Preparation method of N-type ultra-high-purity germanium single crystal

Abstract

The preparation method of the N-type ultra-high-purity germanium single crystal comprises the following steps: S1, carrying out zone melting on ultra-high-purity germanium by adopting a zone melting method, and carrying out low-temperature Hall detection to select a qualified product A of which the conduction type is P type and the net carrier concentration NA-ND is less than or equal to 1E10cm <-3 >; s2, adopting a normal czochralski method to grow an ultra-pure germanium crystal, carrying out a low-temperature Hall test, and selecting a region-melting dopant Y of which the conduction type is N type and the net carrier concentration NA-ND is in the range of E11-E13cm <-3 >; s3, secondary zone melting is carried out, the zone melting product A in the step S1 and the zone melting dopant Y in the step S2 are put into a quartz boat together for multiple times of zone melting, a high-purity germanium polycrystalline rod is obtained, a low-temperature Hall test is carried out, and a part with the conduction type being N type and the net carrier concentration being smaller than or equal to 2E10cm <-3 > is selected as a crystal dopant W; and S4, preparing the N-type ultra-high-purity germanium single crystal, putting the zone-melting product A in the step S1 and the crystal doping agent W in the step S3 into a crucible together, carrying out normal Czochralski crystal growth, and carrying out low-temperature Hall test to obtain the N-type ultra-high-purity germanium single crystal of which the NA-ND is less than or equal to 2E10cm <-3 >.

Description

Technical Field

[0001] The present disclosure relates to the field of crystal growth, and more specifically to a method for preparing an N-type ultra-high purity germanium single crystal. Background Art

[0002] High-purity germanium detectors have the advantages of high resolution, high detection efficiency, and strong stability for both x-rays and gamma-rays. Therefore, they have become the first choice for experimental research in nuclear physics, particle physics, and astrophysics, and have become indispensable instruments and equipment for material science, environmental monitoring, trace element analysis, security inspection, and national defense security.

[0003] The material purity requirements for high-purity germanium detectors are extremely high, and the net carrier concentration |NA-ND|≤2E10cm -3 , high purity germanium detectors can be made of P-type ultra-high purity germanium single crystals or N-type ultra-high purity germanium single crystals. However, the net carrier concentration of ultra-high purity germanium single crystals prepared by conventional methods is ≤2E10cm -3 The part is generally P-type, and the net carrier concentration of the N-type part is generally greater than 1E11 cm -3 This is due to the different purification effects of P-type and N-type impurities during the purification process. Therefore, further development is needed in the preparation method of N-type ultra-high purity germanium single crystals to obtain a net carrier concentration |NA-ND|≤2E10 cm -3 N-type ultra-high purity germanium single crystal. Summary of the invention

[0004] In view of the problems existing in the background technology, an object of the present invention is to provide a method for preparing an N-type ultra-high purity germanium single crystal, which can prepare a net carrier concentration |NA-ND|≤2E10 cm -3 N-type ultra-high purity germanium single crystal.

[0005] Thus, a method for preparing an N-type ultra-high purity germanium single crystal comprises the following steps: S1, using a zone melting method to zone melt ultra-high purity germanium, the product is subjected to low temperature Hall test, and a qualified product A is selected, whose conductivity type is P-type and net carrier concentration |NA-ND|≤1E10cm -3 ; S2, using the normal Czochralski method to grow ultra-high purity germanium crystals, and conducting low-temperature Hall tests, the conductivity type is selected as N-type, and the net carrier concentration |NA-ND| is between E11 and E13 cm -3 The range is used as the zone melting dopant Y; S3, secondary zone melting is performed, the zone melting product A of step S1 and the zone melting dopant Y of step S2 are placed in a quartz boat for multiple zone melting, and a high-purity germanium polycrystalline rod is obtained. After low-temperature Hall test, the conductivity type is selected as N type, and the net carrier concentration |NA-ND|≤2E10cm -3As the crystal dopant W; S4, prepare N-type ultra-high purity germanium single crystal, the zone melting product A of step S1 and the crystal dopant W of step S3 are put into a crucible together for normal Czochralski crystal growth, and after low-temperature Hall test, |NA-ND|≤2E10 cm -3 N-type ultra-high purity germanium single crystal.

[0006] The beneficial effects of the present disclosure are as follows: In the method for preparing an N-type ultra-high purity germanium single crystal according to the present disclosure, |NA-ND|≤1E10 cm -3 Product A, based on product A, is 1E11 cm -3 <|NA-ND|<1E13 cm -3 The zone melting dopant Y is then subjected to secondary zone melting in step S3 to obtain |NA-ND|≤2E10 cm -3 The crystal dopant W is used as a raw material for the normal Czochralski method in step S4, so that the net carrier concentration |NA-ND|≤2E10 cm in the middle and rear of the normal ultra-high purity germanium crystal obtained by the normal Czochralski method can be -3 , thus preparing |NA-ND|≤2E10 cm -3 N-type ultra-high purity germanium single crystal. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 It is a flow chart of the method for preparing N-type ultra-high purity germanium single crystal according to the present disclosure. DETAILED DESCRIPTION

[0008] It will be understood that the disclosed embodiments are merely examples of the present disclosure, which may be implemented in various forms, and therefore, the specific details disclosed herein should not be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one of ordinary skill in the art to implement the present disclosure in various ways.

[0009] [Method for preparing N-type ultra-high purity germanium single crystal]

[0010] Reference Figure 1 According to the present invention, the method for preparing an N-type ultra-high purity germanium single crystal comprises the following steps:

[0011] S1, zone melting method is used to zone melt ultra-high purity germanium. The products are tested by low temperature Hall test and qualified product A is selected. Its conductivity type is P type and net carrier concentration |NA-ND|≤1E10 cm -3 ;

[0012] S2, using the normal Czochralski method to grow ultra-high purity germanium crystals, and conducting low-temperature Hall tests, selecting N-type conductivity and net carrier concentration |NA-ND| between E11 and E13 cm -3 Range (i.e. 1E11 cm -3 <|NA-ND|<1E13 cm -3 ) as a zone melting dopant Y;

[0013] S3, secondary zone melting is performed. The zone melting product A of step S1 and the zone melting dopant Y of step S2 are placed in a quartz boat for multiple zone melting to obtain a high-purity germanium polycrystalline rod. After low-temperature Hall test, the conductivity type is selected as N type, and the net carrier concentration |NA-ND|≤2E10 cm -3 The portion of is used as a crystal dopant W;

[0014] S4, prepare N-type ultra-high purity germanium single crystal, put the zone melting product A of step S1 and the crystal dopant W of step S3 into a crucible for normal Czochralski crystal growth, and obtain |NA-ND|≤2E10 cm after low temperature Hall test. -3 N-type ultra-high purity germanium single crystal.

[0015] In the method for preparing an N-type ultra-high purity germanium single crystal according to the present disclosure, |NA-ND|≤1E10cm is obtained by step S1. -3 Product A, based on product A, is 1E11 cm -3 <|NA-ND|<1E13 cm -3 The zone melting dopant Y is then subjected to secondary zone melting in step S3 to obtain |NA-ND|≤2E10 cm -3 The crystal dopant W is used as a raw material for the normal Czochralski method in step S4, so that the net carrier concentration |NA-ND|≤2E10 cm in the middle and rear of the normal ultra-high purity germanium crystal obtained by the normal Czochralski method can be -3 , thus preparing |NA-ND|≤2E10 cm -3 N-type ultra-high purity germanium single crystal.

[0016] In one example, the zone melting process of step S1 is:

[0017] S11, loading the corroded germanium ingot with a purity of 5N or above into the zone furnace, and corroding it with a mixed solution of 68% HNO3:49% HF in a volume ratio of 1:4;

[0018] S12, introduce high-purity nitrogen gas of 7N or above through the air inlet and open the exhaust port to maintain the flow pressure at normal pressure for 2 hours;

[0019] S13, after step S12 is completed, the gas inlet is switched to allow high-purity hydrogen with a purity of 9N or above to pass for 2 hours, and the exhaust port is kept exhausted to keep the flow pressure at normal pressure;

[0020] S14, heating and heating to carry out zone melting of the chemical material, the zone melting speed is 100-200 mm / h, and the zone melting is repeated 20-30 times;

[0021] S15, after step S14 is completed, the heating is stopped, the air inlet is switched to introduce high-purity nitrogen gas of 7N or above and the exhaust port is maintained to exhaust gas to maintain normal pressure until the cooling is completed and the zone melting high-purity germanium ingot is taken out from the zone melting furnace.

[0022] In one example, the Czochralski process of step S2 comprises the following sub-steps:

[0023] S21, loading the etched 12N high-purity germanium polycrystal into a crucible of a pulling furnace, and etching using a mixed solution of 68% HNO3:49% HF in a volume ratio of 1:4;

[0024] S22, first evacuate to below 1Pa, then pass high-purity nitrogen with a purity of 7N, and purge the pulling furnace by evacuating and filling with nitrogen 3-5 times. After the purging is completed, stop evacuating and stop passing high-purity nitrogen;

[0025] S23, switching to introduce 9N high-purity hydrogen and maintaining exhaust to maintain a flowing atmosphere in the pulling furnace;

[0026] S24, raising the temperature of the pulling furnace to 950-1000° C. in a flowing atmosphere to polycrystallize the 12N high-purity germanium in the crucible into a melt;

[0027] S25, after the melting is completed, the seed crystal is lowered to 10-20 mm from the liquid surface of the melt in the crucible, and the seed crystal is preheated for 30 minutes. The net impurity carrier concentration of the seed crystal is less than 2E11 cm -3 ;

[0028] S26, start the crucible rotation and the crystal rotation in opposite directions, insert the seed crystal 2-5 mm below the liquid surface of the melt, and an aperture appears, and then seeding, necking, neck thinning, shoulder release, equal diameter, and tailing are performed, and a crystal rod is grown by pulling. When there is no residual material or only a small amount of residual material in the crucible, stop the crucible rotation and the crystal rotation, wherein the rotation speed of the crucible rotation and the crystal rotation is 1-5 rpm, and the pulling speed is 20-24 mm / h;

[0029] S27, after step S26 is completed, the temperature is naturally lowered to room temperature, the crystal turner and the crucible turner are turned off, the hydrogen is stopped, and the nitrogen gas with a purity of 7N is switched to be filled and the exhaust is maintained. Then, the nitrogen filling and exhaust are stopped, the pulling furnace is opened, and the crystal rod is cut off.

[0030] In step S2, the crystal rod (i.e., a normal ultra-high purity germanium crystal) is P-type in the first half and begins to transform into N-type in the middle and rear parts, although the net carrier concentration |NA-ND| of the N-type cannot be lower than 2E10 cm -3 However, the N-type portion can be selected and used as the zone melting dopant Y for the secondary zone melting.

[0031] In one example, the secondary zone melting process of step S3 is the same as the zone melting process of step S1 except for the raw materials.

[0032] In one example, the crystal growth process of step S4 is the same as the Czochralski process of step S2 except for the raw materials.

[0033] In one example, in step S3, the mass ratio of the zone melting product A to the zone melting dopant Y is 3000:(30-100); in step S4, the mass ratio of the zone melting product A to the crystal dopant W is 6000:(24-50).

[0034] In the method for preparing an N-type ultra-high purity germanium single crystal disclosed in the present invention, the net impurity carrier concentration and the doping type in steps S1 to S4 are detected by HL9900 of Toho Technology Company of the United States.

[0035] [test]

[0036] Example 1

[0037] Example 1 adopts the following steps:

[0038] S1, using zone melting method to zone melt ultra-high purity germanium, the product was tested by HL9900 low temperature Hall tester of Toho Technology Company of the United States, and qualified product A was selected, whose conductivity type is P type and net carrier concentration |NA-ND|≤1E10 cm -3 ,

[0039] Among them, the zone melting process of step S1 is:

[0040] S11, loading the etched 5N purity germanium ingot into the zone furnace, and etching using a mixed solution of 68% HNO3:49% HF in a volume ratio of 1:4;

[0041] S12, introduce 7N high purity nitrogen through the air inlet and open the exhaust port to maintain the flow pressure

[0042] Normal pressure, lasting 2h;

[0043] S13, after step S12 is completed, the inlet is switched to allow 9N high-purity hydrogen to pass for 2 hours, and the exhaust port is kept exhausted to keep the flow pressure at normal pressure;

[0044] S14, heating and heating to carry out zone melting of the chemical material, the zone melting speed is 150 mm / h, and the zone melting is repeated 25 times;

[0045] S15, after step S14 is completed, the heating is stopped, the air inlet is switched to 7N high-purity nitrogen and the exhaust port is maintained to exhaust gas to maintain normal pressure until the cooling is completed and the zone melting furnace is taken out.

[0046] Pure germanium ingot;

[0047] S2, using the normal Czochralski method to grow ultra-high purity germanium crystals, and conducting the HL9900 low-temperature Hall test of Toho Technology Company, USA, the conductivity type is N-type and the net carrier concentration |NA-ND| is 1.5E12 cm -3 As the zone melting dopant Y,

[0048] The CZT process of step S2 adopts the following sub-steps:

[0049] S21, loading the etched 12N high-purity germanium polycrystal into a crucible of a pulling furnace, and etching using a mixed solution of 68% HNO3:49% HF in a volume ratio of 1:4;

[0050] S22, first evacuate to 1Pa, then pass high-purity nitrogen with a purity of 7N, and purge the pulling furnace by evacuating and filling with nitrogen 4 times. After the purging is completed, stop evacuating and stop passing 7N high-purity nitrogen;

[0051] S23, switch to introduce 9N high purity hydrogen and maintain exhaust to maintain flow in the pulling furnace.

[0052] Dynamic atmosphere;

[0053] S24, raising the temperature of the pulling furnace to 980° C. in a flowing atmosphere to polycrystallize the 12N high-purity germanium in the crucible into a melt;

[0054] S25, after the melting is completed, the seed crystal is lowered to 15 mm from the liquid surface of the melt in the crucible, and the seed crystal is preheated for 30 min. The net impurity carrier concentration of the seed crystal is less than 2E11 cm -3 ;

[0055] S26, start the crucible rotation and the crystal rotation in opposite directions, insert the seed crystal into the melt surface 5mm, and the aperture appears, and then carry out seeding, necking, neck thinning, shoulder release, equal diameter, and tailing, and pull and grow the crystal rod, and only a small amount of residual material is left in the crucible, and stop the crucible rotation and the crystal rotation, wherein the rotation speed of the crucible rotation and the crystal rotation is 4rpm, and the pulling speed is 22mm / h;

[0056] S27, after step S26 is completed, the temperature is naturally lowered to room temperature, the crystal turner and the crucible turner are turned off, the hydrogen is stopped, and the nitrogen with a purity of 7N is switched to be filled and the exhaust is maintained, then the nitrogen with a purity of 7N is stopped and the exhaust is stopped, the pulling furnace is opened, and the crystal rod is cut off;

[0057] S3, secondary zone melting is performed. The zone melting product A of step S1 and the zone melting dopant Y of step S2 are put into a quartz boat at a mass ratio of 3000g:30g after etching, and zone melting is performed multiple times to obtain high-purity germanium polycrystalline rods. After the HL9900 low-temperature Hall test of Toho Technology Company in the United States, the conductivity type is selected as N type, and the net carrier concentration |NA-ND|≤2E10 cm -3 The portion of the precipitate is used as a crystal dopant W, and a mixed solution of 68% HNO3:49% HF in a volume ratio of 1:4 is used for etching. The secondary zone melting process of step S3 is the same as the zone melting process of step S1 except that the raw materials are different (i.e., the raw materials of sub-step S11 of step S1 are different);

[0058] S4, preparing N-type ultra-high purity germanium single crystal, the zone melting product A of step S1 and the crystal dopant W of step S3 are put into a crucible at a mass ratio of 6000g:24g after corrosion to carry out normal Czochralski crystal growth, and the HL9900 low temperature Hall test of Toho Technology Company of the United States is carried out to obtain 800g of |NA-ND|≤2E10 cm -3 The N-type ultra-high purity germanium single crystal is etched using a mixed solution of 68% HNO3:49% HF in a volume ratio of 1:4. The crystal growth process in step S4 is the same as the Czochralski process in step S2 except for the different raw materials (i.e., the raw materials in sub-step 21 of step S2 are different).

[0059] Example 2

[0060] Except for the following differences, the rest is the same as Example 1.

[0061] In step S3, the mass ratio is 3000g:100g;

[0062] In step S4, the mass ratio is 6000 g:50 g, and 600 g of |NA-ND|≤2E10 cm -3 N-type ultra-high purity germanium single crystal.

[0063] The above detailed description is used to describe multiple exemplary embodiments, but this document is not intended to be limited to the explicitly disclosed combinations. Therefore, unless otherwise stated, the various features disclosed herein can be combined together to form multiple additional combinations that are not shown for the sake of simplicity.

Claims

1. A method for preparing an N-type ultra-high purity germanium single crystal, characterized in that: Includes steps: S1, zone melting method is used to zone melt ultra-high purity germanium. The products are tested by low temperature Hall test and qualified product A is selected. Its conductivity type is P type and net carrier concentration |NA-ND|≤1E10 cm -3 ; S2, using the normal Czochralski method to grow ultra-high purity germanium crystals, and conducting low-temperature Hall tests, selecting N-type conductivity and net carrier concentration |NA-ND| between E11 and E13 cm -3 Range as zone melting dopant Y; S3, secondary zone melting is performed. The zone melting product A of step S1 and the zone melting dopant Y of step S2 are placed in a quartz boat for multiple zone melting to obtain a high-purity germanium polycrystalline rod. After low-temperature Hall test, the conductivity type is selected as N type, and the net carrier concentration |NA-ND|≤2E10 cm -3 The portion of is used as a crystal dopant W; S4, prepare N-type ultra-high purity germanium single crystal, put the zone melting product A of step S1 and the crystal dopant W of step S3 into a crucible for normal Czochralski crystal growth, and obtain |NA-ND|≤2E10 cm after low temperature Hall test. -3 N-type ultra-high purity germanium single crystal.

2. The method for preparing an N-type ultra-high purity germanium single crystal according to claim 1, characterized in that: The zone melting process of step S1 is: S11, loading the corroded germanium ingot with a purity of 5N or above into the zone furnace, and corroding it with a mixed solution of 68% HNO3:49% HF in a volume ratio of 1:4; S12, introduce high-purity nitrogen gas of 7N or above through the air inlet and open the exhaust port to maintain the flow pressure at normal pressure for 2 hours; S13, after step S12 is completed, the gas inlet is switched to allow high-purity hydrogen with a purity of 9N or above to pass for 2 hours, and the exhaust port is kept exhausted to keep the flow pressure at normal pressure; S14, heating and heating to carry out zone melting of the chemical material, the zone melting speed is 100-200 mm / h, and the zone melting is repeated 20-30 times; S15, after step S14 is completed, the heating is stopped, the air inlet is switched to introduce high-purity nitrogen gas of 7N or above and the exhaust port is maintained to exhaust gas to maintain normal pressure until the cooling is completed and the zone melting high-purity germanium ingot is taken out from the zone melting furnace.

3. The method for preparing an N-type ultra-high purity germanium single crystal according to claim 1, characterized in that: The CZT process of step S2 adopts the following sub-steps: S21, loading the etched 12N high-purity germanium polycrystal into a crucible of a pulling furnace, and etching using a mixed solution of 68% HNO3:49% HF in a volume ratio of 1:4; S22, first evacuate to below 1Pa, then pass high-purity nitrogen with a purity of 7N, and purge the pulling furnace by evacuating and filling with nitrogen 3-5 times. After the purging is completed, stop evacuating and stop passing high-purity nitrogen; S23, switching to introduce 9N high-purity hydrogen and maintaining exhaust to maintain a flowing atmosphere in the pulling furnace; S24, raising the temperature of the pulling furnace to 950-1000° C. in a flowing atmosphere to polycrystallize the 12N high-purity germanium in the crucible into a melt; S25, after the melting is completed, the seed crystal is lowered to 10-20 mm from the liquid surface of the melt in the crucible, and the seed crystal is preheated for 30 minutes. The net impurity carrier concentration of the seed crystal is less than 2E11 cm -3 ; S26, start the crucible rotation and the crystal rotation in opposite directions, insert the seed crystal 2-5 mm below the liquid surface of the melt, and an aperture appears, and then seeding, necking, neck thinning, shoulder release, equal diameter, and tailing are performed, and a crystal rod is grown by pulling. When there is no residual material or only a small amount of residual material in the crucible, stop the crucible rotation and the crystal rotation, wherein the rotation speed of the crucible rotation and the crystal rotation is 1-5 rpm, and the pulling speed is 20-24 mm / h; S27, after step S26 is completed, the temperature is naturally lowered to room temperature, the crystal turner and the crucible turner are turned off, the hydrogen is stopped, and the nitrogen with a purity of 7N is switched to be filled and the exhaust is maintained. Then, the nitrogen with a purity of 7N is stopped and the exhaust is stopped, the pulling furnace is opened, and the crystal rod is cut off.

4. The method for preparing an N-type ultra-high purity germanium single crystal according to claim 1, characterized in that: The secondary zone melting process of step S3 is the same as the zone melting process of step S1 except for the raw materials.

5. The method for preparing an N-type ultra-high purity germanium single crystal according to claim 1, characterized in that: The crystal growth process of step S4 is the same as the Czochralski process of step S2 except for the raw materials.

6. The method for preparing an N-type ultra-high purity germanium single crystal according to claim 1, characterized in that: In step S3, the mass ratio of the zone melting product A to the zone melting dopant Y is 3000:(30-100); In step S4, the mass ratio of the zone melting product A to the crystal dopant W is 6000:(24-50).

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