source follower transistor M8 may also be electrically connected to the first supply voltage terminal VDD, e.g., to the same supply voltage terminal VDD as the drain of the switch transistor M5.

In some embodiments, the gate of the first readout select transistor M9 is configured to receive a first row select signal WL2, its drain is connected to the source of the second source follower transistor M8, and its source is electrically connected to the first column output BL2 to serve as a signal readout gate tube to enable selective connection of the sampling cell to the column output.

In some embodiments, the gate of the second readout select transistor M7 is configured to receive a second row select signal WL1, its drain is connected to the source of the first source follower transistor M6, and its source is electrically connected to the second column output BL1 to serve as a signal readout gate tube to enable selective connection of the sampling cell to the column output.

In the embodiment shown in fig. 6B, the switching transistor M5, the first source follower transistor M6, the second readout selection transistor M7, the second source follower transistor M8 and the first readout selection transistor M9 may be N-type transistors, while the mode selection transistor M4 is a P-type transistor. The present disclosure does not limit the arrangement of the types of the transistors in the embodiments, for example, if the type of one transistor in the circuit is changed, the control signal is adjusted accordingly, for example, the N-type transistor is turned on by the high level of the square wave signal, the P-type transistor is turned on by the low level of the square wave signal, the source of the N-type transistor is connected to the low voltage terminal, and the source of the P-type transistor is connected to the high voltage terminal.

The method of operation of the pixel unit 60 will be described in detail below in connection with the photodetector unit 200 and the sampling unit 600. As shown in FIG. 6B, the sampling unit 600 may receive the light sensing signal V from the light detector unit 200 through the gate of the switching transistor M5_a(ii) a And the received photosensitive signal V is sampled by the sampling unit 600_aSamples and outputs a sampled signal. Specifically, in conjunction with FIG. 4A described above, when the photodetector cell is in the sensing mode, the photodetector cell 200 is initially in the super-OFF state (state I'), where the PN junction voltage V formed in the photosensitive device 100_npLarger, the first selection transistor M1 and the second selection transistor M2 of the photosensitive device 100 are kept turned off and as the incident light is continuously irradiated, the PN junction voltage V formed in the photosensitive device 100_npTo reduce, the terminal voltage at the second electrode 122 of the photosensitive device 100 is approximate to the PN junction voltage V formed in the photosensitive device 100_npThereby gradually switching the light sensing device 100 to the on-state (state III'), and thus, the sampling unit 600 may receive the light sensing signal V through the gate of the switching transistor M5 electrically connected to the second electrode 122 of the light sensing device 100_aTo enable sampling of the photodetector unit 200.

For example, as shown above, when the light sensing device 100 of the photodetector cell 200 is irradiated with incident light, the mode setting signal SEL1 is set high and the mode setting signal SEL2 is set low, keeping the first and second selection transistors M1 and M2 turned on; the reset signal RST is set low to keep the reset transistor M3 turned on to effect a reset of the photodetector cell 200. At this time, the mode setting signal SEL1 is set low and the mode setting signal SEL2 is set high, the first selection transistor M1 and the second selection transistor M2 are kept turned off, and the photo-detector unit 200 can enter the dim sensing mode.

When the photo-detector unit 200 enters the dim light sensing mode, accordingly, the dim light sampling mode of the sampling unit 600 is used to sense the photo-reception signal V received from the photo-detector unit 200_aSampling is performed.

Specifically, the second readout selection transistor M7 is turned off by the mode selection signal MS turning off the mode selection transistor M4 of the sampling unit 630 and causing the second row selection signal WL1 applied to the gate of the second readout selection transistor M7 to be low. Since the voltage of the second electrode 122 of the light sensing device 100 is high, the switching transistor M5 is turned on, and the first voltage control signal WL3 of the fixed pattern is applied to the gate of the first source follower transistor M6. For example, the first voltage control signal WL3 may be a periodic electrical signal, e.g., a periodic electrical signal including a unidirectionally varying portion, and each period may include a unidirectionally varying portion such as a triangular wave or a half sine wave. At this time, the gate capacitance voltage of the second source follower transistor M8 periodically varies following the first voltage control signal WL3 applied at the gate of the first source follower transistor M6. After a certain time, the photosensitive device 100 is turned on, and the voltage of the second electrode 122 of the photosensitive device 100, i.e. the photosensitive signal V_aFalls below the threshold voltage of the switching transistor M5, the switching transistor M5 turns off. At this time, the gate capacitance voltage of the second source follower transistor M8 will no longer follow the first voltage control signal WL3 applied at the gate of the first source follower transistor M6 periodically, but will leak with a constant drain current, i.e., the gate capacitance voltage of the second source follower transistor M8 will remain constant. A first row select signal WL2 is periodically applied to the gate of the first readout select transistor M9, and a signal voltage VBL2 is read from the first column output terminal BL2 of the first readout select transistor M9. Further, according to the second stepThe sampling signal output from the one-column output terminal BL2 acquires the off time of the switching transistor M5 of the sampling unit 600, and the incident light power density can be calculated based on the off time of the switching transistor M5.

For example, as shown above, when the light sensing device 100 of the photodetector cell 200 is irradiated with incident light, both the mode setting signal SEL1 and the mode setting signal SEL2 are set low, keeping the first selection transistor M1 off and the second selection transistor M2 on; the reset signal RST is set low to keep the reset transistor M3 turned on to effect a reset of the photodetector cell 200. In this case, if only the reset signal RST is set high and the reset transistor M3 is turned off, the light detector unit 200 may enter a triode sensing mode.

When the light detector unit 200 enters the triode sensing mode, the triode sampling mode of the sampling unit 600 is used to sample the photo-sensing signal received from the light detector unit 200 accordingly. Specifically, the mode select transistor M4 is applied with the mode select signal MS to turn on the mode select transistor M4. The first source follower transistor M6 is turned on and the second row select signal WL1 applied to the gate of the second sense select transistor M7 is made low, turning off the second sense select transistor M7. At this time, the light sensing signal is received through the gate of the second source follower transistor M8, that is, the voltage signal of the second electrode 122 of the light sensing device 100 is collected with the gate capacitance of the second source follower transistor M8 as a sampling capacitance. The first row select signal WL2 is applied to the gate of the first readout select transistor M9, and the sample signal can be read directly from the first column output BL2 of the first readout select transistor M9.

For another example, as shown above, when the light sensing device 100 of the photodetector cell 200 is irradiated by incident light, the mode setting signal SEL1 is set high and the mode setting signal SEL2 is set low, keeping the first selection transistor M1 and the second selection transistor M2 turned on; the reset signal RST is set low to keep the reset transistor M3 turned on to effect a reset of the photodetector cell 200. Directly setting the reset signal RST high and the reset transistor M3 off, the photo-detector cell 200 may enter a diode sensing mode.

When the photo-detector unit 200 enters the diode sensing mode, the photo-reception signal received from the photo-detector unit 200 is sampled using the diode sampling mode of the sampling unit 600 accordingly. Further, according to at least one embodiment of the present disclosure, the diode sampling mode of the sampling unit 600 may include a linear sampling mode and a logarithmic sampling mode.

The operation methods of the two diode sampling modes of the sampling unit 600 will be described in detail below with reference to fig. 7A and 7B. Fig. 7A shows the signal readout path of the linear sampling mode and the logarithmic sampling mode of the sampling unit 600; fig. 7B shows incident optical power density versus output voltage for the two signal readout paths of fig. 7A.

When the incident light power density at the photosensitive device 100 is small, the sampling unit 600 may employ a linear sampling mode as shown in fig. 7A. Specifically, the mode select transistor M4 is turned off, keeping the first source follower transistor M6 turned on. At this time, the light sensing signal is received through the gate of the switching transistor M5, that is, the voltage signal of the second electrode 122 of the light sensing device 100 is collected by taking the gate capacitance of the switching transistor M5 as the sampling capacitance. The second row select signal WL1 is applied to the gate of the second readout selection transistor M7, the second readout selection transistor M7 is turned on, and the sampling signal is read through the second column output terminal BL 1.

When the incident light power density at the light sensing device 100 is large, the sampling unit 600 may sample using a logarithmic sampling pattern as shown in fig. 7A. Specifically, the mode select transistor M4 is applied with the mode select signal MS to turn on the mode select transistor M4. The first source follower transistor M6 is turned on, and the second row select signal WL1 with a specific voltage value is applied to the gate of the second sense select transistor M7, so that the second sense select transistor M7 is in a sub-threshold operating state. At this time, the light sensing signal is received through the gate of the second source follower transistor M8, that is, the voltage signal of the second electrode 122 of the light sensing device 100 is collected with the gate capacitance of the second source follower transistor M8 as a sampling capacitance. The first row select signal WL2 is applied to the gate of the first readout select transistor M9, and the sample signal can be read directly from the first column output BL2 of the first readout select transistor M9.

As can be seen from fig. 7B, when the incident light power density is smaller, the relationship between the incident light power density and the output voltage approaches a linear relationship; when the incident light power density is larger, the relationship between the incident light power density and the output voltage is closer to a logarithmic relationship. Therefore, when the sampling unit 600 samples the received photo-reception signal using the diode sampling mode, the sampling unit 600 can more accurately sample by selecting different diode sampling modes according to the magnitude of the incident light power density as described above.

In addition, as described above, the light detector unit according to at least one embodiment of the present disclosure may perform both micro light sensing and light sensing as a general photodiode or triode, and thus, at least one embodiment of the present disclosure also provides a method of operating the light detector unit between a plurality of modes.

Accordingly, for the sampling unit 600, in case that the photo-detector unit 200 enters the triode mode, the mode select transistor M4 is applied with the mode select signal MS to turn on the mode select transistor M4; the first source follower transistor M6 is turned on, and the second row select signal WL1 applied to the gate of the second sense select transistor M7 is lowered to turn off the second sense select transistor M7. At this time, a light sensing signal may be received from the photodetector cell 200 through the gate of the second source follower transistor M8; a first row select signal WL2 is applied to the gate of the first readout select transistor M9 to read a sample signal of the received light sensing signal from the first column output BL2 of the first readout select transistor M9. At this time, the sampling unit 600 may sample the photo-sensing signal in a triode sampling mode.

When the photo-detector cell 200 is to be transistorized from triode to microphotograph, the first voltage control signal WL3 is periodically applied to the gate of the first source follower transistor M6, the mode selection transistor M4 is turned off and the switching transistor M5 is turned on, at which time the gate capacitance voltage of the second source follower transistor M8 is periodically changed following the first voltage control signal WL 3. When the photo-detector cell 200 is switched to the dim light sensing state, the switching transistor M5 is turned off, the first row select signal WL2 is applied to the gate of the first readout select transistor M9, and a sample signal of the received photo-sensing signal is read from the first column output BL2 of the first readout select transistor M9. At this time, the sampling unit 600 samples the photo-reception signal in the low light level sampling mode. Therefore, conversion of the sampling unit 600 from the triode to the glimmer sensing is realized.

Based on the above method, the sampling unit 600 may implement operations between a plurality of modes corresponding to the light detector unit 200. It should be understood that the above description of switching between different modes is merely exemplary and that there is no necessarily sequential relationship between the modes.

For the present disclosure, there are the following points to be explained:

(1) in the drawings of the embodiments of the present disclosure, only the structures related to the embodiments of the present disclosure are referred to, and other structures may refer to general designs.

(2) Features of the disclosure in the same embodiment and in different embodiments may be combined with each other without conflict.

The above description is only for the specific embodiments of the present disclosure, but the scope of the present disclosure is not limited thereto, and any person skilled in the art can easily think of the changes or substitutions within the technical scope of the present disclosure, and shall cover the scope of the present disclosure. Therefore, the protection scope of the present disclosure shall be subject to the protection scope of the claims.

Claims

1. A photodetector unit, comprising:

a control circuit;

a photosensitive device coupled with the control circuit and including:

a semiconductor substrate including a main surface including first and second regions disposed adjacent to each other and having different doping types, third and fifth regions formed in the first region, and fourth and sixth regions formed in the second region, wherein the third and second regions have the same doping type and have a first spacing from the second region, the fourth region has the same doping type as the first region and have a second spacing from the first region, the fifth region has the same doping type as the first region and is on a side of the third region facing away from the second region, the sixth region has the same doping type as the second region and is on a side of the fourth region facing away from the first region, and the first and second spacings form a channel region of the thyristor;

a gate insulating layer disposed on the main surface;

a main gate, a first side gate and a second side gate adjacently disposed on the gate insulating layer, wherein the main gate is disposed at least partially corresponding to the channel region in a direction perpendicular to the main surface, the first side gate is disposed at least partially corresponding to the first space and insulated from the main gate in the direction perpendicular to the main surface, and the second side gate is disposed at least partially corresponding to the second space and insulated from the main gate in the direction perpendicular to the main surface; and

a first electrode disposed on the major surface and in electrical contact with the third region, a second electrode disposed on the major surface and in electrical contact with the fourth region, a third electrode disposed on the major surface and corresponding to the fifth region in a direction perpendicular to the major surface, and a fourth electrode disposed on the major surface and corresponding to the sixth region in a direction perpendicular to the major surface.

2. The photodetector cell of claim 1, wherein the light sensing device further comprises:

a first sidewall insulating layer insulating the main gate from the first sidewall gate;

a second sidewall insulating layer disposed on the main surface and adjacent to the first sidewall gate, and the first sidewall insulating layer at least partially covers a side surface of the first sidewall gate adjacent to the second sidewall insulating layer;

a third sidewall insulating layer insulating the main gate from the second side gate; and

a fourth sidewall insulating layer disposed on the main surface and adjacent to the second side gate, and the third sidewall insulating layer at least partially covers a side surface of the second side gate adjacent to the fourth sidewall insulating layer.

3. The photodetector cell of claim 1, wherein the light sensing device further comprises:

a first trench isolation region located in the first region and separating the third region and the fifth region by the first trench isolation region;

a second trench isolation region in the second region and separating the fourth region and the sixth region by the second trench isolation region.

4. The photodetector cell of claim 1, wherein the control circuit comprises:

a first selection transistor, wherein a first source drain of the first selection transistor is configured to be electrically connected to the first electrode, and a second source drain of the first selection transistor is configured to be electrically connected to the third electrode;

and a second selection transistor, wherein a first source drain of the second selection transistor is configured to be electrically connected to the second electrode, and a second source drain of the second selection transistor is configured to be electrically connected to the fourth electrode.

5. The photodetector cell of claim 4, wherein the control circuit further comprises:

and the first source drain electrode of the reset transistor is configured to be electrically connected with the second electrode and the first source drain electrode of the second selection transistor, and the second source drain electrode of the reset transistor is configured to be electrically connected with a first power supply voltage end.

6. A method of operating a light detector unit as claimed in any one of claims 1-5, comprising:

the control circuit is operated to select the light detection mode of the photosensitive device and control the photosensitive device to perform light detection.

7. The operating method of claim 6, wherein operating the control circuit to select a light detection mode of the light sensing device comprises:

shorting the first electrode with the third electrode, and shorting the second electrode with the fourth electrode and suspending the second electrode and the fourth electrode;

disconnecting the first electrode from the third electrode and disconnecting the second electrode from the fourth electrode from the short to cause the photosensitive device to enter a first photodetection mode.

8. The operating method of claim 7, wherein controlling the light sensing device to perform light detection comprises:

and applying a control voltage to the first side grid electrode of the photosensitive device so that the photosensitive device is started in the process of light incidence.

9. The operating method of claim 8, wherein controlling the light sensing device to perform light detection further comprises:

and recording the moment when the photosensitive device is started in the process of light incidence.

10. The method of operation of claim 7, further comprising, prior to shorting the second electrode to the fourth electrode and floating the second and fourth electrodes:

the second electrode and the fourth electrode are shorted and connected to a first power supply voltage for resetting.

11. The operating method of claim 6, wherein operating the control circuit to select a light detection mode of the light sensing device comprises:

and short-circuiting the first electrode with the third electrode, short-circuiting the second electrode with the fourth electrode, and suspending the second electrode and the fourth electrode to enable the photosensitive device to enter a second light detection mode.

12. The operating method of claim 6, wherein operating the control circuit to select a light detection mode of the light sensing device comprises:

disconnecting the first electrode from the third electrode, shorting the second electrode with the fourth electrode, and suspending the second electrode and the fourth electrode, so that the photosensitive device enters a third light detection mode.

13. An electronic device comprising a photodetector unit as claimed in any one of the claims 1 to 5.

14. A pixel cell comprising a photodetector unit as claimed in any one of claims 1 to 5; and a sampling unit, wherein the sampling unit samples the light sensing signal received from the light detector unit.