An AlScN-based enhanced GaN HEMT device and a preparation method thereof

Abstract

This invention relates to an enhancement-mode GaN HEMT device based on AlScN and its fabrication method. The GaN HEMT device includes: a substrate layer, a nucleation transition layer, a GaN buffer layer, a GaN channel layer, and an AlScN layer. 1‑ x Sc x N-barrier layer, Al 1‑y Sc y N-cap layer, source, drain and gate, substrate layer, nucleation transition layer, GaN buffer layer, GaN channel layer, Al 1‑x Sc x The N-type barrier layers are stacked sequentially, with 15% ≤ x ≤ 25%; Al 1‑ y Sc y The N-cap layer, source, and drain are all located in Al. 1‑x Sc x On the N-barrier layer, Al 1‑y Sc y The N-cap layer is located between the source and drain, with y > 30%; the source and drain are separated and symmetrically distributed; the gate is located between the source and drain. The two AlScN films with different Sc doping concentrations exhibit good lattice matching at the interface. This allows for the generation of a higher concentration of 2DEG at the heterojunction through piezoelectric polarization, increasing the drain current of the HEMT device. Furthermore, ferroelectric polarization enables non-volatile modulation of the HEMT, changing the threshold voltage from negative to positive, thus realizing an enhancement-mode HEMT device. Simultaneously, it reduces drain current collapse, significantly improving the device's electrical performance.

Description

Technical Field

[0001] This invention belongs to the field of power semiconductor technology, specifically relating to an enhancement-mode GaN HEMT device based on AlScN and its fabrication method. Background Technology

[0002] In recent years, with the development of integrated circuit technology, the application range of ferroelectric thin films in semiconductor devices has gradually expanded. Ferroelectric materials, as a special type of dielectric material, not only possess spontaneous polarization characteristics within a certain temperature range, but also exhibit nonlinear changes in polarization intensity and direction with alterations in the applied electric field, meaning they can be modulated by the external electric field. Based on this characteristic, integrating ferroelectric thin films with HEMT devices allows the polarization charge of the ferroelectric material to ferroelectrically modulate the heterojunction energy band in the device, thereby achieving the goal of 2DEG control.

[0003] Ferroelectrically controlled GaN HEMT devices, as a type of semiconductor power device, are based on the principle of growing a ferroelectric material layer on top of the AlGaN / GaN heterojunction in the HEMT device structure. The threshold voltage of the device is continuously adjustable by utilizing the nonlinear control of the polarization intensity and direction of the ferroelectric thin film by an external electric field. Furthermore, after the applied gate voltage is removed, the ferroelectric thin film exhibits positive and negative residual polarization, thus contributing to the excellent threshold voltage retention characteristics of the GaN HEMT device.

[0004] Currently, in the design of high electron mobility transistors (HEMTs), perovskite-type ferroelectric materials are often integrated with transistors to enhance their gate control capabilities. However, due to the significant differences in properties between perovskite and GaN epitaxial structures, the interface between the two is extremely complex, potentially exhibiting different semiconductor or insulator properties. This uncertainty could become a major obstacle to the development of ferroelectrically modulated HEMT devices. Therefore, how to design and fabricate GaN HEMT devices with stable ferroelectric control remains a problem worthy of in-depth investigation.

[0005] Existing GaN HEMT devices mostly utilize perovskite ferroelectric materials such as lead zirconate titanate (PZT) and barium titanate (BTO) for ferroelectric modulation. However, these materials still have some limitations. For example, the large lattice mismatch between perovskite ferroelectrics and semiconductor materials necessitates fabrication through heteroepitaxial growth and substrate lift-off techniques. Their multi-component nature requires precise control of elemental ratios during thin film fabrication. Furthermore, the complex processing steps for common perovskite ferroelectric materials severely hinder the large-scale production and manufacturing of these high-performance devices. Even nanometer-thick ferroelectric thin films made from perovskite ferroelectric materials are prone to generating significant leakage currents, increasing the risk of HEMT device failure during use.

[0006] Meanwhile, GaN HEMT devices mostly use AlGaN as a barrier layer, utilizing its piezoelectric polarization effect to provide a high-concentration, high-mobility two-dimensional electron gas. However, the polarization effect of the AlGaN barrier layer has very limited modulation effect on the band structure of the AlGaN / GaN heterojunction, and the 2DEG concentration at the AlGaN heterojunction interface strongly depends on the thickness of the AlGaN barrier layer and the Al composition. Therefore, AlGaN material as a barrier layer is difficult to provide a higher carrier concentration in HEMT devices, thus seriously affecting the device's operating performance and efficiency.

[0007] In summary, existing GaN HEMT devices using perovskite ferroelectric materials for ferroelectric modulation suffer from problems such as large lattice mismatch between perovskite ferroelectric materials and semiconductor materials, complex fabrication processes, and large leakage currents. Using AlGaN as a barrier layer makes it difficult to provide higher carrier concentrations in HEMT devices, which seriously affects the device's operating performance and efficiency. Summary of the Invention

[0008] To address the aforementioned problems in the prior art, this invention provides an enhanced GaNHEMT device based on AlScN and its fabrication method. The technical problem to be solved by this invention is achieved through the following technical solution:

[0009] This invention provides an enhancement-mode GaN HEMT device based on AlScN, comprising: a substrate layer, a nucleation transition layer, a GaN buffer layer, a GaN channel layer, and AlScN. 1-x Sc x N-barrier layer, Al 1-y Sc y The N-hat layer, source, drain, and gate, among which...

[0010] The substrate layer, the nucleation transition layer, the GaN buffer layer, the GaN channel layer, and the Al 1-x Sc x N barrier layers are stacked sequentially, with 15% ≤ x ≤ 25%;

[0011] The Al 1-y Sc y The N-cap layer, the source, and the drain are all located in the Al layer. 1-x Sc x On the N-barrier layer, the Al 1- y Sc y The N-cap layer is located between the source and the drain, and the Al 1-y Sc y The end of the N-cap layer is in contact with the source and the drain, y > 30%, and the source and the drain are separated from each other and symmetrically distributed;

[0012] The gate is located between the source and the drain of the Al. 1-y Sc y On the N-hat layer.

[0013] In one embodiment of the present invention, the substrate layer is made of silicon single crystal;

[0014] The nucleation transition layer is made of AlN and has a thickness of 40-60 nm.

[0015] The GaN buffer layer is made of C-doped GaN and has a thickness of 600-1500 nm.

[0016] The thickness of the GaN channel layer is 100-300 nm;

[0017] Al 1-x Sc x The thickness of the N-barrier layer is 15-35 nm;

[0018] Al 1-y Sc y The thickness of the N-cap layer is 5-10 nm;

[0019] The thickness of the source and the drain is 320 nm, and the thickness of the gate is 150 nm.

[0020] In one embodiment of the present invention, the Al 1-x Sc x The Sc doping concentration in the N barrier layer is 25%.

[0021] In one embodiment of the present invention, the Al 1-y Sc y The Sc doping concentration in the N-cap layer is 40%.

[0022] Another embodiment of the present invention provides a method for fabricating an enhancement-mode GaN HEMT device based on AlScN, comprising the steps of:

[0023] A nucleation transition layer is fabricated on the substrate.

[0024] A GaN buffer layer is prepared on the nucleation transition layer;

[0025] A GaN channel layer is fabricated on the GaN buffer layer;

[0026] Al was prepared on the GaN channel layer using an organometallic chemical vapor deposition method. 1-x Sc x N-level barrier layer, where 15% ≤ x ≤ 25%;

[0027] Using magnetron sputtering or atomic layer deposition, on the Al 1-x Sc x Preparation of Al with N-barrier layer 1-y Sc y N-cap layer, where y > 30%;

[0028] In the Al 1-x Sc x The source is fabricated at one end of the N-type barrier layer, and the drain is fabricated at the other end, such that the source and drain are separated and symmetrically distributed, and Al 1-y Sc y The N-cap layer is located between the source and the drain, while the Al 1- y Sc y The end of the N-cap layer is in contact with the source and the drain.

[0029] In the Al 1-y Sc y A gate is fabricated on the N-cap layer such that the gate is located between the source and the drain.

[0030] In one embodiment of the present invention, an organometallic chemical vapor deposition method is used to prepare Al on the GaN channel layer. 1-x Sc x The N-barrier layer includes:

[0031] The substrate temperature in the organometallic chemical vapor deposition (HCV) apparatus was maintained at 1200°C, the pressure was set to 60 Torr, and NH3, TMAl, and Cp3Sc were used as the reaction sources, with H2 as the carrier gas. The molar flow rates of TMAl, NH3, and Cp3Sc were set to 11.5 μmol / min, 0.165 mol / min, and 5.5 μmol / min, respectively. The growth time was 10 min, and the Al was prepared. 1-x Sc x N-barrier layer.

[0032] In one embodiment of the present invention, the Al 1-x Sc x The Sc doping concentration in the N barrier layer is 25%.

[0033] In one embodiment of the present invention, magnetron sputtering or atomic layer deposition is used to deposit the Al... 1- x Sc x Preparation of Al with N-barrier layer 1-y Sc y The N-hat layer includes:

[0034] Using magnetron sputtering, pure aluminum metal targets with a purity of 99.999% and pure scandium metal targets with a purity of 99.99% were used as sputtering targets for AlScN thin films. The vacuum degree of the PC chamber was 1E-6 Torr, the gas pressure in the chamber was 10 mtorr, the sputtering power of the two targets was 50 W, and the pre-sputtering time was 10 min.

[0035] After pre-sputtering, the nitrogen flow rate was adjusted to 20 sccm, and the nitrogen to argon gas flow rate ratio was 2:1. The sputtering power of the pure aluminum metal target and the pure scandium metal target was adjusted to control the Al sputtering power. 1-y Sc y The Sc concentration in the N-cap layer, sputtering time of 3 min, yielded Al 1-y Sc y N-hat layer.

[0036] In one embodiment of the present invention, the Al 1-y Sc y The Sc doping concentration in the N-cap layer is 40%.

[0037] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0038] 1. The GaN HEMT device of the present invention uses Al with a doping concentration γ greater than 30%. 1-y Sc y When N is used as the capping layer, AlScN exhibits significant ferroelectric properties when the Sc content is >30%. By using its ferroelectric polarization characteristics as the capping layer and leveraging the flexible and tunable nature of its ferroelectric domain structure, it is possible to introduce flexible, reversible, and non-volatile control of the gate-controlled 2DEG concentration in HEMT devices. This makes the 2DEG control effect of GaN HEMT stronger, allowing the threshold voltage to change from negative to positive, and making it easier to achieve the enhancement-mode operation of HEMT.

[0039] 2. The GaN HEMT device of this invention uses Al 1-y Sc y As a cap layer structure in GaN HEMT, N prevents Al from being deposited. 1- x Sc x Oxidation of the N barrier layer surface can reduce the probability of electrons from the outer channel tunneling to the surface, thereby suppressing current collapse.

[0040] 3. The GaN HEMT device of the present invention uses Al with a Sc doping concentration greater than 30%. 1-y Sc y The N-cap layer is grown on Al with a Sc doping concentration of 15%–25%. 1-x Sc x Above the N-barrier layer, the lattice is perfectly matched, resulting in better thin film crystallization quality and better preservation of its ferroelectric properties.

[0041] 4. The GaN HEMT device of the present invention uses AlN as the nucleation transition layer of GaN HEMT, which solves the problem of lattice mismatch between the substrate and the GaN buffer layer and reduces the interfacial tension caused by the mismatch; at the same time, it can reduce the current collapse caused by interfacial mismatch, defects or trap effects and reduce static current leakage.

[0042] 5. The preparation method of the present invention uses metal-organic chemical vapor deposition to grow Al. 1-x Sc x The N-barrier layer can guarantee Al 1-x Sc x Nitrogen materials can be grown with high quality, and their piezoelectric polarization characteristics, which are far superior to those of AlGaN, enable Al... 1-x Sc x The 2DEG carrier density formed at the N / GaN heterojunction is significantly increased compared to that at the AlGaN / GaN heterojunction, thereby improving transconductance and drain current, giving GaN HEMTs excellent device characteristics.

[0043] 6. The preparation method of the present invention uses magnetron sputtering to prepare Al. 1-y Sc y The N-hat layer has a simple and easy-to-operate process, a short production cycle, and low cost, making it suitable for large-scale production environments. Attached Figure Description

[0044] Figure 1 A schematic diagram of the structure of an enhanced GaN HEMT device based on AlScN provided in an embodiment of the present invention;

[0045] Figure 2 This is a schematic diagram illustrating the fabrication process of an enhanced GaN HEMT device based on AlScN, as provided in an embodiment of the present invention. Detailed Implementation

[0046] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.

[0047] Example 1

[0048] AlScN, as a wurtzite-type ferroelectric material, has a wider band gap (Eg ~ 5-6.2 eV), resulting in thin-film devices with better stability. When the Sc doping concentration in AlScN is low, the material exhibits good piezoelectric polarization characteristics, while at higher Sc doping concentrations (Sc concentration > 30%), the material exhibits strong ferroelectricity. Furthermore, the remanent polarization of AlScN can reach 100-150 μC / cm. 2It far exceeds the remanent polarization of PZT materials under the same conditions, which is 25-35 μC / cm. 2 Therefore, AlScN thin films have a stronger application prospect in ferroelectrically controlled GaN HEMT devices.

[0049] Therefore, in this embodiment, AlScN material with a lower Sc doping concentration is grown as a barrier layer. Utilizing its larger piezoelectric susceptibility compared to AlGaN, a higher carrier density for 2DEG is generated at the AlScN / GaN heterojunction, thereby improving the electrical characteristics of the GaN HEMT device. To enhance its ability to control 2DEG at the AlGaN / GaN heterojunction, AlScN material with a higher Sc doping concentration is grown directly on the AlScN barrier layer as a ferroelectric control film. The AlScN ferroelectric film enhances the gate control of the HEMT and improves the 2DEG cutoff capability, thereby achieving an enhancement-mode operation of the GaN HEMT device, increasing device lifetime, and reducing power consumption. Simultaneously, this material, as a capping layer for the HEMT device, reduces gate leakage current and enhances the source-drain ohmic contact.

[0050] Please see Figure 1 , Figure 1 This is a schematic diagram of the structure of an enhancement-mode GaN HEMT device based on AlScN provided in an embodiment of the present invention. The enhancement-mode GaN HEMT device includes a substrate layer 1, a nucleation transition layer 2, a GaN buffer layer 3, a GaN channel layer 4, and an AlScN layer 5. 1- x Sc x N-barrier layer 5, Al 1-y Sc y N-cap layer 6, source 7, drain 8, and gate 9.

[0051] Among them, substrate layer 1, nucleation transition layer 2, GaN buffer layer 3, GaN channel layer 4, Al 1-x Sc x The N-barrier layers are stacked in sequence, with 15% ≤ x ≤ 25%. Al 1-y Sc y N-cap layer 6, source 7, and drain 8 are all located in Al. 1-x Sc x On the N-barrier layer 5, Al 1-y Sc y The N-cap layer 6 is located between the source 7 and the drain 8, and Al 1-y Sc y The end of the N-cap layer 6 is in contact with the source 7 and drain 8, y>30%, and the source 7 and drain 8 are separated and symmetrically distributed. The gate 9 is located at Al between the source 7 and drain 8. 1-y Sc y N-hat layer 6 on top.

[0052] In this embodiment, Al 1-y Sc y The Sc doping concentration in the N-cap layer 6 must be greater than that in Al. 1-x Sc x Sc doping concentration in N-barrier layer 5.

[0053] Specifically, on the one hand, when the Sc content in AlScN is >30%, it exhibits significant ferroelectric properties. Using its ferroelectric polarization characteristics as a cap layer, and leveraging the flexible and tunable nature of its ferroelectric domain structure, it is possible to introduce flexible, reversible, and non-volatile control of HEMT devices based on the gate-controlled 2DEG concentration. If the Sc content is low, AlScN exhibits piezoelectric properties, making this impossible. Therefore, this embodiment uses AlScN with a doping concentration greater than 30%. 1-y Sc y Nitrogen (N) is used as the cap layer. On the other hand, when the Sc content is below 25%, AlScN mainly exhibits good piezoelectric properties. Under this composition condition, the piezoelectric coefficient of this material is larger than that of AlGaN. Using AlScN with a Sc doping concentration between 15% and 25% as a barrier layer can effectively increase the carrier concentration of 2DEG at the AlScN / GaN interface of HEMT devices, thereby improving the drain current of HEMT. Furthermore, if the Sc concentration in the AlScN barrier layer is chosen to be relatively large, the HEMT device will form a ferroelectric / GaN MFS structure. Although this heterostructure will have a higher concentration of 2DEG, it is difficult to form an ideal interface when directly growing the ferroelectric / GaN heterostructure. It is also difficult to achieve perfect quality when growing an epitaxial layer with good ferroelectric properties on GaN. This is because large interface scattering and interface state density exist at the interface, which will destroy the carrier transport characteristics. In addition, because the ferroelectric / GaN heterojunction will exhibit a very small band structure and the quantum confinement effect is not strong, there may be diffused carriers in the ferroelectric layer, which may cause the electrical characteristics of the HEMT device to decrease rather than improve.

[0054] Furthermore, this embodiment can utilize Al 1-y Sc y The ferroelectricity of the N-cap layer enables enhancement-mode GaN HEMT devices.

[0055] Specifically, in practical applications, if used as a switching device, for system safety, the channel needs to remain off when no gate voltage is applied. However, considering power consumption in actual circuits, depletion-type devices require an additional voltage to the gate to turn off. Enhancement-type devices, on the other hand, do not require an additional voltage to turn off. Therefore, considering system safety, power consumption, and circuit design simplification in practical applications, fabricating enhancement-type devices is essential. And Al... 1-ySc y N-cap layer deposited on Al 1-x Sc x After N / GaN surface, in ferroelectric / Al 1-x Sc x The ferroelectric polarization charge at the N interface modulates the Al below. 1-x Sc x The energy band structure of the N / GaN heterojunction affects the ferroelectric / Al... 1-x Sc x The overall charge distribution of N / GaN; by applying external electric fields of different magnitudes, the direction of ferroelectric polarization charges and the intensity of ferroelectric polarization can be controlled, thereby increasing or decreasing the 2DEG density in the channel. The stronger the ferroelectric polarization characteristics of the ferroelectric material, the greater the adjustable range and control capability of the device for the 2DEG density; the heterojunction channel is more likely to achieve full depletion under the ferroelectric control of AlScN, thus preventing the formation of quantum wells; when the gate bias is zero, the channel is depleted and in a closed state, requiring a positive bias to turn the channel on, achieving the enhancement-mode characteristics of the device.

[0056] Therefore, this embodiment uses an Al layer with a Sc doping concentration greater than 30%. 1-y Sc y Nitrogen ferroelectric thin films are used as capping materials for GaNHEMT devices, with Al doping concentrations of 15%–25%. 1-x Sc x With N as a barrier layer, the AlScN films with different Sc doping concentrations have good lattice matching at the interface. They can generate a higher concentration of 2DEG at the heterojunction through piezoelectric polarization, increasing the drain current of the HEMT device, and can also perform non-volatile modulation of the HEMT through ferroelectric polarization, changing the threshold voltage from negative to positive, realizing an enhancement-mode HEMT device. At the same time, they reduce drain current collapse and significantly improve the electrical performance of the device.

[0057] This embodiment uses AlN as the nucleation transition layer of GaN HEMT, which solves the lattice mismatch problem between the substrate and the GaN buffer layer and reduces the interfacial tension caused by this mismatch. At the same time, it can reduce the current collapse caused by interfacial mismatch, defects or trap effects and reduce static current leakage.

[0058] In one specific embodiment, the substrate layer 1 is made of silicon single crystal, such as silicon 111 single crystal; the nucleation transition layer 2 is made of AlN with a thickness of 40-60 nm; the GaN buffer layer 3 is made of C-doped GaN with a thickness of 600-1500 nm; and the GaN channel layer 4 has a thickness of 100-300 nm. 1-x Sc x The thickness of the N-barrier layer 5 is 15-35 nm; Al 1-ySc y The thickness of the N-cap layer 6 is 5-10nm; the thickness of the source 7 and drain 8 is 320nm, and the thickness of the gate 9 is 150nm.

[0059] In one specific embodiment, Al 1-x Sc x The Sc doping concentration in the N-barrier layer 5 is 25%, and Al 1-y Sc y The Sc doping concentration in the N-cap layer 6 is 40%.

[0060] In summary, the GaN HEMT device of this embodiment has the following advantages: it uses Al with a doping concentration γ greater than 30%. 1- y Sc y Using N as the cap layer strengthens the 2DEG modulation of GaN HEMTs, making it easier to achieve the enhancement-mode operation of HEMTs; using Al 1-y Sc y As a cap layer structure in GaN HEMT, N prevents Al from being deposited. 1-x Sc x Oxidation of the N-type barrier layer surface can reduce the probability of external channel electrons tunneling to the surface, thereby suppressing current collapse; Al with a Sc doping concentration greater than 30% 1-y Sc y The N-cap layer is grown on Al with a Sc doping concentration of 15%–25%. 1-x Sc x Above the N-barrier layer, the lattice is perfectly matched, resulting in better thin film crystallization quality and better preservation of its ferroelectric properties.

[0061] Example 2

[0062] Based on Example 1, please refer to Figure 2 , Figure 2 This is a schematic diagram illustrating a method for fabricating an enhanced GaN HEMT device based on AlScN, provided in an embodiment of the present invention. The fabrication method includes the following steps:

[0063] S1. A nucleation transition layer 2 is prepared on substrate layer 1.

[0064] S2. Prepare a GaN buffer layer 3 on the nucleation transition layer 2.

[0065] S3. Prepare a GaN channel layer 4 on the GaN buffer layer 3.

[0066] S4. Al was prepared on GaN channel layer 4 using organometallic chemical vapor deposition. 1-x Sc x N is a barrier layer 5, where 15% ≤ x ≤ 25%.

[0067] S5. Using magnetron sputtering or atomic layer deposition (ALD) processes, on Al... 1-x Sc x N-barrier layer 5 is prepared Al 1-y Sc y N-hat layer 6, where y > 30%.

[0068] S6, in Al 1-x Sc x A source electrode 7 is fabricated at one end of the N-barrier layer 5, and a drain electrode 8 is fabricated at the other end, such that the source electrode 7 and the drain electrode 8 are separated from each other and symmetrically distributed, and Al 1-y Sc y The N-cap layer 6 is located between the source 7 and the drain 8, while Al 1-y Sc y The end of the N-cap layer 6 is in contact with the source electrode 7 and the drain electrode 8.

[0069] S7, in Al 1-y Sc y A gate 9 is fabricated on the N-cap layer 6, such that the gate 9 is located between the source 7 and the drain 8.

[0070] With Al 1-x Sc x The Sc doping concentration in the N-barrier layer 5 is 25%, and Al 1-y Sc y Taking a Sc doping concentration of 40% in the N-cap layer 6 as an example, the preparation method specifically includes the following steps:

[0071] S1. A nucleation transition layer 2 is prepared on substrate layer 1.

[0072] First, the surface of the Si111 substrate 1 is pretreated. Specifically, the Si111 substrate 1 is fixed in a cleaning rack for cleaning. First, the sample is ultrasonically cleaned in acetone for 5-10 minutes; then, the acetone-cleaned sample is ultrasonically cleaned in isopropanol for 5-10 minutes; finally, the isopropanol-cleaned sample is ultrasonically cleaned in deionized water for 3 minutes. After the above cleaning steps, oil stains and oxides and other impurities on the sample surface are removed. The Si substrate 1, after being cleaned with deionized water, is dried with a nitrogen gun for later use.

[0073] Then, an AlN nucleation transition layer 2 was grown on substrate 1 using magnetron sputtering. A pure aluminum (Al) metal target with a purity of 99.999% was used as the sputtering target. The sputtering temperature was 550℃, the chamber pressure was 5 mtorr, and sputtering growth was carried out at a sputtering power of 130 W for 10 min in an atmosphere with a gas flow ratio of 2:1 for high-purity nitrogen and argon, to obtain the AlN nucleation transition layer 2.

[0074] S2. Prepare a GaN buffer layer 3 on the nucleation transition layer 2.

[0075] Specifically, a C-doped GaN buffer layer was prepared using molecular beam epitaxy (MBE). The MBE equipment was set to a substrate temperature of 850°C, a plasma generator power of 450W, and a Ga source beam current of 5.6 × 10⁻⁶. - 8 Torr, C-source beam flux is 2.0*10 -8 Torr, nitrogen flow rate of 1 sccm, and stable growth under the above conditions for 3 hours to obtain C-doped GaN buffer layer.

[0076] S3. Prepare a GaN channel layer 4 on the GaN buffer layer 3.

[0077] Specifically, GaN channel layer 4 was grown using MBE. The process parameters were set as follows: substrate temperature 850℃, plasma generator power 450W, and Ga source beam current 5.6*10⁻⁶. -8 Torr, nitrogen flow rate of 1 sccm, and stable growth under the above conditions for 1.5 h to obtain GaN channel layer.

[0078] S4. Al was prepared on GaN channel layer 4 using organometallic chemical vapor deposition. 1-x Sc x N-barrier layer 5.

[0079] Specifically, using Metal-organic Chemical Vapor Deposition (MOCVD), Al with a Sc doping concentration of 25% was grown. 0.75 Sc 0.25 N-barrier layer 5. The substrate temperature in the organometallic chemical vapor deposition (HCVD) apparatus was maintained at 1200℃, the pressure was set to 60 Torr, and NH3, TMAl, and Cp3Sc were used as the reaction sources, with H2 as the carrier gas. The molar flow rates of TMAl, NH3, and Cp3Sc were set to 11.5 μmol / min, 0.165 mol / min, and 5.5 μmol / min, respectively. The growth time was 10 min, yielding Al... 0.75 Sc 0.25 N-barrier layer 5.

[0080] This embodiment uses Al with a Sc doping concentration of 25%. 0.75 Sc 0.25 Using N as the barrier layer of GaN HEMT devices, and taking advantage of its high spontaneous polarization and piezoelectric polarization characteristics, a high concentration of 2DEG is formed at the AlScN / GaN heterojunction, thereby increasing the drain current of GaN HEMT.

[0081] This embodiment uses metal-organic chemical vapor deposition to grow Al. 1-x Sc x The N-barrier layer can guarantee Al 1-x Sc x Nitrogen materials can be grown with high quality, and their piezoelectric polarization characteristics, which are far superior to those of AlGaN, enable Al... 1-x Sc x The 2DEG carrier density formed at the N / GaN heterojunction is significantly increased compared to that at the AlGaN / GaN heterojunction, thereby improving transconductance and drain current, giving GaN HEMTs excellent device characteristics.

[0082] S5. Using magnetron sputtering or atomic layer deposition (ALD) processes, on Al... 1-x Sc x N-barrier layer 5 is prepared Al 1-y Sc y N-hat layer 6.

[0083] Specifically, Al with a Sc doping concentration of 40% was grown using magnetron sputtering. 0.6 Sc 0.4 N-cap layer 6. Pure aluminum (Al) metal targets with a purity of 99.999% and pure scandium (Sc) metal targets with a purity of 99.99% were used as sputtering targets for AlScN thin films. The sample was placed in a magnetron sputtering PC chamber. After evacuating the chamber to a vacuum level of 1E-6 Torr, the chamber gas pressure was set to 10 mtorr. Once the gas pressure stabilized, the sputtering power of both targets was set to 50 W, and pre-sputtering was performed for 10 min to allow the Al and Sc targets to stabilize and glow. After pre-sputtering, the chamber gas was adjusted to a nitrogen flow rate of 20 sccm, with a high-purity nitrogen to high-purity argon gas flow rate ratio of 2:1. The Sc concentration of AlScN was controlled by changing the sputtering power of the pure aluminum and pure scandium metal targets. The sputtering power of the Al target was set to 600 W, and the sputtering power of the Sc target was set to 400 W, with a sputtering time of 3 min, to prepare AlScN thin films with good grain quality. 0.6 Sc 0.4 N-hat layer.

[0084] This embodiment uses Al with a Sc doping concentration of 40%. 0.6 Sc 0.4 Nitrogen ferroelectric thin films are used as capping layers for GaN HEMT devices. Their ferroelectric polarization characteristics are used to control the 2DEG concentration of HEMT devices, thereby improving the gate control capability of transistors and realizing the enhancement mode of GaN HEMT.

[0085] The preparation method of this invention uses magnetron sputtering to prepare Al 1-y Sc yThe N-hat layer has a simple and easy-to-operate process, a short production cycle, and low cost, making it suitable for large-scale production environments.

[0086] It should be noted that materials grown using metal-organic chemical vapor deposition tend to have better quality, due to the presence of Al. 1-x Sc x The N-barrier layer is grown on GaN, and Al 1-x Sc x The lattice matching degrees of N and GaN overlap, therefore, the MOCVD method is used to grow Al. 1-x Sc x N-barrier layer; while magnetron sputtering is more convenient to operate and faster to prepare, because Al 1-x Sc x N-barrier layer and Al 1-y Sc y The N-cap layer is made of the same material, and the lattice itself is well-matched, so Al is grown using magnetron sputtering. 1-y Sc y N-hat layer.

[0087] S6, in Al 1-x Sc x A source electrode 7 is fabricated at one end of the N-barrier layer 5, and a drain electrode 8 is fabricated at the other end, such that the source electrode 7 and the drain electrode 8 are separated from each other and symmetrically distributed, and Al 1-y Sc y The N-cap layer 6 is located between the source 7 and the drain 8, while Al 1-y Sc y The end of the N-cap layer 6 is in contact with the source electrode 7 and the drain electrode 8.

[0088] Specifically, in Al 0.6 Sc 0.4 The two ends of the N-cap layer are photolithographically lithographically and etched using standard photolithography processes to remove the Al at both ends. 0.6 Sc 0.4 N ferroelectric thin films were then used in the device Al. 0.75 Sc 0.25 Four layers of metal electrodes, Ti / Al / Ni / Au, were deposited at position 5 of the N-barrier layer, with thicknesses of 20 nm, 150 nm, 50 nm, and 100 nm, respectively. The deposited sample was then placed in a high-temperature annealing furnace and rapidly annealed in an N2 atmosphere at 800 °C for 30 s to form the source electrode 7 and the drain electrode 8.

[0089] S7, in Al 1-y Sc y A gate 9 is fabricated on the N-cap layer 6, such that the gate 9 is located between the source 7 and the drain 8.

[0090] Specifically, electron beam evaporation technology is used in Al 0.6 Sc0.4 Ni / Au bilayer metals with thicknesses of 50 nm and 100 nm are deposited sequentially at the center of the N-cap layer, and then rapidly thermally annealed in an N2 atmosphere at 700 °C for 1 min to form the gate, thus completing the fabrication of the GaN HEMT device.

[0091] The fabrication method in this embodiment is simple and easy to operate. The AlScN cap layer and AlScN barrier layer with different Sc compositions have good lattice matching, resulting in high film quality and low production cost. It is not only applicable to existing HEMT fabrication processes, but also requires a short process time. It can significantly reduce costs while optimizing device performance, making it highly feasible and enabling the fabrication of HEMT devices to be more operable and suitable for large-scale production environments.

[0092] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. An enhancement-mode GaN HEMT device based on AlScN, characterized in that, include: substrate layer (1), nucleation transition layer (2), GaN buffer layer (3), GaN channel layer (4), Al 1-x Sc x N barrier layer (5), Al 1-y Sc y N cap layer (6), source (7), drain (8) and gate (9), wherein, The substrate layer (1), the nucleation transition layer (2), the GaN buffer layer (3), the GaN channel layer (4), and the Al 1-x Sc x N-barrier layers (5) are stacked sequentially, with 15% ≤ x ≤ 25%; The Al 1-y Sc y The N-cap layer (6), the source (7), and the drain (8) are all located in the Al 1-x Sc x On the N-barrier layer (5), the Al 1-y Sc y The N-cap layer (6) is located between the source (7) and the drain (8), and the Al 1-y Sc y The end of the N-cap layer (6) is in contact with the source (7) and the drain (8), y>30%, and the source (7) and the drain (8) are separated from each other and symmetrically distributed; The gate (9) is located between the source (7) and the drain (8) of the Al 1-y Sc y N cap layer (6).

2. The AlScN-based enhancement-mode GaN HEMT device of claim 1, wherein, The substrate layer (1) is made of silicon single crystal; The nucleation transition layer (2) is made of AlN and has a thickness of 40-60 nm. The material of the GaN buffer layer (3) includes C-doped GaN with a thickness of 600-1500 nm; The thickness of the GaN channel layer (4) is 100-300 nm; Al 1-x Sc x The thickness of the N-barrier layer (5) is 15-35 nm; Al 1-y Sc y The thickness of the N-hat layer (6) is 5-10 nm; The thickness of the source (7) and the drain (8) is 320 nm, and the thickness of the gate (9) is 150 nm.

3. The AlScN-based enhancement-mode GaN HEMT device of claim 1, wherein, The Al 1-x Sc x The Sc doping concentration in the N barrier layer (5) is 25%.

4. The AlScN-based enhancement-mode GaN HEMT device of claim 1, wherein, The Al 1-y Sc y The Sc doping concentration in the N-hat layer (6) is 40%.

5. A method of fabricating an AlScN-based enhanced GaN HEMT device, characterized by, Including the following steps: A nucleation transition layer (2) is prepared on the substrate layer (1); A GaN buffer layer (3) is prepared on the nucleation transition layer (2); A GaN channel layer (4) is prepared on the GaN buffer layer (3); Al was prepared on the GaN channel layer (4) using an organometallic chemical vapor deposition method. 1-x Sc x N-barrier layer (5), where 15% ≤ x ≤ 25%; Using magnetron sputtering or atomic layer deposition, on the Al 1-x Sc x N-barrier layer (5) preparation of Al 1-y Sc y N-cap layer (6), where y > 30%; In the Al 1-x Sc x A source electrode (7) is fabricated at one end of the N-barrier layer (5), and a drain electrode (8) is fabricated at the other end, such that the source electrode (7) and the drain electrode (8) are separated from each other and symmetrically distributed, and Al 1-y Sc y The N-cap layer (6) is located between the source (7) and the drain (8), while the Al 1-y Sc y The end of the N-cap layer (6) is in contact with the source electrode (7) and the drain electrode (8); In the Al 1-y Sc y A gate (9) is prepared on the N cap layer (6), so that the gate (9) is located between the source (7) and the drain (8).

6. The method for fabricating an enhanced GaN HEMT device based on AlScN according to claim 5, characterized in that, An AlGaN barrier layer (3) is formed on the GaN channel layer (4) by a metal organic chemical vapor deposition method. 1-x Sc x A N barrier layer (5) comprises: The substrate temperature in the organometallic chemical vapor deposition (HCV) apparatus was maintained at 1200°C, the pressure was set to 60 Torr, and NH3, TMAl, and Cp3Sc were used as the reaction sources, with H2 as the carrier gas. The molar flow rates of TMAl, NH3, and Cp3Sc were set to 11.5 μmol / min, 0.165 mol / min, and 5.5 μmol / min, respectively. The growth time was 10 min, and the Al was prepared. 1-x Sc x N-barrier layer (5).

7. The method for fabricating an enhanced GaN HEMT device based on AlScN according to claim 6, characterized in that, The Al 1-x Sc x The Sc doping concentration in the N barrier layer (5) is 25%.

8. The method for fabricating an enhanced GaN HEMT device based on AlScN according to claim 5, characterized in that, Using magnetron sputtering or atomic layer deposition, on the Al 1-x Sc x N-barrier layer (5) preparation of Al 1-y Sc y N-hat layer (6), including: Using magnetron sputtering, pure aluminum metal targets with a purity of 99.999% and pure scandium metal targets with a purity of 99.99% were used as sputtering targets for AlScN thin films. The vacuum degree of the PC chamber was 1E-6 Torr, the gas pressure in the chamber was 10 mtorr, the sputtering power of the two targets was 50 W, and the pre-sputtering time was 10 min. After pre-sputtering, the nitrogen flow rate was adjusted to 20 sccm, and the nitrogen to argon gas flow ratio was 2:

1. The sputtering power of the pure aluminum metal target and the pure scandium metal target was adjusted to control the Al sputtering power. 1-y Sc y The Sc concentration in the N-cap layer (6) was adjusted, and the sputtering time was 3 min to prepare Al. 1-y Sc y N-cap layer (6).

9. The method of fabricating an AlScN-based enhancement-mode GaN HEMT device according to claim 8, wherein, The Al 1-y Sc y The Sc doping concentration in the N-hat layer (6) is 40%.

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