Active integrated silicon nitride photonic crystal resonant cavity sensor and preparation method thereof

Abstract

The present invention discloses an active integrated silicon nitride photonic crystal resonant cavity sensor and a preparation method. The present invention proposes an active integrated photonic crystal sensor structure, including a defect-free, defective or heterostructured photonic resonant cavity composed of a one-dimensional or two-dimensional periodic photonic crystal structure. A GaN-based blue light material system including a multi-layer quantum well composed of InGaN and GaN alternatingly, a silicon dioxide coating layer and a silicon nitride layer are grown on a sapphire substrate, and air holes are etched in the silicon nitride layer to form a photonic crystal resonant cavity, thereby realizing a refractive index sensor structure. Compared with traditional sensors, the photonic crystal resonant cavity sensor realizes monolithic active integration, realizes the integrated integration of light source and sensor element, has a smaller size and a higher integration level; at the same time, the photonic crystal resonant cavity sensor uses silicon nitride as the photonic crystal resonant cavity material, which has the characteristics of low loss and high Q value, and is conducive to realizing high-sensitivity and low-threshold sensing detection.

Description

Technical Field

[0001] The invention discloses an active integrated silicon nitride photonic crystal resonant cavity sensor and a preparation method thereof, and relates to the technical field of photonic crystal sensors. Background Art

[0002] In recent decades, the research on sensors has gradually matured. Photonic crystal resonant cavity sensors have attracted much attention in the field of sensing technology and are widely used in detection in various fields.

[0003] Currently, common photonic crystal resonant cavity sensors are divided into two structures: one-dimensional photonic crystal and two-dimensional photonic crystal. In order to obtain higher sensitivity, most photonic crystal resonant cavity sensors are usually made of materials with higher refractive index (RI) to achieve high Q value. High Q value corresponds to narrower resonance linewidth, which enables the sensor to distinguish smaller deviations of the resonance wavelength. On the other hand, the increase in the refractive index of the medium makes the light more confined in the medium, and the light field is strongly confined to the area of ​​high refractive index materials, which makes the overlap between the object to be detected and the light field small, and the light-object interaction is low, which is not conducive to improving sensitivity. Therefore, it is necessary to comprehensively consider the influence of refractive index (RI) on Q value and light-object interaction. Summary of the invention

[0004] In view of the defects in the above-mentioned background technology, the present invention provides an active integrated silicon nitride photonic crystal resonant cavity sensor and a preparation method, which realizes the integrated integration of light source and sensor element, has smaller size, higher integration, stable performance and more convenient operation.

[0005] To achieve the above-mentioned object, the technical solution adopted by the present invention is as follows: an active integrated silicon nitride photonic crystal resonant cavity sensor, characterized in that it comprises: a silicon substrate layer;

[0006] n-GaN layer, located on the silicon substrate layer;

[0007] MQWs layer, located on the n-GaN layer;

[0008] p-AlGaN electron blocking layer, located on the MQWs layer;

[0009] A p-GaN layer located on the p-AlGaN electron blocking layer;

[0010] SiO2 layer, located on the p-GaN layer;

[0011] A photonic crystal layer, located on the SiO2 layer;

[0012] A p-electrode is arranged on the surface of the p-GaN layer, and an n-electrode is arranged on the surface of the n-GaN layer.

[0013] Furthermore, the MQWs layer includes: a multilayer quantum well layer composed of InGaN and GaN alternately, the number of the multilayer quantum well layers is 1 to 13, each layer includes: 3 nm thick InGaN and 10 nm thick GaN, and the content of In in the InGaN layer is: 5% to 20%; to achieve continuous adjustable active wavelength selection from blue light to green light;

[0014] Furthermore, the thickness of the p-AlGaN electron blocking layer is 10-50 nm, and the thickness of the p-GaN layer is 50-200 nm.

[0015] Furthermore, the thickness of the SiO2 layer is 500-5000 nm, and the thickness of the photonic crystal layer is 50-300 nm.

[0016] Furthermore, the photonic crystal layer is made of Si3N4.

[0017] Furthermore, the photonic crystal layer includes: a one-dimensional photonic crystal structure and a two-dimensional photonic crystal structure, wherein the air holes are circular, the radius is 10-100 nm, and the lattice constant is 50-200 nm.

[0018] By adjusting parameters such as the SiO2 layer thickness, Si3N4 photonic crystal layer thickness, lattice constant and duty cycle, different resonant frequencies, quality factors, light field distributions, distribution patterns and mode field volumes can be achieved, thereby optimizing the sensor's sensitivity, detection threshold and other performance.

[0019] Furthermore, the resonant cavity of the one-dimensional photonic crystal structure is of a hole defect type or a hole gradient type.

[0020] Furthermore, the resonant cavity of the two-dimensional photonic crystal structure is of a hole defect type, a hole heterostructure type, or a uniform type.

[0021] A method for preparing an active integrated silicon nitride photonic crystal resonant cavity sensor comprises the following steps:

[0022] Step 1: On a sapphire substrate, III-V compound materials are grown layer by layer to form a GaN-based active wafer;

[0023] Step 2: growing a SiO2 layer of a certain thickness on the surface of the grown GaN-based active wafer, and then growing a Si3N4 layer of a certain thickness on the surface of the SiO2 layer;

[0024] Step 3: performing electron beam lithography on the surface of Si3N4 to form a photonic crystal mask structure; performing dry or wet etching of Si3N4 to form a hole structure, and removing the electron beam glue of the electron beam lithography;

[0025] Step 4: using photolithography and Si3N4 and SiO2 layer etching processes to leave the Si3N4 photonic crystal layer and SiO2 coating layer in the set area;

[0026] Step 5: Prepare a p-electrode in a set area on the p-GaN surface using photolithography and lift-off processes;

[0027] Step 6: Using photolithography and III-V etching process, the set area is etched from top to bottom to the n-GaN layer;

[0028] Step 7: Prepare an n-electrode in a designated area on the n-GaN surface using photolithography and lift-off processes.

[0029] Working principle: The active quantum well layer of gallium nitride is electroluminescent. Adjusting the indium component of the quantum well can cover the emission of blue-green light. The emitted light is transmitted to the photonic crystal layer. Since the low-refractive-index silicon oxide layer serves as the cladding layer of the photonic crystal layer, the light with a frequency that meets the resonance condition will form a steady-state resonance and be confined to the photonic crystal layer. The resonance peak can be obtained by measuring its transmission or reflection spectrum. Since the refractive index (RI) of the object to be detected affects the resonance wavelength, when the refractive index changes, it will cause the corresponding resonance wavelength to shift. By detecting the shift of the resonance peak spectrum, the change in the refractive index can be calculated.

[0030] Beneficial effects: The photonic crystal resonant cavity sensor designed by the present invention uses Si3N4 photonic crystals, so that the photonic crystal resonant cavity sensor has higher performance; Si3N4 photonic crystals have high Q value and low loss characteristics, so that the resonant cavity sensor can distinguish smaller deviations of the resonant wavelength; at the same time, the refractive index of Si3N4 photonic crystals is relatively low, and the light-matter interaction is strong. Therefore, the photonic crystal resonant cavity sensor designed by the present invention has higher sensitivity and lower threshold.

[0031] The photonic crystal resonant cavity sensor designed in the present invention adopts a monolithic active integrated structure to realize the integrated integration of light source and sensor element, has a smaller size and a higher integration level, realizes the sensing of refractive index on a tiny chip, is not easily affected by external interference, has stable performance and is more convenient to operate. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of the side view structure of the photonic crystal resonant cavity sensor;

[0033] FIG2( a ) is a schematic diagram of a defective microcavity structure of a one-dimensional photonic crystal resonant cavity sensor;

[0034] FIG2( b ) is a schematic diagram of a one-dimensional photonic crystal resonant cavity sensor with a gradual change microcavity structure;

[0035] FIG3( a ) is a schematic diagram of a square lattice uniform microcavity structure of a two-dimensional photonic crystal resonant cavity sensor;

[0036] FIG3( b ) is a schematic diagram of a square lattice defect microcavity structure of a two-dimensional photonic crystal resonant cavity sensor;

[0037] FIG3( c ) is a schematic diagram of a square lattice heterostructure microcavity structure of a two-dimensional photonic crystal resonant cavity sensor;

[0038] FIG3( d ) is a schematic diagram of a triangular lattice uniform microcavity structure of a two-dimensional photonic crystal resonant cavity sensor;

[0039] Figure 3(e) is a schematic diagram of the triangular lattice defect microcavity structure of a two-dimensional photonic crystal resonant cavity sensor;

[0040] Figure 3(f) is a schematic diagram of the triangular lattice heterostructure microcavity structure of a two-dimensional photonic crystal resonant cavity sensor;

[0041] Figure 3(g) is a schematic diagram of the honeycomb lattice uniform microcavity structure of a two-dimensional photonic crystal resonant cavity sensor;

[0042] Figure 3(h) is a schematic diagram of the honeycomb lattice defect microcavity structure of a two-dimensional photonic crystal resonant cavity sensor;

[0043] FIG3(i) is a schematic diagram of a honeycomb lattice heterostructure microcavity structure of a two-dimensional photonic crystal resonant cavity sensor;

[0044] Figure 4 Schematic diagram of the resonant wavelength shift achieved under different sensing media. DETAILED DESCRIPTION

[0045] The implementation of the technical solution is further described in detail below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention.

[0046] like Figure 1 An embodiment shown: an active integrated silicon nitride photonic crystal resonant cavity sensor, characterized in that it includes: a silicon substrate layer;

[0047] n-GaN layer, located on the silicon substrate layer;

[0048] MQWs layer, located on the n-GaN layer;

[0049] p-AlGaN electron blocking layer, located on the MQWs layer;

[0050] A p-GaN layer located on the p-AlGaN electron blocking layer;

[0051] SiO2 layer, located on the p-GaN layer;

[0052] A photonic crystal layer, located on the SiO2 layer;

[0053] A p-electrode is arranged on the surface of the p-GaN layer, and an n-electrode is arranged on the surface of the n-GaN layer.

[0054] The MQWs layer includes: a multilayer quantum well layer composed of InGaN and GaN alternately, the multilayer quantum well layer has 10 layers, each layer includes: 3 nm thick InGaN and 10 nm thick GaN, and the In content in the InGaN layer is: 5%~20%.

[0055] The thickness of the p-AlGaN electron blocking layer is 50 nm, and the thickness of the p-GaN layer is 200 nm.

[0056] The SiO2 layer has a thickness of 1000nm, and the photonic crystal layer uses Si3N4 with a thickness of 300nm.

[0057] The photonic crystal layer comprises: a one-dimensional photonic crystal structure and a two-dimensional photonic crystal structure, wherein the air holes are circular, the radius is 50nm, and the lattice constant is 200nm.

[0058] In one embodiment shown in FIG. 2 (a), a defective microcavity structure of a one-dimensional photonic crystal resonant cavity sensor is shown: the air holes of the photonic crystal structure are arranged periodically on the dielectric material, and a single air hole is missing in the central area;

[0059] In one embodiment as shown in FIG. 2 (b), a one-dimensional photonic crystal resonant cavity sensor has a gradient microcavity structure: the size of the air hole gradually increases or decreases from the center to the two ends;

[0060] As shown in FIG. 3 (a), an embodiment of a two-dimensional photonic crystal resonant cavity sensor square lattice uniform microcavity structure: air holes are arranged two-dimensionally periodically on the dielectric material, and the lattice type is a square lattice;

[0061] As shown in FIG. 3 (b), an embodiment of a two-dimensional photonic crystal resonant cavity sensor square lattice defect type microcavity structure: air holes are arranged two-dimensionally periodically on the dielectric material, the lattice type is a square lattice, and a single air hole is missing in the central area;

[0062] In one embodiment as shown in FIG. 3 (c), a square lattice heterostructure microcavity structure of a two-dimensional photonic crystal resonant cavity sensor: the lattice constant or the hole radius of the central region of the photonic crystal is different from that of other surrounding regions;

[0063] As shown in FIG. 3 (d), an embodiment of a two-dimensional photonic crystal resonant cavity sensor triangular lattice uniform microcavity structure: air holes are arranged two-dimensionally periodically on the dielectric material, and the lattice type is a triangular lattice;

[0064] As shown in FIG. 3 (e), an embodiment of a two-dimensional photonic crystal resonant cavity sensor triangular lattice defect type microcavity structure: air holes are arranged two-dimensionally periodically on the dielectric material, the lattice type is a triangular lattice, and a single air hole is missing in the central area;

[0065] In one embodiment as shown in FIG. 3 (f), a triangular lattice heterostructure microcavity structure of a two-dimensional photonic crystal resonant cavity sensor: the lattice constant or hole radius of the central region of the photonic crystal is different from that of other surrounding regions;

[0066] As shown in FIG. 3 (g), an embodiment of a two-dimensional photonic crystal resonant cavity sensor honeycomb lattice uniform microcavity structure: air holes are arranged two-dimensionally periodically on the dielectric material, and the lattice type is a honeycomb lattice;

[0067] An embodiment as shown in FIG. 3 (h) is a honeycomb lattice defect type microcavity structure of a two-dimensional photonic crystal resonant cavity sensor: air holes are arranged two-dimensionally periodically on the dielectric material, and the lattice type is a honeycomb lattice, and a single air hole is missing in the central area;

[0068] In one embodiment as shown in FIG. 3 (i), a honeycomb lattice heterostructure microcavity structure of a two-dimensional photonic crystal resonant cavity sensor: the lattice constant or the hole radius of the central region of the photonic crystal is different from that of other surrounding regions;

[0069] The above-mentioned different structures will have different resonance characteristics, such as quality factor, mode field volume, limitation factor of light field in medium and air, etc., thus having different sensing thresholds and sensitivities.

[0070] Example:

[0071] A method for preparing an active integrated silicon nitride photonic crystal resonant cavity sensor comprises the following steps:

[0072] Step 1: On a sapphire substrate, III-V compound materials are grown layer by layer to form a GaN-based active wafer;

[0073] Step 2: growing a SiO2 layer of a certain thickness on the surface of the grown GaN-based active wafer, and then growing a Si3N4 layer of a certain thickness on the surface of the SiO2 layer;

[0074] Step 3: performing electron beam lithography on the surface of Si3N4 to form a photonic crystal mask structure; performing dry or wet etching of Si3N4 to form a hole structure, and removing the electron beam glue of the electron beam lithography;

[0075] Step 4: using photolithography and Si3N4 and SiO2 layer etching processes to leave the Si3N4 photonic crystal layer and SiO2 coating layer in the set area;

[0076] Step 5: Prepare a p-electrode in a set area on the p-GaN surface using photolithography and lift-off processes;

[0077] Step 6: Using photolithography and III-V etching process, the set area is etched from top to bottom to the n-GaN layer;

[0078] Step 7: Prepare an n-electrode in a designated area on the n-GaN surface using photolithography and lift-off processes.

[0079] like Figure 4 As shown, it is a schematic diagram of the resonant wavelength shift achieved by the uniform square lattice structure of a two-dimensional photonic crystal in different refractive index media. It can be seen that the qualitative and quantitative measurement of the refractive index of the measured material can be achieved through the resonant frequency shift.

[0080] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. An active integrated silicon nitride photonic crystal resonant cavity sensor, characterized in that: include: Silicon substrate layer; n-GaN layer, located on the silicon substrate layer; MQWs layer, located on the n-GaN layer; p-AlGaN electron blocking layer, located on the MQWs layer; A p-GaN layer located on the p-AlGaN electron blocking layer; SiO2 layer, located on the p-GaN layer; A photonic crystal layer, located on the SiO2 layer; A p-electrode is arranged on the surface of the p-GaN layer, an n-electrode is arranged on the surface of the n-GaN layer, the MQWs layer comprises: a multilayer quantum well layer composed of InGaN and GaN alternately, the number of the multilayer quantum well layers is 1 to 13, each layer comprises: 3 nm thick InGaN and 10 nm thick GaN, the content of In in the InGaN layer is: 5%-20%, the photonic crystal layer comprises: a one-dimensional photonic crystal structure and a two-dimensional photonic crystal structure, the air hole of which is circular, the radius is 10 to 100 nm, and the lattice constant is 50 to 200 nm.

2. The active integrated silicon nitride photonic crystal resonant cavity sensor according to claim 1, characterized in that: The thickness of the p-AlGaN electron blocking layer is 10-50 nm, and the thickness of the p-GaN layer is 50-200 nm.

3. The active integrated silicon nitride photonic crystal resonant cavity sensor according to claim 1, characterized in that: The thickness of the SiO2 layer is 500-5000nm, and the thickness of the photonic crystal layer is 50-300nm.

4. The active integrated silicon nitride photonic crystal resonant cavity sensor according to claim 1, characterized in that: The photonic crystal layer is made of Si3N4.

5. The active integrated silicon nitride photonic crystal resonant cavity sensor according to claim 1, characterized in that: The resonant cavity of the one-dimensional photonic crystal structure is of a hole defect type or a hole gradient type.

6. The active integrated silicon nitride photonic crystal resonant cavity sensor according to claim 1, characterized in that: The resonant cavity of the two-dimensional photonic crystal structure is of a hole defect type, a hole heterostructure type or a uniform type.

7. A method for preparing an active integrated silicon nitride photonic crystal resonant cavity sensor according to any one of claims 1 to 6, characterized in that: The following steps are involved: Step 1: On a sapphire substrate, III-V compound materials are grown layer by layer to form a GaN-based active wafer; Step 2: growing a SiO2 layer of a certain thickness on the surface of the grown GaN-based active wafer, and then growing a Si3N4 layer of a certain thickness on the surface of the SiO2 layer; Step 3: performing electron beam lithography on the surface of Si3N4 to form a photonic crystal mask structure; performing dry or wet etching of Si3N4 to form a hole structure, and removing the electron beam glue of the electron beam lithography; Step 4: using photolithography and Si3N4 and SiO2 layer etching processes to leave the Si3N4 photonic crystal layer and SiO2 coating layer in the set area; Step 5: Prepare a p-electrode in a set area on the p-GaN surface using photolithography and lift-off processes; Step 6: Using photolithography and III-V etching process, the set area is etched from top to bottom to the n-GaN layer; Step 7: Prepare an n-electrode in a designated area on the n-GaN surface using photolithography and lift-off processes.

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