Epitaxial layer structure of gallium nitride power device
By introducing a superimposed structure of Si-containing and Al-containing material layers into the epitaxial layer of gallium nitride power devices, the problems of voltage withstand and resistance of high-resistance gallium nitride layers are solved, and device performance with high voltage withstand and low leakage current is achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-02
- Publication Date
- 2026-04-14
AI Technical Summary
The existing epitaxial structure of high-resistivity gallium nitride layers remains a concern in the industry, affecting the breakdown voltage and resistance performance of devices.
By introducing a superimposed structure of Si-containing and Al-containing material layers into the epitaxial layer of gallium nitride power devices, a high-resistivity GaN layer is formed, avoiding additional Fe and C sources, reducing defect density, and optimizing device performance.
It significantly improves the resistance of gallium nitride layers and the breakdown voltage characteristics of devices, avoids the memory effect and dynamic performance instability caused by doping, and optimizes the electrical performance of devices.
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Figure CN224124492U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of semiconductor materials and devices, and in particular to an epitaxial layer structure for gallium nitride power devices. Background Technology
[0002] Gallium nitride (GaN) materials exhibit significantly superior performance compared to first- and second-generation semiconductor materials such as silicon (Si), germanium (Ge), and gallium arsenide (GaAs) in high-power, high-temperature, high-frequency, and radiation-resistant microelectronics applications, as well as short-wavelength optoelectronics. Specifically, in GaN heterojunction structures (typically AlGaN / GaN), the strong spontaneous polarization and piezoelectric polarization effects of the epitaxially grown structure along the Ga plane lead to a high concentration of two-dimensional electron gas (2DEG) at the AlGaN / GaN heterojunction interface, resulting in lower on-resistance in GaN devices. Furthermore, at the same voltage rating, GaN is more suitable for fabricating high-efficiency power electronic devices, particularly high electron mobility transistors (HEMTs) with lateral structures. Their on-resistance is 1-2 orders of magnitude lower than that of Si devices, and compared to SiC devices, which are also third-generation semiconductor materials, their on-resistance is reduced by 1 / 2 to 1 / 3.
[0003] Besides the low on-resistance of 2DEG, the high-resistivity gallium nitride layer is also crucial for high-voltage-tolerant devices. Currently, the epitaxial structure of high-resistivity gallium nitride layers remains a focus of industry attention. Utility Model Content
[0004] Therefore, in order to overcome at least some of the defects and deficiencies in the prior art, this utility model provides a gallium nitride power device epitaxial layer structure, which effectively improves the resistance of the gallium nitride layer and the withstand voltage characteristics of the gallium nitride device.
[0005] Specifically, this embodiment of the invention provides an epitaxial layer structure for a gallium nitride power device, comprising, from bottom to top, a substrate, a high-resistivity structural layer, a high-resistivity GaN layer, a channel layer, and a barrier layer. The high-resistivity structural layer includes a Si-containing material layer and an Al-containing material layer, with the Al-containing material layer located between the high-resistivity GaN layer and the Si-containing material layer. The Al-containing material layer comprises Al and N elements. The high-resistivity GaN layer is an undoped layer.
[0006] As can be seen from the above, the technical features of this utility model can have one or more of the following beneficial effects: A high-resistivity gallium nitride epitaxial layer is achieved by combining a Si-containing material layer and an Al-containing material layer, effectively improving the resistance of the gallium nitride layer and the breakdown voltage characteristics of gallium nitride devices, meeting the high breakdown voltage requirements of gallium nitride power devices. Furthermore, a high-resistivity gallium nitride epitaxial layer can be achieved without additional Fe or C doping sources. Simultaneously, the epitaxial layer contains no Fe element and has a low C content, avoiding the memory effect of Fe sources and the instability of device dynamic performance caused by C doping instability; and reducing the defect density of the gallium nitride layer, thereby optimizing device performance. Attached Figure Description
[0007] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0008] Figure 1 A schematic diagram of the epitaxial layer structure of a gallium nitride power device provided in this embodiment of the present invention;
[0009] Figure 2 for Figure 1 A schematic diagram of another embodiment of the epitaxial layer structure of a gallium nitride power device;
[0010] Figure 3 for Figure 1 A schematic diagram of another embodiment of the epitaxial layer structure of a gallium nitride power device;
[0011] Figure 4 for Figure 1 A schematic diagram of another embodiment of the epitaxial layer structure of a gallium nitride power device;
[0012] Figure 5 for Figure 1 Secondary ion mass spectrometry elemental analysis diagram of the epitaxial layer structure of gallium nitride power devices;
[0013] Figure 6 for Figure 1 A comparative analysis of the resistance values of GaN layers with medium to high resistance values;
[0014] Figure 7 for Figure 1 A comparative analysis of experiments on gallium nitride power devices fabricated with epitaxial layer structures and gallium nitride power devices fabricated with high-resistivity GaN layers doped with C.
[0015] [Explanation of Key Figure Markings]
[0016] 1: Substrate; 2: High resistivity structure layer; 21: Si-containing material layer; 210: First Si layer; 211: Second Si layer; 22: Al-containing material layer; 220: First Al material layer; 221: Second Al material layer; 3: High resistivity GaN layer; 4: Channel layer; 5: Barrier layer; 6: Isolation layer; 7: Cap layer. Detailed Implementation
[0017] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. Based on the embodiments described in this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.
[0018] In this embodiment of the invention, the use of terms such as "first" and "second" is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features.
[0019] In this utility model, reference is made to Figure 1 As shown, the epitaxial layer structure of a gallium nitride power device provided in this embodiment includes: a substrate 1, a high-resistivity structure layer 2, a high-resistivity GaN layer 3, a channel layer 4, and a barrier layer 5, stacked sequentially from bottom to top. The high-resistivity structure layer 2 includes a Si-containing material layer 21 and an Al-containing material layer 22, with the Al-containing material layer 22 located between the high-resistivity GaN and the Si-containing material layer 21. The constituent elements of the Al-containing material layer 22 include Al and N. The high-resistivity GaN layer 3 is an undoped layer. The high-resistivity GaN layer 3 grown in this embodiment does not have additional Fe or C sources, contains no Fe element, and is intrinsic GaN.
[0020] The epitaxial layer structure of gallium nitride (GaN) power devices is a multilayer structure formed by sequentially depositing layers on a substrate 1 using epitaxial growth technology during the manufacturing process of gallium nitride (GaN) power devices to improve voltage withstand capability. Substrate 1 is located at the bottom of the epitaxial layer structure and serves as the foundational support for the entire structure. Substrate 1 can be, for example, a sapphire substrate, which offers good corrosion resistance and relatively low cost. The high-resistivity structure layer 2 is a superposition of a Si-containing material layer 21 and an Al-containing material layer 22. The Si material in the Si-containing material layer 21 can be, for example, a single Si layer or an Al-containing material layer with the first Al material layer 220 as the substrate. The Al-containing material layer can also be an AlN material layer. The Al material in the Al-containing material layer 22 can be, for example, AlN or AlGaN.
[0021] The high-resistivity GaN layer 3, a gallium nitride (GaN) layer, effectively confines the movement of charge carriers (such as electrons). In power devices, uncontrolled movement of charge carriers can lead to leakage current and other problems, affecting device performance. The channel layer 4 is the main channel for charge carrier (electron) transport, and its properties directly determine the device's current conduction capability. The channel layer 4 can be, for example, made of GaN. The barrier layer 5 can be, for example, made of AlGaN, with an Al composition of 20%–30%. The barrier layer 5 and the channel layer 4 form an AlGaN / GaN heterostructure. Due to the band shift between the AlGaN and GaN layers, a two-dimensional electron gas (2DEG) is formed at the interface. The 2DEG is a high-mobility carrier channel.
[0022] In the embodiments of this utility model, reference is made to Figure 2 As shown, the gallium nitride power device epitaxial layer structure also includes an isolation layer 6, which is located between the barrier layer 5 and the channel layer 4. The isolation layer 6 is used to increase the electron density of the two-dimensional electron gas, reduce the resistance, and increase the mobility. For example, in some embodiments, the isolation layer 6 is made of AlN. In embodiments of this invention, the gallium nitride power device epitaxial layer structure also includes a cap layer 7, which is located on the outermost layer of the gallium nitride power device epitaxial layer structure. The cap layer 7 is a thin layer located on the outermost layer of the device, covering other functional layers, mainly to protect the internal functional layers. The cap layer 7 can be, for example, made of GaN or SiNx.
[0023] Reference Figure 6 As shown, control group 1 has no Si-containing material layer 21 and no Al-containing material layer 22 in the epitaxial layer structure of the gallium nitride power device. Control group 2 has no Si-containing material layer 21 but has an Al-containing material layer 22 in the epitaxial layer structure of the gallium nitride power device. Control group 3 has a high-resistivity GaN layer 3 with C doping in the epitaxial layer structure of the gallium nitride power device. The experimental group has a Si-containing material layer 21 and an Al-containing material layer 22 in the epitaxial layer structure of the gallium nitride power device. The vertical axis represents the resistance (Ω) on a logarithmic scale; the horizontal axis represents different experimental conditions. According to the experimental data, the resistance of the GaN layer grown in control group 1 is 2.8 × 10⁻⁶. 3 The resistivity of the GaN layer grown in control group 2 was 8.7 × 10⁻⁶ Ω. 3 The resistivity of the GaN layer grown in control group 3 was 6.1 × 10⁻⁶ Ω. 12The resistance of the GaN layer grown in the experimental group was 1.0 × 10¹³ Ω. Without the Si-containing material layer 21 and the Al-containing material layer 22 (control group 1), the resistance was relatively low. With the addition of the Al-containing material layer 22 (control group 2), the resistance increased significantly. When both the Si-containing material layer 21 and the Al-containing material layer 22 were added simultaneously (experimental group), the resistance increased sharply, reaching 1.0 × 10¹³ Ω, slightly higher than the resistance of the high-resistance GaN layer 3 with C doping (control group 3). (Refer to...) Figure 7 As shown, the device specifications are Ig < 60 nA and Id < 200 nA. The Ig and Id leakage current levels of the gallium nitride (GaN) power devices fabricated in the epitaxial structure of the high-resistivity GaN layer 3 with C doping (control group 3) and the GaN power devices fabricated in the epitaxial structure of the GaN power device with a Si-containing material layer 21 and an Al-containing material layer 22 (experimental group) are comparable. The experimental group has no C doping to avoid the influence of C doping on the dynamic stability of the device. Finally, it is verified that a high-resistivity GaN layer 3 can be grown in the epitaxial structure of the gallium nitride power device by stacking a Si-containing material layer 21 and an Al-containing material layer 22.
[0024] In some embodiments of this utility model, reference is made to Figure 3 As shown, the Si-containing material layer 21 includes a first Si layer 210 and a second Si layer 211. The Al-containing material layer 22 includes a first Al material layer 220 and a second Al material layer 221. In the high-resistivity structure, the first Si layer 210, the first Al material layer 220, the second Si layer 211, and the second Al material layer 221 are sequentially disposed on the substrate 1.
[0025] Reference Figure 3 As shown, the epitaxial structure of the gallium nitride power device includes, from bottom to top, a substrate 1, a first Si layer 210, a first Al material layer 220, a second Si layer 211, a second Al material layer 221, a high-resistivity GaN layer 3, a channel layer 4, and a barrier layer 5. There may be no clear interface between the Si material layer 21 and the Al material layer 221; the Si signal can be measured by secondary-ion mass spectrometry (SIMS) elemental analysis. Figure 5 As shown, the horizontal axis represents depth (in nm), and the vertical axis represents concentration (in atoms / cm). 3 This shows the concentration (atoms / cm) of different elements (C-carbon, O-oxygen, Si-silicon, and Al-aluminum) at different depths (nm). 3 ) Changes.
[0026] As shown in the figure, the concentration of carbon (C) is relatively low and stable throughout the entire depth range, while the concentration of oxygen (O) fluctuates significantly at different depths. The concentration of silicon (Si) has a significant peak at a specific depth, and the concentration of aluminum (Al) shows obvious peaks and variations at different depths. Finally, SIMS analysis revealed that silicon (Si) was detected on the surface of substrate 1 and in the Al-containing material layer 22 throughout the entire gallium nitride power device epitaxial layer structure. Furthermore, the figure shows that the oxygen (O) content differs between the first Al material layer 220 and the second Al material layer 221, and the overall carbon (C) concentration is low, thus allowing for the detection of a distinct Al-containing material layer 22.
[0027] In some embodiments of this utility model, reference is made to Figure 4 As shown, in the high-resistivity structure, a Si-containing material layer 21 is disposed on the substrate 1, and an Al-containing material layer 22 is disposed on the Si-containing material layer 21. The epitaxial layer structure of the gallium nitride power device includes, from bottom to top, a substrate 1, a Si-containing material layer 21, an Al-containing material layer 22, a high-resistivity GaN layer 3, a channel layer 4, and a barrier layer 5. The high-resistivity structure can be configured with multiple sets of Al-containing material layers 22 and Si-containing material layers 21, or it can be configured with only one set of Al-containing material layers 22 and Si-containing material layers 21. In the epitaxial layer structure of the gallium nitride power device, only a stack of Al-containing material layers 22 and Si-containing material layers 21 is needed, and their combination can significantly improve the resistance of the original high-resistivity GaN layer 3.
[0028] In some embodiments of the present invention, reference is made to Figure 3 As shown, the first Si layer 210 is a Si-containing Al material layer or a Si monolayer with the first Al material layer 220 on the substrate 1 as the substrate. The second Si layer 211 is a Si-containing Al material layer or a Si monolayer with the first Al material layer 220 as the substrate. Si is usually used as a donor impurity in semiconductor materials, providing additional electrons to the crystal structure. Under a high electric field environment, the electrons provided by Si are easily driven by the electric field, forming unwanted leakage current, resulting in leakage and thus reducing the performance of the device. Secondly, during the subsequent epitaxial layer growth process, Si atoms have a certain diffusion tendency. In this embodiment, by setting the second Al material layer 221 on the side of the second Si layer 211 away from the substrate 1 and combining it with a high-resistivity GaN layer 3, it is possible to prevent Si atoms from moving from their original position to other functional layers (such as the channel layer 4). This prevents the diffusion of Si atoms from damaging the original electrical structure of the device and causing leakage problems.
[0029] Reference Figure 5 As shown, its basis Figure 5Fe was not detected in the SIMS concentration analysis, and the C content was found to be at a low level. Specifically, the C content in the high-resistivity GaN layer 3 was less than 1 × 10⁻⁶. 17 cm -3 As an undoped layer, the absence of additional impurity doping (such as Fe and C sources) avoids side effects such as increased leakage channels caused by excessive carrier introduction. Furthermore, experimental results show that the high-resistivity GaN layer 3 grown undoped is comparable in resistance to high-resistivity GaN layers 3 obtained with additional Fe and C sources. In this embodiment, the high-resistivity GaN layer 3 avoids the memory effect caused by additional Fe sources, which reduces carrier mobility, and also avoids excessively high C content (e.g., C content greater than 1 × 10⁻⁶ in self-doped or additionally doped C sources). 18 cm -3 This is to prevent excessive C source from polluting the reactor environment or causing unstable dynamic performance of the device due to C doping stability factors.
[0030] In some embodiments of this utility model, the Si-containing material layer 21 is a single layer or an Al-containing material layer with the first Al material layer 220 as the substrate. (Refer to...) Figure 4 As shown, the Si-containing material layer 21 is located between the substrate 1 and the Al-containing material layer 22. Its main purpose is to reduce the defects of the Al-containing material layer 22 and increase the crystal quality of the Al-containing material layer 22.
[0031] In some embodiments of this invention, the Al-containing material layer 22 is an aluminum nitride (AlN) layer or an aluminum gallium nitride (AlGaN) layer. The AlN and AlGaN layers serve as the bonding layers between the high-resistivity GaN layer 3 and the substrate 1. The Si-containing material layer 21 improves the crystal quality of the Al-containing material layer 22 bonding layer, further reducing defects in the high-resistivity GaN layer 3 and achieving even higher resistance. In the AlGaN / GaN heterostructure, due to the band shift between the AlGaN and GaN layers, a two-dimensional electron gas (2DEG) is formed at the interface. However, not all current flows through the channel layer 4, causing current leakage. This problem can be solved by increasing the resistance of the high-resistivity GaN layer 3. Experimental results show that the high-resistivity structure significantly increases the resistance of the high-resistivity GaN layer 3, effectively reducing current leakage and thus optimizing the electrical performance of the device.
[0032] In addition, this embodiment provides a method for fabricating an epitaxial layer structure for a gallium nitride power device, comprising:
[0033] S1: A high-resistivity structural layer is grown on the substrate;
[0034] S2: A high-resistivity GaN layer is grown on the high-resistivity structural layer;
[0035] S3: Growing a channel layer on the high-resistivity GaN layer;
[0036] S4: A barrier layer is grown on the channel layer to obtain the epitaxial layer structure of the gallium nitride power device;
[0037] The high-resistivity structure layer in the epitaxial layer structure of the gallium nitride power device includes a Si-containing material layer and an Al-containing material layer, wherein the Al-containing material layer is located between the high-resistivity GaN and the Si-containing material layer, and the constituent elements of the Al-containing material layer include Al and N.
[0038] Specifically, for example, in step S1, a flat Al2O3 (sapphire) substrate can be used. In step S2, a high-resistivity GaN layer is grown on the Al-containing material layer of the high-resistivity structure layer at a temperature between 1000 and 1150°C, with a thickness ranging from 1 to 4 μm. The high-resistivity GaN layer in step S2 can be obtained through conditions such as the epitaxial GaN V / III ratio temperature field, and the high-resistivity GaN layer can be an undoped high-resistivity GaN layer. Next, in step S3, for example, a 100 nm to 300 nm GaN layer can be grown on the high-resistivity GaN layer as a channel layer. In step S4, for example, a 15 nm to 30 nm thick AlGaN layer can be grown on the channel layer as a barrier layer, with an Al composition of 20% to 30% in the barrier layer. In addition, an AlN layer of 1 nm to 2 nm thickness can be grown on the channel layer as an isolation layer, and a GaN or SiNx layer of 1 nm to 4 nm thickness can be grown on the barrier layer as a cap layer on the surface of the epitaxial layer.
[0039] In some embodiments of the present invention, the Si-containing material layer includes a first Si layer and a second Si layer. The Al-containing material layer includes a first Al material layer and a second Al material layer. Step S1 specifically includes:
[0040] S11: Si is introduced for the first time and a first Al material layer is prepared on the substrate to obtain a first Si layer and a first Al material layer sequentially disposed on the substrate.
[0041] S12: Si is introduced for the second time, and a second Al material layer is prepared on the first Al material layer to obtain a second Si layer and a second Al material layer sequentially disposed on the first Al material layer.
[0042] Specifically, in step S11, Si gas is introduced into the substrate to form a Si atmosphere and obtain a first Si layer. Then, a first Al material layer with a thickness of 20-40 nm is deposited on the first Si layer. In step S12, Si gas is introduced again to form a second Si layer on the first Al material layer, and then a second Al material layer with a thickness of 40 nm is grown.
[0043] In some embodiments of the present invention, step S1 specifically involves introducing Si and preparing an Al-containing material layer on a substrate to obtain a Si-containing material layer and an Al-containing material layer sequentially disposed on the substrate.
[0044] Specifically, Si gas is introduced into the substrate to form a Si-containing material layer, and then a 40nm Al-containing material layer is grown.
[0045] The method for fabricating the epitaxial layer structure of gallium nitride power devices provided in this embodiment relies on the combination of Si-containing material layers and Al-containing material layers to grow low-defect, high-quality Al material, thereby significantly improving the resistance of the high-resistance GaN layer. Furthermore, it eliminates the need for additional Fe and C sources during the fabrication process, avoiding the reduction in carrier mobility caused by additional doping and preventing the complication of electrical performance.
[0046] Furthermore, it is understood that the foregoing embodiments are merely illustrative examples of this utility model. Provided that the technical features do not conflict, the structure is not contradictory, and the purpose of this utility model is not violated, the technical solutions of the various embodiments can be arbitrarily combined and used.
[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and not to limit it. Although this utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this utility model.
Claims
1. A gallium nitride power device epitaxial layer structure, characterized by, The gallium nitride power device epitaxial layer structure comprises, from bottom to top, a substrate, a high-resistance structure layer, a high-resistance GaN layer, a channel layer and a barrier layer; the high-resistance structure layer comprises a Si-containing material layer and an Al-containing material layer, and the Al-containing material layer is located between the high-resistance GaN and the Si-containing material layer; the Al-containing material layer is an aluminum nitride layer or an aluminum gallium nitride layer; and the high-resistance GaN layer is an undoped layer.
2. The gallium nitride power device epitaxial layer structure of claim 1, wherein, The Si-containing material layer comprises a first Si layer and a second Si layer; the Al-containing material layer comprises a first Al material layer and a second Al material layer; and the first Si layer, the first Al material layer, the second Si layer and the second Al material layer in the high-resistance structure are sequentially arranged on the substrate.
3. The gallium nitride power device epitaxial layer structure of claim 1, wherein, In the high-resistance structure, the Si-containing material layer is arranged on the substrate, and the Al-containing material layer is arranged on the Si-containing material layer.
4. The gallium nitride power device epitaxial layer structure of claim 1, wherein, There is no Fe element in the high-resistance GaN layer.
5. The gallium nitride power device epitaxial layer structure of claim 1, wherein, The gallium nitride power device epitaxial layer structure further comprises an isolation layer located between the barrier layer and the channel layer.
6. The gallium nitride power device epitaxial layer structure of claim 1, wherein, The gallium nitride power device epitaxial layer structure further comprises a cap layer located at the outermost layer of the gallium nitride power device epitaxial layer structure.