AlGaN / GaN heterojunction Schottky diode structure with partial n +-GaN cap layer

Abstract

The invention relates to an AlGaN / GaN heterojunction Schottky diode structure with a partial n < + >-GaN cap layer. The diode sequentially comprises a substrate, a buffer layer and a GaN channel layer from bottom to top, the AlGaN barrier layer is located at the upper middle part of the GaN channel layer, and the right side of the upper surface of the AlGaN barrier layer is the n +-GaN cap layer; the low-k dielectric protection layer covers the left side of the AlGaN barrier layer and the n +-GaN cap layer and is in a second-order step shape; a high-k dielectric layer covers the low-k dielectric protection layer; the Schottky contact metal covers the left side of the GaN channel layer and the left side of the upper surface of the high-k dielectric layer, and the ohmic contact metal covers the right side part of the GaN channel layer and the right side of the upper surface of the high-k dielectric layer. The diode structure obtained by the invention has excellent forward conduction characteristics and reverse characteristics.

Description

Technical Field

[0001] The present invention belongs to the technical field of power semiconductors and relates to a + -AlGaN / GaN heterojunction Schottky diode structure and preparation method with GaN cap layer. Background Art

[0002] In recent years, GaN materials have attracted widespread attention due to their excellent properties such as large bandgap, strong critical breakdown electric field, high thermal conductivity, and high saturation velocity. At the same time, GaN materials and their systems can form high-concentration, high-mobility two-dimensional electron gas (2DEG) due to extremely strong spontaneous and piezoelectric polarization effects. As a result, GaN materials have become the preferred semiconductor material for the development of high-frequency, high-power, and high-efficiency power devices.

[0003] In order to optimize the forward characteristics of the AlGaN / GaN heterojunction Schottky diode and increase the 2DEG concentration in the channel to reduce its forward on-resistance, a commonly used method is to adopt a multi-channel 2DEG structure. However, this design faces huge challenges in process preparation. The multi-channel 2DEG structure requires multiple depositions of thinner AlGaN layers, and it is necessary to ensure clear separation between the layers to avoid the upper and lower GaN layers being connected and to avoid losing the advantages of multiple channels. Therefore, this structure greatly increases the difficulty of process preparation and requires highly precise process control, which is not easy to achieve in actual production.

[0004] In order to improve the reverse breakdown voltage of AlGaN / GaN heterojunction Schottky diodes, one of the most commonly used and most applicable methods is the anode field plate technology. The field plate dielectric layer generally uses a material with a high-k dielectric constant to further reduce the electric field strength at the edge of the grooved Schottky anode through the charge coupling effect. However, limited by the current level of process technology, magnetron sputtering is generally used when growing thicker high-k materials. This method causes serious damage to the surface of GaN materials and is prone to introduce a large number of defects on the surface of GaN materials, thereby forming a defect-assisted leakage current channel, increasing the reverse leakage current of the device, and ultimately limiting the increase in reverse breakdown voltage. Therefore, it is urgent to explore new methods to reduce or overcome the impact of magnetron sputtering on the surface of GaN materials.

[0005] At the same time, in order to improve the reliability of AlGaN / GaN SBD, the authors of the paper "Mechanism of current-collapse free for lateral GaN Schottkybarrier diodes utilizing polarization-induced hole injection" proposed a lateral AlGaN / GaN SBD structure with an unintentionally doped GaN cap layer. However, due to the negative polarization charge between the GaN cap layer and the AlGaN barrier layer, the 2DEG between AlGaN / GaN is repelled, resulting in an increase in forward resistance and a weakening of the forward characteristics.

[0006] In summary, realizing AlGaN / GaN heterojunction Schottky diodes with excellent forward conduction and reverse cutoff characteristics is still a key technical challenge that needs to be solved urgently. Summary of the invention

[0007] In order to solve the shortcoming of the prior art that the forward conduction characteristic and the reverse cutoff characteristic cannot be improved at the same time, the present invention proposes a method having a partial n + -GaN capping layer AlGaN / GaN heterojunction Schottky diode structure and preparation method. The present invention designs the non-doped capping layer GaN into a partially etched high-doping concentration GaN capping layer, one of which is to provide electrons for the 2DEG at the AlGaN / GaN interface, thereby improving the forward conduction characteristics; the second is to use the etching of a part of the GaN capping layer to block the additional current channel formed by the GaN capping layer, thereby reducing the leakage current and improving the breakdown voltage. The diode structure obtained by the present invention has excellent forward conduction characteristics and reverse characteristics.

[0008] In order to solve the above technical problems, the technical solution of the present invention is as follows:

[0009] A type with part n + -GaN cap layer AlGaN / GaN heterojunction Schottky diode structure, the diode includes: a substrate, a buffer layer, a GaN channel layer, an AlGaN barrier layer, + -GaN cap layer, low-k dielectric protection layer, high-k dielectric layer, Schottky contact metal and ohmic contact metal;

[0010] The diode structure is composed of substrate, buffer layer and GaN channel layer from bottom to top. The AlGaN barrier layer is located in the middle of the upper surface of the GaN channel layer, and its projected area is 60-80% of the area of ​​the GaN channel layer.

[0011] The right side of the upper surface of the AlGaN barrier layer is n +-GaN cap layer; low-k dielectric protection layer covers the left side of the AlGaN barrier layer and the n + -GaN cap layer, in a two-step step shape; the low-k dielectric protection layer is covered with a high-k dielectric layer;

[0012] The + - The GaN cap layer is on the right side of the upper surface of the AlGaN barrier layer, and its projected area is 50-80% of the AlGaN barrier layer;

[0013] The Schottky contact metal covers the entire exposed portion on the left side of the GaN channel layer and the left side of the upper surface of the high-k dielectric layer, and 20 to 70% of the area on the high-k dielectric layer is covered with the Schottky contact metal;

[0014] The ohmic contact metal covers all exposed portions on the right side of the GaN channel layer and the right side of the upper surface of the high-k dielectric layer, and 5 to 10% of the area on the high-k dielectric layer is covered with the ohmic contact metal;

[0015] The substrate is made of sapphire, silicon or silicon carbide;

[0016] The buffer layer is AlGaN or AlN, with a thickness of 1.0 to 1.5 μm;

[0017] The GaN channel layer is unintentionally doped GaN and has a thickness of 3 to 10 μm;

[0018] The AlGaN barrier layer is unintentionally doped AlGaN and has a thickness of 20 to 30 nm;

[0019] The + -GaN capping layer is made of GaN with a doping concentration of 1x10 17 ~1x10 19 cm -3 , the doping element is silicon atom, and the thickness is 5 to 50 nm;

[0020] The material of the low-k dielectric protection layer is Si 3 N 4 or SiO 2 , its thickness is 10~20nm;

[0021] The material of the high-k dielectric layer is HfO 2 or 2 O 5 or SrTiO 3 or BaTiO 3 , its thickness is 0.1~2μm;

[0022] The Schottky contact metal is made of nickel and gold, and its thickness is 20-80nm and 150-300nm respectively;

[0023] The ohmic contact metal is made of titanium, aluminum and gold, and its thickness is 15-80nm, 20-100nm and 80-200nm respectively.

[0024] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0025] The diode obtained by the present invention adopts part n + The GaN capping layer can achieve two effects. First, it can increase the concentration of the two-dimensional electron gas (2DEG) at the AlGaN / GaN interface, thereby greatly improving the forward conduction capability of the diode and reducing the on-resistance. This is the first time that the GaN capping layer has been proposed. + -GaN capping layer structure is used to improve the forward conduction performance of the device. Compared with the structure without capping layer and the structure without intentional doping of GaN capping layer, when the forward voltage is 4V, the forward current density is increased from 1.14kA / cm 2 、0.79kA / cm 2 Increased to 1.6kA / cm 2 ; The second is by etching a part of n + -GaN capping layer can block the n + -GaN layer and Schottky metal, ohmic metal directly connected to the leakage current path, thereby effectively reducing the leakage current, compared with no etching n + -GaN structure, at a reverse bias voltage of 200V, the leakage current is from 0.012A / cm 2 Reduced to 2.5x10 -4 A / cm 2 At the same time, the distribution of the electric field is adjusted to increase the reverse breakdown voltage of the device. + -GaN structure, the reverse breakdown voltage is increased from 296V to 846V. On the other hand, by depositing a thin low-k dielectric protection layer before growing the high-k dielectric layer, the damage to the surface of the GaN material caused by the deposition process is reduced, thereby reducing the leakage current caused by defect-assisted tunneling, thereby suppressing the reverse overall leakage current of the device. The diode structure described in the present invention has excellent forward conduction characteristics and reverse characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the traditional AlGaN / GaN diode structure;

[0027] Figure 2 Schematic diagram of the traditional GaN / AlGaN / GaN diode structure;

[0028] Figure 3 The present invention embodiment 1 has part n +-Schematic diagram of the AlGaN / GaN structure of the GaN capping layer;

[0029] Figure 4 A comparison diagram of the forward characteristics of the present invention and the conventional device;

[0030] Figure 5 This is a comparison diagram of the reverse characteristics of the present invention and the traditional device.

[0031] The reference numerals are as follows:

[0032] 1—substrate; 2—buffer layer; 3—GaN channel layer; 4—AlGaN barrier layer; 5—n + -GaN capping layer; 6—low-k dielectric protection layer; 7—high-k dielectric layer; 8—Schottky contact metal; 9—Ohmic contact metal. DETAILED DESCRIPTION

[0033] The terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchanged in appropriate circumstances, which is only to describe the distinction mode adopted by the objects of the same attribute in the embodiments of the present application when describing. In the description of the present invention, the orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", "inside", "outside", etc. is based on the orientation or positional relationship shown in the drawings, only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, so that the process, method, system, product or equipment containing a series of units need not be limited to those units, but may include other units that are not clearly listed or inherent to these processes, methods, products or equipment.

[0034] The drawings are for illustrative purposes only and should not be construed as limiting the present patent;

[0035] In order to better illustrate the present embodiment, some parts in the drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product;

[0036] It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0037] In order to better understand and implement the present invention, the GaN / AlGaN diode and GaN / AlGaN / GaN diode structure in the prior art are described. Figure 1 :

[0038] The existing AlGaN / GaN diode device structure includes, in order along the epitaxial growth direction: bottom silicon substrate 1, AlGaN (or AlN) buffer layer 2, GaN channel layer 3, AlGaN barrier layer 4, high-k dielectric layer 7, Schottky contact metal 8, and ohmic contact metal 9. The 2DEG in the GaN / GaN SBD structure originates from the AlGaN surface state, and the concentration of donor-type interface states on the AlGaN surface is limited, so the improvement of forward characteristics is subject to certain restrictions.

[0039] See also Figure 2 :

[0040] The existing GaN / AlGaN / GaN diode device structure includes, in order along the epitaxial growth direction: a bottom silicon substrate 1, an AlGaN (or AlN) buffer layer 2, a GaN channel layer 3, an AlGaN barrier layer 4, a GaN cap layer 5, a high-k dielectric layer 7, a Schottky contact metal 8, and an ohmic contact metal 9. The GaN cap layer in the AlGaN / GaN SBD structure has two different functional situations. In the first situation, if the GaN cap layer has a certain doping concentration, i.e., n + -GaN capping layer can provide electrons to the AlGaN / GaN interface and increase the 2DEG concentration. + -The GaN capping layer is directly connected to the Schottky metal and the Ohmic metal to form a leakage current channel, which will increase the reverse leakage current and thus reduce the breakdown voltage. In another case, if the GaN capping layer is undoped, the negative polarization charge will exist between the GaN capping layer and the AlGaN interface, which will repel the 2DEG between the GaN channel layer and the AlGaN barrier layer, resulting in an increase in the forward conduction resistance and a weakening of the forward conduction performance. The GaN capping layers in the currently proposed GaN / AlGaN / GaN structure are all unintentionally doped low-concentration materials.

[0041] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0042] Example 1

[0043] This embodiment provides a method having a part n + -GaN cap layer AlGaN / GaN heterojunction Schottky diode structure, see Figure 3 The diode comprises: a silicon substrate 1, an AlGaN (or AlN) buffer layer 2, a GaN channel layer 3, an AlGaN barrier layer 4, and a + -GaN capping layer 5, low-k dielectric protection layer 6, high-k dielectric layer 7, Schottky contact metal 8 and ohmic contact metal 9;

[0044] The diode structure is as follows from bottom to top: silicon substrate 1, AlGaN (or AlN) buffer layer 2, GaN channel layer 3; AlGaN barrier layer 4 is located in the middle of the upper surface of GaN channel layer 3, and its projected area is 80% of the area of ​​GaN channel layer 3;

[0045] The right side of the upper surface of the AlGaN barrier layer 4 is n + -GaN cap layer 5; low-k dielectric protection layer 6 covers the left side of AlGaN barrier layer 4 and n + -GaN cap layer 5, in a two-step ladder shape; low-k dielectric protection layer 6 is covered with high-k dielectric layer 7;

[0046] The + The GaN cap layer 5 is on the right side of the upper surface of the AlGaN barrier layer 4 , and its projected area is 55% of the AlGaN barrier layer 4 .

[0047] The Schottky contact metal 8 covers the entire exposed portion on the left side of the GaN channel layer 3 and the left side of the upper surface of the high-k dielectric layer 7. 30% of the area of ​​the high-k dielectric layer 7 is covered with the Schottky contact metal 8, which is an "inverted L-type";

[0048] The ohmic contact metal 9 covers all exposed portions on the right side of the GaN channel layer 3 and the right side of the upper surface of the high-k dielectric layer 7, and 5% of the area of ​​the high-k dielectric layer 7 is covered with the ohmic contact metal 9;

[0049] In this embodiment, on the one hand, the diode adopts a part of n + -GaN capping layer 5 can achieve two effects. First, it can increase the concentration of two-dimensional electron gas (2DEG) at the AlGaN / GaN interface, thereby greatly improving the forward conduction capability of the diode and reducing the on-resistance. Second, by etching part of n + -GaN cap layer 5 can block the n + The GaN layer is directly connected to the Schottky metal 8 and the ohmic metal 9 to form a leakage current path, thereby effectively reducing the leakage current and, at the same time, adjusting the distribution of the electric field to increase the reverse breakdown voltage of the device. On the other hand, by depositing a thin low-k dielectric protection layer 6 before growing the high-k dielectric layer 7, the damage to the GaN surface caused by the magnetron sputtering process is effectively reduced, thereby reducing the leakage current caused by defect-assisted tunneling, and further reducing the reverse overall leakage current of the device.

[0050] It should be noted that the diode is a GaN-based diode with a heavily doped n-type GaN layer epitaxially grown on the AlGaN barrier layer 4. + -GaN layer 5, and etch away part of n +-GaN layer 5 can effectively increase the 2DEG concentration at the AlGaN / GaN interface and reduce the leakage current.

[0051] It should be emphasized that the n + - The GaN cap layer 5 is a heavily doped n-type semiconductor material with a certain thickness. The specific doping concentration, thickness and doping atoms are set by those skilled in the art according to actual conditions;

[0052] The substrate 1 is a 4-inch silicon substrate;

[0053] The buffer layer 2 is AlGaN with a thickness of 1.2 μm;

[0054] The GaN channel layer 3 is non-intentionally doped GaN and has a thickness of 5 μm;

[0055] The AlGaN barrier layer 4 is non-intentionally doped AlGaN and has a thickness of 25 nm;

[0056] The + -The doping concentration of the GaN cap layer 5 is 1x10 18 cm -3 , the doping element is silicon atom, and the thickness is 5nm;

[0057] The material of the low-k dielectric protection layer 6 is Si 3 N 4 , its thickness is 10nm;

[0058] The material of the high-k dielectric layer 7 is HfO 2 , its thickness is 0.2μm;

[0059] The Schottky contact metal 8 is made of nickel and gold, and its thickness is 50nm and 200nm respectively;

[0060] The ohmic contact metal 9 is made of titanium, aluminum, titanium and gold, and its thickness is 20nm, 30nm, 60nm and 100nm respectively.

[0061] The above has part n + The preparation method of the AlGaN / GaN heterojunction Schottky diode structure with a GaN cap layer is as follows:

[0062] Using metal organic chemical vapor deposition (MOCVD) technology, the silicon substrate 1 is heated to 1080℃ in a reactor. 2 Perform heat treatment in the atmosphere to remove impurities attached to the surface of the silicon substrate;

[0063] In a MOCVD reactor, an AlGaN buffer layer 2 is epitaxially grown on the surface of the silicon substrate 1 after impurities are removed by using a MOCVD two-step growth method;

[0064] In a MOCVD reactor, epitaxially growing a GaN channel layer 3 on the surface of the AlGaN buffer layer 2 by using a MOCVD two-step growth method;

[0065] In a MOCVD reactor, an AlGaN barrier layer 4 is epitaxially grown on the surface of the GaN channel layer 3 by using a MOCVD two-step growth method;

[0066] In the MOCVD reactor, an MOCVD two-step growth method is used to epitaxially grow nGaN on the surface of the AlGaN barrier layer 4. + -GaN capping 5 layers;

[0067] will grow to n + -The epitaxial wafer of the GaN / AlGaN / GaN structure layer is cleaned in an organic solvent for 20 minutes, then rinsed with flowing deionized water for 2 minutes, and blown dry with high-purity nitrogen for about 2 minutes;

[0068] The upper surface of the dried epitaxial wafer is coated with photoresist at a rotation speed of 3000 rpm for 30 seconds, and then exposed for 5 seconds, developed for 180 seconds, and ICP etched AlGaN / GaN 120nm at an etching rate of about 4nm / min to form grooves for growing Schottky metal and ohmic metal.

[0069] Use AZ400T degumming liquid to remove the remaining photoresist from the etched epitaxial wafer, clean the etched epitaxial wafer, and then blow dry it with nitrogen for about 2 minutes;

[0070] The upper surface of the etched and cleaned epitaxial wafer is coated with photoresist, and part of the n is removed through exposure, development and ICP etching. + -GaN capping layer;

[0071] Immerse the epitaxial wafer after ICP multi-step etching in a 20% mass fraction sodium hydroxide (NaOH) aqueous solution for at least 40 minutes to repair defects and damage on the GaN surface caused by dry etching;

[0072] The upper surface of the repaired epitaxial wafer is coated with photoresist, and after exposure and development, a growth Si 3 N 4 A window of the dielectric protection layer 6;

[0073] The developed epitaxial wafer is placed in a PECVD (plasma enhanced chemical vapor deposition) furnace and a 10 nm thick Si is grown at a low temperature of 70 °C using PECVD. 3 N4 Dielectric protection layer 6;

[0074] Will grow Si 3 N 4 The epitaxial wafer of dielectric protection layer 6 is placed in a magnetron sputtering chamber, and 200 nm of HfO is grown at a growth rate of 0.15 nm / s at room temperature. 2 The field plate dielectric layer 7 is stripped and the photoresist is removed by immersing it in AZ400T stripping solution;

[0075] Will grow HfO 2 The epitaxial wafer of the field plate dielectric layer 7 is subjected to photolithography, and after exposure and development, a window of the ohmic electrode metal 9 is formed, and then it is placed in an electron beam evaporation station to evaporate the ohmic contact metal Ti / Al / Ti / Au at a growth rate of 0.02nm / s, and then peeled off;

[0076] The peeled epitaxial wafer is subjected to rapid thermal annealing at 650°C for 35s in a nitrogen environment to form a Ti / Al / Ti / Au ohmic contact metal 9;

[0077] The epitaxial wafer with the ohmic contact metal 9 is photolithographically processed, and windows of the Schottky electrode and the field plate metal 8 are formed after exposure and development. Then, it is placed in an electron beam evaporation station to evaporate the Schottky contact metal Ni / Au at a growth rate of 0.02nm / s, and then peeled off to finally form an AlGaN / GaN heterojunction Schottky diode structure.

[0078] The device effect obtained by this embodiment is as follows Figure 4 and Figure 5 The test equipment is Keithley 2657A and 2636B series power device analysis systems. Figure 4 It is obvious that in the case of 4V forward, there is a part of n + The current density of the GaN capping layer, unintentionally doped GaN capping layer and no capping layer structure devices is 1.6kA / cm 2 、0.79kA / cm 2 and 1.14 kA / cm 2 .contrast Figure 5 With / without etching + -GaN cap layer, you can see the etched part n + -GaN capping layer can reduce leakage current. When the reverse bias voltage is 200V, the leakage current is reduced from 0.012A / cm 2 Reduced to 2.5x10 -4 A / cm 2 , and at the same time the breakdown voltage can be increased from 296V to 846V.

[0079] Example 2

[0080] The other steps are the same as those in Example 1, except that n + -The doping concentration of the GaN cap layer 5 is 1x10 18 cm -3 , with a thickness of 5nm, and the doping element is replaced by silicon atoms with a doping concentration of 5x10 17 cm -3 , thickness is 20nm.

[0081] The performance of the device obtained is close to that of Example 1.

[0082] Example 3

[0083] The other steps are the same as those in Example 1, except that n + The GaN cap layer 5 is on the right side of the upper surface of the AlGaN barrier layer 4 , and its projected area is 55% of the AlGaN barrier layer 4 instead of 70%.

[0084] The performance of the device obtained is close to that of Example 1.

[0085] Example 4

[0086] The other steps are the same as those in Example 1, except that the material of the low-k dielectric protection layer 7 is Si 3 N 4 , whose thickness is 10nm and is replaced by SiO 2 Material, the thickness of which is 15nm.

[0087] The performance of the device obtained is close to that of Example 1.

[0088] Example 5

[0089] The other steps are the same as those in Example 1, except that the material of the high-k dielectric layer 8 is HfO 2 , whose thickness is 0.2μm is replaced by Ta 2 O 5 The material has a thickness of 0.5 μm.

[0090] The performance of the device obtained is close to that of Example 1.

[0091] Example 6

[0092] The other steps are the same as those in Example 1, except that the upper left surface of the high-k dielectric layer 7 is covered with a Schottky contact metal 8, and its projected area is replaced by 40% of the area of ​​the high-k dielectric layer 7 instead of 30%.

[0093] The performance of the device obtained is close to that of Example 1.

[0094] Compared with the prior art, the method described in this embodiment has strong operability, low cost, simple and reliable process, and is suitable for industrial promotion and use.

[0095] Those skilled in the art should understand that the material used for the Schottky metal electrode is a loading structure, such as Ti / Al, which means that Al is loaded on Ti.

[0096] The same or similar reference numerals correspond to the same or similar components;

[0097] The terms used in the drawings to describe positional relationships are only used for illustrative purposes and should not be construed as limiting this patent;

[0098] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation methods of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. Each functional module or unit can be integrated together to form an independent part, or each module can exist separately, or two or more modules can be integrated to form an independent part. It is not necessary and impossible to list all implementation methods here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the claims of the present invention.

[0099] Matters not covered by the present invention are known technologies.

Claims

1. A type with part n + -GaN cap layer AlGaN / GaN heterojunction Schottky diode structure, characterized by: The diode comprises: a substrate, a buffer layer, a GaN channel layer, an AlGaN barrier layer, + -GaN cap layer, low-k dielectric protection layer, high-k dielectric layer, Schottky contact metal and ohmic contact metal; The diode structure is as follows from bottom to top: substrate, buffer layer, GaN channel layer; the AlGaN barrier layer is located in the middle of the upper surface of the GaN channel layer; The right side of the upper surface of the AlGaN barrier layer is n + -GaN cap layer; low-k dielectric protection layer covers the left side of the AlGaN barrier layer and the n + -GaN cap layer, in a two-step step shape; the low-k dielectric protection layer is covered with a high-k dielectric layer; The Schottky contact metal covers the entire exposed portion on the left side of the GaN channel layer and the left side of the upper surface of the high-k dielectric layer; the ohmic contact metal covers the entire exposed portion on the right side of the GaN channel layer and the right side of the upper surface of the high-k dielectric layer.

2. The method according to claim 1 having a portion n + -GaN cap layer AlGaN / GaN heterojunction Schottky diode structure, characterized by: The projected area of ​​the AlGaN barrier layer is 60-80% of the area of ​​the GaN channel layer.

3. The method according to claim 1 having a portion n + -GaN cap layer AlGaN / GaN heterojunction Schottky diode structure, characterized by: The + The -GaN cap layer is on the right side of the upper surface of the AlGaN barrier layer, and its projected area is 50-80% of that of the AlGaN barrier layer.

4. The method according to claim 1 having a portion n + -GaN cap layer AlGaN / GaN heterojunction Schottky diode structure, characterized by: 20-70% of the area of ​​the high-k dielectric layer is covered with Schottky contact metal; 5 to 10% of the area of ​​the high-k dielectric layer is covered with ohmic contact metal.

5. The method according to claim 1 having a portion n + -GaN cap layer AlGaN / GaN heterojunction Schottky diode structure, characterized by: The substrate is made of sapphire, silicon or silicon carbide; The buffer layer is AlGaN or AlN, with a thickness of 1.0 to 1.5 μm; The GaN channel layer is unintentionally doped GaN and has a thickness of 3 to 10 μm; The AlGaN barrier layer is unintentionally doped AlGaN and has a thickness of 20 to 30 nm; The + -GaN capping layer is made of GaN with a doping concentration of 1x10 17 ~1x10 19 cm -3 , the doping element is silicon atom, and the thickness is 5 to 50 nm; The material of the low-k dielectric protection layer is Si3N4 or SiO2, and its thickness is 10-20nm; The material of the high-k dielectric layer is HfO2, Ta2O5, SrTiO3 or BaTiO3, and its thickness is 0.1-2 μm.

6. The method according to claim 1 having a portion n + -GaN cap layer AlGaN / GaN heterojunction Schottky diode structure, characterized by: The Schottky contact metal is made of nickel and gold, and its thickness is 20-80nm and 150-300nm respectively; The ohmic contact metal is made of titanium, aluminum and gold, and its thickness is 15-80nm, 20-100nm and 80-200nm respectively.

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