CN109742144B - Groove gate enhanced MISHEMT device and manufacturing method thereof - Google Patents

Abstract

The invention discloses a trench gate enhancement type MISHEMT device, comprising a substrate; a SiN nucleation layer that is heteroepitaxially grown on the substrate; a GaN buffer layer that is epitaxially grown on the SiN nucleation layer; AlGaN back barrier layer epitaxially grown on the GaN buffer layer; GaN channel layer epitaxially grown on the AlGaN back barrier layer; AlGaN barrier layer epitaxially grown on the GaN channel layer; A first AlGaN modulation layer epitaxially grown on the AlGaN barrier layer; a second AlGaN modulation layer epitaxially grown on the first AlGaN modulation layer; a recessed gate groove is etched in the middle of the second AlGaN modulation layer, and the recessed gate An Al ₂ O ₃ insulating layer is deposited on the surface of the groove, and the device of the present invention is beneficial in that the breakdown voltage is increased, the threshold voltage is increased and the saturation current density is increased.

Description

A trench gate enhanced MISHEMT device and method of making the same

technical field

The invention relates to the technical field of AlGaN/GaN heterojunction field effect transistors, in particular to a trench gate enhancement type MISHEMT device and a manufacturing method thereof.

Background technique

Compared with the traditional first-generation semiconductors Ge, Si and the second-generation semiconductor materials GaAs, InP and other materials, GaN-based semiconductors have the advantages of large band gap, high breakdown electric field, high electron saturation migration speed, and easy formation of heterostructures. It has excellent properties such as strong spontaneous and piezoelectric polarization effects, strong radiation resistance and good chemical stability. GaN can form a heterojunction with nitride semiconductor materials such as AlGaN and InAlN. During epitaxial growth, the discontinuity of the energy band and the spontaneous polarization and piezoelectric polarization at the interface of the heterojunction can be generated at the interface of the heterojunction. High concentration of two-dimensional electron gas (2DEG). The output power density of GaN-based power devices is 10 times that of GaAs-based power devices. Under the same size, the output power of GaN-based power devices can be made larger, thereby significantly reducing the weight of the device and reducing The number of system components improves the reliability of the system. At the same time, GaN-based devices have a higher working voltage and can work at 42V. The operating frequency of GaN-based power devices can cover the frequency range of 1 to 100 GHz. Therefore, GaN materials are especially suitable for the preparation of high-temperature, high-frequency, high-power and radiation-resistant new-generation microwave power HEMT devices and high-voltage low-loss HEMT electronic power devices, which have broad and special application prospects.

Due to the strong polarization effect of the AlGaN/GaN heterojunction, a high concentration of two-dimensional electron gas conduction channel will be generated at the heterointerface, so the traditional AlGaN/GaN HEMT device is a normally-on device, and the threshold voltage of the device is is a negative value. However, in the circuit application process of normally-on devices, the device can only be turned off when a negative voltage is applied to the gate of the device, which not only increases the extra power consumption of the system, but also is easily affected by noise signals in the circuit, resulting in false turn-on. problem, which reduces the security of the system. Therefore, it is of great significance to study high-performance enhancement-mode AlGaN/GaN HEMTs.

At present, the implementation methods of enhancement mode GaN HEMT devices include: p-type gate, F ion implantation, recessed gate trench, thin barrier layer and other technologies. The threshold voltage and gate voltage range of the device obtained by adding p-type gate are small, which brings problems to the packaging of the transistor; although the process of F ion implantation is simple, there are problems such as unstable threshold voltage and poor reliability; The barrier layer achieves the purpose of enhancement at the expense of the two-dimensional electron gas concentration in all regions, and the device performance is degraded. The recessed gate trench technology only etches the barrier layer under the gate to a certain depth, so that the removed barrier layer becomes thinner and the concentration of two-dimensional electron gas is reduced, so as to achieve the purpose of enhancement. The thickness of the barrier layer between the region and the gate-drain region does not change, and the larger value of the carrier concentration remains unchanged, ensuring a certain current density. Therefore, the use of the trench gate structure to realize the enhancement mode GaN HEMT device has been widely used.

During the etching process of the gate trench, in order to control the gate level leakage, usually after the groove is etched, a layer of dielectric is deposited to form a metal-dielectric-semiconductor (MIS) structure. This not only improves the gate leakage of the recessed gate trench AlGaN/GaN HEMT device, but also increases the gate voltage swing.

When fabricating the trench gate, in order to deplete the two-dimensional electron gas under the gate, the method adopted is to increase the etching depth. However, since the AlGaN/GaN HEMT epitaxial structure is multi-layered, the materials of each layer are different, so the etching rate is also different, and it is difficult to control the depth of the recessed gate groove through the etching time. Large damage will cause instability of the threshold voltage V _th and increase the leakage current of the device. Therefore, it is necessary to propose a new structure to solve the above problems.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a trench gate enhanced MISHEMT device and a manufacturing method thereof in order to overcome the above deficiencies in the prior art.

The object of the present invention is achieved through the following technical solutions:

A trench gate enhancement type MISHEMT device, comprising:

substrate;

a SiN nucleation layer heteroepitaxially grown on the substrate;

a GaN buffer layer epitaxially grown on the SiN nucleation layer;

an AlGaN back barrier layer epitaxially grown on the GaN buffer layer;

a GaN channel layer epitaxially grown on the AlGaN back barrier layer;

an AlGaN barrier layer epitaxially grown on the GaN channel layer;

a first AlGaN modulation layer epitaxially grown on the AlGaN barrier layer;

A second AlGaN modulation layer epitaxially grown on the first AlGaN modulation layer; a recessed gate groove is etched in the middle of the second AlGaN modulation layer, and an Al ₂ O ₃ insulating layer is deposited on the surface of the recessed gate groove, and the The inner cavity of the recessed gate trench is filled with a metal electrode, and the metal electrode serves as a gate; the surfaces on both sides of the second AlGaN modulation layer form ohmic contacts, which are respectively used as a source electrode and a drain electrode; wherein, the first AlGaN modulation layer The AlGaN barrier layer and the GaN channel layer constitute the first double heterojunction, and the AlGaN barrier layer, the GaN channel layer and the AlGaN back barrier layer constitute the second double heterojunction.

Preferably, the Al content in the AlGaN back barrier layer is lower than that in the AlGaN barrier layer; the Al content in the first AlGaN modulation layer is lower than the Al content in the AlGaN barrier layer, and the second AlGaN The Al content in the modulation layer is higher than that in the AlGaN barrier layer.

Preferably, the thickness of the AlGaN back barrier layer is 20 nm; the thickness of the first AlGaN modulation layer is 10 nm; and the thickness of the second AlGaN modulation layer is 25 nm.

Preferably, the width of the recessed gate groove etched in the middle of the second AlGaN modulation layer is 1 μm, and the depth of the recessed gate groove is 30 nm; the thickness of the Al ₂ O ₃ insulating layer is 0.1 μm, and the length of the gate is 0.8 μm.

Preferably, both the source and drain lengths are 1 μm.

Preferably, the epitaxially grown GaN buffer layer has n-type resistance characteristics or semi-insulating characteristics.

Preferably, the material of the substrate is any one of silicon, silicon carbide, gallium nitride or sapphire.

The fabrication method of the above-mentioned trench gate enhanced MISHEMT device includes:

(1) Cleaning the semi-insulating substrate and removing surface contaminants;

(2) Epitaxially growing a 40nm thick SiN nucleation layer on a semi-insulating substrate by MOCVD technology;

(3) Epitaxial 3μm GaN buffer layer on the SiN nucleation layer;

(4) Epitaxial growth of a 20nm thick AlGaN back barrier layer on the GaN buffer layer, during the film growth process, the Al content in the AlGaN back barrier layer is controlled to be 7%;

(5) Epitaxially growing a 15nm thick GaN channel layer on the AlGaN back barrier layer;

(6) A 10nm-thick AlGaN barrier layer, a 10nm-thick first AlGaN modulation layer, and a 25nm-thick second AlGaN modulation layer were epitaxially grown in sequence on the GaN channel layer, and the content of Al was controlled to be 15%, 7%, 25%;

(7) adopting ICP etching method on the second AlGaN modulation layer to isolate the mesa to form the isolation of the active region;

(8) depositing Ti/Al/Ni/Au multilayer metal on the surfaces of both sides of the second AlGaN modulation layer by means of electron beam evaporation, and after the lift-off process, rapidly annealing the two sides of the second AlGaN modulation layer 1 μm long source and drain are formed on the side;

(9) photolithography is performed between the drain and source to make a concave gate groove, and a 30nm thick, 1 μm wide gate groove is etched by ICP etching technology;

(10) depositing Al ₂ O ₃ with a thickness of 0.1 μm as a gate dielectric by means of ALD deposition;

(11) depositing a gate metal by means of magnetron sputtering and combining with a lift-off process, and depositing the gate metal on the surface of the Al ₂ O ₃ gate dielectric;

(12) The final surface passivation is performed on the double modulation layer AlGaN/GaN/AlGaN MISHEMT device formed in steps (1)-(11) to form electrode pads, and finally a trench gate enhancement type MISHEMT that can be electrically tested is obtained device.

Compared with the prior art, the present invention has the following advantages:

- The threshold voltage increases, and the double heterojunction structure is introduced into the recessed gate trench structure. Since the double heterostructure itself has a small two-dimensional electron gas, it only needs to etch a small depth to make the device When the enhancement mode is reached, the threshold voltage increases.

2. The breakdown voltage is increased. In the double heterojunction structure composed of the first AlGaN modulation layer, the second AlGaN barrier layer, and the GaN channel layer, the concentration of the two-dimensional electron gas decreases due to the generation of two-dimensional hole gas. ; Double heterojunction structure composed of AlGaN back barrier layer, GaN channel layer and AlGaN barrier layer, due to the existence of AlGaN back barrier, the two-dimensional electron gas is confined in the quantum well. The reduction of the two-dimensional electron gas makes the buffer current of the device in the off-state smaller and the breakdown voltage increases.

3. The saturation current density increases, and the Al content in the second AlGaN modulation layer is relatively high, so that the difference between the lattice constant of the second AlGaN modulation layer and the GaN barrier layer becomes larger, and the piezoelectric polarization charges generated by the two As the density increases, the concentration of the two-dimensional electron gas increases, so that the saturation current density of the device increases.

Description of drawings

FIG. 1 is a schematic structural diagram of a trench gate enhancement type MISHEMT device of the present invention.

FIG. 2 is a schematic structural diagram of a conventional AlGaN/GaN MISHEMT device.

FIG. 3 is a schematic structural diagram of an AlGaN/GaN/AlGaN MISHEMT device containing only a back barrier layer.

FIG. 4 is a comparison diagram of the transfer characteristic curves of the three devices of FIG. 1 , FIG. 2 and FIG. 3 .

Detailed ways

The present invention will be further described below with reference to the accompanying drawings and embodiments.

Referring to FIG. 1, a trench gate enhancement MISHEMT device includes:

substrate 1;

A SiN nucleation layer 2 that is heteroepitaxially grown on the substrate 1;

A GaN buffer layer 3 epitaxially grown on the SiN nucleation layer 2;

AlGaN back barrier layer 4 epitaxially grown on the GaN buffer layer 3;

a GaN channel layer 5 epitaxially grown on the AlGaN back barrier layer 4;

AlGaN barrier layer 6 epitaxially grown on the GaN channel layer 5;

a first AlGaN modulation layer 7 epitaxially grown on the AlGaN barrier layer 6;

a second AlGaN modulation layer 8 epitaxially grown on the first AlGaN modulation layer 7;

The middle of the second AlGaN modulation layer 8 is etched with a concave gate groove, an Al ₂ O ₃ insulating layer 9 is deposited on the surface of the concave gate groove, and the inner cavity of the concave gate groove is filled with metal electrodes, and the metal electrodes serve as Gate 10; the surfaces on both sides of the second AlGaN modulation layer form ohmic contacts, respectively serving as source 11 and drain 12; wherein, the first AlGaN modulation layer 7, the AlGaN barrier layer 6, and the GaN channel layer 5 The first double heterojunction is constituted, and the AlGaN barrier layer 6 , the GaN channel layer 5 , and the AlGaN back barrier layer 4 constitute the second double heterojunction. The scheme connects the recessed gate trench structure with the double heterojunction structure, increases the threshold voltage, increases the saturation current density, increases the breakdown voltage of the device, and improves the performance of the device.

In this embodiment, the MISHEMT device is a trench gate enhanced ALGAN/GAN/ALGAN MISHEMT device. The surfaces on both sides of the second AlGaN modulation layer after ohmic contact are formed, respectively, as the source electrode 11 and the drain electrode 12; The right side of the second AlGaN modulation layer serves as the drain electrode 12 . The ohmic contact between the metal and the semiconductor means that there is a pure resistance at the contact, and the smaller the resistance, the better, so that when the component operates, most of the voltage drop is in the active region and not on the contact surface. Therefore, its I-V characteristic is a linear relationship. The larger the slope, the smaller the contact resistance. The size of the contact resistance directly affects the performance index of the device. Ohmic contact is widely used in metal processing, and the main measures to achieve it are to carry out high doping in the semiconductor surface layer or introduce a large number of recombination centers.

In this embodiment, the Al content in the AlGaN back barrier layer 4 is lower than the Al content in the AlGaN barrier layer 6 ; the Al content in the first AlGaN modulation layer 7 is lower than that in the AlGaN barrier layer 6 The content of Al in the second AlGaN modulation layer 8 is higher than that in the AlGaN barrier layer 6 .

In this embodiment, the thickness of the AlGaN back barrier layer 4 is 20 nm; the thickness of the first AlGaN modulation layer 7 is 10 nm; the thickness of the second AlGaN modulation layer 8 is 25 nm.

In this embodiment, the width of the recessed gate trench etched in the middle of the second AlGaN modulation layer 8 is 1 μm, and the depth of the recessed gate trench is 30 nm; the thickness of the Al ₂ O ₃ insulating layer 9 is 0.1 μm, and the length of the gate 10 is 0.8μm.

In this embodiment, the lengths of the source electrode 11 and the drain electrode 12 are both 1 μm.

In this embodiment, the epitaxially grown GaN buffer layer 3 has n-type resistance characteristics or semi-insulating characteristics.

In this embodiment, the material of the substrate 1 is any one of silicon, silicon carbide, gallium nitride or sapphire.

The fabrication method of the above-mentioned trench gate enhanced MISHEMT device includes:

(1) cleaning the semi-insulating substrate 1 and removing surface contaminants;

(2) epitaxially growing a 40nm thick SiN nucleation layer 2 on the semi-insulating substrate 1 by MOCVD technology;

(3) GaN buffer layer 3 epitaxially 3 μm on SiN nucleation layer 2;

(4) Epitaxially growing an AlGaN back barrier layer 4 with a thickness of 20 nm on the GaN buffer layer 3, and controlling the Al content in the AlGaN back barrier layer 4 to be 7% during the film growth process;

(5) epitaxially growing a 15 nm thick GaN channel layer 5 on the AlGaN back barrier layer 4;

(6) A 10 nm-thick AlGaN barrier layer 6, a 10-nm-thick first AlGaN modulation layer 7, and a 25-nm-thick second AlGaN modulation layer 8 are sequentially epitaxially grown on the GaN channel layer, and the content of Al is controlled to be 15%, 7%, 25%;

(7) on the second AlGaN modulation layer 8, the ICP etching method is used to isolate the mesa to form the isolation of the active region;

(8) Depositing Ti/Al/Ni/Au multilayer metal on the surfaces of both sides of the second AlGaN modulation layer 8 by means of electron beam evaporation, and then rapidly annealing the second AlGaN modulation layer 8 after a lift-off process 1 μm long source electrode 11 and drain electrode 12 are formed on both sides;

(9) photolithography is performed between the drain and source to make a concave gate groove, and a 30nm thick, 1 μm wide gate groove is etched by ICP etching technology;

(10) depositing Al ₂ O ₃ with a thickness of 0.1 μm as a gate dielectric by means of ALD deposition;

(11) depositing a gate metal by means of magnetron sputtering and combining with a lift-off process, and depositing the gate metal on the surface of the Al ₂ O ₃ gate dielectric;

(12) The final surface passivation is performed on the double modulation layer AlGaN/GaN/AlGaN MISHEMT device formed in steps (1)-(11) to form electrode pads, and finally a trench gate enhancement type MISHEMT that can be electrically tested is obtained device.

The trench gate enhancement mode MISHEMT device (as shown in Figure 1) prepared above is respectively compared with the traditional AlGaN/GaN MISHEMT device (as shown in Figure 2) and the AlGaN/GaN/AlGaN MISHEMT device containing only the back barrier layer (as shown in Figure 2). 3) The threshold voltage and saturated output current are compared, and the results are shown in Figure 4; the results in Figure 4 show that the new trench-gate enhancement MISHEMT device with dual modulation layers has a higher threshold voltage than the other two. species is the largest, and the saturation current density is greatly improved compared to the AlGaN/GaN/AlGaN MISHEMTs containing only the back barrier layer.

Due to the introduction of the double heterojunction, the device does not need to be etched to a large depth to reach the threshold voltage requirement, which reduces the problem of damage to the device caused by the unstable etching process and increases the voltage withstand capability of the device. The introduction of double heterojunction leads to the problem of reducing the current density. We adopt the method of adding an AlGaN modulation layer, which significantly increases the saturation current density of the device.

The principle of improving the threshold voltage and breakdown voltage of the trench gate enhancement MISHEMT device in this scheme is as follows:

The first double heterojunction is formed by the first AlGaN modulation layer 7 , the AlGaN barrier layer 6 and the GaN channel layer 5 . When the Al content of the first AlGaN modulation layer 7 is smaller than that of the AlGaN barrier layer 6 , the first double heterojunction is formed. A hole channel is formed at the interface between the AlGaN modulation layer 7 and the AlGaN barrier layer 6 because the valence band is higher than the Fermi potential, and finally a two-dimensional hole gas (2DHG) is formed. The presence of 2DHG can deplete the 2DEG at the interface between the first AlGaN modulation layer 7 and the AlGaN barrier layer 6 .

The second double heterojunction is formed by the AlGaN barrier layer 6, the GaN channel layer 5, and the AlGaN back barrier layer 4. Due to the existence of the AlGaN back barrier layer 4, the GaN channel layer is in a state of compressive strain, so that the crystal of GaN is in a state of compressive strain. The lattice constant becomes larger. As a result, the lattice constant difference between the AlGaN barrier layer 6 and the GaN channel layer 5 will become smaller, and the polarization charge density between them due to piezoelectric polarization will decrease; at the same time, because the AlGaN back barrier layer The existence of 4 makes a negative charge exist between the AlGaN barrier layer 6 and the GaN channel layer 5, which has a certain depletion effect on the two-dimensional electron gas, so that the conduction band of the GaN channel layer 5 is pulled up, and the potential barrier The depth is reduced, thereby reducing the concentration of the two-dimensional electron gas.

Due to the reduction of the two-dimensional electron gas concentration in the trench gate enhancement type MISHEMT device with double heterostructure, only a small etching depth is required to make the device reach the enhancement mode and the threshold voltage is increased. At the same time, the reduction of the two-dimensional electron gas concentration makes the buffer leakage current of the device smaller in the off state, the device is not easily broken down, and the withstand voltage performance is improved. When the voltage between the drain and the source of the device is large, the threshold voltage of the device changes very little, so that the device can work more stably. And because the two-dimensional electron gas is confined in the quantum well, the 2DEG is not easily overflowed into bulk electrons, which increases the mobility of the device and has a larger transconductance.

The two double heterojunctions of the above composition will reduce the concentration of the two-dimensional electron gas in the channel. In this way, when fabricating a trench gate enhancement transistor, only a lower depth can be etched, and the enhancement mode can be realized. It is easier to control and cause less damage to the device. In addition, the double heterojunction device has the advantages of strong voltage resistance, high stability, and high mobility. By connecting the recessed gate trench structure with the double heterojunction structure, the performance of the device will be greatly improved.

The principle that the saturation current density of the trench gate enhancement MISHEMT device of this scheme is improved is as follows:

Compared with the single heterojunction device, the trench-gate enhancement MISHEMT device with double heterojunction has a smaller two-dimensional electron gas concentration, so that the saturation current density of the device decreases. In order to solve this problem, a second AlGaN modulation layer 8 with a larger Al content is introduced on the first AlGaN modulation layer 7 . With the increase of Al content, the spontaneous polarization and piezoelectric polarization become larger, so that the concentration of the two-dimensional electron gas increases, and the saturation current concentration also increases accordingly.

The beneficial effects that the present invention has relative to the prior art are:

- The threshold voltage increases, and the double heterojunction structure is introduced into the recessed gate trench structure. Since the double heterostructure itself has a small two-dimensional electron gas, it only needs to etch a small depth to make the device When the enhancement mode is reached, the threshold voltage increases.

2. The breakdown voltage is increased. In the double heterojunction structure composed of the first AlGaN modulation layer 7, the second AlGaN barrier layer 6 and the GaN channel layer 5, the two-dimensional electron gas is generated due to the generation of two-dimensional hole gas. In the double heterojunction structure composed of AlGaN barrier layer 6, GaN channel layer 5, and AlGaN back barrier layer 4, due to the existence of AlGaN back barrier, the two-dimensional electron gas is confined in the quantum well. The reduction of the two-dimensional electron gas makes the buffer current of the device in the off-state smaller and the breakdown voltage increases.

3. The saturation current density increases, and the content of Al in the second AlGaN modulation layer 8 is relatively high, so that the difference between the lattice constant of the second AlGaN modulation layer 8 and the GaN barrier layer becomes larger, and the piezoelectric electrode generated by the two With the increase of the chemical charge density, the concentration of the two-dimensional electron gas increases, so that the saturation current density of the device increases.

The above-mentioned specific embodiments are the preferred embodiments of the present invention, and do not limit the present invention. Any other changes or other equivalent replacement methods that do not deviate from the technical solutions of the present invention are included in the protection scope of the present invention. within.

Claims (8)

1. A trench-gate enhanced MISHEMT device, comprising:

a substrate;

a SiN nucleating layer which is positioned on the substrate and is subjected to heteroepitaxial growth;

a GaN buffer layer epitaxially grown on the SiN nucleation layer;

an AlGaN back barrier layer epitaxially grown on the GaN buffer layer;

a GaN channel layer epitaxially grown on the AlGaN back barrier layer;

an AlGaN barrier layer epitaxially grown on the GaN channel layer;

the first AlGaN modulation layer is positioned on the AlGaN barrier layer and epitaxially grows;

a second AlGaN modulation layer epitaxially grown on the first AlGaN modulation layer;

a concave gate groove is etched in the middle of the second AlGaN modulation layer, and Al is deposited on the surface of the concave gate groove₂O₃Insulating layer of the recessed gate trenchThe inner cavity is filled with a metal electrode which is used as a grid; ohmic contacts are formed on the surfaces of the two sides of the second AlGaN modulation layer and are respectively used as a source electrode and a drain electrode;

the first AlGaN modulation layer, the AlGaN barrier layer and the GaN channel layer form a first double heterojunction, and the AlGaN barrier layer, the GaN channel layer and the AlGaN back barrier layer form a second double heterojunction;

the Al content in the first AlGaN modulation layer is lower than that in the AlGaN barrier layer, and the Al content in the second AlGaN modulation layer is higher than that in the AlGaN barrier layer;

for the first double heterojunction, when the Al content of the first AlGaN modulation layer is smaller than that of the AlGaN barrier layer, a Fermi potential is increased at the interface between the first AlGaN modulation layer and the AlGaN barrier layer due to the valence band to form a hole channel, and finally two-dimensional hole gas is formed;

for the second double heterojunction, the GaN channel layer is in a compressive strain state due to the existence of the AlGaN back barrier layer, so that the lattice constant of the GaN is increased; and meanwhile, negative charges which have depletion effect on the two-dimensional electron gas exist between the AlGaN barrier layer and the GaN channel layer.

2. The trench-gate enhancement mode MISHEMT device of claim 1, wherein said AlGaN back barrier layer has an Al content lower than that of said AlGaN barrier layer.

3. The trench-gate enhancement type MISHEMT device of claim 1, wherein said AlGaN back barrier layer has a thickness of 20 nm; the thickness of the first AlGaN modulation layer is 10 nm; the thickness of the second AlGaN modulation layer is 25 nm.

4. The trench-gate enhancement type MISHEMT device of claim 1, wherein said second AlGaN modulation layer has a trench width of 1 μm etched in the middle and a trench depth of 30 nm; al (Al)₂O₃The thickness of the insulating layer is 0.1 μm, and the length of the gate is 0.8 μm.

5. The trench-gate enhancement type MISHEMT device of claim 1, wherein each of said source and drain lengths is 1 μm.

6. The trench-gate enhancement type MISHEMT device of claim 1, wherein said epitaxially grown GaN buffer layer has n-type resistance characteristics or semi-insulating characteristics.

7. The trench-gate enhancement type MISHEMT device of claim 1, wherein said substrate is made of any one of silicon, silicon carbide, gallium nitride or sapphire.

8. The method for manufacturing a trench gate enhancement type MISHEMT device according to any one of claims 1 to 7, comprising:

(1) cleaning the semi-insulating substrate and removing surface pollutants;

(2) epitaxially growing a 40nm thick SiN nucleating layer on a semi-insulating substrate by MOCVD technology;

(3) a GaN buffer layer with the thickness of 3 mu m is extended on the SiN nucleating layer;

(4) epitaxially growing an AlGaN back barrier layer with the thickness of 20nm on the GaN buffer layer, and controlling the Al content in the AlGaN back barrier layer to be 7% in the process of film growth;

(5) epitaxially growing a GaN channel layer with the thickness of 15nm on the AlGaN back barrier layer;

(6) sequentially epitaxially growing an AlGaN barrier layer with the thickness of 10nm, a first AlGaN modulation layer with the thickness of 10nm and a second AlGaN modulation layer with the thickness of 25nm on the GaN channel layer, and respectively controlling the content of Al to be 15%, 7% and 25%;

(7) performing mesa isolation on the second AlGaN modulation layer by adopting an ICP (inductively coupled plasma) etching method to form isolation of an active region;

(8) depositing Ti/Al/Ni/Au multilayer metals on the surfaces of the two sides of the second AlGaN modulation layer in sequence by using an electron beam evaporation method, and quickly annealing to form a source electrode and a drain electrode which are 1 mu m long on the two sides of the second AlGaN modulation layer after a stripping process;

(9) photoetching between a drain and a source to manufacture a concave gate groove, and etching a gate groove with the thickness of 30nm and the width of 1 mu m by utilizing an ICP (inductively coupled plasma) etching technology;

(10) al2O3 with the thickness of 0.1 mu m is deposited as a gate dielectric by using an ALD (atomic layer deposition) deposition mode;

(11) preparing gate metal by using a magnetron sputtering mode deposition and a stripping process, and depositing the gate metal on the surface of the Al2O3 gate medium;

(12) and (3) performing final surface passivation on the groove gate enhanced MISHEMT device formed in the steps (1) to (11) to form an electrode pressure welding point, and finally manufacturing the groove gate enhanced MISHEMT device capable of being electrically tested.

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