Semiconductor Radiation Detectors

Abstract

The present invention discloses a radiation detector (100), comprising: an electronic device layer (120) comprising a first set of electrical contacts (118A) and a second set of electrical contacts (118B); a radiation absorbing layer (110) configured to absorb radiation; a first set of electrodes (119A) and a second set of electrodes (119B), wherein the first set of electrodes (119A) and the second set of electrodes (119B) intersect with each other and extend into the radiation absorbing layer (110) along a thickness direction thereof; wherein the electronic device layer (120) and the radiation absorbing layer (110) are combined so that the first set of electrodes (119A) is electrically connected to the first set of electrical contacts (118A), and the second set of electrodes (119B) is electrically connected to the second set of electrical contacts (118B).

Description

[Background technology]

[0001] A radiation detector is a device that can be used to measure the flux, spatial distribution, spectrum, or other properties of radiation.

[0002] Radiation detectors can be used in many applications, one important application being imaging. Radiation imaging is a radiographic technique and can be used to reveal the internal structure of objects of inhomogeneous composition and opaque objects such as the human body.

[0003] Early radiation detectors used for imaging included photographic plates and photographic films. Photographic plates can be glass plates with a light-sensitive emulsion coating. Although photographic plates were replaced by photographic films, they are still used in special cases because of the superior quality and extreme stability they offer. Photographic films can be plastic films (e.g., strips or sheets) with a light-sensitive emulsion coating.

[0004] In the 1980s, photoexcitable phosphor plates (PSP plates) became available. PSP plates contain phosphor materials with color centers in their lattices. When the PSP plates are exposed to radiation, electrons excited by the radiation are trapped in the color centers until they are excited by a laser beam scanned over the surface of the PSP plates. When the laser scans the PSP plates, the trapped excited electrons emit light, which is collected by a photomultiplier tube, and the collected light is converted into a digital image. Compared to photographic negatives and photographic films, PSP plates are reusable.

[0005] Another type of radiation detector is a radiation image intensifier. The components of a radiation image intensifier are usually sealed in a vacuum. Compared to photographic plates, photographic films, and PSP boards, radiation image intensifiers can produce real-time images, that is, no post-exposure processing is required to produce an image. The radiation first hits the input phosphor (e.g., cesium iodide) and is converted into visible light. The visible light then hits the photocathode (e.g., a thin metal layer containing cesium and antimony compounds) and causes electron emission. The number of electrons emitted is proportional to the intensity of the incident radiation. The emitted electrons are projected onto the output phosphor through an electron optic and cause the output phosphor to produce a visible light image.

[0006] Scintillators operate somewhat similarly to radiation image intensifiers in that the scintillator (e.g., sodium iodide) absorbs radiation and emits visible light, which can then be detected by a suitable image sensor. In the scintillator, the visible light diffuses and scatters in all directions, which reduces spatial resolution. Reducing the scintillator thickness helps improve spatial resolution, but also reduces the absorption of radiation. Therefore, scintillators must achieve a compromise between absorption efficiency and resolution.

[0007] Semiconductor radiation detectors largely overcome the above problems by converting radiation directly into electrical signals. A semiconductor radiation detector may include a semiconductor layer that absorbs radiation at a wavelength of interest. When a radiation particle is absorbed in the semiconductor layer, a plurality of carriers (e.g., electrons and holes) are generated and swept toward electrical contacts on the semiconductor layer under an electric field. The cumbersome thermal management required in currently available semiconductor radiation detectors (e.g., Medipix) may make semiconductor radiation detectors with larger areas and a large number of pixels difficult or impossible to produce. [Summary of the invention]

[0008] Disclosed herein is a radiation detector, comprising: an electronic device layer comprising a first group of electrical contacts and a second group of electrical contacts; a radiation absorbing layer configured to absorb radiation; a first group of electrodes and a second group of electrodes, wherein the first group of electrodes and the second group of electrodes intersect each other and extend into the radiation absorbing layer along a thickness direction thereof; wherein the electronic device layer and the radiation absorbing layer are combined so that the first group of electrodes are electrically connected to the first group of electrical contacts, and the second group of electrodes are electrically connected to the second group of electrical contacts.

[0009] According to an embodiment, the radiation absorbing layer includes GaAs, CdTe, CZT or a combination thereof.

[0010] According to an embodiment, the first set of electrodes and the second set of electrodes comprise a metal or a semiconductor.

[0011] According to an embodiment, the first set of electrodes and the second set of electrodes are configured to be differentially biased.

[0012] According to an embodiment, the distance between one electrode of the first set of electrodes and the nearest neighboring electrode of the second set of electrodes does not exceed 2λ, wherein λ is the mean free path of charge carriers in the radiation absorbing layer.

[0013] According to an embodiment, the second set of electrodes are cylindrical.

[0014] According to an embodiment, the second set of electrodes are prismatic.

[0015] According to an embodiment, the first set of electrodes comprises a grid.

[0016] According to an embodiment, the second set of electrodes are discrete.

[0017] According to an embodiment, the first set of electrodes and the second set of electrodes are coextensive in the thickness direction.

[0018] According to an embodiment, the radiation detector further comprises an insulating layer at a surface of the radiation absorbing layer remote from the electronics layer; wherein the first set of electrodes and the second set of electrodes are connected to the insulating layer.

[0019] According to an embodiment, the radiation absorbing layer includes a polycrystalline semiconductor.

[0020] According to an embodiment, the electronics layer is configured to bias the first set of electrodes and the second set of electrodes to different voltages through the first set of electrical contacts and the second set of electrical contacts.

[0021] According to an embodiment, said radiation is X-rays.

[0022] According to an embodiment, the electronic device layer includes: a first voltage comparator, which is configured to compare the voltage of the second group of electrical contacts with a first threshold; a second voltage comparator, which is configured to compare the voltage with a second threshold; a counter, which is configured to record the number of radiation particles received by the radiation absorbing layer; a controller, wherein the controller is configured to start a time delay when it is determined from the first voltage comparator that the absolute value of the voltage is equal to or exceeds the absolute value of the first threshold; wherein the controller is configured to start the second voltage comparator during the time delay; wherein the controller is configured to increase the number recorded by the counter by one if the second voltage comparator determines that the absolute value of the voltage is equal to or exceeds the absolute value of the second threshold.

[0023] According to an embodiment, the radiation detector further comprises an integrator electrically connected to the electrode, wherein the integrator is configured to collect carriers from the electrode.

[0024] According to an embodiment, the controller is configured to activate the second voltage comparator upon initiation or expiration of the time delay.

[0025] According to an embodiment, the controller is configured to connect the electrical contact to electrical ground.

[0026] According to an embodiment, the rate of change of the voltage is substantially zero upon expiration of the time delay.

[0027] A method is disclosed herein, comprising: obtaining a substrate having an insulating layer and a semiconductor layer attached to the insulating layer; forming a first set of electrodes and a second set of electrodes from the semiconductor layer by etching the entire thickness of the semiconductor layer; introducing semiconductor particles between the first set of electrodes and the second set of electrodes; combining the semiconductor layer with an electronic device layer comprising a first set of electrical contacts and a second set of electrical contacts so that the first set of electrodes is electrically connected to the first set of electrical contacts, and the second set of electrodes is electrically connected to the second set of electrical contacts.

[0028] According to an embodiment, the semiconductor particles include GaAs, CdTe, CZT or a combination thereof.

[0029] According to an embodiment, said introducing semiconductor particles between the first set of electrodes and the second set of electrodes comprises fusing the semiconductor particles.

[0030] According to an embodiment, the first set of electrodes and the second set of electrodes are configured to be differentially biased.

[0031] According to an embodiment, the distance between one electrode of the first set of electrodes and the nearest electrode of the second set of electrodes does not exceed 2λ, wherein λ is the mean free path of charge carriers across the semiconductor particles.

[0032] According to an embodiment, the second set of electrodes are cylindrical.

[0033] According to an embodiment, the second set of electrodes are prismatic.

[0034] According to an embodiment, the first set of electrodes comprises a grid.

[0035] According to an embodiment, the second set of electrodes are discrete.

[0036] According to an embodiment, the electronics layer is configured to bias the first set of electrodes and the second set of electrodes to different voltages through the first set of electrical contacts and the second set of electrical contacts.

[0037] According to an embodiment, the method further includes removing the insulating layer.

Brief Description of the Drawings

[0038] Figure 1A A cross-sectional view of a radiation detector according to an embodiment is schematically shown.

[0039] Figure 1B A detailed cross-sectional view of the radiation detector according to an embodiment is schematically shown.

[0040] Figure 1C-1E Each schematically shows a suitable configuration of the first group of electrodes and the second group of electrodes of the radiation detector according to an embodiment.

[0041] Figure 2A and Figure 2B Each of the diagrams schematically shows an electronic system component diagram of the radiation detector according to an embodiment.

[0042] Figure 3 Schematically illustrating the temporal variation of the current flowing through an electrical contact (upper curve) caused by carriers generated by a visible light pulse incident on a pixel associated with the electrical contact, and the corresponding temporal variation of the voltage (lower curve) according to an embodiment.

[0043] Figure 4A-4F The flowchart schematically shows a method for manufacturing the radiation detector according to an embodiment.

[0044] Figure 5-Figure 9 Each schematically illustrates a system comprising a radiation detector as described herein. [Specific implementation method]

[0045] Figure 1A A cross-sectional view of a radiation detector 100 according to an embodiment is schematically shown. The radiation detector 100 may include a radiation absorbing layer 110 and an electronic device layer 120 (e.g., an ASIC), the electronic device layer 120 being used to process or analyze an electrical signal of incident radiation generated in the radiation absorbing layer 110. In an embodiment, the radiation detector 100 does not include a scintillator. The radiation absorbing layer 110 may include a polycrystalline semiconductor material, such as GaAs, CdTe, CZT, or a combination thereof. The semiconductor may have a high mass attenuation coefficient for the radiation energy of interest. The radiation detector 100 may further include an insulating layer 103 on a surface of the radiation absorbing layer 110 away from the electronic device layer 120. The radiation may be an X-ray.

[0046] like Figure 1B As shown in the detailed cross-sectional view of the radiation detector 100 according to an embodiment, the radiation detector 100 includes a first group of electrodes 119A and a second group of electrodes 119B that cross each other and extend into the radiation absorption layer 110 along the thickness direction of the radiation absorption layer 110. The first group of electrodes 119A and the second group of electrodes 119B may include metal or semiconductor materials. The first group of electrodes 119A and the second group of electrodes 119B may be coextensive in the thickness direction of the radiation absorption layer 110. The first group of electrodes 119A and the second group of electrodes 119B may be attached to the insulating layer 103.

[0047] like Figure 1B As shown, when a radiation particle hits the radiation absorbing layer 110, the radiation particle may be absorbed by the radiation absorbing layer 110, and the radiation absorbing layer 110 may generate one or more carriers through several mechanisms. One radiation particle may generate 10 to 100,000 carriers. The carriers may drift toward the first group of electrodes 119A and the second group of electrodes 119B under an electric field. The electric field may be established by differentially biasing the first group of electrodes 119A and the second group of electrodes 119B. According to an embodiment, the distance between one electrode in the first group of electrodes 119A and the nearest electrode in the second group of electrodes 119B (e.g., Figure 1B 104) does not exceed 2λ, where λ is the mean free path of carriers in the radiation absorbing layer 110.

[0048] like Figure 1C-1EAs shown in the example of, the first set of electrodes 119A and the second set of electrodes 119B can have any suitable size and shape. Figure 1C ), at least some of the second set of electrodes are discrete and cylindrical. According to an embodiment (e.g., in Figure 1D ), at least some of the second set of electrodes are discrete and prismatic. According to an embodiment (e.g., in Figure 1E ), the first set of electrodes comprises a grid and at least some of the second set of electrodes are discrete.

[0049] The electronics layer 120 may include an electronics system 121 suitable for processing or interpreting signals generated by radiation incident on the radiation absorbing layer 110. The electronics system 121 may include analog circuits such as filter networks, amplifiers, integrators, comparators, or digital circuits such as microprocessors and memory. The electronics system 121 may be electrically coupled to the radiation absorbing layer 110 via vias 131. The spaces between the vias may be filled with a filling material 130, which may increase the mechanical stability of the connection of the electronics layer 120 to the radiation absorbing layer 110. Other bonding techniques may be possible to connect the electronics system 121 to the radiation absorbing layer 110 without the use of vias.

[0050] The electronic device layer 120 has a first set of electrical contacts 118A and a second set of electrical contacts 118B. After combining the electronic device layer 120 and the radiation absorbing layer 110, the first set of electrodes 119A is electrically connected to the first set of electrical contacts 118A (through vias 131), and the second set of electrodes 119B is electrically connected to the second set of electrical contacts 118B (e.g., through vias 131). The electronic device layer 120 can be configured to bias the first set of electrodes 119A and the second set of electrodes 119B to different voltages through the first set of electrical contacts 118A and the second set of electrical contacts 118B, respectively. For example, one or more voltage sources 122 can provide a non-zero voltage to the first set of electrical contacts 118A, and the second set of electrical contacts 118B can be connected to a virtual ground of an amplifier in the electronic system 121.

[0051] Figure 2A and Figure 2B Each of the diagrams shows a component of the electronic system 121 according to an embodiment. The electronic system 121 may include a first voltage comparator 301 , a second voltage comparator 302 , a counter 320 , a switch 305 , a voltmeter 306 , and a controller 310 .

[0052] The first voltage comparator 301 is configured to compare the voltage of one electrical contact of the second set of electrical contacts 118B with a first threshold value. The first voltage comparator 301 may be configured to directly monitor the voltage or to calculate the voltage by integrating the current flowing through the electrical contact over a period of time. The first voltage comparator 301 may be controllably activated or deactivated by the controller 310. The first voltage comparator 301 may be a continuous comparator. That is, the first voltage comparator 301 may be configured to be continuously activated and continuously monitor the voltage. The first voltage comparator 301 may be a clocked comparator, which has the advantage of low power consumption. The first threshold value may be 5-10%, 10%-20%, 20-30%, 30-40% or 40-50% of the maximum voltage that a single visible light pulse can generate on the electrical contact. The maximum voltage may depend on the energy of the incident radiation particle, the material of the radiation absorbing layer 110, and other factors. For example, the first threshold may be 50 mV, 100 mV, 150 mV or 200 mV.

[0053] The second voltage comparator 302 is configured to compare the voltage with a second threshold. The second voltage comparator 302 may be configured to directly monitor the voltage or to calculate the voltage by integrating the current flowing through the electrical contact over a period of time. The second voltage comparator 302 may be a continuous comparator. The second voltage comparator 302 may be controllably enabled or disabled by the controller 310. When the second voltage comparator 302 is disabled, the power consumption of the second voltage comparator 302 may be less than 1%, less than 5%, less than 10% or less than 20% of the power consumption when the second voltage comparator 302 is enabled. The absolute value of the second threshold is greater than the absolute value of the first threshold. As used herein, the term "absolute value" or "modulus" |x| of a real number x is a non-negative value of x regardless of its sign. That is, The second threshold value may be 200%-300% of the first threshold value. The second threshold value is at least 50% of the maximum voltage that an incident radiation particle can generate on one of the second set of electrical contacts 118B. For example, the second threshold value may be 100mV, 150mV, 200mV, 250mV, or 300mV. The second voltage comparator 302 and the first voltage comparator 301 may be the same component. That is, the electronic system 121 may have the same voltage comparator that can compare the voltage to two different threshold values ​​at different times.

[0054] The first voltage comparator 301 or the second voltage comparator 302 may include one or more operational amplifiers or any other suitable circuits. The first voltage comparator 301 or the second voltage comparator 302 may have a high speed to allow the electronic system 121 to operate under a high flux of incident radiation particles. However, having a high speed usually comes at the expense of power consumption.

[0055] The counter 320 is configured to record at least one number of radiation particles received by the radiation absorbing layer 110 (e.g., radiation particles generated by carriers collected by a certain subset of the first set of electrodes 119A and a certain subset of the second set of electrodes 119B). The counter 320 can be a software component (e.g., a number stored in a computer memory) or a hardware component (e.g., 4017IC and 7490IC).

[0056] The controller 310 may be a hardware component, such as a microcontroller and a microprocessor. The controller 310 is configured to start a time delay from when the first voltage comparator 301 determines that the absolute value of the voltage is equal to or exceeds the absolute value of the first threshold (e.g., the absolute value of the voltage increases from an absolute value below the first threshold to an absolute value equal to or exceeding the first threshold). Absolute values ​​are used here because the voltage can be negative or positive. The controller 310 may be configured to keep the second voltage comparator 302, the counter 320, and any other circuits not required for the operation of the first voltage comparator 301 disabled before the first voltage comparator 301 determines that the absolute value of the voltage is equal to or exceeds the absolute value of the first threshold. The time delay may expire before or after the voltage becomes stable (i.e., the rate of change of the voltage is approximately zero). The phrase "the rate of change is approximately zero" means that the time rate of change of the voltage is less than 0.1% / ns. The phrase "the rate of change is approximately non-zero" means that the time rate of change of the voltage is at least 0.1% / ns.

[0057] The controller 310 may be configured to start the second voltage comparator during the time delay (including the start and expiration). In an embodiment, the controller 310 is configured to start the second voltage comparator at the start of the time delay. The term "start" means to put a component into an operating state (e.g., by sending a signal such as a voltage pulse or a logic level, by providing power, etc.). The term "disable" means to put a component into a non-operating state (e.g., by sending a signal such as a voltage pulse or a logic level, by cutting off power, etc.). The operating state may have a higher power consumption than the non-operating state (e.g., 10 times higher, 100 times higher, 1000 times higher). The controller 310 itself may be disabled until the output of the first voltage comparator 301 starts the controller 310 when the voltage absolute value equals or exceeds the first threshold absolute value.

[0058] If, during the time delay, the second voltage comparator 302 determines that the absolute value of the voltage is equal to or exceeds the absolute value of the second threshold, the controller 310 may be configured to increase the number recorded by the counter 320 by one.

[0059] The controller 310 may be configured to cause the optional voltmeter 306 to measure the voltage when the time delay expires. The controller 310 may be configured to cause the electrical contact 118B to be connected to electrical ground to reset the voltage and discharge any carriers accumulated on the electrical contact 118B. In an embodiment, the electrical contact 118B is connected to electrical ground after the time delay expires. In an embodiment, the electrical contact 118B is connected to electrical ground for a limited reset period. The controller 310 may cause the at least one electrical contact 119B to be connected to the electrical ground by controlling the switch 305. The switch may be a transistor such as a field effect transistor (FET).

[0060] In an embodiment, the electronic system 121 has no analog filter network (eg, RC network). In an embodiment, the electronic system 121 has no analog circuitry.

[0061] The voltmeter 306 may feed the measured voltage to the controller 310 in the form of an analog or digital signal.

[0062] The electronic system 121 may include an integrator 309 electrically connected to the electrical contact 118B, wherein the integrator is configured to collect carriers from the electrical contact 118B. The integrator 309 may include a capacitor in the feedback path of the amplifier. An amplifier configured in this way is called a capacitive transimpedance amplifier (CTIA). CTIA has a high dynamic range by preventing the amplifier from saturating and improves the signal-to-noise ratio by limiting the bandwidth in the signal path. Carriers from the electrical contact 118B accumulate on the capacitor over a period of time ("integration period"). After the integration period expires, the capacitor voltage is sampled and then reset by a reset switch. The integrator 309 may include a capacitor directly connected to the electrical contact 118B.

[0063] Figure 3 The time variation of the current caused by the carriers generated by the radiation particles flowing through the electrical contact 118B (upper curve) and the corresponding time variation of the voltage of the electrical contact 118B (lower curve) are schematically shown. The voltage may be the integral of the current with respect to time. At time t0, the radiation particles hit the radiation absorption layer 110, carriers begin to be generated in the radiation absorption layer 110, current begins to flow through the electrical contact 118B, and the absolute value of the voltage of the electrical contact 118B begins to increase. At time t1, the first voltage comparator 301 determines that the absolute value of the voltage is equal to or exceeds the absolute value of the first threshold value V1, the controller 310 starts the time delay TD1 and the controller 310 may deactivate the first voltage comparator 301 at the beginning of the TD1. If the controller 310 is deactivated before time t1, the controller 310 is activated at time t1. During the TD1, the controller 310 activates the second voltage comparator 302. As used herein, the term "during" a time delay means the start and the expiration (i.e., the end) and any time in between. For example, the controller 310 may enable the second voltage comparator 302 when the TD1 expires. If during the TD1, the second voltage comparator 302 determines that the absolute value of the voltage at time t2 is equal to or exceeds the absolute value of the second threshold value V2, the controller 310 waits for the voltage to stabilize. The voltage at time t e Stable, at this time all the carriers generated by the radiation particles drift out of the radiation absorption layer 110. s , the time delay TD1 expires. At time t e At or after the time, the controller 310 causes the voltmeter 306 to digitize the voltage and determine in which bin the energy of the radiation particle falls. The controller 310 then increases the number recorded by the counter 320 corresponding to the bin by one. Figure 3 In the example, the time t sAt the time t e That is, TD1 expires after all carriers generated by the radiation particles drift out of the radiation absorption layer 110. If the time t cannot be easily measured e , TD1 can be selected empirically to allow sufficient time to collect substantially all of the carriers generated by the radiation particle, but TD1 cannot be too long, otherwise there is a risk that another carrier generated by the incident radiation particle will be collected. That is, TD1 can be selected empirically so that time t s At time t e After that. Time t s Not necessarily at time t e Afterwards, since once V2 is reached, the controller 310 may ignore TD1 and wait for time t e Therefore, the rate of change of the difference between the voltage and the dark current contribution to the voltage is e The controller 310 may be configured to disable the second voltage comparator 302 upon expiration of TD1 or at time t2 or any time in between.

[0064] At time t e The voltage of is proportional to the number of carriers generated by the irradiated particle, which is related to the energy of the irradiated particle. The controller 310 may be configured to use the voltmeter 306 to determine the energy of the irradiated particle.

[0065] After TD1 expires or is digitized by the voltmeter 306 (whichever is later), the controller connects the electrical contact 118B to electrical ground for a reset period RST to allow the carriers accumulated on the electrical contact 119B to flow to ground and reset the voltage. After RST, the electronic system 121 is ready to detect another incident radiation particle. If the first voltage comparator 301 is disabled, the controller 310 can activate it at any time before the expiration of RST. If the controller 310 is disabled, it can be activated before the expiration of RST.

[0066] Figure 4A-4F The flowchart of the method for manufacturing the radiation detector 100 according to the embodiment is schematically shown. Figure 4A The process is schematically shown starting from a substrate having an insulating layer 103 and a semiconductor layer 117 attached to the insulating layer 103. In an example, the semiconductor layer 117 may be heavily doped silicon.

[0067] Figure 4BThe first and second sets of electrodes 119A and 119B are schematically shown to be formed by etching through the entire thickness of the semiconductor layer 117. As shown in previous examples, the first set of electrodes 119A may or may not have the same shape or structure as the second set of electrodes 119B.

[0068] Figure 4C The semiconductor particles 116 are schematically shown to be introduced into the gap between the first set of electrodes 119A and the second set of electrodes 119B. For example, the gap can be filled with a slurry containing semiconductor particles 116 distributed in a fluid, which will be removed later. The semiconductor particles 116 may include GaAs, CdTe, CZT or a combination thereof. The semiconductor particles 116 may include other suitable semiconductors. In an example, the semiconductor particles 116 are fused. After fusion, at least some of the semiconductor particles 116 may become polycrystalline semiconductors. After fusion, there may still be gaps between the semiconductor particles 116.

[0069] Figure 4D The semiconductor layer 117 (now comprising the first set of electrodes 119A and the second set of electrodes 119B) bonded to the electronics layer 120 is schematically shown. Figure 4E It is schematically shown that after bonding, the first set of electrodes 119A is electrically connected to the first set of electrical contacts 118A, and the second set of electrodes 119B is electrically connected to the second set of electrical contacts 118B. A plurality of chips may be bonded to the same electronics layer 120 , wherein each chip comprises the radiation absorbing layer 110 .

[0070] Figure 4F It is schematically shown that the insulating layer 103 may be removed after bonding.

[0071] The radiation detector 100 described above may be used in various systems, such as the system provided below.

[0072] Figure 5 A system 9000 including the radiation detector 100 described herein is schematically shown. The system can be used for medical imaging, such as chest radiation radiography, abdominal radiation radiography, etc. The system includes a radiation source 1201. The radiation emitted from the radiation source 1201 penetrates an object 1202 (e.g., a human body part such as a chest, a limb, an abdomen), is attenuated to varying degrees by the internal structure of the object 1202 (e.g., bones, muscles, fat, organs, etc.), and is projected to the system 9000. The system 9000 forms an image by detecting the intensity distribution of the radiation.

[0073] Figure 6A system 9000 including the radiation detector 100 described herein is schematically shown. The system can be used for medical imaging such as dental radiation radiography. The system includes a radiation source 1301. Radiation emitted from the radiation source 1301 penetrates an object 1302 that is part of the oral cavity of a mammal (e.g., a human). The object 1302 may include the maxilla, the upper jaw, the teeth, the mandible, or the tongue. The radiation is attenuated to varying degrees by different structures of the object 1302 and projected to the system 9000. The system 9000 forms an image by detecting the intensity distribution of the radiation. Teeth absorb more radiation than caries, infections, and periodontal ligaments. The radiation dose received by dental patients is typically small (approximately 0.150 mSv for a full mouth series).

[0074] Figure 7 A cargo scanning or non-intrusive inspection (NII) system 9000 including the radiation detector 100 described herein is schematically shown. The system can be used for luggage inspection at public transportation stations or airports. The system includes a radiation source 1501. Radiation emitted from the radiation source 1501 can penetrate a piece of luggage 1502, be attenuated to varying degrees by the contents of the luggage, and be projected to the system 9000. The system 9000 forms an image by detecting the intensity distribution of the transmitted radiation. The system can reveal the contents of the luggage and identify prohibited items on public transportation, such as firearms, narcotics, sharp objects, and flammable items.

[0075] Figure 8 A whole body scanner system 9000 including the radiation detector 100 described herein is schematically shown. The whole body scanner system 9000 can detect metal or non-metal objects on a person for security inspection without physically removing clothing or making physical contact. The whole body scanner system includes a radiation source 1601. Radiation emitted from the radiation source 1601 can be backscattered from a person 1602 being inspected and objects thereon, and projected to the system 9000. The objects and the human body can backscatter radiation differently. The system 9000 forms an image by detecting the intensity distribution of the backscattered radiation. The radiation source 1601 of the system 9000 can be configured to scan a person in a linear or rotational direction.

[0076] Fig. 9A radiation computed tomography (radiation CT) system 9000 is schematically shown. The radiation CT system uses computer-processed radiation to produce tomographic images (virtual "slices") of specific areas of the scanned object. The tomographic images can be used for diagnostic and therapeutic purposes in various medical disciplines, or for flaw detection, failure analysis, metrology, assembly analysis, and reverse engineering. The radiation CT system includes the radiation detector 100 and the radiation source 1701 described herein, and the radiation detector 100 and the radiation source 1701 can be configured to rotate synchronously along one or more circular or spiral paths.

[0077] The radiation detector 100 described herein may also have other applications, such as radiation telescopes, mammography, industrial radiation defect detection, radiation microscopy or radiation microphotography, radiation casting inspection, radiation nondestructive testing, radiation weld inspection, radiation digital subtraction angiography, etc. It may be suitable to use the system 9000 instead of photographic film, photographic film, PSP film, radiation image intensifier, scintillator or another semiconductor radiation detector.

[0078] Although various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for illustrative purposes and are not intended to be limiting, and the true scope and spirit of the invention should be determined by the claims herein.

Claims

1. A radiation detector comprising: an electronics layer including a first set of electrical contacts and a second set of electrical contacts; a radiation absorbing layer configured to absorb radiation; a first set of electrodes and a second set of electrodes, wherein the first set of electrodes and the second set of electrodes intersect each other and extend into the radiation absorbing layer along a thickness direction thereof; wherein the electronics layer and the radiation absorbing layer are combined such that the first set of electrodes are electrically connected to the first set of electrical contacts and the second set of electrodes are electrically connected to the second set of electrical contacts, The radiation detector further includes an insulating layer at a surface of the radiation absorbing layer remote from the electronics layer; wherein the first set of electrodes and the second set of electrodes are connected to the insulating layer, wherein the distance between one electrode of the first set of electrodes and the nearest electrode of the second set of electrodes does not exceed 2λ, where λ is the mean free path of carriers in the radiation absorbing layer, The electronic device layer includes a plurality of voltage sources and a plurality of electronic systems, wherein the plurality of voltage sources provide non-zero voltages to the first set of electrical contacts respectively, and the plurality of electronic systems are connected to the second set of electrical contacts respectively. 2 . The radiation detector of claim 1 , wherein the radiation absorbing layer comprises GaAs, CdTe, CZT, or a combination thereof. 3 . The radiation detector of claim 1 , wherein the first set of electrodes and the second set of electrodes comprise metal or semiconductor. 4 . The radiation detector of claim 1 , wherein the first set of electrodes and the second set of electrodes are configured to be differentially biased.

5. The radiation detector of claim 1, wherein the second set of electrodes are cylindrical. The radiation detector of claim 1 , wherein the second set of electrodes are prismatic in shape.

7. The radiation detector of claim 1, wherein the first set of electrodes comprises a grid.

8. The radiation detector of claim 1, wherein the second set of electrodes are discrete.

9. The radiation detector of claim 1, wherein the first set of electrodes and the second set of electrodes are coextensive in the thickness direction.

10. The radiation detector of claim 1, wherein the radiation absorbing layer comprises a polycrystalline semiconductor.

11. The radiation detector of claim 1 , wherein the electronics layer is configured to bias the first set of electrodes and the second set of electrodes to different voltages through the first set of electrical contacts and the second set of electrical contacts.

12. The radiation detector of claim 1, wherein the radiation is X-rays.

13. The radiation detector of claim 1, Wherein the electronic device layer comprises: a first voltage comparator configured to compare a voltage of the second set of electrical contacts to a first threshold; a second voltage comparator configured to compare the voltage to a second threshold; a counter configured to record the number of radiation particles received by the radiation absorbing layer; a controller, wherein the controller is configured to initiate a time delay when the absolute value of the voltage is determined from the first voltage comparator to be equal to or exceeds the absolute value of the first threshold; wherein the controller is configured to enable the second voltage comparator during the time delay; The controller is configured to increase the number recorded by the counter by one if the second voltage comparator determines that the absolute value of the voltage is equal to or exceeds the absolute value of the second threshold.

14. The radiation detector of claim 13, further comprising an integrator electrically connected to the electrical contacts, wherein the integrator is configured to collect carriers from the electrical contacts.

15. The radiation detector of claim 13, wherein the controller is configured to enable the second voltage comparator upon initiation or expiration of the time delay.

16. The radiation detector of claim 13, wherein the controller is configured to connect the electrical contact to electrical ground.

17. The radiation detector of claim 13, wherein the rate of change of the voltage is substantially zero upon expiration of the time delay.

18. The radiation detector of any one of claims 1 to 17, wherein the first set of electrodes and the second set of electrodes are the same semiconductor material.

19. A method of manufacturing a radiation detector, comprising: obtaining a substrate having an insulating layer and a semiconductor layer attached to the insulating layer; forming a first set of electrodes and a second set of electrodes from the semiconductor layer by etching through the thickness of the semiconductor layer; introducing semiconductor particles between the first set of electrodes and the second set of electrodes; combining the semiconductor layer with an electronic device layer including a first set of electrical contacts and a second set of electrical contacts such that the first set of electrodes is electrically connected to the first set of electrical contacts and the second set of electrodes is electrically connected to the second set of electrical contacts, wherein the distance between one electrode of the first set of electrodes and the nearest electrode of the second set of electrodes does not exceed 2λ, where λ is the mean free path of charge carriers across the semiconductor particles, The electronic device layer includes a plurality of voltage sources and a plurality of electronic systems, wherein the plurality of voltage sources provide non-zero voltages to the first set of electrical contacts respectively, and the plurality of electronic systems are connected to the second set of electrical contacts respectively, The first group of electrodes and the second group of electrodes are made of the same semiconductor material.

20. The method of manufacturing a radiation detector of claim 19, wherein the semiconductor particles include GaAs, CdTe, CZT, or a combination thereof.

21. The method of manufacturing a radiation detector as claimed in claim 19, wherein the introducing semiconductor particles between the first set of electrodes and the second set of electrodes comprises fusing the semiconductor particles.

22. The method of manufacturing a radiation detector of claim 19, wherein the first set of electrodes and the second set of electrodes are configured to be differentially biased.

23. The method of manufacturing a radiation detector of claim 19, wherein the second set of electrodes are cylindrical.

24. The method of manufacturing a radiation detector of claim 19, wherein the second set of electrodes are prismatic in shape.

25. The method of manufacturing a radiation detector of claim 19, wherein the first set of electrodes comprises a grid.

26. The method of manufacturing a radiation detector of claim 19, wherein the second set of electrodes are discrete.

27. The method of manufacturing a radiation detector of claim 19, wherein the electronics layer is configured to bias the first set of electrodes and the second set of electrodes to different voltages through the first set of electrical contacts and the second set of electrical contacts.

28. The method of manufacturing a radiation detector of claim 19, further comprising removing the insulating layer.

Images