A small pixel array detector with Schottky floating electrodes

Abstract

The present invention discloses a small pixel array detector with a Schottky floating electrode, relating to the field of semiconductor device technology. The detector comprises a detector body, wherein an anode and a floating electrode are provided on the top surface of the detector body, and a cathode is provided on the bottom surface of the detector body. The anode is an array pixel electrode. The floating electrode comprises an edge grid, a common grid, and a guard ring. The edge grid is positioned around the array pixel electrode, the guard ring is positioned around each pixel electrode in the array, and the common grid is positioned between each guard ring. The small pixel array detector with a Schottky floating electrode proposed in the present invention can effectively prevent carriers from being collected by metal electrodes other than the anode pixel electrode, thereby reducing charge loss. Moreover, unlike conventional guard ring electrode structures, the Schottky floating electrode structure can form a surface transverse electric field without applying pressure, thereby reducing carrier injection, promoting electron drift toward the anode pixel electrode, and improving charge collection efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor devices, and in particular to a small pixel array detector with Schottky floating electrodes. Background Art

[0002] At present, large-area CdZnTe pixel detectors have achieved excellent energy resolution due to their small pixel effect and depth-sensitive technology. However, charge sharing and loss will reduce the performance of semiconductor pixel detectors. In order to reduce the charge loss in the gap between the anode pixel electrodes, a common grid electrode will be added to the original pixel. By applying a negative bias to the lower surface plane electrode and the common grid, the electron cloud can be effectively promoted to drift toward the anode pixel electrode, thereby improving the charge collection efficiency. In addition, the common grid electrode and edge grid added to the original pixel can effectively reduce the surface leakage current.

[0003] However, part of the electron cloud signal will be collected at the common grid and the edge grid, resulting in charge loss. Since there are no pixels outside the edge grid to collect the external electron cloud, insufficient charge steering will result in the entire charge cloud not being completely collected by the anode pixel. Applying a higher bias voltage to the common gate can improve the steering capability and the collection performance, but this method will generate greater leakage current and more electronic noise.

[0004] Therefore, providing a pixel electrode structure with high charge collection efficiency, low leakage current and simple voltage application to improve the problems of charge sharing and charge loss in large-area CdZnTe pixel detectors is a technical problem that needs to be solved urgently in this field. Summary of the Invention

[0005] In order to solve the above problems, the present invention provides a small pixel array detector with Schottky floating electrodes.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A small pixel array detector with a Schottky floating electrode comprises a detector body, wherein the top surface of the detector body is provided with an anode and a floating electrode, and the bottom surface of the detector body is provided with a cathode;

[0008] Wherein, the anode is an array pixel electrode, forming an ohmic contact to collect charge signals;

[0009] The floating electrode includes an edge grid, a common grid and a guard ring to form a Schottky contact. The edge grid is located around the array pixel electrode, the guard ring is located around each pixel electrode of the array, and the common grid is located between each guard ring.

[0010] The Schottky floating electrode structure adopted in the present invention mainly utilizes the Schottky barrier it generates to prevent electronic signals from being collected by the common grid electrode and the edge grid electrode, which can form an automatic voltage division to generate a horizontal surface electric field, promote the drift of electrons toward the anode pixel electrode, and improve the charge collection efficiency; by reducing the size of the anode pixel electrode, its unipolarity and spatial resolution can be enhanced; by designing a number of guard ring electrodes around the reduced pixel points to form Schottky contacts, the surface leakage current increased due to the reduction of the pixel electrode can be reduced, and automatic voltage division can also be formed to promote the drift of electrons.

[0011] Preferably, when the detector is working normally, only negative voltage is applied to the cathode, which makes pressurization easier, and the bias voltage is 1000-2000V; the floating electrode on the upper surface can form automatic voltage division without external bias due to the presence of Schottky barrier until the detector is completely exhausted.

[0012] The detector structure is more convenient to apply pressure, and there is no need to apply a negative bias voltage at the common grid, which reduces the injection of carriers and avoids the increase of surface leakage current.

[0013] Preferably, the detector body is a rectangular parallelepiped, the top surface and the bottom surface are squares, the side length of the square is 8-14 mm, and the height of the rectangular parallelepiped is 5-15 mm.

[0014] Preferably, the material of the detector body is cadmium zinc telluride, and the resistivity is greater than 10 9 Ω·cm.

[0015] Preferably, each pixel electrode is square with a side length of 0.4-0.8 mm.

[0016] The detector structure of the present invention can reduce the size of the anode pixel electrode according to actual needs, enhance its unipolarity and spatial resolution, and reduce the surface leakage current increased by the reduction of the pixel electrode by designing several pixel peripheral guard ring electrodes.

[0017] Preferably, the protective ring is in the shape of a square ring, the number is 1-3, and the width of each square ring is 0.05-0.1 mm;

[0018] The distance between the pixel electrode and the guard ring is not less than 0.02 mm.

[0019] Preferably, the distance between the outer ring of the protective ring and the common grid and the edge grid is not less than 0.05 mm.

[0020] Preferably, the width of the common grid is 0.05-0.1 mm, and the width of the edge grid is 0.4-0.6 mm.

[0021] Preferably, the material of the pixel electrode is any one of Au, Cr, In and Au / Cr alloy materials;

[0022] The floating electrode is made of Al or Au.

[0023] Preferably, the cathode is a planar electrode, and the material of the cathode is any one of Au, Cr, In and Au / Cr alloy materials.

[0024] Preferably, the cathode, the floating electrode and the anode are prepared by electron beam evaporation, and then heat treated to form the required electrode contacts.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) Due to the presence of the potential barrier, the detector structure of the present invention forms a potential distribution in which the potential is highest at the pixel electrode and lowest at the floating electrode. This potential distribution is conducive to the collection of charges by the anode, reducing charge loss;

[0027] (2) The electric field at the floating electrode of the detector structure of the present invention is the highest, followed by the pixel electrode. This is because the floating electrode automatically divides the voltage to form a higher electric field to promote the drift of carriers to the anode pixel, thereby improving the charge collection efficiency.

[0028] (3) The Schottky floating electrode structure proposed in the present invention can effectively prevent carriers from being collected by metal electrodes other than the anode pixel electrode, thereby reducing charge loss. Different from the previous guard ring electrode structure, the Schottky floating electrode structure can form a surface transverse electric field without applying pressure, thereby reducing the injection of carriers and avoiding the increase of surface leakage current. At the same time, it promotes the drift of electrons toward the anode pixel electrode, thereby improving the charge collection efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. The drawings in this description are merely embodiments of the present invention.

[0030] Figure 1 A top view of the structure of the detector proposed by the present invention;

[0031] Figure 2 This is a schematic diagram of the three-dimensional structure of the detector proposed by the present invention from an oblique upward perspective;

[0032] Figure 3 This is a schematic diagram of the three-dimensional structure of the detector proposed by the present invention from an oblique downward perspective;

[0033] Figure 4 A schematic diagram of the detector potential distribution is proposed for the present invention;

[0034] Figure 5 The present invention proposes a schematic diagram of the one-dimensional potential distribution of the detector at X=0 on the upper surface;

[0035] Figure 6 A schematic diagram of the electric field distribution of the detector is proposed for the present invention;

[0036] Figure 7 The present invention proposes a schematic diagram of the one-dimensional electric field distribution of the detector at X=0 on the upper surface;

[0037] Figure 8 A schematic diagram of the electron concentration distribution in the two-dimensional cross section of the detector is provided for the present invention;

[0038] Figure 9 The present invention proposes a one-dimensional electron concentration distribution curve diagram of the detector at X=0 on the upper surface. DETAILED DESCRIPTION

[0039] The following describes embodiments of the present invention, examples of which are shown in the accompanying drawings. The embodiments described with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but are not to be construed as limiting the present invention.

[0040] Example 1

[0041] like Figure 1-3 The present invention provides a small pixel array detector with a Schottky floating electrode:

[0042] The detector body comprises a detector main body, wherein the top surface of the detector main body 1 is provided with an anode and a floating electrode, and the bottom surface of the detector main body 1 is provided with a cathode 3;

[0043] Among them, the anode is an array pixel electrode 2 (5*5 arranged in an array in row and column directions);

[0044] The floating electrode includes an edge grid 4, a common grid 5 and a guard ring 6. The edge grid 4 is located around the array pixel electrode, the guard ring 6 is located around each pixel electrode 2 of the array, and the common grid 5 is located between each guard ring 6.

[0045] The cathode 3 is a planar electrode made of Au;

[0046] The detector body 1 is a rectangular parallelepiped, with the top and bottom surfaces being squares, the side length of the square being 9.55 mm, and the height of the rectangular parallelepiped being 15 mm;

[0047] The material of the detector body 1 is cadmium zinc telluride, with a resistivity of about 10 9 Ω·cm;

[0048] Each pixel electrode 2 is square with a side length of 0.61 mm;

[0049] The shape of the protective ring 6 is a square ring, and the width of each square ring is 0.1 mm;

[0050] The distance between the pixel electrode 2 and the guard ring 6 is 0.21 mm;

[0051] The distance between the outer ring of the protection ring 6 and the common grid 5 and the edge grid 4 is 0.2 mm;

[0052] The width of the common grid 5 is 0.1 mm, and the width of the edge grid 4 is 0.5 mm.

[0053] The material of the pixel electrode 2 is Au;

[0054] The floating electrode is made of Al;

[0055] The cathode 3, floating electrode and anode are prepared by electron beam evaporation, and the electron beam coating device is matched with a specific mask and then heat treated to form the required electrode contacts;

[0056] Figure 4 and 5 Schematic diagram of the detector potential distribution of this embodiment and a schematic diagram of the one-dimensional potential distribution at X=0 on the upper surface. As can be seen from the figure: due to the presence of the Schottky barrier, a potential distribution is formed with the highest potential at the pixel electrode and the lowest potential at the floating electrode. This potential distribution is conducive to charge collection by the anode, reducing charge loss and enhancing unipolarity.

[0057] Figure 6 and 7 Schematic diagram of the electric field distribution of the detector of this embodiment and the one-dimensional electric field distribution at X=0 on the top surface. As can be seen from the figure: the electric field is highest at the floating electrode of the detector structure, followed by the pixel electrode. This is because the floating electrode automatically divides the voltage to form a higher electric field, promoting the drift of carriers to the anode pixel, thereby improving the charge collection efficiency.

[0058] Figure 8 and Figure 9 Figure 2 shows the electron concentration distribution in the two-dimensional cross section of the detector according to this embodiment, and the one-dimensional electron concentration distribution curve at X=0 on the top surface. As can be seen from the figure, the electron concentration at the Schottky floating electrode on the top surface of the detector is about two orders of magnitude lower than that at the pixel electrode. This indicates that the potential barrier at the floating electrode effectively blocks electrons from entering this area, reducing charge loss and improving charge collection efficiency.

[0059] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A small pixel array detector with Schottky floating electrodes, characterized in that: The detector comprises a detector body, wherein the top surface of the detector body is provided with an anode and a floating electrode, and the bottom surface of the detector body is provided with a cathode; Wherein, the anode is an array pixel electrode; The floating electrode includes an edge grid, a common grid and a guard ring to form a Schottky contact. The edge grid is located around the array pixel electrode, the guard ring is located around each pixel electrode in the array, and the common grid is located between each of the guard rings. The spacing between the pixel electrode and the guard ring is not less than 0.02 mm. The spacing between the outer ring of the guard ring and the common grid and the edge grid is not less than 0.05 mm.

2. The small pixel array detector with Schottky floating electrodes according to claim 1, characterized in that: The detector body is a rectangular parallelepiped, the top surface and the bottom surface are squares, the side length of the square is 8-14 mm, and the height of the rectangular parallelepiped is 5-15 mm.

3. The small pixel array detector with Schottky floating electrodes according to claim 1, characterized in that: The material of the detector body is cadmium zinc telluride, with a resistivity greater than 10 9 Ω·cm.

4. The small pixel array detector with Schottky floating electrodes according to claim 1, characterized in that: Each pixel electrode is square, with a side length of 0.4-0.8 mm.

5. The small pixel array detector with Schottky floating electrodes according to claim 1, characterized in that: The protective rings are in the shape of square rings, the number of the protective rings is 1-3, and the width of each square ring is 0.05-0.1 mm.

6. The small pixel array detector with Schottky floating electrodes according to claim 1, characterized in that: The width of the common grid is 0.05-0.1 mm, and the width of the edge grid is 0.4-0.6 mm.

7. The small pixel array detector with Schottky floating electrodes according to claim 1, characterized in that: The material of the pixel electrode is any one of Au, Cr, In and Au / Cr alloy; The floating electrode is made of Al or Au.

8. The small pixel array detector with Schottky floating electrodes according to claim 1, characterized in that: The cathode is a planar electrode, and the material of the cathode is any one of Au, Cr, In and Au / Cr alloy materials.

9. The small pixel array detector with Schottky floating electrodes according to claim 1, characterized in that: The cathode, the floating electrode and the anode are prepared by electron beam evaporation, and then heat treatment is performed to form the required electrode contacts.

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