Device and method for batch production of large-area lead salt semiconductor single crystal thin film

Abstract

The application relates to a device and a method for batch preparing large-area lead salt semiconductor single crystal thin films. The device comprises a multi-section vacuum tube furnace, a gas source, a vacuum pump, a heating and temperature control device; the multi-section vacuum tube furnace comprises a reaction source placement area, a constant-temperature heating area and a temperature control deposition area. The large-area lead salt semiconductor single crystal thin film is grown on a vertically placed substrate and obtained through chemical vapor deposition by using the vacuum tube furnace and the heating and temperature control device. Through the control of the temperature gradient of the temperature control deposition area, the reaction source, the deposition time, the gas flow and the growth substrate, the film thickness, the film area, the surface morphology, the grain size and the single crystal property of the lead salt semiconductor thin film are controlled. The application can effectively solve the problem that the lead salt semiconductor single crystal thin film is difficult to be prepared with high efficiency and in a large area, and promote the realization of a low-cost, room-temperature-working high-resolution focal plane infrared detector.

Description

Technical Field

[0001] This invention belongs to the field of single-crystal thin film preparation technology, specifically relating to an apparatus and method for batch preparation of large-area lead salt semiconductor single-crystal thin films. Background Technology

[0002] Infrared photodetectors, upon absorbing infrared radiation from an object, visualize the infrared signal carrying the object's radiation characteristics through photoelectric conversion and electrical signal processing. This photoelectric conversion technology can be widely applied in low-light night vision, precision guidance, space remote sensing, near-infrared spectroscopy analysis, and other fields, promoting the development of my country's military and civilian industries, biomedicine, and aerospace.

[0003] Infrared photodetectors can be categorized into photonic infrared detectors and photothermal infrared detectors based on their working principle. Photonic detectors utilize infrared radiation to excite bound electrons, resulting in an electrical signal output. While photonic detectors offer higher performance limits and faster response times, they can generate noise due to the excitation of charge carriers at room temperature. Therefore, they typically operate in the liquid nitrogen temperature range, requiring high-vacuum Dewar flasks and high-capacity cryogenic units. Currently, the most widely used HgCdTe and InSb-based infrared detectors exhibit dark currents that increase orders of magnitude with temperature, hindering their widespread application. In contrast, photothermal infrared detectors utilize the temperature change of a photosensitive material caused by received infrared light, converting this temperature change into a measurable electrical signal. Consequently, photothermal detectors can operate at room temperature without cooling equipment, significantly reducing device size, weight, power consumption, and cost, making them a popular research area in infrared focal plane array technology.

[0004] Photothermal infrared detectors are primarily made of group IV-VI (e.g., PbS, PbSe, and PbTe) thin films, which belong to the lead salt semiconductor thin film category. Furthermore, single-crystal thin film materials possess lower defect state densities and lack grain boundaries, reducing electron scattering during transport and thus improving carrier mobility. These properties hold promise for enhancing the performance of infrared photodetectors. The main fabrication methods for these materials include chemical bath deposition (CBD) and electrochemical atomic layer deposition (ALD). CBD readily yields large-area PbS films, but the resulting films exhibit poor single-crystal properties. Electrochemical ALD produces single-crystal thin films that are expensive and difficult to fabricate in large areas. Therefore, there is an urgent need to develop a simple, low-cost, and mass-producible lead salt semiconductor single-crystal thin film fabrication apparatus and method to promote the widespread application of uncooled large-area infrared focal plane array detectors. Summary of the Invention

[0005] The purpose of this invention is to provide an apparatus and method for batch preparation of large-area lead salt semiconductor single crystal thin films. The large-area lead salt semiconductor single crystal thin films have the characteristics of large area and good single crystal properties. The thin films can be used to prepare large-area high-performance infrared detector arrays.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] An apparatus for mass production of large-area lead salt semiconductor single crystal thin films includes: a multi-segment vacuum tube furnace, a gas source, a vacuum pump, and a heating and temperature control device.

[0008] A multi-stage vacuum tube furnace, including a reaction source placement area, a constant temperature heating area, and a temperature-controlled deposition area;

[0009] The constant temperature heating zone can be divided into multiple sections according to the number of reaction sources involved, each with a different heating temperature. The number of sections can be adjusted by using an external heating ring.

[0010] Multiple substrates are arranged in an array in the temperature-controlled deposition zone, with the deposition surface perpendicular to the airflow direction. The temperature-controlled deposition zone controls the temperature of the constant-temperature heating zone, adjusts the heat preservation position of the deposition zone, or adjusts the gas source flow rate by monitoring the temperature distribution, thereby forming the optimal temperature gradient in the deposition area.

[0011] This invention also provides a method for batch preparation of large-area lead salt semiconductor single-crystal thin films, comprising the following steps:

[0012] S1. Place the high-purity reaction source in the reaction source placement area, and stand the cleaned multiple substrates vertically in the temperature-controlled deposition area, with the deposition surface of the substrate perpendicular to the gas flow direction.

[0013] S2. Turn on the vacuum pump and introduce gas. When the vacuum level in the tube is kept below 200Pa, the constant temperature heating zone will start heating.

[0014] S3. When the highest temperature in the constant temperature heating zone reaches above 600℃, the temperature of the constant temperature heating zone is finely adjusted by monitoring the temperature values ​​of temperature sensors at different locations in the deposition zone, or the insulation structure of the deposition zone is adjusted, or the gas source flow rate is adjusted to form the optimal temperature gradient in the deposition zone.

[0015] S4. Send the reaction source to the heating zone. After deposition for about 5-15 minutes, turn off the heating device. After the temperature inside the vacuum tube furnace drops to room temperature, turn off the gas source and remove the thin film with deposited lead salt semiconductor.

[0016] Furthermore, the optimal temperature gradient in the deposition area is controlled by using temperature values ​​monitored by temperature sensors at different locations in the deposition area, and by using a fuzzy PID algorithm embedded in the heating and temperature control device to fine-tune the temperature of the constant temperature heating area to form the optimal temperature gradient.

[0017] Alternatively, the optimal temperature gradient can be formed by manually adjusting the position and thickness of the insulation layer in the deposition area;

[0018] Alternatively, an optimal temperature gradient can be created by controlling the flow rate of the gas source;

[0019] Alternatively, a combination of the three methods mentioned above can be used to achieve the optimal temperature gradient.

[0020] Furthermore, multiple substrates are arranged in an array and placed vertically in the temperature-controlled deposition zone of the vacuum tube furnace. The deposition surface is perpendicular to the gas flow direction, and the effective deposition zone length does not exceed 5 cm.

[0021] Furthermore, the reaction sources include, but are not limited to, PbS, PbSe, PbTe, Pb, S, Se, and Te, and multiple reaction sources can participate in deposition simultaneously. The role of the reaction sources is to form thin films or change the elemental distribution of thin films, thereby playing a role in the regulation of thin films. According to the different evaporation temperatures of the reaction sources, they can be divided into low-temperature reaction sources and high-temperature reaction sources.

[0022] Furthermore, the substrate material includes, but is not limited to, commonly used substrate materials for the growth of two-dimensional materials such as strontium titanate, sapphire, sodium chloride, silicon, and magnesium oxide, as well as one of infrared window materials such as calcium fluoride, magnesium fluoride, and lithium fluoride, preferably strontium titanate.

[0023] Furthermore, the introduced gas may include, but is not limited to, inert gases such as nitrogen and argon, and may be mixed with reducing gases such as hydrogen and carbon monoxide in any way.

[0024] Furthermore, the constant temperature heating zone can be located outside the tubular furnace or inside the tubular furnace via an external heating device.

[0025] Furthermore, the reaction source and the substrate are arranged in the following order from the inlet to the outlet: low-temperature reaction source, high-temperature reaction source, and substrate.

[0026] Compared with the prior art, the beneficial effects of the present invention are:

[0027] This invention employs a low-pressure chemical vapor deposition (CVD) method. Gas is introduced into a vacuum tube furnace and a high vacuum level is maintained. The reaction source is then placed in the reaction source placement area, while the substrate is arranged in a matrix within the temperature-controlled deposition area. After the isothermal heating and temperature-controlled deposition areas have heated and stabilized, the reaction source is transported from the reaction source placement area to the isothermal heating area, at which point the CVD reaction begins. By controlling the temperature gradient in the temperature-controlled deposition area, as well as the reaction source, deposition time, gas flow rate, and growth substrate, large-area lead-salt semiconductor single-crystal thin films can be fabricated. The film thickness, area, surface morphology, grain size, and single-crystallinity of these films can also be controlled. This invention effectively solves the problem of high-efficiency, large-area fabrication of lead-salt semiconductor single-crystal thin films, promoting the realization of low-cost, room-temperature operating high-resolution focal plane infrared detectors. Attached Figure Description

[0028] Figure 1 These are schematic diagrams showing different configurations and forms of the reaction source placement area, the constant temperature heating area, and the temperature-controlled deposition area.

[0029] Figure 2 PbS is grown on a 3cm diameter strontium titanate substrate. x Se 1-x Single-crystal thin films;

[0030] Figure 3 This relates the deposition location temperature to the size of the grain boundaries in the PbS single-crystal thin film.

[0031] Figure 4 It is PbS x Se 1-x Electron micrographs and elemental analysis spectra of single-crystal thin films;

[0032] Figure 5 It is PbS x Se 1-x X-ray diffraction pattern of single-crystal thin film;

[0033] Figure 6 This is a schematic diagram of an apparatus for batch preparation of large-area lead salt semiconductor single crystal thin films according to Example 1;

[0034] Figure 7 This is a schematic diagram of an apparatus for batch preparation of large-area lead salt semiconductor single crystal thin films according to Example 2;

[0035] Figure 8 This is a schematic diagram of an apparatus for batch preparation of large-area lead salt semiconductor single crystal thin films according to Example 3.

[0036] Illustration: 1. Heating and temperature control device; 2. Quartz tube of tube furnace; 3. Strontium titanate sheet; 4. Argon gas; 5. Tube furnace; 6. Quartz boat; 7. Sulfur powder; 8. Selenium powder; 9. Lead sulfide powder; 10. Heating ring. Detailed Implementation

[0037] The present invention will be further described in conjunction with the accompanying drawings and embodiments.

[0038] Figure 1 These are schematic diagrams showing different configurations and forms of the reaction source placement area, the constant temperature heating area, and the temperature-controlled deposition area.

[0039] Example 1

[0040] This embodiment uses, as follows Figure 6 The apparatus shown is used for the mass production of large-area lead salt semiconductor single crystal thin films, comprising the following steps:

[0041] Step 1: Clean four strontium titanate sheets 3 with a diameter of 3cm and a thickness of 0.5mm in sequence with ultrapure water, acetone, isopropanol and anhydrous ethanol, respectively, using ultrasonic cleaning for 15 minutes each, and then air-dry them with inert gas.

[0042] Step 2: Weigh 0.1 g of lead sulfide powder 9, 0.3 g of sulfur powder 7, and 0.3 g of selenium powder 8, and place them in quartz boats 6 respectively; place four strontium titanate sheets 3 in two rows, vertically on quartz boats 6, with the polished surfaces of the four strontium titanate sheets 3 all facing the same side; use a three-zone tube furnace 5, and install a heating and temperature control device 1. Place the quartz boats carrying sulfur powder 7, selenium powder 8, and lead sulfide powder 9 into the quartz tube 2 of the tube furnace, in the reaction source placement area, and place the quartz boats 6 carrying strontium titanate sheets 3 in the temperature-controlled deposition area, with their polished surfaces facing the gas inlet direction; the outer diameter of the quartz tube 2 used in this embodiment is 60 mm, and the wall thickness is 3 mm;

[0043] Step 3: Connect the vacuum pump to the tube furnace and introduce argon gas 4, adjusting the gas flow rate to 150 sccm. When the vacuum level inside the furnace is below 200 Pa, the constant temperature heating zone begins to heat up. The sulfur powder heating zone is set to 190℃, the selenium powder heating zone to 390℃, and the lead sulfide powder heating zone to 800℃. The temperature in the temperature-controlled deposition zone gradually decreases in the direction of the airflow, with the high-temperature end at 480℃ and the low-temperature end at 170℃. After slowly heating for 60 minutes to reach the target conditions, push the quartz boat 6 carrying sulfur powder 7, selenium powder 8, and lead sulfide powder 9 into the corresponding heating zone. The deposition reaction begins, and the reaction time is 7 minutes. Then, shut down the vacuum tube furnace system and open the furnace chamber for rapid cooling to quickly stop the entire reaction, obtaining wafer-level single-crystal PbS. x Se 1-x film.

[0044] Figure 2 PbS is grown on a 3cm diameter strontium titanate substrate. x Se 1-x Single-crystal thin films. Figure 4 It is PbS x Se1-x Electron micrographs and elemental analysis spectra of single-crystal thin films. Figure 5 It is PbS x Se 1-x X-ray diffraction pattern of a single-crystal thin film.

[0045] Example 2

[0046] This embodiment uses, as follows Figure 7 The apparatus shown is used for the mass production of large-area lead salt semiconductor single crystal thin films, comprising the following steps:

[0047] Step 1: Clean four strontium titanate sheets 3 with a diameter of 5cm and a thickness of 0.5mm in sequence with ultrapure water, acetone, isopropanol and anhydrous ethanol, respectively, using ultrasonic cleaning for 15 minutes each, and then air-dry them with inert gas.

[0048] Step 2: Weigh 0.2 g of lead sulfide powder 9 and 0.6 g of sulfur powder 7, and place them in the quartz boat 6 respectively; place four strontium titanate sheets 3 in two rows on the quartz boat 6, with the polished surfaces of the four strontium titanate sheets 3 all facing the same side; use a single-temperature zone tube furnace 5, and install a heating and temperature control device 1. Install an external heating ring 10 on the outer extension of the quartz tube 2 near the air inlet. Place the quartz boat 6 carrying sulfur powder 7 and lead sulfide powder 9 into the quartz tube 2 of the tube furnace, in the reaction source placement area. Place the strontium titanate sheets 3 in the temperature-controlled deposition area, with their polished surfaces facing the air inlet direction; the outer diameter of the quartz tube 2 used in this embodiment is 120 mm and the wall thickness is 3 mm.

[0049] Step 3: Connect the vacuum pump to the tube furnace and introduce argon gas 4, adjusting the gas flow rate to 150 sccm. When the vacuum level inside the furnace is below 200 Pa, start heating the heating ring 10 and the constant temperature heating zone. Set the heating ring corresponding to sulfur powder 7 to 190°C and the heating zone for lead sulfide powder 9 to 800°C. Gradually decrease the temperature in the temperature-controlled deposition zone along the airflow direction, with the high-temperature end at 480°C and the low-temperature end at 170°C. Slowly heat for 60 minutes to reach the target conditions. Push the quartz boat 6 carrying sulfur powder 7 and lead sulfide powder 9 into the corresponding heating zone to start the deposition reaction. The reaction time is 7 minutes. Then, shut down the vacuum tube furnace system and open the furnace chamber for rapid cooling to quickly stop the entire reaction, obtaining a wafer-level single-crystal PbS thin film.

[0050] Example 3

[0051] This embodiment uses, as follows Figure 8 The apparatus shown is used for the mass production of large-area lead salt semiconductor single crystal thin films, comprising the following steps:

[0052] Step 1: Clean four strontium titanate sheets 3 with a diameter of 5cm and a thickness of 0.5mm in sequence with ultrapure water, acetone, isopropanol and anhydrous ethanol, respectively, using ultrasonic cleaning for 15 minutes each, and then air-dry them with inert gas.

[0053] Step 2: Weigh 0.2 g of lead sulfide powder 9 and 0.6 g of sulfur powder 7, and place them in the quartz boat 6 respectively; place four strontium titanate sheets 3 in two rows on the quartz boat 6, with the polished surfaces of the four strontium titanate sheets 3 all facing the same side; use a single-temperature zone tube furnace 5, and install a heating and temperature control device 1. Install an external heating ring 10 on the outer extension of the quartz tube 2 near the air inlet. Place the quartz boat 6 carrying sulfur powder 7 and lead sulfide powder 9 into the quartz tube 2 of the tube furnace, in the reaction source placement area. Place the strontium titanate sheets 3 in the temperature-controlled deposition area, with their polished surfaces facing the air inlet direction; the outer diameter of the quartz tube 2 used in this embodiment is 120 mm and the wall thickness is 3 mm.

[0054] Step 3: Connect the vacuum pump to the tube furnace and introduce argon gas 4, adjusting the gas flow rate to 150 sccm. When the vacuum level inside the furnace is below 200 Pa, start heating the heating ring 10, the constant temperature heating zone, and the heating and temperature control device 1. Set the heating ring corresponding to sulfur powder 7 to 190°C and the heating zone for lead sulfide powder 9 to 800°C. Gradually decrease the temperature in the temperature-controlled deposition zone along the airflow direction, with the high-temperature end at 480°C and the low-temperature end at 200°C. Slowly heat for 60 minutes to reach the target conditions. Push the quartz boat 6 carrying sulfur powder 7 and lead sulfide powder 9 into the corresponding heating zone to start the deposition reaction. The reaction time is 7 minutes. Then, shut down the vacuum tube furnace system and open the furnace chamber for rapid cooling to quickly stop the entire reaction, obtaining a wafer-level single-crystal PbS thin film.

[0055] Figure 3 This relates the deposition location temperature to the size of the grain boundaries in the PbS single-crystal thin film.

[0056] The above description merely illustrates preferred embodiments of the present invention, and while the description is relatively specific and detailed, it should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications, improvements, and substitutions without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. An apparatus for mass production of large-area lead salt semiconductor single crystal thin films, characterized in that, include: Multi-stage vacuum tube furnace, gas source, vacuum pump, heating and temperature control device; The multi-segment vacuum tube furnace includes a reaction source placement area, a constant temperature heating area, and a temperature-controlled deposition area arranged sequentially along the gas flow direction. The constant temperature heating zone includes at least a heating section for a low-temperature reaction source and a heating section for a high-temperature reaction source, with different heating temperatures for different heating sections; Multiple substrates are arrayed within the temperature-controlled deposition zone. The substrates are vertically positioned within the temperature-controlled deposition zone, with the deposition surface of the substrates perpendicular to the airflow direction. The temperature-controlled deposition zone is equipped with multiple temperature sensors along the airflow direction to monitor the temperature distribution at different locations within the zone. The heating and temperature control device adjusts the temperature of the constant temperature heating zone and / or the heat preservation structure of the deposition zone and / or the gas source flow rate according to the temperature distribution, so that the temperature-controlled deposition zone forms a temperature gradient that decreases along the airflow direction. The multiple substrates are arranged within the effective deposition zone, and the length of the effective deposition zone does not exceed 5 cm. The reaction source includes a low-temperature reaction source and a high-temperature reaction source in sequence along the airflow direction, and the substrate is located downstream of the high-temperature reaction source.

2. A method for batch preparation of large-area lead salt semiconductor single crystal thin films, said method being implemented using the apparatus for batch preparation of large-area lead salt semiconductor single crystal thin films as described in claim 1, characterized in that, Includes the following steps: S1. Place the low-temperature reaction source and the high-temperature reaction source in the reaction source placement area, and place the cleaned multiple substrates vertically in the temperature-controlled deposition area, with the deposition surface of the substrate perpendicular to the gas flow direction. S2. Turn on the vacuum pump and introduce gas. When the vacuum level inside the tube is lower than 200Pa, heat the constant temperature heating zone. S3. When the highest temperature in the constant temperature heating zone reaches above 600℃, the temperature distribution is monitored by multiple temperature sensors set at different locations in the temperature-controlled deposition zone. Based on this, the temperature of the constant temperature heating zone is finely adjusted and / or the insulation structure of the deposition zone is adjusted and / or the gas source flow rate is adjusted, so that the temperature-controlled deposition zone forms a temperature gradient that decreases along the airflow direction, and multiple substrates are located in an effective deposition zone with a length not exceeding 5cm. S4. Send the low-temperature reaction source and the high-temperature reaction source to the corresponding heating section. After deposition for 5-15 minutes, turn off the heating device. After the temperature inside the vacuum tube furnace drops to room temperature, turn off the gas source and remove the substrate with the deposited lead salt semiconductor single crystal thin film.

3. The method for batch preparation of large-area lead salt semiconductor single crystal thin films as described in claim 2, characterized in that, The temperature of the constant temperature heating zone is fine-tuned by using a fuzzy PID algorithm embedded in the heating and temperature control device, based on the temperature values ​​monitored by multiple temperature sensors.

4. The method for batch preparation of large-area lead salt semiconductor single crystal thin films as described in claim 2, characterized in that, The reaction source includes one or more of PbS, PbSe, PbTe, Pb, S, Se or Te. The reaction source is classified into low-temperature reaction source and high-temperature reaction source according to the different evaporation temperatures of the reaction source.

5. The method for batch preparation of large-area lead salt semiconductor single crystal thin films as described in claim 2, characterized in that, The substrate material includes strontium titanate, sapphire, sodium chloride, silicon or magnesium oxide, or calcium fluoride, magnesium fluoride, lithium fluoride.

6. The method for batch preparation of large-area lead salt semiconductor single crystal thin films as described in claim 2, characterized in that, The introduced gas may contain nitrogen or an inert gas.

7. The method for batch preparation of large-area lead salt semiconductor single crystal thin films as described in claim 2, characterized in that, The low-temperature reaction source, the high-temperature reaction source, and the substrate are arranged sequentially from the air inlet to the air outlet.

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