GaN-based photoelectric refractive index sensor with integrated guided mode resonant grating and preparation method thereof

Abstract

The present invention discloses a GaN-based photoelectric refractive index sensor with an integrated guided mode resonant grating and a preparation method thereof, and relates to the technical field of semiconductor photoelectric sensors. The present invention includes a substrate layer, a silicon dioxide bonding layer is formed on the substrate layer, and an LED structure and a light detector structure are formed on the upper part of the silicon dioxide layer, respectively, and an electrical isolation region is provided between the two. The present invention uses inductively coupled plasma etching technology to remove the gallium nitride buffer layer and the undoped gallium nitride layer, and further etches and thins the n-type gallium nitride layer, and finally etches to form a grating structure. The integration of the thinning process and the grating optimizes the light propagation path, improves the light extraction efficiency, and enhances the coupling effect between the light and the medium to be detected, thereby improving the sensitivity of the sensor. In addition, the present invention realizes the monolithic integration of light emission and light detection functions, and can realize a system-level sensor chip in combination with a driving circuit and a signal processing circuit, thereby improving the integration of the system.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor photoelectric sensors, in particular to a GaN-based photoelectric refractive index sensor integrated with a guided mode resonant grating and a preparation method thereof. Background Art

[0002] In recent years, with the increasing demand for high-sensitivity, real-time and portable sensors in the fields of biomedical testing, environmental monitoring, industrial automation, etc., optical sensor technology based on refractive index changes has received widespread attention. This type of sensor measures and analyzes the composition, concentration or physical parameters of a substance by detecting the change in the refractive index of light in the sample environment. It has significant advantages such as non-contact, fast response and high sensitivity. In this context, the research and development of GaN-based LED monolithic integrated refractive index sensors has become particularly important and necessary.

[0003] The light emission and detection functions of GaN-based LEDs are integrated into a single chip and applied to refractive index sensors. By utilizing the tunability of LED light sources and the highly sensitive photoelectric response characteristics, tiny refractive index changes in the environment can be detected in real time. This monolithic integrated design not only reduces the complexity and packaging cost of the system, but also improves the signal stability and detection accuracy of the sensor, thus having a wider application prospect. However, the current refractive index sensor technology still faces some urgent problems to be solved, such as insufficient sensitivity, large size and limited system integration compared with traditional discrete devices. These problems restrict its promotion in practical applications. To this end, we propose a GaN-based photoelectric refractive index sensor integrated with a guided mode resonant grating and its preparation method. Summary of the invention

[0004] The object of the present invention is to provide a GaN-based photoelectric refractive index sensor integrated with a guided mode resonant grating and a preparation method thereof, so as to solve the problems raised in the above background technology.

[0005] According to a first aspect of the present invention, in order to achieve the above-mentioned purpose, the present invention provides the following technical solution: a GaN-based photoelectric refractive index sensor with an integrated guided mode resonant grating, comprising a bonded sapphire substrate layer, a silicon dioxide bonding layer is formed above the bonded sapphire substrate layer, an LED structure and a photodetector structure are respectively formed above the silicon dioxide bonding layer, and an electrical isolation region is provided between the LED structure and the photodetector structure;

[0006] The LED structure and the photodetector structure both include a p-type gallium nitride layer formed on a silicon dioxide bonding layer, a multi-quantum well layer formed on the p-type gallium nitride layer, an n-type gallium nitride layer formed on the multi-quantum well layer, and an n-type ohmic contact electrode and a p-type ohmic contact electrode are deposited on the n-type gallium nitride layer and the p-type gallium nitride layer, respectively;

[0007] A grating region is etched on the upper surface of the n-type gallium nitride layer in the LED structure to form an n-type gallium nitride grating layer.

[0008] Furthermore, the thickness of the bonded sapphire substrate layer is set to 500-1500 μm.

[0009] Furthermore, the thickness of the silicon dioxide bonding layer is 1.5-2.5 μm; the thickness of the p-type gallium nitride layer is 0.1-0.15 μm.

[0010] Furthermore, the thickness of the multi-quantum well layer is 50-100 nm; the thickness of the n-type gallium nitride layer is 0.3-0.4 μm.

[0011] Furthermore, the thickness of the p-type ohmic contact electrode and the n-type ohmic contact electrode are both 0.1 μm.

[0012] According to a second aspect of the present invention, the present invention provides a method for preparing a GaN-based photoelectric refractive index sensor integrated with a guided mode resonant grating, which specifically comprises the following steps:

[0013] S1. sequentially growing a gallium nitride buffer layer, an undoped gallium nitride layer, an n-type gallium nitride layer, a multi-quantum well layer and a p-type gallium nitride layer on the original sapphire substrate layer to obtain an LED epitaxial layer;

[0014] S2. Bonding the LED epitaxial p-type gallium nitride layer to the bonded sapphire substrate layer;

[0015] S3. Laser stripping of the original sapphire substrate layer;

[0016] S4. Etching the bonded LED epitaxial layer device to remove the gallium nitride buffer layer and the undoped gallium nitride layer, and further thinning the n-type gallium nitride layer;

[0017] S5. patterning a grating region, an electrical isolation region, and a p-type ohmic contact electrode region on the surface of the n-type gallium nitride layer exposed after thinning, and etching the shape;

[0018] S6. Depositing an n-type ohmic contact electrode and a p-type ohmic contact electrode on the n-type gallium nitride layer and the p-type gallium nitride layer, respectively.

[0019] Furthermore, the LED epitaxial layer in S1 is grown by metal organic chemical vapor deposition, and the thickness of the original sapphire substrate layer is set to 500-1500 μm, the thickness of the gallium nitride buffer layer is set to 0.6-0.8 μm, the thickness of the undoped gallium nitride layer is set to 0.7-0.9 μm, the thickness of the n-type gallium nitride layer is set to 2.5-3 μm, the thickness of the multi-quantum well layer is set to 50-100 nm, and the thickness of the p-type gallium nitride layer is set to 0.1-0.15 μm.

[0020] Furthermore, in S2, silicon dioxide is used as a bonding layer to bond the LED epitaxial layer p-type gallium nitride layer to the bonded sapphire substrate layer.

[0021] Furthermore, in S4, the gallium nitride buffer layer and the undoped gallium nitride layer are removed by inductively coupled plasma technology, and the n-type gallium nitride layer is further thinned.

[0022] Furthermore, in S5, the grating region, the electrical isolation region, and the p-type ohmic contact electrode region are patterned respectively by using photolithography technology, and etching is performed by using inductively coupled plasma technology, wherein the grating region is set to be rectangular in shape, the grating period is 2.4 μm, the grating width is 1.2 μm, and the grating etching depth is 0.2 μm; the electrical isolation region is a long strip region between the LED structure and the photodetector structure, and the etching depth of the electrical isolation region is 0.5-0.6 μm; the p-type ohmic contact electrode region is in the shape of a long strip, and the etching depth is 0.3-0.4 μm;

[0023] In S6, the n-type ohmic contact electrode and the p-type ohmic contact electrode are deposited by sputtering. The n-type ohmic contact electrode is 20 / 80 nm Ti / Al, the p-type ohmic contact electrode is 20 / 80 nm Ni / Au, and the electrode shape is rectangular.

[0024] The present invention has at least the following beneficial effects:

[0025] 1. Compared with traditional sensors, the present invention integrates a grating structure on the surface of the n-type gallium nitride layer. When the refractive index of the medium to be detected changes, the diffraction behavior of the grating changes accordingly, thereby affecting the light field distribution and intensity in the LED, thereby enhancing the coupling effect between light and the medium to be detected. By adjusting the period, width and depth of the grating, the propagation of light can be accurately controlled to ensure that most of the incident light is effectively coupled with the detection medium, thereby reducing light energy loss and improving signal strength and detection accuracy.

[0026] 2. The present invention greatly improves the integration of the system by integrating the light emission and light detection functions of the LED into a single chip. Compared with the traditional refractive index sensor which requires a separate light source and detector, the present invention not only simplifies the system structure, but also makes the entire device more compact and lightweight, reduces the manufacturing cost and system complexity. In addition, the present invention integrates the emission and detection functions into a single chip, which enables the sensor to achieve rapid response and real-time monitoring, thus meeting the application requirements of high precision and high timeliness.

[0027] 3. The present invention adopts a vertical structure LED, removes the gallium nitride buffer layer and the undoped gallium nitride layer, and thins the n-type gallium nitride layer. The preparation process effectively reduces the scattering and absorption loss of light in these layers, further improves the light extraction efficiency, and strengthens the coupling of light with the external environment, so as to more sensitively perceive the changes in the refractive index of the external environment and improve the sensitivity of the sensor. In addition, the thinning of the n-type gallium nitride layer shortens the carrier diffusion path, reduces the parasitic resistance and power consumption, and at the same time, the thinned n-type gallium nitride layer removes unnecessary structures and reduces the overall thickness of the device, which gives it obvious advantages in the design of miniaturized and high-density integrated sensors.

[0028] Of course, any product implementing the present invention does not necessarily need to achieve all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a cross-sectional schematic diagram of the structure of the photoelectric refractive index sensor of the present invention;

[0030] Figure 2 It is a schematic structural diagram corresponding to the preparation process of the photoelectric refractive index sensor of the present invention.

[0031] Figure 3 It is a schematic diagram of the grating structure in the photoelectric refractive index sensor of the present invention.

[0032] Figure 4 Schematic diagram of comparison of light field intensity contours of the cross section (XZ plane) of the photoelectric refractive index sensor of the present invention and the flat-panel LED sensor.

[0033] Figure 5 Schematic diagram comparing the light extraction efficiency of the photoelectric refractive index sensor of the present invention and the flat-panel LED sensor.

[0034] Figure 6 It is a schematic diagram comparing the sensitivity of the photoelectric refractive index sensor of the present invention and the flat-panel LED sensor.

[0035] Figure 7 It is a schematic diagram of the spectral response curve and electroluminescence intensity curve of the photoelectric refractive index sensor of the present invention.

[0036] Figure 8 It is a schematic diagram of the corresponding curves of the LED driving current and the light detector detection current of the photoelectric refractive index sensor of the present invention.

[0037] Fig. 9 The figure is a schematic diagram of the corresponding curves of concentration and refractive index when the photoelectric refractive index sensor of the present invention is applied to measure the concentration of sucrose solution.

[0038] Fig.10The figure is a schematic diagram of the corresponding curves of concentration and light detection current when the photoelectric refractive index sensor of the present invention is applied to measure the concentration of sucrose solution.

[0039] Reference numerals:

[0040] 1. Original sapphire substrate layer; 2. GaN buffer layer; 3. Undoped GaN layer; 4. n-type GaN layer; 5. Multi-quantum well layer; 6. p-type GaN layer; 7. Silicon dioxide bonding layer; 8. Bonded sapphire substrate layer; 9. p-type ohmic contact electrode; 10. n-type ohmic contact electrode; 11. LED structure; 12. Photodetector structure. DETAILED DESCRIPTION

[0041] The following will be combined with the drawings in the embodiments of the present disclosure to clearly and completely describe the technical solutions in the embodiments of the present disclosure. Obviously, the described embodiments are only part of the embodiments of the present disclosure, not all of the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present disclosure.

[0042] Embodiment 1:

[0043] See also Figure 1 The present invention provides a technical solution: a GaN-based photoelectric refractive index sensor with an integrated guided mode resonant grating, comprising a bonded sapphire substrate layer 8, a silicon dioxide bonding layer formed above the bonded sapphire substrate layer 8, an LED structure 11 formed on a portion of the silicon dioxide bonding layer, and a photodetector structure 12 formed on another portion, and an electrical isolation region is provided between the LED structure 11 and the photodetector structure 12;

[0044] The LED structure 11 and the photodetector structure 12 both include a p-type gallium nitride layer 6 formed on a silicon dioxide bonding layer, a multi-quantum well layer 5 formed on the p-type gallium nitride layer 6, an n-type gallium nitride layer 4 formed on the multi-quantum well layer 5, and an n-type ohmic contact electrode 10 and a p-type ohmic contact electrode 9 deposited on the n-type gallium nitride layer 4 and the p-type gallium nitride layer 6, respectively;

[0045] A grating region is etched on the upper surface of the n-type gallium nitride layer 4 in the LED structure 11 to form an n-type gallium nitride grating layer.

[0046] According to the technical solution of this embodiment, the thickness of the bonded sapphire substrate layer 8 is 500-1500 μm. The sapphire substrate is mainly used to provide base support. Sapphire has good optical transparency, refractive index and wear resistance, can effectively support the propagation and refraction of light, and can also improve the sensitivity and accuracy of the sensor.

[0047] According to the technical solution of this embodiment, the thickness of the silicon dioxide bonding layer 7 is 1.5-2.5 μm. As an insulating material, the silicon dioxide bonding layer 7 plays an important role in achieving electrical isolation between the LED structure and the photodetector structure, preventing mutual interference between the LED driving current and the photodetector photocurrent. In addition, the silicon dioxide bonding layer also provides the basic conditions for the homogeneous integration of the LED and the photodetector, ensuring the stability and synergy of the system.

[0048] In actual use, the silica bonding layer 7 can change the propagation path and attenuation characteristics of light, thereby changing the resonant frequency. The appropriate thickness of the silica bonding layer 7 can adjust the refractive index and absorption coefficient to cause total or partial reflection of light at the bonding layer, thereby changing the resonant frequency. In this way, the sensor can detect changes in the refractive index more sensitively, and the silica bonding layer 7 can also improve the dynamic range, response speed, stability and other performance of the sensor. The appropriate thickness of the silica bonding layer 7 can also effectively suppress the distortion of the resonant frequency and the non-uniformity of the resonant amplitude, thereby improving the overall performance of the sensor.

[0049] Furthermore, the thickness of the p-type gallium nitride layer 6 is 0.1-0.15 μm. The introduction of the p-type gallium nitride layer 6 can enhance the reflection and absorption capabilities of visible light, which is helpful to improve the sensitivity of the sensor. Since the p-type gallium nitride layer 6 has a higher carrier mobility, it can accelerate the transmission and recombination process of photogenerated carriers in the n-type gallium nitride layer, further improving the interaction efficiency between light and matter. In addition, the presence of the p-type gallium nitride layer 6 can reduce the reflection loss and loss of the grating, thereby improving the quality factor of the grating. At the same time, by adjusting factors such as the thickness and doping concentration of the p-type gallium nitride layer 6, the grating resonant frequency can also be regulated, further improving the anti-interference ability and stability of the sensor.

[0050] According to the technical solution of this embodiment, the thickness of the multi-quantum well layer 5 is 50-100 nm. The multi-quantum well layer 5 is the main light-emitting area in the LED structure 11. It releases energy and emits it in the form of light by capturing and recombining electrons and holes. In the photodetector, the quantum well layer mainly plays a role in enhancing the photoelectric response. It generates electron-hole pairs by absorbing light of a specific wavelength. Specifically, by setting the multi-quantum well layer 5, the performance and reliability of the sensor can be further improved by controlling the absorption cross section, enhancing the grating resonance mass effect and improving the temperature stability.

[0051] Furthermore, the thickness of the n-type gallium nitride layer 4 is 0.3-0.4 μm. The n-type gallium nitride layer 4 provides negative charge carriers in the LED structure 11 and promotes current transmission to the quantum well layer, ensuring that the negative charge carriers are effectively injected and recombine with holes to generate photons; in the photodetector, the n-type layer is used to provide negative charge carriers and participate in the separation process of photogenerated carriers, and uses an external electric field to promote the flow of photogenerated electrons to the electrode, thereby generating photocurrent. Specifically, the presence of the n-type gallium nitride layer 4 can affect the propagation constant and quality factor of the grating resonance, thereby adjusting the propagation direction and intensity of the light, enhancing the sensing effect, and being used to further enhance and collect the formed photocurrent.

[0052] According to the technical solution of this embodiment, the thickness of the p-type ohmic contact electrode 9 and the n-type ohmic contact electrode 10 are both 0.1 μm. The area of ​​the ohmic contact electrode is small, which can reduce the resistance and thus improve the sensitivity. The thin electrode can also reduce the parasitic capacitance and improve the anti-interference ability.

[0053] Embodiment 2:

[0054] like Figure 2-Figure 10 This embodiment provides a method for preparing a GaN-based photoelectric refractive index sensor integrated with a guided mode resonant grating, which specifically includes the following steps:

[0055] S1. A gallium nitride buffer layer 2, an undoped gallium nitride layer 3, an n-type gallium nitride layer 4, a multi-quantum well layer 5 and a p-type gallium nitride layer 6 are sequentially grown on the original sapphire substrate layer 1 to obtain an LED epitaxial layer;

[0056] S2. Bonding the LED epitaxial p-type gallium nitride layer 6 to the bonded sapphire substrate layer 8;

[0057] S3. Laser stripping of the original sapphire substrate layer 1;

[0058] S4. Etching the bonded LED epitaxial layer device to remove the gallium nitride buffer layer 2 and the undoped gallium nitride layer 3, and further thinning the n-type gallium nitride layer 4;

[0059] S5. Patterning the grating region, the electrical isolation region, and the p-type ohmic contact electrode 9 region on the surface of the exposed n-type gallium nitride layer 4 after thinning, and etching the shape;

[0060] S6. Depositing an n-type ohmic contact electrode 10 and a p-type ohmic contact electrode 9 on the n-type gallium nitride layer 4 and the p-type gallium nitride layer 6 respectively.

[0061] According to the technical solution of this embodiment, the LED epitaxial layer in S1 is grown by a metal organic chemical vapor deposition method, and the thickness of the original sapphire substrate layer 1 is set to 500-1500 μm, the thickness of the gallium nitride buffer layer 2 is set to 0.6-0.8 μm, the thickness of the undoped gallium nitride layer 3 is set to 0.7-0.9 μm, the thickness of the n-type gallium nitride layer 4 is set to 2.5-3 μm, the thickness of the multi-quantum well layer 5 is set to 50-100 nm, and the thickness of the p-type gallium nitride layer 6 is set to 0.1-0.15 μm.

[0062] According to the technical solution of this embodiment, silicon dioxide is used as a bonding layer in S2 to bond the LED epitaxial p-type gallium nitride layer 6 to the bonded sapphire substrate layer 8; laser lift-off technology is used in S3 to remove the original sapphire substrate layer 1; inductively coupled plasma technology is used in S4 to remove the gallium nitride buffer layer 2 and the undoped gallium nitride layer 3, and further thin the n-type gallium nitride layer 4.

[0063] According to the technical solution of this embodiment, the grating region, the electrical isolation region, and the p-type ohmic contact electrode 9 region are patterned by using photolithography technology in S5. Figure 3 As shown, inductively coupled plasma technology is used for etching, wherein the grating area shape is set to be rectangular, the grating period is 2.4 μm, the grating width is 1.2 μm, and the grating etching depth is 0.2 μm; the electrical isolation area is a long strip area between the LED structure 11 and the photodetector structure 12, and the etching depth of the electrical isolation area is 0.5-0.6 μm; the shape of the p-type ohmic contact electrode 9 area is a long strip, and the etching depth is 0.3-0.4 μm. It should be noted that the etching technology includes but is not limited to the mentioned photolithography technology. When the grating period is less than the micron level, electron beam lithography or focused ion beam etching technology can also be used.

[0064] According to the technical solution of this embodiment, the n-type ohmic contact electrode 10 and the p-type ohmic contact electrode 9 in S6 are deposited by sputtering, the n-type ohmic contact electrode 10 is 20 / 80 nm Ti / Al, the p-type ohmic contact electrode 9 is 20 / 80 nm Ni / Au, and the electrode shape is rectangular.

[0065] like Figure 2 As shown, the preparation method of a GaN-based photoelectric refractive index sensor with integrated guided mode resonant grating is further described in combination with a specific embodiment:

[0066] (1) The original sapphire substrate layer 1 is placed in acetone, ethanol, and deionized water in turn, ultrasonically cleaned for 15 minutes, and blown dry with a nitrogen gun for later use;

[0067] (2) On the cleaned original sapphire substrate layer 1, a 0.6-0.8 μm gallium nitride buffer layer 2, a 0.7-0.9 μm undoped gallium nitride layer 3, a 2.5-3 μm n-type gallium nitride layer 4, a 50-100 nm multi-quantum well layer 5, and a 0.1-0.15 μm p-type gallium nitride layer 6 are sequentially grown from bottom to top by a metal organic compound chemical vapor deposition method, and the obtained samples are ultrasonically cleaned again in sequence, dried with nitrogen gas, and set aside;

[0068] (3) Depositing a 1.5-2.5 μm silicon dioxide layer on the p-type gallium nitride layer 6 by plasma chemical vapor deposition, selecting a suitable silicon source gas, and setting a suitable silicon source gas flow rate, oxygen flow rate, pressure, temperature, etc.; Bonding the epitaxial layer to the bonded sapphire substrate layer 8 by a hot pressing process, adjusting a suitable temperature to promote the adhesion and fluidity of the silicon dioxide layer, applying a high pressure to ensure that the silicon dioxide layer completely fills the interface and provides a stable bond, and annealing to improve the structural quality of the silicon dioxide film and enhance the bonding strength between the LED epitaxial layer and the bonded sapphire substrate layer 8; Cleaning and drying for later use;

[0069] (4) using a 365 nm ultraviolet laser to irradiate the contact interface between the epitaxial layer and the original sapphire substrate layer 1 to separate the epitaxial layer from the original sapphire substrate layer 1, and then cleaning and drying the epitaxial layer after peeling for later use;

[0070] (5) Using inductively coupled plasma etching technology to remove the gallium nitride buffer layer 2 and the undoped gallium nitride layer 3, and further thinning the n-type gallium nitride layer 4 to an overall epitaxial layer thickness of 0.5-0.6 μm, using a suitable etching gas, setting a suitable gas flow, chamber pressure, RF power, and etching power, monitoring the etching process until the gallium nitride buffer layer 2 and the undoped gallium nitride layer 3 are completely removed, maintaining the gas flow and chamber pressure unchanged, reducing the RF power and etching power to control the etching rate and time, so that the thickness of the n-type gallium nitride layer 4 is thinned to the expected value, and then cleaning and drying for standby use;

[0071] (6) Using photolithography technology, pattern the grating area, electrical isolation area, and p-type ohmic contact electrode 9 area on the exposed n-type gallium nitride layer 4. The grating shape is rectangular, the grating period is 2.4 μm, the grating width is 1.2 μm, and the grating etching depth is 0.2 μm; the electrical isolation area is in the shape of a long strip, and the etching depth is 0.5-0.6 μm; the p-type ohmic contact electrode 9 area is in the shape of a long strip, and the etching depth is 0.3-0.4 μm; Use a spin coating process to evenly coat a layer of photoresist on the surface of the n-type gallium nitride layer 4. The thickness of the photoresist should be greater than the maximum etching depth, and set a suitable spin coating speed and baking temperature; Prepare a mask with different transmittances. As the etching depth increases, the transmittance should be greater; Use an ultraviolet exposure system, adjust the exposure dose according to the characteristics of the photoresist to control the exposure depth, and control the light intensity to ensure the effect is accurate; Select a developer of appropriate concentration, and control the development time according to the thickness of the photoresist used and the exposure dose. Use appropriate etching gas, set appropriate gas flow, chamber pressure, RF power, and etching power; first etch all grating areas, control the etching time to reach a depth of 0.2 μm; then, etch the p-type ohmic contact electrode 9 area, appropriately adjust the etching time or bias power to ensure that the depth reaches 0.3-0.4 μm; finally, etch the electrical isolation area, monitor the time and depth, and ensure that the final area reaches the target depth. After etching, use an appropriate solvent to remove the photoresist residue; clean and blow dry for later use.

[0072] (7) Spin-coat a layer of photoresist on the device surface using a spin coating process, set a suitable spin coating speed and baking temperature; prepare a mask that defines the shape and position of the LED electrode area, and use an ultraviolet exposure system to expose it, and then perform a development process; use magnetron sputtering technology to deposit p-type ohmic contact electrode 9 and n-type ohmic contact electrode 10, select suitable target materials and working gases, set suitable gas flow, sputtering power, and chamber pressure, and adjust the sputtering time to make the Ni film thickness 20 nm. Similarly, adjust the process parameters and continue to deposit 80 nm Au to obtain p-type ohmic contact electrode 9, and deposit 20 nm Ti and 80 nm Al to obtain n-type ohmic contact electrode 10; immerse the device in a special solvent to remove the photoresist. The electrode material on the area not covered by the photoresist will be retained, thereby forming an electrode structure; clean and blow dry.

[0073] Figure 4 Schematic diagram of comparison of light field intensity contours of the cross section (XZ plane) of the photoelectric refractive index sensor of this embodiment and the traditional flat-panel LED sensor; Figure 5 Schematic diagram comparing the light extraction efficiency of the photoelectric refractive index sensor and the flat-panel LED sensor of this embodiment.

[0074] In summary, Figure 6This is a schematic diagram showing the sensitivity comparison between the photoelectric refractive index sensor and the flat-panel LED sensor of this embodiment; Figure 7 Schematic diagram of the spectral response curve and electroluminescence intensity curve of the photoelectric refractive index sensor of this embodiment; Figure 8 Schematic diagram of corresponding curves of LED driving current and light detector detection current of the photoelectric refractive index sensor of this embodiment; Fig. 9 It is a schematic diagram of the corresponding curve between concentration and refractive index of the photoelectric refractive index sensor of this embodiment in the application of sucrose solution concentration measurement; Fig.10 Schematic diagram of the corresponding curves of concentration and light detection current of the photoelectric refractive index sensor of this embodiment in the application of sucrose solution concentration measurement;

[0075] It can be seen that in this embodiment, a grating structure is integrated on the surface of the n-type gallium nitride layer 4. When the refractive index of the medium to be detected changes, the diffraction behavior of the grating changes accordingly, thereby affecting the light field distribution and intensity in the LED, thereby enhancing the coupling effect between the light and the medium to be detected. By adjusting the period, width and depth of the grating, the propagation of light can be accurately controlled to ensure that most of the incident light is effectively coupled with the detection medium, thereby reducing light energy loss and improving signal strength and detection accuracy. In addition, the present invention greatly improves the integration of the system by integrating the light emission of the LED structure 11 and the light detector structure 12 in a single chip.

[0076] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0077] For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances. When an element is referred to as being "assembled on", "installed on", "fixed on" or "set on" another element, it can be directly on the other element or there can also be a centered element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be a centered element at the same time. The terms "vertical", "horizontal", "up", "down", "left", "right" and similar expressions used herein are only for illustrative purposes and are not intended to be the only implementation method.

[0078] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

[0079] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present disclosure. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

Claims

1. A GaN-based photoelectric refractive index sensor with an integrated guided mode resonant grating, comprising a bonded sapphire substrate layer (8), characterized in that: A silicon dioxide bonding layer (7) is formed above the bonded sapphire substrate layer (8), an LED structure (11) and a light detector structure (12) are respectively formed above the silicon dioxide bonding layer (7), an electrical isolation region is provided between the LED structure (11) and the light detector structure (12), and the LED structure (11) and the light detector structure (12) are homogeneously integrated; The LED structure (11) and the photodetector structure (12) both comprise a p-type gallium nitride layer (6) formed on a silicon dioxide bonding layer (7), a multi-quantum well layer (5) formed on the p-type gallium nitride layer (6), an n-type gallium nitride layer (4) formed on the multi-quantum well layer (5), and an n-type ohmic contact electrode (10) and a p-type ohmic contact electrode (9) deposited on the n-type gallium nitride layer (4) and the p-type gallium nitride layer (6), respectively; A grating region is etched on the upper surface of the n-type gallium nitride layer (4) in the LED structure (11) to form an n-type gallium nitride grating layer.

2. The GaN-based photoelectric refractive index sensor with integrated guided mode resonant grating according to claim 1, characterized in that: The thickness of the bonded sapphire substrate layer (8) is set to 500-1500 μm.

3. The GaN-based photoelectric refractive index sensor with integrated guided mode resonant grating according to claim 2, characterized in that: The silicon dioxide bonding layer (7) has a thickness of 1.5-2.5 μm; the p-type gallium nitride layer (6) has a thickness of 0.1-0.15 μm.

4. The GaN-based photoelectric refractive index sensor integrated with a guided mode resonant grating according to claim 2, characterized in that: The multi-quantum well layer (5) has a thickness of 50-100 nm; the n-type gallium nitride layer (4) has a thickness of 0.3-0.4 μm.

5. The GaN-based photoelectric refractive index sensor integrated with a guided mode resonant grating according to claim 4, characterized in that: The thickness of the p-type ohmic contact electrode (9) and the n-type ohmic contact electrode (10) are both 0.1 μm.

6. A method for preparing a GaN-based photoelectric refractive index sensor integrated with a guided mode resonant grating, for preparing the GaN-based photoelectric refractive index sensor integrated with a guided mode resonant grating according to any one of claims 1 to 5, characterized in that: The specific steps include: S1. A gallium nitride buffer layer (2), an undoped gallium nitride layer (3), an n-type gallium nitride layer (4), a multi-quantum well layer (5) and a p-type gallium nitride layer (6) are sequentially grown on an original sapphire substrate layer (1) to obtain an LED epitaxial layer; S2. bonding the LED epitaxial p-type gallium nitride layer (6) to the bonded sapphire substrate layer (8); S3. Laser stripping of the original sapphire substrate layer (1); S4. Etching the bonded LED epitaxial layer device to remove the gallium nitride buffer layer (2) and the undoped gallium nitride layer (3), and further thinning the n-type gallium nitride layer (4); S5. patterning a grating region, an electrical isolation region, and a p-type ohmic contact electrode region on the surface of the n-type gallium nitride layer (4) exposed after thinning, and etching the shape; S6. Depositing an n-type ohmic contact electrode (10) and a p-type ohmic contact electrode (9) on the n-type gallium nitride layer (4) and the p-type gallium nitride layer (6), respectively.

7. The method for preparing a GaN-based photoelectric refractive index sensor integrated with a guided mode resonant grating according to claim 6, characterized in that: The LED epitaxial layer in S1 is grown by metal organic chemical vapor deposition, and the thickness of the original sapphire substrate layer (1) is set to 500-1500 μm, the thickness of the gallium nitride buffer layer (2) is set to 0.6-0.8 μm, the thickness of the undoped gallium nitride layer (3) is set to 0.7-0.9 μm, the thickness of the n-type gallium nitride layer (4) is set to 2.5-3 μm, the thickness of the multi-quantum well layer (5) is set to 50-100 nm, and the thickness of the p-type gallium nitride layer (6) is set to 0.1-0.15 μm.

8. The method for preparing a GaN-based photoelectric refractive index sensor integrated with a guided mode resonant grating according to claim 7, characterized in that: In S2, silicon dioxide is used as a bonding layer to bond the p-type gallium nitride layer (6) of the LED epitaxial layer to the bonding sapphire substrate layer (8).

9. The method for preparing a GaN-based photoelectric refractive index sensor integrated with a guided mode resonant grating according to claim 8, characterized in that: In the S4, the gallium nitride buffer layer (2) and the undoped gallium nitride layer (3) are removed by using an inductively coupled plasma technique, and the n-type gallium nitride layer (4) is further thinned.

10. The method for preparing a GaN-based photoelectric refractive index sensor integrated with a guided mode resonant grating according to claim 9, characterized in that: In the S5, the grating region, the electrical isolation region, and the p-type ohmic contact electrode region are patterned respectively by using photolithography technology, and etching is performed by using inductively coupled plasma technology, wherein the grating region is set to be rectangular in shape, the grating period is 2.4 μm, the grating width is 1.2 μm, and the grating etching depth is 0.2 μm; the electrical isolation region is a long strip region between the LED structure (11) and the photodetector structure (12), and the etching depth of the electrical isolation region is 0.5-0.6 μm; the p-type ohmic contact electrode region is in the shape of a long strip, and the etching depth is 0.3-0.4 μm; In S6, the n-type ohmic contact electrode (10) and the p-type ohmic contact electrode (9) are deposited by sputtering. The n-type ohmic contact electrode (10) is 20 / 80nm Ti / Al, and the p-type ohmic contact electrode (9) is 20 / 80nm Ni / Au. The electrode shape is rectangular.

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