A gallium nitride device structure and method of fabricating the same
By irradiating GaN devices, the trapping effect of the epitaxial structure is modulated, which solves the problems of dynamic on-resistance decay and low breakdown voltage of GaN devices in high-voltage, high-power power electronic systems, thereby improving the reliability and stability of the devices.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-14
- Publication Date
- 2026-03-24
AI Technical Summary
Existing GaN devices in high-voltage, high-power power electronic systems suffer from problems such as high epitaxial material defect density and channel performance susceptible to trap effects, leading to dynamic on-resistance degradation and low breakdown voltage.
By irradiating GaN devices with preset doses and preset energies, defects are introduced into the epitaxial structure by irradiated particles, modulating the trapping effect of the epitaxial structure, thereby improving the dynamic resistance decay of planar devices and the breakdown voltage of vertical devices.
This improves the reliability and stability of GaN devices in high-voltage, high-power power electronic systems and expands their application in high-voltage, high-frequency fields.
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Abstract
Description
Technical Field
[0001] This application relates to the field of semiconductor manufacturing technology, and in particular to a gallium nitride device structure and its fabrication method. Background Technology
[0002] Gallium nitride (GaN), as a wide bandgap semiconductor material, has shown great application potential in high-frequency, high-power power electronic devices due to its excellent electron mobility, high breakdown voltage and good thermal conductivity. This has made GaN-based high electron mobility transistors (HEMTs) a core component of power electronic systems.
[0003] Currently, the mainstream technology for GaN devices involves planar devices formed through heteroepitaxial growth on substrates such as silicon, silicon carbide, and sapphire. Unlike traditional Si-based metal-oxide-semiconductor field-effect transistors (MOSFETs) in terms of carrier conduction, GaN devices primarily rely on a two-dimensional electron gas (2DEG) formed at the AlGaN / GaN heterojunction interface to operate, thereby enabling current conduction and transmission. Furthermore, the formation of this 2DEG does not depend on any material doping; a high concentration of 2DEG can be formed solely through the spontaneous polarization and piezoelectric polarization of the material at the AlGaN / GaN heterojunction interface.
[0004] Planar GaN devices based on heterogeneous substrates suffer from problems such as high defect density in epitaxial materials and channel performance susceptible to trap effects leading to dynamic on-resistance degradation, which fundamentally limits their application in high-voltage, high-power power electronic systems. Existing technologies, such as vertical GaN devices achieved through homoepitaxial growth on single-crystal GaN substrates, can solve the dynamic on-resistance degradation problem of planar GaN devices, giving them excellent electron mobility and high breakdown voltage characteristics. However, due to the electric field crowding effect at the edge of vertical GaN devices, the breakdown voltage of traditional vertical GaN devices is often lower than its theoretical limit, thus restricting the development of vertical GaN devices to higher voltage levels.
[0005] Therefore, how to provide a GaN device structure and its fabrication method that can address the shortcomings of existing GaN devices and improve the reliability and stability of GaN devices in high-voltage, high-power power electronic systems has become one of the technical problems that urgently need to be solved by those in the field. Summary of the Invention
[0006] This application aims to at least partially address one of the technical problems in the related art.
[0007] Therefore, the first objective of this application is to propose a gallium nitride device structure and its fabrication method, which can improve the reliability and stability of gallium nitride devices in high-voltage, high-power power electronic systems.
[0008] To achieve the above objectives, a first aspect of this application provides a method for fabricating a gallium nitride (GaN) device structure, comprising providing a GaN device, the GaN device comprising a substrate and an epitaxial structure stacked sequentially; placing the GaN device on an irradiation platform, and irradiating the GaN device with a preset dose and preset energy using an irradiation processing system to introduce defects in the epitaxial structure and modulate the trapping effect of the epitaxial structure.
[0009] Optionally, the irradiation treatment system performs irradiation treatment on the gallium nitride device with a preset dose and preset energy, including one or more combinations of proton irradiation treatment, electron irradiation treatment, and ultraviolet irradiation.
[0010] Optionally, the irradiation processing system further includes a first irradiation control component, which includes a silicon diode detector, a Faraday cup, and a quadrupole lens. The proton irradiation processing and / or the electron irradiation processing uses a silicon diode detector to monitor the energy of the irradiation beam, a Faraday cup to monitor the dose of the irradiation beam, and a quadrupole lens to defocus the radiation beam and achieve uniform radiation.
[0011] Optionally, the irradiation treatment system further includes a second irradiation control component, which includes an ultraviolet detector and a beam homogenizer. The ultraviolet irradiation treatment uses an ultraviolet detector to monitor the intensity of the irradiated ultraviolet radiation and a beam homogenizer to defocus the irradiated ultraviolet radiation and achieve uniform radiation. The ambient gas for the ultraviolet irradiation treatment of the gallium nitride device is O3.
[0012] Optionally, when the gallium nitride device is a planar gallium nitride device, the epitaxial structure includes a buffer layer and a channel layer formed by sequentially stacking carbon-doped gallium nitride and undoped gallium nitride; the step of modulating the trapping effect of the epitaxial structure is to make the carrier capture rate of the internal traps of the buffer layer less than the release rate.
[0013] Optionally, the step of irradiating the gallium nitride device with a preset dose and preset energy using an irradiation treatment system includes:
[0014] The epitaxial structure is subjected to proton irradiation treatment by the irradiation treatment system, and defects are introduced into the channel layer by utilizing the displacement effect of the proton irradiation.
[0015] The epitaxial structure is subjected to electron irradiation treatment using the irradiation treatment system, and a large amount of space charge is introduced into the buffer layer by the ionization effect of the electron irradiation; or,
[0016] The epitaxial structure is subjected to ultraviolet irradiation treatment by the irradiation treatment system, which repairs the surface defects of the epitaxial structure and provides energy for the release of internal trapped charge carriers in the buffer layer.
[0017] Optionally, the step of irradiating the gallium nitride device with a preset dose and preset energy using an irradiation treatment system includes:
[0018] The epitaxial structure is subjected to proton irradiation treatment with a first energy threshold and a first dose threshold by the irradiation treatment system, and defects are introduced in the channel layer by utilizing the displacement effect of the proton irradiation.
[0019] The epitaxial structure is subjected to proton irradiation treatment with a second energy threshold and a second dose threshold by the irradiation treatment system, and a large amount of space charge is introduced into the buffer layer by the ionization effect of the proton irradiation.
[0020] Optionally, when the gallium nitride device is a vertical gallium nitride device, the epitaxial structure includes a drift layer composed of unintentionally doped gallium nitride on the substrate, and the step of irradiation treatment to modulate the trap effect of the drift layer is to increase the resistance at a predetermined position on the edge of the drift layer.
[0021] Optionally, the step of irradiating the gallium nitride device with a preset dose and preset energy using an irradiation treatment system includes:
[0022] The electron irradiation treatment is performed on the predetermined edge position of the epitaxial structure by the irradiation treatment system. The displacement effect of the electron irradiation introduces defects in the predetermined edge position of the drift layer, thereby increasing the predetermined resistance of the edge of the drift layer.
[0023] To achieve the above objectives, a second aspect of this application provides a gallium nitride device structure, which is fabricated using any one of the methods described above.
[0024] The gallium nitride device structure and its fabrication method provided in this application have at least the following beneficial effects:
[0025] This application provides a gallium nitride (GaN) device structure and its fabrication method. The method first provides a GaN device, which includes a substrate and an epitaxial structure stacked sequentially. Then, the GaN device is subjected to irradiation treatment with a preset dose and preset energy. The irradiation treatment introduces defects in the epitaxial structure, thereby modulating the internal trap effect of the epitaxial structure and modulating the electrical performance of the GaN device. This improves the reliability and stability of the GaN device in high-voltage and high-frequency applications.
[0026] When gallium nitride (GaN) devices are planar GaN devices, irradiation treatment causes the internal traps of the epitaxial structure to have a lower carrier capture rate than release rate, thereby improving the dynamic resistance degradation of planar GaN devices and enhancing their operational stability and reliability. Simultaneously, the irradiation process does not damage other electrical properties of planar GaN devices, expanding their applications in high-voltage and high-frequency fields.
[0027] When gallium nitride (GaN) devices are vertical GaN devices, irradiation introduces defects into the epitaxial structure, increasing the resistivity of the epitaxial structure at the preset irradiation location. This promotes the lateral distribution of the electric field in the device, reduces electric field concentration, and makes the electric field more uniform. Consequently, it improves the breakdown voltage of vertical GaN devices and expands the application of irradiated vertical GaN devices in high-voltage and high-frequency fields.
[0028] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description
[0029] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:
[0030] Figure 1 This is a schematic flowchart illustrating a method for fabricating a gallium nitride device structure according to an embodiment of this application.
[0031] Figure 2 This is a schematic diagram of the irradiation process of a planar gallium nitride device structure according to an embodiment of this application.
[0032] Figure 3 This is a schematic diagram of the process flow for fabricating a planar gallium nitride device structure according to an embodiment of this application.
[0033] Figure 4 This is a schematic diagram of the irradiation process of a vertical gallium nitride device structure according to an embodiment of this application.
[0034] 100 Substrate; 200 Epitaxial structure; 210 Nucleation layer; 220 Buffer layer; 230 Channel layer; 240 Barrier layer; 300 Epitaxial structure; 310 First gallium nitride layer; 320 Second gallium nitride layer; 330 Third gallium nitride layer; 331 Edge termination; 332 P-type heavily doped region; 410 Anode of contact electrode; 420 Cathode of contact electrode. Detailed Implementation
[0035] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.
[0036] Currently, the mainstream technology for GaN devices is planar devices that are heteroepitaxially grown on substrates such as silicon, silicon carbide, and sapphire. These devices mainly rely on the two-dimensional electron gas (2DEG) formed at the AlGaN / GaN heterojunction interface in the epitaxial structure as a current channel to achieve current conduction and transmission in the device. Moreover, the formation of the two-dimensional electron gas does not rely on any material doping, but is formed solely through the spontaneous polarization and piezoelectric polarization of the material at the AlGaN / GaN heterojunction interface. This enables GaN devices to demonstrate great application potential in high-frequency, high-power power electronic systems.
[0037] However, planar GaN devices based on heterogeneous substrates have a high defect density in the epitaxial material, and the channel performance is easily affected by the trap effect, which in turn causes changes in the 2DEG concentration, leading to an increase in the dynamic on-resistance of the device. This affects the stability and reliability of planar GaN devices, and fundamentally limits their application in high-voltage, high-power power electronic systems.
[0038] Existing technologies, through homoepitaxial development on single-crystal GaN substrates, have created vertical GaN devices where the current conduction and transmission channels are located inside the epitaxial structure. This makes them less susceptible to defects and thus less prone to increased dynamic on-resistance. However, the electric field congestion effect at the edges of vertical GaN devices often results in a breakdown voltage that is lower than the theoretical limit, which limits the development of vertical GaN devices to higher voltage levels.
[0039] Based on the above problems, this application provides a GaN device structure and its fabrication method. By subjecting the GaN device to multiple irradiation treatments and precisely controlling the irradiation parameters and process, the interaction between the internal traps and charge carriers of the GaN epitaxial structure is modulated by irradiated particles, thereby suppressing the dynamic resistance decay of planar GaN devices and improving the breakdown voltage of vertical GaN devices.
[0040] According to one aspect of this application, a method for fabricating a GaN device structure is provided, such as... Figure 1 As shown, the method includes the following steps:
[0041] S1 provides a GaN device comprising a substrate and an epitaxial structure stacked sequentially;
[0042] S2, the GaN device is placed on an irradiation platform, and the epitaxial structure of the GaN device is irradiated with a preset dose and preset energy using an irradiation treatment system. By introducing defects into the epitaxial structure, the trapping effect of the epitaxial structure is modulated, thereby improving the electrical performance of the GaN device.
[0043] In some embodiments, such as Figure 2 As shown, when the GaN device is a planar GaN device, the irradiation treatment system controls the planar GaN device to be irradiated with a preset irradiation dose and preset irradiation energy, so that the carrier capture rate of the internal trap of the epitaxial structure 200 is less than the release rate.
[0044] Irradiation treatment induces displacement and ionization effects at different locations on the epitaxial structure 200 of the planar GaN device. The ionization effect alters the trap state within the epitaxial structure 200, reducing the trap's carrier capture rate. The displacement effect introduces new defects into the epitaxial structure 200, and the tiny leakage current channels created by these newly introduced defects facilitate the release of trapped carriers from the traps within the epitaxial structure 200.
[0045] Therefore, by irradiating planar GaN devices, the irradiation system modulates the trapping effect of the epitaxial structure 200 of the planar GaN device, making the carrier capture rate of the internal traps of the epitaxial structure 200 less than the release rate. This improves the dynamic resistance degradation of the planar GaN device, thereby enhancing its operational stability and reliability. Simultaneously, the irradiation process does not damage other electrical properties of the planar GaN device, expanding its application in high-voltage and high-frequency fields.
[0046] As an example, substrate 100 may be composed of silicon (Si), silicon carbide (SiC), sapphire (Al2O3), or any other suitable substrate material for epitaxial growth of group III-V material layers. For substrate materials other than bulk gallium nitride (GaN), it is difficult to directly epitaxially grow high-quality GaN semiconductor crystal layers on substrate 100 due to poor lattice matching between GaN and the substrate material.
[0047] The epitaxial structure 200 can be composed of a nucleation layer 210, a buffer layer 220, a channel layer 230, and a barrier layer 240 stacked sequentially. The nucleation layer 210 is deposited on the surface of the substrate 100 and provides a growth surface for the subsequent epitaxial growth of a high-quality gallium nitride (GaN) layer, thereby alleviating lattice mismatch between GaN and non-GaN substrate materials and reducing the defect rate during GaN epitaxy. The nucleation layer 210 can be gallium nitride (GaN), aluminum gallium nitride (AlGaN), aluminum nitride (AlN), or any other suitable material for growing GaN. The buffer layer 220 and the channel layer 230 are GaN material layers sequentially grown on the surface of the nucleation layer 210 using thin-film deposition technology. The buffer layer 220 is composed of carbon-doped GaN material, and the channel layer 230 is formed on top of the buffer layer 220 and is composed of undoped GaN material. Introducing carbon into gallium nitride-based material layers can increase the resistivity of the gallium nitride layer. The barrier layer 240 is an electron supply layer and can be formed epitaxially on the channel layer 230 using thin-film deposition techniques. The barrier layer 240 can be made of aluminum gallium nitride (Al₂O₃). x Ga 1-x N), Indium aluminum nitride (In) x Al 1-x N) or any other material suitable for forming a heterojunction with the channel layer 230.
[0048] The aforementioned thin film deposition techniques include, but are not limited to, chemical vapor deposition (CVD), hydride vapor phase epitaxy (HVPE), atomic layer deposition (ALD), molecular beam epitaxy (MBE), or combinations thereof. Chemical vapor deposition further includes metal-organic chemical vapor deposition (MOCVD), low-pressure chemical vapor deposition (LPCVD), plasma-enhanced chemical vapor deposition (PECVD), and atomic layer chemical vapor deposition (ALCVD).
[0049] Contact electrodes are formed on barrier layer 240 and may include source electrodes, drain electrodes, and gate electrodes, with the gate electrode formed between the source and drain electrodes. The source and drain electrodes, formed on barrier layer 240, may be composed of titanium (Ti) / silicon (Si) / nickel (Ni), titanium (Ti) / aluminum (Al) / nickel (Ni), or any other suitable material that forms an ohmic contact with barrier layer 240. The gate electrode is also formed on barrier layer 240 and may be composed of any material that forms a non-ohmic contact with barrier layer 240 (a contact that does not exhibit linear IV characteristics).
[0050] While introducing carbon into gallium nitride (GaN) can increase the resistivity of the GaN buffer layer 220, the growth conditions for carbon introduction in GaN directly conflict with the necessary growth conditions for high-quality GaN. This results in epitaxially grown carbon-doped GaN (c-GaN) exhibiting poor crystal quality and morphology, and makes it difficult to grow thick layers of carbon-doped GaN, thus limiting the electrical breakdown performance of GaN devices. Furthermore, the higher structural defect density present in GaN with higher carbon doping concentrations can also lead to poor device performance, such as larger leakage current and increased power consumption in the device's off-state.
[0051] Therefore, by irradiating the buffer layer 220 of the planar GaN device using an irradiation treatment system, the trapping effect of the epitaxial structure 200 is modulated, making the carrier capture rate of the internal traps of the epitaxial structure 200 less than the release rate. This improves the dynamic resistance decay of the planar GaN device, thereby enhancing its operational stability and reliability. Specifically, the irradiation treatment can include one or more combinations of proton irradiation, electron irradiation, and ultraviolet irradiation.
[0052] As an example, step S2, which uses irradiation treatment to reduce the carrier capture rate of the internal traps of the epitaxial structure 200 to less than the release rate, can be a combination of proton irradiation and electron irradiation. First, the epitaxial structure 200 is subjected to proton irradiation using an irradiation system. The displacement effect of proton irradiation introduces defects into the channel layer 230 composed of unintentionally doped gallium nitride. The tiny leakage current channels generated by these newly introduced defects promote the release of captured carriers from the internal traps of the buffer layer 220 composed of intentionally doped gallium nitride. Then, the epitaxial structure 200 is subjected to electron irradiation using the same system. The ionization effect of electron irradiation introduces a large amount of space charge into the buffer layer 220. This space charge affects the internal electric field distribution and, through electric field modulation, shields the carrier capture of the internal traps of the buffer layer 220. This directly interacts with the internal traps of the buffer layer 220, causing the traps to reach saturation, thereby reducing the carrier capture rate of the internal traps of the buffer layer 220.
[0053] Specifically, the irradiation processing system may include a first irradiation control component consisting of a silicon diode detector, a Faraday cup, and a quadrupole lens. The proton irradiation processing and / or electron irradiation processing respectively use a silicon diode detector to monitor and control the energy of the irradiation beam, use a Faraday cup to monitor and control the dose of the irradiation beam, and use a quadrupole lens to defocus the radiation beam and achieve uniform radiation.
[0054] As an example, step S2, which uses irradiation treatment to reduce the carrier capture rate of the internal traps of the epitaxial structure 200 to less than the release rate, can be a combination of proton irradiation and ultraviolet irradiation. First, the displacement effect of proton irradiation introduces defects into the channel layer 230. The tiny leakage current channels generated by these newly introduced defects promote the release of captured carriers by the internal traps of the buffer layer 220. Then, the epitaxial structure is subjected to ultraviolet irradiation through the irradiation system. The annealing effect of ultraviolet irradiation repairs the defects or damage caused by proton irradiation to the device surface. Simultaneously, the radiation energy of ultraviolet irradiation provides energy for the release of carriers by the internal traps of the buffer layer 220, thereby promoting the release of captured carriers by the internal traps of the buffer layer 220 and reducing the carrier capture rate of the internal traps of the buffer layer 220.
[0055] The irradiation processing system also includes a second irradiation control component consisting of an ultraviolet detector and a beam homogenizer. The ultraviolet irradiation processing uses an ultraviolet detector to monitor and control the intensity of the irradiated ultraviolet radiation, and a beam homogenizer to defocus the irradiated ultraviolet radiation and achieve uniform radiation.
[0056] Furthermore, the ambient gas for ultraviolet irradiation treatment of planar GaN devices is O3. Using ultraviolet irradiation treatment of planar GaN devices in an O3 environment can also dissociate impurity molecules introduced during the fabrication process of planar GaN devices through ultraviolet radiation, and oxidize them with oxygen atoms to form volatile by-products, thereby achieving interface cleaning of planar GaN devices.
[0057] As an example, step S2, which involves irradiation treatment to reduce the carrier capture rate of the internal traps of the epitaxial structure 200 to less than the release rate, can be a combination of multiple gradient proton irradiation treatments. First, the epitaxial structure 200 is subjected to proton irradiation at a first energy threshold and a first dose threshold using an irradiation treatment system. The displacement effect of proton irradiation introduces defects into the channel layer 230. The tiny leakage current channels generated by these newly introduced defects promote the release of captured carriers from the internal traps of the buffer layer 220. Then, the epitaxial structure 200 is subjected to proton irradiation at a second energy threshold and a second dose threshold using the same irradiation treatment system. The ionization effect of proton irradiation introduces a large amount of space charge into the buffer layer 220. This space charge affects the internal electric field distribution of the buffer layer 220, modulating the electric field to shield the carrier capture by the internal traps of the buffer layer 220. This directly interacts with the internal traps of the buffer layer 220, causing them to reach saturation and thus reducing the carrier capture rate of the internal traps of the buffer layer 220.
[0058] As an example, such as Figure 3As shown, the specific steps of the fabrication method for a planar GaN device structure may include:
[0059] Step S1-0 is performed to provide a GaN device, which includes a substrate and an epitaxial structure.
[0060] Perform step S1-1 to clean and oxidize the surface of the epitaxial structure.
[0061] Perform steps S1-2 to form a passivation film on the epitaxial structure. The passivation film includes, but is not limited to, a SiO2 passivation film.
[0062] Then, step S2-0 is executed, in which the GaN device epitaxial structure is irradiated with a preset dose and preset energy using an irradiation treatment system.
[0063] Step S2-1 involves removing the passivation film from the epitaxial structure surface using dry or wet etching, or chemical etching methods, followed by surface passivation, cleaning, and drying of the exposed epitaxial structure surface. The passivation process does not include thermal annealing to prevent the repair of irradiation-induced defects during high-temperature processing.
[0064] Step S3 is performed to form a P-type doped GaN thin film on the surface of the epitaxial structure, and the P-type doped GaN thin film is patterned and etched based on a chlorine-based ICP process to form a P-GaN layer.
[0065] Step S4 is performed to form a passivation layer on the epitaxial structure, and the passivation layer covers the surface of the epitaxial structure and encapsulates the P-GaN layer.
[0066] Step S5 is performed to etch the passivation layer to form a first window that exposes a portion of the upper surface of the P-GaN layer, and a second and third window that expose a portion of the upper surface of the epitaxial structure. The second and third windows are located on opposite sides of the P-GaN layer.
[0067] Step S6 is performed to deposit metal in the second window and the third window respectively to form an ohmic contact layer in the second window and the third window.
[0068] Step S7 is performed, where ion implantation is carried out at the outer edges of the second and third windows based on the ion implantation process to form an isolation region between adjacent cells within the GaN device.
[0069] Step S8 is performed to form a contact electrode based on a metal deposition process, including forming a gate electrode on a P-GaN layer exposed in a first window, forming a source electrode on an ohmic contact layer exposed in a second window, and forming a drain electrode on an ohmic contact layer exposed in a third window. The gate electrode forms a Schottky contact with the P-GaN layer, and the source electrode and drain electrode respectively form ohmic contacts with the surface of the epitaxial structure through the ohmic contact layer.
[0070] It should be noted that this application does not specifically limit the direction of irradiation treatment for the epitaxial structure. The above examples and their illustrations 2 and 3 are as described above. Figure 3 In the process, the direction of irradiation of the epitaxial structure 200 is top irradiation. However, the direction of irradiation of the epitaxial structure 200 can be including but not limited to top irradiation. For example, bottom irradiation or side irradiation can also be used to irradiate the epitaxial structure 200. Steps S1-2 and S2-1 can be omitted.
[0071] Furthermore, the specific type of GaN device is not specifically limited in the above embodiments, including but not limited to enhancement-mode (E-mode) devices and depletion-mode (D-mode) devices. Those skilled in the art only need to make adaptive adjustments to the above process according to the specific device type. For example, depletion-mode devices are omitted. Figure 3 Step S3 is sufficient and will not be elaborated here.
[0072] In other embodiments, such as Figure 4 As shown, when the GaN device is a vertical GaN device, the irradiation treatment system irradiates the vertical GaN device with a preset irradiation dose and preset irradiation energy. This will cause a displacement effect at a preset position (i.e., edge terminal 331) on the edge of the drift layer of the vertical GaN device, introducing new defects and modulating the trap effect on the epitaxial structure 300 of the vertical GaN device. This increases the resistivity of the drift layer at the edge terminal 331, promotes the lateral distribution of the device's electric field, reduces the crowding effect caused by electric field concentration, makes the electric field more uniform, and improves the breakdown voltage of the vertical GaN device. This, in turn, expands the application of irradiated vertical GaN devices in high voltage and high frequency fields.
[0073] As an example, the vertical gallium nitride epitaxial structure 300 may include a first gallium nitride layer 310, a second gallium nitride layer 320 and a third gallium nitride layer 330 sequentially stacked on the substrate 100.
[0074] The first gallium nitride layer 310 can be an N-type heavily doped layer (N... +-GaN) to facilitate ohmic contact with substrate 100. A second gallium nitride layer 320 and a third gallium nitride layer 330 are sequentially formed on top of the first gallium nitride layer 310. These layers may be unintentionally gallium-doped and serve as drift layers for the epitaxial structure 300. Because the coefficients of thermal expansion (CTE) of the first gallium nitride layer 310 and the second gallium nitride layer 320 match those of the substrate 100, the second gallium nitride layer 320 can be grown to a relatively thick thickness while maintaining good crystal quality. In other embodiments, the epitaxial structure 300 also includes an interface layer between the first gallium nitride layer 310 and the second gallium nitride layer 320. This interface layer may comprise materials such as aluminum gallium nitride or indium gallium nitride. The third gallium nitride layer 330 is formed on top of the second gallium nitride layer 320 and includes edge terminals 331 located at the edges and P-type heavily doped regions 332 (P-type doped regions) located between the edge terminals 331. + -GaN). The edge terminal 331 and the heavily p-doped region 332 can also be coupled to the drift layer, and a portion of the drift layer is converted to form a third gallium nitride layer 330, for example, by doping with magnesium ions to form opposing first and second edge terminals at the edge of the second gallium nitride. The anode 410 in the contact electrode is located on the heavily p-doped region 332 and extends to cover part of the edge terminal 331, and the cathode 420 in the contact electrode is located on the side of the substrate 100 away from the epitaxial structure 300.
[0075] As an example, the step of modulating the internal trapping effect of the drift layer by irradiation treatment in step S2 is to perform electron irradiation treatment with preset energy and preset dose on the edge terminal 331 of the epitaxial structure 300. The displacement effect of electron irradiation is used to introduce a large number of defects in the edge terminal 331. The newly introduced defects combine with the charge carriers, so that the corresponding region of the edge terminal 331 obtains a larger resistivity, promotes the lateral distribution of the electric field of the epitaxial structure 300, reduces the electric field concentration, makes the electric field uniform, and improves the breakdown voltage of the device.
[0076] In addition, the newly injected electrons can temporarily act as charge carriers in the conduction process of the device after entering the drift layer, replenishing the lost charge carrier concentration and thus reducing the on-resistance.
[0077] It should be noted that the term "layer" mentioned above should be understood to mean that a layer can include multiple sublayers that form the layer of interest. Therefore, the term "layer" is not intended to refer to a single layer composed of a single material, but rather encompasses one or more materials layered in a composite manner to form the desired structure. Various variations, modifications, and substitutions will be apparent to those skilled in the art.
[0078] According to a second aspect of this application, a GaN device structure is also provided, which is fabricated using the fabrication method of the GaN device structure described in any of the above embodiments.
[0079] In summary, this application provides a GaN device structure and its fabrication method, including providing a GaN device and then subjecting the GaN device to irradiation treatment with a preset dose and preset energy. By introducing defects into the epitaxial structure 300 of the GaN device through irradiation treatment, the internal trapping effect of the epitaxial structure is modulated, thereby achieving modulation of the electrical properties of the GaN device and expanding its application in high-voltage and high-frequency fields.
[0080] When the GaN device is a planar GaN device, irradiation treatment causes the internal traps of the epitaxial structure 300 to have a lower carrier capture rate than release rate, thereby improving the dynamic resistance degradation of the planar GaN device and thus enhancing its operational stability and reliability. Simultaneously, the irradiation process does not damage other electrical properties of the planar GaN device, expanding its application in high-voltage and high-frequency fields.
[0081] When the GaN device is a vertical GaN device, the irradiation process introduces defects into the epitaxial structure 300, thereby increasing the resistivity of the epitaxial structure 300 at the preset irradiation position. This promotes the lateral distribution of the electric field in the device, reduces electric field concentration, and makes the electric field more uniform. As a result, the breakdown voltage of the vertical GaN device is improved, and the application of irradiated vertical GaN devices in high voltage and high frequency fields is expanded.
[0082] In the foregoing description of the embodiments, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of those different embodiments or examples.
[0083] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.
Claims
1. A method for fabricating a gallium nitride device structure, characterized in that, include: A gallium nitride device is provided, the gallium nitride device comprising a substrate and an epitaxial structure stacked sequentially; The gallium nitride device is placed on an irradiation platform and irradiated with a preset dose and preset energy using an irradiation processing system to introduce defects into the epitaxial structure and modulate the trapping effect of the epitaxial structure. When the gallium nitride device is a planar gallium nitride device, the epitaxial structure includes a buffer layer and a channel layer formed by sequentially stacking carbon-doped gallium nitride and undoped gallium nitride. The irradiation treatment includes a combination of proton irradiation treatment and ultraviolet irradiation treatment, so that the carrier capture rate of the internal traps of the buffer layer is less than the release rate. The combined treatment steps of proton irradiation and ultraviolet irradiation include: The epitaxial structure is subjected to proton irradiation treatment by the irradiation treatment system, and defects are introduced into the channel layer by utilizing the displacement effect of the proton irradiation. The epitaxial structure is subjected to ultraviolet irradiation treatment by the irradiation treatment system, which repairs the surface defects of the epitaxial structure and provides energy for the release of charge carriers from the internal traps of the buffer layer.
2. The preparation method according to claim 1, characterized in that, The irradiation processing system further includes a first irradiation control component, which includes a silicon diode detector, a Faraday cup, and a quadrupole lens. The proton irradiation processing uses a silicon diode detector to monitor the energy of the irradiation beam, a Faraday cup to monitor the dose of the irradiation beam, and a quadrupole lens to defocus the radiation beam and achieve uniform radiation.
3. The preparation method according to claim 1, characterized in that, The irradiation treatment system further includes a second irradiation control component, which includes an ultraviolet detector and a beam homogenizer. The ultraviolet irradiation treatment uses an ultraviolet detector to monitor the intensity of the irradiated ultraviolet radiation and a beam homogenizer to defocus the irradiated ultraviolet radiation and achieve uniform radiation. The ambient gas for the ultraviolet irradiation treatment of the gallium nitride device is O3.
4. A gallium nitride device structure, characterized in that, It is prepared by the method of preparing the gallium nitride device structure according to any one of claims 1 to 3.