Power semiconductor device and preparation method thereof

Abstract

The present disclosure provides a power semiconductor device and a preparation method thereof, belonging to the field of semiconductor technology. The power semiconductor device includes: a substrate, a first GaN layer, a second GaN layer, an AlGaN layer, an ohmic electrode, and a Schottky electrode; the first GaN layer, the second GaN layer, and the AlGaN layer are sequentially stacked on the supporting surface of the substrate, the Schottky electrode is located on the side of the AlGaN layer away from the substrate, the surface of the AlGaN layer has a groove exposing the first GaN layer, the ohmic electrode is located in the groove and is connected to the first GaN layer; the surface of the second GaN layer away from the substrate has a plurality of spaced convex structures, and the convex structures are embedded in the AlGaN layer. The present disclosure can improve the problem of uneven current distribution and current congestion in power semiconductor devices, so as to avoid easy damage to power semiconductor devices.

Description

Technical Field

[0001] The present disclosure relates to the field of semiconductor technology, and in particular to a power semiconductor device and a method for preparing the same. Background Art

[0002] Power semiconductor devices, also known as power electronic devices, are high-power electronic devices used in power conversion and control circuits in power equipment. Due to the excellent physical and chemical properties of GaN, GaN-based power semiconductor devices can significantly improve conversion efficiency and reduce power loss.

[0003] In related art, a GaN-based power semiconductor device includes a substrate, a first GaN layer, a second GaN layer, an ohmic electrode, and a Schottky electrode, which are stacked in sequence. The ohmic electrode is connected to the first GaN layer, and the Schottky electrode is connected to the second GaN layer to form a power semiconductor device.

[0004] However, there is a problem of uneven current distribution in power semiconductor devices, which can easily lead to current congestion, causing serious heating of the power semiconductor devices. In addition, the electric field strength in the current congestion area is high, which can easily break down the power semiconductor devices. Summary of the Invention

[0005] The present disclosure provides a power semiconductor device and a method for manufacturing the same, which can improve the problem of uneven current distribution and current congestion in the power semiconductor device, thereby preventing the power semiconductor device from being easily damaged. The technical solution is as follows:

[0006] An embodiment of the present disclosure provides a power semiconductor device, which includes: a substrate, a first GaN layer, a second GaN layer, an AlGaN layer, an ohmic electrode, and a Schottky electrode; the first GaN layer, the second GaN layer, and the AlGaN layer are stacked in sequence on a supporting surface of the substrate, the Schottky electrode is located on a side of the AlGaN layer away from the substrate, the surface of the AlGaN layer has a groove exposing the first GaN layer, the ohmic electrode is located in the groove and is connected to the first GaN layer; the surface of the second GaN layer away from the substrate has a plurality of spaced-apart protrusion structures, and the protrusion structures are embedded in the AlGaN layer.

[0007] In an implementation of the embodiment of the present disclosure, on the surface of the second GaN layer away from the substrate, the distribution density of the protruding structures gradually increases in a direction from the Schottky electrode to the ohmic electrode.

[0008] In another implementation of the embodiment of the present disclosure, in the direction from the Schottky electrode to the ohmic electrode, the ratio of the maximum distance between two adjacent protrusion structures to the minimum distance between two adjacent protrusion structures is 40:3.

[0009] In another implementation of the embodiment of the present disclosure, the height of the protruding structure is 20nm to 80nm, and the width is 200nm to 500nm. The height direction of the protruding structure is perpendicular to the supporting surface of the substrate, and the width direction is parallel to the supporting surface of the substrate.

[0010] In another implementation of the embodiment of the present disclosure, the power semiconductor device further includes a third GaN layer, which is located on a surface of the AlGaN layer away from the substrate; the first GaN layer, the second GaN layer, and the third GaN layer are all doped with Si, and the doping concentration of the first GaN layer and the doping concentration of the third GaN layer are both higher than that of the second GaN layer.

[0011] In another implementation of the embodiment of the present disclosure, the doping concentration of the first GaN layer is 10 17 cm -3 to 10 19 cm -3 , the doping concentration of the second GaN layer is 10 15 cm -3 to 10 17 cm -3 The doping concentration of the third GaN layer is 5×10 15 cm -3 to 5×10 17 cm -3 .

[0012] In another implementation of the embodiment of the present disclosure, the thickness of the AlGaN layer is not greater than the height of the protruding structure.

[0013] In another implementation of the embodiment of the present disclosure, the thickness of the AlGaN layer is 5 nm to 20 nm, and the thickness of the third GaN layer is greater than 75 nm.

[0014] In another implementation of the embodiment of the present disclosure, the thickness of the first GaN layer is 1 μm to 5 μm, and the thickness of the second GaN layer is 1 μm to 5 μm.

[0015] An embodiment of the present disclosure provides a method for preparing a power semiconductor device, the method comprising: providing a substrate; sequentially forming a first GaN layer, a second GaN layer, and an AlGaN layer on the substrate, wherein a surface of the second GaN layer away from the substrate has a plurality of spaced-apart raised structures, and the raised structures are embedded in the AlGaN layer; etching the AlGaN layer to form a groove exposing the first GaN layer; forming a Schottky electrode on the AlGaN layer, and forming an ohmic electrode in the groove, wherein the ohmic electrode is connected to the first GaN layer.

[0016] The beneficial effects of the technical solutions provided by the embodiments of the present disclosure include at least:

[0017] The power semiconductor device provided by the embodiment of the present disclosure includes a substrate, a first GaN layer, a second GaN layer and an AlGaN layer stacked in sequence, a Schottky electrode is located on the AlGaN layer and connected to the second GaN layer, and an ohmic electrode is connected to the first GaN layer through a groove to form a power semiconductor device.

[0018] The second GaN layer has multiple raised structures on its surface near the AlGaN layer, which are arranged at intervals and embedded in the AlGaN layer. This allows the second GaN layer and the AlGaN layer to form a two-dimensional electron gas distributed in three dimensions, allowing electrons to expand within the plane of the second GaN layer, thereby increasing the electron injection efficiency and making the current more evenly distributed on the second GaN layer. This also makes the current distribution in the power semiconductor device more uniform, avoiding current congestion in local areas of the power semiconductor device, improving the problem of severe heating of the power semiconductor device, and preventing the power semiconductor device from being broken down due to high electric field strength in the current congested area, thereby improving reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0020] Figure 1 is a schematic structural diagram of a power semiconductor device provided by an embodiment of the present disclosure;

[0021] Figure 2 is a partial schematic diagram of a power semiconductor device provided by an embodiment of the present disclosure;

[0022] Figure 3 is a top view of a second GaN layer provided by an embodiment of the present disclosure;

[0023] Figure 4 This is a flow chart of a method for preparing a power semiconductor device provided by an embodiment of the present disclosure.

[0024] The descriptions of the marks in the figure are as follows:

[0025] 10. substrate; 11. buffer layer; 12. u-type GaN layer;

[0026] 21. First GaN layer; 22. Second GaN layer; 221. Protrusion structure; 23. AlGaN layer; 24. Third GaN layer;

[0027] 31. Ohmic electrode; 32. Schottky electrode;

[0028] 40. Groove. DETAILED DESCRIPTION

[0029] In order to make the objectives, technical solutions and advantages of the present disclosure more clear, the embodiments of the present disclosure will be further described in detail below with reference to the accompanying drawings.

[0030] Unless otherwise defined, the technical or scientific terms used herein shall have the ordinary meaning understood by a person of ordinary skill in the art to which this disclosure pertains. The terms "first," "second," "third," and similar words used in the patent specification and claims of this disclosure do not indicate any order, quantity, or importance, but are merely used to distinguish between different components. Similarly, terms such as "a" or "an" do not indicate a quantitative limitation, but rather indicate the presence of at least one. Terms such as "include" or "comprise" mean that the elements or objects preceding "include" or "comprises" encompass the elements or objects listed after "include" or "comprises," and their equivalents, and do not exclude other elements or objects. Terms such as "connected" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," "right," "top," and "bottom" are used only to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0031] Figure 1 Schematic diagram of a power semiconductor device provided by an embodiment of the present disclosure. Figure 1 As shown, the power semiconductor device includes: a substrate 10 , a first GaN layer 21 , a second GaN layer 22 , an AlGaN layer 23 , an ohmic electrode 31 and a Schottky electrode 32 .

[0032] like Figure 1As shown, the first GaN layer 21, the second GaN layer 22 and the AlGaN layer 23 are stacked in sequence on the supporting surface of the substrate 10, the Schottky electrode 32 is located on the side of the AlGaN layer 23 away from the substrate 10, and the surface of the AlGaN layer 23 has a groove 40 exposing the first GaN layer 21, and the ohmic electrode 31 is located in the groove 40 and is connected to the first GaN layer 21.

[0033] Figure 2 FIG is a partial schematic diagram of a power semiconductor device provided by an embodiment of the present disclosure. Figure 2 As shown, the surface of the second GaN layer 22 away from the substrate 10 has a plurality of spaced-apart protrusion structures 221 , and the protrusion structures 221 are embedded in the AlGaN layer 23 .

[0034] The power semiconductor device provided by the embodiment of the present disclosure includes a substrate 10, a first GaN layer 21, a second GaN layer 22 and an AlGaN layer 23 stacked in sequence, a Schottky electrode 32 is located on the AlGaN layer 23 and is connected to the second GaN layer 22, and the ohmic electrode 31 is connected to the first GaN layer 21 through a groove 40 to form a power semiconductor device.

[0035] The second GaN layer 22 has a plurality of raised structures 221 on its surface near the AlGaN layer 23. The plurality of raised structures 221 are arranged at intervals and embedded in the AlGaN layer 23. In this way, the second GaN layer 22 and the AlGaN layer 23 can form a two-dimensional electron gas distributed in a three-dimensional space, allowing electrons to expand within the plane of the second GaN layer 22, thereby increasing the electron injection efficiency and making the current more evenly distributed on the second GaN layer 22. This also makes the current distribution in the power semiconductor device more uniform, avoiding current congestion in local areas of the power semiconductor device, improving the problem of severe heating of the power semiconductor device, and preventing the power semiconductor device from being broken down due to the high electric field strength in the current congested area, thereby improving reliability.

[0036] In the embodiment of the present disclosure, the substrate 10 may be a sapphire substrate 10. Sapphire material is relatively hard and has relatively stable chemical properties, which enables the power semiconductor device to have good stability.

[0037] Figure 3 FIG. 2 is a top view of a second GaN layer 22 provided in an embodiment of the present disclosure. Figure 2 、 3 As shown, on the surface of the second GaN layer 22 away from the substrate 10 , the distribution density of the protrusion structures 221 gradually increases in the direction from the Schottky electrode 32 to the ohmic electrode 31 .

[0038] The distribution density of the protrusions 221 refers to the number of protrusions 221 per unit area on the surface of the second GaN layer 22 away from the substrate 10. A higher distribution density indicates a greater number of protrusions 221 per unit area and a smaller spacing between adjacent protrusions 221. A lower distribution density indicates a smaller number of protrusions 221 per unit area.

[0039] Because the current density in the area near the ohmic electrode 31 in a power semiconductor device is relatively high, the current congestion problem in the area near the ohmic electrode 31 is more serious. The denser the distribution of the protruding structures 221, the better the current spreading effect. Therefore, by setting the distribution density of the protruding structures 221 near the ohmic electrode 31 to be relatively high, the current congestion problem in the area near the ohmic electrode 31 is alleviated. At the same time, the problem of severe heating in the area near the ohmic electrode 31 is avoided, and the current congestion area is effectively prevented from being broken down due to the high electric field strength, thereby improving reliability.

[0040] In the above implementation, the distribution density of the protruding structure 221 gradually increases from the Schottky electrode 32 to the ohmic electrode 31, so that the current expansion effect in the area close to the ohmic electrode 31 is the best, which can ensure the effect of current expansion and alleviate the current congestion in the area close to the ohmic electrode 31 to the greatest extent. As it gradually approaches the Schottky electrode 32, the problem of current congestion gradually weakens. A certain amount of protruding structures 221 are set on the surface of the second GaN to have a certain current expansion effect, so that the current can spread and the current is evenly distributed on the second GaN layer 22. In addition, this gradual change in distribution density can make the current expansion process more moderate, avoiding the distribution density change of the protruding structure 221 being too drastic and affecting the current expansion, thereby affecting the uniformity of the current distribution.

[0041] For example, in the direction from the Schottky electrode 32 to the ohmic electrode 31 , the ratio of the maximum distance between two adjacent protrusion structures 221 to the minimum distance between two adjacent protrusion structures 221 is 40:3.

[0042] In the embodiment of the present disclosure, the distance between two adjacent protrusion structures 221 in the direction from the Schottky electrode 32 to the ohmic electrode 31 may be 0.15 um to 2 um.

[0043] like Figure 2 As shown, the maximum spacing L1 is the spacing between the two protruding structures 221 closest to the region where the Schottky electrode 32 is located. The minimum spacing L2 is the spacing between the two protruding structures 221 closest to the region where the ohmic electrode 31 is located.

[0044] In the above implementation, the ratio of the maximum spacing between two adjacent protrusions 221 to the minimum spacing between two adjacent protrusions 221 is set to 40:3. This keeps the distribution density of the protrusions 221 within a reasonable range on the second GaN surface between the ohmic electrode 31 and the Schottky electrode 32, preventing large variations in the distribution density of the protrusions 221, which could affect the uniformity of current spreading.

[0045] In the above implementation, the distribution density of the protruding structure 221 increases linearly from the Schottky electrode 32 to the ohmic electrode 31, which can make the current expansion process more gentle and avoid the distribution density of the protruding structure 221 changing too drastically to affect the current expansion and further affect the uniformity of the current distribution.

[0046] In the embodiment of the present disclosure, Figure 3 As shown, in the direction from the Schottky electrode 32 to the ohmic electrode 31, the distance H1 between two adjacent protrusion structures 221 changes gradually, and in the direction perpendicular to the Schottky electrode 32 to the ohmic electrode 31, the distance H2 between two adjacent protrusion structures 221 also changes gradually.

[0047] In some other implementations, the distance between two adjacent protrusion structures 221 changes gradually in the direction from the Schottky electrode 32 to the ohmic electrode 31, while the distance between two adjacent protrusion structures 221 in the direction perpendicular to the Schottky electrode 32 to the ohmic electrode 31 is constant.

[0048] In some other implementations, the distance between two adjacent protrusion structures 221 in the direction perpendicular to the Schottky electrode 32 to the ohmic electrode 31 is constant, while the distance between two adjacent protrusion structures 221 in the direction perpendicular to the Schottky electrode 32 to the ohmic electrode 31 gradually changes.

[0049] It should be noted that the specific distribution of the protruding structures can be selected according to actual conditions and is not limited in the embodiments of the present disclosure.

[0050] Optionally, the height of the protruding structure 221 is 20 nm to 80 nm, and the width is 200 nm to 500 nm. The height direction of the protruding structure 221 is perpendicular to the supporting surface of the substrate 10 , and the width direction is parallel to the supporting surface of the substrate 10 .

[0051] By setting the height of the protruding structure 221 within the above range and setting the width of the protruding structure 221 within the above range, the size of the protruding structure 221 can be reasonably controlled to avoid the protruding structure 221 being too large or too small, thereby affecting the effect of the second GaN layer 22 and the AlGaN layer 23 in forming a three-dimensionally distributed two-dimensional electron gas.

[0052] For example, Figure 2 、 3 As shown, the protrusion structure 221 is a cylindrical protrusion. The length of the cylindrical protrusion in the direction perpendicular to the substrate 10, that is, the height of the cylindrical protrusion is 50 nm, and the length of the cylindrical protrusion in the direction parallel to the substrate 10, that is, the diameter of the cylindrical protrusion is 300 nm.

[0053] Alternatively, as Figure 1 As shown, the power semiconductor device further includes a third GaN layer 24 , which is located on the surface of the AlGaN layer 23 .

[0054] The first GaN layer 21 , the second GaN layer 22 and the third GaN layer 24 are all doped with Si, and the doping concentration of the first GaN layer 21 and the doping concentration of the third GaN layer 24 are both higher than that of the second GaN layer 22 .

[0055] Exemplarily, the doping concentration of the first GaN layer 21 is higher than the doping concentration of the third GaN layer 24 , and the doping concentration of the third GaN layer 24 is higher than the doping concentration of the second GaN layer 22 .

[0056] By providing the third GaN layer 24 and setting the doping concentration of Si in the third GaN layer 24 higher than the doping concentration of Si in the second GaN layer 22, carriers can be quickly transferred from the third GaN layer 24 to the AlGaN layer 23 and the first GaN layer 21, thereby improving the carrier transmission efficiency.

[0057] Moreover, the doping concentration of Si doped in the first GaN layer 21 is higher than the doping concentration of Si doped in the second GaN layer 22 and the third GaN layer 24, so that carriers can only flow from the first GaN layer 21 to the second GaN layer 22 and the third GaN layer 24, thereby forming a unidirectional conduction and constituting a diode device.

[0058] Optionally, the doping concentration of the first GaN layer 21 is 10 17 cm -3 to 10 19 cm -3 , the doping concentration of the second GaN layer 22 is 10 15 cm -3 to 10 17 cm -3 The doping concentration of the third GaN layer 24 is 5×10 15 cm -3 to 5×10 17 cm -3 .

[0059] As an example, in the embodiment of the present disclosure, the doping concentration of the first GaN layer 21 is 10 18 cm-3 , the doping concentration of the second GaN layer 22 is 10 17 cm -3 The doping concentration of the third GaN layer 24 is 5×10 17 cm -3 .

[0060] In the embodiment of the present disclosure, the first GaN layer 21 , the second GaN layer 22 and the third GaN layer 24 are all doped with Si, that is, the first GaN layer 21 , the second GaN layer 22 and the third GaN layer 24 are all n-type layers.

[0061] Alternatively, as Figure 1 、 2 As shown, the thickness of the AlGaN layer 23 is no greater than the height of the protruding structure 221 , and the third GaN layer 24 covers the protruding structure 221 and extends to the surface of the AlGaN layer 23 .

[0062] In the above implementation, the thickness of the AlGaN layer 23 does not exceed the height of the protruding structure 221, that is, after the protruding structure 221 is embedded in the AlGaN layer 23, the end of the protruding structure 221 is still located outside the AlGaN layer 23, and the part located outside the AlGaN layer 23 is covered by the third GaN layer 24 to form a flat film structure of the second GaN layer 22, the AlGaN layer 23 and the third GaN layer 24.

[0063] By inserting the protruding structure 221 into the third GaN layer 24 , the third GaN layer 24 is connected to the protruding structure 221 in addition to the AlGaN layer 23 , thereby improving the connection reliability of the third GaN layer 24 and preventing it from falling off.

[0064] In the disclosed embodiment, the height of the protruding structure 221 is greater than the designed height of the AlGaN layer 23. This ensures that the AlGaN layer 23 is completely deposited on the surface of the second GaN layer 22, ensuring that the protruding structure 221 is completely interspersed with the AlGaN layer 23. This fully utilizes the AlGaN layer 23 and allows the second GaN layer 22 and the AlGaN layer 23 to form a three-dimensionally distributed two-dimensional electron gas.

[0065] Optionally, the thickness of the AlGaN layer 23 is 5 nm to 20 nm, and the thickness of the third GaN layer 24 is greater than 75 nm.

[0066] By setting the thickness of the AlGaN layer 23 within the above range, it is possible to avoid that the AlGaN layer 23 is too thin and the current spreading performance of the AlGaN layer 23 is reduced, and it is also possible to avoid that the AlGaN layer 23 is too thin and the manufacturing cost is increased.

[0067] As an example, in the embodiment of the present disclosure, the thickness of the AlGaN layer 23 is 10 nm, and the thickness of the third GaN layer 24 may be 100 nm.

[0068] Optionally, the thickness of the first GaN layer 21 is 1 μm to 5 μm, and the thickness of the second GaN layer 22 is 1 μm to 5 μm.

[0069] As an example, in the embodiment of the present disclosure, the thickness of the first GaN layer 21 is 3 μm, and the thickness of the second GaN layer 22 is 3 μm.

[0070] In the embodiment of the present disclosure, Figure 1 As shown, a buffer layer 11 and a u-type GaN layer 12 are further stacked in sequence between the substrate 10 and the first GaN layer 21 .

[0071] Providing the buffer layer 11 is beneficial to the growth of the GaN layer in the subsequent film layer, and can further improve the crystal quality of the GaN layer, thereby ensuring the performance of the power semiconductor device.

[0072] Alternatively, the buffer layer 11 may be a GaN layer. Exemplarily, the thickness of the buffer layer 11 may be 15 nm to 35 nm. For example, the thickness of the buffer layer 11 is 20 nm.

[0073] For example, the thickness of the u-type GaN layer 12 may be 0.5 μm to 2 μm. For example, the thickness of the u-type GaN layer 12 may be 1 μm.

[0074] In the embodiment of the present disclosure, the Schottky electrode 32 and the ohmic electrode 31 may be made of aluminum, copper, tungsten, molybdenum, gold, titanium, neodymium, palladium or cesium.

[0075] Exemplarily, the Schottky electrode 32 and the ohmic electrode 31 are made of gold, with a thickness of 50 nm to 500 nm.

[0076] Figure 4 This is a flow chart of a method for preparing a power semiconductor device provided by an embodiment of the present disclosure. Figure 4 As shown, this preparation method is suitable for preparing Figure 1 The power semiconductor device shown includes:

[0077] Step S11: providing a substrate 10;

[0078] Step S12 : forming a first GaN layer 21 , a second GaN layer 22 and an AlGaN layer 23 in sequence on the substrate 10 .

[0079] The surface of the second GaN layer 22 away from the substrate 10 has a plurality of spaced-apart protrusion structures 221 , and the protrusion structures 221 are embedded in the AlGaN layer 23 .

[0080] Step S13 : etching the AlGaN layer 23 to form a groove 40 exposing the first GaN layer 21 .

[0081] Step S14 : forming a Schottky electrode 32 on the AlGaN layer 23 , and forming an ohmic electrode 31 in the groove 40 , wherein the ohmic electrode 31 is connected to the first GaN layer 21 .

[0082] In the power semiconductor device fabricated according to the disclosed embodiment, the second GaN layer 22 has a plurality of raised structures 221 on its surface near the AlGaN layer 23. These raised structures 221 are arranged at intervals and embedded in the AlGaN layer 23. This allows the second GaN layer 22 and the AlGaN layer 23 to form a three-dimensionally distributed two-dimensional electron gas, allowing electrons to expand within the plane of the second GaN layer 22, thereby increasing electron injection efficiency and distributing current more evenly across the second GaN layer 22. This also results in a more uniform current distribution within the power semiconductor device, avoiding current congestion in localized areas of the power semiconductor device, improving the severe heating problem of the power semiconductor device, and preventing breakdown of the power semiconductor device due to high electric field strength in current-congested areas, thereby improving reliability.

[0083] In step S11 , the substrate 10 may be a sapphire substrate 10 .

[0084] The sapphire substrate 10 may be pre-treated by annealing it in a hydrogen atmosphere for 5 to 10 minutes, cleaning the surface of the substrate 10 while controlling the annealing temperature between 1000° C. and 1200° C., and then performing a nitridation treatment.

[0085] As an example, in the embodiment of the present disclosure, the sapphire substrate 10 is placed in a hydrogen atmosphere and annealed for 8 minutes at an annealing temperature of 1100°C.

[0086] Before step S12 , the process further includes: sequentially growing a buffer layer 11 and a u-type GaN layer 12 on the substrate 10 .

[0087] When growing the buffer layer 11 , the growth temperature is controlled to be 400° C. to 600° C., and the growth pressure is controlled to be 400 Torr to 600 Torr.

[0088] The buffer layer 11 may be a GaN layer, and the thickness of the grown buffer layer 11 may be 15 nm to 35 nm. For example, the thickness of the buffer layer 11 is 20 nm.

[0089] After the buffer layer 11 is grown, the buffer layer 11 may be annealed.

[0090] During the annealing process, the annealing temperature is controlled to be 1000° C. to 1200° C., the pressure is controlled to be 400 Torr to 600 Torr, and the annealing time is controlled to be 5 min to 10 min.

[0091] As an example, in the embodiment of the present disclosure, the annealing temperature is 1100° C., the pressure is controlled to be 500 Torr, and the annealing time is controlled to be 5 minutes.

[0092] When growing the u-type GaN layer 12 , the growth temperature is controlled to be 1000° C. to 1100° C., and the growth pressure is controlled to be 100 Torr to 500 Torr.

[0093] The thickness of the grown u-type GaN layer 12 may be 0.5 μm to 2 μm. For example, the thickness of the u-type GaN layer 12 may be 1 μm.

[0094] Forming the first GaN layer 21 in step S12 may include: controlling the growth temperature to be 1000° C. to 1200° C., controlling the growth pressure to be 100 Torr to 500 Torr, and forming the first GaN layer 21 on the surface of the u-type GaN layer 12 .

[0095] The first GaN layer 21 is a Si-doped film layer, and the Si doping concentration is 10 17 cm -3 to 10 19 cm -3 For example, the doping concentration of the first GaN layer 21 may be 10 18 cm -3 .

[0096] Optionally, the thickness of the first GaN layer 21 is 1 μm to 5 μm. As an example, in the embodiment of the present disclosure, the thickness of the first GaN layer 21 is 3 μm.

[0097] Forming the second GaN layer 22 in step S12 may include: controlling the growth temperature to be 1000° C. to 1200° C., controlling the growth pressure to be 100 Torr to 500 Torr, and forming the second GaN layer 22 on the surface of the first GaN layer 21 .

[0098] The second GaN layer 22 is a Si-doped film layer, and the Si doping concentration is 10 15 cm -3 to 10 17 cm -3 For example, the doping concentration of the second GaN layer 22 may be 10 17 cm -3 .

[0099] Optionally, the thickness of the second GaN layer 22 is 1 μm to 5 μm. As an example, in the embodiment of the present disclosure, the thickness of the second GaN layer 22 is 3 μm.

[0100] After growing the second GaN layer 22 , the method further includes etching the surface of the second GaN layer 22 away from the substrate 10 to form a plurality of convex structures 221 arranged at intervals on the surface of the second GaN layer 22 away from the substrate 10 .

[0101] The protrusion structure 221 may be a cylindrical protrusion, and the length of the protrusion structure 221 in a direction perpendicular to the substrate 10 is 20 nm to 80 nm, and the length of the protrusion structure 221 in a direction parallel to the substrate 10 is 200 nm to 500 nm.

[0102] For example, Figure 2 、 3 As shown, the length of the cylindrical protrusion in the direction perpendicular to the substrate 10, that is, the height of the cylindrical protrusion is 50 nm, and the length of the cylindrical protrusion in the direction parallel to the substrate 10, that is, the diameter of the cylindrical protrusion is 300 nm.

[0103] Exemplarily, the distribution density of the protruding structures 221 changes linearly, and the distribution density in the region close to the ohmic electrode 31 is twice the distribution density in the region close to the Schottky electrode 32 .

[0104] Setting the distribution density to change linearly can make the current spreading process more gentle, and avoid the distribution density of the protruding structures 221 changing too drastically to affect the current spreading, thereby affecting the uniformity of the current distribution.

[0105] In the above implementation, the distribution density in the area near the ohmic electrode 31 is set to twice the distribution density in the area near the Schottky electrode 32. The maximum difference in distribution density is controlled to not exceed two times. Thus, on the surface of the second GaN, within the range between the ohmic electrode 31 and the Schottky electrode 32, the distribution density of the protruding structures 221 is controlled within a two-fold range. This prevents excessive differences in the distribution density of the protruding structures 221, which could affect the uniformity of current spreading.

[0106] Forming the AlGaN layer 23 in step S12 may include: controlling the growth temperature to be between 1000° C. and 1200° C., controlling the growth pressure to be between 50 Torr and 150 Torr, and depositing the AlGaN layer 23 on the surface of the second GaN layer 22 .

[0107] The thickness of the AlGaN layer 23 is 5 nm to 20 nm. As an example, in the embodiment of the present disclosure, the thickness of the AlGaN layer 23 is 10 nm.

[0108] Optionally, the thickness of the deposited AlGaN layer 23 is no greater than the height of the protruding structure 221 .

[0109] In the disclosed embodiment, the height of the protruding structure 221 is greater than the designed height of the AlGaN layer 23. This ensures that the AlGaN layer 23 is completely deposited on the surface of the second GaN layer 22, ensuring that the protruding structure 221 is completely interspersed with the AlGaN layer 23. This fully utilizes the AlGaN layer 23 and allows the second GaN layer 22 and the AlGaN layer 23 to form a three-dimensionally distributed two-dimensional electron gas.

[0110] Optionally, the molar content of Al in the AlGaN layer 23 is 0.15 to 0.25.

[0111] Step S12 may further include: controlling the growth temperature to be 1000° C. to 1200° C., controlling the growth pressure to be 100 Torr to 500 Torr, and growing a third GaN layer 24 on the surface of the AlGaN layer 23 until the third GaN layer 24 covers the protruding structure 221 .

[0112] The thickness of the third GaN layer 24 is greater than 75 nm. For example, the thickness of the third GaN layer 24 may be 100 nm.

[0113] Optionally, the doping concentration of the third GaN layer 24 is 5×10 15 cm -3 to 5×10 17 cm -3 For example, the doping concentration of the third GaN layer 24 is 5×10 17 cm -3 .

[0114] The etching to form the groove 40 in step S13 may include the following steps:

[0115] In the first step, a photoresist with a certain pattern is formed on the third GaN layer 24 using a photolithography technique. The photoresist is disposed on an area of ​​the third GaN layer 24 except an area where the groove 40 is located.

[0116] In the second step, the third GaN layer 24 , the AlGaN layer 23 and the second GaN layer 22 not covered by the photoresist are dry-etched to form a groove 40 .

[0117] In specific implementation, the photoresist of a certain pattern formed by photolithography technology may include:

[0118] Lay a layer of photoresist; expose the photoresist through a mask with a certain pattern; immerse the exposed photoresist in a developer to dissolve part of the photoresist, leaving the photoresist with the desired pattern.

[0119] Step S14 : forming a Schottky electrode 32 on the AlGaN layer 23 , and forming an ohmic electrode 31 in the groove 40 , wherein the ohmic electrode 31 is connected to the first GaN layer 21 .

[0120] The Schottky electrode 32 and the ohmic electrode 31 may be made of aluminum, copper, tungsten, molybdenum, gold, titanium, neodymium, palladium or cesium.

[0121] The above does not limit the present disclosure in any form. Although the present disclosure has been disclosed as above through the embodiments, it is not intended to limit the present disclosure. Any technician familiar with the profession can make slight changes or modifications to equivalent embodiments with equivalent changes using the technical content disclosed above without departing from the scope of the technical solution of the present disclosure. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present disclosure without departing from the content of the technical solution of the present disclosure are still within the scope of the technical solution of the present disclosure.

Claims

1. A power semiconductor device, characterized in that: The power semiconductor device comprises: a substrate (10), a first GaN layer (21), a second GaN layer (22), an AlGaN layer (23), an ohmic electrode (31) and a Schottky electrode (32); The first GaN layer (21), the second GaN layer (22), and the AlGaN layer (23) are sequentially stacked on the supporting surface of the substrate (10); the Schottky electrode (32) is located on a side of the AlGaN layer (23) away from the substrate (10); the surface of the AlGaN layer (23) has a groove (40) exposing the first GaN layer (21); the ohmic electrode (31) is located in the groove (40) and is connected to the first GaN layer (21); The surface of the second GaN layer (22) away from the substrate (10) has a plurality of spaced-apart protrusion structures (221), the protrusion structures (221) being embedded in the AlGaN layer (23), and the distribution density of the protrusion structures (221) gradually increases in a direction from the Schottky electrode (32) to the ohmic electrode (31) on the surface of the second GaN layer (22) away from the substrate (10).

2. The power semiconductor device according to claim 1, wherein: In the direction from the Schottky electrode (32) to the ohmic electrode (31), the ratio of the maximum distance between two adjacent protrusion structures (221) to the minimum distance between two adjacent protrusion structures (221) is 40:

3.

3. The power semiconductor device according to claim 1, wherein: The height of the protruding structure (221) is 20 nm to 80 nm, and the width is 200 nm to 500 nm. The height direction of the protruding structure (221) is perpendicular to the supporting surface of the substrate (10), and the width direction is parallel to the supporting surface of the substrate (10).

4. The power semiconductor device according to any one of claims 1 to 3, characterized in that: The power semiconductor device further comprises a third GaN layer (24), wherein the third GaN layer (24) is located on a surface of the AlGaN layer (23) away from the substrate (10); The first GaN layer (21), the second GaN layer (22) and the third GaN layer (24) are all doped with Si, and the doping concentration of the first GaN layer (21) and the doping concentration of the third GaN layer (24) are both higher than that of the second GaN layer (22).

5. The power semiconductor device according to claim 4, characterized in that: The doping concentration of the first GaN layer (21) is 10 17 cm -3 to 10 19 cm -3 , the doping concentration of the second GaN layer (22) is 10 15 cm -3 to 10 17 cm -3 The doping concentration of the third GaN layer (24) is 5×10 15 cm -3 to 5×10 17 cm -3 .

6. The power semiconductor device according to claim 4, characterized in that The thickness of the AlGaN layer (23) is not greater than the height of the protruding structure (221).

7. The power semiconductor device according to claim 6, characterized in that The thickness of the AlGaN layer (23) is 5 nm to 20 nm, and the thickness of the third GaN layer (24) is greater than 75 nm.

8. The power semiconductor device according to any one of claims 1 to 3, characterized in that: The thickness of the first GaN layer (21) is 1 μm to 5 μm, and the thickness of the second GaN layer (22) is 1 μm to 5 μm.

9. A method for preparing a power semiconductor device, characterized in that: The preparation method comprises: providing a substrate; forming a first GaN layer, a second GaN layer, and an AlGaN layer in sequence on the substrate, wherein a surface of the second GaN layer away from the substrate has a plurality of spaced-apart protrusion structures, and the protrusion structures are embedded in the AlGaN layer; Etching the AlGaN layer to form a groove exposing the first GaN layer; A Schottky electrode is fabricated on the AlGaN layer, and an ohmic electrode is fabricated in the groove. The ohmic electrode is connected to the first GaN layer. On a surface of the second GaN layer away from the substrate, the distribution density of the protruding structure gradually increases in a direction from the Schottky electrode to the ohmic electrode.

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