CN105280725B - A kind of gallium nitride diode and its manufacturing method - Google Patents

Abstract

The invention discloses a kind of gallium nitride diode and preparation method thereof, which includes: substrate；The first channel layer on the substrate；The first two-dimensional electron gas is formed at the interface of the first barrier layer on first channel layer, first barrier layer and first channel layer；Cap layer structure on first barrier layer；On first barrier layer of cap layer structure side and/or cathode within first barrier layer is extended to, is provided with gap between the cap layer structure and the cathode；On first barrier layer of the cap layer structure other side and/or anode within first barrier layer is extended to, and the anode is covered to the upper surface of the cap layer structure.Gallium nitride diode of the present invention have low turn-on voltage, low on-resistance, high forward conduction electric current, high reverse withstand voltage and low reverse leakage characteristic.

Description

A kind of gallium nitride diode and its manufacturing method

technical field

The present invention relates to the technical field of semiconductors, and in particular, to a gallium nitride diode and a manufacturing method thereof.

Background technique

As the basic building block of electronic power, diodes are an indispensable part of voltage regulators, rectifiers and inverters. With the development of modern power electronics, diodes have put forward higher requirements on the performance of high breakdown voltage, low power consumption and low leakage.

The semiconductor material gallium nitride (GaN) has the characteristics of large band gap, high thermal conductivity, and strong breakdown field, which makes gallium nitride devices have the advantages of low on-resistance and high operating frequency, which can meet the requirements of modern power electronics development for diodes. requirements.

At present, diodes based on GaN materials have achieved great development. Most of the existing GaN Schottky diodes achieve rectification characteristics through a Schottky barrier formed by metal materials and semiconductor materials in the diodes. At this time, electrons need to cross the Schottky barrier to achieve conduction, so the forward turn-on voltage is relatively large, generally greater than 1.5V. To reduce the forward turn-on voltage, the Schottky barrier needs to be reduced, but after the Schottky barrier is reduced, when the diode is applied with reverse bias, the leakage current will increase, and there is a mirror force effect As a result, the Schottky barrier height is reduced and the leakage current is increased. Around increasing breakdown voltage, reducing reverse leakage current, increasing forward current, and reducing turn-on voltage, GaN Schottky diodes still need continuous improvement and innovation.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a gallium nitride diode and a manufacturing method thereof to achieve low turn-on voltage and low reverse leakage.

For this purpose, the present invention adopts the following technical solutions:

In a first aspect, the present invention discloses a gallium nitride diode, comprising:

substrate;

a first channel layer on the substrate;

a first potential barrier layer located on the first channel layer, a first two-dimensional electron gas is formed at the interface between the first potential barrier layer and the first channel layer;

a cap layer structure on the first barrier layer;

a cathode located on the first barrier layer on one side of the cap layer structure and/or extending into the first barrier layer, a gap is provided between the cap layer structure and the cathode;

An anode located on and/or extending into the first barrier layer on the other side of the cap layer structure and covering the upper surface of the cap layer structure.

Further, it also includes:

a second channel layer under the capping structure and on the first barrier layer between the capping structure and the cathode;

a second barrier layer on the second channel layer between the cap layer structure and the second channel layer and between the cap layer structure and the cathode, the second barrier layer being connected to A second two-dimensional electron gas is formed at the interface of the second channel layer.

Further, the material of the cap layer structure is indium gallium nitride, aluminum indium gallium nitride or p-type indium gallium nitride.

Further, the P-type indium gallium nitride is doped with magnesium.

Further, the thickness of the cap layer structure is 2 nanometers to 20 nanometers.

Further, the surface regions of the first barrier layer in contact with the cathode and the anode are respectively doped with impurities.

Further, the preparation process of the cathode and the anode are completely the same.

Further, the anode includes a first anode and a second anode;

the first anode is located on the first barrier layer on the other side of the capping structure, and the first anode is in contact with the capping structure;

the second anode is located on the first anode and the capping structure; wherein,

The first anode forms an ohmic contact with the first barrier layer, and the second anode forms a Schottky contact with the cap layer structure.

In a second aspect, the present invention discloses a method for manufacturing a gallium nitride diode, comprising:

provide a substrate;

forming a first channel layer on the substrate;

forming a first potential barrier layer on the first channel layer, and a first two-dimensional electron gas is formed at the interface between the first potential barrier layer and the first channel layer;

forming a capping layer structure on the first barrier layer, and

forming a cathode on and/or extending into the first barrier layer on one side of the cap layer structure, a gap is provided between the cap layer structure and the cathode, and

An anode is formed on and/or extending into the first barrier layer on the other side of the capping structure, and the anode covers the upper surface of the capping structure.

Further, after a first barrier layer is formed on the first channel layer, and a first two-dimensional electron gas is formed at the interface between the first barrier layer and the first channel layer, the Methods also include:

forming a second channel layer on the first barrier layer;

A second barrier layer is formed on the second channel layer, and a second two-dimensional electron gas is formed at the interface between the second barrier layer and the second channel layer,

The forming a cap layer structure is formed on the second barrier layer.

In the gallium nitride diode and its manufacturing method provided by the embodiments of the present invention, a cap layer structure is introduced, and a part of the anode covers the upper surface of the cap layer structure, so that the anode above the cap layer structure controls the first channel below the cap layer structure The turn-on and turn-off of the first two-dimensional electron gas at the interface between the layer and the first barrier layer realizes the rectification characteristics of the gallium nitride diode, so that the gallium nitride diode has low turn-on voltage, low on-resistance, Features high forward current, high reverse withstand voltage and low reverse leakage.

Description of drawings

In order to illustrate the technical solutions of the exemplary embodiments of the present invention more clearly, the following briefly introduces the accompanying drawings used in describing the embodiments. Obviously, the introduced drawings are only a part of the drawings of the embodiments to be described in the present invention, rather than all drawings. For those of ordinary skill in the art, without creative work, they can also obtain the drawings according to these drawings. Additional drawings.

FIG. 1 is a cross-sectional view of the gallium nitride diode according to the first embodiment of the present invention when the conduction channel is turned off.

FIG. 2A is an energy band diagram of the gallium nitride diode provided in the first embodiment of the present invention when there is no external bias voltage and no cap layer structure.

FIG. 2B is an energy band diagram of the gallium nitride diode provided in the first embodiment of the present invention when no external bias is applied, and the material of the cap layer structure is indium gallium nitride.

FIG. 2C is an energy band diagram of the gallium nitride diode provided in the first embodiment of the present invention when there is no external bias voltage, and the material of the cap layer structure is P-type indium gallium nitride.

FIG. 3 is a cross-sectional view of the gallium nitride diode according to the first embodiment of the present invention when the conductive channel is recovered.

FIG. 4 is a flowchart of a method for fabricating a gallium nitride diode according to Embodiment 1 of the present invention.

5A shows the first barrier layer formed on the first channel layer from the step of providing the substrate to the step of the method for fabricating a gallium nitride diode according to the first embodiment of the present invention, and the intersection of the first barrier layer and the first channel layer A cross-sectional view corresponding to the first two-dimensional electron gas is formed at the interface.

5B is a cross-sectional view corresponding to the steps of forming a cap layer on the first barrier layer in the method for fabricating a gallium nitride diode according to Embodiment 1 of the present invention.

5C is a cross-sectional view corresponding to the step of etching the cap layer in the method for manufacturing a gallium nitride diode according to Embodiment 1 of the present invention, and exposing the first barrier layers on both sides of the etched cap layer.

5D is a cross-sectional view of simultaneously forming a cathode and a first anode on the first barrier layer exposed on both sides of the etched cap layer in the method for fabricating a gallium nitride diode according to Embodiment 1 of the present invention.

5E shows the steps of forming a second anode on the first anode and the etched cap layer in the method for fabricating a gallium nitride diode provided in the first embodiment of the present invention, and the second anode covers a portion of the upper surface of the etched cap layer corresponding to Sectional drawing.

FIG. 6 is a cross-sectional view of the gallium nitride diode according to the second embodiment of the present invention when the conduction channel is turned off.

FIG. 7 is a flowchart of a method for fabricating a gallium nitride diode according to Embodiment 2 of the present invention.

8A is a cross-sectional view corresponding to the step of doping the surface area of the first barrier layer exposed on both sides of the etched cap layer in the method for fabricating a gallium nitride diode according to Embodiment 2 of the present invention.

FIG. 9 is a cross-sectional view of the gallium nitride diode according to the third embodiment of the present invention when the conduction channel is turned off.

FIG. 10 is a flowchart of a method for fabricating a gallium nitride diode according to Embodiment 3 of the present invention.

11A shows the steps of forming the second channel layer on the first barrier layer to the step of etching part of the cap layer and the second barrier layer and the second barrier layer under the gallium nitride diode according to the third embodiment of the present invention. Two channel layers.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be completely described below with reference to the accompanying drawings in the embodiments of the present invention and through specific implementation manners. Obviously, the described embodiments are a part of the embodiments of the present invention, rather than all the embodiments, based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work, All fall within the protection scope of the present invention.

First, the working principle of the gallium nitride diode provided by the embodiment of the present invention is described: 1) When there is no applied voltage (V _AC =0), the cap layer structure (the material can be InGaN, indium gallium nitride) and the first barrier layer ( The material can be AlGaN, aluminum gallium nitrogen) interface to generate negative polarization charges, so that the energy band is moved up, depleting the first barrier layer (the material can be AlGaN) and the first channel layer (the material can be GaN) The first two-dimensional electron gas (two-dimensional electron gas, 2DEG for short) at the interface turns off the gallium nitride diode. 2) When a positive voltage is applied to the anode (V _AC > Vk), the conduction band at the interface between the first barrier layer and the first channel layer under the cap layer structure moves down, and when it is lower than the Fermi level, the first barrier layer moves downward. The one-dimensional electron gas channel recovers and the GaN diode turns on. 3) When a negative voltage is applied to the anode (V _AC <0), the bottom of the conduction band at the interface between the first barrier layer and the first channel layer further rises, the 2DEG is further depleted, and the gallium nitride diode is turned off. The turn-on voltage of the GaN diode is determined by the depletion of the 2DEG by the cap layer structure and has nothing to do with the height of the Schottky barrier. In addition, using the undoped InGaN cap layer structure, the energy band upward shift at the interface between the first barrier layer and the first channel layer under the cap layer structure is small, the turn-on voltage of the GaN diode is small when it is turned on, and the current Low power consumption through the same current. The leakage current of the gallium nitride diode consists of two parts: 1) the leakage current between the anode and the cathode on one side of the cap layer structure; 2) the leakage current between the anode and the cathode above the cap layer structure. As the reverse voltage increases, the width of the 2DEG depletion layer under the cap layer expands and the leakage decreases, which is much smaller than the Schottky tunneling current. The leakage between the anode and the cathode above the cap layer structure is the leakage of the heterojunction diode. The height and width of the barrier of the heterojunction diode are larger than that of the Schottky diode, and the height of the barrier is not affected by the mirror force. In principle, the leakage current of this structure is determined by the recombination current generated in the depletion region, which is much smaller than the tunneling current of ordinary diodes.

Example 1:

FIG. 1 is a cross-sectional view of the gallium nitride diode according to the first embodiment of the present invention when the conduction channel is turned off. As shown in FIG. 1 , the gallium nitride diode includes: a substrate 11 , a first channel layer 131 located on the substrate 11 , a first barrier layer 141 located on the first channel layer 131 , a first potential barrier A first two-dimensional electron gas 151 is formed at the interface between the layer 141 and the first channel layer 131 , the cap layer structure 16 located on the first barrier layer 141 , and the first barrier layer 141 located on the side of the cap layer structure 16 . On and/or extending to the cathode 17 within the first barrier layer 141 , a gap is provided between the cap layer structure 16 and the cathode 17 , located on and/or extending from the first barrier layer 141 on the other side of the cap layer structure 16 to the anode within the first barrier layer 141 , and the anode covers the upper surface of the cap layer structure 16 . Preferably, the anode may include a first anode 181 and a second anode 182; the first anode 181 is located on the first barrier layer 141 on the other side of the cap layer structure 16, and the first anode 181 is in contact with the cap layer structure 16; Two anodes 182 are located on the first anode 181 and the cap layer structure 16 .

In this embodiment, the material of the substrate 11 may be silicon carbide, silicon or sapphire. The material of the first channel layer 131 may be undoped gallium nitride. Preferably, the gallium nitride diode may further include a buffer layer 12 between the substrate 11 and the first channel layer 131 . The buffer layer 12 can match the material of the substrate 11 and improve the quality of the first channel layer 131 . effect. The material of the buffer layer 12 may be undoped gallium nitride, aluminum nitride or other group III nitrides.

The first barrier layer 141 and the first channel layer 131 form a heterojunction structure, and a first two-dimensional electron gas 151 is formed at the interface between the first barrier layer 141 and the first channel layer 131 . The material of the first barrier layer 141 may be aluminum gallium nitride or other group V nitrides.

The material of the cap layer structure 16 can be indium gallium nitride, indium aluminum gallium nitride or p-type indium gallium nitride, wherein the doping material of p-type indium gallium nitride can be magnesium. The smaller the doping concentration of P-type IGaN, the weaker the depletion of 2EDG, that is, the closer the distance between the conduction band (E _c ) and the Fermi level (E _f ) at the channel formed by 2EDG, the more The lower the turn-on voltage of the gallium diode. In order to achieve a relatively low turn-on voltage, the material of the cap layer structure 16 is preferably indium gallium nitride.

When the thickness of the cap layer structure 16 is greater than 2 nm, the bottommost position of the conduction band (ie, the bottom of the conduction band) at the interface between the first channel layer 131 and the first barrier layer 141 of the gallium nitride diode can be moved up to Above the m energy level, the first two-dimensional electron gas 151 at the interface between the first channel layer 131 and the first barrier layer 141 under the cap layer structure 16 is completely depleted, and at the same time, in order to ensure that the gallium nitride diode has a relatively high energy density. For a small turn-on voltage (less than 1V), the thickness of the cap layer structure 16 should be controlled within 20 nanometers. Therefore, the thickness of the cap layer structure 16 may be 2 nanometers to 20 nanometers. The turn-on voltage can be made close to +0V by adjusting the thickness of the cap layer structure 16 , and the length of the cap layer structure 16 can be determined according to the specific design requirements of the gallium nitride diode.

The first anode 181 and the second anode 182 may be formed simultaneously to constitute an anode together. The cathode 17 and the first anode 181 form ohmic contact with the first barrier layer 141 and the first channel layer 131 . The second anode 182 covers the upper surface of the capping structure 16 and forms a Schottky contact with the capping structure 16 .

As shown in Figure 1, when the gallium nitride diode is not biased, the polarized charges generated at the interface between the cap layer structure and the first barrier layer make the first channel layer under the cap layer structure and the first barrier layer The bottom of the conduction band at the interface of the barrier layer moves up, depleting the first two-dimensional electron gas at the interface between the first channel layer and the first barrier layer under the cap layer structure, and the conductive channel of the gallium nitride diode closure.

FIG. 2A is an energy band diagram of the gallium nitride diode provided in the first embodiment of the present invention when there is no external bias voltage and no cap layer structure. FIG. 2B is an energy band diagram of the gallium nitride diode provided in the first embodiment of the present invention when no external bias is applied, and the material of the cap layer structure is indium gallium nitride. FIG. 2C is an energy band diagram of the gallium nitride diode provided in the first embodiment of the present invention when there is no external bias voltage, and the material of the cap layer structure is P-type indium gallium nitride. where E _C and E _F represent the conduction band and Fermi level, respectively. It can be seen from FIGS. 2A , 2B and 2C that when the material of the cap layer structure is undoped indium gallium nitride, the bottom of the conduction band moves upward, and when the material of the cap layer structure is indium gallium nitride, the magnitude of the upward shift of the bottom of the conduction band When the material of the cap layer structure is P-type indium gallium nitride, the upward shift of the conduction band bottom is smaller, that is, it is close to the Fermi level. Because the smaller the upward shift of the conduction band bottom is, the lower the turn-on voltage is. Therefore, when the material of the cap layer structure is indium gallium nitride, the turn-on voltage and the on-state power consumption of the gallium nitride diode are smaller when it is turned on. . Therefore, the material of the cap layer structure in the first embodiment is preferably indium gallium nitride.

FIG. 3 is a cross-sectional view of the gallium nitride diode according to the first embodiment of the present invention when the conductive channel is recovered. As shown in Fig. 3, when the gallium nitride diode is forward biased, the bottom of the conduction band at the interface between the first channel layer and the first barrier layer under the cap layer structure moves down, and when it is lower than the Fermi level At the time, the first two-dimensional electron gas at the interface between the first channel layer and the first barrier layer under the cap layer structure recovers, and the conductive channel of the gallium nitride diode recovers.

When a reverse bias is applied to the gallium nitride diode, the bottom of the conduction band at the interface between the first channel layer and the first barrier layer under the cap layer structure moves upward, and the first channel layer under the cap layer structure and the first barrier layer move upward. The first two-dimensional electron gas at the interface of the first barrier layer is depleted. The leakage current of the gallium nitride diode consists of two parts: 1) the leakage current between the anode and the cathode on one side of the cap layer structure; 2) the leakage current between the anode and the cathode above the cap layer structure. As the reverse voltage increases, the width of the 2DEG depletion layer under the cap layer expands and the leakage decreases, which is much smaller than the Schottky tunneling current. The leakage between the anode and the cathode above the cap layer structure is the leakage of the heterojunction diode. The height and width of the barrier of the heterojunction diode are larger than that of the Schottky diode, and the barrier height is not affected by the mirror force. In principle, the leakage current of this structure is determined by the recombination current generated in the depletion region, which is much smaller than the tunneling current of ordinary diodes.

The gallium nitride diode provided in the first embodiment of the present invention controls the on and off of the first two-dimensional electron gas at the interface between the first channel layer and the first barrier layer below the cap layer structure through the anode above the cap layer structure , to achieve the rectification characteristics of the gallium nitride diode, by increasing the height of the heterojunction barrier and the width of the depletion layer in the reverse direction, and without the effect of reducing the reverse barrier. Therefore, the gallium nitride diode has the characteristics of low turn-on voltage, low on-resistance, high forward current, high reverse withstand voltage and low reverse leakage at the same time, and has a simple structure.

FIG. 4 is a flowchart of a method for fabricating a gallium nitride diode according to Embodiment 1 of the present invention. As shown in Figure 4, the method includes:

Step 41, providing a substrate.

The material of the substrate can be silicon carbide, silicon or sapphire.

Step 42, forming a first channel layer on the substrate.

The material of the first channel layer may be undoped gallium nitride. The first channel layer is formed on the substrate using a metal organic compound chemical vapor deposition process or a molecular beam epitaxy process.

Preferably, between step 41 and step 42, the method may further include: forming a buffer layer on the substrate. The buffer layer can play the role of matching the substrate material and improving the quality of the first channel layer. Wherein, the material of the buffer layer may be undoped gallium nitride, aluminum nitride or other group III nitrides.

Step 43 , forming a first potential barrier layer on the first channel layer, and a first two-dimensional electron gas is formed at the interface between the first potential barrier layer and the first channel layer.

A first barrier layer is formed on the first channel layer by using a metal organic compound chemical vapor deposition process or a molecular beam epitaxy process.

As shown in FIG. 5A , FIG. 5A shows cross-sectional views corresponding to steps 41 to 43 .

Step 44 , forming a cap layer on the first barrier layer.

As shown in FIG. 5B , a cap layer 161 is formed on the first barrier layer 141 . At this time, the first two-dimensional electron gas at the interface between the first channel layer 131 and the first barrier layer 141 under the cap layer 161 is run out.

Step 45 , etching the cap layer, and exposing the first barrier layers on both sides of the etched cap layer.

As shown in FIG. 5C , the cap layer is etched using a photolithography process and a dry etching process, and the first barrier layers 141 on both sides of the etched cap layer 162 are exposed. The first two-dimensional electron gas at the interface between the first channel layer 131 and the first barrier layer 141 under the layer 162 is depleted, and only at the interface between the exposed first barrier layer region and the first channel layer A first two-dimensional electron gas 151 exists.

Since the material of the cap layer is different from the material of the first barrier layer, in the process of etching the cap layer, the etching of the cap layer can precisely stay on the first barrier layer.

When the material of the cap layer is indium gallium nitride, aluminum indium gallium nitride or p-type indium gallium nitride, a photolithography process and a selective etching process are used, using boron trichloride/sulfur hexafluoride (BCl ₃ /SF ₆ ) The plasma is used as an etching gas to etch the cap layer. When the cap layer is etched, the boron trichloride/sulfur hexafluoride plasma will form aluminum trifluoride when it contacts the first barrier layer below, while The volatility of aluminum trifluoride is very low, and it will adhere to the first barrier layer to protect the first barrier layer from being etched, so when the cap layer is etched, it will automatically stay at the first barrier layer. layer.

Step 46 , simultaneously forming a cathode and a first anode on the exposed first barrier layer on both sides of the etched cap layer and/or extending into the first barrier layer.

As shown in FIG. 5D , using a metal electron beam evaporation process or a metal sputtering process, the exposed first barrier layer 141 on both sides of the etched cap layer 162 and/or extends to the first barrier layer 141 The cathode 17 and the first anode 181 are simultaneously formed therein.

Step 47 , forming a second anode on the first anode and the etched cap layer, and the second anode covers part of the upper surface of the etched cap layer.

As shown in FIG. 5E, a metal electron beam evaporation process or a metal sputtering process is used to form a second anode 182 on the first anode 181 and the partially etched cap layer 162, and the second anode 182 covers the partially etched cap layer 162. The upper surface of the cap layer 162 .

The area of the cap layer structure portion of the anode formed in this step may be determined according to the specific design requirements of the gallium nitride diode.

Step 48 , etching the remaining part of the etched cap layer that is not covered by the second anode to form a cap layer structure.

In the gallium nitride diode provided by the first embodiment of the present invention, a cap layer structure is introduced, and a part of the anode covers the upper surface of the cap layer structure, so that the anode above the cap layer structure controls the first channel layer under the cap layer structure and the first channel layer under the cap layer structure. The turn-on and turn-off of the first two-dimensional electron gas at the interface of a potential barrier layer realizes the rectification characteristics of the gallium nitride diode, so that the gallium nitride diode has low turn-on voltage, low on-resistance, and high forward conductance at the same time. It has the characteristics of passing current, high reverse withstand voltage and low reverse leakage current, and has a simple structure.

Embodiment 2:

FIG. 6 is a cross-sectional view of the gallium nitride diode according to the second embodiment of the present invention when the conduction channel is turned off. As shown in FIG. 6 , different from the gallium nitride diode provided by the first embodiment of the present invention, the first barrier layer 141 in contact with the cathode 17 and the first anode 181 in the gallium nitride diode provided by the second embodiment of the present invention The surface regions of the doped regions are respectively doped with impurities to form doped regions 19 .

In this embodiment, the impurities may be silicon ions.

The first barrier layer doped with impurities forms an n-type heavily doped region. After that, when a metal electrode is evaporated in this heavily doped region, due to the high doping concentration of the first barrier layer, the metal electrode and the first barrier are separated from each other. The barrier width of the layer is lower and the electron tunneling probability is higher, so the resistance between the first barrier layer and the metal electrode is lower, and a better ohmic contact can be formed, and the metal electrode is the cathode and the anode.

FIG. 7 is a flowchart of a method for fabricating a gallium nitride diode according to Embodiment 2 of the present invention. As shown in FIG. 7 , in this embodiment, Steps 71 to 75 are respectively the same as Steps 41 to 45 in Embodiment 1. , steps 77 to 79 are respectively the same as steps 46 to 48 in the first embodiment. This embodiment only describes the difference from the first embodiment.

Step 76: Doping the exposed surface regions of the first barrier layer on both sides of the etched cap layer.

As shown in FIG. 8A , by using an ion implantation process, the surface regions of the first barrier layer 141 on both sides of the etched cap layer 162 are doped to form a doped region 19 .

Compared with the gallium nitride diode provided by the first embodiment of the present invention, the gallium nitride diode provided by the second embodiment of the present invention is doped with impurities through the surface regions of the first barrier layer in contact with the cathode and the anode, so that the The cathode and the anode of the gallium nitride diode can form better ohmic contact with the first barrier layer and the first channel layer, respectively.

Embodiment three:

FIG. 9 is a cross-sectional view of the gallium nitride diode according to the third embodiment of the present invention when the conduction channel is turned off. As shown in FIG. 9 , different from the gallium nitride diode provided in the first embodiment of the present invention, the gallium nitride diode further includes: a first layer located under the cap layer structure 16 and between the cap layer structure 16 and the cathode 17 . The second channel layer 132 on the barrier layer 141 , the second potential barrier on the second channel layer 132 between the cap layer structure 16 and the second channel layer 132 and between the cap layer structure 16 and the cathode 17 Layer 142, a second two-dimensional electron gas 152 is formed at the interface between the second barrier layer 142 and the second channel layer 132.

The second barrier layer 142 and the second channel layer 132 form a heterojunction structure, and a second two-dimensional electron gas 152 is formed at the interface between the second barrier layer 142 and the second channel layer 132 . The material of the second barrier layer 142 may be aluminum gallium nitride or other group V nitrides.

The material of the cap layer structure 16 may be indium gallium nitride, aluminum indium gallium nitride or p-type indium gallium nitride, preferably P-type indium gallium nitride. When p-type indium gallium nitride is used, the cap layer structure is thinner, and the anode has better control ability of the conductive channel.

The gallium nitride diode provided in this embodiment adopts a multi-layer heterojunction structure to form a multi-conductive channel diode. The multi-layer heterojunction includes: a first channel layer 131 on the substrate 11 ; a first barrier layer 141 on the first channel layer 131 ; and a second channel layer on the first barrier layer 141 132 ; the second barrier layer 142 on the second channel layer 132 . A first two-dimensional electron gas 151 (a first conductive channel) is formed at the interface between the first channel layer 131 and the first barrier layer 141 , and the second channel layer 132 and the second barrier layer 142 are at the interface A second two-dimensional electron gas 152 (second conductive channel) is formed. Using a multi-conductive channel structure can further reduce the on-resistance of the GaN diode and the power consumption when the same current flows.

FIG. 10 is a flowchart of a method for fabricating a gallium nitride diode according to Embodiment 3 of the present invention. As shown in FIG. 10 , in this embodiment, steps 101 to 103 are the same as steps 41 to 43 in the first embodiment, and steps 108 to 1010 are the same as steps 46 to 48 in the first embodiment. This embodiment only describes the difference from the first embodiment.

Step 104 , forming a second channel layer on the first barrier layer.

The material of the second channel layer may be undoped gallium nitride. The second channel layer is formed on the substrate using a metal organic compound chemical vapor deposition process or a molecular beam epitaxy process.

Step 105 , forming a second barrier layer on the second channel layer, and a second two-dimensional electron gas is formed at the interface between the second barrier layer and the second channel layer.

A second barrier layer is formed on the second channel layer by using a metal organic compound chemical vapor deposition process or a molecular beam epitaxy process.

Step 106 , forming a cap layer on the second barrier layer.

A cap layer is formed on the second barrier layer. At this time, the second two-dimensional electron gas at the interface between the second channel layer and the second barrier layer under the cap layer and the first channel layer and the first barrier layer The first two-dimensional electron gas at the interface is depleted.

Step 107, etching part of the cap layer and the second barrier layer and the second channel layer thereunder.

The cap layer is etched by a photolithography process and a dry etching process. In order to form a good ohmic contact, chlorine-based etching can be used to etch the exposed second barrier layer and the second channel layer thereunder. At this time, the second channel layer and the second channel layer under the etched cap layer The second two-dimensional electron gas at the interface of the barrier layer and the first two-dimensional electron gas at the interface between the first channel layer and the first barrier layer are depleted, and only in the exposed first barrier layer region A first two-dimensional electron gas exists at the interface with the second channel layer.

As shown in FIG. 11A , FIG. 11A shows cross-sectional views corresponding to steps 104 to 107 .

Compared with the gallium nitride diode provided in the first embodiment of the present invention, the gallium nitride diode provided in the third embodiment can further reduce the on-resistance of the gallium nitride diode and when the same current flows, by introducing multiple conductive channels. power consumption.

The above are only the preferred embodiments of the present invention and the applied technical principles. The present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the protection scope of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and can also include more other equivalent embodiments without departing from the concept of the present invention. The scope is determined by the scope of the claims.

Claims (7)

1. A gallium nitride diode, comprising:

a substrate;

a first channel layer on the substrate;

a first barrier layer on the first channel layer, a first two-dimensional electron gas being formed at an interface of the first barrier layer and the first channel layer;

a capping layer structure on the first barrier layer;

the cathode is positioned on the first barrier layer on one side of the capping layer structure and/or extends into the first barrier layer, and a gap is arranged between the capping layer structure and the cathode;

the anode is positioned on the first barrier layer on the other side of the capping layer structure and/or extends into the first barrier layer, and the anode covers the upper surface of the capping layer structure;

wherein the anode comprises a first anode and a second anode;

the first anode is positioned on the first barrier layer on the other side of the capping layer structure and is in contact with the capping layer structure;

the second anode is positioned on the first anode and the capping layer structure; wherein,

the first anode forms ohmic contact with the first barrier layer, and the second anode forms Schottky contact with the capping layer structure;

the capping layer structure is made of indium gallium nitride or aluminum indium gallium nitride.

2. The gallium nitride diode according to claim 1, further comprising:

a second channel layer on the first barrier layer under the capping layer structure and between the capping layer structure and the cathode;

and a second barrier layer on the second channel layer between the capping layer structure and the second channel layer and between the capping layer structure and the cathode, wherein a second two-dimensional electron gas is formed at an interface of the second barrier layer and the second channel layer.

3. Gallium nitride diode according to claim 1 or 2, wherein the thickness of the capping layer structure is between 2 nm and 20 nm.

4. The gallium nitride diode according to claim 1 or 2, wherein surface regions of the first barrier layer in contact with the cathode and the anode are doped with impurities, respectively.

5. The GaN diode of claim 4, wherein the cathode and the anode are fabricated by the same process.

6. A method for manufacturing a gallium nitride diode is characterized by comprising the following steps:

providing a substrate;

forming a first channel layer on the substrate;

forming a first barrier layer on the first channel layer, the first barrier layer having a first two-dimensional electron gas formed at an interface with the first channel layer;

forming a capping layer structure on the first barrier layer, an

Forming a cathode on and/or extending into the first barrier layer on one side of the capping layer structure, a gap being provided between the capping layer structure and the cathode, an

Forming an anode on the first barrier layer on the other side of the capping layer structure and/or extending into the first barrier layer, wherein the anode covers the upper surface of the capping layer structure;

wherein the anode comprises a first anode and a second anode;

wherein the first anode forms an ohmic contact with the first barrier layer and the second anode forms a Schottky contact with the capping layer structure;

the capping layer structure is made of indium gallium nitride or aluminum indium gallium nitride.

7. The method of fabricating a gallium nitride diode according to claim 6, wherein after forming a first barrier layer on the first channel layer, the first barrier layer having a first two-dimensional electron gas formed at an interface with the first channel layer, the method further comprises:

forming a second channel layer on the first barrier layer;

forming a second barrier layer on the second channel layer, a second two-dimensional electron gas being formed at an interface of the second barrier layer and the second channel layer,

the forming a capping layer structure is formed on the second barrier layer.