Depletion mode GaN HEMT-based metal-semiconductor direct-current friction nano-generator

Abstract

The invention discloses a metal-semiconductor direct current friction nanometer generator based on a depletion mode u-GaN / AlGaN / AlN / GaN high electron mobility transistor. The generator comprises a titanium (Ti) metal friction layer and a depletion mode GaN HEMT friction layer, and direct current is generated through the interface friction volt effect. The core of the invention lies in that high-concentration two-dimensional electron gas (2DEG) and surface state characteristics in the u-GaN / AlGaN / AlN / GaN heterojunction are utilized, and the friction volt effect is combined, so that efficient mechanical energy-electric energy conversion is realized. In the dynamic Schottky contact of the D-GaN HEMT and metal, unbalanced carriers in u-GaN Cap are excited by friction, electrons and holes are separated by a built-in electric field, surface state electrons of u-GaN Cap obtain friction energy to be transited to a conduction band, and a Schottky barrier is overcome to form current; in the sliding process, metal and a semiconductor interact to increase the surface state density, a large number of electrons are excited, chemical bonds are formed, two-dimensional electron gas is formed on an AlN / GaN interface and flows back under a reverse electric field, the electron concentration is maintained, current is continuously generated, and finally direct current is formed in an external circuit.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor energy technology, and particularly to a metal-semiconductor direct current triboelectric nanogenerator (TENG) based on gallium nitride (GaN) high electron mobility transistors (HEMTs), which is applicable to micro-nano energy harvesting and self-powered electronic devices. Background Art

[0002] The advent of the era of artificial intelligence has led to an increased demand for energy in society, and the demand for renewable energy has become increasingly urgent. In 2012, the triboelectric nanogenerator (TENG) invented by the team of Zhong Lin Wang was able to utilize mechanical energy in the environment and convert it into electrical energy, thus making full use of natural resources to serve humanity and promoting the sustainable development of energy. Through continuous innovation and improvement, the output performance of TENG has been significantly improved, changing from alternating current to direct current, with the current increasing from the nanoampere (nA) level to the microampere (μA) or even milliampere (mA) level, and the power density increasing from milliwatts per square meter (mW / m 2 ) to watts per square meter (W / m 2 ), demonstrating great power generation potential. To adapt to the current trend of miniaturization and integration of semiconductor electronic devices, semiconductor direct current TENG has emerged. Compared with traditional polymer TENG, it is more suitable for the development of small electronic devices.

[0003] Currently, research on metal-semiconductor direct current triboelectric nanogenerators (MSDC TENG) mainly focuses on n-type or p-type doped semiconductor materials to increase the carrier concentration and study the electron transport mechanism during the friction process. For example, Zhang et al. reported an MSDC TENG composed of stainless steel and n-Si / p-Si wafers, whose working principle is based on the tribovoltaic effect. In recent years, the third-generation semiconductor material gallium nitride (GaN) has been used as a triboelectric material. The inventor team of this application has made progress in this field. Xiao et al. developed a Cu / p-GaN TENG, and by adjusting the carrier concentration of p-GaN, its short-circuit current density increased by 51 times. In addition, Chen et al. demonstrated that when different bias voltages are applied to Si / n-GaN, the transport direction of carriers is controlled by the interfacial electric field. However, due to the low carrier concentration of undoped semiconductors, research on the transport mechanism and output performance of undoped semiconductor materials in MSDC TENG is still limited. Therefore, there is an urgent need to develop high-performance direct current TENG based on GaN.

[0004] The information disclosed in this background art section is only intended to enhance the overall understanding of the present invention and should not be regarded as an admission or any form of implication that this information constitutes prior art already known to those of ordinary skill in the art. Summary of the Invention

[0005] The object of the present invention is to provide a metal-semiconductor direct current triboelectric nanogenerator based on depletion-mode GaN HEMT. By sliding metal titanium (Ti) on the u-GaN / AlGaN / AlN / GaN heterostructure GaN HEMT thin film, a novel MSDC TENG is designed. The HEMT material itself has a relatively high 2DEG without deliberate doping, which can thus affect the charge transfer during friction to obtain high-voltage and high-power density output.

[0006] To achieve the above object, the present invention adopts the following technical solutions to solve:

[0007] In the first aspect, the present invention provides a metal-semiconductor direct current triboelectric nanogenerator based on depletion-mode GaN HEMT, which comprises:

[0008] A titanium (Ti) metal friction layer;

[0009] A GaN HEMT friction layer, the structure of which is a u-GaN / AlGaN / AlN / GaN heterojunction. The GaN HEMT friction layer is grown on a sapphire substrate by metal-organic chemical vapor deposition (MOCVD);

[0010] The titanium (Ti) metal friction layer can generate a direct current by reciprocating sliding contact with the GaN HEMT friction layer.

[0011] Preferably, the GaN HEMT friction layer is a 2-inch wafer, and its two-dimensional electron gas (2DEG) concentration is ~1.6×10 13 cm -2 , and the sheet resistance is ~450 ohm / sq.

[0012] Preferably, the thickness of the GaN channel layer of the GaN HEMT friction layer is 2 μm, the thickness of the AlN interlayer layer is 1-2 nm, the thickness of the AlGaN barrier layer is 19-22 nm, and the thickness of the u-GaN cap layer is 2 nm.

[0013] Preferably, the size of the titanium (Ti) metal friction layer is 2 cm×1.2 cm. The sliding distance of the reciprocating sliding of the titanium (Ti) metal friction layer and the GaN HEMT friction layer is 5-32 mm, the load pressure is 1-9 N, the sliding speed is 0.1-1 m / s, and the sliding acceleration is 1-5 m / s 2 .

[0014] In the second aspect, the present invention provides a method for generating electricity using the metal-semiconductor direct current triboelectric nanogenerator based on depletion-mode GaN HEMT, which comprises the following steps:

[0015] (1) The u-GaN / AlGaN / AlN / GaN heterojunction is epitaxially grown on a sapphire substrate by metalorganic chemical vapor deposition (MOCVD) to obtain the GaN HEMT friction layer;

[0016] (2) Pure indium (In) is deposited on the surface of the GaN HEMT friction layer, and a pure indium ohmic electrode is formed by high-temperature annealing on a heating stage;

[0017] (3) The titanium (Ti) metal friction layer is fixed to the linear motor motion module as the top friction layer, and reciprocating sliding contact is made with the bottom friction layer GaN HEMT friction layer fixed on the working platform to generate direct current.

[0018] Preferably, the production temperature of the pure indium ohmic electrode formed by high-temperature annealing on the heating stage in step (2) is 350 °C.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The present invention utilizes the high-concentration two-dimensional electron gas (2DEG) and surface state characteristics in the u-GaN / AlGaN / AlN / GaN heterojunction, and combines the triboelectric effect to efficiently achieve mechanical energy-electric energy conversion. An internal built-in electric field will be generated at the heterojunction interface due to spontaneous polarization and piezoelectric polarization, thereby causing electron transition and forming a high-concentration two-dimensional electron gas. Since the outermost layer is intrinsic GaN (u-GaN), the electrons are mainly provided by its surface states. It should be emphasized that the present invention uses HEMT as a new triboelectric material, and these properties it itself has can effectively improve the performance of the MSDC TENG. Description of the Drawings

[0021] Figure 1 is a three-dimensional structure schematic diagram of a metal-semiconductor DC triboelectric nanogenerator based on a depletion-mode GaN HEMT in the present invention;

[0022] Figure 2 is a physical connection diagram of the Ti layer and the GaN HEMT in the metal-semiconductor DC triboelectric nanogenerator of the present invention;

[0023] Figure 3 is the short-circuit current (ISC) and open-circuit voltage (UOC) curves of the metal-semiconductor DC triboelectric nanogenerator of the present invention under different reciprocating motion conditions;

[0024] Figure 4 is the output short-circuit current waveform of the metal-semiconductor DC triboelectric nanogenerator of the GaN HEMT of the present invention;

[0025] Figure 5It is the output open-circuit voltage waveform of the metal-semiconductor DC triboelectric nanogenerator of the GaN HEMT of the present invention;

[0026] Figure 6 It is the output power density curve of the metal-semiconductor DC triboelectric nanogenerator of the GaN HEMT of the present invention;

[0027] Figure 7 It is the short-circuit current (ISC) and open-circuit voltage (UOC) curves of the metal-semiconductor DC triboelectric nanogenerator of the GaN HEMT of the present invention;

[0028] Figure 8 It is a schematic diagram of the metal-semiconductor DC triboelectric nanogenerator of the GaN HEMT of the present invention driving an LED and an electronic watch. Detailed implementation manners

[0029] The following combines the accompanying drawings to describe in detail the specific implementation manners of the present invention. However, it should be understood that the protection scope of the present invention is not limited by the specific implementation manners.

[0030] Unless otherwise clearly stated, throughout the specification and claims, the term "comprising" or its variations such as "including" or "having" etc. will be understood to include the stated elements or components, without excluding other elements or other components.

[0031] Example 1

[0032] Combined with Figure 1 , according to a metal-semiconductor DC triboelectric nanogenerator based on a depletion-mode GaN HEMT in a specific implementation manner of the invention, it includes a Ti metal friction layer; a depletion-mode GaN HEMT friction layer, and the structure of the GaN HEMT friction layer is a u-GaN / AlGaN / AlN / GaN heterojunction (combined with Figure 1 , the arrangement order is GaN cap, AlGaN barrier, AlN interlayer, GaN channel, C-doped GaN buffer, AlN buffer, and Sapphire), and is grown on a sapphire substrate by metal-organic chemical vapor deposition (MOCVD); combined with Figure 2, the Ti metal friction layer and the GaN HEMT friction layer generate direct current through reciprocating sliding contact without a rectifying circuit. In the dynamic Schottky contact between the D-GaN HEMT and the metal, frictional excitation generates non-equilibrium carriers in the u-GaN Cap, and the built-in electric field separates electrons and holes. The electrons in the surface states of the u-GaN Cap gain frictional energy and jump to the conduction band, overcoming the Schottky barrier to form a current. In addition, during the sliding process, the interaction between the metal and the semiconductor increases the surface state density, exciting a large number of electrons and forming chemical bonds. A two-dimensional electron gas is formed at the AlN / GaN interface and flows back under the reverse electric field, maintaining the electron concentration and continuously generating current, ultimately forming direct current in the external circuit. The technology in this embodiment can be widely applied to self-powered sensors, wearable devices, and micro-nano energy systems.

[0033] In a specific embodiment, the GaN HEMT friction layer is a 2-inch wafer with a two-dimensional electron gas (2DEG) concentration of ~1.6×10^13 cm^-2 and a sheet resistance of ~450 ohm / sq. At the u-GaN / AlGaN / AlN / GaN heterojunction interface, a built-in electric field is generated due to spontaneous polarization and piezoelectric polarization, causing electrons to transition and form a high-concentration two-dimensional electron gas. Since the outermost layer is intrinsic GaN (u-GaN), the electrons are mainly provided by its surface states. The size of the Ti metal friction layer is 2 cm × 1.2 cm. In some specific embodiments, the sliding distance between the titanium (Ti) metal friction layer and the GaN HEMT friction layer during reciprocating sliding is 5 - 32 mm, the load pressure is 1 - 9 N, the sliding speed is 0.1 - 1 m / s, and the sliding acceleration is 1 - 5 m / s 2 , combined with Figure 3 , a direct current can be stably generated within the above sliding parameter range. Taking the sliding distance of 32 mm, the load pressure of 5 N, the sliding speed of 1 m / s, and the sliding acceleration of 3 m / s 2 as an example for illustration, the open-circuit voltage output under this condition is 45.5 V, the short-circuit current output is 26 μA, and the peak power density output is 2.32 W / m 2 . It can directly drive 14 series-connected LEDs and a digital watch without an additional rectifying or energy storage unit.

[0034] The principle by which the Ti metal friction layer and the GaN HEMT friction layer generate direct current through reciprocating sliding contact is as follows:

[0035] 1) During the dynamic Schottky contact between the D-GaN HEMT and the metal, frictional motion causes the generation of non-equilibrium charge carriers in the u-GaN cap, which are separated under the action of the built-in electric field. The electrons diffuse in the semiconductor, while the holes are driven to the metal-semiconductor interface, thus forming a direct current flowing from the semiconductor to the metal side.

[0036] 2) Electrons in the surface states of the Ti / µ-GaN cap gain frictional energy and jump to the bottom of the conduction band of the µ-GaN cap. After overcoming the Schottky barrier, these electrons move to the top layer of the µ-GaN and can also form a direct current flowing from the semiconductor to the metal side. The interaction with the metal during the sliding process leads to an increase in the surface state density, which can excite a large number of electrons, form many chemical bonds and release "Bindington", thus generating a frictional current.

[0037] 3) Different from elemental and compound semiconductors, electrons in the D-GaN HEMT move longitudinally along the conduction band during friction and can form a two-dimensional electron gas at the AlN / GaN channel interface. Under the action of the electric field of the two-dimensional electron gas in the direction opposite to the built-in electric field direction, the electrons flow back to the µ-GaN cap. This process maintains the electron concentration at a certain level and continuously generates current, significantly improving the activity of electrons at the interface, thereby enhancing the density and mobility of the two-dimensional electron gas. Therefore, a direct current is formed in the external circuit during the sliding process, and then a potential difference is generated on the surface of the Ti metal and the D-GaN HEMT wafer.

[0038] Example 2

[0039] This example provides a method for generating electricity using a metal-semiconductor direct current friction nanogenerator of a depletion-mode GaN HEMT. The method includes the following steps:

[0040] (1) Use MOCVD to epitaxially grow a µ-GaN / AlGaN / AlN / GaN heterojunction on a sapphire substrate to obtain a depletion-mode GaN HEMT. The thickness of the GaN channel layer of the GaN HEMT is 2 µm, the thickness of the AlN interlayer is 1 - 2 nm, the thickness of the AlGaN barrier layer is 19 - 22 nm, and the thickness of the µ-GaN cap layer is 2 nm.

[0041] (2) Deposit pure indium (In) on the surface of the GaN HEMT and form a pure indium ohmic electrode by high-temperature annealing on a heating stage at a temperature of 350 °C;

[0042] (3) Fix the Ti metal as the top friction layer to the linear motor motion module and make reciprocating sliding contact with the GaN HEMT friction layer fixed on the working platform as the bottom friction layer. Reciprocating sliding is carried out at a sliding length of 32 mm, a load pressure of 5 N, a sliding speed of 1 m / s, and a sliding acceleration of 3 m / s 2 for reciprocating sliding;

[0043] (4) The short - circuit current and open - circuit voltage are measured by a Keithley 6514 programmable electrometer. The Ti metal and the GaN HEMT are respectively connected to the interface of the electrometer through external wires for testing.

[0044] For the metal - semiconductor DC triboelectric nanogenerator based on depletion - mode GaN HEMT prepared in Example 1, the test results are as follows:

[0045] Reference Figure 4 High - resolution X - ray diffraction 2θ - ω (002) scans are used to study the crystal properties of the D - GaN HEMT thin film. Three diffraction peaks are observed on GaN, AlGaN, and AlN respectively for this thin film, indicating the structural components of the D - GaN HEMT material.

[0046] Reference Figure 5 The volt - ampere characteristic curve is shown. Pure indium (In) is annealed at a high temperature (350 °C) to form an electrode on the surface of the D - GaN HEMT wafer. It shows that there is a good ohmic contact between the D - GaN HEMT wafer and the In electrode.

[0047] Reference Figure 6 To evaluate the performance of the metal - semiconductor DC triboelectric nanogenerator based on depletion - mode GaN HEMT, the short - circuit current (ISC) and open - circuit voltage (UOC) are measured using a programmable electrometer (Keithley 6514). At a sliding distance of 32 mm, a reciprocating speed of 1 m / s, a sliding acceleration of 3 m / s 2 and a pressure of 5 N, the recorded peaks are approximately 26 μA and 45.5 V respectively.

[0048] Reference Figure 7 The output power and internal resistance of the metal - semiconductor DC triboelectric nanogenerator based on depletion - mode GaN HEMT are measured. By changing the load resistance, the change in electrical output is observed: the current drops from 26 μA to 0 μA, while the voltage rises from 0 V to 45.5 V. When the load resistance is about 10 6 ohms (close to the matching condition of the internal resistance and the maximum power point in the maximum power transfer law), the calculated maximum power density is 2.32 W / m 2 , and this point corresponds to the intersection of the voltage - current curve.

[0049] Reference Figure 8Demonstrates the ability of a metal-semiconductor DC triboelectric nanogenerator based on depletion-mode GaN HEMT to power devices. The metal-semiconductor DC triboelectric nanogenerator based on depletion-mode GaN HEMT can light up all 14 green LEDs, which emit bright light in the dark. The typical lighting voltage of the 2×5×7 square green LEDs is about 3.0 - 3.4V. It can also drive the electronic watch in the figure to work properly.

[0050] The foregoing description of the specific exemplary embodiments of the present invention is for purposes of illustration and exemplification. These descriptions are not intended to limit the invention to the precise forms disclosed, and it is obvious that many changes and variations are possible in light of the above teachings. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the present invention and its practical applications, so that those skilled in the art can implement and utilize various different exemplary embodiments of the present invention, as well as various different selections and changes. The scope of the present invention is intended to be defined by the claims and their equivalents.

[0051] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A metal-semiconductor DC triboelectric nanogenerator based on depletion-mode GaN HEMT, characterized in that, Comprising: Titanium (Ti) metal friction layer; GaN HEMT friction layer with a structure of u-GaN / AlGaN / AlN / GaN heterojunction, and the GaN HEMT friction layer is grown on a sapphire substrate by metalorganic chemical vapor deposition (MOCVD); The titanium (Ti) metal friction layer can generate direct current through reciprocating sliding contact with the GaN HEMT friction layer.

2. The metal-semiconductor DC triboelectric nanogenerator based on depletion-mode GaN HEMT according to claim 1, characterized in that The GaN HEMT friction layer is a 2-inch wafer with a two-dimensional electron gas (2DEG) concentration of ~1.6×10 13 cm -2 , and a sheet resistance of ~450 ohm / sq.

3. The metal-semiconductor DC triboelectric nanogenerator based on depletion-mode GaN HEMT according to claim 1, wherein The thickness of the GaN channel layer of the GaN HEMT friction layer is 2 μm, the thickness of the AlN interlayer is 1 - 2 nm, the thickness of the AlGaN barrier layer is 19 - 22 nm, and the thickness of the u-GaN cap layer is 2 nm.

4. The metal-semiconductor DC triboelectric nanogenerator based on depletion-mode GaN HEMT according to claim 1, characterized in that The size of the titanium (Ti) metal friction layer is 2 cm × 1.2 cm. The sliding distance of the reciprocating sliding between the titanium (Ti) metal friction layer and the GaN HEMT friction layer is 5 - 32 mm, the load pressure is 1 - 9 N, the sliding speed is 0.1 - 1 m / s, and the sliding acceleration is 1 - 5 m / s 2 .

5. A method for generating electricity using the metal-semiconductor DC triboelectric nanogenerator based on depletion-mode GaN HEMT according to any one of claims 1 to 4, characterized in that, Including the following steps: (1) Epitaxially grow u-GaN / AlGaN / AlN / GaN heterojunction on a sapphire substrate by metalorganic chemical vapor deposition (MOCVD) to obtain the GaN HEMT friction layer; (2) Deposit pure indium (In) on the surface of the GaN HEMT friction layer, and form a pure indium ohmic electrode through high-temperature annealing on a heating stage; (3) Fix the titanium (Ti) metal friction layer as the top friction layer to the linear motor motion module, and make reciprocating sliding contact with the bottom friction layer GaN HEMT friction layer fixed on the working platform to generate direct current.

6. The method according to claim 5, wherein The manufacturing temperature of the pure indium ohmic electrode formed by high-temperature annealing on the heating stage in step (2) is 350 °C.

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