CN115274818A - HEMT epitaxial wafer and preparation method thereof, HEMT device - Google Patents

Abstract

The present disclosure provides a HEMT epitaxial wafer, a preparation method thereof, and a HEMT device, belonging to the technical field of semiconductor devices. The HEMT epitaxial wafer includes: a Si substrate, a composite transition layer sequentially stacked on the Si substrate, an AlGaN buffer layer, an AlGaN high resistance layer, a GaN channel layer, an AlGaN barrier layer and a GaN cap layer, the The composite transition layer includes a low temperature BP nucleation layer, a high temperature BP nucleation layer and a pre-laid Al layer sequentially stacked on the Si substrate, and the growth temperature of the low temperature BP nucleation layer is lower than the high temperature BP nucleation layer growth temperature.

Description

HEMT epitaxial wafer and its preparation method, HEMT device

technical field

The present disclosure relates to the technical field of semiconductor devices, in particular to a HEMT epitaxial wafer, a preparation method thereof, and a HEMT device.

Background technique

A high electron mobility transistor (High Electron Mobility Transistor, HEMT) is a heterojunction field effect transistor. The HEMT epitaxial wafer is the basis for the preparation of HEMT devices. The HEMT epitaxial wafer includes a silicon (Si) substrate and an aluminum gallium nitride (AlGaN) buffer layer, an AlGaN high-resistance layer, and a gallium nitride (GaN) trench stacked on the Si substrate in sequence. channel layer, AlGaN barrier layer and GaN capping layer.

The performance of HTME devices largely depends on the crystal quality of the epitaxial layer. In order to reduce the lattice mismatch between the Si substrate and GaN in the epitaxial layer, reduce the dislocation density, and improve the crystal quality of the epitaxial layer, low-temperature aluminum nitride (AlN ) nucleation layer and high temperature AlN nucleation layer.

However, since the lattice constants of GaN and AlN are 0.3189nm and 0.3112nm, the band gaps of GaN and AlN are 3.4eV and 6.2eV respectively, the lattice constant of Si (0.5431nm), the band gap (1.12eV) Compared with GaN and AlN, the crystal quality of the epitaxial layer grown on the low-temperature AlN nucleation layer and the high-temperature AlN nucleation layer is not high.

Contents of the invention

Embodiments of the present disclosure provide a HEMT epitaxial wafer, a preparation method thereof, and a HEMT device, which can improve the crystal quality of the HEMT epitaxial wafer. Described technical scheme is as follows:

An embodiment of the present disclosure provides a HEMT epitaxial wafer, and the HEMT epitaxial wafer includes:

a Si substrate, a composite transition layer, an AlGaN buffer layer, an AlGaN high resistance layer, a GaN channel layer, an AlGaN barrier layer, and a GaN capping layer sequentially stacked on the Si substrate,

The composite transition layer includes a low-temperature boron phosphide (BP) nucleation layer, a high-temperature BP nucleation layer, and a pre-coated Al layer sequentially stacked on the Si substrate, and the growth temperature of the low-temperature BP nucleation layer is lower than The growth temperature of the high-temperature BP nucleation layer.

Optionally, the growth temperature of the low-temperature BP nucleation layer ranges from 600°C to 800°C, and the growth temperature of the high-temperature BP nucleation layer ranges from 900°C to 1100°C;

The value range of the thickness of the low-temperature BP nucleation layer is 10nm-40nm, and the value range of the growth temperature of the high-temperature BP nucleation layer is 150nm-250nm;

The growth pressure of the low-temperature BP nucleation layer ranges from 200 mbar to 300 mbar, and the growth pressure of the high-temperature BP nucleation layer ranges from 50 mbar to 100 mbar.

Optionally, the growth temperature of the pre-laid Al layer ranges from 900°C to 1100°C, the growth pressure of the pre-laid Al layer ranges from 40mbar to 70mbar, and the thickness of the pre-laid Al layer The value range of is 1nm～5nm.

Optionally, the HEMT epitaxial wafer further includes: an AlN insertion layer located between the GaN channel layer and the AlGaN barrier layer.

An embodiment of the present disclosure provides a method for preparing a HEMT epitaxial wafer, the preparation method comprising:

providing a Si substrate;

growing a composite transition layer on the Si substrate, the composite transition layer comprising a low-temperature BP nucleation layer, a high-temperature BP nucleation layer and a pre-coated Al layer sequentially stacked on the Si substrate;

An AlGaN buffer layer, an AlGaN high resistance layer, a GaN channel layer, an AlGaN barrier layer and a GaN capping layer are sequentially grown on the composite transition layer.

Optionally, the growing a composite transition layer on the Si substrate includes: preparing the low-temperature BP nucleation layer in the following manner:

Under the condition that the growth temperature ranges from 600° C. to 800° C. and the growth pressure ranges from 200 mbar to 300 mbar, the low-temperature BP nucleation layer whose thickness ranges from 10 nm to 40 nm is grown.

Optionally, the growing a composite transition layer on the Si substrate includes: preparing the high-temperature BP nucleation layer in the following manner:

Under the condition that the growth temperature ranges from 900° C. to 1100° C. and the growth pressure ranges from 50 mbar to 100 mbar, the high-temperature BP nucleation layer whose thickness ranges from 150 nm to 250 nm is grown.

Optionally, the growing a composite transition layer on the Si substrate includes: preparing the pre-coated Al layer in the following manner:

Under the condition that the growth temperature ranges from 900° C. to 1100° C. and the growth pressure ranges from 40 mbar to 70 mbar, the pre-coated Al layer with a thickness ranging from 1 nm to 5 nm is grown.

Optionally, the preparation method also includes:

An AlN insertion layer is grown between the GaN channel layer and the AlGaN barrier layer.

An embodiment of the present disclosure provides a HEMT device, and the HEMT device includes the HEMT epitaxial wafer described in any one of the preceding items.

The beneficial effects brought by the technical solutions provided by the embodiments of the present disclosure include:

By setting the nucleation layer as a double-layer structure composed of a low-temperature BP nucleation layer and a high-temperature BP nucleation layer. Compared with the conventional AlN nucleation layer, the BP nucleation layer has a smaller lattice mismatch degree with the GaN epitaxial layer, which can reduce the dislocation density caused by the lattice mismatch, thereby improving the crystal quality of the epitaxial layer growth . When AlN is used as the nucleation layer, its lattice constant is smaller than that of Si and GaN, and its forbidden band width is larger than that of Si and GaN, while the lattice constant and forbidden band width of BP are between Si and GaN, which can be easily It plays a good buffer transition role between the Si substrate and the GaN epitaxial layer, which is conducive to reducing the lattice mismatch between the Si substrate and the epitaxial layer and improving the crystal quality. In addition, the growth of the pre-laid Al layer after the growth of the high-temperature BP nucleation layer can avoid the contact reaction between _NH3 and BP to grow BN, because there is a large lattice mismatch between BN and GaN, thereby avoiding the dislocation of the GaN epitaxial layer increase in density.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, the drawings that need to be used in the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present disclosure. For those skilled in the art, other drawings can also be obtained based on these drawings without creative effort.

FIG. 1 is a flowchart of a HEMT epitaxial wafer preparation method provided by an embodiment of the present disclosure;

Fig. 2 is a flow chart of a HEMT epitaxial wafer preparation method provided by an embodiment of the present disclosure;

FIG. 3 is a schematic structural diagram of a HEMT epitaxial wafer provided by an embodiment of the present disclosure.

Detailed ways

In order to make the purpose, technical solution and advantages of the present disclosure clearer, the implementation manners of the present disclosure will be further described in detail below in conjunction with the accompanying drawings.

Unless otherwise defined, the technical terms or scientific terms used herein shall have the usual meanings understood by those having ordinary skill in the art to which the present disclosure belongs. "First", "second", "third" and similar words used in the specification and claims of this disclosure do not indicate any order, quantity or importance, but are only used to distinguish different components . Likewise, words like "a" or "one" do not denote a limitation in quantity, but indicate that there is at least one. Words such as "comprises" or "comprising" and similar terms mean that the elements or items listed before "comprising" or "comprising" include the elements or items listed after "comprising" or "comprising" and their equivalents, and do not exclude other component or object. Words such as "connected" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "Down", "Left", "Right", "Top", "Bottom" and so on are only used to indicate the relative positional relationship. When the absolute position of the described object changes, the relative positional relationship may also be Change accordingly.

Figure 1 is a flow chart of a HEMT epitaxial wafer preparation method provided by an embodiment of the present disclosure. Referring to Figure 1, an embodiment of the present disclosure provides a HEMT epitaxial wafer preparation method, and the HEMT epitaxial wafer preparation method includes:

S101: Provide a Si substrate.

Wherein, the Si substrate may adopt a (111) crystal orientation Si substrate.

S102: grow a composite transition layer on a Si substrate. The composite transition layer includes a low-temperature BP nucleation layer, a high-temperature BP nucleation layer, and a pre-coated Al layer stacked on the Si substrate in sequence. The growth temperature of the low-temperature BP nucleation layer is lower than The growth temperature of the high temperature BP nucleation layer.

Exemplarily, the growth temperature of the low-temperature BP nucleation layer ranges from 600°C to 800°C, and the growth temperature of the high-temperature BP nucleation layer ranges from 900°C to 1100°C; for example, the low-temperature BP nucleation layer The growth temperature is 700°C, and the growth temperature of the high-temperature BP nucleation layer is 1000°C.

The thickness of the low-temperature BP nucleation layer ranges from 10nm to 40nm, and the growth temperature of the high-temperature BP nucleation layer ranges from 150nm to 250nm; for example, the thickness of the low-temperature BP nucleation layer is 25nm, and the high-temperature BP nucleation layer The growth temperature is 200nm.

The growth pressure of the low temperature BP nucleation layer ranges from 200mbar to 300mbar, and the growth pressure of the high temperature BP nucleation layer ranges from 50mbar to 100mbar; for example, the growth pressure of the low temperature BP nucleation layer is 250mbar, and the high temperature BP nucleation layer The growth pressure of the nuclear layer was 75 mbar.

Exemplarily, the growth temperature of the pre-laid Al layer ranges from 900°C to 1100°C, the growth pressure of the pre-laid Al layer ranges from 40mbar to 70mbar, and the thickness of the pre-laid Al layer ranges from 1nm ~5nm. For example, the growth temperature of the pre-applied Al layer is 1000° C., the growth pressure of the pre-applied Al layer is 55 mbar, and the thickness of the pre-applied Al layer is 3.5 nm.

S103: growing an AlGaN buffer layer, an AlGaN high resistance layer, a GaN channel layer, an AlGaN barrier layer, and a GaN capping layer sequentially on the composite transition layer.

Exemplarily, the AlGaN buffer layer is an undoped AlGaN layer, the thickness ranges from 2.0 to 3.0 microns, and the Al composition ranges from 0.2 to 0.8, which can ensure the quality of the AlGaN buffer layer.

Exemplarily, the thickness of the AlGaN high-resistance layer ranges from 1.0 to 2.0 microns, which can ensure the growth quality of the AlGaN high-resistance layer itself, and at the same time effectively achieve the goal of high resistance, that is, ensure the high-resistance effect.

Exemplarily, the AlGaN high resistance layer is doped with C, and the doping concentration of the carbon element is 10 ¹⁹ cm ⁻³ to 10 ²⁰ cm ⁻³ . Doping the AlGaN high-resistance layer with carbon can improve the high-resistance effect of the AlGaN high-resistance layer, and the doping concentration of the carbon element within the above range can also ensure the quality of the AlGaN high-resistance layer itself.

Exemplarily, the thickness of the GaN channel layer ranges from 300 to 600 nm, so that the quality of the obtained GaN channel layer is better, and the quality of the finally obtained HEMT epitaxial wafer is improved.

For example, the GaN channel layer has a thickness of 400 nm. The thickness of the GaN channel layer is more appropriate, the cost is more reasonable, and the quality of the HEMT epitaxial wafer can be effectively improved.

Exemplarily, the thickness range of the AlGaN barrier layer is 20-25 nm, which can ensure the quality of the HEMT epitaxial wafer.

Exemplarily, the GaN capping layer can be a P-type GaN layer, which is convenient for preparation and acquisition.

Optionally, the thickness of the GaN capping layer ranges from 3 to 5 nm, and the overall quality of the obtained GaN capping layer is better.

Exemplarily, the impurity in the GaN capping layer is Mg, which is convenient for preparation and acquisition.

By setting the nucleation layer as a double-layer structure composed of a low-temperature BP nucleation layer and a high-temperature BP nucleation layer. Compared with the conventional AlN nucleation layer, the BP nucleation layer has a smaller lattice mismatch degree with the GaN epitaxial layer, which can reduce the dislocation density caused by the lattice mismatch, thereby improving the crystal quality of the epitaxial layer growth . When AlN is used as the nucleation layer, its lattice constant is smaller than that of Si and GaN, and its forbidden band width is larger than that of Si and GaN, while the lattice constant and forbidden band width of BP are between Si and GaN, which can be easily It plays a good buffer transition role between the Si substrate and the GaN epitaxial layer, which is conducive to reducing the lattice mismatch between the Si substrate and the epitaxial layer and improving the crystal quality. In addition, the growth of the pre-laid Al layer after the growth of the high-temperature BP nucleation layer can avoid the contact reaction between _NH3 and BP to grow BN, because there is a large lattice mismatch between BN and GaN, thereby avoiding the dislocation of the GaN epitaxial layer increase in density.

Fig. 2 is a flow chart of another HEMT epitaxial wafer preparation method provided by an embodiment of the present disclosure. Referring to Fig. 2, the HEMT epitaxial wafer preparation method may include:

S201: Provide a Si substrate.

Wherein, the Si substrate may adopt a (111) crystal orientation Si substrate.

Optionally, step S201 includes: placing the Si substrate in a metal-organic chemical vapor deposition (Metal-organic Chemical Vapor Deposition, MOVCD) system, in a hydrogen (H ₂ ) atmosphere, at a temperature of 1000°C to 1200°C 1. Processing the surface of the Si substrate for 5 minutes to 10 minutes under a pressure condition of 50 mbar to 150 mbar. To remove impurities (such as oxides) on the surface of the Si-based Si substrate.

S202: growing a composite transition layer on the Si substrate.

In a possible implementation of the present disclosure, the growth process of the composite transition layer is as follows:

The first step is to grow a low-temperature BP nucleation layer with a thickness ranging from 10nm to 40nm under the condition that the growth temperature ranges from 600°C to 800°C and the growth pressure ranges from 200mbar to 300mbar.

Exemplarily, the first step may include: growing a low-temperature BP nucleation layer at a temperature of 600°C to 800°C and a pressure of 200mbar to 300mbar, and the V/III ratio during growth is in the range of 500 to 800 , the low-temperature BP nucleation layer is a three-dimensional island-like growth pattern.

The second step is to grow a high-temperature BP nucleation layer with a thickness ranging from 150nm to 250nm under the condition that the growth temperature ranges from 900°C to 1100°C and the growth pressure ranges from 50mbar to 100mbar.

Exemplarily, the second step may include: growing a high-temperature BP nucleation layer at a temperature of 900°C to 1100°C and a pressure of 50mbar to 100mbar, and the V/III ratio during growth is in the range of 50 to 80 , the low-temperature BP nucleation layer is a two-dimensional flat growth mode.

Step 3: Under the condition that the growth temperature ranges from 900°C to 1100°C and the growth pressure ranges from 40mbar to 70mbar, grow a pre-laid Al layer with a thickness ranging from 1nm to 5nm .

Exemplarily, the third step may include: at a temperature of 900-1100° C. and a pressure of 40 mbar-70 mbar, feed an Al source with a flow rate of 50-200 sccm into the reaction chamber for 10-20 seconds (s), without NH ₃ , after the Al source is decomposed, a layer of Al film is pre-paved on the surface of the high-temperature BP nucleation layer, that is, a pre-pave Al layer.

Wherein, the Al source may be trimethylaluminum (TMAl).

By setting the nucleation layer as a double-layer structure composed of a low-temperature BP nucleation layer and a high-temperature BP nucleation layer. Compared with the conventional AlN nucleation layer, the BP nucleation layer has a smaller lattice mismatch degree with the GaN epitaxial layer, which can reduce the dislocation density caused by the lattice mismatch, thereby improving the crystal quality of the epitaxial layer growth . When AlN is used as the nucleation layer, its lattice constant is smaller than that of Si and GaN, and its forbidden band width is larger than that of Si and GaN, while the lattice constant and forbidden band width of BP are between Si and GaN, which can be easily It plays a good buffer transition role between the Si substrate and the GaN epitaxial layer, which is conducive to reducing the lattice mismatch between the Si substrate and the epitaxial layer and improving the crystal quality. In addition, the growth of the pre-laid Al layer after the growth of the high-temperature BP nucleation layer can avoid the contact reaction between _NH3 and BP to grow BN, because there is a large lattice mismatch between BN and GaN, thereby avoiding the dislocation of the GaN epitaxial layer increase in density.

However, the growth of the high-temperature BP nucleation layer, the low-temperature BP nucleation layer, and the pre-coated Al layer using the above-mentioned growth conditions and thickness can ensure that the obtained high-temperature BP nucleation layer, low-temperature BP nucleation layer, and pre-coated Al layer meet the above mitigation requirements. Lattice mismatch, improving crystal quality requirements.

S203: growing an AlGaN buffer layer on the composite transition layer.

Optionally, the growth conditions of the AlGaN buffer layer include: the growth temperature is between 1050° C. and 1200° C., the pressure is between 40 and 70 mbar, and NH ₃ and MO sources (trimethylgallium TMGa and trimethylaluminum TMAl) to grow the AlGaN buffer layer. Wherein, the AlGaN buffer layer is an undoped AlGaN layer, the thickness ranges from 2.0 to 3.0 microns, and the Al composition ranges from 0.2 to 0.8, so that a good quality AlGaN buffer layer can be obtained.

S204: growing an AlGaN high resistance layer on the AlGaN buffer layer.

Growing the AlGaN high-resistance layer on the AlGaN buffer layer can effectively reduce the lattice mismatch between the AlGaN buffer layer and the AlGaN high-resistance layer, so as to improve the crystal quality of the obtained AlGaN high-resistance layer, and the quality of the AlGaN high-resistance layer If it is guaranteed, the quality of other epitaxial materials grown on the AlGaN high resistance layer can be further improved.

Exemplarily, the growth temperature of the AlGaN high resistance layer ranges from 1000° C. to 1200° C., and the growth pressure of the AlGaN high resistance layer ranges from 40 to 70 mbar.

The growth temperature and the growth pressure of the AlGaN high resistance layer are respectively in the above ranges, which can effectively improve the growth quality of the obtained AlGaN high resistance layer.

Optionally, the thickness of the AlGaN high-resistance layer ranges from 1.0 to 2.0 microns, which can ensure the growth quality of the AlGaN high-resistance layer itself, and at the same time effectively achieve the goal of high resistance, that is, ensure the high-resistance effect.

Optionally, the AlGaN high resistance layer is doped with carbon (C), and the doping concentration of the carbon element is 10 ¹⁹ cm ⁻³ to 10 ²⁰ cm ⁻³ .

Doping the AlGaN high-resistance layer with carbon can improve the high-resistance effect of the AlGaN high-resistance layer, and the doping concentration of the carbon element within the above range can also ensure the quality of the AlGaN high-resistance layer itself.

Optionally, the composition range of Al in the AlGaN high resistance layer is 0.1-0.3.

S205: growing a GaN channel layer on the AlGaN high resistance layer.

Optionally, the growth conditions of the GaN channel layer include: a growth temperature of 1050° C.˜1150° C. and a pressure of 150˜250 mbar. A GaN channel layer with better quality can be obtained.

Exemplarily, the thickness of the GaN channel layer ranges from 300 nm to 600 nm, so that the quality of the obtained GaN channel layer is better, and the quality of the finally obtained HEMT epitaxial wafer is improved.

S206: growing an AlN insertion layer on the GaN channel layer.

Optionally, the growth conditions of the AlN insertion layer include: the growth temperature is 1000° C.˜1100° C., and the pressure is 30˜70 mbar. A good quality AlN insertion layer can be obtained.

Optionally, the thickness of the AlN insertion layer ranges from 0.8nm to 1.2nm. For example, the AlN insertion layer has a thickness of 1 nm.

S207: growing an AlGaN barrier layer on the AlN insertion layer.

Optionally, the growth temperature of the AlGaN barrier layer is 1000° C.˜1100° C., and the growth pressure of the AlGaN barrier layer is 40˜70 mbar. The quality of the obtained AlGaN barrier layer is better.

In an implementation manner provided in the present disclosure, the growth temperature of the AlGaN barrier layer may be 1050°C. This disclosure does not limit this.

Optionally, the thickness of the AlGaN barrier layer ranges from 20nm to 25nm.

Optionally, the Al composition in the AlGaN barrier layer is between 0.20 and 0.25.

S208: growing a GaN cap layer on the AlGaN barrier layer.

Optionally, the growth temperature of the GaN cap layer is 1000° C.˜1100° C., and the growth pressure of the AlGaN barrier layer is 100˜200 mbar. The quality of the obtained GaN capping layer is better.

Optionally, the thickness of the GaN capping layer ranges from 3nm to 5nm.

Optionally, after the growth of the epitaxial structure is completed, the temperature of the reaction chamber is lowered to room temperature in a nitrogen atmosphere to complete the epitaxial growth.

It should be noted that, in the embodiments of the present disclosure, VeecoK 465i or C4 or RB MOCVD (MetalOrganic Chemical Vapor Deposition, metal organic compound chemical vapor deposition) equipment is used to realize the LED growth method. Use high-purity H ₂ (hydrogen) or high-purity N ₂ (nitrogen) or a mixture of high-purity H ₂ and high-purity N ₂ as carrier gas, high-purity NH ₃ as N source, trimethylgallium (TMGa) and three Ethyl gallium (TEGa) as gallium source, trimethyl indium (TMIn) as indium source, silane (SiH4) as N-type dopant, trimethyl aluminum (TMAl) as aluminum source, dimagnesocene (CP ₂ Mg ) as the P-type dopant, and ferrocene (Cp ₂ Fe) as the precursor of the iron (Fe) source. Carbon tetrabromide (CBr ₄ ) is used as the precursor of the carbon (C) source, and Cl ₂ is used as the etching gas.

FIG. 3 is a schematic structural diagram of a HEMT epitaxial wafer provided by an embodiment of the present disclosure. Referring to Figure 3, the HEMT epitaxial wafer includes:

Si substrate 1 , composite transition layer 2 , AlGaN buffer layer 3 , AlGaN high resistance layer 4 , GaN channel layer 5 , AlGaN barrier layer 6 and GaN capping layer 7 stacked on the Si substrate 1 in sequence.

Among them, the composite transition layer 2 includes a low-temperature BP nucleation layer 21, a high-temperature BP nucleation layer 22, and a pre-coated Al layer 23 stacked on the Si substrate 1 in sequence. The growth temperature of the low-temperature BP nucleation layer 21 is lower than that of the high-temperature BP nucleation layer. The growth temperature of the core layer 22.

Exemplarily, the growth temperature of the low-temperature BP nucleation layer ranges from 600°C to 800°C, and the growth temperature of the high-temperature BP nucleation layer ranges from 900°C to 1100°C;

The thickness of the low-temperature BP nucleation layer ranges from 10nm to 40nm, and the growth temperature of the high-temperature BP nucleation layer ranges from 150nm to 250nm;

The growth pressure of the low temperature BP nucleation layer ranges from 200mbar to 300mbar, and the growth pressure of the high temperature BP nucleation layer ranges from 50mbar to 100mbar.

Exemplarily, the growth temperature of the pre-laid Al layer ranges from 900°C to 1100°C, the growth pressure of the pre-laid Al layer ranges from 40mbar to 70mbar, and the thickness of the pre-laid Al layer ranges from 1nm ~5nm.

The following table 1 is the lattice field number and forbidden band width table of Si, BP, GaN, AlN and other substances, combined with table 1, we can know:

Compared with the conventional AlN nucleation layer, the BP nucleation layer has a smaller lattice mismatch degree with the GaN epitaxial layer, which can reduce the dislocation density caused by the lattice mismatch, thereby improving the crystal quality of the epitaxial layer growth . When AlN is used as the nucleation layer, its lattice constant is smaller than that of Si and GaN, and its forbidden band width is larger than that of Si and GaN, while the lattice constant and forbidden band width of BP are between Si and GaN, which can be easily It plays a good buffer transition role between the Si substrate and the GaN epitaxial layer, which is conducive to reducing the lattice mismatch between the Si substrate and the epitaxial layer and improving the crystal quality. In addition, the growth of the pre-laid Al layer after the growth of the high-temperature BP nucleation layer can avoid the contact reaction between _NH3 and BP to grow BN, because there is a large lattice mismatch between BN and GaN, thereby avoiding the dislocation of the GaN epitaxial layer increase in density.

Table 1

parameter/substance Si BP GaN AlN Lattice constant (nm) 0.5431 0.4538 0.3189 0.3112 Bandgap (eV) 1.12 2.0 3.4 6.2

However, the growth of the high-temperature BP nucleation layer, the low-temperature BP nucleation layer, and the pre-coated Al layer using the above-mentioned growth conditions and thickness can ensure that the obtained high-temperature BP nucleation layer, low-temperature BP nucleation layer, and pre-coated Al layer meet the above mitigation requirements. Lattice mismatch, improving crystal quality requirements.

Optionally, the HEMT epitaxial wafer further includes: an AlN insertion layer 8 located between the GaN channel layer and the AlGaN barrier layer.

Exemplarily, the thickness of the AlN insertion layer 8 ranges from 0.8nm to 1.2nm.

For example, the AlN insertion layer has a thickness of 1 nm.

Exemplarily, the AlGaN buffer layer is an undoped AlGaN layer, the thickness ranges from 2.0 to 3.0 microns, and the Al composition ranges from 0.2 to 0.8, which can ensure the quality of the AlGaN buffer layer.

Exemplarily, the thickness of the AlGaN high-resistance layer ranges from 1.0 to 2.0 microns, which can ensure the growth quality of the AlGaN high-resistance layer itself, and at the same time effectively achieve the goal of high resistance, that is, ensure the high-resistance effect.

Exemplarily, the AlGaN high resistance layer is doped with C, and the doping concentration of the carbon element is 10 ¹⁹ cm ⁻³ to 10 ²⁰ cm ⁻³ . Doping the AlGaN high-resistance layer with carbon can improve the high-resistance effect of the AlGaN high-resistance layer, and the doping concentration of the carbon element within the above range can also ensure the quality of the AlGaN high-resistance layer itself.

Exemplarily, the thickness of the GaN channel layer ranges from 300 to 600 nm, so that the quality of the obtained GaN channel layer is better, and the quality of the finally obtained HEMT epitaxial wafer is improved.

For example, the GaN channel layer has a thickness of 400 nm. The thickness of the GaN channel layer is more appropriate, the cost is more reasonable, and the quality of the HEMT epitaxial wafer can be effectively improved.

Exemplarily, the thickness range of the AlGaN barrier layer is 20-25 nm, which can ensure the quality of the HEMT epitaxial wafer.

Exemplarily, the GaN capping layer can be a P-type GaN layer, which is convenient for preparation and acquisition.

Optionally, the thickness of the GaN capping layer ranges from 3 to 5 nm, and the overall quality of the obtained GaN capping layer is better.

Exemplarily, the impurity in the GaN capping layer is Mg, which is convenient for preparation and acquisition.

It should be noted that FIG. 3 is only one implementation of the HEMT epitaxial wafer provided by the embodiment of the present disclosure. In other implementations provided by the present disclosure, the HEMT epitaxial wafer can also be other forms of HEMT including a reflective layer. Epitaxial wafer, the present disclosure does not limit it.

An embodiment of the present disclosure provides a HEMT device, and the HEMT device includes a HEMT epitaxial wafer as shown in FIG. 3 .

The above does not limit the present disclosure in any form. Although the present disclosure has been disclosed above through the embodiments, it is not used to limit the present disclosure. Use the technical content disclosed above to make some changes or modify equivalent embodiments as equivalent changes, but any simple modifications and equivalent changes made to the above embodiments according to the technical essence of the present disclosure without departing from the content of the technical solution of the present disclosure and modifications, all still belong to the scope of the technical solutions of the present disclosure.

Claims (10)

1. A HEMT epitaxial wafer, characterized in that, said HEMT epitaxial wafer comprises: a Si substrate, a composite transition layer, an AlGaN buffer layer, an AlGaN high resistance layer, a GaN channel layer, an AlGaN barrier layer, and a GaN capping layer sequentially stacked on the Si substrate, The composite transition layer includes a low-temperature BP nucleation layer, a high-temperature BP nucleation layer, and a pre-coated Al layer sequentially stacked on the Si substrate, and the growth temperature of the low-temperature BP nucleation layer is lower than that of the high-temperature BP nucleation layer. The growth temperature of the nuclear layer. 2. The HEMT epitaxial wafer according to claim 1, characterized in that the growth temperature of the low-temperature BP nucleation layer ranges from 600°C to 800°C, and the growth temperature of the high-temperature BP nucleation layer The value range is 900℃～1100℃; The value range of the thickness of the low-temperature BP nucleation layer is 10nm-40nm, and the value range of the growth temperature of the high-temperature BP nucleation layer is 150nm-250nm; The growth pressure of the low-temperature BP nucleation layer ranges from 200 mbar to 300 mbar, and the growth pressure of the high-temperature BP nucleation layer ranges from 50 mbar to 100 mbar. 3. The HEMT epitaxial wafer according to claim 1, characterized in that the growth temperature of the pre-laid Al layer ranges from 900°C to 1100°C, and the growth pressure of the pre-laid Al layer ranges from 40mbar-70mbar, and the thickness range of the pre-applied Al layer is 1nm-5nm. 4. The HEMT epitaxial wafer according to any one of claims 1 to 3, wherein the HEMT epitaxial wafer further comprises: an AlN insertion layer located between the GaN channel layer and the AlGaN barrier layer . 5. a preparation method of HEMT epitaxial wafer, is characterized in that, described preparation method comprises: providing a Si substrate; growing a composite transition layer on the Si substrate, the composite transition layer comprising a low-temperature BP nucleation layer, a high-temperature BP nucleation layer and a pre-coated Al layer sequentially stacked on the Si substrate; An AlGaN buffer layer, an AlGaN high resistance layer, a GaN channel layer, an AlGaN barrier layer and a GaN capping layer are sequentially grown on the composite transition layer. 6. The preparation method according to claim 5, wherein said growing a composite transition layer on said Si substrate comprises: preparing said low-temperature BP nucleation layer in the following manner: Under the condition that the growth temperature ranges from 600° C. to 800° C. and the growth pressure ranges from 200 mbar to 300 mbar, the low-temperature BP nucleation layer whose thickness ranges from 10 nm to 40 nm is grown. 7. The preparation method according to claim 5, wherein said growing a composite transition layer on said Si substrate comprises: preparing said high-temperature BP nucleation layer in the following manner: Under the condition that the growth temperature ranges from 900° C. to 1100° C. and the growth pressure ranges from 50 mbar to 100 mbar, the high-temperature BP nucleation layer whose thickness ranges from 150 nm to 250 nm is grown. 8. The preparation method according to claim 5, wherein said growing a composite transition layer on said Si substrate comprises: preparing said pre-applied Al layer as follows: Under the condition that the growth temperature ranges from 900° C. to 1100° C. and the growth pressure ranges from 40 mbar to 70 mbar, the pre-coated Al layer with a thickness ranging from 1 nm to 5 nm is grown. 9. according to the preparation method described in any one of claim 5 to 8, it is characterized in that, described preparation method also comprises: An AlN insertion layer is grown between the GaN channel layer and the AlGaN barrier layer. 10. A HEMT device, characterized in that the HEMT device comprises the HEMT epitaxial wafer according to any one of claims 1 to 4.

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