CN102230213B - Method for growing tellurium-zinc-cadmium crystals by using tellurium solvent solution method - Google Patents

Abstract

The invention relates to a device and a method for growing cadmium zinc telluride crystals by a tellurium solvent solution method, and belongs to the technical field of special crystal growth. Its features include: put high-purity Cd, Zn, and Te raw materials with a purity of 7N whose stoichiometric ratio satisfies Cd _1-x Zn _x Te (x=0.04～0.5) into a quartz crucible, and then add a mass percentage of 30% to 80% excess Te, vacuum fusion seal and synthesis in a swing furnace; put the synthesized quartz crucible into the crystal growth device, due to the addition of excess Te, the crystal growth temperature can be from 1092 ° C to 1295 ° C Drop to 700-900°C; before the crystal growth process starts, the quartz crucible is placed in a high-temperature zone, so that both the polycrystalline CdZnTe and the solvent Te are in the liquid phase, and then the furnace body is raised at a speed of 0.04-2mm/h. The temperature gradient in the temperature gradient area is 15-25°C/cm. As the temperature decreases, the saturation of CdZnTe in the solution decreases, and the bottom of the crucible is continuously saturated to precipitate CdZnTe crystals. At the same time, different donors are used for doping (In , Cl ^-1 , Al, etc.) to increase the resistivity of CdZnTe crystals, thereby preparing detector-grade CdZnTe crystals. The growth temperature of the crystal, the impurity concentration in the crystal and the defect density in the crystal are significantly reduced by adopting the invention to grow the cadmium zinc telluride crystal.

Description

Method for growing cadmium zinc telluride crystal by tellurium solvent solution method

technical field

The invention relates to a method for growing cadmium zinc telluride crystals by a tellurium solvent solution method, and belongs to the technical field of special crystal growth techniques.

Background technique

Cadmium zinc telluride Cd _1-x Zn _x Te (CZT) is a semiconductor material with broad application prospects, and the preparation of its single crystal material has been widely concerned. Because CdZnTe (CZT) single crystal has a large bandgap energy gap (Eg=1.70eV), the main components Cd and Te have high atomic numbers, high resistivity (10 ¹¹ Ω cm), and large electron and pore mobility ( μ e= 1100cm/V s, μ h=100cm/V s), wide energy detection range (10keV～6MeV), high energy resolution, high anti-neutron and proton radiation damage threshold, so the CZT detector has a large Excellent absorption coefficient, high count rate, especially it can work at room temperature without any cooling equipment, so it is smaller in size and more convenient to use. However, the growth of CdZnTe single crystal itself is difficult, and the growth of the original crystal is difficult due to various environmental factors and external environmental constraints. Usually, the crystal quality is difficult to meet the industrial standards set by general commercial users for detectors. At present, the wide application of CZT detectors is mainly limited by several aspects such as crystal performance, volume and cost. The preparation method of crystals is mainly to grow CZT crystals by high-voltage Bridgman method or improved vertical Bridgman method.

Recent studies have found that impurities in Te-rich CZT crystals are usually more likely to be enriched in Te that exists as inclusions (i.e., Te inclusions or inclusions). The adsorption of impurities keeps the impurities in the solvent, thereby improving the purity of the crystals. In addition, the crystal growth temperature can be reduced from the original 1092°C to 1295°C (varied according to the Zn composition) to 700 to 900°C, which will greatly reduce the contamination of the melt by impurities from the quartz crucible. In addition, the growth at low temperature reduces the thermal diffusion pollution of the crucible, and reduces the thermal stress, and the dislocation density is low. The tellurium solution growth method under the temperature gradient has its own advantages, the growth temperature is low, and the growth rate is faster than the moving heater method (THM), and the synthesis of polycrystalline materials and the growth of crystals are in the same quartz crucible, reducing the The impurities introduced by the secondary charging, and the process is simple, etc.

Contents of the invention

The object of the present invention is to provide a method for preparing Cd _1-x Zn _x Te (x=0.04-0.5) crystals by a tellurium solvent solution method. The invention can prepare cadmium zinc telluride crystal at the temperature of 700-900 DEG C. In the quartz crucible, more Te (rich Te30wt%~80wt%) is used as a solvent. Due to the addition of excess Te, the precipitation temperature of CdZnTe crystals is significantly lowered. With the movement of the furnace body, when the quartz crucible passes through the temperature gradient zone , as the temperature decreases, the saturation of CdZnTe in the Te solvent decreases, and CdZnTe crystals are precipitated in the saturated solution at the low temperature end, that is, CdZnTe crystals grow in the lower part of the crucible. Using the present invention to grow CdZnTe crystal significantly reduces the growth temperature of the crystal, the impurity concentration in the crystal and the defect density in the crystal, and at the same time adopts the method of donor doping to increase the resistivity of the CdZnTe crystal, thereby growing a detector level CdZnTe crystals.

The present invention adopts the following technical solutions.

A method for growing cadmium zinc telluride crystals by a tellurium solvent solution method of the present invention is characterized in that it has the following process and steps:

a. According to the stoichiometric ratio, put the high-purity Cd, Zn, and Te raw materials with a purity of 7N that satisfy x=0.04～0.5 in the chemical formula Cd _1-x Zn _x Te into a high-purity quartz crucible with an angled tip, and then Add 30% to 80% of the excess Te of the total mass of raw materials, vacuumize to 2.0×10 ^-4 Pa, and then seal the quartz crucible;

b. Put the above-mentioned quartz crucible containing CdZnTe polycrystalline material mixture into a swing furnace for synthesis reaction to obtain a mixture of CdZnTe polycrystal and solvent Te; slowly raise the temperature to 500 ° C for 3 hours, and then slowly The temperature was raised to 1000°C for 24 hours. During the heat preservation process, the swing furnace was shaken slowly to make the raw materials in the quartz crucible fully react, and then the temperature was slowly lowered to room temperature, and the synthesis was completed;

c. Put the above synthesized quartz crucible into the crystal growth furnace, set the temperature in the high temperature zone of the crystal growth furnace to 850-950°C, set the temperature in the low temperature zone to 500-600°C, and set the temperature in the temperature gradient zone to 800-900°C , and the temperature gradient in the temperature gradient zone is 15-25°C/cm; before the crystal growth process starts, keep the quartz crucible in the high temperature zone for 24 hours, so that the internal CdZnTe polycrystal and solvent Te are in the liquid phase, Adjust the furnace body, then raise the furnace body at a speed of 0.04 to 2mm/h, and at the same time ensure that the support rod remains still, which is equivalent to the quartz crucible falling at the same rate. When passing through the temperature gradient area, as the temperature decreases, the Te solvent The saturation of cadmium zinc telluride in the medium decreases. When the temperature drops to a certain level, the saturated solution at the low temperature end is saturated and precipitates cadmium zinc telluride, that is, cadmium zinc telluride crystals grow in the lower part of the crucible; when the quartz crucible passes through the entire temperature gradient area, the growth ends and the solution Most of the cadmium zinc telluride has been saturated and precipitated to form a cadmium zinc telluride ingot, and the tail is a CdZnTe-Te mixture;

d. Take out the grown crystal ingot from the quartz crucible, remove the CdZnTe-Te mixture at the tail, and the front part is the freely selected cadmium zinc telluride crystal grown by the tellurium solvent solution method. During the crystal growth process, acceptor defect Cd vacancies are easily generated, and a large number of Cd vacancies in CdZnTe crystals will greatly reduce the resistivity of the crystal, making the crystal conduct p-type. By introducing donor doping (In, Cl ^-1 , Al, etc.), recombining Cd vacancies to achieve the purpose of improving the resistivity.

The special device used in this method of growing cadmium zinc telluride crystal by Te solvent solution method includes a furnace body, a quartz crucible, and a support rod; it is characterized in that: the furnace body is a heating furnace with three temperature zones, a high temperature zone, a gradient zone and a low temperature zone, The furnace body can move vertically at a rate from 0.02 to 2mm/h, with an adjustable pace of 0.01. The temperature gradient in the growth gradient area should be between 15-25°C/cm. The upper end of the support rod is hollow, with a tapered corundum tube. Guaranteed to match the head of the quartz crucible and ensure that the quartz crucible can be stably supported.

The characteristics of the inventive method are:

The crystal growth temperature can be reduced from 1092°C to 1295°C to 700°C to 900°C, which will greatly reduce the contamination of the melt by impurities from the quartz crucible, and the synthesis of polycrystalline material and the growth of crystals in the same quartz In the crucible, the impurities introduced by the secondary charging are reduced, the process is simple, and more importantly, the quality and performance of the CdZnTe single crystal can be improved.

Description of drawings

Fig. 1 is a schematic diagram of a growth device and a growth principle for growing CdZnTe crystals by a tellurium solvent solution method.

Detailed ways

Embodiment one

The cadmium zinc telluride crystal growth of the present invention is realized by a tellurium solvent solution method.

Referring to Fig. 1, the CdZnTe crystal growth device used in the present invention comprises a furnace body 1, a quartz crucible 2, and a support rod 3: wherein the furnace body 1 is divided into three sections for heating, high temperature zone 4, temperature gradient zone 5 and low temperature zone 6 , the temperature gradient in the temperature gradient zone 5 will be between 15-25°C/cm; the raw material is packed into the quartz crucible 2 and then fused and sealed after being vacuumed; the quartz crucible 2 of the charge is placed in a swing furnace to combine materials; The crucible 2 is placed on the matching support rod 3 in the crystal growth furnace to ensure that the quartz crucible 2 is in a vertically stable state; Te is in the liquid phase; when the growth starts, the furnace body 1 rises at a certain speed, the quartz crucible passes through the temperature gradient zone 5, and the solubility of the lower part of the solution decreases with the decrease of the temperature. When the temperature drops to a certain value, CdZnTe Saturated precipitation from the solution, growing cadmium zinc telluride crystal 8, the above solution is a CZT saturated solution 7 with Te as the solvent.

The concrete process step of the example of the present invention is as follows:

(1) First, put the 7N high-purity raw material of Cd _0.9 Zn _0.1 Te that meets the stoichiometric ratio into the high-purity quartz crucible, then add 50% of the excess Te of the total mass of the raw material, and then evacuate to 2.0×10 ^-4 After Pa is melted and sealed, it is synthesized in a swing furnace to obtain a mixture of CdZnTe polycrystal and solvent Te;

(2) Place the quartz crucible 2 filled with synthetic raw materials on the matching support rod 3 to ensure that the quartz crucible 2 is vertical and stable;

(3) Adjust the position of the furnace body 1 so that the quartz crucible 2 is kept in the high temperature zone 4 for 24 hours, so that all the materials inside are in the liquid phase, and the rising speed of the furnace body 1 is set to 0.4mm/h when the growth starts. After all the quartz crucibles pass through the temperature gradient zone, the growth ends. The crystal is taken out, and the remaining Te used as a solvent at the tail is removed, and the front part is a free-selected CdZnTe crystal grown by the tellurium solvent solution method.

Embodiment two

In this embodiment, the same growth device as in the first embodiment above is used.

The growth process steps in this embodiment are completely the same as those in the first embodiment above, except that some process parameters are changed. The different process parameters are: (1) The Te-enriched amount in the raw material mixture is 70% of the total mass of raw materials; finally, cadmium zinc telluride crystals are obtained.

Embodiment three

In this embodiment, the same growth device as in the first embodiment above is used.

The growth process steps in this embodiment are completely the same as those in the first embodiment above, except that some process parameters are changed. The different process parameters are: the rising speed of the furnace body 1 is set to 0.8mm/h. CdZnTe crystals are finally obtained.

Embodiment Four

In this embodiment, the same growth device as in the first embodiment above is used.

The growth process steps in this embodiment are completely the same as those in the first embodiment above, except that some process parameters are changed. The different process parameters are: weigh according to the stoichiometric ratio of Cd _0.8 Zn _0.2 Te, and then add an excess Te of 50% of the total mass of raw materials. CdZnTe crystals are finally obtained.

Embodiment five

In this embodiment, the same growth device as in the first embodiment above is used.

The growth process steps in this embodiment are completely the same as those in the first embodiment above, except that some process parameters are changed. The different process parameters are: add 100ppm of doping (In, or Cl ^-1 , or Al) to the weighed material, and finally obtain cadmium zinc telluride crystal.

The device and method for growing cadmium zinc telluride crystals by using the tellurium solvent solution method of the present invention are simple to operate, reduce the crystal growth temperature, and reduce the pollution of impurities, and at the same time, the existence of the growth process plays a role in purifying the crystals, and finally obtains high-quality crystals. The pure cadmium zinc telluride crystal is used to improve the resistivity of the crystal by doping, which fully meets the requirements of the detector material.

Claims (1)

1. tellurium solvent solution method growing tellurium zinc cadmium crystalline method is characterized in that having following technological process and step:

A. according to stoichiometric, will satisfy chemical formula Cd _1-xZn _xThe purity of x=0.04 among the Te ~ 0.5 is that high-purity Cd, Zn, the Te raw material of 7N packed in the most advanced and sophisticated angled high-purity silica pot; 30%～80% excessive Te of extra again adding raw materials quality summation; Carry out donor doping simultaneously,, be evacuated to 2.0 * 10 then to improve crystalline resistivity ^-4Sealing by fusing quartz crucible behind the Pa obtains the mixture of tellurium zinc cadmium polycrystalline and solvent Te;

B. the above-mentioned quartz crucible that the polycrystal mixture of tellurium zinc cadmium is housed is put into and waved stove and carry out building-up reactions; Slowly be warming up to 500 ℃ of insulation 3h; And then slowly be warming up to 1000 ℃ the insulation 24h; Wave stove in the process of insulation and slowly shake the raw material that makes in the quartz crucible and fully react, be cooled to room temperature, end of synthesis subsequently slowly;

C. the quartz crucible of above-mentioned end of synthesis is put into crystal growing furnace; The high-temperature zone temperature of crystal growing furnace is set to 850～950 ℃; The cold zone temperature is set to 500～600 ℃; The temperature gradient zone temperature is set to 800～900 ℃, and the thermograde that makes its temperature gradient zone is at 15-25 ℃/cm; Before crystal growing process begins, quartz crucible is in high-temperature zone insulation 24h, makes its inner tellurium zinc cadmium polycrystalline and solvent Te all be in liquid phase; The adjustment body of heater subsequently with the speed rising body of heater of 0.04～2mm/h, guarantees that simultaneously support bar keeps transfixion; Be equivalent to quartz crucible and descend, during through temperature gradient zone, along with the reduction of temperature with identical speed; The saturation ratio of tellurium zinc cadmium descends in the Te solvent; When temperature drops to one regularly, the saturated tellurium zinc cadmium of separating out of the saturated solution of low-temperature end, promptly crucible bottom grows tellurium-zincium-cadmium crystal; When the whole temperature gradient zone of quartz crucible process, growth ending, saturated the separating out of most of tellurium zinc cadmium in the solution forms tellurium zinc cadmium crystal ingot, and afterbody then is tellurium zinc cadmium-Te mixture;

D. the crystal ingot with growth ending takes out from quartz crucible, removes the tellurium zinc cadmium-Te mixture of afterbody, and fore-end is the tellurium-zincium-cadmium crystal that freely selects crystalline substance that tellurium solvent solution method grows.