HIGH ELECTRON MOBILITY TRANSISTOR, RADIO FREQUENCY TRANSISTOR, POWER AMPLIFIER, AND PREPARATION METHOD FOR HIGH ELECTRON MOBILITY TRANSISTOR

TECHNICAL FIELD

This disclosure relates to the field of microelectronics technologies, and in particular, to a high electron mobility transistor, a radio frequency transistor, a power amplifier, and a preparation method for a high electron mobility transistor.

BACKGROUND

A wide bandgap semiconductor gallium nitride (GaN) material has advantages of a large bandgap, high breakdown field strength, a high polarization coefficient, a high electron mobility, and a high electron saturation drift velocity, and is gradually used in the field of power electronics and radio frequency.

Currently, a structure of a high electron mobility transistor based on gallium nitride has defects and needs to be improved.

SUMMARY

The present disclosure provides a high electron mobility transistor having a low ohmic contact resistance, a radio frequency transistor, a power amplifier, and a preparation method for a high electron mobility transistor.

According to one aspect, this disclosure provides a high electron mobility transistor, including at least a channel layer, a barrier layer, and a substrate layer that are sequentially disposed, where a two-dimensional electron gas layer is formed in the channel layer, and the two-dimensional electron gas layer is in contact with the barrier layer; and the high electron mobility transistor further includes a source and a drain, where the source and the drain are located on the channel layer, and the source and the drain are in ohmic contact with the channel layer. The two-dimensional electron gas layer is generated through a polarization effect at a junction interface between the channel layer and the barrier layer. The two-dimensional electron gas layer is located in the channel layer, and the two-dimensional electron gas layer is in contact with the barrier layer. Therefore, a lower ohmic contact resistance may be obtained in a surface that is of the channel layer and that faces away from the barrier layer, or it may be understood that there is a lower ohmic contact resistance between the source and the channel layer and between the drain and the channel layer, so that the high electron mobility transistor can be better used in a high frequency and power scenario.

The two-dimensional electron gas layer is a virtual layer of two-dimensional electron gas generated through a polarization effect at a heterojunction interface of the channel layer and the barrier layer. The two-dimensional electron gas layer is located in the channel layer, and the two-dimensional electron gas layer is in contact with the barrier layer.

In an implementation, a material of the channel layer may be gallium nitride (GaN), and a material of the barrier layer may be aluminum gallium nitride (AlGaN). The high electron mobility transistor may implement a high electron mobility by using the two-dimensional electron gas generated through a polarization effect at a heterojunction interface of aluminum gallium nitride and gallium nitride.

In addition, in an embodiment provided in this disclosure, the surface that is of the channel layer and that faces away from the barrier layer is a nitrogen (N) surface. Alternatively, it may be understood that a surface (namely, a surface that faces away from the substrate layer) of the high electron mobility transistor is a nitrogen surface. The channel layer, the barrier layer, and the substrate layer may be sequentially grown and formed. Therefore, during preparation of the high electron mobility transistor provided in an embodiment of this disclosure, a high electron mobility transistor with a nitrogen surface can be more easily obtained, and crystal quality of the nitrogen surface can be effectively ensured. In addition, compared with a high electron mobility transistor with a gallium (Ga) surface, the high electron mobility transistor with the nitrogen surface can implement a lower ohmic contact resistance. Therefore, the high electron mobility transistor with the nitrogen surface can be better used in a high frequency and power scenario.

In specific application, a material of the substrate layer may be silicon (Si), silicon carbide (SiC), diamond, or the like. In an implementation provided in this disclosure, the substrate layer may be made of a diamond material. Because the diamond material has higher thermal conductivity, heat dissipation performance of the component can be effectively improved. In addition, in an implementation provided in this disclosure, the channel layer, the barrier layer, and the substrate layer are sequentially grown and formed. Therefore, the diamond substrate layer may be directly grown on the barrier layer by using a process, for example, microwave plasma chemical vapor deposition (Microwave Plasma Chemical Vapor Deposition, MPCVD), so that preparation efficiency and quality of the substrate layer can be effectively improved.

For a gate, in an implementation, the gate may be disposed on the channel layer and in Schottky contact with the channel layer.

In addition, according to different structures of the high electron mobility transistor, the gate may alternatively be disposed on another structure.

For example, in an implementation provided in this disclosure, the high electron mobility transistor may further include a nucleation layer. The nucleation layer is located on a side that is of the channel layer and that faces away from the barrier layer. The gate is located on the nucleation layer, and the gate is in Schottky contact with the nucleation layer. A material of the nucleation layer may be aluminum nitride (AlN), or may be another material that facilitates forming of the channel layer. This disclosure is not limited to using AlN for this purpose and other compositions or elements may be used.

In an implementation, the barrier layer may include gallium nitride aluminum. Alternatively, the barrier layer may include a silicon-doped aluminum gallium nitride layer and an aluminum gallium nitride layer whose aluminum component is greater than 20% that are sequentially disposed in a direction away from the channel layer. The silicon-doped aluminum gallium nitride layer can adjust an energy band, to prevent a hole from being bound. The aluminum gallium nitride layer with a larger aluminum component can effectively improve an electron gas concentration. In summary, performance of the high electron mobility transistor can be effectively improved by using the silicon-doped aluminum gallium nitride layer and the aluminum gallium nitride layer whose aluminum component is greater than 20%.

In an implementation, the high electron mobility transistor may further include a high resistance layer. Specifically, the high resistance layer is located between the barrier layer and the substrate layer. The nucleation layer, the channel layer, the barrier layer, the high resistance layer, and the substrate layer may be sequentially disposed. A material of the high resistance layer may be iron (Fe)-doped or carbon (C)-doped gallium nitride. A main function of the high resistance layer is to increase a resistance value of the high electron mobility transistor, so that the high electron mobility transistor can be used in an application scenario in which a high resistance value is required.

In addition, in an implementation, the high electron mobility transistor may also be a P-type (or normally closed) transistor. For example, the high electron mobility transistor includes the channel layer, the barrier layer, and the substrate layer that are sequentially disposed. In addition, there is a P-type doped (or hole-doped) gallium nitride layer on a side that is of the channel layer and that faces away from the barrier layer. In addition, the gate is in Schottky contact with the P-type doped gallium nitride layer. The source and the drain are in ohmic contact with the channel layer. In a final component structure, the high resistance layer, the nucleation layer, and the like mentioned in the foregoing embodiments may alternatively exist. Details are not described herein again.

According to another aspect, this disclosure further provides a radio frequency transistor and a power amplifier, including any one of the foregoing high electron mobility transistors. Alternatively, it may be understood that the high electron mobility transistor provided in this disclosure may be widely used in devices such as a base station, a radar, a mobile phone, and a notebook computer. A specific application scenario of the high electron mobility transistor is not limited in this disclosure.

According to another aspect, this disclosure further provides a preparation method for a high electron mobility transistor, and the method may include: sequentially growing at least a channel layer, a barrier layer, and a substrate layer on a base material in a specific direction; removing the base material; and preparing a source and a drain on the channel layer, where the source and the drain are in ohmic contact with the channel layer. The base material may be a material like silicon (Si) or silicon carbide (SiC). It may be understood that, in this embodiment of this disclosure, a main function of the base material is to be used as a substrate used to grow an epitaxial structure like the channel layer and the barrier layer, to prepare the epitaxial structure. A material of the channel layer may be gallium nitride, and a material of the barrier layer may be aluminum gallium nitride. In addition, in this embodiment provided in this disclosure, the channel layer, the barrier layer, and the substrate layer are sequentially grown and formed. Therefore, during preparation of the high electron mobility transistor in the preparation method provided in this embodiment of this disclosure, a high electron mobility transistor with a nitrogen surface can be more easily obtained, and crystal quality of the nitrogen surface can be effectively ensured.

In an implementation, the preparation method may further include preparing a gate. The gate may be located on the channel layer, and the gate may be in Schottky contact with the channel layer.

Alternatively, in some preparation methods, before the growing a channel layer on a base material, the method may further include: growing a nucleation layer on the base material in the specific direction, where the channel layer is located on the nucleation layer.

In addition, during preparation of the gate, the gate may be located on the nucleation layer and in Schottky contact with the nucleation layer.

Alternatively, in some preparation methods, the nucleation layer may be removed after the base material is removed.

Alternatively, in some preparation methods, after the growing a nucleation layer on the base material in the specific direction, the method may further include: growing a buffer layer on the nucleation layer in the specific direction.

After the base material is removed, the nucleation layer and the buffer layer may be removed. The buffer layer is disposed to facilitate effective removal of the nucleation layer and the buffer layer itself, and quality of the channel layer is not affected.

In some preparation methods, the growing the barrier layer may specifically include: sequentially growing, in the specific direction, a silicon-doped aluminum gallium nitride layer and an aluminum gallium nitride layer whose aluminum composition is greater than 20%.

Alternatively, in some implementations, before the growing the substrate layer, the method may further include: growing a high resistance layer on a surface of the barrier layer in the specific direction. A main function of the high resistance layer is to increase a resistance value of the high electron mobility transistor, so that the high electron mobility transistor can be used in an application scenario in which a high resistance value is required.

In addition, based on the preparation method provided in this disclosure, a P-type (or normally closed) high electron mobility transistor may be further prepared. For example, when the P-type high electron mobility transistor is prepared, a P-type doped (or hole-doped) gallium nitride layer may be added on the channel layer, and the gate is in Schottky contact with the P-type doped gallium nitride layer.

It may be understood that, in a specific application, a sequence of different processes may be adaptively adjusted based on an actual requirement in the preparation method in this disclosure. This is not limited in this disclosure.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic of a structure of a current high electron mobility transistor according to an embodiment of this disclosure;

FIG. 2 is a schematic of a structure of a high electron mobility transistor according to an embodiment of this disclosure;

FIG. 3 is a schematic of a structure of another high electron mobility transistor according to an embodiment of this disclosure;

FIG. 4 is a schematic of a structure of another high electron mobility transistor in a preparation process according to an embodiment of this disclosure;

FIG. 5 is a schematic of a structure of another high electron mobility transistor according to an embodiment of this disclosure;

FIG. 6 is a schematic of a structure of another high electron mobility transistor in a preparation process according to an embodiment of this disclosure;

FIG. 7 is a schematic of a structure of another high electron mobility transistor in a preparation process according to an embodiment of this disclosure;

FIG. 8 is a schematic of a structure of another high electron mobility transistor in a preparation process according to an embodiment of this disclosure;

FIG. 9 is a schematic of a structure of another high electron mobility transistor in a preparation process according to an embodiment of this disclosure;

FIG. 10 is a schematic of a structure of another high electron mobility transistor according to an embodiment of this disclosure;

FIG. 11 is a schematic of a structure of another high electron mobility transistor according to an embodiment of this disclosure;

FIG. 12 is a flowchart of a preparation method for a high electron mobility transistor according to an embodiment of this disclosure;

FIG. 13 is a schematic of a structure of another high electron mobility transistor in a preparation process according to an embodiment of this disclosure;

FIG. 14 is a schematic of a structure of another high electron mobility transistor in a preparation process according to an embodiment of this disclosure;

FIG. 15 is a schematic of a structure of another high electron mobility transistor in a preparation process according to an embodiment of this disclosure;

FIG. 16 is a schematic of a structure of another high electron mobility transistor in a preparation process according to an embodiment of this disclosure;

FIG. 17 is a schematic of a structure of another high electron mobility transistor in a preparation process according to an embodiment of this disclosure;

FIG. 18 is a schematic of a structure of another high electron mobility transistor in a preparation process according to an embodiment of this disclosure; and

FIG. 19 is a schematic of a structure of another high electron mobility transistor according to an embodiment of this disclosure.

DESCRIPTION OF EMBODIMENTS

To make the objectives, technical solutions, and advantages of this disclosure clearer, the following further describes the various embodiments of this disclosure in detail with reference to the accompanying drawings.

To facilitate understanding of a high electron mobility transistor provided in embodiments of this disclosure, the following first describes an operating principle of the high electron mobility transistor.

The high electron mobility transistor (HEMT) achieves high electron mobility by using two-dimensional electron gas (2DEG) generated through a polarization effect at a heterojunction interface of aluminum gallium nitride (AlGaN)/gallium nitride (GaN). The two-dimensional electron gas means that motion of electrons in a direction perpendicular to a junction interface is bound by a potential well, and therefore the electrons are quantized, while motion of the electrons in a direction parallel to the junction interface is still free. Such an electron thin layer is called the two-dimensional electron gas.

A high electron mobility transistor can be used in microelectronics such as microwave radio frequency or power electronics. For example, in the field of microwave radio frequency, the high electron mobility transistor may be used as a power amplifier, and a main function of the high electron mobility transistor is to amplify a radio frequency signal inside an active antenna unit (AAU), and then transmit the radio frequency signal in a form of an electromagnetic wave through an antenna. In the field of power electronics, the high electron mobility transistor can be used as a power switch and drive. For example, in a terminal device like a mobile phone, a notebook computer, or a tablet computer, the high electron mobility transistor may be used as a switch in a charging circuit. In a device like a lidar, the high electron mobility transistor can be used as a main component of a drive.

As shown in FIG. 1, in some high electron mobility transistors, silicon (Si) or silicon carbide (SiC) is usually used as a substrate, and then materials such as aluminum nitride (AlN), gallium nitride (GaN), and aluminum gallium nitride (AlGaN) are sequentially grown on the substrate for preparation. Then, a source 02, a drain 03, and a gate 04 are prepared on an upper surface of the AlGaN layer. A two-dimensional electron gas layer 01 is formed in the GaN layer, and the two-dimensional electron gas layer 01 is in contact with the AlGaN layer. When AlGaN is prepared, nitrogen (N) atoms in a compound are first formed, and then aluminum (Al) atoms and gallium (Ga) atoms are formed on the basis of the N atoms in a specific direction. Alternatively, it may be understood that, from a micro perspective, the N atoms, the Al atoms, and the Ga atoms in the AlGaN layer are sequentially arranged, so that a surface (for example, an upper surface in the figure) of a current high electron mobility transistor is a Ga surface. However, compared with the high electron mobility transistor with the Ga surface, a high electron mobility transistor with an N surface can implement a lower ohmic contact resistance. Therefore, the high electron mobility transistor with the N surface can be better used in a high frequency and power scenario.

Therefore, an embodiment of this disclosure provides a high electron mobility transistor that can implement a lower ohmic contact resistance.

To make the objectives, technical solutions, and advantages of this disclosure clearer, the following further describes in detail with reference to the accompanying drawings and specific embodiments.

Terms used in the following embodiments are merely intended to describe specific embodiments, but are not intended to limit the scope of the embodiments of this disclosure. Terms “one”, “a”, and “this” of singular forms used in this specification and the appended claims of this disclosure are also intended to include a form like “one or more”, unless otherwise specified in the context clearly. It may be further understood that, in the following embodiments of this disclosure, “at least one” means one, two, or more.

Reference to “an embodiment” or the like described in this specification means that one or more embodiments of this disclosure include a particular feature, structure, or characteristic described in combination with the embodiment. Therefore, in this specification, statements, such as “in an embodiment”, “in some implementations”, and “in another implementation”, that appear at different places do not necessarily mean referring to a same embodiment, instead, the statements mean referring to “one or more but not all of embodiments”, unless otherwise specifically emphasized in other ways. Terms “include”, “have”, and variants of the terms all mean “include but are not limited to”, unless otherwise specifically emphasized in other ways.

As shown in FIG. 2, an embodiment of this disclosure provides a high electron mobility transistor. The high electron mobility transistor includes a channel layer 30, a barrier layer 20, and a substrate layer 10. The channel layer 30, the barrier layer 20, and the substrate layer 10 are sequentially disposed in a specific direction. A two-dimensional electron gas layer 01 (represented by a dashed line in the figure) is formed in the channel layer 30, and the two-dimensional electron gas layer 01 is in contact with the barrier layer 20. A source 02, a gate 04, and a drain 03 are located on the channel layer 30, the source 02 and the drain 03 are in ohmic contact with the channel layer 30, and the gate 04 is in Schottky contact with the channel layer 30.

In the high electron mobility transistor provided in this disclosure, the two-dimensional electron gas layer is located in the channel layer, and is in contact with the barrier layer. Therefore, a surface that is of the channel layer and that faces away from the barrier layer can implement a lower ohmic contact resistance, so that the high electron mobility transistor can be better used in a high frequency and power scenario.

The two-dimensional electron gas layer 01 is a virtual layer of two-dimensional electron gas generated through a polarization effect at a heterojunction interface of the channel layer 30 and the barrier layer 20. The two-dimensional electron gas layer 01 is located in the channel layer 30, and is in contact with the barrier layer 20.

Ohmic contact means that when a semiconductor is in contact with a metal, a barrier is usually formed. However, when doping density of the semiconductor is high, electrons may pass through the barrier through a tunnel effect, to form low-resistance ohmic contact. Good ohmic contact facilitates current input and output. Schottky contact means that when the gate 04 (for example, a metal material) and the channel layer 30 (for example, a semiconductor material) are in contact, an energy band of the semiconductor is bent at a boundary surface, to form a Schottky barrier.

In specific implementation, a material of the channel layer 30 may be GaN. A material of the barrier layer 20 may be AlGaN. The high electron mobility transistor may implement a high electron mobility by using the two-dimensional electron gas generated through a polarization effect at a heterojunction interface of AlGaN and GaN.

In this embodiment provided in this disclosure, a surface (namely, a surface that faces away from the substrate layer 10) of the high electron mobility transistor is a nitrogen (N) surface. Therefore, the high electron mobility transistor can implement a lower ohmic contact resistance, or it may be understood that there is a lower ohmic contact resistance between the source 02 and the channel layer 30 and between the drain 03 and the channel layer 30, so that the high electron mobility transistor can be better used in a high frequency and power scenario. In addition, in this embodiment provided in this disclosure, the channel layer 30, the barrier layer 20, and the substrate layer 10 are sequentially grown and formed. Therefore, during preparation of the high electron mobility transistor provided in this embodiment of this disclosure, a high electron mobility transistor with an N surface can be more easily obtained, and crystal quality of the N surface can be effectively ensured. In addition, compared with a high electron mobility transistor with a gallium (Ga) surface, the high electron mobility transistor with the N surface can implement a lower ohmic contact resistance. Therefore, the high electron mobility transistor with the N surface can be better used in a high frequency and power scenario.

A thickness of the channel layer 30 may be any value between 50 nm and 500 nm, and a thickness of the barrier layer 20 may be any value between 10 nm and 100 nm. In specific application, the thicknesses of the channel layer 30 and the barrier layer 20 may be appropriately set based on an actual requirement. This is not specifically limited in this disclosure. In addition, in another implementation, the material of the channel layer 30 may alternatively be gallium arsenide (GaAs) or the like, and the material of the barrier layer 20 may be gallium arsenide (AlGaAs) or the like. In specific application, the materials of the channel layer 30 and the barrier layer 20 may be appropriately selected and adjusted based on an actual requirement. This is not specifically limited in this disclosure.

In specific application, a material of the substrate layer 10 may be silicon (Si), silicon carbide (SiC), diamond, or the like.

At room temperature (for example, 25° C.), thermal conductivity of Si is about 150 W/mK, thermal conductivity of SiC is about 370 W/mK, and thermal conductivity of diamond is usually greater than 1000 W/mK.

Because the thermal conductivity of Si or SiC is relatively poor, a large thermal resistance is formed, and the thermal conductivity decreases with temperature rise, a problem of insufficient heat dissipation capability is faced in some high-power application scenarios. As a result, a high electron mobility transistor can run only at low power density, to ensure long-term reliability of the transistor. For example, theoretical output power density of a GaN HMET component may be more than 40 W/mm. However, when a substrate material is Si or SiC, to ensure long-term reliability of a high electron mobility transistor, the high electron mobility transistor needs to run at low power density (for example, less than 10 W/mm). This is not conducive to working performance of the high electron mobility transistor.

Therefore, the high electron mobility transistor with a diamond substrate can implement better heat dissipation. In addition, this further helps improve power density of the high electron mobility transistor.

When the substrate is made of a diamond material, in a preparation process, the GaN layer is usually bonded to the diamond substrate. However, a bonding process is complex and costly, which is not conducive to large-scale production. The bonding process requires a diamond surface to be very flat (for example, surface roughness is less than 1 nm) through processing. However, hardness of the diamond is high, and it is very difficult to process the surface to be very flat. In addition, a bonding process is also a monolithic process, and piece-by-piece processing and production may cause a problem of low production efficiency. In addition, during bonding, a bonding layer material, for example, silicon nitride (SiN), needs to be added between the GaN layer and the diamond substrate. Because the bonding layer material has a high thermal resistance, heat dissipation performance of the component is reduced.

In addition, because the diamond material has good thermal conductivity, heat dissipation performance of the component can be significantly improved.

In this embodiment provided in this disclosure, the diamond material may be used as the substrate layer 10, to improve heat dissipation performance of the component.

In addition, in this embodiment provided in this disclosure, the channel layer 30, the barrier layer 20, and the substrate layer 10 are sequentially grown and formed. Therefore, the diamond substrate layer 10 may be directly grown on the barrier layer 20 by using a process, for example, microwave plasma chemical vapor deposition (MPCVD), so that preparation efficiency and quality of the substrate layer 10 can be effectively improved.

Alternatively, it may be understood that, in the high electron mobility transistor provided in this disclosure, when the substrate layer 10 is prepared, bonding between the substrate layer 10 and the barrier layer 20 by using a bonding process can be avoided, thereby reducing a manufacturing difficulty and manufacturing costs. In addition, because the bonding process is avoided, adding a bonding material (for example, SiN) with a large thermal resistance between the substrate layer 10 and the barrier layer 20 is avoided. Therefore, heat dissipation performance of the component can be ensured.

In specific implementation, the HMET component may have various structures.

For example, as shown in FIG. 3, in another embodiment provided in this disclosure, the high electron mobility transistor further includes a nucleation layer 40, and the nucleation layer 40 is located on a side that is of the channel layer 30 and that faces away from the barrier layer 20. A material of the nucleation layer 40 may be AlN. In addition, a thickness of the nucleation layer 40 may be any value between 10 nm and 50 nm. In specific application, the thickness of the nucleation layer 40 may be appropriately set based on an actual requirement. This is not specifically limited in this disclosure.

Specifically, during preparation, to facilitate growth of the channel layer 30, the nucleation layer 40 may be first grown, and then the channel layer 30 is grown on the basis of the nucleation layer 40.

As shown in FIG. 4, it may be understood that, during preparation of the high electron mobility transistor, a base material 100 used to grow the channel layer 30 or the nucleation layer 40 is usually provided. The base material 100 is usually made of a Si or SiC material.

In a current preparation process, it is difficult to directly grow the channel layer 30 on the base material 100. Therefore, the nucleation layer 40 may be first grown on the base material 100, so that the channel layer 30 may be grown on the nucleation layer 40.

Alternatively, it may be understood that because the GaN channel layer 30 and the Si or SiC base material 100 are made of different materials, the channel layer 30 and the base material 100 usually have different lattice constants and different thermal expansion coefficients. If the GaN channel layer 30 is directly grown on the Si or SiC base material 100, a large quantity of hexagonal defects may occur between the channel layer 30 and the base material 100 due to problems such as lattice mismatch and thermal adaptation. Such defects are macro defects, and a crystal surface fluctuates greatly, which destroys continuity of a crystal film, and results in extremely difficult preparation of the component and low quality. In addition, when the GaN channel layer 30 is directly grown on the Si or SiC base material 100, oxygen impurity ionization causes the channel layer 30 to have a high background carrier concentration. Therefore, mobility of electrons is significantly reduced, and working performance of the component is affected.

Therefore, to grow a high-quality channel layer 30 with an N surface, the nucleation layer 40 may be first grown on the base material 100, and then the channel layer 30 is grown on the nucleation layer 40.

As shown in FIG. 3, in this embodiment provided in this disclosure, the nucleation layer 40 generated due to a preparation process procedure may not be removed, to reduce preparation costs and simplify the preparation process. Therefore, a final product structure of the high electron mobility transistor may include the nucleation layer 40.

In addition, during preparation of the electrodes, the source 02 and the drain 03 may pass through the nucleation layer 40 and be in ohmic contact with the channel layer 30, and the gate 04 may be located on the nucleation layer 40 and be in Schottky contact with the nucleation layer 40.

It may be understood that, in another implementation, the gate 04 may also pass through the nucleation layer 40 and be in Schottky contact with the channel layer 30. This is not limited in this disclosure.

In specific implementation, the barrier layer 20 may be an AlGaN material, or may be a doped AlGaN material.

For example, in an embodiment provided in this disclosure, the barrier layer 20 may include a Si-doped AlGaN layer and an AlGaN layer whose Al component is greater than 20% that are sequentially disposed in a direction away from the channel layer 30. The Si-doped AlGaN layer can adjust an energy band to prevent a hole from being bound. The AlGaN layer with a larger Al component can effectively improve an electron gas concentration. In summary, performance of the high electron mobility transistor can be effectively improved by using the Si-doped AlGaN layer and the AlGaN layer whose Al component is greater than 20%.

It may be understood that in specific application, an overall thickness of the barrier layer 20 may be between 10 nm and 100 nm. A thickness of the Si-doped AlGaN layer may be between 10 nm and 50 nm. A thickness of the AlGaN layer whose Al component is greater than 20% may be between 1 nm and 20 nm. In addition, in the AlGaN layer whose Al component is greater than 20%, the Al component may be 21%, 22%, 30%, or the like. A specific proportion of the Al component is not limited in this disclosure. In addition, the overall thickness of the barrier layer 20, the thickness of the Si-doped AlGaN layer, and the thickness of an AlGaN layer whose Al component is greater than 20% may be adaptively adjusted based on an actual situation. This is not limited in this disclosure.

In addition, as shown in FIG. 5, in another implementation, the high electron mobility transistor may further include a high resistance layer 50.

Specifically, the high resistance layer 50 is located between the barrier layer 20 and the substrate layer 10. The nucleation layer 40, the channel layer 30, the barrier layer 20, the high resistance layer 50, and the substrate layer 10 may be formed by sequentially growing in a specific direction.

The high resistance layer 50 may be iron (Fe)-doped or carbon (C)-doped GaN. A main function of the high resistance layer 50 is to increase a resistance value of the high electron mobility transistor, so that the high electron mobility transistor can be used in an application scenario in which a high resistance value is required.

In a specific application, a thickness of the high resistance layer 50 may be any value between 10 nm and 500 nm. In addition, in the high resistance layer 50, a specific concentration of doped Fe or C may be appropriately set based on an actual requirement. This is not limited in this disclosure.

For ease of clearly understanding the technical solutions of this disclosure, the following describes in detail a forming process of a high electron mobility transistor.

As shown in FIG. 6, a nucleation layer 40, a channel layer 30, a barrier layer 20, and a high resistance layer 50 may be sequentially grown on a base material 100 in a specific direction.

As shown in FIG. 7, the substrate layer 10 is grown on the high resistance layer 50.

As shown in FIG. 8, the component is flipped.

As shown in FIG. 9, the base material 100 is removed.

As shown in FIG. 10, a gate 04, a drain 03, and a source 02 are prepared on a surface of the nucleation layer 40. The gate 04 is in Schottky contact with the nucleation layer 40, and the source 02 and the drain 03 are in ohmic contact with the channel layer 30.

It may be understood that high electron mobility transistors are mainly classified into two types: an N-type (or normally open) transistor and a P-type (or normally closed) transistor. N-type high electron mobility transistors can be widely used in the field of microwave radio frequency. For example, the N-type high electron mobility transistor may be used in a device like a base station or a radar, and is configured to perform a function like amplifying a radio frequency signal. P-type high electron mobility transistors can be widely used in the field of power electronics. For example, in a terminal device like a mobile phone or a notebook computer, the P-type high electron mobility transistor may be used as a drive, a switch, or the like.

In the foregoing embodiment, an N-type (or normally open) high electron mobility transistor is used as an example for specific description.

Certainly, in another implementation, a P-type (or normally closed) high electron mobility transistor is adaptively designed based on the foregoing structure. Alternatively, it may be understood that, in the P-type high electron mobility transistor, a P-type doped (or hole-doped) GaN layer may be added based on the HMET component in any one of the foregoing embodiments.

For example, as shown in FIG. 11, in an embodiment provided in this disclosure, a high electron mobility transistor includes a channel layer 30, a barrier layer 20, and a substrate layer 10 that are formed by sequentially growing in a specific direction. In addition, there is a P-type doped GaN layer 60 on a side that is of the channel layer 30 and that faces away from the specific direction. In addition, a gate 04 is in Schottky contact with the P-type doped GaN layer 60. A source 02 and a drain 03 are in ohmic contact with the channel layer 30.

It may be understood that, in a final component structure, the high resistance layer 50, the nucleation layer 40, and the like mentioned in the foregoing embodiments may alternatively exist. Details are not described herein again.

Refer to FIG. 12. An embodiment of this disclosure further provides a preparation method for a high electron mobility transistor, and the method may include the following steps.

S100: Sequentially grow at least a channel layer, a barrier layer, and a substrate layer on a base material in a specific direction.

S200: Remove the base material.

S300: Prepare a source and a drain on the channel layer. The source and the drain are in ohmic contact with the channel layer.

In specific preparation, the specific direction refers to any direction in space. For example, in a conventional preparation manner, to facilitate obtaining of good forming quality, the layers of materials are usually formed by sequentially growing from bottom to top. Therefore, the specific direction may be a direction from bottom to top. It may be understood that in another implementation, the specific direction may be a direction from top to bottom, or may be a direction from left to right. This is not specifically limited in this disclosure.

Refer to FIG. 6. In specific implementation, the base material 100 may be a material like silicon (Si) or silicon carbide (SiC). It may be understood that, in this embodiment of this disclosure, a main function of the base material 100 is to be used as a substrate used to grow an epitaxial structure like the channel layer 30 and the barrier layer 20, to prepare the epitaxial structure.

In actual application, a material of the channel layer 30 may be GaN, and a material of the barrier layer 20 may be AlGaN. In addition, in this embodiment provided in this disclosure, the channel layer 30, the barrier layer 20, and the substrate layer 10 are sequentially grown and formed. Therefore, during preparation of the high electron mobility transistor in the preparation method provided in this embodiment of this disclosure, a high electron mobility transistor with an N surface can be more easily obtained, and crystal quality of the N surface can be effectively ensured.

When the channel layer 30 and the barrier layer 20 are grown, the channel layer 30 and the barrier layer 20 may be prepared by using a process, for example, metal-organic chemical vapor deposition (MOCVD). Certainly, a preparation process of the channel layer 30 and the barrier layer 20 is not limited in this disclosure.

The substrate layer 10 may be prepared by using a material such as Si, SiC, or diamond. For example, when a diamond material is used for the substrate layer 10, the diamond material may be directly grown on the barrier layer 20 by using a process, for example, microwave plasma chemical vapor deposition (MPCVD), to implement preparation of the substrate layer 10.

Alternatively, it may be understood that, as shown in FIG. 1, in a conventional preparation method, an AlN material, an AlGaN material, and a GaN material are usually grown sequentially on the substrate layer 10 of the Si or SiC material. Finally, the source 02, the drain 03, and the gate 04 are prepared on a surface of GaN (that is, a surface that faces away from the substrate layer 10).

Refer to FIG. 2. In the preparation method provided in this disclosure, a base material (not shown in the figure) of a Si or SiC material may be used, and then the channel layer 30 (for example, GaN), the barrier layer 20 (for example, AlGaN), and the substrate layer 10 (for example, Si, SiC, or diamond) are grown on the base material. Then, the base material is removed, and the source 02, the drain 03, and the gate 04 are prepared on the channel layer 30.

According to the preparation method provided in this embodiment of this disclosure, a high-quality high electron mobility transistor with an N surface can be obtained. In addition, diamond may be directly grown and formed, to facilitate preparation of the substrate layer 10.

Refer to FIG. 8 and FIG. 9 together. When the base material 100 is removed, an etching process, a mechanical grinding process, or a combination thereof may be used.

For example, the mechanical grinding process may be first used to perform thinning processing on the base material 100, and then the etching process is used to remove the residual base material 100. In this way, removal efficiency and quality of the base material 100 can be improved.

It may be understood that, in specific implementation, a process of removing the base material 100 is not limited in this disclosure.

In addition, during specific preparation, to ensure forming quality of the channel layer 30, before the channel layer 30 is prepared on the base material 100, the method may further include: growing the nucleation layer 40 on the base material 100 in the specific direction, and then growing the channel layer 30 on the nucleation layer 40. A material of the nucleation layer 40 may be AlN, or C-doped or Fe-doped AlN. A specific material composition of the nucleation layer 40 is not limited in this disclosure.

During specific implementation, after the base material 100 is removed, the nucleation layer 40 may not be removed, so that a preparation process procedure can be simplified, and preparation efficiency can be improved.

In addition, refer to FIG. 10. During preparation of the electrodes, the source 02 and the drain 03 need to keep in ohmic contact with the channel layer 30. Therefore, before the source 02 and the drain 03 are prepared, a via that penetrates to a surface of the channel layer 30 may be further prepared on the nucleation layer 40 in a mechanical drilling or etching manner. Finally, the source 02 and the drain 03 may be prepared in different vias, so that the source 02 and the drain 03 keep in ohmic contact with the channel layer 30.

The gate 04 may be directly prepared on a surface of the nucleation layer 40, and is in Schottky contact with the nucleation layer 40. Alternatively, a via that penetrates to the surface of the channel layer 30 may be prepared on the nucleation layer 40, and the gate 04 keeps in Schottky contact with the channel layer 30.

In addition, after the base material 100 is removed, the nucleation layer 40 may be further removed. For example, the nucleation layer 40 may be removed by using an etching process. Certainly, when the nucleation layer 40 is removed, another process like mechanical grinding may alternatively be used. This is not limited in this disclosure.

Based on a current removal process, when the nucleation layer 40 is separately removed, quality of the surface of the channel layer 30 may be affected.

Therefore, as shown in FIG. 13, during specific preparation, the method may further include: after the nucleation layer 40 is grown, growing a buffer layer 70 on the surface of the nucleation layer 40 in the specific direction, and then growing the channel layer 30 on a surface of the buffer layer 70. A material of the buffer layer 70 may be AlGaN, and may be prepared by using a process like a metal-organic chemical vapor deposition process.

When the buffer layer 70 and the nucleation layer 40 are removed, a process combining thermal oxidation and wet etching may be used. Temperature required by a thermal oxidation process is generally between 550° C. and 650° C., and a time is about 30 to 60 minutes. A main solution in a wet etching process is potassium hydroxide (KOH). In the thermal oxidation process, sufficient oxygen is first injected to fully oxidize AlN and AlGaN. AlN, AlGaN, and oxygen react to generate aluminum trioxide (Al₂O₃), gallium oxide (Ga₂O₃), and nitrogen (N₂), where the oxide Al₂O₃and Ga₂O₃may be etched off by a KOH solution of 70° C., and this method has little impact on the GaN channel layer 30. Alternatively, it may be understood that, in a high-temperature oxidation temperature condition, AlGaN is more likely to be oxidized than GaN. A main reason why AlGaN is more easily oxidized than GaN is that Gibbs free energy (Gibbs free energy) of Al₂O₃obtained through reaction is greater than Gibbs free energy of Ga₂O₃obtained through reaction. In this way, impact on the GaN channel layer 30 can be reduced as much as possible.

In addition, during preparation of the barrier layer 20, AlGaN may be directly grown on the surface of the channel layer 30 by using a metal-organic chemical vapor deposition method.

Alternatively, a Si-doped AlGaN layer and an AlGaN layer whose Al component is greater than 20% may be sequentially grown on the surface of the channel layer 30 in the specific direction. The Si-doped AlGaN layer can adjust an energy band to prevent a hole from being bound. The AlGaN layer with a larger Al component can effectively improve an electron gas concentration. In summary, performance of the high electron mobility transistor can be effectively improved by using the Si-doped AlGaN layer and the AlGaN layer whose Al component is greater than 20%.

In addition, in some preparation methods, before the substrate layer 10 is grown, the method may further include: growing a high resistance layer 50 on the surface of the barrier layer 20 in the specific direction. The high resistance layer 50 may be iron (Fe)-doped or carbon (C)-doped GaN. The high resistance layer 50 can be prepared by using a process, for example, metal-organic chemical vapor deposition. A main function of the high resistance layer 50 is to increase a resistance value of the high electron mobility transistor, so that the high electron mobility transistor can be used in an application scenario in which a high resistance value is required.

Certainly, in specific implementation, a specific method for preparing the high resistance layer 50 is not limited in this disclosure.

For ease of clearly understanding the technical solutions of this disclosure, the following describes in detail another forming process of a high electron mobility transistor.

As shown in FIG. 14, a nucleation layer 40, a buffer layer 70, a channel layer 30, a barrier layer 20, and a high resistance layer 50 may be sequentially grown on a base material 100 in a specific direction.

As shown in FIG. 15, the substrate layer 10 is grown on the high resistance layer 50.

As shown in FIG. 16, the component is flipped.

As shown in FIG. 17, the base material 100 is removed.

As shown in FIG. 18, the nucleation layer 40 and the buffer layer 70 are removed.

As shown in FIG. 19, a gate 04, a drain 03, and a source 02 are prepared on a surface of the channel layer 30. The gate 04 is in Schottky contact with the channel layer 30, and the source 02 and the drain 03 are in ohmic contact with the channel layer 30.

In the foregoing preparation method, a preparation method for an N-type (or normally open) high electron mobility transistor is used as an example for specific description.

Certainly, in another implementation, the foregoing preparation method may alternatively be applied to preparation of a P-type (or normally closed) high electron mobility transistor.

For example, as shown in FIG. 11, when the P-type high electron mobility transistor is prepared, a P-type doped GaN layer 60 may be added on the channel layer 30, and the gate 04 is in Schottky contact with the P-type doped GaN layer 60.

The foregoing descriptions are merely specific implementations of this disclosure, but are not intended to limit the protection scope of this disclosure. Any variation or replacement readily figured out by a person skilled in the art within the technical scope disclosed in this disclosure shall fall within the protection scope of this disclosure. Therefore, the protection scope of this disclosure shall be subject to the protection scope of the claims.

	Number	Date	Country
Parent	PCT/CN2021/133250	Nov 2021	WO
Child	18676360		US

HIGH ELECTRON MOBILITY TRANSISTOR, RADIO FREQUENCY TRANSISTOR, POWER AMPLIFIER, AND PREPARATION METHOD FOR HIGH ELECTRON MOBILITY TRANSISTOR

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