阅读说明：本技术 一种提高ZnTe晶体掺杂元素均匀性的方法 (Method for improving uniformity of doping elements of ZnTe crystal ) 是由 徐亚东 孙俊杰 于 2020-08-14 设计创作，主要内容包括：本发明公开了一种提高ZnTe晶体掺杂元素均匀性的方法,包括如下步骤：采用Te熔剂-TGSM技术生长ZnTe电光晶体；将晶体在生长炉内低温区保温退火；将晶体锭条取出,进行定向切片,研磨和抛光,然后清洗干净并甩干备用；建立掺杂量与ZnTe晶体电阻率及载流子传输特性的定量关系,获得THz辐射的吸收和散射机理；将晶体切片架在石英支架上固定于石英安瓿内,将安瓿瓶进行内进行抽真空,然后对安瓿瓶的瓶口进行熔封,将安瓿瓶放入退火炉进行均匀性退火。通过建立掺杂量与ZnTe晶体电阻率及载流子传输特性的定量关系,获得THz辐射的吸收和散射机理,优化掺杂浓度及设计多阶段组合退火处理工艺,最终获得高均匀性光学品质的ZnTe晶体。(The invention discloses a method for improving the uniformity of doping elements of ZnTe crystal, which comprises the following steps: growing ZnTe electro-optic crystal by using Te flux-TGSM technology; carrying out heat preservation annealing on the crystal in a low-temperature region in a growth furnace; taking out the crystal ingot, carrying out directional slicing, grinding and polishing, then cleaning and spin-drying for later use; establishing a quantitative relation between the doping amount and the resistivity of the ZnTe crystal and the transmission characteristic of a current carrier to obtain an absorption and scattering mechanism of THz radiation; fixing the crystal slice frame in a quartz ampoule on a quartz bracket, internally vacuumizing the ampoule, then sealing the opening of the ampoule by fusing, and putting the ampoule into an annealing furnace for uniform annealing. By establishing a quantitative relation between the doping amount and the resistivity of the ZnTe crystal and the carrier transmission characteristic, the absorption and scattering mechanism of THz radiation is obtained, the doping concentration is optimized, a multi-stage combined annealing treatment process is designed, and finally the ZnTe crystal with high uniformity optical quality is obtained.)

1. A method for improving the uniformity of doping elements of ZnTe crystal is characterized by comprising the following steps:

s1, crystal growth

Growing ZnTe electro-optic crystal by using Te flux-TGSM technology, and obtaining large-size ZnTe single crystal by optimizing ACRT parameter;

s2, annealing in crystal furnace

After all the crystals pass through the temperature gradient region of the vertical growth furnace, carrying out heat preservation annealing in the low-temperature region in the growth furnace;

s3 crystal surface treatment

Taking out the crystal ingot strip annealed in the furnace, directionally slicing the crystal orientation, grinding and polishing, cleaning and spin-drying for later use;

s4, doping element and crystal relation

Establishing a quantitative relation between the doping amount and the ZnTe crystal resistivity and the carrier transmission characteristic, obtaining an absorption and scattering mechanism of THz radiation, and summarizing the influence rule of the Te-rich phase and the induced defects thereof on the THz radiation efficiency, the uniformity and the like;

s5, crystal homogenizing annealing

Fixing the crystal slice frame in a quartz ampoule on a quartz bracket, internally vacuumizing the ampoule, then sealing the opening of the ampoule by fusing, and putting the ampoule into an annealing furnace for uniform annealing.

2. The method for improving the uniformity of doping elements of ZnTe crystal according to claim 1, wherein: in step S1, the crystal growth method comprises the steps of melting Te and Zn simple substances in a vacuum quartz crucible to form ZnTe ingot strips, and then putting the ingot strips together with the crucible into a vertical growth furnace for vertical growth.

3. The method for improving the uniformity of doping elements of ZnTe crystal according to claim 2, wherein: and swinging the Te and Zn simple substances when the Te and Zn simple substances are melted in the crucible, wherein the melting synthesis temperature is 20 ℃ higher than the melting point temperature of the ZnTe compound, naturally cooling and solidifying after 7h of melting synthesis, then putting the ZnTe ingot into a vertical growth furnace along with the crucible, wherein the highest temperature in the furnace is 1100 ℃, the low-temperature crystallization temperature is 1060 ℃, the temperature gradient is 10 ℃/cm, the descending speed of the crucible is 0.5-1mm/h, and moving the crucible to a low-temperature region to finish crystal growth after all the melt passes through the temperature gradient region of the vertical growth furnace.

4. The method for improving the uniformity of doping elements of ZnTe crystal according to claim 1, wherein: in step S2, when annealing is carried out in the crystal furnace, the whole furnace temperature of the growth furnace is adjusted to 450-510 ℃, and the annealing time is as follows: 24-48 h.

5. The method for improving the uniformity of doping elements of ZnTe crystal according to claim 1, wherein: in step S3, after the crystal slices are polished, the crystal is cleaned with an organic solvent and ultrasonic waves, and rinsed with deionized water and spun for use.

6. The method of claim 5, wherein the uniformity of doping elements of the ZnTe crystal is improved by: the organic solvent is one or more of isopropanol, petroleum ether and acetone.

7. The method for improving the uniformity of doping elements of ZnTe crystal according to claim 1, wherein: in step S4, the relationship between the doping amount and the ZnTe crystal performance is obtained by developing the macroscopic photoelectric performance of the ZnTe crystal and developing the THz-TDS system based on the ZnTe crystal, establishing a quantitative relationship between the doping amount and the performances such as the resistivity and the carrier mobility of the ZnTe crystal, and revealing the main factors affecting the generation and detection of THz radiation of the ZnTe crystal and revealing the rule of the influence of surface treatment and modification on THz response by combining the electrical characteristics such as the carrier concentration, lifetime and mobility and the absorption, transmission and scattering relationships of the ZnTe crystal in the THz band.

8. The method for improving the uniformity of doping elements of ZnTe crystal according to claim 1, wherein: in step S5, the quartz support and the quartz ampoule bottle are soaked by aqua regia and washed clean by deionized water and dried, and the vacuum degree in the quartz ampoule bottle is more than or equal to 5 multiplied by 10^-4Pa, the annealing temperature is 550-600 ℃, and the annealing time is 50-110 h.

Technical Field

The invention relates to the technical field of ZnTe crystals, in particular to a method for improving the uniformity of doping elements of the ZnTe crystals.

Background

Crystals are solids with internal particles arranged in periodic repetitions in three-dimensional space. Due to the special structural characteristics of the crystal, the crystal can realize the interaction and interconversion of electricity, heat, magnetism, light, sound and force, becomes an indispensable important functional material in industry, and is widely applied to the fields of communication, photography, astronavigation, medicine, geology, meteorology, architecture, military technology and the like. The crystal material can be classified into optical functional crystal, semiconductor crystal, piezoelectric crystal, pyroelectric crystal, super hard crystal, etc. according to different functional physical properties. The reserves of natural crystals are limited, and the purity and single crystallinity are difficult to guarantee due to inevitable various defects in natural formation. The artificial crystal can achieve the purpose of meeting specific requirements by controlling the growth rule and habit of the artificial crystal. One of them is to dope the crystal with elements having a certain kind (such as B and P, transition metal elements, rare earth elements, actinides, etc.) and content, so as to improve the crystal production quality and improve some properties.

Due to segregation of the doping elements, the contents of the doping elements in different parts of the growing ZnTe crystal are different, and further the difference exists in the electrical properties of the growing ZnTe crystal. The melting zone length is reduced, and the diffusion of solute can be promoted by adopting the ACRT technology, so that the segregation phenomenon can be reduced, and the uniformity of doped elements can be improved. In addition, the compensation mechanism between different doping elements and Zn space, the trapping property of free carriers and the solid solubility of the free carriers in ZnTe crystal are different, and a new defect complex can be introduced, so that the THz radiation efficiency is reduced and the waveform is changed. The state and energy level of the doping element need to be confirmed according to a defect physical and defect chemical analysis method and a quantitative characterization means of point defects, so that the doping concentration can be accurately controlled.

In recent years, researchers have developed tellurium self-flux (hereinafter referred to as Te flux) technology to grow ZnTe crystals, which can effectively lower the growth temperature of the crystals and can reduce impurities diffused from a quartz crucible under high temperature conditions. In 2014, a ZnTe crystal is grown by adopting a VGF method improved by a Te flux technology by a Japan new-day mining company. However, the Te flux method is adopted for ZnTe crystal growth, and has the remarkable characteristics that: along with the growth of the crystal, the continuous change of the components of the melt leads to the continuous change of the precipitation temperature and the precipitation rate of the solute, and further causes the unstable advancing rate and the unstable form of a liquid/solid interface.

Zn vacancy in the crystal is a main factor for determining the carrier concentration and resistivity of ZnTe crystal. The discovery of Wangxiemin of capital university and the like can be efficiently generatedThe resistivity of the ZnTe crystal detecting THz radiation is usually 10²-10⁶Omega cm. The resistivity of the ZnTe crystal can be adjusted in a wide range by growth doping. Such as: using ZnP₂As a dopant, the resistivity of the crystal can be reduced to 2.3 x 10^-2Omega cm, while the resistivity of the In-doped ZnTe crystal can reach 4.4 x 10⁸Omega cm. Asahi et al doped with GaS to achieve a resistivity of 10⁶Omega cm. In addition, researchers at the university of Princeton, USA, 2007 found that V-doping could significantly improve the electro-optic effect of the crystal. However, theoretical researches on the states of doping elements in crystals and the action rule of the doping elements and Zn vacancies are still lacked. Meanwhile, because the ii-vi semiconductor compound materials generally have a serious self-compensation phenomenon, how to achieve effective doping and control the uniformity of doping is also a technical problem to be solved at present, so we propose a method for improving the uniformity of doping elements of ZnTe crystals to solve the above problems.

Disclosure of Invention

The invention aims to provide a method for improving the uniformity of doping elements of ZnTe crystal, which aims to solve the problems in the background technology.

In order to achieve the purpose, the invention provides the following technical scheme: a method for improving the uniformity of doping elements of ZnTe crystal comprises the following steps:

s1, crystal growth

Growing ZnTe electro-optic crystal by using Te flux-TGSM technology, and obtaining large-size ZnTe single crystal by optimizing ACRT parameter;

s2, annealing in crystal furnace

After all the crystals pass through the temperature gradient region of the vertical growth furnace, carrying out heat preservation annealing in the low-temperature region in the growth furnace;

s3 crystal surface treatment

Taking out the crystal ingot strip annealed in the furnace, directionally slicing the crystal orientation, grinding and polishing, cleaning and spin-drying for later use;

s4, detecting relation between doping elements and crystals

Establishing a quantitative relation between the doping amount and the ZnTe crystal resistivity and the carrier transmission characteristic, obtaining an absorption and scattering mechanism of THz radiation, and summarizing the influence rule of the Te-rich phase and the induced defects thereof on the THz radiation efficiency, the uniformity and the like;

s5, crystal homogenizing annealing

Fixing the crystal slice frame in a quartz ampoule on a quartz bracket, internally vacuumizing the ampoule, then sealing the opening of the ampoule by fusing, and putting the ampoule into an annealing furnace for uniform annealing.

In a preferred embodiment, in step S1, the crystal growth method comprises melting Te and Zn in a vacuum quartz crucible to form ZnTe ingot, and then placing the ingot together with the crucible into a vertical growth furnace for vertical growth.

In a preferred embodiment, the Te and Zn simple substances are shaken when melted in a crucible, the melting synthesis temperature is 20 ℃ higher than the melting point temperature of the ZnTe compound, after 7 hours of melting synthesis, the ZnTe ingot is naturally cooled and solidified, then the ZnTe ingot is put into a vertical growth furnace along with the crucible, the highest temperature in the furnace is 1100 ℃, the low-temperature crystallization temperature is 1060 ℃, the temperature gradient is 10 ℃/cm, the descending speed of the crucible is 0.5-1mm/h, and after the melt completely passes through the temperature gradient area of the vertical growth furnace, the crystal growth is finished in a low-temperature area.

In a preferred embodiment, in step S2, when annealing is performed in the crystal furnace, the overall furnace temperature of the growth furnace is adjusted to 450 ℃ to 510 ℃, and the annealing time is: 24-48 h.

In a preferred embodiment, in step S3, after the crystal slices are polished, the crystal is cleaned by using an organic solvent and ultrasonic waves, and is rinsed with deionized water and spun for use.

In a preferred embodiment, the organic solvent is one or more of isopropanol, petroleum ether and acetone.

In a preferred embodiment, in step S4, the relationship between the doping amount and the ZnTe crystal performance is obtained by developing the macro-photoelectric performance of the ZnTe crystal and developing a THz-TDS system based on the ZnTe crystal, establishing a quantitative relationship between the doping amount and the performances such as the resistivity and the carrier mobility of the ZnTe crystal, and combining the electrical characteristics such as the carrier concentration, the lifetime, and the mobility with the absorption, transmission, and scattering relationships of the ZnTe crystal in the THz band, revealing main factors influencing the generation and detection of the ZnTe crystal and revealing the influence rule of the surface treatment and modification on the THz response.

In a preferred embodiment, in step S5, the quartz holder and the quartz ampoule are soaked in aqua regia and rinsed with deionized water and dried, and the vacuum degree in the quartz ampoule is greater than or equal to 5 × 10^-4Pa, the annealing temperature is 550-600 ℃, and the annealing time is 50-110 h.

Compared with the prior art, the invention has the beneficial effects that:

1. carrying out surface treatment on the ZnTe crystal by batch processing technologies such as directional cutting, grinding and polishing on the ZnTe crystal, and establishing a quantitative relation between doping amount and ZnTe crystal resistivity and carrier transmission characteristics to obtain an absorption and scattering mechanism of THz radiation, thereby essentially disclosing key factors of doping elements influencing the THz response performance of the ZnTe crystal;

2. by optimizing the doping concentration and designing a multi-stage combined annealing treatment process, the ZnTe crystal with high optical quality is finally obtained, an engineering technology of the ZnTe-based electro-optic crystal for terahertz generation and detection is formed, and a foundation is laid for developing high-performance THz spectrometers and THz imaging devices and realizing the application of the THTe-based electro-optic crystal in the fields of medical imaging, safety inspection, atmospheric environment quality monitoring, industrial nondestructive detection and the like.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The invention provides a technical scheme that: a method for improving the uniformity of doping elements of ZnTe crystal comprises the following steps:

s1, crystal growth

Growing ZnTe electro-optic crystal by using Te flux-TGSM technology, and obtaining large-size ZnTe single crystal by optimizing ACRT parameter;

s2, annealing in crystal furnace

After all the crystals pass through the temperature gradient region of the vertical growth furnace, carrying out heat preservation annealing in the low-temperature region in the growth furnace;

s3 crystal surface treatment

Taking out the crystal ingot strip annealed in the furnace, directionally slicing the crystal orientation, grinding and polishing, cleaning and spin-drying for later use;

s4, detecting relation between doping elements and crystals

Establishing a quantitative relation between the doping amount and the ZnTe crystal resistivity and the carrier transmission characteristic, obtaining an absorption and scattering mechanism of THz radiation, and summarizing the influence rule of the Te-rich phase and the induced defects thereof on the THz radiation efficiency, the uniformity and the like;

s5, crystal homogenizing annealing

Fixing the crystal slice frame in a quartz ampoule on a quartz bracket, internally vacuumizing the ampoule, then sealing the opening of the ampoule by fusing, and putting the ampoule into an annealing furnace for uniform annealing.

In step S1, the crystal growth method comprises the steps of melting Te and Zn simple substances in a vacuum quartz crucible to form ZnTe ingot strips, and then putting the ingot strips together with the crucible into a vertical growth furnace for vertical growth.

Further, Te and Zn simple substances are swung when melted in a crucible, the melting synthesis temperature is 20 ℃ higher than the melting point temperature of the ZnTe compound, the temperature is naturally reduced and solidified after 7 hours of melting synthesis, then the ZnTe ingot is put into a vertical growth furnace along with the crucible, the highest temperature in the furnace is 1100 ℃, the low-temperature crystallization temperature is 1060 ℃, the temperature gradient is 10 ℃/cm, the descending speed of the crucible is 0.5-1mm/h, and the crystal growth is finished when all the melt passes through the temperature gradient area of the vertical growth furnace.

In step S2, when annealing is carried out in the crystal furnace, the whole furnace temperature of the growth furnace is adjusted to 450-510 ℃, and the annealing time is as follows: 24-48 h.

In step S3, the crystal slices are polished, then cleaned with acetone and ultrasonic waves, rinsed with deionized water, and spun for use.

In step S4, the relation between the doping amount and the ZnTe crystal performance is realized by developing the macroscopic photoelectric property of the ZnTe crystal, developing a THz-TDS system based on ZnTe crystal, establishing a quantitative relation between doping amount and the properties of ZnTe crystal such as resistivity, carrier mobility and the like, and combines the electric characteristics such as carrier concentration, service life and mobility with the absorption, transmission and scattering relations of the ZnTe crystal in the THz wave band, reveals the main factors influencing the generation and detection of the THz radiation of the ZnTe crystal, reveals the influence rule of surface treatment and modification on the THz response, and further, the structural defects in the growing crystal are characterized, the compensation principle and efficiency of doping on Zn vacancy are mainly explored, the interaction mechanism and evolution rule of the Te-rich phase and the induced defects thereof are disclosed, the research result is taken as the basis, providing basis for optimizing the doping concentration and multi-stage combined annealing treatment, and finally obtaining the ZnTe crystal with high optical quality.

In step S5, the quartz support and the quartz ampoule bottle are soaked by aqua regia and washed clean by deionized water and dried, the vacuum degree in the quartz ampoule bottle is more than 5 x 10 < -4 > Pa, the annealing temperature is 550-.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.