A double PN junction X-ray irradiation scintillator detector

Abstract

The present invention belongs to the field of radiation detection technology, and specifically relates to a double PN junction X-ray irradiation scintillator detector. The detector provided by the present invention comprises a first PN junction, a tunnel junction, and a second PN junction connected in sequence, a scintillator and a P-type electrode are provided at the end of the first PN junction, and an N-type electrode is provided at the end of the second PN junction; the scintillator is a cadmium tungstate scintillator, the first PN junction is a PN junction of an InGaP-based material, and the second PN junction is a PN junction of a GaAs-based material. The detector of the present invention has the advantages of high light utilization, low heat generation, and strong high-temperature stability, and is particularly suitable for use in extreme environments such as space exploration.

Description

Technical Field

[0001] The invention belongs to the technical field of radiation detection, and specifically relates to a double PN junction X-ray irradiation scintillator detector, and in particular to a GaAs / InGaP double PN junction X-ray irradiation scintillator detector structure. Background Art

[0002] The structure of X-ray scintillator detector is mainly composed of scintillator and semiconductor detector. When X-rays are irradiated on the scintillator layer, the scintillator layer absorbs the X-rays and generates photons. When the X-rays are irradiated on the detector, the photoelectric effect of the PN junction is used to generate photogenerated carriers, which are affected by the built-in electric field and collected by the electrodes at both ends.

[0003] Silicon semiconductor materials are widely used in detectors, but actual use may involve high-temperature radiation environments, which can easily cause detector failure. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a double PN junction X-ray irradiation scintillator detector.

[0005] The double PN junction X-ray irradiation scintillator detector provided by the present invention comprises a first PN junction, a tunnel junction, and a second PN junction connected in sequence, a scintillator and a P-type electrode are provided at the end of the first PN junction, and an N-type electrode is provided at the end of the second PN junction; the scintillator is a cadmium tungstate scintillator, the first PN junction is a PN junction of an InGaP-based material, and the second PN junction is a PN junction of a GaAs-based material.

[0006] Further, the first PN junction includes a first electron blocking layer, a first P-type absorption layer, a first N-type absorption layer and a first hole blocking layer connected in sequence;

[0007] The first electron blocking layer material is (Al 0.7 Ga 0.3 ) 0.5 In 0.5 P, doped to P type;

[0008] The first P-type absorption layer material is In 0.5 Ga 0.5 P, doped to P type;

[0009] The first N-type absorption layer material is In 0.5 Ga 0.5 P, doped to N type;

[0010] The first hole blocking layer material is (Al 0.7 Ga 0.3 ) 0.5 In 0.5 P, doped to N type.

[0011] Further, as a preferred solution of the double PN junction X-ray irradiation scintillator detector:

[0012] The thickness of the first electron blocking layer is 8~12nm;

[0013] The thickness of the first P-type absorption layer is 80~120nm;

[0014] The thickness of the first N-type absorption layer is 400~600nm;

[0015] The thickness of the first hole blocking layer is 40-60 nm.

[0016] Further, as a preferred solution of the double PN junction X-ray irradiation scintillator detector:

[0017] The P-type doping concentration of the first electron blocking layer is 2e19cm -3 ;

[0018] The P-type doping concentration of the first P-type absorption layer is 2e18cm -3 ;

[0019] The N-type doping concentration of the first N-type absorption layer is 2e18cm -3 ;

[0020] The N-type doping concentration of the first hole blocking layer is 2e19cm -3 .

[0021] Further, the second PN junction includes a second electron blocking layer, a second P-type absorption layer, a second N-type absorption layer and a second hole blocking layer connected in sequence;

[0022] The second electron blocking layer material is In 0.5 Ga 0.5 P, doped to P type;

[0023] The second P-type absorption layer is made of GaAs and is doped into P-type;

[0024] The second N-type absorption layer is made of GaAs and doped to N-type;

[0025] The second hole blocking layer material is Al 0.7 Ga 0.3 As, doped to N type.

[0026] Further, as a preferred solution of the double PN junction X-ray irradiation scintillator detector:

[0027] The thickness of the second electron blocking layer is 36~50nm;

[0028] The thickness of the second P-type absorption layer is 400~600nm;

[0029] The thickness of the second N-type absorption layer is 1600~2400nm;

[0030] The thickness of the second hole blocking layer is 80-120 nm.

[0031] Further, as a preferred solution of the double PN junction X-ray irradiation scintillator detector:

[0032] The P-type doping concentration of the second electron blocking layer is 2e19cm -3 ;

[0033] The P-type doping concentration of the second P-type absorption layer is 2e18cm -3 ;

[0034] The N-type doping concentration of the second N-type absorption layer is 2e18cm -3 ;

[0035] The N-type doping concentration of the second hole blocking layer is 2e19cm -3 .

[0036] Further, the tunnel junction includes a tunnel junction N-type portion and a tunnel junction P-type portion;

[0037] The N-type part of the tunnel junction is made of GaAs with a thickness of 16-25 nm and is doped with N-type at a concentration of 5e19 cm -3 .

[0038] The P-type material of the tunnel junction is GaAs, with a thickness of 16~25nm, and is doped to P type with a concentration of 5e19 cm -3 .

[0039] Furthermore, the P-type electrode at the end of the first PN junction is 25-35 nm thick Cr superimposed on 10-16 nm thick Ni superimposed on 1000-1500 nm thick Au;

[0040] A buffer layer is connected to the end of the second PN junction, and an N-type electrode is connected to the buffer layer; the N-type electrode is Cr with a thickness of 25-35 nm superimposed on Ni with a thickness of 10-16 nm superimposed on Au with a thickness of 1000-1500 nm.

[0041] Furthermore, a transparent adhesive is used to adhere the scintillator to the surface of the first electron blocking layer, and the adhesive is cured to form an adhesive body that wraps the scintillator.

[0042] Beneficial Effects

[0043] 1. The detector of the present invention uses cadmium tungstate as a scintillator and cooperates with a GaAs / InGaP-based double PN junction structure to form a good energy band matching relationship, thereby improving the overall utilization rate of cadmium tungstate luminescence and greatly improving the efficiency of photoelectric conversion.

[0044] 2. The energy bands of the scintillator cadmium tungstate and the GaAs / InGaP-based double PN junction are highly matched, which significantly reduces the relaxation of photogenerated carriers after absorbing high-energy photons, significantly reduces heat release, and suppresses the heating of the detector.

[0045] 3. GaAs / InGaP materials have better radiation resistance and high temperature resistance than traditional Si-based materials. They have stable EQE at high temperatures and high breakdown voltage, making them particularly suitable for extreme environments such as space exploration. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a schematic diagram of the structure of a double PN junction X-ray irradiation scintillator detector.

[0047] Figure 2 This is the EQE absorption of the detector and the X-ray excitation band diagram of the cadmium tungstate scintillator.

[0048] Figure 3 This is the graph of the detector's EQE absorption varying with temperature. DETAILED DESCRIPTION

[0049] Example 1

[0050] A double PN junction X-ray irradiation scintillator detector, the structure of which is as follows Figure 1 As shown, from top to bottom, it includes a scintillator 1, an adhesive 2, a P-type electrode 3, a first electron blocking layer 4, a first P-type absorption layer 5, a first N-type absorption layer 6, a first hole blocking layer 7, a tunnel junction N-type portion 8, a tunnel junction P-type portion 9, a second electron blocking layer 10, a second P-type absorption layer 11, a second N-type absorption layer 12, a second hole blocking layer 13, a buffer layer 14, and an N-type electrode 15.

[0051] The scintillator 1 is made of cadmium tungstate material. Cadmium tungstate as a scintillator material has the characteristics of high light output and low afterglow, forms an excited state under the irradiation of X-rays, and releases photons to form a "scintillation" phenomenon when the excited state is de-excited.

[0052] The scintillator 1 is adhered to the surface of the first electron blocking layer 4 by using a transparent adhesive, and the adhesive body 2 wrapping the scintillator 1 is formed after the adhesive is cured.

[0053] The first electron blocking layer 4 , the first P-type absorption layer 5 , the first N-type absorption layer 6 and the first hole blocking layer 7 together form a first PN junction structure.

[0054] The material of the first electron blocking layer 4 is (Al 0.7 Ga 0.3 ) 0.5 In 0.5P, thickness is 10nm, doped as P type, concentration is 2e19cm -3 .

[0055] The material of the first P-type absorption layer 5 is In 0.5 Ga 0.5 P, thickness is 100nm, doped as P type, concentration is 2e18cm -3 .

[0056] The material of the first N-type absorption layer 6 is In 0.5 Ga 0.5 P, thickness is 500nm, doped as N-type, concentration is 2e18cm -3 .

[0057] The material of the first hole blocking layer 7 is (Al 0.7 Ga 0.3 ) 0.5 In 0.5 P, thickness is 50nm, doped as N-type, concentration is 2e19cm -3 .

[0058] The second electron blocking layer 10 , the second P-type absorption layer 11 , the second N-type absorption layer 12 and the second hole blocking layer 13 together form a second PN junction structure.

[0059] The material of the second electron blocking layer 10 is In 0.5 Ga 0.5 P, thickness 40nm, doped to P type, concentration 2e19cm -3 ;

[0060] The second P-type absorption layer 11 is made of GaAs, has a thickness of 500 nm, and is doped to P-type with a concentration of 2e18 cm -3 ;

[0061] The second N-type absorption layer 12 is made of GaAs, has a thickness of 2000 nm, and is doped to N-type with a concentration of 2e18 cm -3 ;

[0062] The material of the second hole blocking layer 13 is Al 0.7 Ga 0.3 As, thickness is 100nm, doped as N-type, concentration is 2e19cm -3 .

[0063] The tunnel junction N-type part 8 and the tunnel junction P-type part 9 form a tunnel junction connected between two PN junctions. The tunnel junction uses the quantum tunneling effect to transfer electrons, and connecting between two PN junctions can prevent the formation of an inverse PN junction at the connection.

[0064] The tunnel junction N-type part 8 is made of GaAs with a thickness of 20 nm and is doped with N-type at a concentration of 5e19 cm -3 .

[0065] The tunnel junction P-type part 9 is made of GaAs with a thickness of 20 nm and is doped to P-type with a concentration of 5e19 cm -3 .

[0066] The buffer layer 14 uses GaAs material as the substrate, has a thickness of 200nm, is doped as N-type, and has a concentration of 1e18cm -3 .

[0067] The P-type electrode 3 is connected to the top of the first PN junction in a strip shape. The material of the P-type electrode 3 is Cr / Ni / Au (30 / 13 / 1200nm), that is, 30nm thick Cr, 13nm thick Ni and 1200nm thick Au are plated on the first electron blocking layer 4 in sequence to form an electrode.

[0068] The N-type electrode 15 is in a thin layer connected to the bottom of the second PN junction, and its material is Cr / Ni / Au (30 / 13 / 1200nm).

[0069] The detector's scintillator 1 uses a self-made cadmium tungstate scintillator block, which is excited by X-rays in the wavelength band such as Figure 2 In addition, the absorption range of InGaP material highly matches the main luminescence peak of CdT, while the absorption range of GaAs material just forms a perfect complementary relationship with InGaP material, greatly expanding the absorption range of CdT excitation band.

[0070] The first PN junction is adjacent to the scintillator 1, absorbing the excitation light in the shorter wavelength range emitted by the scintillator 1, covering the entire main peak of the luminescence of the scintillator 1 and highly matching; the second PN junction is located below the first PN junction, absorbing the excitation light in the longer wavelength range that is not absorbed by the first PN junction.

[0071] Figure 3 The figure shows the EQE absorption band of the detector at different temperatures. As the temperature increases from 300 K to 900 K, the performance only slightly decays. In view of the failure of traditional Si-based detectors in high temperature environments, the dual PN junction X-ray irradiation scintillator detector of the present invention can effectively replace Si-based detectors for X-ray irradiation detection in extreme environments.

[0072] Example 2

[0073] A double PN junction X-ray irradiation scintillator detector, the structure of which is as follows Figure 1As shown, from top to bottom, it includes a scintillator 1, an adhesive 2, a P-type electrode 3, a first electron blocking layer 4, a first P-type absorption layer 5, a first N-type absorption layer 6, a first hole blocking layer 7, a tunnel junction N-type portion 8, a tunnel junction P-type portion 9, a second electron blocking layer 10, a second P-type absorption layer 11, a second N-type absorption layer 12, a second hole blocking layer 13, a buffer layer 14, and an N-type electrode 15.

[0074] The scintillator 1 is made of cadmium tungstate material.

[0075] The scintillator 1 is adhered to the surface of the first electron blocking layer 4 by using a transparent adhesive, and the adhesive body 2 wrapping the scintillator 1 is formed after the adhesive is cured.

[0076] The first electron blocking layer 4 , the first P-type absorption layer 5 , the first N-type absorption layer 6 and the first hole blocking layer 7 together form a first PN junction structure.

[0077] The material of the first electron blocking layer 4 is (Al 0.7 Ga 0.3 ) 0.5 In 0.5 P, thickness 12nm, doped as P type, concentration 2e19cm -3 .

[0078] The material of the first P-type absorption layer 5 is In 0.5 Ga 0.5 P, thickness 120nm, doped as P type, concentration 2e18cm -3 .

[0079] The material of the first N-type absorption layer 6 is In 0.5 Ga 0.5 P, thickness is 600nm, doped as N-type, concentration is 2e18cm -3 .

[0080] The material of the first hole blocking layer 7 is (Al 0.7 Ga 0.3 ) 0.5 In 0.5 P, thickness is 60nm, doped as N-type, concentration is 2e19cm -3 .

[0081] The second electron blocking layer 10 , the second P-type absorption layer 11 , the second N-type absorption layer 12 and the second hole blocking layer 13 together form a second PN junction structure.

[0082] The material of the second electron blocking layer 10 is In 0.5 Ga 0.5 P, thickness 50nm, doped to P type, concentration 2e19cm -3 ;

[0083] The second P-type absorption layer 11 is made of GaAs, has a thickness of 600 nm, and is doped to P-type with a concentration of 2e18 cm -3 ;

[0084] The second N-type absorption layer 12 is made of GaAs, has a thickness of 2400 nm, and is doped to N-type with a concentration of 2e18 cm -3 ;

[0085] The material of the second hole blocking layer 13 is Al 0.7 Ga 0.3 As, thickness 120nm, doped as N-type, concentration 2e19cm -3 .

[0086] The tunnel junction N-type portion 8 and the tunnel junction P-type portion 9 constitute a tunnel junction connected between two PN junctions.

[0087] The tunnel junction N-type part 8 is made of GaAs with a thickness of 25 nm and is doped with N-type at a concentration of 5e19 cm -3 .

[0088] The tunnel junction P-type part 9 is made of GaAs with a thickness of 25 nm and is doped to P-type with a concentration of 5e19 cm -3 .

[0089] The buffer layer 14 uses GaAs material as the substrate, has a thickness of 240nm, is doped as N-type, and has a concentration of 1e18cm -3 .

[0090] The P-type electrode 3 is connected to the top of the first PN junction in a strip shape. The material of the P-type electrode 3 is Cr / Ni / Au (35 / 16 / 1500nm), that is, 35nm thick Cr, 16nm thick Ni and 1500nm thick Au are plated on the first electron blocking layer 4 in sequence to form an electrode.

[0091] The N-type electrode 15 is in a thin layer connected to the bottom of the second PN junction, and its material is Cr / Ni / Au (35 / 16 / 1500nm).

[0092] Example 3

[0093] A double PN junction X-ray irradiation scintillator detector, the structure of which is as follows Figure 1 As shown, from top to bottom, it includes a scintillator 1, an adhesive 2, a P-type electrode 3, a first electron blocking layer 4, a first P-type absorption layer 5, a first N-type absorption layer 6, a first hole blocking layer 7, a tunnel junction N-type portion 8, a tunnel junction P-type portion 9, a second electron blocking layer 10, a second P-type absorption layer 11, a second N-type absorption layer 12, a second hole blocking layer 13, a buffer layer 14, and an N-type electrode 15.

[0094] The scintillator 1 is made of cadmium tungstate material.

[0095] The scintillator 1 is adhered to the surface of the first electron blocking layer 4 by using a transparent adhesive, and the adhesive body 2 wrapping the scintillator 1 is formed after the adhesive is cured.

[0096] The first electron blocking layer 4 , the first P-type absorption layer 5 , the first N-type absorption layer 6 and the first hole blocking layer 7 together form a first PN junction structure.

[0097] The material of the first electron blocking layer 4 is (Al 0.7 Ga 0.3 ) 0.5 In 0.5 P, thickness 8nm, doped as P type, concentration 2e19cm -3 .

[0098] The material of the first P-type absorption layer 5 is In 0.5 Ga 0.5 P, thickness 80nm, doped to P type, concentration 2e18cm -3 .

[0099] The material of the first N-type absorption layer 6 is In 0.5 Ga 0.5 P, thickness is 400nm, doped as N-type, concentration is 2e18cm -3 .

[0100] The material of the first hole blocking layer 7 is (Al 0.7 Ga 0.3 ) 0.5 In 0.5 P, thickness is 40nm, doped as N-type, concentration is 2e19cm -3 .

[0101] The second electron blocking layer 10 , the second P-type absorption layer 11 , the second N-type absorption layer 12 and the second hole blocking layer 13 together form a second PN junction structure.

[0102] The material of the second electron blocking layer 10 is In 0.5 Ga 0.5 P, thickness 36nm, doped to P type, concentration 2e19cm -3 ;

[0103] The second P-type absorption layer 11 is made of GaAs, has a thickness of 400 nm, and is doped to P-type with a concentration of 2e18 cm -3 ;

[0104] The second N-type absorption layer 12 is made of GaAs, has a thickness of 1600 nm, and is doped to N-type with a concentration of 2e18 cm -3;

[0105] The material of the second hole blocking layer 13 is Al 0.7 Ga 0.3 As, thickness 80nm, doped N-type, concentration 2e19cm -3 .

[0106] The tunnel junction N-type portion 8 and the tunnel junction P-type portion 9 constitute a tunnel junction connected between two PN junctions.

[0107] The tunnel junction N-type part 8 is made of GaAs with a thickness of 16 nm and is doped with N-type at a concentration of 5e19 cm -3 .

[0108] The tunnel junction P-type part 9 is made of GaAs with a thickness of 16 nm and is doped as P-type with a concentration of 5e19 cm -3 .

[0109] The buffer layer 14 uses GaAs material as the substrate, has a thickness of 160nm, is doped as N-type, and has a concentration of 1e18cm -3 .

[0110] The P-type electrode 3 is connected to the top of the first PN junction in a strip shape. The material of the P-type electrode 3 is Cr / Ni / Au (25 / 10 / 1000nm), that is, 25nm thick Cr, 10nm thick Ni and 1000nm thick Au are plated on the first electron blocking layer 4 in sequence to form an electrode.

[0111] The N-type electrode 15 is in a thin layer connected to the bottom of the second PN junction, and its material is Cr / Ni / Au (25 / 10 / 1000nm).

[0112] The above embodiments are exemplary, and their purpose is to illustrate the technical concept and features of the present invention so that people familiar with the technology in this field can understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A double PN junction X-ray irradiation scintillator detector, characterized in that: It comprises a first PN junction, a tunnel junction and a second PN junction which are connected in sequence, a scintillator (1) and a P-type electrode (3) are provided at the end of the first PN junction, and an N-type electrode (15) is provided at the end of the second PN junction; the scintillator (1) is a cadmium tungstate scintillator, the first PN junction is a PN junction of an InGaP-based material, and the second PN junction is a PN junction of a GaAs-based material.

2. The double PN junction X-ray irradiation scintillator detector according to claim 1, characterized in that: The first PN junction comprises a first electron blocking layer (4), a first P-type absorption layer (5), a first N-type absorption layer (6) and a first hole blocking layer (7) which are connected in sequence; The material of the first electron blocking layer (4) is (Al 0.7 Ga 0.3 ) 0.5 In 0.5 P, doped to P type; The material of the first P-type absorption layer (5) is In 0.5 Ga 0.5 P, doped to P type; The material of the first N-type absorption layer (6) is In 0.5 Ga 0.5 P, doped to N type; The material of the first hole blocking layer (7) is (Al 0.7 Ga 0.3 ) 0.5 In 0.5 P, doped to N type.

3. The double PN junction X-ray irradiation scintillator detector according to claim 2, characterized in that: The thickness of the first electron blocking layer (4) is 8-12 nm; The first P-type absorption layer (5) has a thickness of 80-120 nm; The thickness of the first N-type absorption layer (6) is 400-600 nm; The first hole blocking layer (7) has a thickness of 40-60 nm.

4. The double PN junction X-ray irradiation scintillator detector according to claim 2, characterized in that: The P-type doping concentration of the first electron blocking layer (4) is 2e19cm -3 ; The P-type doping concentration of the first P-type absorption layer (5) is 2e18cm -3 ; The N-type doping concentration of the first N-type absorption layer (6) is 2e18 cm -3 ; The N-type doping concentration of the first hole blocking layer (7) is 2e19cm -3 .

5. The double PN junction X-ray irradiation scintillator detector according to claim 1, characterized in that: The second PN junction comprises a second electron blocking layer (10), a second P-type absorption layer (11), a second N-type absorption layer (12) and a second hole blocking layer (13) which are connected in sequence; The material of the second electron blocking layer (10) is In 0.5 Ga 0.5 P, doped to P type; The material of the second P-type absorption layer (11) is GaAs, which is doped to be P-type; The material of the second N-type absorption layer (12) is GaAs, which is doped to N-type; The material of the second hole blocking layer (13) is Al 0.7 Ga 0.3 As, doped to N type.

6. The double PN junction X-ray irradiation scintillator detector according to claim 5, characterized in that: The second electron blocking layer (10) has a thickness of 36-50 nm; The second P-type absorption layer (11) has a thickness of 400-600 nm; The second N-type absorption layer (12) has a thickness of 1600-2400 nm; The second hole blocking layer (13) has a thickness of 80-120 nm.

7. The double PN junction X-ray irradiation scintillator detector according to claim 5, characterized in that: The P-type doping concentration of the second electron blocking layer (10) is 2e19cm -3 ; The P-type doping concentration of the second P-type absorption layer (11) is 2e18cm -3 ; The N-type doping concentration of the second N-type absorption layer (12) is 2e18cm -3 ; The N-type doping concentration of the second hole blocking layer (13) is 2e19cm -3 .

8. The double PN junction X-ray irradiation scintillator detector according to claim 1, characterized in that: The tunnel junction comprises a tunnel junction N-type portion (8) and a tunnel junction P-type portion (9); The material of the N-type part (8) of the tunnel junction is GaAs, with a thickness of 16-25 nm, and is doped to N-type with a concentration of 5e19 cm -3 ; The tunnel junction P-type part (9) is made of GaAs, has a thickness of 16-25 nm, and is doped to a P-type with a concentration of 5e19 cm -3 .

9. The double PN junction X-ray irradiation scintillator detector according to claim 1, characterized in that: The P-type electrode (3) at the end of the first PN junction is composed of Cr with a thickness of 25 to 35 nm and Ni with a thickness of 10 to 16 nm, and Au with a thickness of 1000 to 1500 nm; A buffer layer (14) is connected to the end of the second PN junction, and an N-type electrode (15) is connected to the buffer layer (14); the N-type electrode (15) is 25-35 nm thick Cr superimposed on 10-16 nm thick Ni superimposed on 1000-1500 nm thick Au.

10. The double PN junction X-ray irradiation scintillator detector according to claim 1, characterized in that: The scintillator (1) is adhered to the surface of the first electron blocking layer (4) using a transparent adhesive, and after the adhesive is cured, an adhesive body (2) that wraps the scintillator (1) is formed.

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