Ammonia thermal method gallium nitride crystal growing furnace based on diversion enhancement

Abstract

The invention relates to an ammonothermal method gallium nitride crystal growing furnace based on diversion enhancement, which comprises a high-pressure kettle shell, a heating system, a crystal growing area arranged at the upper part of the high-pressure kettle shell and a raw material dissolving area arranged at the lower part of the high-pressure kettle shell, seed crystals are arranged in the crystal growing area, and a gallium nitride raw material is arranged in the raw material dissolving area; the crystal growing area and the raw material dissolving area are separated by a baffle plate of which the top is of a smooth transition structure; the circumferential side wall of the baffle is in sealed connection with the inner wall of the autoclave shell, and a fluid channel is formed between the edge of the smooth transition structure at the top of the baffle and the inner surface of a top cover of the autoclave shell; a guide cylinder is coaxially arranged in the raw material dissolving area below the baffle plate; and a top opening of the guide cylinder is over against the smooth transition structure of the baffle plate. By introducing the combined structure of the guide cylinder and the smooth top baffle, the flow field in the furnace is physically reconstructed. The guide cylinder guides the solution to form ordered axial circulation, the smooth baffle plate greatly reduces the flow energy loss, and the transport efficiency of nutrient substances to a growth interface is obviously enhanced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of crystal growth furnace, in particular to an ammonia thermal method gallium nitride crystal growth furnace based on flow guide enhancement. BACKGROUND

[0002] As the core representative of the third generation semiconductor material, gallium nitride has a wide range of applications in optoelectronics, power electronics and microwave radio frequency fields, and is a key wide bandgap semiconductor material for preparing high-performance optoelectronic and power electronic devices. The ammonia thermal method is concerned because it can grow large-volume and high-quality gallium nitride crystals under relatively mild conditions. However, the ammonia thermal growth process occurs in a high-temperature and high-pressure diamond ampoule or autoclave, and involves complex coupling processes of thermal field, flow field, mass transfer and chemical reaction inside, which is difficult to observe and measure directly through experimental means.

[0003] The existing ammonia thermal method growth furnace design and process optimization seriously depend on the "trial and error method", which adjusts the structure and process parameters through repeated experiments, resulting in long research and development cycle, high cost, and difficulty in achieving precise control and mechanism insight of the crystal growth process. The traditional ammonia thermal furnace model mostly adopts a simple transverse baffle structure, and the simulation results of its flow field and mass transfer characteristics have large deviation from the actual situation, which cannot effectively predict the key behaviors of crystal growth, such as the transport efficiency of nutrients and the supersaturation distribution of the growth interface. Therefore, an ammonia thermal method gallium nitride crystal growth furnace based on flow guide enhancement is needed. SUMMARY

[0004] The purpose of the present application is to provide an ammonia thermal method gallium nitride crystal growth furnace based on flow guide enhancement.

[0005] To achieve the above purpose, the present application is implemented according to the following technical solutions: The present application comprises an autoclave shell, a heating system, a crystal growth zone arranged at the upper part of the autoclave shell and a raw material dissolution zone arranged at the lower part of the autoclave shell, a seed crystal is arranged in the crystal growth zone, and gallium nitride raw material is arranged in the raw material dissolution zone, the crystal growth zone and the raw material dissolution zone are separated by a baffle with a smooth transition structure at the top; the circumferential side wall of the baffle is sealingly connected with the inner wall of the autoclave shell, and a fluid channel is formed between the edge of the smooth transition structure of the top of the baffle and the inner surface of the top cover of the autoclave shell; a flow guide cylinder is coaxially arranged below the baffle in the raw material dissolution zone, and the top opening of the flow guide cylinder is directly opposite to the smooth transition structure of the baffle.

[0006] Further, the smooth transition structure at the top of the baffle is a circular arc surface, which is used to guide the smooth turning of the fluid flowing out of the flow guide cylinder upward into the crystal growth zone.

[0007] Further, the baffle separates the inner cavity of the autoclave into two parts, the upper part of the crystal growth zone containing the seed crystal, and the lower part of the raw material dissolving zone containing the flow guide cylinder and gallium nitride raw material (7).

[0008] Further, the height of the flow guide cylinder is less than the total height of the raw material dissolving zone, and the bottom of the flow guide cylinder has a gap with the inner surface of the bottom of the autoclave shell, forming a fluid backflow channel.

[0009] Further, the heating system includes an upper heater and a lower heater with independent temperature control, the upper heater is arranged corresponding to the crystal growth zone, and the lower heater is arranged corresponding to the raw material dissolving zone, for establishing and maintaining the required temperature gradient between the crystal growth zone and the raw material dissolving zone.

[0010] The beneficial effects of the present application are: The present application is a gallium nitride crystal growth furnace based on flow enhancement, compared with the prior art, the present application has the following technical effects: The present application restructures the flow field in the furnace by introducing the combination structure of the flow guide cylinder and the smooth top baffle. The flow guide cylinder guides the solution to form an ordered axial circulation, and the smooth baffle greatly reduces the flow energy loss, significantly enhancing the transport efficiency of nutrients to the growth interface. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 The growth furnace structure schematic diagram provided for the embodiments of the present application.

[0012] Figure 2 The overall velocity field of the traditional growth furnace (lateral baffle); Figure 3 The overall velocity field of the growth furnace of the present application; Figure 4 The velocity field near the seed crystal surface of the traditional growth furnace (lateral baffle); Figure 5 The velocity field near the seed crystal surface of the growth furnace of the present application.

[0013] Wherein: 1, autoclave shell; 2, upper heater (growth zone); 3, lower heater (dissolving zone); 4, seed crystal; 5, top smooth baffle; 6, flow guide cylinder; 7, gallium nitride raw material. DETAILED DESCRIPTION

[0014] The present application will be further described below and in the specific embodiments, the schematic embodiments and the description of the present application are used to explain the present application, but not as a limitation of the present application.

[0015] As Figure 1As shown, the invention includes a high-pressure kettle shell 1, a heating system, a crystal growth zone arranged at the upper part of the high-pressure kettle shell 1 and a raw material dissolving zone arranged at the lower part of the high-pressure kettle shell 1, a seed crystal 4 is arranged in the crystal growth zone, and a gallium nitride raw material 7 is arranged in the raw material dissolving zone, the crystal growth zone and the raw material dissolving zone are separated by a baffle 5 with a top smooth transition structure; the circumferential sidewall of the baffle 5 is sealingly connected with the inner wall of the high-pressure kettle shell 1, and the edge of the top smooth transition structure of the baffle 5 and the inner surface of the top cover of the high-pressure kettle shell 1 form a fluid passage; a flow guide cylinder 6 is coaxially arranged below the baffle 5 in the raw material dissolving zone, and the top opening of the flow guide cylinder 6 is opposite to the smooth transition structure of the baffle 5.

[0016] The top smooth transition structure of the baffle 5 is a circular arc curved surface, which is used to guide the fluid to smoothly turn into the crystal growth zone after flowing out of the flow guide cylinder 6 upward, the baffle 5 separates the inner cavity of the high-pressure kettle into two parts, the upper part of the crystal growth zone contains the seed crystal 4, and the lower part of the raw material dissolving zone contains the flow guide cylinder 6 and the gallium nitride raw material 7, the height of the flow guide cylinder 6 is less than the total height of the raw material dissolving zone, and a gap is left between the bottom of the flow guide cylinder 6 and the inner surface of the bottom of the high-pressure kettle shell 1 to form a fluid backflow passage, the heating system includes an upper heater 2 and a lower heater 3 with independent temperature control, the upper heater 2 is arranged corresponding to the crystal growth zone, and the lower heater 3 is arranged corresponding to the raw material dissolving zone, which is used to establish and maintain the required temperature gradient between the crystal growth zone and the raw material dissolving zone.

[0017] Gallium nitride crystals were grown by ammonothermal method in the growth furnace (example group, using the Figure 1 structure) of the embodiment of the invention and the conventional horizontal baffle growth furnace (comparative example group, using the Figure 2 structure).

[0018] After the experiment, the flow field was simulated by computational fluid dynamics (CFD) and the grown crystals were tested, and the following key data were obtained: Table 1: Comparison data of flow field stability and mass transfer efficiency As shown in Table 1, the internal flow field of the growth furnace in this embodiment of the invention exhibits extremely high stability. The number of eddies is reduced to zero, and the velocity non-uniformity of the seed crystal surface is significantly reduced from 35.2% to 8.7%, proving that the smooth baffle effectively eliminates flow separation, and the guide tube guides the formation of a uniform and stable axial mainstream. At the same time, the nutrient transport coefficient is increased by approximately 176%, and the flow energy loss is reduced by approximately 73%, indicating that the structure of this invention greatly promotes the transport of solute to the growth interface and significantly reduces the energy required to drive the flow.

[0019] Table 2: Comparison of Crystal Quality Data The optimization of the flow field directly translates into a leap in crystal growth quality. As shown in Table 2, the average crystal growth rate in the embodiment was increased by approximately 45%, and the growth rate fluctuation range was controlled within ±4.5%, far lower than the ±15.0% of the comparative example, demonstrating the stability of the supersaturation at the growth interface. Ultimately, the dislocation density of the grown crystal was reduced by an order of magnitude, and the crystal stress was reduced by approximately 72%. The stable and uniform growth environment provided by this invention can effectively suppress defect generation and obtain high-quality gallium nitride crystals.

[0020] like Figure 2 The image shown is a flow field contour plot of a traditional transverse baffle structure. Figure 3 The diagram shows the overall flow field of the structure of this invention. It can be clearly observed that, guided by the flow guide tube and with the synergistic effect of the smooth baffles, the fluid inside the furnace forms a single, stable, symmetrical, large-scale annular flow field that runs through the entire chamber. The streamlines are smooth and continuous, and the entire flow field exhibits no obvious eddies, backflows, or dead zones, demonstrating a high degree of order and stability. This flow field structure ensures that heat and nutrients can be uniformly and efficiently transported to the entire crystal growth region.

[0021] and Figure 3 In stark contrast, the internal flow field of this structure exhibits oscillations and significant eddies. Impeded by the transverse baffle, the mainstream fluid undergoes severe separation, generating multiple eddies of varying sizes and large-scale dead zones below the baffle, at the bottom of the raw material zone, and in the corners. This unstable flow field leads to heat accumulation and uneven nutrient transport, which is the root cause of fluctuations in supersaturation at the crystal growth interface and the induction of crystal defects.

[0022] like Figure 5 The image shown is a magnified velocity field cloud / vector diagram of the structure of this invention near the seed crystal growth interface. It can be seen that the fluid particles flow through the growth interface in a nearly parallel and uniformly distributed manner. The velocity vectors are consistent in direction and uniform in size, indicating that the supply of nutrients to the crystal surface is steady-state and spatially uniform, providing crucial ideal conditions for obtaining crystals with uniform composition and low dislocation density.

[0023] like Figure 4 The figure shows the local velocity field near the seed crystal growth interface in a traditional growth furnace structure. The results show that the flow field in this region is extremely turbulent. The velocity vectors are randomly oriented and unevenly distributed in magnitude, with obvious low-velocity regions and transverse shear flows. This unstable and non-uniform interfacial flow field causes the crystal growth rate to fluctuate at the microscale, easily introducing stress, forming inclusions, and significantly increasing the density of crystal defects such as dislocations.

[0024] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A gallium nitride crystal growth furnace based on ammothermal method with enhanced current conductivity, comprising a high-pressure autoclave shell (1), a heating system, a crystal growth zone disposed on the upper part of the high-pressure autoclave shell (1), and a raw material dissolution zone disposed on the lower part, wherein a seed crystal (4) is disposed in the crystal growth zone, and gallium nitride raw material (7) is disposed in the raw material dissolution zone, characterized in that: The crystal growth zone and the raw material dissolution zone are separated by a baffle (5) with a smooth transition structure at the top; the circumferential sidewall of the baffle (5) is sealed to the inner wall of the autoclave shell (1), and the edge of its smooth transition structure at the top forms a fluid channel with the inner surface of the top cover of the autoclave shell (1); below the baffle (5), a guide tube (6) is coaxially arranged in the raw material dissolution zone, and the top opening of the guide tube (6) is directly opposite the smooth transition structure of the baffle (5).

2. The growth furnace according to claim 1, characterized in that, The top of the baffle (5) has a smooth transition structure with an arc-shaped surface, which is used to guide the fluid to flow upward from the guide tube (6) and then smoothly turn into the crystal growth area.

3. The growth furnace according to claim 1 or 2, characterized in that, The baffle (5) divides the inner cavity of the autoclave into upper and lower parts. The upper part is the crystal growth zone that accommodates the seed crystal (4), and the lower part is the raw material dissolution zone that accommodates the guide tube (6) and gallium nitride raw material (7).

4. The growth furnace according to claim 1, characterized in that, The height of the guide tube (6) is less than the total height of the raw material dissolution zone, and there is a gap between its bottom and the bottom inner surface of the high pressure vessel shell (1) to form a fluid return channel.

5. The growth furnace according to claim 1, characterized in that, The heating system includes an upper heater (2) and a lower heater (3) with independent temperature control. The upper heater (2) is set in the crystal growth zone and the lower heater (3) is set in the raw material dissolution zone. It is used to establish and maintain the required temperature gradient between the crystal growth zone and the raw material dissolution zone.

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