Power Diode and Its Preparation Method

Abstract

The present disclosure discloses a power diode and a method for manufacturing the same, belonging to the field of diode manufacturing. By adding an AlGaN layer between the N-type heavily doped gallium nitride layer and the N-type lightly doped gallium nitride layer, the formed two-dimensional electron gas can also promote the movement and expansion of electrons, reducing the resistance. In the direction parallel to the surface of the substrate and pointing from the Schottky electrode to the ohmic electrode, increasing the thickness of the AlGaN layer can control the movement rate of electrons at different positions in the power diode, reducing the probability of electrons moving vertically from the Schottky electrode to the ohmic electrode, making the movement paths of electrons in each part of the epitaxial wafer between the two electrodes approximately the same, and enabling electrons to move more uniformly inside the power diode. It can effectively improve the uniformity of current distribution under the condition of equivalent on-resistance, increase the reverse breakdown voltage, and improve the reliability of the finally obtained power diode.

Description

Technical Field

[0001] The present disclosure relates to the field of diode fabrication, and particularly to a power diode and a method for preparing the same. Background Art

[0002] A power diode is the most basic component unit of a power electronic circuit and is commonly used in radio frequency and power devices. A power diode is a basic structure for preparing a power diode. The power diode includes an epitaxial wafer, a Schottky electrode, and an ohmic electrode. The epitaxial wafer includes a substrate and an N-type heavily doped gallium nitride layer and an N-type lightly doped gallium nitride layer that are sequentially stacked on the substrate. A groove extending to the N-type heavily doped gallium nitride layer is formed on the surface of the N-type lightly doped gallium nitride layer. The Schottky electrode is connected to the N-type lightly doped gallium nitride layer, and the ohmic electrode is connected to the surface of the N-type heavily doped gallium nitride layer exposed by the groove.

[0003] Since the areas of the surfaces of the N-type lightly doped gallium nitride layer covered by the Schottky electrode and the N-type heavily doped gallium nitride layer covered by the ohmic electrode are limited, problems such as uneven current distribution and congestion occur during the process of current transfer inside the power diode. Moreover, when there is an electron concentration difference due to different doping concentrations of n-type impurities in the N-type heavily doped gallium nitride layer and the N-type lightly doped gallium nitride layer, the resistance to current transfer will also increase, resulting in insufficient use stability and reliability of the finally obtained power diode. Summary of the Invention

[0004] Embodiments of the present disclosure provide a power diode and a method for preparing the same, which can improve the uniformity of current distribution inside the power diode and reduce the resistance to electron movement, so as to improve the reliability of the obtained power diode. The technical solution is as follows:

[0005] Embodiments of the present disclosure provide a power diode. The power diode includes an epitaxial wafer, a Schottky electrode, and an ohmic electrode. The epitaxial wafer includes a substrate and an N-type heavily doped gallium nitride layer, an AlGaN layer, and an N-type lightly doped gallium nitride layer that are sequentially stacked on the substrate. A groove extending to the N-type heavily doped gallium nitride layer is formed on the surface of the N-type lightly doped gallium nitride layer. The Schottky electrode is connected to the N-type lightly doped gallium nitride layer, and the ohmic electrode is connected to the surface of the N-type heavily doped gallium nitride layer exposed by the groove.

[0006] In the direction parallel to the surface of the substrate and pointing from the Schottky electrode to the ohmic electrode, the thickness of the AlGaN layer increases.

[0007] Optionally, the difference between the maximum thickness and the minimum thickness of the AlGaN layer is 1-12 nm.

[0008] Optionally, the maximum thickness of the AlGaN layer is 3 to 15 nm, and the Al component in the AlGaN layer ranges from 0.07 to 0.3.

[0009] Optionally, in a direction parallel to the surface of the substrate and pointing from the Schottky electrode to the ohmic electrode, the thickness of the AlGaN layer increases linearly.

[0010] Optionally, the thickness of the portion of the AlGaN layer that coincides with the orthographic projection of the Schottky electrode on the substrate is 0.5 to 2 nm.

[0011] An embodiment of the present disclosure provides a method for manufacturing a power diode, the manufacturing method including:

[0012] Providing a substrate;

[0013] Growing an N-type heavily doped gallium nitride layer, an AlGaN layer, and an N-type lightly doped gallium nitride layer on the substrate in sequence. The surface of the N-type lightly doped gallium nitride layer has a groove extending to the N-type heavily doped gallium nitride layer. The Schottky electrode is connected to the N-type lightly doped gallium nitride layer, and the ohmic electrode is connected to the surface of the N-type heavily doped gallium nitride layer exposed by the groove. In a direction parallel to the surface of the substrate and pointing from the Schottky electrode to the ohmic electrode, the thickness of the AlGaN layer increases.

[0014] Optionally, growing an AlGaN layer on the N-type heavily doped gallium nitride layer includes:

[0015] Growing an AlGaN film on the N-type heavily doped gallium nitride layer;

[0016] Placing the substrate in a dry etching device, adjusting the substrate so that an acute angle is formed between the surface of the substrate and the horizontal plane, and etching the AlGaN film to obtain the AlGaN layer.

[0017] Optionally, the range of the acute angle between the surface of the substrate and the horizontal plane is 3° to 15°.

[0018] Optionally, the manufacturing method further includes:

[0019] After growing the N-type heavily doped gallium nitride layer on the substrate and before growing the AlGaN layer on the N-type heavily doped gallium nitride layer, purging and heat preservation treatment are performed on the reaction chamber.

[0020] Optionally, the purging and heat preservation treatment of the reaction chamber is performed under the condition that the temperature is 800°C to 1600°C.

[0021] The beneficial effects brought by the technical solution provided by the embodiment of the present disclosure are:

[0022] An AlGaN layer is added between the N-type heavily doped gallium nitride layer and the N-type lightly doped gallium nitride layer. The AlGaN layer can play a role in balancing the electron concentration to a certain extent, and under the action of the electric field during use, it promotes the stable flow of electrons between the Schottky electrode and the ohmic electrode. Moreover, the piezoelectric polarization between the AlGaN layer and the N-type lightly doped gallium nitride layer and the N-type heavily doped gallium nitride layer can promote the planar spreading of electrons, and the two-dimensional electron gas formed between the aluminum gallium nitride material and the gallium nitride material can also promote the movement and expansion of electrons, improving the electron expansion and increasing the effective downward injection of electrons, which can reduce the resistance of electron movement and lower the resistance. And in the direction parallel to the surface of the substrate and pointing from the Schottky electrode to the ohmic electrode, increasing the thickness of the AlGaN layer can control the movement rate of electrons at different positions in the power diode, reduce the probability of electrons moving vertically from the Schottky electrode to the ohmic electrode, making the movement paths of electrons in each part of the epitaxial wafer between the two electrodes approximately the same, and electrons can move more uniformly inside the power diode. It can effectively improve the uniformity of current distribution under the condition of equivalent on-resistance, increase the reverse breakdown voltage, and improve the reliability of the finally obtained power diode. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present disclosure. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0024] Figure 1 is a schematic structural diagram of a power diode provided by an embodiment of the present disclosure;

[0025] Figure 2 is a schematic structural diagram of another power diode provided by an embodiment of the present disclosure;

[0026] Figure 3 is a flowchart of a method for manufacturing a power diode provided by an embodiment of the present disclosure;

[0027] Figure 4 is a flowchart of another method for manufacturing a power diode provided by an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] To make the purpose, technical solutions, and advantages of the present disclosure clearer, the following will further describe the embodiments of the present disclosure in detail with reference to the drawings.

[0029] Figure 1 is a schematic structural diagram of a power diode provided by an embodiment of the present disclosure, referring to Figure 1It can be seen that an embodiment of the present disclosure provides a power diode, which includes an epitaxial wafer 1, a Schottky electrode 2 and an ohmic electrode 3. The epitaxial wafer 1 includes a substrate 11 and an N-type heavily doped gallium nitride layer 12, an AlGaN layer 13 and an N-type lightly doped gallium nitride layer 14 stacked in sequence on the substrate 11. The surface of the N-type lightly doped gallium nitride layer 14 has a groove S extending to the N-type heavily doped gallium nitride layer 12. The Schottky electrode 2 is connected to the N-type lightly doped gallium nitride layer 14, and the ohmic electrode 3 is connected to the surface of the N-type heavily doped gallium nitride layer 12 exposed by the groove S.

[0030] The thickness of the AlGaN layer 13 increases in a direction parallel to the surface of the substrate 11 and directed from the Schottky electrode 2 to the ohmic electrode 3 .

[0031] An AlGaN layer 13 is added between the N-type heavily doped gallium nitride layer 12 and the N-type lightly doped gallium nitride layer 14. The AlGaN layer 13 can play a certain role in balancing the electron concentration, and promote the stable flow of electrons between the Schottky electrode 2 and the ohmic electrode 3 under the action of the electric field during use. The piezoelectric polarization between the AlGaN layer 13 and the N-type lightly doped gallium nitride layer 14 and the N-type heavily doped gallium nitride layer 12 can promote the planar spreading of electrons, and the two-dimensional electron gas formed between the aluminum gallium nitride material and the gallium nitride material can also promote the movement and expansion of electrons. Improving the electron expansion also increases the effective downward injection of electrons, which can reduce the resistance to electron movement and reduce the resistance. In addition, the thickness of the AlGaN layer 13 increases in the direction parallel to the surface of the substrate 11 and pointing from the Schottky electrode 2 to the ohmic electrode 3, which can control the movement rate of electrons at different positions in the power diode, reduce the probability of electrons moving vertically from the Schottky electrode 2 to the ohmic electrode 3, and make the paths of electrons in various parts of the epitaxial wafer 1 moving between the two electrodes almost the same, so that the electrons can move more evenly inside the power diode. Under the condition of equivalent on-resistance, the uniformity of current distribution can be effectively improved, the reverse breakdown voltage can be increased, and the reliability of the power diode finally obtained can be improved.

[0032] It should be noted that, when no electric field is applied, the electrons inside the power diode tend to move from the part with high electron concentration to the part with low electron concentration. The AlGaN layer 13 itself can also play the role of accepting electrons and balancing the electron concentration between the N-type heavily doped gallium nitride layer 12 and the N-type lightly doped gallium nitride layer 14, and to a certain extent, it can also promote the resistance of each part inside the power diode to be close to the same.

[0033] It should be noted that the surface of the substrate 11 in the present disclosure is the plane with the largest area of ​​the substrate 11 , and this plane is usually used to deposit epitaxial materials, that is, the gallium nitride material in the present disclosure.

[0034] Optionally, in a direction parallel to the surface of the substrate 11 and pointing from the Schottky electrode 2 to the ohmic electrode 3, the thickness of the AlGaN layer 13 increases linearly.

[0035] When the thickness of the AlGaN layer 13 increases linearly, a plane at a certain angle to the horizontal plane can be formed on the surface of the AlGaN layer 13. The surface of the AlGaN layer 13 is relatively flat. At the same time, the growth quality of the N-type heavily doped gallium nitride layer 12 and the N-type lightly doped gallium nitride layer 14 on both sides of the AlGaN layer 13 can be ensured to be good, which can effectively improve the quality of the finally obtained power diode. At the same time, the resistance of each part of the obtained power diode is relatively uniform, and the uniformity of the obtained power diode can be improved.

[0036] It should be noted that in other implementation manners provided in the present disclosure, the thickness of the AlGaN layer 13 can also be set to increase in a gradient manner or in other ways, which can also play a certain role in making the resistance more uniform. The present disclosure does not limit this.

[0037] Exemplarily, the difference between the maximum thickness and the minimum thickness of the AlGaN layer 13 is 1 to 12 nm.

[0038] When the difference between the maximum thickness and the minimum thickness of the AlGaN layer 13 is within the above range, the quality of the obtained AlGaN layer 13 can be ensured to be good. At the same time, the current can be controlled to be relatively uniform, and the quality of the N-type heavily doped gallium nitride layer 12 and the N-type lightly doped gallium nitride layer 14 in contact with the AlGaN layer 13 is good, which can improve the quality and current uniformity of the finally obtained power diode.

[0039] Optionally, the maximum thickness of the AlGaN layer 13 is 3 to 15 nm, and the range of the Al component in the AlGaN layer 13 is 0.07 to 0.3.

[0040] When the maximum thickness of the AlGaN layer 13 is within the above range and the Al component in the AlGaN layer 13 is within the above range, the quality of the obtained AlGaN layer 13 can be ensured to be good, and the matching degree between the AlGaN layer 13 and the n-type doped gallium nitride material is also relatively high, which can improve the crystal quality of the power diode. At the same time, the AlGaN layer 13 can play a role in stable transition and balance of the electron concentration to improve the overall quality and use stability of the finally obtained power diode.

[0041] It should be noted that the minimum thickness of the AlGaN layer 13 is less than the maximum thickness of the AlGaN layer 13, and the range of the minimum thickness of the AlGaN layer 13 can be 0 to 2 nm.

[0042] Exemplarily, the thickness of the portion of the AlGaN layer 13 that coincides with the orthographic projection of the Schottky electrode 2 on the substrate 11 is 0.5 to 2 nm.

[0043] When the thickness of the portion of the AlGaN layer 13 that coincides with the orthographic projection of the Schottky electrode 2 on the substrate 11 is within the above range, it can ensure that the AlGaN layer 13 plays a stable role in expanding the current conducted by the Schottky electrode 2, and can also effectively reduce the possibility of current breakdown caused by the Schottky electrode 2, effectively improving the reliability of the power diode.

[0044] It should be noted that the portion of the AlGaN layer 13 that coincides with the orthographic projection of the Schottky electrode 2 on the substrate 11 is the portion of the AlGaN layer 13 corresponding to the region where the orthographic projection of the AlGaN layer 13 on the surface of the substrate 11 coincides with the orthographic projection of the Schottky electrode 2 on the surface of the substrate 11.

[0045] In one implementation provided by the present disclosure, the interface between the AlGaN layer 13 and the N-type heavily doped gallium nitride layer 12 can be parallel to the surface of the substrate 11, and the interface between the AlGaN layer 13 and the N-type lightly doped gallium nitride layer 14 can be a plane with an acute angle with the surface of the substrate 11. The obtained power diode has good quality. In other implementations provided by the present disclosure, the interface between the AlGaN layer 13 and the N-type heavily doped gallium nitride layer 12 can also be set to have an acute angle with the surface of the substrate 11, and the present disclosure does not limit this.

[0046] Figure 2 is a schematic structural diagram of another power diode provided by an embodiment of the present disclosure. Refer to Figure 2 It can be seen that the power diode may include an epitaxial wafer 1, a Schottky electrode 2, and an ohmic electrode 3. The epitaxial wafer 1 includes a substrate 11 and a buffer layer 15, an undoped gallium nitride layer 16, an N-type heavily doped gallium nitride layer 12, an AlGaN layer 13, and an N-type lightly doped gallium nitride layer 14 that are sequentially stacked on the substrate 11. The surface of the N-type lightly doped gallium nitride layer 14 has a groove S extending to the N-type heavily doped gallium nitride layer 12. The Schottky electrode 2 is connected to the N-type lightly doped gallium nitride layer 14, and the ohmic electrode 3 is connected to the surface of the N-type heavily doped gallium nitride layer 12 exposed by the groove S. In the direction parallel to the surface of the substrate 11 and pointing from the Schottky electrode 2 to the ohmic electrode 3, the thickness of the AlGaN layer 13 increases.

[0047] It should be noted that Figure 2 the AlGaN layer 13 shown in Figure 1 can refer to the AlGaN layer 13 shown in

[0048] Optionally, the substrate 11 can be a sapphire substrate 11. It can ensure the growth quality and use quality of the power diode.

[0049] Exemplarily, the buffer layer 15 may include a gallium nitride buffer layer 15, and the thickness of the buffer layer 15 is 15 to 35 nm. It can effectively reduce the lattice mismatch between the substrate 11 and the gallium nitride material, and improve the quality and reliability of the obtained power diode.

[0050] Optionally, the thickness of the undoped gallium nitride layer 16 is 0.5 to 2 microns. It can effectively improve the quality of the N-type heavily doped gallium nitride layer 12 grown on the undoped gallium nitride layer 16.

[0051] Exemplarily, the thickness of the N-type heavily doped gallium nitride layer 12 is 1 to 5 microns. It can ensure that the obtained power diode has good quality.

[0052] Optionally, the n-type impurity doped in the N-type heavily doped gallium nitride layer 12 is Si, and the doping concentration of Si is 10 17 cm -3 -10 19 cm -3 . It can ensure that the obtained power diode has good quality.

[0053] Exemplarily, the thickness of the N-type lightly doped gallium nitride layer 14 is 1 to 5 microns. It can ensure that the obtained power diode has good quality.

[0054] Optionally, the n-type impurity doped in the N-type lightly doped gallium nitride layer 14 is Si, and the doping concentration of Si is 10 15 cm -3 -10 17 cm -3 . It can ensure that the obtained power diode has good quality.

[0055] Exemplarily, the Schottky electrode may include at least one layer of Cr, Al, Au, Ni, Pd. It ensures that the power diode has good quality.

[0056] Optionally, the ohmic electrode 3 may include at least one layer of Cr, Al, Au, Ni, Pd. It ensures that the power diode has good quality.

[0057] Figure 2 The addition of the buffer layer 15 and the undoped gallium nitride layer 16 can improve the quality of the obtained power diode to further improve the reliability of the obtained power diode.

[0058] It should be noted that Figure 2 is only one implementation manner of the power diode in the present disclosure. In other implementation manners provided by the present disclosure, the epitaxial wafer 1 of the power diode may also add different epitaxial layers on the basis of Figure 2 , and the present disclosure does not limit this.

[0059] Figure 3 is a flowchart of a method for manufacturing a power diode provided by an embodiment of the present disclosure. Referring to Figure 3 it can be seen that the embodiment of the present disclosure provides a method for manufacturing a power diode, and the manufacturing method includes:

[0060] S101: Provide a substrate.

[0061] S102: Grow an N-type heavily doped gallium nitride layer, an AlGaN layer, and an N-type lightly doped gallium nitride layer on the substrate in sequence. The surface of the N-type lightly doped gallium nitride layer has a groove extending to the N-type heavily doped gallium nitride layer. The Schottky electrode is connected to the N-type lightly doped gallium nitride layer, and the ohmic electrode is connected to the surface of the N-type heavily doped gallium nitride layer exposed by the groove. In the direction parallel to the surface of the substrate and pointing from the Schottky electrode to the ohmic electrode, the thickness of the AlGaN layer increases.

[0062] Adding an AlGaN layer between the N-type heavily doped gallium nitride layer and the N-type lightly doped gallium nitride layer can play a role in balancing the electron concentration to a certain extent, and under the action of the electric field during use, it can promote the stable flow of electrons between the Schottky electrode and the ohmic electrode. And the piezoelectric polarization between the AlGaN layer and the N-type lightly doped gallium nitride layer and the N-type heavily doped gallium nitride layer can promote the planar spreading of electrons, and the two-dimensional electron gas formed between the aluminum gallium nitride material and the gallium nitride material can also promote the movement and expansion of electrons, improving the electron expansion and increasing the effective downward injection of electrons, which can reduce the resistance of electron movement and reduce the resistance. And in the direction parallel to the surface of the substrate and pointing from the Schottky electrode to the ohmic electrode, the increase in the thickness of the AlGaN layer can play a role in controlling the movement rate of electrons at different positions in the power diode, reducing the probability of electrons moving vertically from the Schottky electrode to the ohmic electrode, making the movement paths of electrons in each part of the epitaxial wafer between the two electrodes approximately the same, and electrons can move more uniformly inside the power diode. It can effectively improve the uniformity of current distribution under the condition of equivalent on-resistance, improve the reverse breakdown voltage, and improve the reliability of the finally obtained power diode.

[0063] Optionally, in step S102, when growing the AlGaN layer on the N-type heavily doped gallium nitride layer, it includes:

[0064] Grow an AlGaN film on the N-type heavily doped gallium nitride layer; place the substrate in a dry etching device, adjust the substrate so that an acute angle is formed between the surface of the substrate and the horizontal plane, and etch the AlGaN film to obtain the AlGaN layer.

[0065] When it is necessary to control the shape of the surface of the AlGaN layer, the surface of the AlGaN layer can be processed by a dry etching device. When controlling the shape of the surface of the AlGaN layer to be obtained, by changing the angle between the surface of the substrate and the horizontal plane, the surface of the AlGaN layer can form an inclined plane, without the need to make large modifications to the parameters of the dry etching device, reducing the preparation cost of the AlGaN layer.

[0066] It should be noted that when the substrate is placed in the dry etching device, it can be supported by the bracket inside the dry etching device.

[0067] Optionally, the range of the acute angle between the surface of the substrate and the horizontal plane is 3° to 15°.

[0068] When the range of the acute angle between the surface of the substrate and the horizontal plane is within the above range, the substrate can be ensured to be relatively stable, and the slope of the surface of the AlGaN layer is relatively reasonable, so as to improve the quality of the obtained power diode.

[0069] Exemplarily, the growth temperature and growth pressure of the AlGaN layer can be 1000 to 1200 °C and 50 to 100 Torr respectively. The crystal quality of the obtained AlGaN layer can be ensured, and it can be ensured that the AlGaN layer obtained in a low-pressure environment is relatively dense, which is beneficial to making the resistances everywhere inside the power diode closer.

[0070] The structure of the power diode after performing step S102 can refer to Figure 1 the structure of the power diode shown in

[0071] Figure 4 is a flowchart of another method for preparing a power diode provided by an embodiment of the present disclosure. Referring to Figure 4 it can be seen that the method for preparing a power diode may include:

[0072] S201: Provide a substrate.

[0073] Among them, the substrate can be a sapphire substrate. It is easy to implement and manufacture.

[0074] Optionally, step S201 may further include: in a hydrogen atmosphere, the processing time of the substrate surface is 6 to 10 min.

[0075] Exemplarily, when processing the substrate surface, the temperature of the reaction chamber can be 1000 to 1200 °C, and the pressure of the reaction chamber can be 200 to 500 Torr.

[0076] In an implementation manner provided by the present disclosure, when processing the substrate, the temperature of the reaction chamber can also be 1100 °C, and the processing time of the substrate surface can be 8 min.

[0077] S202: Grow a buffer layer on the substrate.

[0078] Optionally, control the temperature of the reaction chamber to be 450°C - 600°C and the pressure of the reaction chamber to be 400 - 600 torr, and grow a gallium nitride buffer layer. A buffer layer with better quality can be obtained.

[0079] S203: Grow an undoped gallium nitride layer on the buffer layer.

[0080] The growth temperature and growth pressure of the undoped gallium nitride layer can be 1000 - 1200°C and 100 - 500 torr respectively. An undoped gallium nitride layer with better quality can be obtained.

[0081] S204: Grow an N-type heavily doped gallium nitride layer on the undoped gallium nitride layer.

[0082] Optionally, the growth temperature of the N-type heavily doped gallium nitride layer is between 1000°C - 1200°C, the pressure is between 100 Torr and 500 Torr, and the Si doping concentration is between 10 17 cm -3 -10 19 cm -3 . An N-type heavily doped gallium nitride layer with better quality can be obtained.

[0083] S205: Perform purging and heat preservation treatment on the reaction chamber.

[0084] Before growing the AlGaN layer, performing purging and heat preservation treatment on the reaction chamber can avoid the influence of the residues from the growth of the N-type heavily doped gallium nitride layer on the AlGaN layer. At the same time, it can also effectively release the stress accumulated during the growth of the N-type heavily doped gallium nitride layer, improve the quality of the obtained N-type heavily doped gallium nitride layer, and is also beneficial to providing a good foundation for the growth of the AlGaN layer.

[0085] It should be noted that the purging treatment and heat preservation treatment of the reaction chamber are carried out synchronously, and purging is performed during the heat preservation process. The temperature in the reaction chamber remains unchanged during the heat preservation treatment.

[0086] Optionally, perform purging and heat preservation treatment on the reaction chamber under the condition that the temperature is 800°C - 1600°C. It can ensure the stable release of stress in the N-type heavily doped gallium nitride layer.

[0087] Exemplarily, a carrier gas can be used to purge the reaction chamber. It can ensure the purity of the reaction chamber.

[0088] Optionally, the duration of purging and heat preservation treatment of the reaction chamber can be 5 - 20 min. It can ensure that the quality of the subsequently grown AlGaN layer is better.

[0089] S206: Grow an AlGaN layer on the N-type heavily doped gallium nitride layer.

[0090] Step S206 can refer to Figure 3 Step S102 shown in [reference] and will not be elaborated here.

[0091] S207: Purge and heat-insulate the reaction chamber.

[0092] Step S207 can refer to step S205. The reaction chamber can be cleaned to effectively release the stress accumulated inside the power diode.

[0093] S208: Grow an N-type lightly doped gallium nitride layer on the AlGaN layer.

[0094] Optionally, the growth temperature of the N-type lightly doped gallium nitride layer is between 1000°C and 1200°C, the pressure is between 100 Torr and 500 Torr, and the Si doping concentration is between 10 15 cm -3 -10 17 cm -3 . A better-quality N-type lightly doped gallium nitride layer can be obtained.

[0095] It should be noted that the surface of the N-type lightly doped gallium nitride layer far from the substrate can be made parallel to the surface of the substrate by controlling the growth conditions, or in combination with a photolithography process to achieve a structure where the surface of the N-type lightly doped gallium nitride layer far from the substrate is parallel to the surface of the substrate.

[0096] S209: Form a groove on the N-type lightly doped gallium nitride layer that extends to the N-type heavily doped gallium nitride layer.

[0097] In step S209, the groove can be prepared by a photolithography process.

[0098] S210: Form a Schottky electrode on the surface of the N-type lightly doped gallium nitride layer, form an ohmic electrode on the surface of the N-type heavily doped gallium nitride layer exposed by the groove, and in the direction parallel to the surface of the substrate and pointing from the Schottky electrode to the ohmic electrode, the thickness of the AlGaN layer increases.

[0099] It should be noted that the electrodes can both be obtained by evaporation or sputtering. The structure of the power diode after performing step S210 can refer to Figure 2 the structure of the power diode shown in [reference].

[0100] It should be noted that in the embodiments of the present disclosure, a Veeco K465i or C4 or RB MOCVD (Metal Organic Chemical Vapor Deposition) device is used to implement the growth method of light-emitting diodes. High-purity H2 (hydrogen) or high-purity N2 (nitrogen) or a mixed gas of high-purity H2 and high-purity N2 is used as the carrier gas, high-purity NH3 is used as the N source, trimethylgallium (TMGa) and triethylgallium (TEGa) are used as the gallium sources, trimethylindium (TMIn) is used as the indium source, silane (SiH4) is used as the N-type dopant, trimethylaluminum (TMAl) is used as the aluminum source, and bis(cyclopentadienyl)magnesium (CP2Mg) is used as the P-type dopant.

[0101] The above are only optional embodiments of the present disclosure and are not intended to limit the present disclosure. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present disclosure shall be included within the protection scope of the present disclosure.

Claims

1. A power diode, characterized in that, The power diode includes an epitaxial wafer, a Schottky electrode and an ohmic electrode. The epitaxial wafer includes a substrate and an N-type heavily doped gallium nitride layer, an AlGaN layer and an N-type lightly doped gallium nitride layer that are sequentially stacked on the substrate. The surface of the N-type lightly doped gallium nitride layer has a groove extending to the N-type heavily doped gallium nitride layer. The Schottky electrode is connected to the N-type lightly doped gallium nitride layer, and the ohmic electrode is connected to the surface of the N-type heavily doped gallium nitride layer exposed by the groove. In the direction parallel to the surface of the substrate and pointing from the Schottky electrode to the ohmic electrode, the thickness of the AlGaN layer increases.

2. The power diode according to claim 1, wherein The difference between the maximum thickness and the minimum thickness of the AlGaN layer is 1 - 12 nm.

3. The power diode according to claim 1, wherein The maximum thickness of the AlGaN layer is 3 - 15 nm, and the Al component range in the AlGaN layer is 0.07 - 0.

3.

4. The power diode according to any one of claims 1 to 3, characterized in that, In the direction parallel to the surface of the substrate and pointing from the Schottky electrode to the ohmic electrode, the thickness of the AlGaN layer increases linearly.

5. The power diode according to any one of claims 1 to 3, characterized in that, The thickness corresponding to the part of the AlGaN layer that coincides with the positive projection of the Schottky electrode on the substrate is 0.5 - 2 nm.

6. A method for preparing a power diode, characterized in that, The preparation method includes: Providing a substrate; Growing an N-type heavily doped gallium nitride layer, an AlGaN layer and an N-type lightly doped gallium nitride layer on the substrate in sequence. The surface of the N-type lightly doped gallium nitride layer has a groove extending to the N-type heavily doped gallium nitride layer. The Schottky electrode is connected to the N-type lightly doped gallium nitride layer, and the ohmic electrode is connected to the surface of the N-type heavily doped gallium nitride layer exposed by the groove. In the direction parallel to the surface of the substrate and pointing from the Schottky electrode to the ohmic electrode, the thickness of the AlGaN layer increases.

7. The manufacturing method of the power diode according to claim 6, wherein, Growing an AlGaN layer on the N-type heavily doped gallium nitride layer includes: Growing an AlGaN film on the N-type heavily doped gallium nitride layer; Placing the substrate in a dry etching device, adjusting the substrate so that an acute angle is formed between the surface of the substrate and the horizontal plane, and etching the AlGaN film to obtain the AlGaN layer.

8. The manufacturing method of the power diode according to claim 7, characterized in that, The range of the acute angle between the surface of the substrate and the horizontal plane is 3° - 15°.

9. The manufacturing method of the power diode according to any one of claims 6 to 8, characterized in that The preparation method further includes: After growing the N-type heavily doped gallium nitride layer on the substrate and before growing the AlGaN layer on the N-type heavily doped gallium nitride layer, purging and heat-preserving the reaction chamber.

10. The manufacturing method of the power diode according to claim 9, characterized in that, Purging and heat-preserving the reaction chamber under the condition that the temperature is 800°C - 1600°C.

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