Vertical GaN-based epitaxial structure, manufacturing method thereof and gallium nitride HEMT device
By using a combined structure of a tungsten disulfide buffer layer and a gallium nitride epitaxial layer on a sapphire substrate, the vertical leakage and heat dissipation problems of the vertical GaN-based epitaxial structure are solved, and a high-mobility, low-square-resistance epitaxial structure is achieved, which is suitable for high-current-density power devices.
Patent Information
- Application Number
- CN202510868725.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-26
- Publication Date
- 2025-09-19
AI Technical Summary
In the prior art, vertical GaN-based epitaxial structures fabricated using sapphire substrates have vertical leakage and heat dissipation problems.
Tungsten disulfide is used as a buffer layer, combined with the structural design of gallium nitride buffer layer, GaN high-resistance layer and gallium nitride epitaxial layer. By controlling the thickness and doping concentration of each layer, a high-mobility, low-square-resistance epitaxial structure is formed, and the tungsten disulfide buffer layer is used as a heat dissipation layer.
It can effectively control the thickness uniformity of the epitaxial layer, reduce vertical leakage, solve the heat dissipation problem after chip packaging, and is suitable for the production of power devices with high current density.
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Figure CN120676687A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of semiconductors, and in particular to a vertical GaN-based epitaxial structure and a manufacturing method thereof. Background Art
[0002] GaN HEMTs (High Electron Mobility Transistors), with their high electron concentration and high electron mobility, have enormous potential for application in power electronics. This is because the AlGaN / GaN heterojunction interface in the GaN HEMT structure can form a large amount of polarized positive charge, resulting in the presence of a very high surface density two-dimensional electron gas (2DEG) in the heterojunction potential well. Its surface electron concentration is typically on the order of 1013 cm-2, and its mobility can typically reach around 2000 cm2 / V*s. This increases the frequency of high-power switching devices and significantly reduces power consumption, significantly reducing the size of power modules (such as power supply modules) while also significantly improving efficiency.
[0003] Currently, GaN HEMT structures for power devices are primarily grown on Si substrates, while those for RF devices are primarily based on SiC substrates. High-power devices are grown on Si substrates primarily because they are less sensitive to defect density and are significantly cheaper than SiC. However, for RF devices with higher defect density requirements, SiC substrates with the same lattice structure and similar lattice constant as GaN are required, which are more expensive. Sapphire substrates offer excellent insulating properties, allowing for the production of epitaxial layers with lower defect density.
[0004] However, vertical GaN-based epitaxial structures made using sapphire substrates still often have vertical leakage and heat dissipation problems.
[0005] Therefore, there is an urgent need for a vertical GaN-based epitaxial structure and a manufacturing method thereof that can solve the above problems. Summary of the Invention
[0006] The purpose of the present invention is to provide a vertical GaN-based epitaxial structure and its manufacturing method, which can effectively control the thickness uniformity of the gallium nitride epitaxial layer, effectively reduce vertical leakage, and solve the heat dissipation problem after the chip is packaged.
[0007] To achieve the above objectives, the present invention provides a vertical GaN-based epitaxial structure, comprising a growth substrate, a tungsten disulfide buffer layer formed on the growth substrate, a gallium nitride buffer layer formed on the tungsten disulfide buffer layer, a GaN high-resistance layer formed on the gallium nitride buffer layer, and a gallium nitride epitaxial layer formed on the GaN high-resistance layer.
[0008] Preferably, the thickness of the tungsten disulfide buffer layer is 50-200 μm, the thickness of the gallium nitride buffer layer is 1-1.5 μm, and the C doping concentration in the GaN high resistance layer is 5E18-2E19 cm -3 , thickness 800-1200nm.
[0009] Preferably, the gallium nitride epitaxial layer includes a GaN channel layer, an Al x Ga 1-x N barrier layer and cap layer.
[0010] Specifically, the Al x Ga 1-x The thickness of the N barrier layer is 15-30 nm, the range of x is 15% to 25%, the thickness of the GaN channel layer is 200-300 nm, and the thickness of the cap layer is 50-100 nm.
[0011] The present invention also provides a method for manufacturing a vertical GaN-based epitaxial structure, comprising: providing a growth substrate; growing a tungsten disulfide buffer layer on the growth substrate; growing a gallium nitride buffer layer on the tungsten disulfide buffer layer; growing a GaN high-resistance layer on the gallium nitride buffer layer; and growing a gallium nitride epitaxial layer on the GaN high-resistance layer.
[0012] Preferably, the thickness of the tungsten disulfide buffer layer is 50-200 μm, the thickness of the gallium nitride buffer layer is 1-1.5 μm, and the C doping concentration in the GaN high resistance layer is 5E18-2E19 cm -3 , thickness 800-1200nm.
[0013] Preferably, when growing the tungsten disulfide buffer layer on the growth substrate, it is grown by CVD, the growth temperature is 900-1000°C, the growth pressure is 600-1000mbar, the ratio of the sulfur source to the tungsten trioxide source in the raw material is 1:2, the growth time is 15-25min, and the Ar flow rate during growth is 50-100 cm3 / min; when growing the gallium nitride buffer layer on the tungsten disulfide buffer layer, it is grown by MOCVD, the growth pressure is 100-300mbar, the growth temperature is 1030-1080°C, and the growth rate of the gallium nitride buffer layer is 2-4um / h; when growing the GaN high-resistance layer on the gallium nitride buffer layer, the growth pressure is 50-200mbar, the growth temperature is 800-1000°C, and the growth rate is 4-5um / h.
[0014] Preferably, growing a gallium nitride epitaxial layer on the GaN high resistance layer specifically includes: sequentially growing a GaN channel layer, an Al x Ga 1-x N barrier layer and cap layer.
[0015] Specifically, the Al x Ga 1-x The thickness of the N barrier layer is 15-30 nm, the range of X is 15% to 25%, the thickness of the GaN channel layer is 200-300 nm, and the thickness of the cap layer is 50-100 nm.
[0016] Specifically, when the GaN channel layer is grown on the GaN high resistance layer, the growth pressure is 100-300 mbar, the growth temperature is 1060-1120° C., and the growth rate is 2-3 μm / h; when the Al is grown on the GaN channel layer, the growth pressure is 100-300 mbar, the growth temperature is 1060-1120° C., and the growth rate is 2-3 μm / h. x Ga 1-x When the N barrier layer is formed, the growth pressure is 50-100 mbar, the growth temperature is 1050-1100 ° C, and the growth rate is 0.5-1 μm / h; x Ga 1-x When the cap layer is grown on the N barrier layer, the growth pressure is 100-200 mbar, the growth temperature is 1000-1035°C, the SiH4 flow rate is 1000-1500 sccm, the SiH4 concentration is 1000 ppm, the NH3 flow rate is 2000-3000 sccm, and the growth rate is 0.1-0.3 um / h.
[0017] Preferably, the method for manufacturing a vertical GaN-based epitaxial structure further comprises removing the growth substrate and using the tungsten disulfide buffer layer as a tungsten disulfide heat dissipation layer.
[0018] The present invention also provides a gallium nitride HEMT device, comprising a vertical GaN-based epitaxial structure and pins formed on the vertical GaN-based epitaxial structure, wherein the vertical GaN-based epitaxial structure is manufactured by the method for manufacturing a vertical GaN-based epitaxial structure as claimed in claim 1.
[0019] The present invention also provides a gallium nitride HEMT device, comprising a vertical GaN-based epitaxial structure, and a source, a drain, and a gate formed on the vertical GaN-based epitaxial structure. The vertical GaN-based epitaxial structure comprises a tungsten disulfide heat dissipation layer, a gallium nitride buffer layer formed on the gallium nitride heat dissipation layer, a GaN high-resistance layer formed on the gallium nitride buffer layer, and a gallium nitride epitaxial layer formed on the GaN high-resistance layer. The source, the drain, and the gate are formed on a side of the gallium nitride epitaxial layer away from the tungsten disulfide heat dissipation layer.
[0020] Preferably, the thickness of the disulfide heat dissipation layer is 50-200 μm, the thickness of the gallium nitride buffer layer is 1-1.5 μm, and the C doping concentration in the GaN high resistance layer is 5E18-2E19 cm -3 , thickness 800-1200nm.
[0021] Preferably, the gallium nitride epitaxial layer includes a GaN channel layer, an Al2O3 layer, and a GaN high resistance layer formed on a side of the GaN high resistance layer away from the gallium nitride buffer layer. x Ga 1-x N barrier layer and cap layer, the source and gate connect the Al x Ga 1-x An N barrier layer, the drain is connected to the cap layer.
[0022] Preferably, the Al x Ga 1-x The thickness of the N barrier layer is 15-30 nm, the range of X is 15% to 25%, the thickness of the GaN channel layer is 200-300 nm, and the thickness of the cap layer is 50-100 nm.
[0023] Compared to existing technologies, this invention uses tungsten disulfide as a buffer layer between the growth substrate and the GaN buffer layer beneath the GaN epitaxial layer. The layered crystal structure of the tungsten disulfide buffer layer exhibits strong in-plane covalent bonds, which can reduce stress through out-of-plane interactions and modify the substrate's warpage, particularly when growing the AlGaN barrier layer within the GaN epitaxial layer. This results in superior thickness and composition uniformity, as well as device consistency. It also addresses the issue of heat dissipation after chip packaging. This method can produce epitaxial structures with high mobility and low square resistance, making them suitable for the fabrication of high-current-density power devices. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] Figure 1 It is a structural diagram of the vertical GaN-based epitaxial structure of the present invention.
[0025] Figures 2 to 3 It is a flow chart of the method for manufacturing a vertical GaN-based epitaxial structure of the present invention.
[0026] Figure 4 1 is a structural diagram of the gallium nitride HEMT device of the present invention. DETAILED DESCRIPTION
[0027] In order to explain the technical content, structural features, achieved objectives and effects of the present invention in detail, the following is a detailed description in conjunction with the embodiments and the accompanying drawings.
[0028] refer to Figure 1 The present invention discloses a vertical GaN-based epitaxial structure 100, comprising a growth substrate 10, a tungsten disulfide buffer layer 20 formed on the growth substrate 10, a gallium nitride buffer layer 30 formed on the tungsten disulfide buffer layer 20, a GaN high-resistance layer 40 formed on the gallium nitride buffer layer 30, and a gallium nitride epitaxial layer 50 formed on the GaN high-resistance layer 40. The growth substrate 10 is a sapphire substrate.
[0029] The thickness of the tungsten disulfide buffer layer 20 is 50-200 μm, the thickness of the gallium nitride buffer layer 30 is 1-1.5 μm, and the C doping concentration in the GaN high resistance layer 40 is 5E18-2E19 cm -3 , thickness 800-1200nm.
[0030] refer to Figure 1 The gallium nitride epitaxial layer 50 includes a GaN channel layer 51, an Al x Ga 1-x N barrier layer 52 and cap layer 53 .
[0031] Specifically, the Al x Ga 1-x The thickness of the N barrier layer 52 is 15-30 nm, and the range of x is 15% to 25%. The thickness of the GaN channel layer 51 is 200-300 nm, and the thickness of the cap layer 53 is 50-100 nm. The cap layer 53 is a SiN cap layer, but it can also be a GaN cap layer.
[0032] refer to Figure 2 and Figure 3 The present invention also provides a method for manufacturing a vertical GaN-based epitaxial structure 100, including steps S1 to S5.
[0033] refer to Figure 2 In step S1, a growth substrate 10 is provided. The growth substrate 10 is a sapphire substrate. The thickness of the growth substrate 10 is 550-1000 μm and the diameter is 100 or 150 mm.
[0034] Step S2 , growing a tungsten disulfide buffer layer 20 on the growth substrate 10 .
[0035] The thickness of the tungsten disulfide buffer layer 20 is 50-200 μm.
[0036] When the tungsten disulfide buffer layer 20 is grown on the growth substrate 10 by the CVD process, the growth temperature T1 is 900-1000° C., the growth pressure is 600-1000 mbar, the ratio of the sulfur source to the tungsten trioxide source in the raw materials is 1:2, the growth time is 15-25 minutes, and the Ar flow rate during growth is 50-100 cm3 / min.
[0037] refer to Figure 2 In step S3, a gallium nitride buffer layer 30 is grown on the tungsten disulfide buffer layer 20. The gallium nitride buffer layer 30 has a thickness of 1-1.5 μm.
[0038] The gallium nitride buffer layer 30 is grown on the tungsten disulfide buffer layer 20 by MOCVD, with a growth pressure of 100-300 mbar and a growth temperature of 1030-1080° C. The growth rate of the gallium nitride buffer layer 30 is 2-4 um / h.
[0039] refer to Figure 2 , step S4, growing a GaN high resistance layer 40 on the gallium nitride buffer layer 30 .
[0040] The C doping concentration in the GaN high resistance layer 40 is 5E18-2E19 cm -3 , thickness 800-1200nm.
[0041] When growing the GaN high-resistance layer 40 on the gallium nitride buffer layer 30, the growth pressure is 50-200 mbar, the growth temperature is 800-1000°C, and the growth rate is 4-5 μm / h. Specifically, the GaN high-resistance layer 40 is a C-GaN high-resistance layer, and the external dopant source used in growing the C-GaN high-resistance layer 40 is ethylene or hexene.
[0042] In this embodiment, when growing the C-doped GaN high-resistance layer 40 (C-GaN high-resistance layer), ammonia and trimethylgallium are used as nitrogen sources and gallium sources, respectively, and hexene is used as a doping source. During growth, the growth temperature is slowly increased to 1000 degrees Celsius, and the growth pressure is slowly changed to 75 mbar. When the temperature and pressure change, ammonia, trimethylgallium, and hexene are introduced. The C doping concentration can be obtained through SIMS testing.
[0043] refer to Figure 3 , step S5, growing a gallium nitride epitaxial layer 50 on the GaN high resistance layer 40.
[0044] Specifically, growing the gallium nitride epitaxial layer 50 on the GaN high resistance layer 40 includes: sequentially growing a GaN channel layer 51, an Al x Ga 1-x N barrier layer 52 and cap layer 53 .
[0045] Specifically, the Al x Ga 1-x The thickness of the N barrier layer 52 is 15-30 nm, the range of x is 15%-25%, and the thickness of the cap layer 53 is 50-100 nm.
[0046] When growing the GaN channel layer 51 on the GaN high-resistance layer 40, ammonia and trimethylgallium are used as nitrogen and gallium sources, respectively, at a growth pressure of 100-300 mbar, a growth temperature of 1060-1120°C, and a growth rate of 2-3 μm / h. The thickness of the GaN channel layer 52 is 200-300 nm.
[0047] The Al is grown on the GaN channel layer 51. x Ga 1-x When forming the N barrier layer 52, ammonia, trimethyl gallium, and trimethyl aluminum are used as nitrogen source, gallium source, and aluminum source, respectively. The growth pressure is 50-100 mbar, the temperature is raised to 1050-1100°C, and the growth rate is 0.5-1 μm / h. x Ga 1-x The thickness of the N barrier layer 52 can be measured by XRR method. x Ga 1-x The composition of the N barrier layer 52 can be obtained by XRD.
[0048] In the Al x Ga 1-xWhen growing the cap layer 53 on the N barrier layer 52, the growth pressure is 100-200 mbar, the growth temperature is 1000-1035°C, the SiH4 flow rate is 1000-1500 sccm, the SiH4 concentration is 1000 ppm, the NH3 flow rate is 2000-3000 sccm, and the growth rate is 0.1-0.3 μm / h. The thickness of the cap layer 53 can be measured using XRR. The cap layer 53 is a SiN cap layer. Of course, the cap layer 53 can also be a GaN cap layer.
[0049] refer to Figure 3 The method for manufacturing the vertical GaN-based epitaxial structure 100 further includes step S6 of removing the growth substrate 10 and using the tungsten disulfide buffer layer 20 as a tungsten disulfide heat dissipation layer.
[0050] refer to Figure 4 The present invention also discloses a gallium nitride HEMT device, comprising a vertical GaN-based epitaxial structure 100 and an electrode 60 formed on the vertical GaN-based epitaxial structure 100. The vertical GaN-based epitaxial structure 100 is manufactured by the method for manufacturing the vertical GaN-based epitaxial structure 100 according to the above-mentioned claim.
[0051] The gallium nitride HEMT device includes a vertical GaN-based epitaxial structure 100 and an electrode 60 formed on the vertical GaN-based epitaxial structure 100. The electrode 60 includes a source S, a gate G, and a drain D. The vertical GaN-based epitaxial structure 100 includes a tungsten disulfide heat dissipation layer 20a, a gallium nitride buffer layer 30 formed on the gallium nitride heat dissipation layer 20a, a GaN high-resistance layer 40 formed on the gallium nitride buffer layer 30, and a gallium nitride epitaxial layer 50 formed on the GaN high-resistance layer 40. The electrode 60 is formed on a side of the gallium nitride epitaxial layer 50 away from the tungsten disulfide heat dissipation layer 20a.
[0052] The thickness of the disulfide heat dissipation layer is 50-200 μm, the thickness of the gallium nitride buffer layer 30 is 1-1.5 μm, and the C doping concentration in the GaN high resistance layer 40 is 5E18-2E19 cm -3 , thickness 800-1200nm.
[0053] refer to Figure 4 The GaN epitaxial layer 50 includes a GaN channel layer 51, an Al x Ga 1-x N barrier layer 52 and cap layer 53. The source S and drain G are connected to the Al x Ga 1-xN barrier layer 52 , the drain electrode G is connected to the cap layer 53 .
[0054] Wherein, the Al x Ga 1-x The thickness of the N barrier layer 52 is 15-30 nm, and the range of X is 15% to 25%. The thickness of the GaN channel layer 51 is 200-300 nm, and the thickness of the cap layer 53 is 50-100 nm. The cap layer 53 is a SiN cap layer. Of course, the cap layer 53 can also be a GaN cap layer.
[0055] The present invention uses tungsten disulfide as a buffer layer between the growth substrate 10 and the gallium nitride buffer layer 30. The layered crystal structure of the tungsten disulfide buffer layer 20 has good in-plane covalent bonds, which can reduce stress through out-of-plane interactions, change the warpage of the growth substrate 10, and especially change the Al content in the growing gallium nitride epitaxial layer 50. x Ga 1-x The warpage of the N barrier layer 52 is reduced, achieving superior thickness and composition uniformity and device consistency; it also solves the problem of heat dissipation after chip packaging. This method can also produce epitaxial structures with high mobility and low square resistance, which are suitable for the production of high-current density power devices.
[0056] The above disclosure is merely a preferred embodiment of the present invention, which certainly cannot be used to limit the scope of the present invention. Therefore, equivalent changes made within the scope of the present invention are still within the scope of the present invention.
Claims
1. A vertical GaN-based epitaxial structure, characterized by: The invention comprises a growth substrate, a tungsten disulfide buffer layer formed on the growth substrate, a gallium nitride buffer layer formed on the tungsten disulfide buffer layer, a GaN high-resistance layer formed on the gallium nitride buffer layer, and a gallium nitride epitaxial layer formed on the GaN high-resistance layer.
2. The vertical GaN-based epitaxial structure according to claim 1, wherein: The thickness of the tungsten disulfide buffer layer is 50-200 μm, the thickness of the gallium nitride buffer layer is 1-1.5 μm, and the C doping concentration in the GaN high resistance layer is 5E18-2E19 cm -3 , thickness 800-1200nm.
3. The vertical GaN-based epitaxial structure according to claim 1, wherein: The gallium nitride epitaxial layer includes a GaN channel layer, an Al x Ga 1-x N barrier layer and cap layer.
4. The vertical GaN-based epitaxial structure according to claim 3, wherein: The Al x Ga 1-x The thickness of the N barrier layer is 15-30 nm, the range of x is 15% to 25%, the thickness of the GaN channel layer is 200-300 nm, and the thickness of the cap layer is 50-100 nm.
5. A method for fabricating a vertical GaN-based epitaxial structure, characterized by: include: providing a growth substrate; growing a tungsten disulfide buffer layer on the growth substrate; growing a gallium nitride buffer layer on the tungsten disulfide buffer layer; Growing a GaN high-resistance layer on the gallium nitride buffer layer; A gallium nitride epitaxial layer is grown on the GaN high-resistance layer.
6. The method for manufacturing a vertical GaN-based epitaxial structure according to claim 5, wherein: The thickness of the tungsten disulfide buffer layer is 50-200 μm, the thickness of the gallium nitride buffer layer is 1-1.5 μm, and the C doping concentration in the GaN high resistance layer is 5E18-2E19 cm -3 , thickness 800-1200nm.
7. The method for fabricating a vertical GaN-based epitaxial structure according to claim 5, wherein: When growing a tungsten disulfide buffer layer on the growth substrate by a CVD process, the growth temperature is 900-1000° C., the growth pressure is 600-1000 mbar, the ratio of the sulfur source to the tungsten trioxide source in the raw materials is 1:2, the growth time is 15-25 minutes, and the Ar flow rate during growth is 50-100 cm3 / min; When growing the gallium nitride buffer layer on the tungsten disulfide buffer layer, MOCVD is used for growth, with a growth pressure of 100-300 mbar, a growth temperature of 1030-1080° C., and a growth rate of 2-4 μm / h for the gallium nitride buffer layer; When the GaN high-resistance layer is grown on the gallium nitride buffer layer, the growth pressure is 50-200 mbar, the growth temperature is 800-1000° C., and the growth rate is 4-5 um / h.
8. The method for manufacturing a vertical GaN-based epitaxial structure according to claim 5, wherein: Growing a gallium nitride epitaxial layer on the GaN high resistance layer specifically includes: sequentially growing a GaN channel layer, an Al x Ga 1-x N barrier layer, cap layer; the Al x Ga 1-x The thickness of the N barrier layer is 15-30 nm, the range of X is 15% to 25%, the thickness of the GaN channel layer is 200-300 nm, and the thickness of the cap layer is 50-100 nm.
9. The method for manufacturing a vertical GaN-based epitaxial structure according to claim 8, wherein: When growing the GaN channel layer on the GaN high-resistance layer, the growth pressure is 100-300 mbar, the growth temperature is 1060-1120° C., and the growth rate is 2-3 μm / h; The Al is grown on the GaN channel layer. x Ga 1-x For the N barrier layer, the growth pressure is 50-100 mbar, the growth temperature is 1050-1100°C, and the growth rate is 0.5-1 μm / h; In the Al x Ga 1-x When the cap layer is grown on the N barrier layer, the growth pressure is 100-200 mbar, the growth temperature is 1000-1035°C, the SiH4 flow rate is 1000-1500 sccm, the SiH4 concentration is 1000 ppm, the NH3 flow rate is 2000-3000 sccm, and the growth rate is 0.1-0.3 um / h.
10. The method for fabricating a vertical GaN-based epitaxial structure according to claim 5, wherein: The method further includes removing the growth substrate and using the tungsten disulfide buffer layer as a tungsten disulfide heat dissipation layer.
11. A gallium nitride HEMT device, characterized in that: It comprises a vertical GaN-based epitaxial structure and pins formed on the vertical GaN-based epitaxial structure, wherein the vertical GaN-based epitaxial structure is manufactured by the method for manufacturing a vertical GaN-based epitaxial structure according to any one of claims 5-10.
12. A gallium nitride HEMT device, characterized in that: It includes a vertical GaN-based epitaxial structure, and a source, a drain and a gate formed on the vertical GaN-based epitaxial structure. The vertical GaN-based epitaxial structure includes a tungsten disulfide heat dissipation layer, a gallium nitride buffer layer formed on the disulfide heat dissipation layer, a GaN high-resistance layer formed on the gallium nitride buffer layer, and a gallium nitride epitaxial layer formed on the GaN high-resistance layer. The source, the drain and the gate are formed on a side of the gallium nitride epitaxial layer away from the tungsten disulfide heat dissipation layer.
13. The gallium nitride HEMT device according to claim 12, wherein: The thickness of the disulfide heat dissipation layer is 50-200 μm, the thickness of the gallium nitride buffer layer is 1-1.5 μm, and the C doping concentration in the GaN high resistance layer is 5E18-2E19 cm -3 , thickness 800-1200nm.
14. The gallium nitride HEMT device according to claim 12, wherein: The gallium nitride epitaxial layer includes a GaN channel layer, an Al x Ga 1-x N barrier layer and cap layer, the source and gate connect the Al x Ga 1-x N barrier layer, the drain is connected to the cap layer; the Al x Ga 1-x The thickness of the N barrier layer is 15-30 nm, the range of X is 15% to 25%, the thickness of the GaN channel layer is 200-300 nm, and the thickness of the cap layer is 50-100 nm.