High-efficiency high-power rectifier diode device based on thin barrier AlGaNGaN and preparation method of high-efficiency high-power rectifier diode device

Abstract

The invention belongs to the technical field of microwave radio frequency energy conversion, and particularly relates to a high-efficiency high-power rectifier diode device based on a thin barrier AlGaNGaN and a preparation method of the high-efficiency high-power rectifier diode device. The method comprises the following steps: firstly, selecting a substrate layer, and then growing an AlN nucleating layer on the substrate; growing a GaN buffer layer on the AlN nucleating layer; growing a GaN layer on the GaN buffer layer, and growing a barrier layer AlGaN on the GaN channel layer; according to the method, the high-efficiency and high-power rectifier diode device based on the thin barrier AlGaNGaN is obtained by firstly cleaning a test piece, then preparing an ohmic junction and a Schottky junction and finally passivating the surface, high rectification efficiency can be realized through the method, and a leading level is achieved in a known GaN SBD (Schottky Bridge Diode) formed rectifier circuit.

Description

Technical Field

[0001] The present invention belongs to the technical field of microwave radio frequency energy conversion, and particularly relates to a high-efficiency high-power rectifier diode device based on thin-barrier AlGaN / GaN and a preparation method thereof. Background Art

[0002] Since the concept of wireless power transfer (WPT) was proposed, many scholars have been engaged in the theoretical and practical research of WPT. Although microwave wireless power transfer (MWPT) can achieve long-distance energy transfer, its system efficiency is still not ideal at present. The total system efficiency is the product of the DC-RF conversion efficiency, the transmission efficiency between the transmitting and receiving antennas, and the receiving antenna RF-DC conversion efficiency. Therefore, high-efficiency rectification of MWPT has always been the research focus in the field of wireless energy transfer. The function of the rectifier circuit is to convert the RF energy collected by the antenna into DC energy for the load to use. In terms of rectification efficiency, the rectifier diode is a crucial influencing factor. In the research field of rectifier diodes, Schottky barrier diodes (SBDs) based on gallium nitride (GaN) substrates are common research objects.

[0003] In the prior art, a GaN-based microwave rectifier circuit was designed, which adopted a single parallel configuration and achieved a maximum efficiency of 72.4% at an input power of 33.4 dBm. The prior art also proposed a lateral GaN SBD rectifier circuit, which integrated DC and high-frequency filtering functions and reached a maximum efficiency of 75.5% in the power range of 26 - 37 dBm at a frequency of 5.8 GHz. However, the GaN diode structure is often used in the prior art, but it cannot well reduce the influence of the junction resistance on the rectification conversion efficiency. Therefore, the conversion efficiency is relatively low. Summary of the Invention

[0004] Aiming at the deficiencies in the prior art, the present invention provides a high-efficiency high-power rectifier diode device based on thin-barrier AlGaN / GaN. The diode device includes 4H-SiC, an AlN nucleation layer, a GaN buffer layer, a GaN channel layer, and a barrier layer AlGaN from bottom to top. A cathode ohmic contact, an anode Schottky contact, and a passivation layer SiN are provided on the barrier layer AlGaN x , and the barrier layer AlGaN is 5 - 10 nm.

[0005] A preparation method of a high-efficiency high-power rectifier diode device based on thin-barrier AlGaN / GaN specifically includes the following steps:

[0006] S1: Select a substrate layer;

[0007] S2; Grow an AlN nucleation layer on the substrate layer of S1;

[0008] S3: Grow a GaN buffer layer on the AlN nucleation layer of S2;

[0009] S4: Grow a GaN channel layer on the GaN buffer layer of S3;

[0010] S5: Grow a barrier layer AlGaN on the GaN channel layer of S4;

[0011] S6: Clean and dry the epitaxial wafer obtained after epitaxy of S1 - S5, and immerse it in an acid solution to obtain a pretreated test piece;

[0012] S7: Fabricate a cathode ohmic contact on the barrier layer;

[0013] S8: Fabricate an anode Schottky contact on the barrier layer;

[0014] S9: Grow a layer of SiNx passivation layer on the surface of the test piece to obtain a high - efficiency high - power rectifier diode device based on thin - barrier AlGaN\GaN.

[0015] Furthermore, the substrate described in S1 is a 4 - inch semi - insulating SiC single crystal. Ammonia (NH 3 ) is used as the Group V source, trimethylgallium TMGa and trimethylaluminum TMAl are used as Group III elements, and hydrogen and nitrogen are used as carrier gases.

[0016] Furthermore, the thickness of the AlN nucleation layer in S2 is 100 nm, the thickness of the GaN buffer layer in S3 is 1600 nm, and the thickness of the GaN channel layer in S4 is 160 nm.

[0017] Furthermore, the acid solution in S6 is dilute hydrochloric acid, and HC1:H 2 O = 1:1, and the soaking time is 5 min.

[0018] Furthermore, the steps of fabricating the cathode ohmic contact described in S7 include:

[0019] Step 1: Immerse the test piece in an acid solution for pretreatment;

[0020] Step 2: Use photoresist as a mask to lithograph the ohmic electrode area, and use electron beam evaporation deposition or magnetron sputtering. Immerse the test piece in a solvent, and use ultrasound to remove the photoresist and strip the metal to obtain a processed test piece;

[0021] Step 3: Rapidly anneal the test piece to form a cathode ohmic contact.

[0022] Further, in the electron beam evaporation deposition / magnetron sputtering process described in step 2, Ti / Al / Ni / Au metal is used. The thickness of Ti is 10 - 40 nm, the thickness of Al is 60 - 200 nm, the thickness of Ni is 40 nm, and the thickness of Au is 75 nm.

[0023] Further, in the rapid annealing process described in step 3, the temperature is 750 - 900 °C and the time is 15 - 60 s.

[0024] Further, the SiNx passivation layer described in S9 is 20 - 200 nm.

[0025] Beneficial effects

[0026] Generally speaking, the thickness of the AlGaN barrier layer is between 20 nm and 30 nm. Such a barrier thickness can effectively control the turn-on voltage and the junction capacitance component of the Schottky device. Reducing the barrier layer thickness will cause an increase in the junction capacitance component, resulting in a decrease in the cut-off frequency of the device. At the same time, it will cause a decrease in the reverse breakdown voltage, making the device's tolerable power low. However, the equivalent resistance of this Schottky device is relatively large, and it is difficult to achieve a high-efficiency radio frequency energy conversion device. This invention patent adopts a thin barrier technology, designs a Schottky barrier layer (AlGaN layer) with a thickness of 18 nanometers, and strictly controls the electrode spacing of the SBD, effectively reducing the influence of the diode junction resistance on the rectification efficiency.

[0027] In addition, an AlGaN / GaN heterojunction diode with a barrier layer thickness less than 10 nm is designed, and its rectification performance is significantly improved. The equivalent series resistance of this Schottky device is within 3 ohms, and the zero-bias junction capacitance is effectively controlled within 0.5 pF. Under the working conditions of W-level input power, a rectification conversion efficiency of more than 80% is achieved.

[0028] Through the preparation method of a high-efficiency high-power rectifier diode device based on a thin barrier AlGaN / GaN provided by the present invention, firstly, through reasonable device design and optimization, the rectification efficiency is significantly improved. Under the conditions of an impedance of 170 Ω and an input power of 700 mW, the rectification efficiency reaches 81%, leading the reported GaN SBD rectification circuits. And it has an advanced thin barrier design. By adopting a thin barrier AlGaN structure, the barrier layer thickness is reduced, resulting in a significant reduction in the turn-on voltage of the diode and an improvement in the rectification efficiency. The input power of the device provided by the present invention is 20 dBm - 30 dBm, and the application frequency is 500 MHz - 20 GHz. And this device is applicable to the microwave - DC energy conversion direction. At the same time, this structure effectively reduces the reverse leakage current, making the device have excellent breakdown voltage characteristics and power handling capabilities.

[0029] Through precise process control and simulation optimization, the present invention realizes the mass production of SBD high-performance rectifier devices, while ensuring the long-term stability and reliability of the rectifier circuit. In actual tests, the devices and circuits showed excellent voltage resistance, low power consumption characteristics and high-efficiency rectification effects. The present invention can be widely used in high-frequency power rectifier devices, wireless energy transmission equipment, microwave communication equipment and other high-efficiency power conversion systems, providing high-performance, low-power solutions for related fields. The present invention not only solves the problem of limited rectification efficiency in existing GaN-based rectifier diodes, but also achieves higher device and circuit performance through complete simulation and process flow linkage design, greatly improving rectification efficiency and reducing power consumption, and has significant technical innovation and industrial promotion value. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other relevant drawings can be obtained based on these drawings without creative work. In the drawings:

[0031] Figure 1 This is a block diagram of a microwave / radio frequency energy transmission system according to Embodiment 1 of the present invention;

[0032] Figure 2 A single diode series-parallel rectifier circuit diagram of Embodiment 1 of the present invention;

[0033] Figure 3 The voltage doubler / charge pump rectifier circuit and the multi-stage rectifier circuit thereof of embodiment 1 of the present invention;

[0034] Figure 4 This is a structural diagram of a thin barrier GaN rectifier device embodiment of embodiment 1 of the present invention;

[0035] Figure 5 This is a diagram of high rectification conversion efficiency of Example 1 of the present invention;

[0036] Figure 6 This is a preparation flow chart of Example 1 of the present invention. DETAILED DESCRIPTION

[0037] The following will be combined with Example 1 of the present invention and the attached Figures 1-6 , the technical solution of the present invention is clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] Example 1

[0039] Combined with Figure 6 The preparation flow chart can obtain a preparation method of a high-efficiency high-power rectifier diode device based on a thin-barrier AlGaN / GaN provided by the present invention.

[0040] S1; Based on metal-organic chemical vapor deposition (MOCVD) technology for material growth, the substrate is a 4-inch semi-insulating SiC single crystal. Using ammonia (NH 3 ) as the group V source, trimethylgallium (TMGa) and trimethylaluminum (TMAl) as the group III, and hydrogen and nitrogen as the carrier gases, perform in-situ baking of the substrate to remove surface impurities and obtain the substrate layer;

[0041] S2: Grow a 100-nm AlN nucleation layer on the substrate;

[0042] S3: Grow a 1600-nm-thick GaN buffer layer on the AlN nucleation layer;

[0043] S4: Grow a 160-nm GaN layer on the GaN buffer layer;

[0044] S5: Grow a barrier layer AlGaN on the GaN channel layer, and control the thickness of the barrier layer at 8 nm;

[0045] S6: Use ionized water to clean the epitaxial surface to remove most of the impurities and surface contaminants; then soak the epitaxial wafer in acetone and ethanol respectively, and use heating and ultrasonic methods to remove contaminants; use deionized water to clean the epitaxial wafer to remove residual organic solvents, and dry it with a nitrogen gun; soak the epitaxial wafer in a dilute hydrochloric acid solution (HCl:H 2 O = 1:1) for 5 minutes to remove the natural oxide layer on the surface and obtain a test piece;

[0046] S7: Soak the test piece of S6 in a dilute hydrochloric acid solution (HCl:H 2 O = 1:1) for 1 minute to remove the oxide layer on the epitaxial wafer surface; use photoresist as a mask, photolithograph the ohmic electrode area, and use electron beam evaporation deposition to deposit a 10-nm-thick metal Ti, a 60-nm-thick metal Al, a 40-nm-thick metal Ni, and a 75-nm-thick metal Au; immerse the test piece in an acetone solution, use an ultrasonic instrument to remove the photoresist and strip the metal; put the test piece into a rapid annealing furnace filled with nitrogen and perform rapid annealing of the metal at a high temperature of 850 °C for 30 seconds;

[0047] S8: Use Ni and Wu to make an anode Schottky contact on the barrier layer

[0048] S9: Use a PECVD device and use reverse photoresist etching to define Schottky electrode holes and Ohmic electrode thickening regions. A 20-nm SiNx passivation layer is grown on the surface to obtain a high-efficiency high-power rectifier diode device based on a thin-barrier AlGaN / GaN.

[0049] The annealing treatment method in S7 can cause Ti to react with N in AlGaN to generate TiN and produce a large number of N vacancies in the AlGaN barrier layer, thereby forming an Ohmic contact. Al has a low work function and can cover the surface of Ti to form an alloy. Ni is used as an isolation layer between Au and Al to prevent the two from diffusing into each other. Au has good electrical conductivity and stability and can protect the anode metal from oxidation. In addition, rapid annealing can also help reduce the formation of surface states. The Ohmic contact resistance in this embodiment is controlled at 0.3 Ω / mm.

[0050] Combined with Figure 1 , the block diagram of the microwave wireless power transfer system and the subsystem efficiency are obtained. The total system efficiency is the product of the DC-RF conversion efficiency, the transmission efficiency between the transmitting and rectenna, and the RF-DC conversion efficiency of the receiving antenna. Therefore, high-efficiency rectification of MWPT has always been the research focus in the field of wireless power transfer. The role of the rectifier circuit is to convert the RF power collected by the antenna into DC power for the load to use.

[0051] Combined with Figure 2 , it can be seen that the single-tube parallel / series rectifier circuit structure commonly used in the rectifier circuit / chip Figure 2 (a) is a single-tube parallel (single shunt), Figure 2 (b) is a single-tube series (single series) rectifier circuit structure. In the figure, Diode indicates that the switching device used includes a diode and a MOS / HEMT switching device, and the direction of the switching device in the figure is not limited. The direction of the switching device only affects the positive and negative of the output DC voltage and does not affect the working state of the rectifier circuit. C2 in the figure is the output filter (output filter) capacitor, which can be replaced by an open-end microstrip line (Open-end Microstrip Line).

[0052] Combined with Figure 3 , it can be seen that Figure 3 is the double-voltage / charge pump rectifier circuit structure (Double Voltage / Charge Pump) and its multi-stage double-voltage rectifier circuit structure commonly used in the rectifier circuit / chip, Figure 3(b) is Dickson multi-stage voltage multiplier / charge pump rectification, Figure 3 (c) is the Cockcroft Walton multi-stage voltage multiplier / charge pump rectifier circuit structure. Figure 3 The diode symbol in it indicates that the switching device shown includes diodes and MOS / HEMT Schottky switching devices, and Figure 3 the direction of the switching device is not limited. The direction of the switching device only affects the positive and negative of the output DC voltage and does not affect the operation of the rectifier circuit, but their switching directions are all in the same direction. Figure 3 Both C and Co in it represent capacitors (Capacitors). Figure 3 The number of stages used in the rectifier circuit structure is not limited. Figure 2 and Figure 3 The rectifier circuit structures in can both be used as Figure 1 the rectifier circuit part in.

[0053] Combined with Figure 5 it can be seen that Figure 6 this is the high rectification efficiency that the device of this patent proposal can achieve. It can be seen that its highest rectification efficiency is 81%, far superior to the traditional ultra-low power rectification scheme. Figure 6 It is only a diagram showing the rectification ability and does not limit the maximum rectification efficiency and reflectivity of the device.

[0054] Through a preparation method of a high-efficiency high-power rectifier diode device based on thin-barrier AlGaN\GaN provided by the present invention, by using the thin-barrier technology, an AlGaN layer with a thickness of 5 - 10 nm is obtained, effectively reducing the influence of the diode junction resistance on the rectification efficiency, and having strong process adaptability, leading rectification efficiency, performance stability and broad application prospects.

Claims

1. A high-efficiency, high-power rectifier diode device based on thin-barrier AlGaN\GaN, characterized in that: The diode device comprises 4H-SiC, AlN nucleation layer, GaN buffer layer, GaN channel layer, and barrier layer AlGaN from bottom to top, wherein the barrier layer AlGaN is provided with cathode ohmic contact, anode Schottky contact and passivation layer SiN x , the barrier layer AlGaN is 5 to 10 nm.

2. The method for preparing a thin barrier AlGaN\GaN high-efficiency high-power rectifier diode device according to claim 1, characterized in that: The following steps are involved: S1: Select the substrate layer; S2: growing an AlN nucleation layer on the substrate layer of S1; S3: growing a GaN buffer layer on the AlN nucleation layer of S2; S4: growing a GaN channel layer on the GaN buffer layer of S3; S5: growing a barrier layer AlGaN on the GaN channel layer of S4; S6: cleaning and drying the epitaxial wafer obtained after the epitaxy in S1 to S5, and immersing it in an acid solution to obtain a pretreated test wafer; S7: making a cathode ohmic contact on the barrier layer; S8: making an anode Schottky contact on the barrier layer; S9: A SiNx passivation layer was grown on the surface of the test piece to obtain a high-efficiency and high-power rectifier diode device based on thin-barrier AlGaN\GaN.

3. The method for preparing a thin barrier AlGaN\GaN high-efficiency high-power rectifier diode device according to claim 2, characterized in that: The substrate described in S1 is a 4-inch semi-insulating SiC single crystal, using ammonia (NH3) as a group V source, trimethylgallium TMGa and trimethylaluminum TMAl as group III sources, and hydrogen and nitrogen as carrier gases.

4. The method for preparing a thin barrier AlGaN\GaN high-efficiency high-power rectifier diode device according to claim 2, characterized in that: The thickness of the AlN nucleation layer in S2 is 100 nm, the thickness of the GaN buffer layer in S3 is 1600 nm, and the thickness of the GaN channel layer in S4 is 160 nm.

5. The method for preparing a thin barrier AlGaN\GaN high-efficiency high-power rectifier diode device according to claim 2, characterized in that: The acid solution described in S6 is dilute hydrochloric acid, and HCl:H2O=1:1, and the immersion time is 5 minutes.

6. The method for preparing a thin barrier AlGaN\GaN high-efficiency high-power rectifier diode device according to claim 2, characterized in that: The step of making the cathode ohmic contact described in S7 comprises: Step 1: Soak the test piece in an acid solution for pretreatment; Step 2: Use photoresist as a mask to photolithograph the ohmic electrode area, and use electron beam evaporation deposition\magnetron sputtering to immerse the test piece in a solvent, and use ultrasound to remove the photoresist and strip the metal to obtain a processed test piece; Step 3: Rapidly anneal the test piece to form a cathode ohmic contact.

7. The method for preparing a thin barrier AlGaN\GaN high-efficiency high-power rectifier diode device according to claim 2, characterized in that: Ti / Al / Ni / Au metal is used in the electron beam evaporation deposition or magnetron sputtering process described in step 2, the thickness of Ti is 10-40nm, the thickness of Al is 60-200nm, the thickness of Ni is 40nm, and the thickness of Au is 75nm.

8. The method for preparing a thin barrier AlGaN\GaN high-efficiency high-power rectifier diode device according to claim 2, characterized in that: The temperature in the rapid annealing process described in step 3 is 750-900° C. and the time is 15-60 seconds.

9. The method for preparing a thin barrier AlGaN\GaN high-efficiency high-power rectifier diode device according to claim 2, characterized in that: S9 SiN x The passivation layer is 20-200nm.

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