JP2000164913A - Radiation detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To apply a sufficient bias voltage to a radiation sensitive layer. SOLUTION: A radiation sensitive layer 3 wherein a carrier is directly generated by an incident radiation comprises three division sensitive layers 3a-3c, stuck together, separated by internal electrodes 6a and 6b for applying bias voltage, with the carrier acceleration electric field applied sequentially, in time shard manner, to each of division sensitive layers 3a-3c from a surface electrode 4 side instead of to the entire radiation sensitive layer 3. Since, the bias voltage applied to each of electrodes 4, 6a, and 6b is lower compared to when it is applied to the entire radiation sensitive layer at always, a sufficient bias voltage is eventually applied to the radiation sensitive layer 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for producing carriers (electrons or holes) directly on a radiation-sensitive layer by incident radiation.
Is related to a direct conversion type radiation detection device in which
In particular, the present invention relates to a technique for applying a sufficient bias voltage to a radiation-sensitive layer.

[0002]

2. Description of the Related Art In recent years, in the medical X-ray apparatus, so-called indirect conversion type radiation detection apparatuses and direct conversion type radiation detection apparatuses have become popular as alternatives to conventional image intensifiers and ionization chamber type X-ray detectors. Is being considered. In the case of the former indirect conversion type, after the incident radiation is first converted to light in the radiation conversion layer, this converted light is converted to an electrical signal in the photoelectric conversion layer, but in the case of the latter direct conversion type, The configuration is such that incident radiation is directly converted into an electric signal without being converted into light.

In a conventional direct conversion type radiation detecting apparatus, as shown in FIG. 8, a front surface electrode 52 and a carrier collecting electrode 53 are formed on the front and back surfaces of a radiation sensitive layer 51, respectively. Va is applied, and carriers (electrons or holes) are extracted from the carrier collection electrode 53. That is, the carriers generated in the radiation-sensitive layer 51 by the incident radiation are composed of the carrier collection electrode 53, the lower electrode 54, and the capacitor layer (for example, SiO ₂ layer) 55 by the carrier accelerating electric field by applying the bias voltage Va. The carriers accumulated in the capacitor Ca are quickly collected and stored, and the carriers stored in the capacitor Ca are taken out of the carrier collection electrode 53 via a thin film transistor (TFT) 56 at an appropriate time.

[0004]

However, in the case of the conventional direct conversion type radiation detecting apparatus, there is a problem that it is difficult to apply a sufficient bias voltage to the radiation sensitive layer 51. In order to ensure sufficient radiation detection efficiency, the radiation-sensitive layer 51 is made thicker so that incident radiation is
Must be well absorbed. In order to secure an S / N ratio in radiation detection, the electric field for carrier acceleration in the radiation-sensitive layer 51 must be increased. In order to satisfy the need to generate a strong carrier accelerating electric field in such a thick radiation-sensitive layer 51, an extremely high bias voltage Va must be applied to the surface electrode 52.

However, when the bias voltage Va applied to the surface electrode 52 becomes extremely high, noise due to discharge between the electrodes increases, and a circuit element for collecting carriers (for example, TF
Since another problem such as destruction of T) or an increase in the cost of a bias voltage supply power supply is caused, it is difficult to apply a sufficient bias voltage to the radiation sensitive layer 51 in reality.

An object of the present invention is to provide a direct conversion type radiation detecting apparatus capable of applying a sufficient bias voltage to a radiation sensitive layer in view of the above circumstances.

[0007]

According to a first aspect of the present invention, there is provided a radiation detecting apparatus, wherein electrodes are formed on the front and back surfaces of a radiation-sensitive layer in which carriers are generated by the incidence of radiation. In the radiation detection apparatus, a bias voltage is applied to one electrode (surface electrode) and carriers are taken out from the other electrode (carrier collection electrode). At least one internal electrode for applying a bias voltage is provided extending so as to partition the radiation-sensitive layer, and a carrier accelerating electric field is applied to each of the radiation-sensitive layers divided by the internal electrode. Is applied to each electrode so that electric field application scanning is performed in order from the section sensitive layer on the surface electrode side to the section sensitive layer on the carrier collection electrode side. And a voltage application control means for controlling the bias voltage application.

According to a second aspect of the present invention, in the radiation detecting apparatus according to the first aspect, the internal electrode is a mesh-shaped or stripe-shaped metal electrode.

According to a third aspect of the present invention, in the radiation detecting device according to the first aspect, the internal electrode is a thin film impurity semiconductor layer electrode.

[0010] Further, the invention of claim 4 is based on claims 1 to 3.
In the radiation detection device according to any one of the above, while the internal electrodes are provided in a number of stages in the radiation-sensitive layer, all the division sensitive layers in the radiation-sensitive layer, a plurality of continuous in the thickness direction of the radiation-sensitive layer They are divided into groups, and are configured so that electric field application scanning by voltage application control means is performed simultaneously and in parallel for each group.

[Operation] Next, the operation when a bias voltage is applied to the radiation sensitive layer when radiation is detected by the radiation detection apparatus of the present invention will be described. In the radiation detecting apparatus according to the first aspect of the present invention, the radiation-sensitive layer has a configuration in which a number of divisionally-sensitive layers separated by internal electrodes for applying a bias voltage are stacked, and the bias voltage is controlled by the voltage application control means. By the application control, the electric field for carrier acceleration is
Rather than always being applied to the entire radiation sensitive layer,
It is applied to each section sensitive layer in order from the surface electrode side (electric field application scanning is performed). Of course, the carriers generated in the divisionally responsive layer due to the incidence of the radiation move quickly to the carrier collecting electrode with the generation of the carrier acceleration electric field by the application of the bias voltage.

As described above, in the radiation detecting apparatus according to the first aspect, the electric field for accelerating the carrier having the required strength is not always applied to the entire radiation sensitive layer, but is much smaller than the thickness of the entire radiation sensitive layer. The only requirement is that a carrier accelerating electric field having the required strength is applied to each of the divided sensitive layers in order. The strength of the electric field for carrier acceleration is proportional to the bias voltage and inversely proportional to the thickness of the sensitive layer. Therefore, the bias voltage required only to apply the carrier acceleration electric field of the required strength to each section sensitive layer is smaller than the bias voltage required to apply the same carrier acceleration electric field to the entire radiation sensitive layer. , Resulting in a much lower voltage.

In the radiation detecting apparatus according to the second aspect of the present invention, carriers generated in the divisionally sensitive layer due to the incidence of the radiation quickly pass through the meshes of the metal electrodes, which are the internal electrodes, or the gaps between the stripes. Move toward.

In the radiation detecting apparatus according to the third aspect of the present invention, carriers generated in the divisionally sensitive layer by the incidence of the radiation pass through the thin film of the impurity semiconductor layer electrode, which is the internal electrode, and move to the carrier collecting electrode.

In the radiation detecting apparatus according to a fourth aspect of the present invention, all of the divided sensitive layers divided by the multi-stage internal electrodes are divided into a plurality of groups extending along the thickness direction of the radiation sensitive layer, and voltage application control means is provided. Are applied simultaneously for each group. In other words, carrier movement proceeds simultaneously in all groups. If the carrier accelerating electric field goes through the grouping sensitive layers one by one, the electric field applying scanning of one cycle ends and the next cycle starts. Therefore, the scanning of the electric field applying scanning is compared with the case where all the grouping sensitive layers are not grouped at all. If the speed is the same, the cycle period of the electric field application scanning becomes short, and the generated carrier is quickly applied with the carrier accelerating electric field. If the cycle period of the electric field application scanning is the same, the scanning speed becomes long, and the bias is increased. The application of the voltage may be performed at a low speed.

[0016]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram illustrating a basic configuration of a main part of a radiation detection apparatus according to an embodiment, and FIG. 2 is a partial plan view illustrating a shape of an internal electrode of the embodiment. The radiation detection apparatus shown in FIG. 1 includes a radiation sensor unit 1 that converts incident radiation into a carrier, and a voltage application control unit 2 that controls application of a bias voltage applied to the radiation sensor unit 1.

The radiation sensor unit 1 is, as shown in FIG.
A radiation-sensitive layer 3 in which carriers are generated by the incidence of radiation, a front electrode (one electrode) 4 and a carrier collection electrode (the other electrode) 5 provided on the front and back surfaces of the radiation-sensitive layer 3, It has two internal electrodes 6 a and 6 b for applying a bias voltage, which are arranged in the layer 3. Since both internal electrodes 6a and 6b extend entirely in the surface direction of the radiation-sensitive layer 3, the radiation-sensitive layer 3 is stacked by the two internal electrodes 6a and 6b in the thickness direction. 3c.

The radiation sensor section 1 includes a carrier extracting thin film transistor (TFT) 7 connected to the carrier collecting electrode 5 and a capacitor Ca formed below the carrier collecting electrode 5. The capacitor Ca includes a collecting electrode 5 and a capacitor layer (for example, an SiO ₂ layer) 9 disposed between the lower electrode 8 and the electrodes 5 and 8.

The radiation sensitive layer 3 of the radiation sensor unit 1 is, for example, an amorphous selenium (a-Se) layer. The total thickness of the radiation-sensitive layer 3 varies depending on the number of the divided sensitive layers and the like, but is generally up to about 1 mm, and the thickness of the divided sensitive layer is, for example, about 50 to 100 microns per layer. In the case of the embodiment, the radiation-sensitive layer 3 has three divisionally sensitive layers having the same thickness, but the total number of the divisionally sensitive layers is not limited to the specific three layers. In addition, the thickness of each of the divided sensitive layers does not necessarily have to be the same.

The surface electrode 4, the carrier collection electrode 5, and the lower electrode 8 are, for example, metal electrodes such as gold having a thickness of about several hundred angstroms. The internal electrodes 6a and 6b are electrodes made of metal such as gold or aluminum. As shown in FIG. 2, the metal lines 6A are formed in a square lattice (mesh) running vertically and horizontally. The metal line 6
A may be a stripe shape running only in one of the vertical and horizontal directions. The ratio (Lb / La) between the width La of the metal line 6A and the width Lb of the gap 6B between the metal lines 6A in the internal electrodes 6a and 6b of this embodiment is not limited to a specific value, but, for example, Lb / La = If it is about 10, a mesh through which the carrier easily passes will be obtained. Specifically, the internal electrodes 6a, 6b
Has a thickness of, for example, about several μm to several hundred μm,
The width La of A is about 1 μm, and the gap Lb between the metal lines 6A is about 10 μm. It is preferable that these values be determined by experiments.

On the other hand, as shown in FIG. 1, the voltage application control section 2 controls a power supply control section 11 for controlling a period of generation of a bias voltage applied to each electrode and a voltage for outputting a bias voltage in accordance with a command signal of the power supply control section 11. The voltage generator 12a is wired to supply a bias voltage to the surface electrode 4, the voltage generator 12b is wired to supply a bias voltage to the internal electrode 6a, and the voltage generator 12c Are wired to supply a bias voltage to the internal electrode 6b.

The manner in which the voltage application controller 2 controls the application of the bias voltage will be described below with reference to the drawings. FIG.
Is a graph showing the voltage state of each electrode by the voltage generation units 12a to 12c in comparison with the state of the electric field E for carrier acceleration in the divisionally sensitive layers 3a to 3c.

With the start of radiation detection, as shown in the first stage (uppermost stage) of FIG. 4, the voltage generator 12a starts to apply the bias voltage Vb to the surface electrode 4, and thereafter holds the same. Further, as shown in the second stage of FIG. 4, the voltage generator 12b applies the bias voltage Vb to the internal electrode 6a when the period Ta has elapsed from the start of the radiation detection, and further, as shown in the third stage of FIG. The bias voltage Vb is applied to the internal electrode 6a.
The voltage generator 12c applies the bias voltage Vb to the internal electrode 6b at the point in time when the period Ta has elapsed since the start of application of. When the period Ta has elapsed since the start of the application of the bias voltage Vb to the internal electrode 6b, the voltage generators 12b and 12c stop outputting the bias voltage Vb, and once reduce the voltage of the internal electrodes 6a and 6b to zero volt. After returning, after the elapse of the period Ta, the output operation of the same bias voltage Vb is repeated again as shown in the second and third stages of FIG.

On the other hand, each of the voltage generators 12a-1
According to the output operation of the bias voltage Vb by 2c, the carrier accelerating electric field E is applied to the section sensitive layer 3a for the period Ta during which the bias voltage Vb is applied only to the front surface electrode 4, as shown in the fourth stage of FIG. In the division sensitive layer 3b, as shown in the fifth row of FIG. 4, a period Ta during which the bias voltage Vb is applied to the surface electrode 4 and the internal electrode 6a is applied.
Only the carrier accelerating electric field E is applied and the division sensitive layer 3
In FIG. 4C, as shown in the sixth stage (bottom stage) of FIG. 4, the carrier acceleration electric field E is applied only during the period Ta during which the bias voltage Vb is applied to the surface electrode 4 and the internal electrodes 6a and 6b. While the radiation detection operation is being performed, the electric field application scan cycle in which the carrier accelerating electric field E is sequentially applied to the divisionally sensitive layers 3a to 3c is repeatedly performed.

The above-mentioned period Ta is determined, for example, so that the electric field E for carrier acceleration moves from 50 .mu.SEC to 200 .mu.SEC to the next section sensitive layer. The bias voltage Vb is a + (plus) voltage when the carrier to be accelerated is a hole, and − when the carrier to be accelerated is an electron.
(Minus) voltage. Incidentally, in the case of the embodiment in which the radiation-sensitive layer 3 is an amorphous selenium (a-Se) layer,
Since the carrier to be accelerated is a hole, the bias voltage V
b is a positive voltage.

Further, as shown in FIG. 3, the radiation sensor section 1 of the embodiment has a surface sensor configuration in which a large number of detecting elements 1a are arranged along the X and Y directions (for example, 1024 × 1024). The radiation sensor unit 1 shown in FIG. 1 shows a configuration just for one detection unit 1a.
As shown in FIG. 3, the surface electrode 4 and the internal electrodes 6a, 6
b is formed on the entire surface as a common electrode, but the carrier collection electrode 5 is formed separately as an individual electrode for each detection element 1a, and one thin film transistor 7 is formed for each detection element 1a. In the radiation sensor unit 1,
As shown in FIG. 3, the thin film transistor 7 of the detection element 1a
Are connected to the horizontal (X) direction readout wiring 13,
The gate is connected to the readout wiring 14 in the vertical (Y) direction. The read wiring 13 is connected to a multiplexer 16 via a preamplifier group 15 and the read wiring 1
4 is connected to the gate driver 17. In the preamplifier group 15, one preamplifier 15a as shown in FIG.

In the case of the radiation sensor section 1, a scanning signal for extracting a carrier is sent to the multiplexer 16 and the gate driver 17. The identification of each detection element 1a of the radiation sensor unit 1 is performed based on the addresses (for example, 0 to 1023) sequentially assigned to each detection element 1a along the array in the X direction and the Y direction. Are signals for specifying an X-direction address or a Y-direction address, respectively. As a voltage for taking out is applied from the gate driver 17 to the readout wiring 14 in the Y direction according to the scanning signal in the Y direction, each detection element 1a is selected in a column unit. Then, by switching the multiplexer 16 according to the scanning signal in the X direction, the carriers (electrons or carriers) accumulated in the capacitor Ca of the detection element 1a in the selected column are sequentially transferred to the preamplifier group 15 and the multiplexer 1
6 and will be taken out.

From the above, it can be said that the method of taking out the carrier from the radiation sensor section 1 has a configuration similar to that of a general video device such as a TV camera. In the case of the embodiment, a preamplifier group 15, a multiplexer 16, a gate driver 17 and, if necessary, an AD converter (not shown) are provided around the radiation sensor unit 1.
The structure is further integrated. However, all or a part of the preamplifier group 15, the multiplexer 16, the gate driver 17, the AD converter, and the like may be configured separately from the radiation sensor unit 1.

When the radiation sensor unit 1 of the radiation detecting apparatus according to the embodiment is manufactured, the insulating substrate 10 made of glass or the like is used.
The lower electrode 8, the capacitor layer 9, the carrier collecting electrode 5, the thin film transistor 7, the divisionally sensitive layers 3a to 3c, and the internal electrodes are formed on the surface of the substrate by using a thin film forming technique by various vacuum evaporation methods or a patterning technique by photolithography. 6a,
6b, the surface electrode 4 and the like are sequentially laminated.

Next, a description will be given of the movement of the carrier due to the supply of a bias voltage to the radiation sensitive layer when radiation is detected in the radiation detector of the embodiment having the above-described configuration. FIG. 5 is a schematic diagram illustrating a movement state of the carrier H occurring in the radiation-sensitive layer 3 with the electric field application scanning. When the radiation detection is started, as shown in the fourth stage in FIG. 4, the carrier accelerating electric field E is applied to the section sensitive layer 3a only during the period Ta during which the bias voltage Vb is supplied only to the surface electrode 4.
As shown in FIG. 5 (a), the carriers H generated in the divisionally sensitive layer 3a move quickly to the next divisionally sensitive layer 3b through the mesh of the internal electrode 6a.

Subsequently, as shown in the fifth stage of FIG. 4, the carrier accelerating electric field E is applied to the section sensitive layer 3b only during the period Ta during which the bias voltage Vb is applied to the surface electrode 4 and the internal electrode 6a. As shown in FIG. 5 (b), the carrier H generated in the divisionally sensitive layer 3b passes through the mesh of the internal electrode 6b together with the carrier H that has moved from the divisionally sensitive layer 3a and immediately moves to the next divisionally sensitive layer 3c. I will do it. Subsequently, as shown in the sixth stage (bottom stage) of FIG. 4, the carrier accelerating electric field E is applied to the divisionally sensitive layer 3c only during the period Ta during which the bias voltage Vb is applied to the surface electrode 4 and the internal electrodes 6a and 6b. As a result, as shown in FIG. 5C, the carriers H generated in the divisionally sensitive layers 3c move below the carrier collecting electrodes 5 together with the carriers H that have moved from the divisionally sensitive layers 3a and 3b. Thereafter, while the radiation detection is continued, the above-described situations of FIGS. 5A to 5C are repeated, and during that time, the accumulated carriers are taken out (read) at an appropriate timing.

As described above, in the radiation detecting apparatus of the embodiment, the electric field for accelerating the carrier is not applied to the entire radiation-sensitive layer 3, but is applied to each of the section-sensitive layers 3a to 3a.
c is applied in order from the surface electrode side, so that the bias voltage Vb required to apply a carrier accelerating electric field E having a necessary strength to one of the divided sensitive layers 3a to 3c.
Requires a much lower voltage than the conventional bias voltage Va required to apply the carrier accelerating electric field E of the required strength to the entire radiation-sensitive layer 3, and as a result, It is possible to apply an appropriate bias voltage.

Conventionally, the entire radiation-sensitive layer 3 has a thickness of 7000
Since the bias voltage Va of about 10,000 V is applied, the bias voltage Vb in the case of the embodiment in which the total number of the divisionally sensitive layers is 3 is around 2500 to 3000 V. Of course, the bias voltage Vb decreases as the total number of the divisionally sensitive layers increases, and when the total number of divisionally sensitive layers becomes 10, the bias voltage Vb decreases to about 700 to 1000 V. Further, in the case of the embodiment, since the carriers move quickly through the meshes of the metal electrodes as the internal electrodes 6a and 6b, a sufficient amount of the carriers are collected on the carrier collecting electrode 5, and the sufficient detection efficiency is obtained. Can be secured.

Next, a radiation detecting apparatus according to another embodiment of the present invention will be described with reference to the drawings. FIG. 6 is a schematic diagram showing a state of applying a bias voltage to each electrode and a state of a carrier accelerating electric field in a radiation detecting apparatus according to another embodiment.
In the radiation detection device of another embodiment, as shown in FIG.
The radiation-sensitive layer 3 is provided with four internal electrodes 6a to 6d, and the radiation-sensitive layer 3 has five section-sensitive layers 3a to 3e.
Are stacked, and as described below, all the divided sensitive layers 3a to 3e are divided into two groups G1 and G2 that continue along the thickness direction of the radiation sensitive layer. Since the configuration is the same as that of the previous embodiment except that the electric field application scanning by the voltage application control unit 2 is performed simultaneously and in parallel for each G2, only the different parts will be described, and the description of the common parts will be omitted. Omitted.

That is, in the case of the device of another embodiment, the divisionally sensitive layers 3a to 3c constitute a group G1, and the divisionally sensitive layers 3d and 3e constitute a group G2. Then, during the period Ta after the start of the radiation detection, as shown in FIG. 6A, in the case of the group G1, the bias voltage Vb is supplied only to the surface electrode 4, and as a result, the carrier acceleration is applied to the divisionally sensitive layer 3a. In the case of the group G2, the bias voltage Vb is supplied only to the internal electrode 6c, and as a result, the carrier accelerating electric field E is applied to the divisionally sensitive layer 3d. Therefore, the carriers generated in the division sensitive layer 3a are
a, the carrier immediately moves to the next section-sensitive layer 3b, and the carriers generated in the section-sensitive layer 3d quickly move to the next section-sensitive layer 3e through the internal electrode 6c.

In the next period Ta, as shown in FIG. 6B, in the case of the group G1, the surface electrode 4 and the internal electrode 6
a is supplied with the bias voltage Vb, so that the divided sensitive layer 3
b, a carrier accelerating electric field E is applied. In the case of group G2, the bias voltage Vb is supplied to the internal electrodes 6c and 6d. As a result, the carrier accelerating electric field E is applied to the divisionally sensitive layer 3e. Therefore, the carriers generated in the divisionally sensitive layer 3b pass through the internal electrode 6b together with the carriers that have moved from the divisionally sensitive layer 3a, and immediately move to the next divisionally sensitive layer 3c, and the carriers generated in the divisionally sensitive layer 3e are separated. The carrier moves under the carrier collecting electrode 5 together with the carrier moving from the sensitive layer 3d and is accumulated.

In the next period Ta, as shown in FIG. 6C, in the case of the group G1, the bias voltage Vb is supplied to the surface electrode 4 and the internal electrodes 6a and 6b, so that the carrier is supplied to the divisionally sensitive layer 3c. When the acceleration electric field E is applied and the group G2, the bias voltage V is applied to the internal electrodes 6c and 6d.
b is not supplied, and no carrier accelerating electric field E is applied to the divisionally sensitive layers 3d and 3e. Therefore, the carriers generated in the divisionally responsive layers 3c pass through the internal electrodes 6c and move to the next divisionally responsive layer 3d promptly together with the carriers that have moved from the divisionally sensitive layers 3a, 3b.
In e, carrier movement does not occur.

Thereafter, while the radiation detection continues, the electric field application scanning shown in FIGS. 6A to 6C is repeated, and during that time, the accumulated carriers are taken out at an appropriate timing. Will be. However, in the case of the second and subsequent cycle electric field application scans excluding the first electric field application scan cycle, in the region of the group G2, the group G1
And the carriers generated in the group G2 move to the carrier collection electrode 5 together.

As described above, in the case of the radiation detecting apparatus of the other embodiment, all of the divided sensitive layers 3a to 3e are divided into two groups G1 and G2, and the electric field for carrier acceleration is changed to the group G1 by electric field application scanning. , G2, the order is one, the one cycle of electric field application scanning ends and the next cycle starts. Therefore, compared to the case where all the division sensitive layers 3a to 3e are not grouped at all, the electric field application scanning is not performed. If the scanning speed is the same, the cycle period of the electric field application scanning becomes short, and the generated carriers are quickly collected by the carrier collection electrode 5.
Is reached. If the cycle period of the electric field application scanning is the same, the scanning speed becomes longer and the bias voltage V
Since the application control of b may be performed at a low speed, it is easy to implement.

In FIGS. 5 and 6, for convenience of explanation, the voltage of the carrier collecting electrode 5 is shown as zero volt, but actually, the lower electrode 8 is at zero volt, and the carrier generated in the radiation sensitive layer 3 is the carrier. While the thin film transistor 7 accumulating under the collecting electrode 5 is shut off, the carrier collecting electrode 5 is not connected to the outside and the carrier collecting electrode 5
Is exactly a voltage slightly above or slightly below zero volts.

The present invention is not limited to the above embodiment, but can be modified as follows. (1) In the radiation detection apparatus of the embodiment, the internal electrode is a mesh-shaped or striped metal electrode. However, a modified example is a device in which the internal electrode is a thin-film impurity semiconductor layer electrode. . As the impurity semiconductor layer electrode, a semiconductor layer of a type opposite to that of the radiation sensitive layer is used. For example, when the radiation-sensitive layer is pure Se, the radiation-sensitive layer is considered to be N-type. Therefore, as the impurity semiconductor layer electrode, P-type antimony sulfide (Sb ₂ S ₃ ),
Alternatively, arsenic selenide (As ₂ Se) is used. The impurity semiconductor layer electrode has an extremely small thickness, for example, about several hundred angstroms to about 1 μm. In the case of this modification, carriers move through the thin film of the impurity semiconductor layer electrode toward the carrier collection electrode, so that it is not necessary to pattern the thin film of the impurity semiconductor layer with a mesh or stripe pattern.

(2) In each of the above embodiments, the bias voltage applied to the surface electrode and the internal electrode was a constant voltage.
A different bias voltage may be applied to each electrode. Hereinafter, description will be made with reference to FIG. In this example, an intermediate bias voltage MV having a value between the bias voltage Vb and the ground potential is applied to the internal electrodes 6a and 6b. That is, in FIG. 7A, the bias voltage V
b, applying the intermediate bias voltage MV to each of the internal electrodes 6a to move the carriers of the divisionally sensitive layer 3a toward the divisionally sensitive layer 3b. Subsequently, in FIG. 7B, the bias voltage Vb is applied to the surface electrode 4 and the internal electrode 6a, and the intermediate bias voltage MV is applied to the internal electrode 6b, and the carriers of the divisionally sensitive layer 3b are moved toward the divisionally sensitive layer 3c. Let it. Further, in FIG. 7C, the bias voltage Vb is applied to all of the surface electrode 4 and the internal electrodes 6a and 6b without applying the intermediate bias voltage MV, and the carriers of the divisionally sensitive layer 3c are moved to the side of the carrier collection electrode 5. Has been moved to. Hereinafter, FIGS. 7A to 7C are repeatedly executed in the same manner. In order to obtain a large electric field with a small bias voltage, it is advantageous that the absolute value of the potential difference between the intermediate bias voltage MV and the ground potential is considerably smaller than the absolute value of the potential difference between the bias voltage Vb and the ground potential. It is believed that there is.

(3) In the radiation detecting apparatus of the embodiment, the radiation sensitive layer is formed of selenium. However, as a modified example, a radiation sensitive layer is formed of CdZnTe.

[0044]

As described above in detail, according to the radiation detecting apparatus of the first aspect of the present invention, the radiation sensitive layer is formed by superposing several divided sensitive layers separated by the internal electrode for applying the bias voltage. The structure is such that the carrier accelerating electric field is not applied to the entire radiation-sensitive layer, but is applied to each of the divided sensitive layers in order from the surface electrode side. Since the bias voltage required to apply the carrier acceleration electric field of this type is much lower than the bias voltage required to apply the carrier acceleration electric field of the required strength to the entire radiation-sensitive layer, Thus, a sufficient bias voltage can be applied to the radiation-sensitive layer.

Further, according to the radiation detecting apparatus of the second aspect of the present invention, the carriers move quickly through the meshes of the metal electrodes, which are the internal electrodes, or the gaps between the stripes. A quantity of career is collected.

According to the radiation detecting apparatus of the third aspect of the present invention, since carriers move through the thin film of the impurity semiconductor layer electrode which is the internal electrode, the thin film of the impurity semiconductor layer is practically meshed. This eliminates the need for patterning in the shape of stripes or stripes.

Further, according to the radiation detecting apparatus of the present invention, all the division sensitive layers of the radiation sensitive layer are divided into a plurality of groups which follow along the thickness direction, and the electric field for carrier acceleration is divided into the division sensitive layers of the group. If the scanning speed of the electric field application scanning is the same as compared with the case where all the divided sensitive layers are not grouped at all, the electric field application scanning of one cycle ends and the next cycle starts. The cycle period of the applied scan becomes shorter, the generated carriers can quickly reach the carrier collection electrode, and if the cycle period of the electric field applied scan is the same, the scanning speed becomes longer,
The control of the application of the bias voltage may be performed at a low speed, and the control becomes easy.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a basic configuration of a main part of a radiation detection apparatus according to an embodiment.

FIG. 2 is a partial plan view showing the shape of an internal electrode of the device according to the embodiment.

FIG. 3 is a plan view illustrating a configuration of a radiation sensor unit of the example device.

FIG. 4 is a graph showing a voltage state of each electrode of the example apparatus and a state of a carrier accelerating electric field of each section sensitive layer.

FIG. 5 is a schematic view showing a carrier moving state occurring in the radiation-sensitive layer of the apparatus of the embodiment.

FIG. 6 is a schematic diagram showing a voltage state of each electrode and a state of a carrier accelerating electric field of each divisionally sensitive layer according to another embodiment.

FIG. 7 is a schematic diagram showing a modification of bias voltage application.

FIG. 8 is a block diagram showing a basic configuration of a main part of a conventional radiation detection device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Radiation sensor part 2 ... Voltage application control part 3 ... Radiation sensitive layer 3a-3e ... Division sensitive layer 4 ... Surface electrode 5 ... Carrier collection electrode 6a-6d ... Internal electrode 7 ... Thin film transistor 12a-12c ... Voltage generation part E ... Electric field for carrier acceleration G1, G2 ... group Vb ... bias voltage

Claims (4)

[Claims] An electrode is formed on each of the front and back surfaces of a radiation-sensitive layer in which carriers are generated by the incidence of radiation, and a bias voltage is applied to one electrode (front electrode) and the other electrode (front electrode). In a radiation detection device configured to take out carriers from a carrier collection electrode, an internal electrode for applying a bias voltage, which extends in the surface direction of the radiation-sensitive layer and is arranged so as to partition the radiation-sensitive layer, is provided. While having at least one,
An electric field application scan is performed in which a carrier accelerating electric field is sequentially applied to each of the radiation-sensitive layers of the radiation-sensitive layer divided by the internal electrode from the surface-electrode-side radiation-sensitive layer to the carrier collection electrode-side radiation-sensitive layer. A radiation detection apparatus comprising voltage application control means for controlling application of a bias voltage to each electrode. 2. The radiation detecting apparatus according to claim 1, wherein the internal electrode is a mesh-shaped or stripe-shaped metal electrode. 3. The radiation detecting apparatus according to claim 1, wherein the internal electrode is a thin film impurity semiconductor layer electrode. 4. The radiation detecting apparatus according to claim 1, wherein the internal electrodes are provided in a plurality of stages on the radiation sensitive layer, and all of the radiation sensitive layers in the radiation sensitive layer are radiation sensitive. A radiation detection device which is divided into a plurality of groups that continue along a thickness direction of a layer, and is configured so that electric field application scanning by voltage application control means is performed simultaneously and in parallel for each group.