CN-122029458-A - Radiation detection element, radiation detector, and method for manufacturing radiation detection element

Abstract

The invention provides a radiation detection element, a radiation detector and a method for manufacturing the radiation detection element, wherein the energy measurement of radiation can be performed with good precision. A radiation detection element includes a compound semiconductor crystal substrate formed of cadmium zinc telluride to which indium is added as an impurity, and a metal electrode provided on a surface of the compound semiconductor crystal substrate, and has an energy resolution of 7% or less for gamma rays of 122keV emitted from 57 Co.

Inventors

• Tsumura Ryusuke

Assignees

• ＪＸ金属株式会社

Dates

Publication Date

20260512

Application Date

20240910

Priority Date

20240122

Claims (11)

1. 1. A radiation detecting element, comprising: compound semiconductor crystal substrate formed of cadmium zinc telluride doped with indium as impurity, and A metal electrode provided on the surface of the compound semiconductor crystal substrate, The radiation detection element has an energy resolution of 7% or less for gamma rays of 122keV emitted from 57 Co.
2. 2. The radiation detecting element according to claim 1, wherein, The energy resolution for the 122keV gamma rays emitted from 57 Co is 5% or less.
3. 3. The radiation detecting element according to claim 1, wherein, The energy resolution for the 122keV gamma rays emitted from 57 Co is 3.4% or less.
4. 4. The radiation detecting element according to claim 1, wherein, The ideal coefficient n of the IV characteristic is 1.0-1.5.
5. 5. The radiation detecting element according to claim 1, wherein, The resistivity at the working voltage of 500V is more than 1 multiplied by 10 11 ohm cm.
6. 6. A radiation detector, comprising: The radiation detecting element according to any one of claims 1 to 5, and And an amplifying unit connected to the radiation detecting element and amplifying an electric signal output from the radiation detecting element.
7. 7. A method of manufacturing a radiation detection element, comprising: A step of slicing a wafer from an ingot containing a compound semiconductor crystal of cadmium zinc telluride to which indium is added as an impurity, and polishing the wafer; forming a metal electrode on the surface of the wafer; A step of cutting out the radiation detection element from the wafer on which the metal electrode is formed, and And (3) placing the radiation detection element into an annealing furnace, and annealing for 10 minutes to 24 hours at a temperature of 100 to 200 ℃.
8. 8. A method of manufacturing a radiation detection element, comprising: A step of slicing a wafer from an ingot containing a compound semiconductor crystal of cadmium zinc telluride to which indium is added as an impurity, and polishing the wafer; forming a metal electrode on the surface of the wafer; A step of annealing the wafer on which the metal electrode is formed in an annealing furnace at 100-200 ℃ for 10 minutes-24 hours, and And cutting the radiation detection element from the annealed wafer.
9. 9. The method for manufacturing a radiation detecting element according to claim 7 or 8, wherein, The radiation detection element has an energy resolution of 7% or less for gamma rays of 122keV emitted from 57 Co.
10. 10. The method for manufacturing a radiation detecting element according to claim 7, wherein, In the step of cutting out radiation detection elements from the wafer, 30 radiation detection elements are cut out from one wafer, and after the step of annealing, a standard deviation of the energy resolution of the 30 radiation detection elements is 2% or less when the energy resolution of the 122keV gamma rays emitted from 57 Co is measured under the same conditions.
11. 11. The method for manufacturing a radiation detecting element according to claim 8, wherein, In the step of cutting out radiation detection elements from the wafer, 30 radiation detection elements are cut out from one wafer, and a standard deviation of the energy resolution of the 30 radiation detection elements is 2% or less when the energy resolution of the 122keV gamma rays emitted from 57 Co is measured under the same conditions.

Description

Radiation detection element, radiation detector, and method for manufacturing radiation detection element Technical Field The present invention relates to a radiation detection element, a radiation detector, and a method of manufacturing a radiation detection element. Background In the field of application of direct conversion type radiation detection elements, development of compound semiconductors excellent in high efficiency, high resolution, and miniaturization is underway. Among them, cadmium zinc telluride (CdZnTe) as a group II-VI compound semiconductor has recently received attention as an advantageous material for use in radiation detection elements. CdZnTe has a larger atomic number than other semiconductors, and therefore has advantages of high radiation absorptivity and detection efficiency, and large band gap energy, and therefore has a small leakage current due to heat even at room temperature, and does not require a cooling device (can operate at room temperature). In a radiation detection element using a compound semiconductor crystal substrate formed of CdZnTe, it is useful to form ohmic electrodes on both sides of the substrate to operate the element in order to suppress an operating current of the element, while increasing the resistivity of the substrate. However, there is a problem that it is difficult to obtain good ohmic characteristics for a compound semiconductor crystal substrate made of CdZnTe having a large resistivity, and an operating current increases when a high voltage is applied due to an influence of a bonding state of a bonding interface between a semiconductor and an electrode. In addition, the ohmic junction failure affects not only the electrical characteristics but also the radiation spectrum characteristics. Patent document 1 proposes a compound semiconductor crystal for a radiation detection element, which is formed of cadmium zinc telluride containing 0.2 to 2.6 ppm by weight of indium as an impurity, has a product μτ (E) of electron mobility μ and electron lifetime τ of 7.85E-04cm 2/V or more, has a resistivity of 1.2e+11 Ω cm or more when a voltage of 100V is applied, and has a ratio b/a of a change amount b of a leakage current after 60 seconds from the start of bias application to a leakage current value a at the start of bias application of 56% or less, as a compound semiconductor crystal for cadmium zinc telluride having excellent radiation spectral characteristics. Prior art literature Patent literature Patent document 1 Japanese patent No. 5953116 Disclosure of Invention Problems to be solved by the invention One example of a method for forming an ohmic contact on a compound semiconductor crystal substrate made of CdZnTe having a high resistivity is to form a Pt electrode by electroless substitution plating. In the conventional Pt electrode formation by plating, there is a problem that even if an element is fabricated from a substrate having good crystal characteristics, current-voltage characteristics (hereinafter also referred to as IV characteristics) are poor, and an operating current increases under high voltage application, so that energy resolution of a radiation spectrum is deteriorated. In such a case, there is a problem that the accuracy of the energy measurement of the radiation is poor. The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a radiation detection element, a radiation detector, and a method of manufacturing the radiation detection element, which can perform energy measurement of radiation with good accuracy. Solution for solving the problem The above-mentioned technical problems are solved by the specific invention in the following (1) - (11). (1) A radiation detection element includes a compound semiconductor crystal substrate formed of cadmium zinc telluride to which indium is added as an impurity, and a metal electrode provided on a surface of the compound semiconductor crystal substrate, wherein an energy resolution of gamma rays of 122keV emitted from 57 Co is 7% or less. (2) The radiation detecting element according to (1), wherein the energy resolution for the 122keV gamma rays emitted from 57 Co is 5% or less. (3) The radiation detecting element according to the item (1) or (2), wherein the energy resolution for the gamma ray of 122keV emitted from 57 Co is 3.4% or less. (4) The radiation detecting element according to any one of (1) to (3), wherein an ideal coefficient n of IV characteristic is 1.0 to 1.5. (5) The radiation detecting element according to any one of (1) to (4), wherein the resistivity at an operating voltage of 500V is 1X 10 11. OMEGA cm or more. (6) A radiation detector comprising the radiation detecting element according to any one of (1) to (5), and an amplifying section connected to the radiation detecting element for amplifying an electric signal output from the radiation detecting element. (7) A method for manufacturing a radiat