Cadmium zinc telluride single crystal preparation method and device

Abstract

The invention provides a preparation method of a cadmium zinc telluride single crystal. The preparation method comprises the following steps: putting a cadmium zinc telluride raw material into a single crystal furnace for growth of the cadmium zinc telluride single crystal; in the single crystal furnace, a temperature control structure is arranged, so that a uniform temperature or a gradient temperature gradient along the radial direction of the single crystal furnace is formed in an area which is positioned between a tellurium-zinc-cadmium raw material and the furnace wall of the single crystal furnace and is flush with a solid-liquid interface for growth of the tellurium-zinc-cadmium single crystal; therefore, a tellurium-zinc-cadmium single crystal solid-liquid interface is guided to form a growth interface which is flat or slightly convex towards a tellurium-zinc-cadmium liquid phase. The temperature control structure is arranged in the single crystal furnace to perform temperature compensation on the growth interface temperature field of the tellurium-zinc-cadmium crystal, so that the uniformity of the temperature field near the growth interface of the crystal is improved, and the single crystal rate is favorably improved; and the radial temperature gradient control is realized through the temperature control structure to control the shape of the crystal growth interface temperature field, so that the whole crystal growth interface temperature field is beneficial to the growth of large single crystals, and the relatively small radial temperature gradient can reduce the generation of crystal defects and is beneficial to improving the crystal quality.

Description

Technical Field

[0001] The invention belongs to the technical field of crystal growth, and in particular relates to a method and a device for preparing a cadmium zinc telluride single crystal. Background Art

[0002] Cadmium zinc telluride (CZT) substrate material is the most ideal substrate material for HgCdTe epitaxy. The development of high-performance HgCdTe infrared focal plane devices, long-wave infrared focal plane devices, new HgCdTe avalanche infrared focal plane technology and high-temperature infrared focal plane technology depends on CdZnTe substrate materials. As infrared detectors have entered the third generation of infrared detector technology, large-scale, high-resolution, multi-band, high-integration, lightweight and low-cost have become the most concerned issues in infrared technology. Large-scale infrared detectors have higher spatial resolution and can expand the detection and identification range of targets. They have become an inevitable trend in the development of infrared detectors. Therefore, the first condition for preparing large-array infrared detectors is to develop large-size, high-quality CdZnTe substrates.

[0003] The melt method is currently the mainstream way to grow cadmium zinc telluride crystals. The principle is to first melt all the high-purity raw materials or polycrystalline materials at high temperature, and then use various growth techniques to make the melt slowly crystallize from the head to the tail of the crucible to obtain a single crystal.

[0004] However, compared with the crystal growth of semiconductor materials such as Si and GaAs, the physical properties of CZT are relatively special. It is a ternary alloy, and its physical properties determine that it is very difficult to grow such large single crystals: CZT's low thermal conductivity makes it difficult to dissipate the heat released during the crystallization process, making it difficult to form a flat or slightly convex solid-liquid interface shape toward the melt, and it is difficult to achieve full single crystal growth; at the same time, due to the small critical shear stress of cadmium zinc telluride, a very small radial temperature gradient will cause the thermal stress to exceed the critical shear stress of lattice slip and produce dislocations. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing a cadmium zinc telluride single crystal, which can at least solve some of the defects existing in the prior art.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] A method for preparing a cadmium zinc telluride single crystal comprises the following steps:

[0008] placing a cadmium zinc telluride raw material in a single crystal furnace to grow a cadmium zinc telluride single crystal;

[0009] In the single crystal furnace, by setting a temperature control structure, a uniform temperature or a gradual temperature gradient is formed along the radial direction of the single crystal furnace in a region located between the CdZnTe raw material and the furnace wall of the single crystal furnace and flush with the solid-liquid interface of the CdZnTe single crystal growth, so as to guide the solid-liquid interface of the CdZnTe single crystal to form a flat growth interface or a slightly convex growth interface toward the CdZnTe liquid phase.

[0010] Furthermore, in an area located between the cadmium zinc telluride raw material and the wall of the single crystal furnace and flush with the solid-liquid interface of the cadmium zinc telluride single crystal growth, multiple temperature measuring points are set along the radial direction of the single crystal furnace for real-time temperature measurement, and the annular area concentric with the solid-liquid interface of the cadmium zinc telluride single crystal where each temperature measuring point is located is heated through a temperature control structure so that the annular area where each temperature measuring point is located reaches its respective design temperature.

[0011] Furthermore, when a temperature gradient gradually changing radially along the single crystal furnace is designed to be formed in an area flush with the solid-liquid interface of the cadmium zinc telluride single crystal growth, the temperature of the annular area where each temperature measuring point is located is controlled by the temperature control structure to increase gradually from the cadmium zinc telluride single crystal growth position toward the single crystal furnace wall.

[0012] Furthermore, the temperature difference between the annular areas where two adjacent temperature measuring points are located is no more than 2°C.

[0013] Specifically, the above-mentioned method for preparing cadmium zinc telluride single crystal comprises the following steps:

[0014] S1, loading the CdZnTe raw material into a CdZnTe single crystal growth container;

[0015] S2, placing the cadmium zinc telluride single crystal growth container into the single crystal furnace;

[0016] S3, placing a temperature control structure between the inner cavity wall of the single crystal furnace and the CdZnTe single crystal growth container, and placing the temperature control structure near the CdZnTe single crystal growth melting point according to the designed single crystal furnace temperature field to grow the CdZnTe single crystal;

[0017] S4, by measuring the temperature of the annular area where each temperature measuring point is located, adjusting the position of the temperature control structure so that it is on the same plane as the solid-liquid interface of the cadmium zinc telluride single crystal growth, and controlling the temperature of the annular area where each temperature measuring point is located to be stable at its respective design temperature value;

[0018] S5. Directly move the CdZnTe single crystal growth container to grow the CdZnTe single crystal.

[0019] In addition, the present invention also provides a cadmium zinc telluride single crystal preparation device, including a single crystal furnace and a cadmium zinc telluride single crystal growth container arranged in the single crystal furnace for containing cadmium zinc telluride raw materials, a temperature control structure is provided between the furnace wall of the single crystal furnace and the cadmium zinc telluride single crystal growth container, which is used to control the formation of a uniform temperature or a gradual temperature gradient along the radial direction of the single crystal furnace in an area located between the cadmium zinc telluride raw materials and the furnace wall of the single crystal furnace and flush with the solid-liquid interface of the cadmium zinc telluride single crystal growth, and a lifting component is provided in the single crystal furnace for driving the cadmium zinc telluride single crystal growth container to rise and fall.

[0020] Furthermore, the temperature control structure includes a plurality of groups of directional temperature control rings arranged at intervals along the radial direction of the single crystal furnace, and the directional temperature control rings are fixed in the single crystal furnace by a plurality of heat conducting rods arranged at equal intervals along the circumference of the directional temperature control rings.

[0021] Furthermore, at least one of the heat-conducting rods connected to each of the directional temperature-controlling rings is a hollow structure, which is used to install a temperature measuring element for detecting the temperature of the directional temperature-controlling ring.

[0022] A plurality of groups of directional temperature control rings are concentrically arranged.

[0023] Furthermore, each two adjacent groups of directional temperature control rings are fixedly connected.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The method for preparing a cadmium zinc telluride single crystal provided by the present invention provides a temperature control structure in a single crystal furnace to perform temperature compensation and reinforcement on the temperature field of the cadmium zinc telluride crystal growth interface, thereby improving the uniformity of the temperature field near the crystal growth interface and facilitating the improvement of the single crystal rate; and radial temperature gradient control is achieved through the temperature control structure, so as to form a uniform temperature or gradual temperature gradient along the radial direction of the single crystal furnace in a region located between the cadmium zinc telluride raw material and the furnace wall of the single crystal furnace and flush with the solid-liquid interface of the cadmium zinc telluride single crystal growth, thereby controlling the shape of the crystal growth interface temperature field, adjusting the entire crystal growth interface temperature field to an approximately flat or slightly convex interface that is conducive to the growth of single crystals, facilitating the growth of large single crystals, and a smaller radial temperature gradient can reduce the generation of crystal defects and facilitate improving the crystal quality.

[0026] The present invention will be further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic structural diagram of a cadmium zinc telluride single crystal preparation device of the present invention;

[0028] Figure 2 It is a schematic diagram of the arrangement of multiple groups of directional temperature control rings in an embodiment of the present invention.

[0029] Explanation of the reference numerals: 1. crystal furnace; 2. directional temperature control ring; 3. heat conducting rod; 4. PBN crucible; 5. cadmium zinc telluride raw material; 6. quartz crucible; 7. temperature measuring element. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] In the description of the present invention, it should be understood that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0032] In the description of the present invention, it should be noted that, unless otherwise clearly stipulated and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, a conflicting connection or an integral connection. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0033] The terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features; in the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0034] Embodiment 1:

[0035] During the growth of CZT, the thermal stress (σ) exceeds the critical shear stress (α) for lattice slip. CRSS ), the crystal releases stress through dislocation formation, and the simplified calculation method of σ value is as follows:

[0036]

[0037] Where α T is the thermal expansion coefficient of CZT (6.36×10 -6 ℃ -1 ), E is its Young's modulus (5×10 10 Pa), L is the characteristic length, T is the temperature, z is the axial direction of the pulling growth, δ Tmax The maximum allowable deviation between the isotherm and the line shape. The linear isotherm deviation δ of 1 to 2 K Tmax Very small, enough to reach the critical resolution shear stress (CRSS) for dislocation multiplication (0.3MPa).

[0038] It can be seen from the above calculation formula that the greater the radial temperature gradient, the greater the thermal stress generated, and the easier it is to exceed the critical shear stress of lattice slip and produce dislocations. During the growth of CZT crystals, the maximum stress generally occurs after solidification is completed, when the thermal stress exceeds the critical shear stress of lattice slip, and the crystal releases stress through dislocation formation. The greater the radial temperature gradient, the higher the thermal stress generated, and the easier it is to exceed the critical shear stress of lattice slip and produce dislocations.

[0039] Based on the above analysis, this embodiment provides a method for preparing a cadmium zinc telluride single crystal, which reduces the generation of crystal defects by controlling the radial temperature gradient during the growth of the CZT crystal. Specifically, Figure 1 and Figure 2 As shown, the process includes the following steps: placing a CdZnTe raw material 5 in a single crystal furnace 1 to grow a CdZnTe single crystal. In the single crystal furnace 1, a temperature control structure is provided to form a uniform temperature or a gradual temperature gradient along the radial direction of the single crystal furnace 1 in a region between the CdZnTe raw material 5 and the furnace wall of the single crystal furnace 1 and flush with the solid-liquid interface of the CdZnTe single crystal growth, so as to guide the solid-liquid interface of the CdZnTe single crystal to form a growth interface that is approximately flat or slightly convex to the CdZnTe liquid phase. During the heating process of the crystal furnace 1, different temperature field sections with increasing temperatures from bottom to top are formed in the crystal furnace 1. In this embodiment, a temperature control structure is added to the high temperature zone, and the temperature of the temperature control structure is controlled to form a radial temperature gradient control, stabilize the solid-liquid interface morphology of the CdZnTe crystal, guide the interface gradient, and make the CdZnTe single crystal have a smaller radial temperature gradient during the growth process, thereby achieving better single crystal interface growth, and improving the single crystal rate and crystal quality of crystal growth.

[0040] In a detailed implementation method, in an area located between the cadmium zinc telluride raw material 5 and the furnace wall of the single crystal furnace 1 and flush with the solid-liquid interface of the cadmium zinc telluride single crystal growth, multiple temperature measuring points are set along the radial direction of the single crystal furnace 1 for real-time temperature measurement, and the annular area concentric with the solid-liquid interface of the cadmium zinc telluride single crystal where each temperature measuring point is located is heated through a temperature control structure so that the annular area where each temperature measuring point is located reaches its respective design temperature.

[0041] Specifically, when a temperature gradient gradually changing radially along the single crystal furnace 1 is formed in a region flush with the solid-liquid interface of the CdZnTe single crystal growth, the temperature of the annular region where each temperature measuring point is located is controlled by the temperature control structure to increase gradually from the CdZnTe single crystal growth position toward the furnace wall of the single crystal furnace 1; this design can more stably supplement heat to the CdZnTe crystal growth interface (i.e., the solid-liquid interface), control the shape of the growth interface temperature field, and adjust the entire growth interface temperature field to an approximately flat or slightly convex interface that is conducive to single crystal growth.

[0042] Preferably, the temperature difference between the annular regions where two adjacent temperature measuring points are located is controlled to be no greater than 2° C., and the generation of crystal defects is reduced by setting a smaller radial temperature gradient.

[0043] Embodiment 2:

[0044] This embodiment provides a CdZnTe single crystal preparation device, which can be applied to the above-mentioned CdZnTe single crystal preparation method, such as Figure 1 and Figure 2 As shown, it includes a single crystal furnace 1 and a CdZnTe single crystal growth container arranged in the single crystal furnace 1 for containing CdZnTe raw materials. A temperature control structure is provided between the furnace wall of the single crystal furnace 1 and the CdZnTe single crystal growth container, which is used to control the formation of a uniform temperature or a gradual temperature gradient along the radial direction of the single crystal furnace in an area located between the CdZnTe raw material 5 and the furnace wall of the single crystal furnace 1 and flush with the solid-liquid interface of the CdZnTe single crystal growth. A lifting component is provided in the single crystal furnace 1 for driving the CdZnTe single crystal growth container to rise and fall.

[0045] The CdZnTe single crystal growth container includes a quartz crucible 6 and a PBN crucible 4, a CdZnTe raw material 5 is contained in the PBN crucible 4, the PBN crucible 4 is placed in the quartz crucible 6, the quartz crucible 6 is placed in the single crystal furnace 1, and the temperature control structure is placed between the single crystal furnace 1 and the quartz crucible 6. The lifting assembly can be a supporting device arranged below the quartz crucible 6 to support the quartz crucible 6, driving the quartz crucible 6 to descend, so that the CdZnTe crystal is transformed from a molten state in a high temperature zone to a solid state in a low temperature zone, thereby completing crystal growth.

[0046] As a specific implementation method, the temperature control structure includes a plurality of groups of directional temperature control rings 2 radially spaced apart along the single crystal furnace 1; as for the fixing method of the directional temperature control ring 2 in the single crystal furnace 1, in some embodiments, the directional temperature control ring 2 is fixed in the single crystal furnace 1 by a plurality of heat-conducting rods 3 equidistantly spaced apart along its own circumference. Specifically, the heat-conducting rods 3 are arranged perpendicular to the directional temperature control ring 2, the bottom end of the heat-conducting rod 3 is fixed to the directional temperature control ring 2, and the top end passes through the top of the single crystal furnace 1. The setting of the heat-conducting rod 3 can not only drive the directional temperature control ring 2 to move and adjust the position of the directional temperature control ring 2, but also the heat-conducting rod 3 can play a heat-conducting role to heat the directional temperature control ring 2 so that the directional temperature control ring 2 reaches the desired temperature designed for it; and each directional temperature control ring 2 is independently provided with a heat-conducting rod 3 for independent temperature control.

[0047] Preferably, among the several heat-conducting rods 3 connected to each of the directional temperature control rings 2, at least one heat-conducting rod 3 is designed to be a hollow structure, which is used to install a temperature measuring element 7 for detecting the temperature of the directional temperature control ring 2. The temperature measuring element 7 can be but is not limited to a temperature sensor. The temperature of the directional temperature control ring 2 is monitored in real time by the temperature measuring element 7 to ensure that the cadmium zinc telluride crystal is always in a set radial temperature gradient temperature field for single crystal growth, thereby improving the crystal quality.

[0048] Preferably, multiple groups of directional temperature control rings 2 are arranged concentrically to ensure uniform crystal temperature distribution. In order to ensure that all directional temperature control rings 2 are in the same horizontal plane, that is, the plane where the solid-liquid interface of the CdZnTe single crystal is grown, each two adjacent groups of directional temperature control rings 2 can be fixedly connected, so that in the crystal furnace 1, only one search is needed to find the CdZnTe single crystal growth interface position, thereby improving the positioning efficiency of the directional temperature control rings 2.

[0049] Optionally, the directional temperature control ring 2 in this embodiment can be an integral circular ring structure, or a circular ring structure composed of multiple arc segments, wherein each arc segment is provided with an independent temperature measuring and heating element, so as to realize precise control of the omnidirectional temperature uniformity of the solid-liquid interface during the growth of cadmium zinc telluride single crystals.

[0050] The following is a specific embodiment to illustrate the method for preparing a cadmium zinc telluride single crystal of the present invention. Specifically, taking the setting of three sets of directional temperature control rings as an example, the specific preparation process is as follows:

[0051] S1, put the cadmium zinc telluride raw material 5 into the PBN crucible 4 located in the quartz crucible 6, and evacuate and seal the quartz crucible 6, wherein the vacuum degree of the vacuum seal is 1 to 10×10 -5 Pa.

[0052] S2, placing the vacuum sealed quartz crucible 6 into the single crystal furnace 1.

[0053] S3. Place multiple groups of directional temperature control rings 2 between the inner cavity wall of the single crystal furnace 1 and the quartz crucible 6, and place three groups of directional temperature control rings 2 near the melting point temperature field of CdZnTe single crystal growth according to the designed temperature field of the single crystal furnace 1 to grow CdZnTe single crystal.

[0054] S4. By measuring the temperature of the directional temperature control ring 2 close to the quartz crucible 6 and adjusting the position of the directional temperature control ring, the crystallization temperature (i.e., 1098°C) position of the CdZnTe crystal is found so that it is on the same plane as the solid-liquid interface (i.e., the crystallization temperature position) of the CdZnTe single crystal growth, the directional temperature control ring 2 is heated and the temperature of the directional temperature control ring 2 is controlled to be stable at 1098°C.

[0055] S5. Adjust the positions of the remaining two groups of directional temperature control rings 2 so that the three groups of directional temperature control rings 2 are all located on the plane where the CdZnTe single crystal growth interface is located, and control the temperatures of the remaining two groups of directional temperature control rings 2 to be stable at their respective designed temperature values. Specifically, measure the temperature of the middle directional temperature control ring 2, and heat and control its temperature to be stable at 1100°C; measure the temperature of the directional temperature control ring 2 close to the inner wall of the crystal furnace 1, and heat and control its temperature to be stable at 1102°C.

[0056] S6. The quartz crucible 6 is lowered at a speed of 1 mm / h to grow a cadmium zinc telluride single crystal.

[0057] The above examples are merely illustrative of the present invention and do not constitute a limitation on the protection scope of the present invention. All designs that are the same or similar to the present invention fall within the protection scope of the present invention.

Claims

1. A method for preparing a cadmium zinc telluride single crystal, characterized in that: The process includes the following: placing a cadmium zinc telluride raw material in a single crystal furnace to grow a cadmium zinc telluride single crystal; In the single crystal furnace, by setting a temperature control structure, a uniform temperature or a gradual temperature gradient is formed along the radial direction of the single crystal furnace in a region located between the CdZnTe raw material and the furnace wall of the single crystal furnace and flush with the solid-liquid interface of the CdZnTe single crystal growth, so as to guide the solid-liquid interface of the CdZnTe single crystal to form a flat growth interface or a slightly convex growth interface toward the CdZnTe liquid phase.

2. The method for preparing a cadmium zinc telluride single crystal according to claim 1, characterized in that: In an area located between the CdZnTe raw material and the wall of the single crystal furnace and flush with the solid-liquid interface of the CdZnTe single crystal growth, multiple temperature measuring points are set along the radial direction of the single crystal furnace for real-time temperature measurement, and the annular area concentric with the solid-liquid interface of the CdZnTe single crystal where each temperature measuring point is located is heated through a temperature control structure so that the annular area where each temperature measuring point is located reaches its respective design temperature.

3. The method for preparing a cadmium zinc telluride single crystal according to claim 2, characterized in that: When a temperature gradient gradually changing radially along the single crystal furnace is designed to be formed in an area flush with the solid-liquid interface of the CdZnTe single crystal growth, the temperature of the annular area where each temperature measuring point is located is controlled by the temperature control structure to increase gradually from the CdZnTe single crystal growth position toward the single crystal furnace wall.

4. The method for preparing a cadmium zinc telluride single crystal according to claim 3, characterized in that: The temperature difference between the annular areas where two adjacent temperature measuring points are located is no more than 2°C.

5. The method for preparing a cadmium zinc telluride single crystal according to any one of claims 2 to 4, characterized in that: The steps include: S1, placing the CdZnTe raw material into a CdZnTe single crystal growth container; S2, placing the cadmium zinc telluride single crystal growth container into the single crystal furnace; S3, placing a temperature control structure between the inner cavity wall of the single crystal furnace and the CdZnTe single crystal growth container, and placing the temperature control structure near the CdZnTe single crystal growth melting point according to the designed single crystal furnace temperature field to grow the CdZnTe single crystal; S4, by measuring the temperature of the annular area where each temperature measuring point is located, adjusting the position of the temperature control structure so that it is on the same plane as the solid-liquid interface of the cadmium zinc telluride single crystal growth, and controlling the temperature of the annular area where each temperature measuring point is located to be stable at its respective design temperature value; S5. Directly move the CdZnTe single crystal growth container to grow the CdZnTe single crystal.

6. A cadmium zinc telluride single crystal preparation device, characterized in that: The invention comprises a single crystal furnace and a CdZnTe single crystal growth container which is arranged in the single crystal furnace and used for containing CdZnTe raw materials. A temperature control structure is arranged between the furnace wall of the single crystal furnace and the CdZnTe single crystal growth container, which is used for controlling a uniform temperature or a gradual temperature gradient along the radial direction of the single crystal furnace in a region which is located between the CdZnTe raw materials and the furnace wall of the single crystal furnace and is flush with the solid-liquid interface of the CdZnTe single crystal growth. A lifting component is arranged in the single crystal furnace and used for driving the CdZnTe single crystal growth container to rise and fall.

7. The cadmium zinc telluride single crystal preparation device according to claim 6, characterized in that: The temperature control structure comprises a plurality of groups of directional temperature control rings arranged at intervals along the radial direction of the single crystal furnace. The directional temperature control rings are fixed in the single crystal furnace by a plurality of heat conducting rods arranged at equal intervals along the circumference of the directional temperature control rings.

8. The cadmium zinc telluride single crystal preparation device according to claim 7, characterized in that: At least one of the heat-conducting rods connected to each of the directional temperature-controlling rings is a hollow structure, and is used for installing a temperature measuring element for detecting the temperature of the directional temperature-controlling ring.

9. The cadmium zinc telluride single crystal preparation device according to claim 7, characterized in that: A plurality of groups of directional temperature control rings are concentrically arranged.

10. The cadmium zinc telluride single crystal preparation device according to claim 9, characterized in that: Every two adjacent groups of directional temperature control rings are fixedly connected.

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