Method for growing aluminum nitride thick film by hydride vapor phase epitaxy method

Abstract

The invention provides a method for growing an aluminum nitride thick film through a hydride vapor phase epitaxy method, and belongs to the technical field of third-generation semiconductor material preparation. According to the method, an aluminum source area in HVPE equipment is improved, supply of a multi-partition independent control aluminum source is provided, a periodic etching control strategy of an HCl gas channel is introduced, and a nested collaborative epitaxy method of outer-layer aluminum source rotation and inner-layer growth cycle embedded etching is formed. The problems of aluminum source degradation, nozzle blockage and stress accumulation in existing HVPE growth can be effectively solved, and long-time continuous operation of epitaxial AlN of the HVPE equipment is achieved; interruption and replacement operations caused by degradation of the aluminum source in long-time growth are avoided; nozzle area deposition is effectively removed, and the flow field stability is maintained; the stress is dynamically released, the crack occurrence rate is reduced, the film layer integrity is improved, and the method is suitable for HVPE equipment transformation and upgrading.

Description

Technical Field

[0001] This invention belongs to the field of third-generation semiconductor material preparation technology, specifically relating to a method for growing aluminum nitride (AlN) thick films using hydride vapor phase epitaxy (HVPE). More specifically, it relates to an epitaxial method combining a multi-zone continuous aluminum source supply device and a periodic etching control strategy, aiming to improve the epitaxial capability of AlN thick films, suppress crack formation, improve crystal quality, and thus achieve the preparation of high-quality, crack-free AlN thick films. Background Technology

[0002] In recent years, AlGaN-based deep ultraviolet (DUV) optoelectronic devices and electronic devices have developed rapidly, leading to an increasing demand for high-quality, long-life DUV optoelectronic devices. This places higher demands on the materials themselves. Traditional epitaxial substrates typically use materials such as sapphire and silicon (111), but due to the mismatch between their lattice constants and thermal expansion coefficients with AlN, a large amount of stress and defects are easily generated during heteroepitaxial growth. Homoepitaxial growth on AlN substrates can overcome the problem of lattice constant and thermal expansion coefficient mismatch. At the same time, the high thermal conductivity of AlN provides a heat dissipation advantage, which helps to extend the lifespan of DUV optoelectronic devices. Therefore, the preparation of high-quality, high-transmittance AlN single-crystal substrates is of great significance for the application of DUV optoelectronic devices.

[0003] Hydride vapor phase epitaxy (HVPE) is one of the main methods for preparing AlN single crystal substrates. However, the HVPE method still faces a series of technical challenges in achieving long-term continuous growth of AlN thick films. These challenges are mainly reflected in the following three aspects: (1) Deterioration of aluminum source: After long-term operation in a high-temperature, hydrogen chloride mixed atmosphere, the aluminum source surface may experience oxidation, chlorination by-product deposition, etc., which leads to a decrease in the reactivity of the aluminum source and a decrease in the growth rate, thus hindering the long-term growth of AlN. (2) Nozzle clogging: Since the pre-reaction products of AlCl3 and NH3 may be deposited in the nozzle area, long-term operation can easily cause nozzle clogging, which in turn leads to flow field disturbance and affects growth. (3) Stress accumulation: During AlN epitaxy, due to high-temperature growth (>1400℃) and the lattice mismatch and thermal expansion coefficient mismatch between the substrate (such as sapphire, SiC) and AlN, the film layer is prone to accumulate internal stress, which induces crack generation and reduces the yield. Therefore, to achieve high-quality, long-term epitaxial growth of thick AlN films, a solution is urgently needed that can balance aluminum source activity maintenance, nozzle stable operation, and dynamic stress release. An existing patent (CN202311559319.3) proposes reducing the impact of thermal radiation on the aluminum source through a light-blocking and flow-through device, thereby delaying its degradation. However, it still cannot prevent the accumulation of byproducts on the aluminum source surface, which could lead to reaction termination and hinder long-term continuous growth. Previous research (Liu et al., 2016) indicates that introducing an in-situ HCl etching stage during HVPE can reconstruct the AlN surface, remove defects, and release local stress, thereby improving film quality. However, this method lacks a system design for periodic etching control of the equipment and is not integrated with the aluminum source supply system or gas path, making it difficult to apply to long-term continuous thick film growth. Summary of the Invention

[0004] This invention relates to a method for growing high-quality aluminum nitride (AlN) thick films by hydride vapor phase epitaxy (HVPE), the core of which is to propose an epitaxy method that combines multi-zone continuous aluminum source supply with a periodic control strategy.

[0005] The present invention proposes the following technical solution:

[0006] A method for growing aluminum nitride thick films using hydride vapor phase epitaxy (HVPE) is characterized in that, in the HVPE equipment, the aluminum source reaction chamber is divided into multiple mutually enclosed individual chambers as partitions, each partition containing an aluminum boat and equipped with independent HCl and N2 gas inlets; the HVPE equipment is equipped with an NH3 gas path and an isolation gas path (ID gas path), and an HCl gas channel is added to the ID gas path, the HCl gas channel being equipped with a gas flow control component; used for in-situ etching and removal of pre-reaction products deposited in the nozzle and reaction chamber wall areas; by manually or automatically switching and alternately introducing reaction gases into each partition, a long-term stable supply of AlCl3 is achieved, combined with periodic HCl etching, to achieve the growth of AlN thick films. The specific process includes the following steps:

[0007] 1) Complete the preparations before AlN thick film growth, and bring the HVPE equipment to the set initial temperature, pressure and atmosphere conditions;

[0008] 2) Select a partition as the AlCl3 precursor supply area and periodically execute the "growth → etching → purging" process cycle for several rounds;

[0009] 3) When it is detected that the aluminum source of the partition is basically exhausted or the planned growth time of the partition is reached, switch to another partition and repeat step 2).

[0010] 4) Repeat steps 2)-3) until all partitions have finished growing.

[0011] Furthermore, the number of individual chambers ranges from 2 to 8.

[0012] Furthermore, the HCl gas flow rate in the HCl gas channel ranges from 0 to 1000 sccm.

[0013] Furthermore, the preparation steps before AlN thick film growth in step 1) specifically include:

[0014] 1-1) Load high-purity metallic aluminum into the aluminum boats of each zone, and load the substrate to be grown into the designated area of ​​the reaction chamber;

[0015] 1-2) Evacuate the equipment to achieve the set vacuum level;

[0016] 1-3) Introduce dry inert gas for gas replacement and purging to improve the purity of the equipment;

[0017] 1-4) Start the heating system, heat the reaction zone and non-reaction zone to the set temperature respectively, and set the heating rate and heating power;

[0018] 1-5) Once the temperature and pressure have stabilized within the preset range, the initialization preparation is complete, and the system enters the standby state before epitaxial growth.

[0019] Furthermore, the specific steps of growth in step 2) include:

[0020] 2-1) In this zone, 10–200 sccm of HCl gas is introduced to react with aluminum to generate AlCl3 precursor, and 100–3000 sccm of N2 is introduced as carrier gas. At the same time, other zones maintain N2 gas supply, with a flow rate equal to the sum of the HCl and N2 flow rates in the AlCl3 precursor supply zone.

[0021] 2-2) Simultaneously open the ID gas path and introduce N2 at a flow rate of 50-2000 sccm as an isolation gas to reduce pre-reaction;

[0022] 2-3) Simultaneously turn on the NH3 gas path and introduce NH3 gas at a flow rate of 500–8000 sccm. It reacts with AlCl3 in the high-temperature zone to generate AlN, thereby achieving epitaxial deposition. The growth time is 5–30 minutes.

[0023] Furthermore, the specific etching steps in step 2) are as follows: the HCl gas supply to the aluminum source zone is turned off, the NH3 gas supply to the NH3 gas path is turned off, the HCl gas channel in the ID gas path is opened, and 5–100 sccm of HCl gas is introduced to act on the nozzle area and the sample surface. The etching time is set to 1–120 seconds.

[0024] Furthermore, the purging in step 2) involves introducing a high flow rate of N2 into the ID gas path for purging, with the flow rate set to 5000–12000 sccm and the duration to be 5–180 seconds.

[0025] Furthermore, the number of rounds in step 2) is 4 to 20.

[0026] Furthermore, the switching in step 3) specifically involves the following steps: immediately stopping the supply of NH3 and HCl, then starting N2 purging to ensure complete purification of the reaction chamber, and then opening the selected zone as the AlCl3 precursor supply zone.

[0027] The beneficial effects of the present invention are as follows:

[0028] 1. Add multi-zone independent control of aluminum source supply to the equipment.

[0029] In traditional HVPE equipment, the aluminum source is typically located in a single reaction chamber. As growth time progresses, oxidation and byproduct deposition easily occur on the surface of the aluminum source, leading to reaction interruption and preventing a continuous supply of the precursor AlCl3. Even if the chamber size is increased to increase the amount of metallic aluminum, the oxidation and byproduct deposition after prolonged reaction will still interrupt growth, failing to fundamentally solve the problem. Therefore, this invention improves the aluminum source region in the equipment by proposing a multi-zone, independently controlled aluminum source supply device.

[0030] 2. Add an HCl gas channel to the isolation (ID) gas path.

[0031] This HCl gas channel works in conjunction with the main growth process to introduce HCl gas during the intervals when NH3 supply is stopped in each small cycle. This allows for in-situ etching and removal of pre-reaction products deposited in the nozzle and reaction chamber wall areas, thereby reducing the risk of nozzle clogging. Simultaneously, this HCl gas channel also enables mild etching of the growth surface, dynamically releasing film stress and reducing crack formation. It is used to address nozzle clogging issues caused by pre-reaction product accumulation.

[0032] III. Periodic Control Strategy

[0033] To address the issues of nozzle clogging and sample cracking, this invention introduces a periodic control strategy for independently controlling the aluminum source and HCl gas channel in multiple zones, forming a nested collaborative epitaxy method of "outer layer aluminum source rotation + inner layer growth cycle embedded etching".

[0034] Therefore, the multi-zone continuous aluminum source supply and periodic control strategy proposed in this invention can effectively solve the problems of aluminum source degradation, nozzle clogging, and stress accumulation in existing HVPE growth. It enables long-term continuous operation of HVPE equipment for epitaxial AlN; avoids interruptions and replacement operations caused by aluminum source degradation during long-term growth; effectively removes deposits in the nozzle area and maintains flow field stability; dynamically releases stress, reduces crack incidence, and improves film integrity; the entire equipment has high controllability and is suitable for HVPE equipment retrofitting and upgrading. Attached Figure Description

[0035] Figure 1 This is a schematic cross-sectional view of a reaction chamber suitable for independent control of multiple zones, provided by the present invention.

[0036] 1—NH3 gas path;

[0037] 2—ID gas path;

[0038] 3—The aluminum source reaction chamber is divided into different zones, each zone having independent HCl and N2 inlets;

[0039] 4—Aluminum boat, used to hold aluminum source;

[0040] Figure 2 This is a flowchart of the present invention. Detailed Implementation

[0041] The present invention will now be described in detail with reference to the accompanying drawings.

[0042] The following description of the present invention and its embodiments is not restrictive, and actual embodiments are not limited thereto. In short, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the invention, such designs should fall within the protection scope of the present invention.

[0043] Example 1:

[0044] 1. Equipment Configuration

[0045] like Figure 1 As shown, this invention sets up four independent aluminum source zones (A, B, C, and D) in the HVPE equipment. Each zone contains an aluminum boat loaded with 50g of 99.999% pure metallic aluminum and equipped with an independent gas inlet. The flow rates of HCl and N2 gas at each inlet are precisely controlled by mass flow meters, with adjustment ranges of 0-100 sccm and 0-2000 sccm, respectively. The gas outlets are merged into one. The gas inlets can be used to introduce HCl and N2 gas respectively for alternating reactions, and all gas path switching is achieved by an automated control system. An HCl gas channel is added to the ID gas path, with the HCl gas flow rate precisely controlled by a mass flow meter, with an adjustment range of 0-1000 sccm, which can be used for in-situ etching during the growth gap. The main chamber of the reaction system adopts a horizontal quartz reaction chamber, and the substrate support structure is a custom-made graphite tray.

[0046] 2. Complete the preparations before AlN thick film growth, ensuring the HVPE equipment reaches the set initial temperature, pressure, and atmosphere conditions. The main heating system in the HVPE equipment uses high-frequency induction heating in conjunction with a graphite heating element, achieving a heating temperature of up to 1600℃. Before growth begins, high-purity aluminum blocks are placed into aluminum boats in the four aluminum source zones (A to D). After loading, the equipment is sealed, and the vacuum pump system is activated to evacuate the reaction chamber and aluminum source chamber until the system pressure is less than 1×10⁻² Torr, continuing for 2 hours to remove residual moisture. After evacuation, the N₂ gas source is turned on, and dry N₂ gas is introduced to replace and purge the entire equipment. The N₂ flow rate is set to 800 sccm for each aluminum source zone. Simultaneously, the heating system is activated, raising the temperature of the main reaction zone to 1550℃, and the temperature of the other aluminum source zones to 550℃. The induction heating power is set to 12kW, and the heating rate is controlled by a program. Once the temperature stabilizes, the equipment pressure is maintained at 20 Torr, and epitaxial growth can begin.

[0047] 3. Select a partition as the AlCl3 precursor supply area, and periodically execute the "growth → etching → purging" process cycle for several rounds, referring to... Figure 2 Specifically, it includes the following steps:

[0048] 1) First, activate the aluminum source in zone A by introducing 50 sccm of HCl gas to react with the aluminum to generate the AlCl3 precursor and 750 sccm of N2. Simultaneously, maintain an N2 flow of 800 sccm in other zones (B, C, and D) to prevent back diffusion.

[0049] 2) Simultaneously activate the NH3 gas path, introducing NH3 gas at a flow rate of 5000 sccm. This NH3 reacts with AlCl3 in the high-temperature zone to generate AlN, achieving epitaxial deposition. Each growth cycle lasts 20 minutes, with the equipment pressure maintained at 20 Torr throughout the process, and temperature fluctuations controlled within ±5℃.

[0050] 3) After the growth cycle is complete, the etching stage begins. First, the NH3 gas supply is shut off, and HCl gas at 50 sccm is introduced through the ID gas path. The etching time is set to 10 seconds, primarily targeting the nozzle area, sample surface, and the deposition area at the front of the reaction chamber. This is used to remove pre-reaction byproducts of AlCl3 and NH3 and mitigate stress accumulation. This embodiment uses a shorter etching time and a moderate HCl flow rate, suitable for epitaxial growth processes with high cycle frequency and moderate deposition rates. It focuses on solving deposition clogging in the nozzle area and initial surface stress release issues. Its advantages lie in maintaining rhythm stability and thermal field equilibrium, making it suitable for periodic cleaning strategies in medium-thickness film rapid deposition scenarios.

[0051] 4) After etching is complete, immediately switch to high-flow-rate N2 purging, setting the flow rate to 8000 sccm for 20 seconds. This step thoroughly removes residual etching gas and reaction products from the reaction chamber.

[0052] 5) Periodically execute steps 2), 3) and 4) "growth → etching → purging" process cycles, with the number of continuous process cycles ranging from 4 to 20.

[0053] 4. AlN thick film growth is achieved by manually or automatically switching between alternating gas introduction into each partition; that is, when the aluminum source in a partition is detected to be essentially exhausted, the system automatically switches to another partition.

[0054] Perform the zone switching operation manually or automatically: Immediately stop the NH3 supply and HCl gas flow to zone A, switch to N2 gas at 6000 sccm for system purging for 30 seconds. Then activate the HCl supply to zone B (50 sccm) and coordinate with N2 (750 sccm) to ensure a stable total gas flow; restore the NH3 (5000 sccm) gas flow and continue the standard periodic process cycle.

[0055] 5. The same applies to zones C and D, until all aluminum sources are consumed without needing to replace the aluminum source or interrupt the process.

[0056] Example 2:

[0057] 1. Equipment Configuration

[0058] This embodiment sets up six independent aluminum source zones (A, B, C, D, E, F) in the HVPE equipment. Each zone contains an aluminum boat loaded with 40g of 99.999% pure metallic aluminum and equipped with an independent gas inlet. The flow rates of HCl and N2 gas at each inlet are precisely controlled by mass flow meters, with adjustment ranges of 0–100 sccm and 0–2000 sccm, respectively. All gas outlets merge into a unified exhaust channel. The gas inlets can be vented with HCl and N2 gas respectively to achieve alternating reactions, and all gas path switching is achieved by an automated control system. An HCl gas channel is added to the ID gas path, with the HCl gas flow rate precisely controlled by a mass flow meter, with an adjustment range of 0–1000 sccm, to achieve the etching function of the growth gap. The main chamber of the reaction system adopts a horizontal quartz reaction chamber, and the substrate support structure is a custom graphite tray. The main heating system uses high-frequency induction heating in conjunction with a graphite heating element, and the heating temperature can reach 1600℃.

[0059] 2. Complete the preparations for AlN thick film growth, ensuring the HVPE equipment reaches the set initial temperature, pressure, and atmosphere conditions. Before growth begins, place high-purity aluminum blocks into the aluminum boats of the six aluminum source zones (A to F). Close the HCl channels in all zones and open the N2 carrier gas in all zones, setting the N2 flow rate for each zone to 800 sccm. Subsequently, synchronously raise the temperatures of the aluminum source zones and reaction zones. Set the aluminum source zone temperature to 530℃ and the reaction zone temperature to 1530℃. After the system pressure stabilizes at 20 Torr, the formal growth process begins.

[0060] 3. Select a partition as the AlCl3 precursor supply area, and periodically execute the "growth → etching → purging" process cycle for several rounds, referring to... Figure 2 Specifically, it includes the following steps:

[0061] 1) First, activate the aluminum source in zone A by introducing 40 sccm of HCl gas to react with the aluminum and generate the AlCl3 precursor, while simultaneously introducing 760 sccm of N2 gas as a carrier. Maintain an N2 gas flow of 800 sccm in the remaining zones (B, C, D, E, F) to prevent back diffusion.

[0062] 2) Simultaneously turn on the NH3 gas path, set the flow rate to 4500 sccm, and begin AlN epitaxial growth. This growth phase lasts for 20 minutes.

[0063] 3) After the growth cycle is completed, the etching stage begins. First, the NH3 gas supply is shut off, and HCl gas at 300 sccm is introduced through the ID gas path. The etching time is set to 60 seconds, primarily targeting the nozzle area, sample surface, and the deposition area at the front of the reaction chamber. This further removes byproducts accumulated during the long deposition process and provides a stronger stress release treatment to the film surface. Compared to Example 1, this example significantly improves etching intensity (higher HCl flow rate + longer etching time), making it more suitable for the dual requirements of residual deposits and internal stress release capabilities in high-thickness, long-duration epitaxial growth tasks, further ensuring film integrity and the stability of long-term equipment operation.

[0064] 4) After etching is complete, immediately switch to high-flow N2 purging, with a flow rate of 10,000 sccm and a duration of 20 seconds, to thoroughly remove residual etching gas and reaction products from the reaction chamber and provide a clean environment for the next growth cycle.

[0065] 5) Periodically execute steps 2), 3) and 4) "growth → etching → purging" process cycles, with the number of continuous process cycles ranging from 4 to 20.

[0066] 4. AlN thick film growth is achieved by manually or automatically switching between alternating gas introduction into each zone; that is, when the planned growth time for a zone is detected, the system automatically switches to another zone.

[0067] When the planned growth time for partition A reaches 2 hours, perform a partition switch manually or automatically: First, immediately stop the supply of NH3 and HCl to partition A. Then, purge with N2 at 6000 sccm for 30 seconds to ensure complete purification of the reaction chamber. After purging, start the HCl supply to partition B at 40 sccm, while adjusting the N2 flow rate in partition B to ensure consistent total flow rate across all partitions. Reintroduce NH3 and begin the standard growth-etching-purging cycle.

[0068] 5. Switch sequentially to zones C, D, E, and F to complete the full multi-cavity rotation. With a planned growth time of 2 hours per zone, a total of 12 hours of continuous operation can be achieved without changing the aluminum source or interrupting the process.

[0069] The etching strategies employed in the two embodiments are adapted to different growth conditions. Embodiment 1 is suitable for medium-thickness, high-frequency, low-stress deposition processes, emphasizing gas field stability and rapid cycle response. Embodiment 2, on the other hand, is designed for longer-duration and higher-thickness AlN epitaxial processes, maintaining interface cleanliness and structural integrity by enhancing etching intensity. This demonstrates the high adaptability and adjustability of the process of the present invention under different epitaxial tasks.

[0070] In summary, this embodiment demonstrates the adaptability and feasibility of the present invention in actual HVPE equipment, and can effectively alleviate problems such as aluminum source deterioration, nozzle clogging and stress accumulation in traditional growth processes, thus possessing good industrial application potential.

Claims

1. A method for growing aluminum nitride thick films using hydride vapor phase epitaxy, characterized in that, In the HVPE equipment, the aluminum source reaction chamber is divided into multiple mutually enclosed individual chambers as zones. Each zone contains an aluminum boat and is equipped with independent HCl and N2 gas inlets. The HVPE equipment has an NH3 gas path and an ID gas path. An HCl gas channel is added to the ID gas path, and the HCl gas channel is equipped with a gas flow control component. This is used to perform in-situ etching and removal of the pre-reaction products deposited in the nozzle and reaction chamber wall areas. By manually or automatically switching and alternately introducing reaction gases into each zone, a long-term stable supply of AlCl3 is achieved. Combined with the periodic etching control of HCl, the growth of AlN thick films is realized. The specific process includes the following steps: 1) Complete the preparations before AlN thick film growth, and bring the HVPE equipment to the set initial temperature, pressure and atmosphere conditions; 2) Select a partition as the AlCl3 precursor supply area and periodically execute the "growth → etching → purging" process cycle for several rounds; 3) When it is detected that the aluminum source of the partition is basically exhausted or the planned growth time of the partition is reached, switch to another partition and repeat step 2). 4) Repeat steps 2)-3) until all partitions have finished growing.

2. The method for growing aluminum nitride thick films by hydride vapor phase epitaxy as described in claim 1, characterized in that, The number of partitions is 2 to 8.

3. The method for growing aluminum nitride thick films by hydride vapor phase epitaxy as described in claim 1, characterized in that, The HCl gas flow rate in the HCl gas channel ranges from 0 to 1000 sccm.

4. The method for growing thick aluminum nitride films by hydride vapor phase epitaxy as described in claim 1, characterized in that, The preparation steps before AlN thick film growth in step 1) include: 1-1) Load high-purity metallic aluminum into the aluminum boats of each zone, and load the substrate to be grown into the designated area of ​​the reaction chamber; 1-2) Evacuate the equipment to achieve the set vacuum level; 1-3) Introduce dry inert gas for gas replacement and purging to improve the purity of the equipment; 1-4) Start the heating system, heat the reaction zone and non-reaction zone to the set temperature respectively, and set the heating rate and heating power; 1-5) Once the temperature and pressure have stabilized within the preset range, the initialization preparation is complete, and the system enters the standby state before epitaxial growth.

5. The method for growing aluminum nitride thick films by hydride vapor phase epitaxy as described in claim 1, characterized in that, The specific steps of growth in step 2) include: 2-1) In this zone, 10–200 sccm of HCl gas is introduced to react with aluminum to generate AlCl3 precursor, and 100–3000 sccm of N2 is introduced as carrier gas. At the same time, other zones maintain N2 gas supply, with a flow rate equal to the sum of the HCl and N2 flow rates in the AlCl3 precursor supply zone. 2-2) Simultaneously open the ID gas path and introduce N2 at a flow rate of 50-2000 sccm as an isolation gas to reduce pre-reaction; 2-3) Simultaneously turn on the NH3 gas path and introduce NH3 gas at a flow rate of 500–8000 sccm. The NH3 gas reacts with AlCl3 in the high-temperature zone to generate AlN, thereby achieving epitaxial deposition. The growth time is 5–30 minutes.

6. The method for growing aluminum nitride thick films by hydride vapor phase epitaxy as described in claim 1, characterized in that, The specific etching steps in step 2) are as follows: shut off the HCl gas supply to the aluminum source zone, shut off the NH3 gas supply to the NH3 gas path, open the HCl gas channel in the ID gas path, introduce 5–100 sccm of HCl gas, apply it to the nozzle area and the sample surface, and set the etching time to 1–120 seconds.

7. The method for growing aluminum nitride thick films by hydride vapor phase epitaxy as described in claim 1, characterized in that, The purging in step 2) involves introducing a high flow rate of N2 into the ID gas path for purging. The flow rate is set to 5000–12000 sccm, and the duration is 5–180 seconds.

8. The method for growing aluminum nitride thick films by hydride vapor phase epitaxy as described in claim 1, characterized in that, The number of rounds in step 2) is 4 to 20.

9. The method for growing aluminum nitride thick films by hydride vapor phase epitaxy as described in claim 1, characterized in that, The switching described in step 3) involves the following steps: immediately stop the supply of NH3 and HCl, then start N2 purging to ensure that the reaction chamber is completely purified, and then open the selected zone as the AlCl3 precursor supply zone.

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