CN105280725B - A kind of gallium nitride diode and preparation method thereof - Google Patents
A kind of gallium nitride diode and preparation method thereof Download PDFInfo
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- CN105280725B CN105280725B CN201510185726.1A CN201510185726A CN105280725B CN 105280725 B CN105280725 B CN 105280725B CN 201510185726 A CN201510185726 A CN 201510185726A CN 105280725 B CN105280725 B CN 105280725B
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- 229910002601 GaN Inorganic materials 0.000 title claims abstract description 79
- JMASRVWKEDWRBT-UHFFFAOYSA-N Gallium nitride Chemical compound [Ga]#N JMASRVWKEDWRBT-UHFFFAOYSA-N 0.000 title claims abstract description 76
- 238000002360 preparation method Methods 0.000 title abstract description 3
- 230000004888 barrier function Effects 0.000 claims abstract description 163
- 230000005533 two-dimensional electron gas Effects 0.000 claims abstract description 36
- 239000000758 substrate Substances 0.000 claims abstract description 24
- 238000000034 method Methods 0.000 claims description 40
- 230000008569 process Effects 0.000 claims description 21
- 229910052738 indium Inorganic materials 0.000 claims description 19
- APFVFJFRJDLVQX-UHFFFAOYSA-N indium atom Chemical compound [In] APFVFJFRJDLVQX-UHFFFAOYSA-N 0.000 claims description 19
- 238000004519 manufacturing process Methods 0.000 claims description 19
- 239000012535 impurity Substances 0.000 claims description 6
- AJGDITRVXRPLBY-UHFFFAOYSA-N aluminum indium Chemical compound [Al].[In] AJGDITRVXRPLBY-UHFFFAOYSA-N 0.000 claims description 4
- 239000000463 material Substances 0.000 description 27
- 238000005530 etching Methods 0.000 description 11
- 229910052751 metal Inorganic materials 0.000 description 8
- 239000002184 metal Substances 0.000 description 8
- 238000010586 diagram Methods 0.000 description 7
- 230000005641 tunneling Effects 0.000 description 5
- KLZUFWVZNOTSEM-UHFFFAOYSA-K Aluminium flouride Chemical compound F[Al](F)F KLZUFWVZNOTSEM-UHFFFAOYSA-K 0.000 description 4
- 238000005229 chemical vapour deposition Methods 0.000 description 4
- 238000001451 molecular beam epitaxy Methods 0.000 description 4
- 150000004767 nitrides Chemical class 0.000 description 4
- 150000002902 organometallic compounds Chemical class 0.000 description 4
- 229910018503 SF6 Inorganic materials 0.000 description 3
- RNQKDQAVIXDKAG-UHFFFAOYSA-N aluminum gallium Chemical compound [Al].[Ga] RNQKDQAVIXDKAG-UHFFFAOYSA-N 0.000 description 3
- 230000015556 catabolic process Effects 0.000 description 3
- 239000004065 semiconductor Substances 0.000 description 3
- 229910052710 silicon Inorganic materials 0.000 description 3
- 239000010703 silicon Substances 0.000 description 3
- SFZCNBIFKDRMGX-UHFFFAOYSA-N sulfur hexafluoride Chemical compound FS(F)(F)(F)(F)F SFZCNBIFKDRMGX-UHFFFAOYSA-N 0.000 description 3
- 229910002704 AlGaN Inorganic materials 0.000 description 2
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 2
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 2
- PMHQVHHXPFUNSP-UHFFFAOYSA-M copper(1+);methylsulfanylmethane;bromide Chemical compound Br[Cu].CSC PMHQVHHXPFUNSP-UHFFFAOYSA-M 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 238000001312 dry etching Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000008020 evaporation Effects 0.000 description 2
- 238000001704 evaporation Methods 0.000 description 2
- 239000011777 magnesium Substances 0.000 description 2
- 229910052749 magnesium Inorganic materials 0.000 description 2
- 238000001259 photo etching Methods 0.000 description 2
- 230000010287 polarization Effects 0.000 description 2
- 238000005215 recombination Methods 0.000 description 2
- 230000006798 recombination Effects 0.000 description 2
- 238000011084 recovery Methods 0.000 description 2
- 229910052594 sapphire Inorganic materials 0.000 description 2
- 239000010980 sapphire Substances 0.000 description 2
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 description 2
- 229910010271 silicon carbide Inorganic materials 0.000 description 2
- 238000004544 sputter deposition Methods 0.000 description 2
- 229960000909 sulfur hexafluoride Drugs 0.000 description 2
- FAQYAMRNWDIXMY-UHFFFAOYSA-N trichloroborane Chemical compound ClB(Cl)Cl FAQYAMRNWDIXMY-UHFFFAOYSA-N 0.000 description 2
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 1
- AUCDRFABNLOFRE-UHFFFAOYSA-N alumane;indium Chemical compound [AlH3].[In] AUCDRFABNLOFRE-UHFFFAOYSA-N 0.000 description 1
- 239000000460 chlorine Substances 0.000 description 1
- 229910052801 chlorine Inorganic materials 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 230000000779 depleting effect Effects 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000005468 ion implantation Methods 0.000 description 1
- 239000007769 metal material Substances 0.000 description 1
- 238000000206 photolithography Methods 0.000 description 1
- 230000008707 rearrangement Effects 0.000 description 1
- -1 silicon ions Chemical class 0.000 description 1
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Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
- H01L29/86—Types of semiconductor device ; Multistep manufacturing processes therefor controllable only by variation of the electric current supplied, or only the electric potential applied, to one or more of the electrodes carrying the current to be rectified, amplified, oscillated or switched
- H01L29/861—Diodes
- H01L29/872—Schottky diodes
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/02—Semiconductor bodies ; Multistep manufacturing processes therefor
- H01L29/06—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by their shape; characterised by the shapes, relative sizes, or dispositions of the semiconductor regions ; characterised by the concentration or distribution of impurities within semiconductor regions
- H01L29/0603—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by their shape; characterised by the shapes, relative sizes, or dispositions of the semiconductor regions ; characterised by the concentration or distribution of impurities within semiconductor regions characterised by particular constructional design considerations, e.g. for preventing surface leakage, for controlling electric field concentration or for internal isolations regions
- H01L29/0607—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by their shape; characterised by the shapes, relative sizes, or dispositions of the semiconductor regions ; characterised by the concentration or distribution of impurities within semiconductor regions characterised by particular constructional design considerations, e.g. for preventing surface leakage, for controlling electric field concentration or for internal isolations regions for preventing surface leakage or controlling electric field concentration
- H01L29/0611—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by their shape; characterised by the shapes, relative sizes, or dispositions of the semiconductor regions ; characterised by the concentration or distribution of impurities within semiconductor regions characterised by particular constructional design considerations, e.g. for preventing surface leakage, for controlling electric field concentration or for internal isolations regions for preventing surface leakage or controlling electric field concentration for increasing or controlling the breakdown voltage of reverse biased devices
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/02—Semiconductor bodies ; Multistep manufacturing processes therefor
- H01L29/06—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by their shape; characterised by the shapes, relative sizes, or dispositions of the semiconductor regions ; characterised by the concentration or distribution of impurities within semiconductor regions
- H01L29/0603—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by their shape; characterised by the shapes, relative sizes, or dispositions of the semiconductor regions ; characterised by the concentration or distribution of impurities within semiconductor regions characterised by particular constructional design considerations, e.g. for preventing surface leakage, for controlling electric field concentration or for internal isolations regions
- H01L29/0607—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by their shape; characterised by the shapes, relative sizes, or dispositions of the semiconductor regions ; characterised by the concentration or distribution of impurities within semiconductor regions characterised by particular constructional design considerations, e.g. for preventing surface leakage, for controlling electric field concentration or for internal isolations regions for preventing surface leakage or controlling electric field concentration
- H01L29/0638—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by their shape; characterised by the shapes, relative sizes, or dispositions of the semiconductor regions ; characterised by the concentration or distribution of impurities within semiconductor regions characterised by particular constructional design considerations, e.g. for preventing surface leakage, for controlling electric field concentration or for internal isolations regions for preventing surface leakage or controlling electric field concentration for preventing surface leakage due to surface inversion layer, e.g. with channel stopper
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
- H01L29/66007—Multistep manufacturing processes
- H01L29/66075—Multistep manufacturing processes of devices having semiconductor bodies comprising group 14 or group 13/15 materials
- H01L29/66083—Multistep manufacturing processes of devices having semiconductor bodies comprising group 14 or group 13/15 materials the devices being controllable only by variation of the electric current supplied or the electric potential applied, to one or more of the electrodes carrying the current to be rectified, amplified, oscillated or switched, e.g. two-terminal devices
- H01L29/6609—Diodes
- H01L29/66143—Schottky diodes
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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
Technical Field
The invention relates to the technical field of semiconductors, in particular to a gallium nitride diode and a manufacturing method thereof.
Background
Diodes are indispensable parts of a regulator, a rectifier, and an inverter as basic constituent units of electronic power. With the development of modern power electronics, diodes have made higher demands on high breakdown voltage, low power consumption, low leakage current and other properties.
The semiconductor material gallium nitride (GaN) has the characteristics of large forbidden band width, high heat conduction efficiency and large breakdown field strength, so that the gallium nitride device has the advantages of low on-resistance and high working frequency, and can meet the requirements of modern power electronic development on diodes.
Currently, diodes based on GaN materials have been developed considerably. Most of conventional GaN schottky diodes have rectifying characteristics due to a schottky barrier formed by a metal material and a semiconductor material in the diode. At this time, the electrons need to cross the schottky barrier to realize conduction, so the forward turn-on voltage is larger, generally larger than 1.5V. If the forward turn-on voltage is reduced, the schottky barrier needs to be reduced, but after the schottky barrier is reduced, when a reverse bias is applied to the diode, the leakage current will be increased, and the schottky barrier height is reduced and the leakage current is increased due to the image force effect. GaN schottky diodes are also in need of continuous improvement and innovation in the areas of improving breakdown voltage, reducing reverse leakage current, increasing forward current, and reducing turn-on voltage.
Disclosure of Invention
The invention aims to provide a gallium nitride diode and a manufacturing method thereof, which can realize low turn-on voltage and low reverse leakage.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the present invention discloses 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;
and 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 covers the upper surface of the capping layer structure.
Further, still include:
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.
Further, the capping layer structure is made of indium gallium nitride, aluminum indium gallium nitride or P-type indium gallium nitride.
Furthermore, the P-type indium gallium nitride is doped with magnesium.
Further, the thickness of the capping layer structure is 2 to 20 nanometers.
Further, surface regions of the first barrier layer in contact with the cathode and the anode are doped with impurities, respectively.
Further, the preparation process of the cathode and the anode is identical.
Further, the anode includes 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 an ohmic contact with the first barrier layer and the second anode forms a Schottky contact with the capping layer structure.
In a second aspect, the present invention discloses a method for manufacturing a gallium nitride diode, including:
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
And 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.
Further, 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 includes:
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.
According to the gallium nitride diode and the manufacturing method thereof provided by the embodiment of the invention, the cap layer structure is introduced, and part of the anode covers the upper surface of the cap layer structure, so that the anode above the cap layer structure controls the conduction and the disconnection 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, the rectification characteristic of the gallium nitride diode is realized, and the gallium nitride diode has the characteristics of low turn-on voltage, low conduction resistance, high forward conduction current, high reverse withstand voltage and low reverse leakage current.
Drawings
In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, a brief description is given below of the drawings used in describing the embodiments. It should be clear that the described figures are only views of some of the embodiments of the invention to be described, not all, and that for a person skilled in the art, other figures can be derived from these figures without inventive effort.
Fig. 1 is a cross-sectional view of a gan diode according to an embodiment of the present invention with the conduction channel turned off.
Fig. 2A is an energy band diagram of a gan diode without an external bias and without a capping layer structure according to an embodiment of the present invention.
Fig. 2B is a band diagram of a gan diode without an external bias voltage and with a capping layer structure made of ingan according to an embodiment of the present invention.
Fig. 2C is an energy band diagram of the gan diode provided by the first embodiment of the present invention when no external bias is applied and the material of the cap layer structure is P-type ingan.
Fig. 3 is a cross-sectional view illustrating recovery of a conduction channel of a gan diode according to an embodiment of the present invention.
Fig. 4 is a flowchart of a method for manufacturing a gan diode according to an embodiment of the invention.
Fig. 5A is a cross-sectional view of the first barrier layer formed on the first channel layer in the step of providing the substrate in the method for manufacturing the gan diode according to the embodiment of the invention, wherein the first barrier layer is formed at an interface between the first barrier layer and the first channel layer.
Fig. 5B is a cross-sectional view of a step of forming a cap layer on the first barrier layer in the method for fabricating a gan diode according to an embodiment of the invention.
Fig. 5C is a cross-sectional view corresponding to the step of etching the cap layer in the method for manufacturing the gan diode according to the embodiment of the present invention, and exposing the first barrier layers on the two sides of the etched cap layer.
Fig. 5D is a cross-sectional view of the step of simultaneously forming a cathode and a first anode on the first barrier layer exposed at the two sides of the etched cap layer in the method for manufacturing a gan diode according to the first embodiment of the present invention.
Fig. 5E is a cross-sectional view of the step of forming a second anode on the first anode and the etched cap layer in the method for manufacturing a gallium nitride diode according to the first embodiment of the present invention, where the second anode covers a portion of the etched upper surface of the cap layer.
Fig. 6 is a cross-sectional view of a gan diode according to a second embodiment of the present invention with the conduction channel turned off.
Fig. 7 is a flowchart of a method for manufacturing a gan diode according to a second embodiment of the invention.
Fig. 8A is a cross-sectional view corresponding to doping performed on the surface region of the first barrier layer exposed at the two sides of the cap layer after etching in the step of the method for manufacturing the gallium nitride diode according to the second embodiment of the present invention.
Fig. 9 is a cross-sectional view of a gan diode according to a third embodiment of the present invention with the conduction channel turned off.
Fig. 10 is a flowchart of a method for manufacturing a gan diode according to a third embodiment of the present invention.
Fig. 11A is a diagram illustrating a step of forming a second channel layer on the first barrier layer in the method for manufacturing a gan diode according to the third embodiment of the present invention, and a step of etching a portion of the cap layer and the second barrier layer and the second channel layer thereunder.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be fully described by the detailed description with reference to the accompanying drawings in the embodiments of the present invention. It is obvious that the described embodiments are a part of the embodiments of the present invention, not all embodiments, and all other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without inventive efforts fall within the scope of the present invention.
Firstly, for the gallium nitride diode provided by the embodiment of the inventionThe working principle is explained: 1) in the absence of applied voltage (V)ACAnd (0), generating negative polarization charges at an interface between the cap layer structure (the material may be InGaN, indium gallium nitride) and the first barrier layer (the material may be AlGaN, aluminum gallium nitride), enabling the energy band to move upwards, depleting the first Two-dimensional electron gas (2 DEG) at the interface between the first barrier layer (the material may be AlGaN) and the first channel layer (the material may be GaN), and turning off the gallium nitride diode. 2) When positive pressure is applied to the anode (V)AC>Vk), the conduction band at the interface of the first barrier layer and the first channel layer below the cap layer structure moves downwards, and when the conduction band is lower than the Fermi level, the first two-dimensional electron gas channel is recovered, and the gallium nitride diode is started. 3) When negative pressure is applied to the anode (V)AC<0) And the conduction band bottom at the interface of 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 condition of the capping layer structure to the 2DEG, and is independent of the Schottky barrier height. In addition, a non-doped InGaN cap layer structure is adopted, the upward shift amplitude of an energy band at the interface of the first barrier layer and the first channel layer below the cap layer structure is small, the starting voltage of the gallium nitride diode is small when the gallium nitride diode is conducted, and the power consumption of flowing the same current is low. The leakage of the gan diode consists of two parts: 1) leakage between the anode and the cathode on one side of the cap layer structure; 2) leakage between the anode and the cathode over the capping layer structure. As the reverse voltage increases, the width of the 2DEG depletion layer under the capping layer structure expands, and the leakage current 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 barrier height and width of the heterojunction diode are larger than those of the Schottky diode, and the barrier height is not influenced by image force. In principle, the leakage of the structure is determined by the recombination current generated by the depletion region and is much smaller than the tunneling current of a common diode.
The first embodiment is as follows:
fig. 1 is a cross-sectional view of a gan diode according to an embodiment of the present invention with the conduction channel turned off. As shown in fig. 1, the gallium nitride diode includes: the electron-emitting diode comprises 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 two-dimensional electron gas 151 formed at an interface of the first barrier layer 141 and the first channel layer 131, a capping structure 16 located on the first barrier layer 141, a cathode 17 located on the first barrier layer 141 on one side of the capping structure 16 and/or extending into the first barrier layer 141, a gap is arranged between the capping structure 16 and the cathode 17, an anode located on the first barrier layer 141 on the other side of the capping structure 16 and/or extending into the first barrier layer 141, and the anode covers the upper surface of the capping 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 capping layer structure 16, and the first anode 181 is in contact with the capping layer structure 16; second anode 182 is located over first anode 181 and capping 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, and the buffer layer 12 may serve to match the material of the substrate 11 and improve the quality of the first channel layer 131. The material of the buffer layer 12 may be undoped gallium nitride, aluminum nitride or other group III nitride.
The first barrier layer 141 and the first channel layer 131 form a heterojunction structure, and the first two-dimensional electron gas 151 is formed at an interface of 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 nitride.
The capping layer structure 16 may be made of indium gallium nitride, indium aluminum gallium nitride, or P-type indium gallium nitride, wherein the P-type indium gallium nitride may be doped with magnesium. The lower doping concentration of the P-type InGaN is weaker in the depletion degree of the 2EDG, namely the conduction band (E) at the channel formed by the 2EDGc) With Fermi level (E)f) The closer the distance, the lower the turn-on voltage of the gan diode. To achieve a lower turn-on voltage, the material of the capping layer structure 16 is preferably indium gallium nitride.
When the thickness of the capping layer structure 16 is greater than 2 nm, the lowest position of the conduction band (i.e., the conduction band bottom) at the interface of the first channel layer 131 and the first barrier layer 141 of the gan diode can move up to above the fermi level, so that the first two-dimensional electron gas 151 at the interface of the first channel layer 131 and the first barrier layer 141 below the capping layer structure 16 is completely exhausted, and meanwhile, in order to ensure that the gan diode has a small turn-on voltage (less than 1V), the thickness of the capping layer structure 16 should be controlled within 20 nm. Thus, the capping layer structure 16 may have a thickness in the range of 2 nanometers to 20 nanometers. The capping layer structure 16 can be adjusted to have a turn-on voltage of approximately +0V by adjusting the thickness of the capping layer structure 16, and the length of the capping layer structure 16 can be determined according to the design requirements of a specific gallium nitride diode.
The first anode 181 and the second anode 182 may be formed at the same time, together constituting an anode. The cathode 17 and the first anode 181 form ohmic contacts with the first barrier layer 141 and the first channel layer 131. Second anode 182 overlies the upper surface of capping layer structure 16 and forms a schottky contact with capping layer structure 16.
As shown in fig. 1, when the gan diode has no external bias, the polarization charges generated at the interface between the capping layer structure and the first barrier layer make the conduction band at the interface between the first channel layer and the first barrier layer under the capping layer structure move up, deplete the first two-dimensional electron gas at the interface between the first channel layer and the first barrier layer under the capping layer structure, and close the conduction channel of the gan diode.
Fig. 2A is an energy band diagram of a gan diode without an external bias and without a capping layer structure according to an embodiment of the present invention. Fig. 2B is a band diagram of a gan diode without an external bias voltage and with a capping layer structure made of ingan according to an embodiment of the present invention. Fig. 2C is an energy band diagram of the gan diode provided by the first embodiment of the present invention when no external bias is applied and the material of the cap layer structure is P-type ingan. Wherein E isCAnd EFRespectively representing the conduction band and the fermi level. As can be seen from fig. 2A, 2B and 2C, when the material of the capping layer structure is undoped indium gallium nitride, the conduction band bottom moves up,and the upward shift amplitude of the conduction band bottom when the material of the cap layer structure is indium gallium nitride is smaller than that when the material of the cap layer structure is P-type indium gallium nitride, namely the upward shift amplitude is close to the Fermi level. Because the smaller the upward shift amplitude of the conduction band bottom is, the lower the starting voltage is, therefore, when the material of the cap layer structure is indium gallium nitride, the starting voltage is smaller when the gallium nitride diode is conducted, and the on-state power consumption is lower. Therefore, the material of the capping layer structure in this embodiment is preferably indium gallium nitride.
Fig. 3 is a cross-sectional view illustrating recovery of a conduction channel of a gan diode according to an embodiment of the present invention. As shown in fig. 3, when the forward bias is applied to the gan diode, the conduction band at the interface between the first channel layer and the first barrier layer under the cap structure moves downward, and when the conduction band is lower than the fermi level, the first two-dimensional electron gas at the interface between the first channel layer and the first barrier layer under the cap structure recovers, and the conduction channel of the gan diode recovers.
When the gallium nitride diode is applied with reverse bias, the conduction band bottom at the interface of the first channel layer and the first barrier layer below the cap layer structure moves upwards, and the first two-dimensional electron gas at the interface of the first channel layer and the first barrier layer below the cap layer structure is exhausted. The leakage of the gan diode consists of two parts: 1) leakage between the anode and the cathode on one side of the cap layer structure; 2) leakage between the anode and the cathode over the capping layer structure. As the reverse voltage increases, the width of the 2DEG depletion layer under the capping layer structure expands, and the leakage current 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 barrier height and width of the heterojunction diode are larger than those of the Schottky diode, and the barrier height is not influenced by image force. In principle, the leakage of the structure is determined by the recombination current generated by the depletion region and is much smaller than the tunneling current of a common diode.
According to the gallium nitride diode provided by the embodiment of the invention, the anode above the capping layer structure controls the conduction and the disconnection of the first two-dimensional electron gas at the interface of the first channel layer and the first barrier layer below the capping layer structure, so that the rectification characteristic of the gallium nitride diode is realized, the barrier height and the depletion layer width of a heterojunction are improved in the reverse direction, and the reverse barrier lowering effect is avoided. Therefore, the gallium nitride diode has the characteristics of low turn-on voltage, low on resistance, high forward conducting 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 manufacturing a gan diode according to an embodiment of the invention. As shown in fig. 4, the method includes:
step 41, providing a substrate.
The material of the substrate may be silicon carbide, silicon or sapphire.
A first channel layer is formed on the substrate, step 42.
The material of the first channel layer may be undoped gallium nitride. And forming a first channel layer on the substrate by 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 comprise: a buffer layer is formed on a substrate. The buffer layer can serve to match the substrate material and improve the quality of the first channel layer. Wherein, the material of the buffer layer can be undoped gallium nitride, aluminum nitride or other III group nitrides.
And 43, forming a first barrier layer on the first channel layer, wherein the first two-dimensional electron gas is formed at the interface of the first barrier layer and the first channel layer.
A first barrier layer is formed on the first channel layer using a metal organic compound chemical vapor deposition process or a molecular beam epitaxy process.
As shown in fig. 5A, fig. 5A shows a cross-sectional view corresponding to step 41 to step 43.
Step 44 forms a cap layer on the first barrier layer.
As shown in fig. 5B, the cap layer 161 is formed on the first barrier layer 141, and at this time, the first two-dimensional electron gas at the interface of the first channel layer 131 and the first barrier layer 141 below the cap layer 161 is depleted.
And step 45, etching the cap layer, and exposing the first barrier layers on the two sides of the etched cap layer.
As shown in fig. 5C, the cap layer is etched by using a photolithography process and a dry etching process, and the first barrier layers 141 on the two sides of the etched cap layer 162 are exposed, at this time, the first two-dimensional electron gas at the interface between the first channel layer 131 and the first barrier layer 141 below the etched cap layer 162 is exhausted, and the first two-dimensional electron gas 151 exists only at the interface between the exposed first barrier layer region and the first channel layer.
Because the material of the cap layer is different from that of the first barrier layer, the etching of the cap layer can be accurately stopped on the first barrier layer in the process of etching the cap layer.
When the cap layer is made of InGaN, AlInGaN or P-type InGaN, a photoetching process and a selective etching process are adopted, and boron trichloride/sulfur hexafluoride (BCl) is used3/SF6) The plasma is used as etching gas to etch the cap layer, after the cap layer is etched, the boron trichloride/sulfur hexafluoride plasma can form aluminum trifluoride when contacting with the first barrier layer below, the volatility of the aluminum trifluoride is low, the aluminum trifluoride can be attached to the first barrier layer to protect the first barrier layer from being etched, and therefore the aluminum trifluoride can automatically stay on the first barrier layer after the cap layer is etched.
And step 46, forming a cathode and a first anode on the exposed first barrier layer at two sides of the etched cap layer and/or extending into the first barrier layer.
As shown in fig. 5D, the cathode 17 and the first anode 181 are formed on the exposed first barrier layer 141 on the two sides of the etched cap layer 162 and/or extend into the first barrier layer 141 by using a metal e-beam evaporation process or a metal sputtering process.
And 47, forming a second anode on the first anode and the etched cap layer, wherein the second anode covers part of the upper surface of the etched cap layer.
As shown in fig. 5E, a second anode 182 is formed over the first anode 181 and the partially etched cap layer 162 by using a metal E-beam evaporation process or a metal sputtering process, and the second anode 182 covers a portion of the upper surface of the partially etched cap layer 162.
The area of the portion of the anode formed in this step that covers the cap layer structure may be determined according to the design requirements of a particular gan diode.
And 48, etching the rest part of the etched cap layer which is not covered by the second anode to form a cap layer structure.
According to the gallium nitride diode provided by the embodiment of the invention, the 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 conduction and the disconnection of the first two-dimensional electron gas at the interface of the first channel layer and the first barrier layer below the cap layer structure, the rectification characteristic of the gallium nitride diode is realized, and the gallium nitride diode has the characteristics of low turn-on voltage, low conduction resistance, high forward conduction current, high reverse withstand voltage and low reverse leakage at the same time, and is simple in structure.
Example two:
fig. 6 is a cross-sectional view of a gan diode according to a second embodiment of the present invention with the conduction channel turned off. As shown in fig. 6, unlike the gan diode according to the first embodiment of the present invention, the gan diode according to the second embodiment of the present invention is formed by doping impurity into the surface regions of the first barrier layer 141 in contact with the cathode 17 and the first anode 181, respectively, to form the doped regions 19.
In this embodiment, the impurity may be silicon ions.
The first barrier layer doped with impurities forms an n-type heavily doped region, and then when metal electrodes are evaporated in the heavily doped region, because the doping concentration of the first barrier layer is high, the barrier width between the metal electrodes and the first barrier layer is low, and the electron tunneling probability is high, the resistance between the first barrier layer and the metal electrodes is low, good ohmic contact can be formed, and the metal electrodes are cathodes and anodes.
Fig. 7 is a flowchart of a method for manufacturing a gan diode according to a second embodiment 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 the first embodiment, and steps 77 to 79 are respectively the same as steps 46 to 48 in the first embodiment. The present embodiment only describes the differences from the first embodiment.
And 76, doping the surface area of the first barrier layer exposed at the two sides of the etched cap layer.
As shown in fig. 8A, an ion implantation process is performed to dope the surface regions of the first barrier layer 141 on both sides of the etched cap layer 162, so as to form a doped region 19.
Compared with the gallium nitride diode provided by the first embodiment of the invention, the gallium nitride diode provided by the second embodiment of the invention has the advantages that 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 by doping impurities in the surface regions of the first barrier layer in contact with the cathode and the anode respectively.
Example three:
fig. 9 is a cross-sectional view of a gan diode according to a third embodiment of the present invention with the conduction channel turned off. As shown in fig. 9, unlike the gan diode provided in the first embodiment of the present invention, the gan diode further includes: a second channel layer 132 on the first barrier layer 141 under the capping layer structure 16 and between the capping layer structure 16 and the cathode 17, a second barrier layer 142 on the second channel layer 132 between the capping layer structure 16 and the second channel layer 132 and between the capping layer structure 16 and the cathode 17, and a second two-dimensional electron gas 152 formed at an interface of the second barrier layer 142 and the second channel layer 132.
The second barrier layer 142 forms a heterojunction structure with the second channel layer 132, and a second two-dimensional electron gas 152 is formed at an interface of 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 nitride.
The capping layer structure 16 may be indium gallium nitride, aluminum indium gallium nitride, or P-type indium gallium nitride, and is preferably P-type indium gallium nitride. When the P-type indium gallium nitride is adopted, the cap layer structure is thinner, and the control capability of the anode on the conductive channel is better.
The gan diode provided by this embodiment uses a multilayer heterojunction structure to form a multi-conduction channel diode. The multilayer heterojunction includes: a first channel layer 131 on the substrate 11; a first barrier layer 141 on the first channel layer 131; a second channel layer 132 on the first barrier layer 141; a second barrier layer 142 on the second channel layer 132. The first channel layer 131 forms a first two-dimensional electron gas 151 (first conduction channel) at an interface with the first barrier layer 141, and the second channel layer 132 forms a second two-dimensional electron gas 152 (second conduction channel) at an interface with the second barrier layer 142. The adoption of the multi-conduction channel structure can further reduce the on-resistance of the gallium nitride diode and the power consumption when the same current flows.
Fig. 10 is a flowchart of a method for manufacturing a gan diode according to a third embodiment of the present invention. As shown in fig. 10, in the present 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. The present embodiment only describes the differences from the first embodiment.
Step 104 forms a second channel layer on the first barrier layer.
The material of the second channel layer may be undoped gallium nitride. And forming a second channel layer on the substrate by using a metal organic compound chemical vapor deposition process or a molecular beam epitaxy process.
And 105, forming a second barrier layer on the second channel layer, wherein a second two-dimensional electron gas is formed at the interface of the second barrier layer and the second channel layer.
And forming a second barrier layer 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.
And forming a cap layer on the second barrier layer, wherein the second two-dimensional electron gas at the interface of the second channel layer and the second barrier layer and the first two-dimensional electron gas at the interface of the first channel layer and the first barrier layer below the cap layer are exhausted.
Step 107, etching part of the cap layer and the second barrier layer and the second channel layer below the cap layer.
And etching the cap layer by utilizing a photoetching process and a dry etching process. In order to form good ohmic contact, the exposed second barrier layer and the second channel layer below the second barrier layer can be etched by adopting chlorine base, at the moment, the second two-dimensional electron gas at the interface of the second channel layer and the second barrier layer below the etched cap layer and the first two-dimensional electron gas at the interface of the first channel layer and the first barrier layer are exhausted, and the first two-dimensional electron gas exists only at the interface of the exposed first barrier layer region and the second channel layer.
As shown in fig. 11A, fig. 11A shows a cross-sectional view corresponding to step 104 to step 107.
Compared with the gan diode provided in the first embodiment of the present invention, the gan diode provided in the third embodiment of the present invention can further reduce the on-resistance of the gan diode and the power consumption when the same current flows through the gan diode by introducing the multiple conductive channels.
The foregoing is considered as illustrative of the preferred embodiments of the invention and technical principles employed. The present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in more detail by the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the present invention, and the scope of the present invention 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.
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