CN115763251A - GaN heteroepitaxial structure based on Si substrate and preparation method - Google Patents

GaN heteroepitaxial structure based on Si substrate and preparation method Download PDF

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CN115763251A
CN115763251A CN202211448706.5A CN202211448706A CN115763251A CN 115763251 A CN115763251 A CN 115763251A CN 202211448706 A CN202211448706 A CN 202211448706A CN 115763251 A CN115763251 A CN 115763251A
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layer
gan
aln
buffer layer
superlattice
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李兵兵
商延卫
马旺
张义
王建立
程静云
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Juneng Jingyuan Qingdao Semiconductor Materials Co ltd
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Juneng Jingyuan Qingdao Semiconductor Materials Co ltd
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Abstract

The invention provides a GaN hetero-epitaxial structure based on a Si substrate and a preparation method thereof, and the GaN-on-Si epitaxial structure with large size, no crack, low dislocation density, controllable warping and high performance can be prepared by introducing an AlN/GaN superlattice buffer layer and optimizing the preparation process.

Description

GaN heteroepitaxial structure based on Si substrate and preparation method
Technical Field
The invention belongs to the technical field of semiconductors, and relates to a GaN heteroepitaxial structure based on a Si substrate and a preparation method thereof.
Background
Compared with materials such as first-generation semiconductor silicon (Si) and second-generation semiconductor gallium arsenide (GaAs), the third-generation semiconductor material represented by gallium nitride (GaN) has larger forbidden bandwidth (> 3 eV), so that the third-generation semiconductor material is obviously superior to traditional semiconductor materials such as Si and GaAs in the aspects of breakdown electric field, intrinsic carrier concentration and radiation resistance. In addition, the GaN material is more excellent in carrier mobility, saturated carrier concentration and the like, so that the GaN material is particularly suitable for manufacturing power and microwave electronic devices with high power density, high response rate and high efficiency, and has wide application prospects in the fields of 5G communication, radars, cloud computing, fast charging sources and the like.
The AlGaN/GaN HEMT based on Si substrate growth at present develops rapidly with the advantages of low cost, easy integration and the like, but because the Si substrate and the GaN have the problems of lattice adaptation up to 17% and thermal mismatch up to 118%, the GaN-on-Si epitaxial technology faces a plurality of technical difficulties such as melt etching (melt back etching), cracking of GaN epitaxial layers, dense defects, warpage control and the like, and greatly hinders the development of the GaN-on-Si HEMT, so the current market still takes 6-inch epitaxial wafers as the key point for research and development, and the 8-inch GaN-on-Si epitaxy still has a plurality of problems.
Therefore, it is desirable to provide a GaN heteroepitaxial structure based on a Si substrate and a method for fabricating the same.
Disclosure of Invention
In view of the above-mentioned drawbacks of the prior art, an object of the present invention is to provide a Si substrate-based GaN hetero-epitaxial structure and a fabrication method thereof, which solve the problem of difficulty in fabricating a high-performance GaN hetero-epitaxial structure based on a Si substrate in the prior art.
In order to achieve the above objects and other related objects, the present invention provides a method for fabricating a GaN heteroepitaxial structure based on a Si substrate, comprising the steps of:
providing a Si substrate;
providing an Al source and NH3, and forming an AlN nucleating layer on the Si substrate;
providing a Ga source, and forming an AlGaN first buffer layer on the AlN nucleating layer;
closing an Al source, forming a GaN layer on the AlGaN first buffer layer, closing a Ga source, opening the Al source, forming an AlN layer on the GaN layer, repeatedly and alternately preparing the GaN layer and the AlN layer to form an AlN/GaN superlattice second buffer layer, wherein the GaN layer is contacted with the AlGaN first buffer layer;
and opening a Ga source, and forming a GaN epitaxial layer on the AlN/GaN superlattice second buffer layer, wherein the GaN epitaxial layer is in contact with the GaN layer.
Optionally, the step of forming the GaN epitaxial layer includes:
opening a Ga source, providing C2H2, and forming a cGaN layer on the AlN/GaN superlattice second buffer layer;
closing a C2H2 source, and forming a uGaN layer on the cGaN layer;
opening a Ga source, forming a GaN channel layer on the uGaN layer, wherein the growth temperature of the cGaN layer is lower than that of the uGaN layer, and growing NH of the cGaN layer 3 The flow rate is less than NH of the uGaN layer 3 And the thickness of the cGaN layer is larger than that of the uGaN layer.
Optionally, the AlN nucleation layer includes a low-temperature AlN nucleation layer and a high-temperature AlN nucleation layer, where a growth temperature of the low-temperature AlN nucleation layer is 600 to 1020 ℃, and a growth temperature of the high-temperature AlN nucleation layer is 900 to 1300 ℃; the AlN nucleating layer is 100-250 nm thick.
Optionally, the growth temperature for forming the AlGaN first buffer layer is 900-1120 ℃, and the NH3 flow is 1000-2000 sccm; the Al component in the formed AlGaN first buffer layer is 40-80%; the thickness of the AlGaN first buffer layer is 100-500 nm.
Optionally, when the AlN/GaN superlattice second buffer layer is prepared, the growth pressure of the AlN layer is 40-150 mbar, the growth temperature is 900-1300 ℃, and NH is generated 3 The flow rate is 1000-30000 sccm, the growth pressure of the GaN layer is 50-200 mbar, the growth temperature is 900-1150 ℃, and NH is added 3 The flow rate of (2) is 1000 to 25000sccm.
Optionally, in the AlN/GaN superlattice second buffer layer, a single layer of the AlN layer has a thickness of 1 to 5nm, and a single layer of the GaN layer has a thickness of 25 to 40nm.
Optionally, the second buffer layer of AlN/GaN superlattice is prepared after growing a single layerAfter the AlN layer, only NH is opened in the reaction chamber 3 After the GaN layer is stabilized, the growth of the GaN layer is started again, and only NH is opened after the growth of the single-layer GaN layer is finished 3 After stabilization, regrowing the AlN layer; the AlN layer and the GaN layer have the same growth conditions including temperature, pressure and NH 3 The amount of (c).
Optionally, a step of forming an AlN/GaN superlattice third buffer layer on the AlN/GaN superlattice second buffer layer; the thickness of the AlN/GaN superlattice second buffer layer and the AlN/GaN superlattice third buffer layer is 150-400 nm; the thickness of the single GaN layer in the AlN/GaN superlattice second buffer layer is t1, the thickness of the single AlN layer is t2, the thickness of the single GaN layer in the AlN/GaN superlattice third buffer layer is t3, the thickness of the single AlN layer is t4, t1 is the same as t3, and t2 is 1.5-2.5 times of t 4.
The present invention also provides a GaN heteroepitaxial structure based on a Si substrate, the heteroepitaxial structure comprising:
a Si substrate;
an AlN nucleation layer located on the Si substrate;
an AlGaN first buffer layer on the AlN nucleation layer;
the AlN/GaN superlattice second buffer layer is positioned on the AlGaN first buffer layer and comprises GaN layers and AlN which are repeatedly and alternately arranged, and the GaN layers are contacted with the AlGaN first buffer layer;
a GaN epitaxial layer on the AlN/GaN superlattice second buffer layer, the GaN epitaxial layer being in contact with the GaN layer.
Optionally, an AlN/GaN superlattice third buffer layer is further included on the AlN/GaN superlattice second buffer layer; the thicknesses of the AlN/GaN superlattice second buffer layer and the AlN/GaN superlattice third buffer layer are respectively more than 150 nm; the thickness of the single GaN layer in the AlN/GaN superlattice second buffer layer is t1, the thickness of the single AlN layer is t2, the thickness of the single GaN layer in the AlN/GaN superlattice third buffer layer is t3, the thickness of the single AlN layer is t4, t1 is the same as t3, and t2 is 1.5-2.5 times of t 4.
As described above, the GaN-on-Si epitaxial structure based on the Si substrate and the preparation method thereof can prepare the GaN-on-Si epitaxial structure with large size, no Crack (Crack-free), low dislocation density, controllable warping and high performance by introducing the AlN/GaN superlattice buffer layer and optimizing the preparation process.
Drawings
Fig. 1 shows a schematic structural view of a GaN heteroepitaxial structure based on a Si substrate prepared in a first embodiment of the present invention.
Fig. 2 is an enlarged view of the second buffer layer of the AlN/GaN superlattice as shown in fig. 1.
FIG. 3 shows two different NH groups in one embodiment of the present invention 3 And (3) comparing the warpage in-situ monitoring curve of the AlN/GaN superlattice second buffer layer under flow regulation.
Fig. 4 is a schematic structural view showing a GaN heteroepitaxial structure based on a Si substrate prepared in the second embodiment of the present invention.
Fig. 5 is an enlarged view of the second buffer layer of the AlN/GaN superlattice as shown in fig. 4.
Fig. 6 is an enlarged schematic view of the third buffer layer of the AlN/GaN superlattice as shown in fig. 4.
Fig. 7 is a graph comparing two warpage in-situ monitoring curves obtained by adjusting the thickness of a single layer in the second buffer layer and the third buffer layer of the AlN/GaN superlattice in accordance with the second embodiment of the present invention.
FIG. 8 is an Atomic Force Microscope (AFM) view of the surface of a GaN epitaxial layer according to a second embodiment of the invention.
FIG. 9 is an optical microscope photograph showing the surface of the GaN epitaxial layer in the second embodiment of the invention.
Description of the element reference numerals
110 Si substrate
210 AlN nucleation layer
310 AlGaN first buffer layer
410 Second buffer layer of AlN/GaN superlattice
411 GaN layer
412 AlN layer
510. Composite GaN
610 GaN channel layer
710 AlGaN barrier layer
120 Si substrate
220 AlN nucleation layer
320 AlGaN first buffer layer
420 Second buffer layer of AlN/GaN superlattice
421 GaN layer
422 AlN layer
520 AlN/GaN superlattice third buffer layer
521 GaN layer
522 AlN layer
620 GaN epitaxial layer
Detailed Description
The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.
As in the detailed description of the embodiments of the present invention, the cross-sectional views illustrating the device structure are not partially enlarged in general scale for convenience of illustration, and the schematic views are only examples, which should not limit the scope of the present invention. In addition, the three-dimensional dimensions of length, width and depth should be included in the actual fabrication.
For convenience in description, spatial relational terms such as "below," "beneath," "below," "under," "over," "upper," and the like may be used herein to describe one element or feature's relationship to another element or feature as illustrated in the figures. It will be understood that these terms of spatial relationship are intended to encompass other orientations of the device in use or operation in addition to the orientation depicted in the figures. Further, when a layer is referred to as being "between" two layers, it can be the only layer between the two layers, or one or more intervening layers may also be present. Where an element is referred to as being "secured to" or "disposed on" another element, it can be directly on the other element or be indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or be indirectly connected to the other element.
Expressions such as "between 8230%" \8230, between "may be used herein, both inclusive, and expressions such as" plurality "may be used herein, both inclusive, and expressions such as two or more, unless explicitly specified otherwise. Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature.
It should be noted that the drawings provided in the present embodiment are only for illustrating the basic idea of the present invention, and the drawings only show the components related to the present invention rather than being drawn according to the number, shape and size of the components in actual implementation, and the type, quantity and proportion of each component in actual implementation may be changed freely, and the layout of the components may be more complicated.
Example one
The embodiment provides a preparation method of a GaN hetero-epitaxial structure based on a Si substrate, wherein a GaN-on-Si epitaxial structure with large size, no Crack (Crack-free), low dislocation density, controllable warpage and high performance can be prepared by introducing an AlN/GaN superlattice buffer layer and optimizing the preparation process.
Specifically, with reference to fig. 1 and 2, the preparation of the heteroepitaxial structure may include the following steps:
s1: a Si substrate 110 is provided.
Specifically, the size of the Si substrate 110 may include, for example, 6 inches, 8 inches, or 12 inches, and the thickness and size of the Si substrate 110 may be selected according to specific needs. Wherein the Si substrate 110 may include an intrinsic silicon substrate or a silicon-on-insulator substrate, which is not limited herein.
In order to further provide the bonding property of the subsequently grown material layer and the Si substrate 110, the surface of the Si substrate 110 is preferably subjected to a high temperature hydrogen treatment, and the specific treatment process is not limited herein.
S2: providing Al source and NH 3 An AlN nucleation layer 210 is formed on the Si substrate 110.
Specifically, the TMAl source may be opened in the reaction chamber to pre-coat a layer of Al on the surface of the Si substrate 110, and then the temperature and pressure in the reaction chamber are adjusted to open NH 3 To grow the AlN nucleation layer 210. The AlN nucleation layer 210 is preferably composed of a low-temperature AlN layer and a high-temperature AlN layer, the growth temperature of the low-temperature AlN nucleation layer may be 600-1020 ℃, such as 600 ℃, 800 ℃, 1000 ℃, 1020 ℃ and the like, and the growth temperature of the high-temperature AlN nucleation layer may be 900-1300 ℃, such as 900 ℃, 1000 ℃, 1200 ℃, 1300 ℃ and the like; and the AlN nucleation layer 210 is preferably formed to a thickness of 100 to 250nm, such as 100nm, 150nm, 200nm, 250nm, etc.
S3: a Ga source is provided and an AlGaN first buffer layer 310 is formed on the AlN nucleation layer 210.
Specifically, the growth temperature and pressure are adjusted, the TMGa source is turned on, the AlGaN first buffer layer 310 is grown, the AlGaN first buffer layer 310 mainly functions as lattice transition and warpage control, wherein the preferred Al component is 40 to 80%, such as 40%, 60%, 80%, etc., the growth temperature is 900 to 1120 ℃, such as 900 ℃, 1000 ℃, 1120 ℃, etc., and NH 3 The flow rate is 1000-2000 sccm, such as 1000sccm, 1500sccm, 2000sccm, etc. Among them, the AlGaN first buffer layer 310 is preferably formed to have a thickness of 100 to 500nm, such as 100nm, 200nm, 300nm, 500nm, or the like.
S4: turning off an Al source, forming a GaN layer 411 on the AlGaN first buffer layer 310, turning off a Ga source, turning on the Al source, forming an AlN layer 412 on the GaN layer 411, repeatedly and alternately preparing the GaN layer 411 and the AlN layer 412 to form an AlN/GaN superlattice second buffer layer 410, and the GaN layer 411 being in contact with the AlGaN first buffer layer 310.
Specifically, the TMAl source is first turned off, the GaN layer 411 is grown, the TMGa source is then turned off, the TMAl source is turned on, the AlN layer 412 is grown, and the above steps are repeated for several cycles, so as to obtain the AlN/GaN superlattice second buffer layer 410, wherein when the AlN/GaN superlattice second buffer layer 410 is prepared, the growth pressure of the AlN layer 412 may be 40 to 150mbar, such as 40mbar, 80mbar, 100mbar, 120mbar, 150mbar, etc., the growth temperature may be 900 to 1300 ℃, such as 900 ℃, 1000 ℃, 1300 ℃, etc., NH, and the growth pressure may be 40 to 150mbar, such as 40mbar, 80mbar, 100mbar, 120mbar, 150mbar, etc., and the growth temperature may be 900 to 1300 ℃, or the like 3 The flow rate can be 1000-30000 sccm, such as 1000sccm, 5000sccm, 10000sccm, 20000sccm, 30000sccm, etc., the growth pressure of the GaN layer 411 can be 50-200 mbar, such as 50mbar, 80mbar, 100mbar, 150mbar, 200mbar, etc., the growth temperature can be 900-1150 ℃, such as 900 ℃, 1000 ℃, 1150 ℃, etc., NH 3 The flow rate can be 1000-25000 sccm, such as 1000sccm, 5000sccm, 10000sccm, 20000sccm, 25000sccm, etc.
In the AlN/GaN superlattice second buffer layer 410, the AlN layer 412 may have a thickness of 1 to 5nm, such as 1nm, 2nm, 4nm, 5nm, etc., and the GaN layer 411 may have a thickness of 25 to 40nm, such as 25nm, 300nm, 40nm, etc.
Wherein, when the AlN/GaN superlattice second buffer layer 410 is prepared, only NH is opened in the reaction chamber after the AlN layer 412 of a single layer is grown 3 After stabilization, for example, stabilizing for 20-80 s, the growth of the GaN layer 411 is started, and only NH is turned on after the growth of the single-layer GaN layer 411 is completed 3 After stabilization, the AlN layer 412 is regrown, e.g., for the same time as stabilization.
Wherein the growth conditions of the AlN layer 412 and the GaN layer 411 may be the same, and the growth conditions include temperature, pressure and NH 3 The amount of (c).
S5: a Ga source is turned on to form a GaN epitaxial layer on the AlN/GaN superlattice second buffer layer 410, and the GaN epitaxial layer is in contact with the GaN layer 411.
Specifically, in this embodiment, the forming the GaN epitaxial layer includes:
adjusting growth temperature and pressure, turning on TMGa source, and providing C 2 H 2 Forming a cGaN layer (carbon-doped GaN layer) on the AlN/GaN superlattice second buffer layer 410;
adjusting growth temperature and pressure, and closing C 2 H 2 A source forming a uGaN layer (unintentionally doped GaN layer) on the cGaN layer;
adjusting the growth temperature and pressure, opening a TMGa source, forming a GaN channel layer 610 on the uGaN layer, wherein the growth temperature of the cGaN layer is lower than that of the uGaN layer, and growing NH of the cGaN layer 3 The flow rate is less than NH of the uGaN layer 3 And (c) flowing, wherein the thickness of the cGaN layer is greater than that of the uGaN layer, so as to form a composite GaN layer 510 comprising the cGaN layer and the uGaN layer.
Further, the method also comprises the following steps of S6: the growth temperature and pressure are adjusted and the TMGa source and TMAl source are turned on to grow an AlGaN barrier layer 710 on the GaN channel layer 610.
FIG. 3 illustrates the present embodiment in two different NH types 3 And comparing the warpage in-situ monitoring curve of the AlN/GaN superlattice second buffer layer 410 under the flow regulation. According to the embodiment, through the optimization of the structure and the process, the crack-free epitaxial wafer with good warping can be obtained in the epitaxial structure, and the warping can be controlled to be about 0 according to the requirement after the AlGaN barrier layer 710 is grown, so that the warping after cooling can be small, and no cracks are generated.
As shown in fig. 1 and fig. 2, the present embodiment provides a GaN hetero-epitaxial structure based on a Si substrate, which can be prepared by the above preparation process, but is not limited thereto, and the hetero-epitaxial structure in the present embodiment is prepared by the above preparation process, so that the preparation, material, structure, and the like of the hetero-epitaxial structure can refer to the above preparation method, which is not repeated herein.
Wherein the heteroepitaxial structure comprises:
a Si substrate 110;
an AlN nucleation layer 210, the AlN nucleation layer 210 being located on the Si substrate 110;
an AlGaN first buffer layer 310, the AlGaN first buffer layer 310 being located on the AlN nucleation layer 210;
an AlN/GaN superlattice second buffer layer 410, the AlN/GaN superlattice second buffer layer 410 being on the AlGaN first buffer layer 310, including GaN layers 411 and AlN layers 412 alternately arranged repeatedly, and the GaN layers 411 being in contact with the AlGaN first buffer layer 310;
a GaN epitaxial layer on the AlN/GaN superlattice second buffer layer 410, the GaN epitaxial layer being in contact with the GaN layer 411.
Example two
The present embodiment further provides another method for preparing a GaN hetero-epitaxial structure based on a Si substrate, and the present embodiment is different from the first embodiment mainly in that an AlN/GaN superlattice third buffer layer is further formed above the AlN/GaN superlattice second buffer layer.
Specifically, with reference to fig. 1 and fig. 2, the preparation of the heteroepitaxial structure may include the following steps:
s1: a Si substrate 120 is provided.
Specifically, the size of the Si substrate 120 may include, for example, 6 inches, 8 inches, or 12 inches, and the thickness and size of the Si substrate 120 may be selected according to specific needs. The Si substrate 120 may include an intrinsic silicon substrate or a silicon-on-insulator substrate, which is not limited herein.
In order to further provide the bonding property of the subsequently grown material layer and the Si substrate 120, the surface of the Si substrate 120 is preferably subjected to a high temperature hydrogen treatment, and the specific treatment process is not limited herein.
S2: providing Al source and NH 3 An AlN nucleation layer 220 is formed on the Si substrate 120.
Specifically, the TMAl source may be opened in the reaction chamber to pre-coat a layer of Al on the surface of the Si substrate 120, and then the temperature and pressure in the reaction chamber are adjusted to open NH 3 To grow the AlN nucleation layer 220. The AlN nucleation layer 220 is preferably composed of a low-temperature AlN layer and a high-temperature AlN layerThe growth temperature of (a) may be 600-1020 ℃, such as 600 ℃, 800 ℃, 1000 ℃, 1020 ℃ and the like, and the growth temperature of the high-temperature AlN nucleation layer may be 900-1300 ℃, such as 900 ℃, 1000 ℃, 1200 ℃, 1300 ℃ and the like; and the AlN nucleation layer 210 is preferably formed to have a thickness of 100 to 250nm, such as 100nm, 150nm, 200nm, 250nm, etc.
S3: a Ga source is provided, and an AlGaN first buffer layer 310 is formed on the AlN nucleation layer 210.
Specifically, the growth temperature and pressure are adjusted, the TMGa source is turned on, the AlGaN first buffer layer 310 is grown, and the AlGaN first buffer layer 320 mainly functions as lattice transition and warpage control, wherein the preferred Al component is 60 to 80%, such as 60% or 80%, the growth temperature is 900 to 1120 ℃, such as 900 ℃, 1000 ℃, 1120 ℃, or NH 3 The flow rate is 1000-2000 sccm, such as 1000sccm, 1500sccm, 2000sccm, etc. Among them, the AlGaN first buffer layer 320 is preferably formed to have a thickness of 100 to 500nm, for example, 100nm, 200nm, 300nm, 500nm, or the like.
S4: closing the Al source, forming a GaN layer 421 on the AlGaN first buffer layer 320, closing the Ga source, opening the Al source, forming an AlN layer 422 on the GaN layer 421, repeatedly and alternately preparing the GaN layer 421 and the AlN layer 422 to form an AlN/GaN superlattice second buffer layer 420, and the GaN layer 421 being in contact with the AlGaN first buffer layer 320.
Specifically, the growth temperature and pressure are adjusted, the TMAl source is first turned off to grow the GaN layer 421 with the thickness of t1, the TMGa source is then turned off, the TMAl source is turned on to grow the AlN layer 421 with the thickness of t2, the process is repeated for several cycles to obtain the AlN/GaN superlattice second buffer layer 420, and the TMGa source and the TMAl source are turned off.
Wherein, when the AlN/GaN superlattice second buffer layer 420 is prepared, the growth pressure of the AlN layer 422 may be 40 to 150mbar, such as 40mbar, 80mbar, 100mbar, 120mbar, 150mbar, etc., the growth temperature may be 900 to 1300 ℃, such as 900 ℃, 1000 ℃, 1300 ℃, etc., NH 3 The flow rate can be 1000-30000 sccm, such as 1000sccm, 5000sccm, 10000sccm, 20000sccm, 30000sccm, etc., the growth pressure of the GaN layer 411 can be 50-200 mbar, such as 50mbar, 80mbar, 100mbar, 150mbar, 200mbar, etc.,the growth temperature can be 900-1150 deg.C, such as 900 deg.C, 1000 deg.C, 1150 deg.C, NH 3 The flow rate can be 1000-25000 sccm, such as 1000sccm, 5000sccm, 10000sccm, 20000sccm, 25000sccm, etc.
Wherein, when preparing the AlN/GaN superlattice second buffer layer 420, only NH is opened in the reaction cavity after the AlN layer 422 of the single layer grows 3 After the stabilization, for example, 5 to 80 seconds, the growth of the GaN layer 421 is started, and after the growth of the single GaN layer 421 is completed, only NH is turned on 3 After stabilization, e.g., 10-80 seconds, the AlN layer 422 is regrown.
In the AlN/GaN superlattice second buffer layer 420, the thickness t1 of the single GaN layer 421 is 25 to 40nm, such as 25nm, 300nm, 40nm, etc., and the thickness t2 of the single AlN layer 422 is 2 to 15nm, such as 2nm, 5nm, 10nm, 15nm, etc.
Wherein the growth conditions of the AlN layer 422 and the GaN layer 421 may be the same, and include temperature, pressure, and NH 3 The amount of (c).
S5: the Ga source is turned on, the AlN/GaN superlattice third buffer layer 520 is formed on the AlN/GaN superlattice second buffer layer 420, and the AlN/GaN superlattice third buffer layer 520 is in contact with the GaN layer 421.
Specifically, the growth temperature and pressure are adjusted, the TMAl source is kept closed, the GaN layer 521 with the thickness of t3 is grown, the TMGa source is closed, the TMAl source is opened, the AlN layer 522 with the thickness of t4 is grown, the process is repeated for a plurality of periods, the AlN/GaN superlattice third buffer layer 520 is obtained, and the TMGa and TMAl source are closed.
The thickness of the AlN/GaN superlattice second buffer layer 420 and the AlN/GaN superlattice third buffer layer 520 may be 150nm or more, such as 150nm, 200nm, 300nm, 400nm, and the like. The thickness t3 of the GaN layer 521 single-layered in the AlN/GaN superlattice third buffer layer 520 may be the same as or close to the thickness t1 of the GaN layer 421 in the AlN/GaN superlattice second buffer layer 420, but the thickness t4 of the AlN layer 522 single-layered in the AlN/GaN superlattice third buffer layer 520 is different from the thickness t2 of the AlN layer 422 in the AlN/GaN superlattice second buffer layer 420, and preferably t2 is 1.5 to 2.5 times the thickness t 4.
S6: a Ga source is turned on, a GaN epitaxial layer 620 is formed on the AlN/GaN superlattice third buffer layer 520, and the GaN epitaxial layer 620 is in contact with the GaN layer 521.
Specifically, the growth temperature and pressure are adjusted, the TMGa source is turned on, and the GaN material layer is grown, wherein the layer can be externally doped with carbon or can be only the GaN material layer.
As shown in fig. 4 to fig. 6, the present embodiment further provides a GaN hetero-epitaxial structure based on a Si substrate, and the hetero-epitaxial structure may be prepared by the above preparation process, but not limited thereto, and the hetero-epitaxial structure in the present embodiment is prepared by the above preparation process, so that the preparation, material, structure, and the like of the hetero-epitaxial structure may refer to the above preparation method, which is not repeated herein.
Fig. 7 is a graph comparing two sets of warpage in-situ monitoring curves obtained by adjusting the thickness of the single layer in the AlN/GaN superlattice second buffer layer 420 and the AlN/GaN superlattice third buffer layer 520 in the present embodiment, fig. 8 is a surface atomic force microscope (afm) view of the GaN epitaxial layer 620, and fig. 9 is a surface optical microscope (afm) view of the GaN epitaxial layer 620. The GaN epitaxial layer 620 with ultrahigh thickness, high crystal quality and good warping can be obtained by regulation, and XRD test of the obtained GaN epitaxial layer 620 shows that the (002) and (102) full width at half maximum are 171arcsec and 414arcsec respectively.
As shown in fig. 4 to fig. 6, the present embodiment further provides a GaN hetero-epitaxial structure based on a Si substrate, and the hetero-epitaxial structure may be prepared by the above preparation process, but not limited thereto, and the hetero-epitaxial structure in the present embodiment is prepared by the above preparation process, so that the preparation, material, structure, and the like of the hetero-epitaxial structure may refer to the above preparation method, which is not repeated herein.
Wherein the heteroepitaxial structure comprises:
a Si substrate 120;
an AlN nucleation layer 220, the AlN nucleation layer 220 being located on the Si substrate 120;
an AlGaN first buffer layer 320, the AlGaN first buffer layer 320 being positioned on the AlN nucleation layer 220;
an AlN/GaN superlattice second buffer layer 420, the AlN/GaN superlattice second buffer layer 420 being positioned on the AlGaN first buffer layer 320, including GaN layers 421 and AlN layers 422 alternately arranged repeatedly, and the GaN layers 421 being in contact with the AlGaN first buffer layer 320;
an AlN/GaN superlattice third buffer layer 520, the AlN/GaN superlattice third buffer layer 520 being positioned on the AlN/GaN superlattice second buffer layer 420 and being in contact with the GaN layer 421;
a GaN epitaxial layer 620, the GaN epitaxial layer 620 being on the AlN/GaN superlattice third buffer layer 520, and the GaN epitaxial layer 620 being in contact with the GaN layer 521.
In conclusion, according to the preparation method of the GaN-on-Si epitaxial structure based on the Si substrate, the GaN-on-Si epitaxial structure with large size, no Crack (Crack-free), low dislocation density, controllable warpage and high performance can be prepared by introducing the AlN/GaN superlattice buffer layer and optimizing the preparation process.
The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which may be made by those skilled in the art without departing from the spirit and scope of the present invention as defined in the appended claims.

Claims (10)

1. A preparation method of a GaN heteroepitaxial structure based on a Si substrate is characterized by comprising the following steps:
providing a Si substrate;
providing Al source and NH 3 Forming an AlN nucleating layer on the Si substrate;
providing a Ga source, and forming an AlGaN first buffer layer on the AlN nucleating layer;
closing an Al source, forming a GaN layer on the AlGaN first buffer layer, closing a Ga source, opening the Al source, forming an AlN layer on the GaN layer, repeatedly and alternately preparing the GaN layer and the AlN layer to form an AlN/GaN superlattice second buffer layer, wherein the GaN layer is contacted with the AlGaN first buffer layer;
and opening a Ga source, and forming a GaN epitaxial layer on the AlN/GaN superlattice second buffer layer, wherein the GaN epitaxial layer is in contact with the GaN layer.
2. The method for preparing a GaN heteroepitaxial structure based on a Si substrate according to claim 1, characterized in that: the step of forming the GaN epitaxial layer includes:
opening the Ga source, and providing C 2 H 2 Forming a cGaN layer on the AlN/GaN superlattice second buffer layer;
closing C 2 H 2 A source forming a uGaN layer on the cGaN layer;
opening a Ga source, forming a GaN channel layer on the uGaN layer, wherein the growth temperature of the cGaN layer is lower than that of the uGaN layer, and growing NH of the cGaN layer 3 The flow rate is less than NH of the uGaN layer 3 And the thickness of the cGaN layer is larger than that of the uGaN layer.
3. The method of claim 1, wherein the method comprises the steps of: the AlN nucleating layer comprises a low-temperature AlN nucleating layer and a high-temperature AlN nucleating layer, wherein the growth temperature of the low-temperature AlN nucleating layer is 600-1020 ℃, and the growth temperature of the high-temperature AlN nucleating layer is 900-1300 ℃; the AlN nucleating layer is 100-250 nm thick.
4. The method for preparing a GaN heteroepitaxial structure based on a Si substrate according to claim 1, characterized in that: the growth temperature for forming the AlGaN first buffer layer is 900-1120 ℃, and NH is adopted 3 The flow rate is 1000-2000 sccm; the Al component in the formed AlGaN first buffer layer is 40-80%; the thickness of the AlGaN first buffer layer is 100-500 nm.
5. GaN heterology based on Si substrate according to claim 1The preparation method of the epitaxial structure is characterized by comprising the following steps: when the AlN/GaN superlattice second buffer layer is prepared, the growth pressure of the AlN layer is 40-150 mbar, the growth temperature is 900-1300 ℃, and NH is added 3 The flow rate is 1000-30000 sccm, the growth pressure of the GaN layer is 50-200 mbar, the growth temperature is 900-1150 ℃, and NH is added 3 The flow rate of (A) is 1000 to 25000sccm.
6. The method of claim 1, wherein the method comprises the steps of: in the AlN/GaN superlattice second buffer layer, the thickness of the single AlN layer is 1-5 nm, and the thickness of the single GaN layer is 25-40 nm.
7. The method for preparing a GaN heteroepitaxial structure based on a Si substrate according to claim 1, characterized in that: when preparing the AlN/GaN superlattice second buffer layer, only NH is opened in the reaction cavity after the AlN layer of the single layer grows 3 After the GaN layer is stabilized, the growth of the GaN layer is started, and only NH is opened after the growth of the single-layer GaN layer is finished 3 After stabilization, regrowing the AlN layer; the AlN layer and the GaN layer have the same growth conditions including temperature, pressure and NH 3 The amount of (c).
8. The method of claim 1, wherein the method comprises the steps of: further comprising a step of forming an AlN/GaN superlattice third buffer layer on the AlN/GaN superlattice second buffer layer; the thickness of the AlN/GaN superlattice second buffer layer and the AlN/GaN superlattice third buffer layer is 150-400 nm; the thickness of the single GaN layer in the AlN/GaN superlattice second buffer layer is t1, the thickness of the single AlN layer is t2, the thickness of the single GaN layer in the AlN/GaN superlattice third buffer layer is t3, the thickness of the single AlN layer is t4, t1 is the same as t3, and t2 is 1.5-2.5 times of t 4.
9. A GaN heteroepitaxial structure based on a Si substrate, characterized in that it comprises:
a Si substrate;
an AlN nucleation layer on the Si substrate;
an AlGaN first buffer layer on the AlN nucleation layer;
the AlN/GaN superlattice second buffer layer is positioned on the AlGaN first buffer layer and comprises GaN layers and AlN which are repeatedly and alternately arranged, and the GaN layers are contacted with the AlGaN first buffer layer;
a GaN epitaxial layer on the AlN/GaN superlattice second buffer layer, the GaN epitaxial layer being in contact with the GaN layer.
10. The heteroepitaxial structure of claim 9, wherein: the AlN/GaN superlattice second buffer layer is also provided with an AlN/GaN superlattice third buffer layer; the thicknesses of the AlN/GaN superlattice second buffer layer and the AlN/GaN superlattice third buffer layer are respectively more than 150 nm; the thickness of the single GaN layer in the AlN/GaN superlattice second buffer layer is t1, the thickness of the single AlN layer is t2, the thickness of the single GaN layer in the AlN/GaN superlattice third buffer layer is t3, the thickness of the single AlN layer is t4, t1 is the same as t3, and t2 is 1.5-2.5 times of t 4.
CN202211448706.5A 2022-11-18 2022-11-18 GaN heteroepitaxial structure based on Si substrate and preparation method Pending CN115763251A (en)

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