Overhanging gan-based led device for microfluidic substance detection and method of making same

Abstract

This invention relates to a suspended GaN-based LED device for microfluidic material detection and its fabrication method. The suspended GaN-based LED device for microfluidic material detection includes: a first GaN-based LED structure comprising a first substrate, a first buffer layer, a first GaN-based device layer, and a first cavity, the first cavity penetrating the first substrate, the first buffer layer, and a portion of the first GaN-based device layer; and a second GaN-based LED structure comprising a second substrate, a second buffer layer, a second GaN-based device layer, and a second cavity, the second cavity penetrating the second substrate, the second buffer layer, and a portion of the second GaN-based device layer; the first GaN-based LED structure is located above the second GaN-based LED structure, and the first substrate is connected to the second substrate, and the first cavity is connected to the second cavity. This invention expands the application fields of visible light communication technology and microfluidic material detection technology.

Description

Technical Field

[0001] This invention relates to the fields of information materials and visible light communication technology, and in particular to a suspended GaN-based LED device for microfluidic material detection and its fabrication method. Background Technology

[0002] As a representative of third-generation semiconductors, GaN possesses excellent optoelectronic and mechanical properties. Its bandgap is 3.4 eV. By forming ternary or quaternary solid solution alloy systems with InN (0.63 eV bandgap) and AlN (6.2 eV bandgap), it creates a multi-quantum-well structure, achieving a continuously tunable bandgap between 0.63 eV and 6.2 eV. Through electron-hole recombination, it directly converts electrical energy into light energy, exhibiting high electro-optical conversion efficiency. Furthermore, GaN light-emitting diodes (LEDs) also possess the ability to detect light; by irradiating them with high-energy photons, electron-hole pairs are generated, converting light energy into electrical energy. Based on integrated light-emitting and detection devices, these technologies are widely used in communication, lighting, and sensing fields.

[0003] With the continuous development of microfluidics technology, it has been widely applied in many fields, such as biomedical engineering, environmental monitoring, and chemical analysis. In the biomedical field, microfluidics has become an important tool for cell manipulation, drug screening, and disease diagnosis. For example, using microfluidic chips to separate and diagnose blood cells enables rapid, accurate, and non-invasive blood testing. Furthermore, microfluidics technology is also applied in environmental monitoring, enabling rapid analysis and detection of pollutants in air, water, and soil. Simultaneously, microfluidics technology can also be applied in chemical analysis, achieving efficient sample separation and detection, improving the accuracy and sensitivity of analysis.

[0004] With the gradual development of 6G IoT, there is an urgent need for more diverse and highly integrated sensors to address more complex application scenarios. However, current visible light technology cannot be applied to the field of logistics control and detection, which limits both the development of visible light communication technology and the expansion of the application areas of microfluidic detection technology.

[0005] Therefore, how to expand the application areas of visible light communication technology and the functions of visible light communication devices is a technical problem that urgently needs to be solved. Summary of the Invention

[0006] This invention provides a suspended GaN-based LED device for microfluidic material detection and its fabrication method, thereby expanding the application areas of visible light communication technology.

[0007] To address the above problems, this invention provides a suspended GaN-based LED device for microfluidic material detection, comprising:

[0008] The first GaN-based LED structure includes a first substrate, a first buffer layer on the first substrate, a first GaN-based device layer on the first buffer layer, and a first cavity, wherein the first cavity penetrates the first substrate, the first buffer layer, and a portion of the first GaN-based device layer.

[0009] The second GaN-based LED structure includes a second substrate, a second buffer layer on the second substrate, a second GaN-based device layer on the second buffer layer, and a second cavity, wherein the second cavity penetrates the second substrate, the second buffer layer, and a portion of the second GaN-based device layer.

[0010] The first GaN-based LED structure is located above the second GaN-based LED structure, and the first substrate is connected to the second substrate, and the first cavity is connected to the second cavity.

[0011] In some embodiments, the first GaN-based device layer includes a first n-type GaN layer, a first InGaN layer on the first n-type GaN layer, a first InGaN / GaN quantum well active layer on the first InGaN layer, and a first p-type GaN layer on the first InGaN / GaN quantum well active layer. The first n-type GaN layer includes a first lower step and a first upper step on the first lower step. The first InGaN layer is located on the first upper step, and the first cavity penetrates the first lower step.

[0012] The second GaN-based device layer includes a second n-type GaN layer, a second InGaN layer on the second n-type GaN layer, a second InGaN / GaN quantum well active layer on the second InGaN layer, and a second p-type GaN layer on the second InGaN / GaN quantum well active layer. The second n-type GaN layer includes a second lower step and a second upper step on the second lower step. The second InGaN layer is located on the second upper step, and the second cavity penetrates the second lower step.

[0013] In some embodiments, the first cavity includes a first branch cavity penetrating the first buffer layer and the first lower step, and a first main cavity penetrating the first substrate. The first branch cavity is connected to the first main cavity, and the width of the first main cavity is greater than the width of the first branch cavity.

[0014] The second cavity includes a second branch cavity penetrating the second buffer layer and the second lower step, and a second main cavity penetrating the second substrate. The second branch cavity is connected to the second main cavity, and the width of the second main cavity is greater than the width of the second branch cavity.

[0015] In some embodiments, the first GaN-based LED structure further includes a first passivation layer, a first n-type electrode, and a first p-type electrode covering the surface of the first GaN-based device layer. The first n-type electrode penetrates the first passivation layer and is electrically connected to the first lower step. The first p-type electrode penetrates the first passivation layer and is electrically connected to the first p-type GaN layer. The first cavity penetrates the first passivation layer. The first n-type electrode and the first cavity are located on opposite sides of the first upper step.

[0016] The second GaN-based LED structure further includes a second passivation layer covering the surface of the second GaN-based device layer, a second n-type electrode, and a second p-type electrode. The second n-type electrode penetrates the second passivation layer and is electrically connected to the second lower step. The second p-type electrode penetrates the second passivation layer and is electrically connected to the second p-type GaN layer. The second branch cavity penetrates the second passivation layer. The second n-type electrode and the second branch cavity are located on opposite sides of the second upper step.

[0017] In some embodiments, the projection of the first upper step onto the first substrate is entirely located inside the first main cavity, and the projection of the second upper step onto the second substrate is entirely located inside the second main cavity.

[0018] In some embodiments, the first main cavity and the second main cavity are partially offset, and the first main cavity and the second main cavity are connected and together constitute a microfluidic main cavity, with the first branch cavity and the second branch cavity located on opposite sides of the microfluidic main cavity.

[0019] In some embodiments, it also includes:

[0020] An adhesive layer is located between the first substrate and the second substrate, and the material of the adhesive layer is ethyl cyanoacrylate or vacuum sealing wax.

[0021] In some embodiments, the thickness of the first buffer layer and the second buffer layer are both 700 nm, the thickness of the first n-type GaN layer and the second n-type GaN layer are both 2800 nm, the thickness of the first InGaN layer and the second InGaN layer are both 70 nm, the thickness of the first InGaN / GaN quantum well active layer and the second InGaN / GaN quantum well active layer are both 50 nm, and the thickness of the first p-type GaN layer and the second p-type GaN layer are both 125 nm.

[0022] To address the aforementioned problems, this invention also provides a method for fabricating a suspended GaN-based LED device for microfluidic material detection, comprising the following steps:

[0023] A first GaN-based LED structure and a second GaN-based LED structure are formed. The first GaN-based LED structure includes a first substrate, a first buffer layer on the first substrate, a first GaN-based device layer on the first buffer layer, and a first cavity. The first cavity penetrates the first substrate, the first buffer layer, and a portion of the first GaN-based device layer. The second GaN-based LED structure includes a second substrate, a second buffer layer on the second substrate, a second GaN-based device layer on the second buffer layer, and a second cavity. The second cavity penetrates the second substrate, the second buffer layer, and a portion of the second GaN-based device layer.

[0024] The first GaN-based LED structure and the second GaN-based LED structure are connected with the first substrate facing the second substrate, and the first cavity is connected to the second cavity.

[0025] In some embodiments, the specific steps for forming the first GaN-based LED structure and the second GaN-based LED structure include:

[0026] Provide a first substrate and a second substrate;

[0027] The first buffer layer and the first GaN-based device layer are sequentially formed on the first substrate, and the second buffer layer and the second GaN-based device layer are sequentially formed on the second substrate;

[0028] A first cavity is formed that penetrates the first buffer layer and a portion of the first GaN-based device layer, and a second cavity is formed that penetrates the second buffer layer and a portion of the second GaN-based device layer;

[0029] A first main cavity is formed that penetrates the first substrate and communicates with the first branch cavity, and a second main cavity is formed that penetrates the second substrate and communicates with the second branch cavity. The width of the first main cavity is greater than the width of the first branch cavity, and the width of the second main cavity is greater than the width of the second branch cavity. The first branch cavity and the first main cavity together constitute the first cavity, and the second branch cavity and the second main cavity together constitute the second cavity.

[0030] The present invention provides a suspended GaN-based LED device for microfluidic material detection and its fabrication method. By connecting a first GaN-based LED structure with a first cavity and a second GaN-based LED structure with a second cavity, and making the first cavity and the second cavity interconnected to form a microfluidic detection cavity, the invention combines microfluidic material detection technology with visible light communication technology, expanding the application fields of visible light communication technology and microfluidic material detection technology. Furthermore, the fabrication method of the suspended GaN-based LED device for microfluidic material detection provided by the present invention is simple and low-cost, thereby reducing the cost of microfluidic material detection. In addition, the present invention can utilize the multiple functionalities of the first GaN-based LED structure and the second GaN-based LED structure to combine microfluidic material detection with multiple functions such as lighting and communication, thereby achieving the integration of multiple complex systems. Attached Figure Description

[0031] Appendix Figure 1 This is a schematic diagram of the structure of the suspended GaN-based LED device for microfluidic material detection provided by the present invention;

[0032] Appendix Figure 2 This is a flowchart of the fabrication method of the suspended GaN-based LED device for microfluidic material detection provided by the present invention;

[0033] Appendix Figure 3 - Appendix Figure 12 This is a schematic diagram of the main process structure in the fabrication of a suspended GaN-based LED device for microfluidic material detection according to the present invention. Detailed Implementation

[0034] The following detailed description, in conjunction with the accompanying drawings, illustrates the specific embodiments of the suspended GaN-based LED device for microfluidic material detection and its fabrication method provided by the present invention.

[0035] This specific embodiment provides a suspended GaN-based LED device for microfluidic material detection, with appended... Figure 1 This is a schematic diagram of the structure of the suspended GaN-based LED device for microfluidic material detection provided by the present invention. Figure 1 As shown, the suspended GaN-based LED device for microfluidic material detection includes:

[0036] The first GaN-based LED structure includes a first substrate 10, a first buffer layer 11 located on the first substrate 10, a first GaN-based device layer located on the first buffer layer 11, and a first cavity, wherein the first cavity penetrates the first substrate 10, the first buffer layer 11, and a portion of the first GaN-based device layer.

[0037] The second GaN-based LED structure includes a second substrate 20, a second buffer layer 21 located on the second substrate 20, a second GaN-based device layer located on the second buffer layer 21, and a second cavity, wherein the second cavity penetrates the second substrate 20, the second buffer layer 21, and a portion of the second GaN-based device layer.

[0038] The first GaN-based LED structure is located above the second GaN-based LED structure, and the first substrate 10 is connected to the second substrate 20, and the first cavity is connected to the second cavity.

[0039] Specifically, the suspended GaN-based LED device for microfluidic material detection includes a first GaN-based LED structure and a second GaN-based LED structure. The first GaN-based LED structure includes a first cavity penetrating the first substrate 10, the first buffer layer 11, and a portion of the first GaN-based device layer, thus making the first GaN-based LED structure a suspended structure. The second GaN-based LED structure includes a second cavity penetrating the second substrate 20, the second buffer layer 21, and a portion of the second GaN-based device layer, thus also making the second GaN-based LED structure a suspended structure. The first cavity and the second cavity are connected, and can thus jointly serve as a microfluidic detection cavity in the microfluidic material detection process. Both the first GaN-based LED structure and the second GaN-based LED structure possess the physical characteristic of coexisting light emission and detection. Therefore, one of the first GaN-based LED structure and the second GaN-based LED structure can be used as the excitation light source and the other as the detection light source in the microfluidic material detection process. The detection light signal emitted by the excitation light source is received by the analyte within the microfluidic detection cavity, exciting the analyte to generate an excitation light signal. The detection light source receives the excitation light signal, converts it into an electrical signal, and outputs it to the outside, thereby achieving microfluidic optical detection of the analyte. In one example, the first GaN-based LED structure is used as the excitation light source, and the second GaN-based LED structure is used as the detection light source. This specific embodiment enables precise detection of fluid substances in the environment through the microfluidic detection cavity.

[0040] In some embodiments, the first GaN-based device layer includes a first n-type GaN layer, a first InGaN layer 14 located on the first n-type GaN layer, a first InGaN / GaN quantum well active layer 15 located on the first InGaN layer 14, and a first p-type GaN layer 16 located on the first InGaN / GaN quantum well active layer 15. The first n-type GaN layer includes a first lower step 12 and a first upper step 13 located on the first lower step 12. The first InGaN layer 14 is located on the first upper step 13, and the first cavity penetrates the first lower step 12.

[0041] The second GaN-based device layer includes a second n-type GaN layer, a second InGaN layer 24 located on the second n-type GaN layer, a second InGaN / GaN quantum well active layer 25 located on the second InGaN layer 24, and a second p-type GaN layer 26 located on the second InGaN / GaN quantum well active layer 25. The second n-type GaN layer includes a second lower step 22 and a second upper step 23 located on the second lower step 22. The second InGaN layer 24 is located on the second upper step 23, and the second cavity penetrates the second lower step 22.

[0042] Specifically, such as Figure 1 As shown, in the first GaN-based LED structure, the first n-type GaN layer is stepped, including a first lower step 12 and a first upper step 13 protruding from the first lower step 12. The first InGaN layer 14, the first InGaN / GaN quantum well active layer 15, and the first p-type GaN layer 16 are sequentially stacked on the first upper step 13 along the first direction D1. The first direction D1 is perpendicular to the top surface of the first substrate 10, which refers to the surface of the first substrate 10 facing the first GaN-based device layer. In the second GaN-based LED structure, the second n-type GaN layer is stepped, including a second lower step 22 and a second upper step 23 protruding from the second lower step 22. The second InGaN layer 24, the second InGaN / GaN quantum well active layer 25, and the second p-type GaN layer 26 are sequentially stacked on the second upper step 23 along the first direction D1.

[0043] In some embodiments, the first cavity includes a first branch cavity 301 penetrating the first buffer layer 11 and the first lower step 12, and a first main cavity 302 penetrating the first substrate 10. The first branch cavity 301 is connected to the first main cavity 302, and the width of the first main cavity 302 is greater than the width of the first branch cavity 301.

[0044] The second cavity includes a second branch cavity 303 penetrating the second buffer layer 21 and the second lower step 22, and a second main cavity 304 penetrating the second substrate 20. The second branch cavity 303 is connected to the second main cavity 304, and the width of the second main cavity 304 is greater than the width of the second branch cavity 303.

[0045] Specifically, the width of the first main cavity 302 being greater than the width of the first branch cavity 301 means that the width of the first main cavity 302 along at least the second direction D2 is greater than the width of the first branch cavity 301 along the second direction D2, where the second direction D2 is parallel to the top surface of the first substrate 10. The width of the second main cavity 304 being greater than the width of the second branch cavity 303 means that the width of the second main cavity 304 along at least the second direction D2 is greater than the width of the second branch cavity 303 along the second direction D2. By making the width of the first main cavity 302 greater than the width of the first branch cavity 301, the reception rate of the detection light signal emitted by the excitation light source by the analyte located within the microfluidic detection cavity can be increased, i.e., the utilization rate of the detection light signal emitted by the excitation light source can be improved. By making the width of the second main cavity 304 greater than the width of the second branch cavity 303, the reception rate of the excitation light signal emitted by the test object by the detection light source can be increased, thereby helping to further improve the detection sensitivity of the suspended GaN-based LED device for microfluidic material detection.

[0046] In some embodiments, the first GaN-based LED structure further includes a first passivation layer 19, a first n-type electrode 18, and a first p-type electrode 17 covering the surface of the first GaN-based device layer. The first n-type electrode 18 penetrates the first passivation layer 19 and is electrically connected to the first lower step 12. The first p-type electrode 17 penetrates the first passivation layer 19 and is electrically connected to the first p-type GaN layer 16. The first branch cavity 301 penetrates the first passivation layer 19. The first n-type electrode 18 and the first branch cavity 301 are located on opposite sides of the first upper step 13.

[0047] The second GaN-based LED structure further includes a second passivation layer 29, a second n-type electrode 28, and a second p-type electrode 27 covering the surface of the second GaN-based device layer. The second n-type electrode 28 penetrates the second passivation layer 29 and is electrically connected to the second lower step 22. The second p-type electrode 27 penetrates the second passivation layer 29 and is electrically connected to the second p-type GaN layer 26. The second branch cavity 303 penetrates the second passivation layer 29. The second n-type electrode 28 and the second branch cavity 303 are located on opposite sides of the second upper step 23.

[0048] For example, the first n-type electrode 18 and the first branch cavity 301 are located on opposite sides of the first upper step 13 along the second direction D2, and the second n-type electrode 28 and the second branch cavity 303 are located on opposite sides of the second upper step 23 along the second direction D2. This specific embodiment, by setting the first n-type electrode 18 and the first branch cavity 301 to be located on opposite sides of the first upper step 13, and the second n-type electrode 28 and the second branch cavity 303 to be located on opposite sides of the second upper step 23, simplifies the manufacturing process of the suspended GaN-based LED device for microfluidic material detection while avoiding the influence of the analyte flow on the first n-type electrode 18 and the second n-type electrode 28. In one example, the materials of the first n-type electrode 18 and the second n-type electrode 28 are both Ti / Pt / Au metal alloys, and the thickness of the Ti metal layer in the first n-type electrode 18 and the second n-type electrode 28 is 30 nm, the thickness of the Pt metal layer is 100 nm, and the thickness of the Au metal layer is 200 nm. The materials of the first p-type electrode 17 and the second p-type electrode 27 are both Ni / Au metal alloys, and the thickness of the Ni metal layer in the first p-type electrode 17 and the thickness of the Au metal layer in the second p-type electrode 27 are 20 nm and 200 nm, respectively.

[0049] In one example, both the first passivation layer 19 and the second passivation layer 29 are made of silicon dioxide. By providing the first passivation layer 19 and the second passivation layer 29, the leakage current of the first GaN-based LED structure and the second GaN-based LED structure can be reduced, and the influence of the external environment on the first GaN-based LED structure and the second GaN-based LED structure can be avoided (e.g., preventing the external environment from oxidizing the first GaN-based LED structure and the second GaN-based LED structure). The thickness of the first passivation layer 19 and the thickness of the second passivation layer 29 can be the same, for example, both 200 nm.

[0050] In order to further improve the detection accuracy and sensitivity while improving the utilization rate of the detection optical signal, in some embodiments, the projection of the first upper step 13 on the first substrate 10 is entirely located inside the first main cavity 302, and the projection of the second upper step 23 on the second substrate 20 is entirely located inside the second main cavity 304.

[0051] In some embodiments, the first main cavity 302 and the second main cavity 304 are partially offset, and the first main cavity 302 and the second main cavity 304 are connected and together constitute a microfluidic main cavity. The first branch cavity 301 and the second branch cavity 303 are located on opposite sides of the microfluidic main cavity to increase the residence time of the analyte in the microfluidic main cavity, thereby further improving the accuracy and reliability of microfluidic detection.

[0052] To improve the overall structural stability of the suspended GaN-based LED device for microfluidic material detection, in some embodiments, the suspended GaN-based LED device for microfluidic material detection further includes:

[0053] An adhesive layer is located between the first substrate 10 and the second substrate 20, and the material of the adhesive layer is ethyl cyanoacrylate or vacuum sealing wax.

[0054] In other embodiments, the adhesive layer may be omitted, and the first substrate 10 and the second substrate 20 may be connected by bonding.

[0055] In some embodiments, the thicknesses of the first buffer layer 11 and the second buffer layer 21 are both 700 nm, the thicknesses of the first n-type GaN layer and the second n-type GaN layer are both 2800 nm, the thicknesses of the first InGaN layer 14 and the second InGaN layer 24 are both 70 nm, the thicknesses of the first InGaN / GaN quantum well active layer 15 and the second InGaN / GaN quantum well active layer 25 are both 50 nm, and the thicknesses of the first p-type GaN layer 16 and the second p-type GaN layer 26 are both 125 nm. In one example, the materials of the first buffer layer 11 and the second buffer layer 12 are the same, and both are AlN / AlGaN (i.e., at least including AlN and AlGaN layers stacked along the first direction D1). The first InGaN / GaN quantum well active layer 15 includes InGaN and GaN layers alternately stacked along the first direction D1.

[0056] This specific embodiment is illustrated using the example where the first GaN-based LED structure and the second GaN-based LED structure are identical in specific structure. In other embodiments, the structures of the first GaN-based LED structure and the second GaN-based LED structure may also differ, for example, depending on the wavelength of the excitation light source or the detection wavelength of the detection light source required in the microfluidic material detection process.

[0057] This specific embodiment also provides a method for fabricating a suspended GaN-based LED device for microfluidic material detection, attached... Figure 2 This is a flowchart illustrating the fabrication method of a suspended GaN-based LED device for microfluidic material detection provided by the present invention. Figure 3 - Appendix Figure 12 This is a schematic diagram of the main process structure in the fabrication of the suspended GaN-based LED device for microfluidic material detection according to the present invention. A schematic diagram of the structure of the suspended GaN-based LED device for microfluidic material detection prepared in this specific embodiment can be found in [reference needed]. Figure 1 .like Figures 1-12 As shown, the fabrication method of the suspended GaN-based LED device for microfluidic material detection includes the following steps:

[0058] Step S21: Form a first GaN-based LED structure and a second GaN-based LED structure. The first GaN-based LED structure includes a first substrate 10, a first buffer layer 11 on the first substrate 10, a first GaN-based device layer on the first buffer layer 11, and a first cavity. The first cavity penetrates the first substrate 10, the first buffer layer 11, and a portion of the first GaN-based device layer. The second GaN-based LED structure includes a second substrate 20, a second buffer layer 21 on the second substrate 20, a second GaN-based device layer on the second buffer layer 21, and a second cavity. The second cavity penetrates the second substrate 20, the second buffer layer 21, and a portion of the second GaN-based device layer.

[0059] Step S22: Connect the first GaN-based LED structure and the second GaN-based LED structure with the first substrate 10 facing the second substrate 20, and make the first cavity communicate with the second cavity.

[0060] In some embodiments, the specific steps for forming the first GaN-based LED structure and the second GaN-based LED structure include:

[0061] A first substrate 10 and a second substrate 20 are provided;

[0062] The first buffer layer 11 and the first GaN-based device layer are sequentially formed on the first substrate 10, and the second buffer layer 21 and the second GaN-based device layer are sequentially formed on the second substrate 20.

[0063] A first branch cavity 301 is formed that penetrates the first buffer layer 11 and a portion of the first GaN-based device layer, and a second branch cavity 303 is formed that penetrates the second buffer layer 21 and a portion of the second GaN-based device layer.

[0064] A first main cavity 302 is formed that penetrates the first substrate 10 and communicates with the first branch cavity 301, and a second main cavity 304 is formed that penetrates the second substrate 20 and communicates with the second branch cavity 303. The width of the first main cavity 302 is greater than the width of the first branch cavity 301, and the width of the second main cavity 304 is greater than the width of the second branch cavity 303. The first branch cavity 301 and the first main cavity 302 together constitute the first cavity, and the second branch cavity 303 and the second main cavity 304 together constitute the second cavity.

[0065] The following example illustrates the formation process of the first GaN-based LED structure. The first substrate 10 can be a silicon substrate. An AlN / AlGaN buffer layer (i.e., the first buffer layer 11), a first n-type GaN layer 31, a first InGaN layer 14, a first InGaN / GaN quantum well active layer 15, and a first p-type GaN layer 16 can be sequentially grown along the first direction D1 on the top surface of the first substrate 10 using a metal-organic chemical vapor deposition (MOCVD) process. Figure 3 As shown. Photoresist is spin-coated onto the surface of the first p-type GaN layer 16, and pre-baked (e.g., pre-baked at 100°C for 3 min). Using ultraviolet lithography (e.g., exposure for 18 s), a pattern is formed on the photoresist using a mask, and then developed (e.g., developed for 1 min 20 s), forming the desired shape. Figure 4 The photoresist layer 40 is shown. The photoresist layer 40 has an etching window that exposes a portion of the first p-type GaN layer 16. Next, the first p-type GaN layer 16, the first InGaN / GaN quantum well active layer 15, the first InGaN layer 14, and the first n-type GaN layer 31 are anisotropically etched along the etching window using a first inductively coupled plasma etching (ICP) process to form a stepped first n-type GaN layer, as shown. Figure 5 The stepped first n-type GaN layer includes a first lower step 12 and a first upper step 13 protruding along the first direction D1 and disposed on the first lower step 12. The remaining first p-type GaN layer 16, the first InGaN / GaN quantum well active layer 15, and the first InGaN layer 14 are all located above the first upper step 13. In one example, the etching gas used in the first inductively coupled plasma etching process is a mixture of Cl2 and BCl3, with flow rates of 25 sccm and 10 sccm, respectively, a pressure of 10 mTorr, an ICP power of 300 W, an RF power of 100 W, and a time of 8 min. The etching depth of this inductively coupled plasma etching process can be 800 nm.

[0066] Subsequently, the first lower step 12 and the first buffer layer 11 are anisotropically etched using a second inductively coupled plasma etching process to form the first branch cavity 301, as shown below. Figure 6 As shown. In one example, the etching gas used in the second inductively coupled plasma etching process is a mixture of Cl2 and BCl3, with flow rates of 25 sccm and 10 sccm, respectively, a pressure of 10 mTorr, an ICP power of 1000 W, an RF power of 300 W, and a time of 3 min. The depth of the first cavity 301 can be 3 μm. Next, an insulating material such as silicon dioxide is deposited on the first substrate 10 using plasma-enhanced chemical vapor deposition (PECVD) to form a first passivation layer 19 covering the surface of the first lower step 12, the sidewalls of the first upper step 13, the sidewalls of the first InGaN layer 14, the sidewalls of the first InGaN / GaN quantum well active layer 15, the sidewalls and top surface of the first p-type GaN layer 16, and the inner wall of the first cavity 301, as shown. Figure 7 As shown. In the plasma-enhanced chemical vapor deposition process, the deposition gas is a mixture of N2 (mixed with 5% SiH4) and N2O, with flow rates of 100 sccm and 400 sccm, respectively, a pressure of 300 mTorr, a power of 10 W, a temperature of 350 °C, and a time of 9 min 30 s.

[0067] Reactive ion etching (RIE) is used to remove a portion of the first passivation layer 19 above the first p-type GaN layer 16, a portion of the first passivation layer 19 on the first lower step 12, and all of the first passivation layer 19 within the first cavity 301, forming a first p-type electrode trench 81 exposing the first p-type GaN layer 16 and a first n-type electrode trench 80 exposing the first lower step 12, as shown below. Figure 8 As shown. During reactive ion etching, the etching gas used is a mixture of CF4 and O2, with flow rates of 30 sccm and 10 sccm respectively, a pressure of 4 Pa, a power of 150 W, and a time of 4 min. The first n-type electrode trench 80 and the first branch cavity 301 are located on opposite sides of the first upper step 13 along the second direction D2. Next, a first n-type electrode 18 is formed in the first n-type electrode trench 80 using physical vapor deposition (PVD) (e.g., sequentially depositing a layer of titanium (Ti), a layer of platinum (Pt), and a layer of gold (Au)). Ohmic contact between the first n-type electrode 18 and the first lower step 12 is achieved through rapid annealing (e.g., rapid annealing at 600°C for 30 s in a N2 environment). Figure 9As shown. Then, a first p-type electrode 17 is formed in the first p-type electrode trench 81 using a physical chemical vapor deposition process (e.g., sequentially depositing a layer of nickel (Ni) and a layer of gold (Au)). Ohmic contact between the first p-type electrode 17 and the first p-type GaN layer 16 is achieved through rapid annealing (e.g., rapid annealing at 550°C for 5 min in an argon atmosphere). Figure 10 As shown. Then, using a third inductively coupled plasma etching process, the first substrate 10 is etched from the back side (i.e., the surface opposite to the top surface of the first substrate 10) to form a first main cavity 302 that penetrates the first substrate 10 and communicates with the first branch cavity 301, as shown. Figure 11 As shown. The etching gas used in the third inductively coupled plasma etching process is a mixture of SF6 and O2, with flow rates of 48 sccm and 6 sccm, respectively, a pressure of 10 mTorr, an ICP power of 600 W, an RF power of 10 W, and a time of 30 min. The second GaN-based LED structure can be formed using the same method as the first GaN-based LED structure. Then, the first substrate 10 and the second substrate 20 are connected by an adhesive layer to form the suspended GaN-based LED device for microfluidic material detection.

[0068] This specific embodiment provides a suspended GaN-based LED device for microfluidic material detection and its fabrication method. By connecting a first GaN-based LED structure with a first cavity and a second GaN-based LED structure with a second cavity, and making the first cavity and the second cavity interconnected to form a microfluidic detection cavity, it realizes the combination of microfluidic material detection technology and visible light communication technology, expanding the application fields of visible light communication technology and microfluidic material detection technology. Moreover, the fabrication method of the suspended GaN-based LED device for microfluidic material detection provided in this specific embodiment is simple and low-cost, thereby reducing the cost of microfluidic material detection. In addition, this invention can also utilize the multiple functionalities of the first GaN-based LED structure and the second GaN-based LED structure to combine microfluidic material detection with multiple functions such as lighting and communication, so as to achieve the integration of multiple complex systems.

[0069] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A suspended GaN-based LED device for microfluidic substance detection, characterized in that, include: The first GaN-based LED structure includes a first substrate, a first buffer layer on the first substrate, a first GaN-based device layer on the first buffer layer, and a first cavity, wherein the first cavity penetrates the first substrate, the first buffer layer, and a portion of the first GaN-based device layer. The second GaN-based LED structure includes a second substrate, a second buffer layer on the second substrate, a second GaN-based device layer on the second buffer layer, and a second cavity, wherein the second cavity penetrates the second substrate, the second buffer layer, and a portion of the second GaN-based device layer. The first GaN-based LED structure is located above the second GaN-based LED structure, and the first substrate is connected to the second substrate, and the first cavity is connected to the second cavity; The first GaN-based device layer includes a first n-type GaN layer, a first InGaN layer on the first n-type GaN layer, a first InGaN / GaN quantum well active layer on the first InGaN layer, and a first p-type GaN layer on the first InGaN / GaN quantum well active layer. The first n-type GaN layer includes a first lower step and a first upper step on the first lower step. The first InGaN layer is located on the first upper step, and the first cavity penetrates the first lower step. The second GaN-based device layer includes a second n-type GaN layer, a second InGaN layer on the second n-type GaN layer, a second InGaN / GaN quantum well active layer on the second InGaN layer, and a second p-type GaN layer on the second InGaN / GaN quantum well active layer. The second n-type GaN layer includes a second lower step and a second upper step on the second lower step. The second InGaN layer is located on the second upper step, and the second cavity penetrates the second lower step. The first cavity includes a first branch cavity penetrating the first buffer layer and the first lower step, and a first main cavity penetrating the first substrate. The first branch cavity is connected to the first main cavity, and the width of the first main cavity is greater than the width of the first branch cavity. The second cavity includes a second branch cavity penetrating the second buffer layer and the second lower step, and a second main cavity penetrating the second substrate. The second branch cavity is connected to the second main cavity, and the width of the second main cavity is greater than the width of the second branch cavity.

2. The suspended GaN-based LED device for microfluidic material detection according to claim 1, characterized in that, The first GaN-based LED structure further includes a first passivation layer, a first n-type electrode, and a first p-type electrode covering the surface of the first GaN-based device layer. The first n-type electrode penetrates the first passivation layer and is electrically connected to the first lower step. The first p-type electrode penetrates the first passivation layer and is electrically connected to the first p-type GaN layer. The first branch cavity penetrates the first passivation layer. The first n-type electrode and the first branch cavity are located on opposite sides of the first upper step. The second GaN-based LED structure further includes a second passivation layer covering the surface of the second GaN-based device layer, a second n-type electrode, and a second p-type electrode. The second n-type electrode penetrates the second passivation layer and is electrically connected to the second lower step. The second p-type electrode penetrates the second passivation layer and is electrically connected to the second p-type GaN layer. The second branch cavity penetrates the second passivation layer. The second n-type electrode and the second branch cavity are located on opposite sides of the second upper step.

3. The free-standing GaN-based LED device for microfluidic analyte detection of claim 1, wherein, The projection of the first upper step onto the first substrate is entirely located inside the first main cavity, and the projection of the second upper step onto the second substrate is entirely located inside the second main cavity.

4. The free-standing GaN-based LED device for microfluidic analyte detection of claim 2, wherein, The first main cavity and the second main cavity are partially offset, and the first main cavity and the second main cavity are connected and together constitute the microfluidic main cavity. The first branch cavity and the second branch cavity are located on opposite sides of the microfluidic main cavity.

5. The free-standing GaN-based LED device for microfluidic analyte detection of claim 1, wherein, Also includes: An adhesive layer is located between the first substrate and the second substrate, and the material of the adhesive layer is ethyl cyanoacrylate or vacuum sealing wax.

6. The free-standing GaN-based LED device for microfluidic analyte detection of claim 1, wherein, The thickness of the first buffer layer and the second buffer layer are both 700 nm, the thickness of the first n-type GaN layer and the second n-type GaN layer are both 2800 nm, the thickness of the first InGaN layer and the second InGaN layer are both 70 nm, the thickness of the first InGaN / GaN quantum well active layer and the second InGaN / GaN quantum well active layer are both 50 nm, and the thickness of the first p-type GaN layer and the second p-type GaN layer are both 125 nm.

7. The method for fabricating a free-standing GaN-based LED device for microfluidic substance detection according to claim 1, wherein, Includes the following steps: A first GaN-based LED structure and a second GaN-based LED structure are formed. The first GaN-based LED structure includes a first substrate, a first buffer layer on the first substrate, a first GaN-based device layer on the first buffer layer, and a first cavity. The first cavity penetrates the first substrate, the first buffer layer, and a portion of the first GaN-based device layer. The second GaN-based LED structure includes a second substrate, a second buffer layer on the second substrate, a second GaN-based device layer on the second buffer layer, and a second cavity. The second cavity penetrates the second substrate, the second buffer layer, and a portion of the second GaN-based device layer. The first GaN-based LED structure and the second GaN-based LED structure are connected with the first substrate facing the second substrate, and the first cavity is connected to the second cavity.

8. The method for fabricating a suspended GaN-based LED device for microfluidic material detection according to claim 7, characterized in that, The specific steps for forming the first GaN-based LED structure and the second GaN-based LED structure include: Provide a first substrate and a second substrate; The first buffer layer and the first GaN-based device layer are sequentially formed on the first substrate, and the second buffer layer and the second GaN-based device layer are sequentially formed on the second substrate; A first cavity is formed that penetrates the first buffer layer and a portion of the first GaN-based device layer, and a second cavity is formed that penetrates the second buffer layer and a portion of the second GaN-based device layer; A first main cavity is formed that penetrates the first substrate and communicates with the first branch cavity, and a second main cavity is formed that penetrates the second substrate and communicates with the second branch cavity. The width of the first main cavity is greater than the width of the first branch cavity, and the width of the second main cavity is greater than the width of the second branch cavity. The first branch cavity and the first main cavity together constitute the first cavity, and the second branch cavity and the second main cavity together constitute the second cavity.

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