Preparation method of Cd0. 9Mn0. 1Te semiconductor crystal

Abstract

The invention relates to the technical field of special crystal growth, in particular to a preparation method of a Cd0. 9Mn0. 1Te semiconductor crystal, which realizes controllable preparation of a high-quality Cd.Mn.Te single crystal through raw material ratio optimization, environment control, multi-stage reaction and precise temperature control technologies, and has the specific innovation point of temperature gradient control. Under the condition of excessive Te, the temperature and the heating rate can be accurately controlled through the three-temperature-zone crystal growth furnace, a proper and stable vertical temperature gradient is formed, and the existence of the temperature gradient is beneficial to inhibiting instability in the crystal growth process, optimizing the crystal quality and reducing crystal defects.

Description

Technical Field

[0001] The present invention relates to the technical field of special crystal growth, and is particularly concerned with a Cd 0.9 Mn 0.1 Method for preparing Te semiconductor crystal. Background Art

[0002] As a basic product of the modern electronics industry, semiconductor materials are of vital importance in the field of artificial intelligence. According to the chemical composition of semiconductor materials, they can be divided into elemental semiconductors and compound semiconductors. Elemental semiconductors are composed of a single element, such as silicon (Si) and germanium (Ge), which are widely used in traditional integrated circuits and solar cells. Compound semiconductors are composed of two or more elements, such as gallium arsenide (GaAs), gallium nitride (GaN), silicon carbide (SiC), etc., which have significant application advantages in RF, power devices, optoelectronics, and national defense and military industries due to their large bandgap, high power density, and excellent electron mobility.

[0003] Cadmium manganese telluride (Cd 1-x Mn x Te, referred to as CdMnTe or CMT) crystal is a II-VI compound semiconductor, which has the advantages of high atomic number, wide band gap, large resistivity, and excellent carrier mobility-lifetime product. 1-x Mn x The segregation coefficient of Mn in Te crystal is close to 1, which helps to achieve a more uniform composition distribution. 1-x Mn x Te has significant advantages in the application of X / γ-ray room temperature detectors. At the same time, with the continuous expansion of the demand for HgCdTe infrared detectors in the defense field, Cd 1-x Mn x Te crystals are becoming increasingly important as high-quality substrate materials.

[0004] Compared with first-generation silicon (Si) semiconductors and third-generation gallium arsenide (GaAs) semiconductor crystals, CdMnTe has poor thermophysical properties near the melting point, including higher component partial pressure, lower thermal conductivity, stronger ionic bonding characteristics, lower stacking fault energy and critical shear stress. These factors make the growth of large-sized and high-quality single-crystal CdMnTe crystals face many challenges: (1) Stoichiometric deviation: During the growth of CdMnTe crystals, since Cd is more volatile than Te, the concentration of Cd in the crystal is lower than expected, while Te is relatively stable. This volatility difference causes the relative ratio of Cd to Te to change, resulting in a deviation from the stoichiometric ratio, making it difficult to accurately control the chemical ratio of the material. (2) Mn purity: Low Mn purity in the raw material will lead to an increase in impurity content, which may not only cause changes in the chemical stability of the material, but may also have an adverse effect on the conductivity, optical properties and other important physical properties. (3) The growth interface morphology is difficult to control: The thermal conductivity of CdMnTe crystals is low, resulting in uneven temperature and concentration gradients at the solid-liquid interface, forming a concave interface. The concave increases the probability of sidewall nucleation, promotes polycrystalline growth, reduces the efficiency of single crystal growth, and provides favorable conditions for the formation of twins and dislocations and the removal of impurities, thereby affecting the purity and performance of the crystal. (4) Crystal structure defects are easy to produce: The critical shear stress of CdMnTe crystals is small, dislocations are easy to form, and low stacking faults can make the crystals susceptible to disturbance, resulting in twins and stacking faults. These defects will affect the structural stability of the crystal and its optical, electrical and thermal conductivity properties.

[0005] At present, there are many methods for preparing CdMnTe crystals, such as the Bridgman method (under the premise of excess Te, the growth of crystals is controlled by temperature gradient, which can achieve high-quality crystal growth, especially suitable for materials with high melting points or complex compositions), vertical gradient solidification method and mobile heating method, etc. However, these methods often face challenges such as complex processes, uneven crystal composition and difficult quality control. Summary of the invention

[0006] In view of the problems in the prior art that the preparation process of CdMnTe crystal is complicated, the crystal composition is uneven, and the quality control of the finished product is difficult, the present invention provides a Cd 0.9 Mn 0.1 Method for preparing Te semiconductor crystal.

[0007] The present invention is achieved through the following technical solutions: A Cd 0.9 Mn 0.1 The method for preparing Te semiconductor crystal comprises the following steps: S1, cleaning the crucible and evaporating a carbon film on the inner wall of the crucible; S2, solid raw materials Cd, Mn and Te are prepared in a molar ratio of 0.9:0.1:1.1 with Te in excess of 10%, and are loaded into the crucible with the carbon film in S1, and then the crucible is sealed and evacuated to a vacuum state for standby use; S3, combining the raw materials in the crucible to obtain a crude polycrystalline material; S4, the rough polycrystalline material grows under the vertical temperature gradient of three temperature zones to generate Cd 0.9 Mn 0.1 Te single crystal.

[0008] Preferably, in S1, during cleaning, different cleaning agents are used for multiple cleanings, and the cleaning agents used are deionized water, acetone solution, aqua regia solution, HF solution and deionized water, respectively.

[0009] Preferably, in S1, the specific process of evaporating the carbon film is: heating the acetone solution, cracking the acetone under an argon gas flow, and depositing the cracked carbon particles on the inner wall of the crucible to form a carbon film.

[0010] Preferably, the thickness of the carbon film is 20-50 μm.

[0011] Preferably, in S2, the purity of Cd is 7N or more, the purity of Mn is 5N or more, and the purity of Te is 7N or more.

[0012] Preferably, in S2, the vacuum degree in the crucible after the tube is sealed and evacuated is 5×10 5 Pa.

[0013] Preferably, in S3, the mixing process includes heating, heat preservation and cooling, specifically: S31, raise the temperature from room temperature to 321°C at a rate of 20-30°C / h, and keep at 321°C for 1-2h; S32, reducing the heating rate to 10-20°C / h, continuing to heat to 450°C, and maintaining at 450°C for 5h; S33, increasing the heating rate to 30-40°C / h to 1090°C, and setting a longer holding time at this temperature as required, which is greater than the holding time required to meet the S34 and S35 operations; S34, then keep warm for 2 hours, and rock the crucible at a rocking speed of 1-2 r / min for 24 hours; S35, stop shaking, keep warm for 2 hours, and then cool naturally at room temperature to obtain a crude polycrystalline material.

[0014] Preferably, in S4, Cd is generated 0.9 Mn 0.1 The specific process of Te single crystal is: S41, set the temperature of three temperature zones from top to bottom, respectively recorded as the first temperature zone, the second temperature zone and the third temperature zone, and the temperature gradually decreases from top to bottom; the temperature satisfies the condition: when the crucible is in the middle of the inner space of the heating furnace, the tip of the crucible is at Cd 0.9 Mn 0.1 The growth point of Te is at 1030℃, and the temperature gradient 3~5cm below the growth point meets 10~15℃ / cm; S42, when the temperature meets the conditions, keep warm for 2 hours; S43, moving the crucible to a hot spot, and overheating for 24 hours to melt the coarse polycrystalline material; wherein the hot spot is a position 30° C. higher than the temperature at the growth point; S44, after overheating, move the crucible to the growth point and keep it warm for 2h; S45, under heat preservation conditions, the crucible is lowered by 10-15 cm at a speed of 0.2-0.25 mm / h, and the crystal begins to grow; S46, after the growth is completed, stop moving the crucible and keep warm for 2 hours; S47, after the insulation is completed, the temperature of the three temperature zones is set to 860°C, and the temperature is reduced to 860°C standard temperature within 10 hours, and the temperature is kept for 48 hours, and the crucible is annealed in situ; S48, after the annealing is completed, the temperature of the three temperature zones is lowered to 500°C at a cooling rate of 5°C / h, the furnace body is powered off, and the crucible is cooled naturally; after the furnace is cooled to room temperature, the crystal stops growing and is taken out to obtain Cd 0.9 Mn 0.1 Te single crystal.

[0015] A Cd 0.9 Mn 0.1 The product obtained by the method for preparing Te semiconductor crystal.

[0016] A semiconductor device comprising the product.

[0017] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a method for preparing Cd0.9Mn0.1Te semiconductor crystals, which realizes high-quality Cd0.9Mn0.1Te semiconductor crystals by optimizing raw material ratio, environmental control, multi-stage reaction and precise temperature control technology. 0 . 9 Mn 0 . 1 Controllable preparation of Te single crystal. Specifically, the innovation lies in the control of temperature gradient, that is, the temperature and heating rate can be accurately controlled through the three-temperature zone crystal growth furnace under Te excess to form a suitable and stable vertical temperature gradient. The existence of temperature gradient helps to suppress the instability in the crystal growth process, optimize the quality of the crystal and reduce crystal defects.

[0018] Furthermore, multiple cleaning agents are used for multiple cleanings to ensure the cleanliness of the crucible and reduce the introduction of impurities. At the same time, the evaporated carbon film can protect the inner wall of the crucible to prevent the raw materials from directly reacting with the crucible. At the same time, the carbon film may help the uniform melting of the raw materials and the crystal growth.

[0019] Furthermore, the design of a 10% excess Te ratio can compensate for Te that may volatilize during high-temperature treatment, avoid component deviation caused by volatilization, and ensure the accuracy of the composition of the final crystal.

[0020] Furthermore, in the material mixing process, the gradual increase in temperature combined with the rocking of the crucible promotes uniform mixing of the melt, reduces component segregation, and forms high-quality polycrystalline materials.

[0021] Furthermore, the growth point temperature and temperature gradient are optimized to ensure the stable growth and high quality of the crystal. Specifically, first, the vertical temperature gradient of the three temperature zones controls the growth environment of the crystal, and then the temperature gradient near the growth point (3~5cm downward) should be maintained at 10~15℃ / cm, and the crystal growth rate (crucible descent speed) should not be too fast; overheating treatment helps to eliminate the stress in the raw materials and improve the uniformity of the crystal; then the growth rate of the crystal is controlled by slowly lowering the speed of the crucible to ensure the integrity of the crystal, and finally in-situ annealing treatment helps to reduce defects in the crystal and improve the crystal quality of the crystal. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This invention is a Cd 0.9 Mn 0.1 Flow chart of the method for preparing Te semiconductor crystal; Figure 2 This invention is a Cd 0.9 Mn 0.1 The process curve of mixing materials in the preparation method of Te semiconductor crystal; Figure 3 This invention is a Cd 0.9 Mn 0.1 Schematic diagram of a heating furnace for growing a Te semiconductor crystal under a three-temperature zone vertical temperature gradient in a method for preparing the Te semiconductor crystal; Figure 4 This invention is a Cd 0.9 Mn 0.1 A process temperature control curve for growing a Te semiconductor crystal under a vertical temperature gradient in three temperature zones in a method for preparing the Te semiconductor crystal; Figure 5 The Cd obtained in Example 1 of the present invention 0.9 Mn 0.1 XRD diffraction peaks of the head, middle and tail crystals of the Te ingot; Figure 6The Cd obtained in Example 1 of the present invention 0.9 Mn 0.1 UV-Vis-NIR spectra of the head, middle and tail crystals of Te ingot; Figure 7 The Cd obtained in Example 1 of the present invention 0.9 Mn 0.1 The cutoff wavelength of the head crystal of the Te ingot; Figure 8 The Cd obtained in Example 1 of the present invention 0.9 Mn 0.1 The bandgap width of the head crystal of the Te ingot; Fig. 9 The Cd obtained in Example 1 of the present invention 0.9 Mn 0.1 The cutoff wavelength of the middle crystal of the Te ingot; Fig.10 The Cd obtained in Example 1 of the present invention 0.9 Mn 0.1 The bandgap width of the middle crystal of the Te ingot; Fig.11 The Cd obtained in Example 1 of the present invention 0.9 Mn 0.1 The cutoff wavelength of the tail crystal of the Te ingot; Fig.12 The Cd obtained in Example 1 of the present invention 0.9 Mn 0.1 The bandgap width of the tail crystal of the Te ingot; Fig.13 The Cd obtained in Example 1 of the present invention 0.9 Mn 0.1 Infrared transmission spectra of the head, middle and tail crystals of the Te ingot; Fig.14 The Cd obtained in Example 1 of the present invention 0.9 Mn 0.1 IV curves of the head, middle, and tail crystals of a Te ingot. DETAILED DESCRIPTION

[0023] The present invention is further described in detail below in conjunction with specific embodiments, which are intended to explain the present invention rather than to limit it.

[0024] The invention discloses a Cd 0.9 Mn 0.1 The preparation method of Te semiconductor crystal is as follows: Figure 1 , including the following steps: S1, cleaning the crucible and evaporating a carbon film on the inner wall of the crucible.

[0025] Among them, during cleaning, different cleaning agents are used for multiple cleanings, and the cleaning agents used are deionized water, acetone solution, aqua regia solution, HF solution and deionized water. The specific cleaning steps are: 1. Rinse with deionized water 2 to 4 times; 2. Soak in acetone solution (concentration 100%) for 24 hours to remove organic matter; 3. Soak in aqua regia solution (HCl: HNO3=3:1) for 24 hours to remove inorganic matter; 4. Soak in 10% HF solution for 20 minutes; 5. Rinse repeatedly with deionized water, dry and seal to prevent other impurities from entering.

[0026] The specific process of carbon film evaporation is as follows: place the crucible at a certain angle (30°~45°) in a resistance furnace and insert the gas guide tube into the bottom of the crucible. Then heat the acetone solution and crack the acetone under the flow of argon gas with a purity of 99.9% or higher. The cracked carbon particles are deposited on the inner wall of the crucible to form a carbon film with a thickness of 20~50μm.

[0027] S2, solid raw materials Cd (purity of 7N or above), Mn (purity of 5N or above) and Te (purity of 7N or above) are prepared in a molar ratio of 0.9:0.1:1.1 with an excess of 10% Te, and then loaded into the crucible with carbon film in S1, and the crucible plug is plugged to seal the tube. When sealing the tube, a hydrogen-oxygen flame is used to fully burn the crucible plug part so that it is completely melted with the crucible and then the crucible mouth is sealed. Then a vacuum compressor is used to evacuate the inside of the crucible to 5×10 5 The crucible is in a high vacuum state of 100 Pa to remove gas molecules. At this time, the inside of the crucible is completely in a vacuum state to ensure that no foreign impurities are introduced during the mixing and crystal growth.

[0028] S3, combining the raw materials in the crucible to obtain a rough polycrystalline material.

[0029] Specifically, the mixing process is carried out using a swing mixing furnace, which is mainly divided into three parts: heating, insulation and cooling. The temperature control curve is as follows: Figure 2 As shown: S31, raise the temperature from room temperature to 321°C at a rate of 20-30°C / h, and keep at 321°C for 1-2h; S32, reducing the heating rate to 10-20°C / h, continuing to heat to 450°C, and maintaining at 450°C for 5h; S33, increase the heating rate to 30~40℃ / h, rise to 1090℃, and set a longer insulation time at this temperature as needed. The insulation time at this time is greater than the insulation time that meets S34 and S35 operations; if the subsequent operation requires insulation for 28h, then the insulation time here needs to be set to be higher than 28h.

[0030] S34, then keep warm for 2 hours, and rock the crucible at a rocking speed of 1-2 r / min for 24 hours; rocking the crucible helps to further homogenize the raw materials, and limiting the rocking speed is to reduce the impact force of the melt in the crucible on the inner wall of the crucible.

[0031] S35, stop shaking, keep warm for 2 hours, turn off the mixing program and control power, and let the mixing furnace cool naturally at room temperature to obtain rough polycrystalline material.

[0032] S4, the rough polycrystalline material grows under the vertical temperature gradient of three temperature zones to generate Cd 0.9 Mn 0.1 Te single crystal.

[0033] Specifically, a three-temperature zone crystal growth furnace single crystal growth process is used to grow Cd 0.9 Mn 0.1 Te single crystal, the structure of the growth furnace is as follows Figure 3 As shown. Generate Cd 0.9 Mn 0.1 Te single crystals were grown using Figure 4 The temperature control curve shown in the figure is as follows: S41, setting the temperatures of three temperature zones from top to bottom, which are respectively recorded as the first temperature zone, the second temperature zone and the third temperature zone, and the temperatures are gradually reduced from top to bottom; Temperature meets the condition: When the crucible is in the middle of the heating furnace, the tip of the crucible is at Cd 0.9 Mn 0.1 The growth point of Te is at 1030℃, and the temperature gradient 3~5cm below the growth point meets 10~15℃ / cm; S42, when the temperature meets the conditions, keep warm for 2 hours; S43, moving the crucible to a hot spot, and overheating for 24 hours to melt the coarse polycrystalline material; wherein the hot spot is a position 30° C. higher than the temperature at the growth point; S44, after overheating, move the crucible to the growth point and keep it warm for 2h; S45, under heat preservation conditions, the crucible is lowered by 10-15 cm at a speed of 0.2-0.25 mm / h, and the crystal begins to grow; S46, after the growth is completed, stop moving the crucible and keep warm for 2 hours; S47, after the insulation is completed, the temperature of the three temperature zones is set to 860°C, and the temperature is reduced to 860°C standard temperature within 10 hours, and the temperature is kept for 48 hours, and the crucible is annealed in situ; S48, after the annealing is completed, the temperature of the three temperature zones is lowered to 500°C at a cooling rate of 5°C / h, the furnace body is powered off, and the crucible is cooled naturally; after the furnace is cooled to room temperature, the crystal stops growing and is taken out to obtain Cd 0.9 Mn0.1 Te single crystal.

[0034] The present invention is a Cd 0.9 Mn 0.1 The method for preparing Te semiconductor crystals can accurately control the temperature and heating rate through a three-temperature zone crystal growth furnace to form a suitable and stable vertical temperature gradient, and use the temperature gradient to suppress the instability during the crystal growth process, optimize the quality of the crystal and reduce crystal defects, so as to obtain Cd Te with higher crystal quality and lower defect density. 0.9 Mn 0.1 Te single crystal.

[0035] The invention also discloses a method according to Cd 0.9 Mn 0.1 The product obtained by the method for preparing Te semiconductor crystal.

[0036] The invention also discloses a semiconductor device comprising the product.

[0037] Example 1 S1, clean the quartz crucible (when cleaning and soaking, ensure that the 2 / 3 part above the tip of the crucible is clean). The main steps are: 1. Rinse with deionized water twice; 2. Soak in acetone solution (concentration 100%) for 24 hours to remove organic matter; 3. Soak in aqua regia solution (HCl: HNO3=3:1) for 24 hours to remove inorganic matter; 4. Soak in 10% HF solution for 20 minutes; 5. Rinse repeatedly with deionized water, dry and seal to prevent other impurities from entering. After the crucible is cleaned, evaporate the carbon film: place the crucible in a resistance furnace at a certain angle of 45°, and insert the air guide tube into the bottom of the crucible. Then start heating acetone, which will undergo a cracking reaction at 948°C to generate carbon particles. An argon gas flow with a purity of 99.9% is introduced through the air guide tube to bring the carbon particles to the inner wall of the crucible for deposition, forming a 50-micron thick carbon layer.

[0038] S2, Cd (purity 7N), Mn (purity 5N), Te (purity 7N) raw materials are mixed according to the molar ratio of 0.9:0.1:1.1 with 10% excess Te, and then loaded into a quartz crucible, and then plugged with a crucible stopper. After loading, the crucible is evacuated to 5×10 5 Pa high vacuum state to remove gas molecules. When sealing the tube, hydrogen-oxygen flame is used to fully burn the crucible plug part, so that it is completely melted together with the crucible and then the crucible mouth is sealed. At this time, the inside of the crucible is completely in a vacuum state, ensuring that no foreign impurities are introduced during the mixing and crystal growth.

[0039] S3, Swinging Furnace Process: The synthesis of polycrystalline materials is mainly divided into three parts: heating, insulation and cooling. The temperature control curve is as follows: Figure 2As shown. First, the temperature is raised from room temperature to 321°C at a rate of 30°C / h, and kept at this temperature for 2h. Subsequently, the heating rate is reduced to 20°C / h, and the temperature is continued to rise to the melting point of Te, 450°C, and kept at 450°C for 5h. Finally, the heating rate is increased to 40°C / h, rising to 1090°C, and a longer holding time can be set at this temperature as needed. After 2h of holding, turn on the swing transmission device of the swing mixing furnace. In order to reduce the impact of the melt in the crucible on the inner wall of the crucible, set the swing speed to 1.8r / min, so that the melt rotates 360° with the crucible, and the components in the melt are mixed evenly. After 24h, turn off the swing device, and after keeping warm for another 2h, turn off the mixing program and control power supply, and let the mixing furnace cool naturally with room temperature.

[0040] S4, three-temperature zone crystal growth furnace single crystal growth process: three-temperature zone crystal growth furnace such as Figure 3 As shown, the temperature control curve is Figure 4 As shown (the set temperatures of the upper, middle and lower furnaces in the figure are 1120℃, 900℃ and 770℃ respectively), the growth process is as follows: 1. Fix the crucible holder on the mechanical transmission device of the crystal growth furnace, then place the crucible, and align the temperature sensing thermocouple at the top of the temperature measuring rod with the tip of the crucible to determine the actual growth point position. Finally, adjust the crucible to the middle of the furnace; 2. After the temperature is measured by the temperature measuring rod, the upper, middle and lower furnace temperatures are set to 1120℃, 900℃ and 770℃ respectively. When the growth point temperature is 1030℃ and the overheating point (the overheating temperature is 30℃ higher than the growth point temperature, which is 1060℃), the crucible can be placed in the growth furnace, and the temperature gradient 4cm below the growth point meets 10~15℃ / cm. The heating time is 21.5h. After reaching the target temperature, keep warm for 2h; 3. Move the crucible to the hot spot temperature position through the transmission device, and overheat for 24 hours to ensure that the polycrystalline material is fully melted and the heterogeneous nucleation is eliminated. After the overheating is over, slowly lower the crucible and measure the temperature through the temperature measuring rod. After the crucible stays at the growth point temperature, keep it warm for 2 hours; 4. Turn on the automatic control system of the transmission device, and make the crucible drop at a speed of 0.25mm / h. The drop distance is 11cm (this distance is the length of the crystal ingot in the crucible). At this time, the crystal growth begins. During this period, the three heating furnaces are in a heat preservation state for 440 hours. After the growth is completed, the transmission device stops running and keeps warm for 2 hours. 5. Set the temperature of the upper, middle and lower furnaces to 860°C, and the cooling time is 10 hours. After reaching the target temperature, keep the temperature for 48 hours to anneal the crucible in situ, which can effectively reduce thermal stress and avoid the generation of new stress and defects. At the same time, it promotes further diffusion and homogenization of components at high temperature, repairs some micro defects, and maintains the integrity and stability of the crystal structure. 6. After annealing, set the cooling rate to 5℃ / h, and let the temperature of the upper, middle and lower furnaces drop to 500℃. Then cut off the power and let the crucible cool naturally. When the temperature drops to room temperature, the crystal growth is over and the crucible is taken out for subsequent operations.

[0041] After taking out the crucible, use a cutter to cut the Cd 0.9 Mn 0.1 The Te ingot was taken out of the crucible. The overall length of the ingot was 93.5 mm, the diameter was 28 mm, and the surface was bright silver. This was due to the use of the Te solution Bridgman method to grow crystals, resulting in a Te-rich layer on the surface of the ingot. The phenomenon at the tail is shown in the figure. As the crystal growth continues, the solute concentration in the solution gradually decreases, causing the crystal growth rate to slow down and the crystallization temperature to continue to drop. When the temperature drops, the solubility in the solution is not enough to continue to dissolve Te, resulting in excessive precipitation of Te. In this process, the liquid-solid interface is unstable, causing Te to fail to fully combine with the CdMnTe crystal, but to precipitate in a single phase at the tail of the ingot. Due to the excessive accumulation of Te, a large number of Te single-phase regions are formed at the tail, making it an unusable area.

[0042] A diamond wire saw was used to cut radial wafers with a thickness of 2.3 mm at the head, middle and tail of the ingot. The front and middle wafers of the ingot are mostly composed of a large grain with a high single crystal rate, while the tail wafer is composed of a large grain and two small grains. The formation of a high single crystal rate is due to the relatively uniform temperature gradient in the front and middle regions, which promotes the formation of larger grains during the growth process of the crystal, and the single crystal growth is relatively good. The appearance of multiple grains in the rear wafer is related to the faster cooling rate of the temperature in the cooling stage after the end of crystal growth. This rapid cooling may cause more dense nucleation in this area, thus forming a large grain and two small grains.

[0043] Reference Figure 5 , the crystals in the three locations all contain 7 diffraction peaks. By analyzing these peaks and comparing them with the Cd0.9Mn0.1Te standard card (PDF#65-8867), it was found that the positions of the diffraction peaks were exactly the same as those of the standard card. This result shows that the grown Cd 0.9 Mn 0.1 Te crystals have F-43m space group and cubic sphalerite structure. In addition, no other impurity peaks were observed except for these 7 diffraction peaks, which further proves that the crystals are of high purity and have very low impurity content. This shows that the prepared crystals are of excellent quality and are almost not disturbed or contaminated by the outside world. Among the three samples, the diffraction peak corresponding to the (220) crystal plane has the strongest intensity and sharp peak shape, indicating that the crystals have been grown along the <110> The direction shows preferential growth characteristics, indicating that it has good orientation and crystallinity.

[0044] Reference Figure 6 When the wavelength of the incident light is less than 780nm, the transmittance is close to zero, because at this time the energy of the photon is greater than the bandgap width of the crystal, and the electrons will completely absorb the energy of the incident light and transition from the valence band to the conduction band. This area is called the strong absorption region. As the wavelength of the incident light varies between 780 and 830nm, the transmittance of the crystal increases exponentially. When the wavelength of the incident light is greater than 830nm, the transmittance gradually increases, ranging from 56.3% to 64.4%, which means that more than half of the photons can pass through the crystal, and the remaining part may be absorbed due to crystal defects. This area is called the weak absorption region. In this region, the energy of the incident light is lower than the bandgap width of the crystal, and the electrons cannot obtain enough energy to transition from the valence band to the conduction band, so no intrinsic absorption occurs.

[0045] According to the semiconductor light absorption law, the relationship between the absorption coefficient and the band gap width can be expressed by the following formula: (1) In the formula, α is the absorption coefficient; hν is the incident light energy; B is a constant; Eg is the bandgap width; γ is the mechanism index of electronic transition.

[0046] Since CdMnTe crystal is a direct band gap crystal, the value of γ in formula (1) is 1 / 2. and In direct proportional relationship, formula (1) can be expressed as formula (2): (2) right Figure 7 Differentiate the value in once, and the x value corresponding to the maximum value is the absorption edge cutoff wavelength of the crystal. By extrapolating formula (2), the bandgap width of the crystal at different positions of the Cd0.9Mn0.1Te ingot can be obtained. The cutoff wavelength and bandgap width of the crystal at different positions of the Cd0.9Mn0.1Te ingot are as follows: Figure 7 , 8 As shown in Figures 9, 10, 11, and 12, it can be seen that the absorption edge cutoff wavelength of the Cd0.9Mn0.1Te crystal is in the range of 801~808nm, and the bandgap width is between 1.53~1.54eV, which indicates that the bandgap width at different positions of the ingot varies little, indicating that the optical properties of the crystal in each area are relatively uniform. This may mean that during the growth process, the material quality of the Cd0.9Mn0.1Te ingot remains consistent and is not affected by significant defects or uneven doping. In addition, the small range of the bandgap width indicates that the doping concentration of Mn is relatively uniform throughout the ingot.

[0047] Reference Fig.13The infrared transmittance curves of the head, middle and tail crystals in the range of 500~4000cm-1 remain basically horizontal without obvious fluctuations. The infrared transmittance of the middle crystal is slightly lower than the theoretical maximum value of 65%, at 64.32%, the infrared transmittance of the head crystal is 61.73%, and the infrared transmittance of the tail crystal is as low as 54.6%. Overall, the quality of Cd0.9Mn0.1Te crystals is relatively high. The transmittance of the middle crystal is close to the theoretical value, and the difference in transmittance between the head and tail is small, indicating that the overall quality of the crystal still meets high standards, and only local areas may be slightly affected by changes in growth conditions.

[0048] The current-voltage (IV) test is a common technique for evaluating the resistivity of semiconductor materials and is widely used in the field of semiconductor nondestructive testing. In the present invention, a vacuum evaporation method is used to deposit gold (Au) electrodes on the upper and lower surfaces of the processed wafer to ensure the formation of a stable ohmic contact. In order to avoid the influence of leakage current on the test results, the crystal surface needs to be passivated using photoresist. The specific steps are as follows: first, the photoresist is coated on the Au electrode and dried on a heating table or naturally dried. Subsequently, the wafer is immersed in 10% H 2 O 2 The samples were immersed in the solution for 10 minutes, taken out and placed in acetone solution to remove the surface photoresist, and finally cleaned thoroughly with deionized water. Next, an Agilent 4155C semiconductor parameter analyzer was used to analyze the Cd 0.9 Mn 0.1 IV tests were performed on crystals at different positions of the Te ingot, and IV curves were measured in the bias voltage range of -100V to 100V, such as Fig.14 As shown. It can be observed from the figure that the current I and voltage V of the sample show a good linear relationship, which indicates that a stable ohmic contact is formed between the wafer and the electrode. Therefore, Ohm's law can be applied to calculate the resistivity of the crystal: (3) Where R is the resistance of the crystal; S is the area of ​​the evaporated Au electrode; L is the thickness of the crystal; V is the test voltage; I is the current under the test voltage V.

[0049] Depend on Fig.14 The data in combined with formula (3) were used to calculate Cd 0.9 Mn 0.1 The resistivity of the crystals at different positions of the Te ingot is shown in Table 1.

[0050] It can be observed from Table 1 that Cd 0.9 Mn 0.1 The resistivity of each part of Te ingot has reached 10 10Ω·cm, indicating that the crystal exhibits highly uniform and stable electrical properties throughout the ingot. This may be due to the small number of free carriers in the semiconductor material or the high integrity of the material structure, which reduces the migration of carriers. Among the crystals at different locations, the resistivity of the middle crystal is slightly higher than that of the head and tail, indicating that the crystallization quality of the middle crystal is better, a result consistent with the findings in the optical study.

[0051] Table 1Cd 0.9 Mn 0.1 Resistivity of crystals at different positions of Te:In / V ingot ( ρ ) Table 1 Resistivity (ρ) of crystals at different positions ofCd 0.9 Mn 0.1 Te ingot.

[0052] The above description is only a preferred embodiment of the present invention and is not intended to impose any limitation on the technical solution of the present invention. Those skilled in the art should understand that, without departing from the spirit and principles of the present invention, the technical solution can also be subjected to several simple modifications and substitutions, and these modifications and substitutions are also within the scope of protection covered by the claims.

Claims

1. A Cd 0.9 Mn 0.1 The method for preparing Te semiconductor crystal is characterized in that: The following steps are involved: S1, cleaning the crucible and evaporating a carbon film on the inner wall of the crucible; S2, solid raw materials Cd, Mn and Te are prepared in a molar ratio of 0.9:0.1:1.1 with Te in excess of 10%, and are loaded into the crucible with the carbon film in S1, and then the crucible is sealed and evacuated to a vacuum state for standby use; S3, combining the raw materials in the crucible to obtain a crude polycrystalline material; S4, the rough polycrystalline material grows under the vertical temperature gradient of three temperature zones to generate Cd 0.9 Mn 0.1 Te single crystal.

2. Cd according to claim 1 0.9 Mn 0.1 The method for preparing Te semiconductor crystal is characterized in that: In S1, during cleaning, different cleaning agents are used for multiple cleanings, and the cleaning agents used are deionized water, acetone solution, aqua regia solution, HF solution and deionized water.

3. Cd according to claim 1 0.9 Mn 0.1 The method for preparing Te semiconductor crystal is characterized in that: In S1, the specific process of evaporating the carbon film is: heating the acetone solution, cracking the acetone under an argon gas flow, and depositing the cracked carbon particles on the inner wall of the crucible to form a carbon film.

4. Cd according to claim 3 0.9 Mn 0.1 The method for preparing Te semiconductor crystal is characterized in that: The thickness of the carbon film is 20~50μm.

5. The method for preparing a CD0.9MN0.1TE semiconductor crystal according to claim 1, characterized in that: In S2, the purity of Cd is 7N or more, the purity of Mn is 5N or more, and the purity of Te is 7N or more.

6. Cd according to claim 1 0.9 Mn 0.1 The method for preparing Te semiconductor crystal is characterized in that: In S2, the vacuum degree in the crucible is 5×10 5 Pa.

7. Cd according to claim 1 0.9 Mn 0.1 The method for preparing Te semiconductor crystal is characterized in that: In S3, the mixing process includes heating, heat preservation and cooling, specifically: S31, raise the temperature from room temperature to 321°C at a rate of 20-30°C / h, and keep at 321°C for 1-2h; S32, reducing the heating rate to 10-20°C / h, continuing to heat to 450°C, and maintaining at 450°C for 5h; S33, increasing the heating rate to 30-40°C / h to 1090°C, and setting a longer holding time at this temperature as required, which is greater than the holding time required to meet the S34 and S35 operations; S34, then keep warm for 2 hours, and rock the crucible at a rocking speed of 1-2 r / min for 24 hours; S35, stop shaking, keep warm for 2 hours, and then cool naturally at room temperature to obtain a crude polycrystalline material.

8. Cd according to claim 1 0.9 Mn 0.1 The method for preparing Te semiconductor crystal is characterized in that: In S4, Cd is generated 0.9 Mn 0.1 The specific process of Te single crystal is: S41, set the temperature of three temperature zones from top to bottom, respectively recorded as the first temperature zone, the second temperature zone and the third temperature zone, and the temperature gradually decreases from top to bottom; the temperature satisfies the condition: when the crucible is in the middle of the inner space of the heating furnace, the tip of the crucible is at Cd 0.9 Mn 0.1 The growth point of Te is at 1030℃, and the temperature gradient 3~5cm below the growth point meets 10~15℃ / cm; S42, when the temperature meets the conditions, keep warm for 2 hours; S43, moving the crucible to a hot spot, and overheating for 24 hours to melt the coarse polycrystalline material; wherein the hot spot is a position 30° C. higher than the temperature at the growth point; S44, after overheating, move the crucible to the growth point and keep it warm for 2h; S45, under heat preservation conditions, the crucible is lowered by 10-15 cm at a speed of 0.2-0.25 mm / h, and the crystal begins to grow; S46, after the growth is completed, stop moving the crucible and keep warm for 2 hours; S47, after the insulation is completed, the temperature of the three temperature zones is set to 860°C, and the temperature is reduced to 860°C standard temperature within 10 hours, and the temperature is kept for 48 hours, and the crucible is annealed in situ; S48, after the annealing is completed, the temperature of the three temperature zones is lowered to 500°C at a cooling rate of 5°C / h, the furnace body is powered off, and the crucible is cooled naturally; after the furnace is cooled to room temperature, the crystal stops growing and is taken out to obtain Cd 0.9 Mn 0.1 Te single crystal.

9. A Cd according to any one of claims 1 to 8 0.9 Mn 0.1 The product obtained by the method for preparing Te semiconductor crystal.

10. A semiconductor device comprising the product as claimed in claim 9.

Images