InGaN difference frequency accelerometer with quantum limited stark effect and preparation method thereof

Abstract

A beam laser diode takes a silicon-based nitride epitaxial wafer as a carrier and comprises a silicon substrate layer, an aluminum nitride buffer layer, an n-type gallium nitride layer, a quantum well layer, a p-type gallium nitride layer and a SiO2 layer which are sequentially arranged from bottom to top, the p-type electrode is arranged on the p-type gallium nitride layer, and the n-type electrode is arranged on the edge of the n-type gallium nitride layer. A nitride material on a silicon substrate is used for preparing a micro-beam stress sensitive area LD by utilizing photoetching and ICP (Inductively Coupled Plasma) etching processes for emitting light, and after electrification, the laser LD is obtained in the stress sensitive area of the beam. Under the power-on condition, before and after acceleration loading, due to the fact that quantum limits the stark effect, the frequency wavelength of laser changes, and the magnitude of the acceleration can be sensed through difference frequency.

Description

Technical Field

[0001] The present invention belongs to the fields of electronics and optomechanics, and particularly relates to an indium gallium nitrogen difference frequency accelerometer with quantum confined Stark effect and a preparation method thereof. Background Art

[0002] Background: Accelerometers are important components of inertial navigation systems. Optical accelerometers are a new type of accelerometer, offering advantages such as miniaturization, low cost, high sensitivity, and resistance to electromagnetic interference and shock. However, current optical accelerometers are made of passive materials such as Si and SiN. The sensing components themselves do not emit light, requiring the integration of an external light source, which limits high-density optoelectronic integration. The existing technologies have the following problems: First, the design of the beam-plus-mass of the overall accelerometer must take into account the influence of the beam length on the luminescence, the realization of the quantum confined Stark effect, and the feasibility of realization in the actual processing process; 2. When wiring the device, consider that the wiring position cannot affect the normal operation of the device; 3. The influence of device slit width and slit spacing on device sensitivity. Summary of the Invention

[0003] To achieve the above-mentioned purpose, the present invention discloses an InGaN difference frequency accelerometer with quantum confined Stark effect, which uses a silicon-based nitride epitaxial wafer as a carrier and comprises a silicon substrate layer, an aluminum nitride buffer layer, an n-type GaN layer, a quantum well layer, a p-type GaN layer, and a SiO2 layer arranged in sequence from bottom to top, a p-type electrode arranged on the p-type GaN layer, and an n-type electrode arranged at the edge of the n-type GaN layer. The silicon substrate layer (1) is completely etched away around the disc-shaped mass block and the cantilever beam, so that it presents the shape of the beam and the mass block, and the n-type electrode is arranged on the exposed n-type GaN layer.

[0004] Furthermore, the accelerometer of the present invention includes a cantilever beam with a mass block at the edge.

[0005] Furthermore, in the accelerometer of the present invention, when powered on, the frequency wavelength of the laser will change due to the quantum confined Stark effect before and after the acceleration load, and the magnitude of the acceleration can be sensed through the difference frequency.

[0006] The invention uses optical lithography and ICP etching technology to prepare a cantilever beam accelerometer. The rationally designed process steps include etching the shape of the template to obtain a cantilever beam supported by a single-side column and having smooth edges and a disk-shaped mass block.

[0007] The method of the present invention for preparing an InGaN quantum well optomechanical microcavity accelerometer based on the quantum confined Stark effect comprises the following steps: The first step is to spin-coat a photoresist on the p-type gallium nitride (5) of the silicon-based gallium nitride epitaxial wafer, and then use optical lithography technology to define a pattern consisting of a rectangular connecting cantilever beam and a disk on the spin-coated photoresist layer; Step 2: Electron beam evaporation technology is used to evaporate 300-500nm thick metal nickel on the surface of the defined pattern. The epitaxial wafer is then placed in an acetone solution for ultrasonic treatment. The epitaxial wafer is then placed in ultrapure water for cleaning, and then placed in anhydrous ethanol and ultrapure water for cleaning in sequence. Finally, the residual photoresist is removed; a nickel mask pattern is obtained.

[0008] Step 3: Using ICP etching technology to etch 2 μm-2.5 μm down to the middle of the n-type gallium nitride layer (3), thereby transferring the pattern defined in the first step to the n-type gallium nitride layer (3) of the silicon-based nitride epitaxial wafer, and obtaining the high-low shape structure of the accelerometer and the prototype of the cantilever beam and the mass block; Step 4: Use dilute nitric acid to remove metallic nickel, then immediately rinse in ultrapure water; Step 5: Evaporate a SiO2 layer on the exposed p-type GaN layer of the accelerometer, and do not evaporate the SiO2 layer in two areas 1 / 4 of the length of the cantilever beam at both ends.

[0009] Step 6: Spin-coat photoresist on the accelerometer cantilever beam and disk mass block to ensure that the beam structure and mass block will not be etched away during the etching process, thus playing a protective role. Step 7: Electron beam evaporation is used to deposit 300-500nm thick nickel on the surface of the defined pattern. The epitaxial wafer is then ultrasonically cleaned in acetone solution, followed by cleaning in anhydrous ethanol and ultrapure water. Finally, the remaining photoresist is removed to obtain a nickel mask pattern. Step 8: Use ICP etching technology to etch the pattern downward until the middle is hollowed out, and finally clean the remaining photoresist; Step 9: using electron beam evaporation technology to evaporate a positive electrode on the upper surface of the p-type region electrode pattern, and to evaporate a negative electrode on the upper surface of the n-type region electrode pattern, so that the p-type gallium nitride layer (5) and the n-type gallium nitride layer (3) are respectively plated with positive and negative electrodes, and finally removing the residual photoresist to obtain the p-type region electrode (7) and the n-type region electrode (8); Step 10: Use a mixture of hydrofluoric acid and dilute nitric acid to wet-etch silicon until the bottom of the silicon substrate layer (1) to form a cantilever beam plus mass block structure.

[0010] Furthermore, in the method of the present invention, both the positive electrode and the negative electrode are vapor-deposited Au / Ni.

[0011] Compared to existing technologies, the present invention offers the following advantages: it utilizes a single epitaxial wafer, eliminating the need for growing different materials. This results in a simple structure, compact size, and easy integration. Compared to existing optical accelerometers fabricated from passive materials such as Si and SiN, it offers advantages in high resolution, high integration, and ultra-high sensitivity. Furthermore, its difference frequency transmission characteristics offer exceptionally high immunity to interference. This invention provides a path to developing high-resolution, high-sensitivity, and low-mode-volume optomechanical sensors with dual luminescence and sensing capabilities. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 Side view of the InGaN difference-frequency accelerometer based on the quantum-confined Stark effect. Figure 2 A top view of the InGaN difference-frequency accelerometer based on the quantum-confined Stark effect. Figure 3 Process flow chart for an InGaN difference-frequency accelerometer based on the quantum-confined Stark effect.

[0013] The figure includes: silicon substrate layer 1, aluminum nitride buffer layer 2, n-type gallium nitride layer 3, quantum well layer 4, p-type gallium nitride layer 5, SiO2 layer 6, p-type electrode 7, and n-type electrode 8. DETAILED DESCRIPTION

[0014] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0015] Example: Figures 1 to 3 As shown: The present invention uses a silicon-based nitride epitaxial wafer as a substrate. From bottom to top, it comprises a silicon substrate layer, an aluminum nitride buffer layer, an n-type gallium nitride layer, a quantum well layer, a p-type gallium nitride layer, a SiO2 layer, a p-type electrode disposed on the p-type gallium nitride layer, and an n-type electrode disposed at the edge of the n-type gallium nitride layer. The silicon substrate layer is completely etched away, leaving only the cantilever beam and mass. The n-type electrode is disposed on the exposed n-type gallium nitride layer. The accelerometer features a cantilever beam with a mass. The beam is 20 mm wide. The p-type electrode, which covers the p-type gallium nitride layer, consists of a beam and a square electrode. The beam is 100 mm long and 10 mm wide, with a disk diameter of 50 mm. The electrode is 120 nm thick.

[0016] The method for preparing the indium gallium nitride quantum well optomechanical microcavity accelerometer based on the quantum confined Stark effect of the present invention comprises the following steps: Step 1: The purchased commercial silicon substrate gallium nitride epitaxial wafer was ultrasonically cleaned with acetone, anhydrous ethanol and ultrapure water in sequence (5 min), and then blown dry with nitrogen; the photoresist AZ-5214 was spin-coated on the front side of the epitaxial wafer (the upper surface of the p-type nitride layer (5)) at a speed of 4000 rpm using a coating machine, and the spin coating time was 40 seconds (the photoresist thickness was 1.5 μm).

[0017] Optical lithography technology is used to define a rectangular pattern connecting the cantilever beam and the disk on the spin-coated photoresist layer. The lithography machine model is MA6.

[0018] Step 2: Use electron beam evaporation technology to evaporate 700 nm of metallic nickel on the surface of the p-type gallium nitride layer, and then remove the remaining photoresist.

[0019] Step 3: Using ICP etching technology to etch the nitride layer down to the n-type gallium nitride layer (3), thereby transferring the pattern defined in the first step to the n-type gallium nitride layer (3) of the silicon-based nitride epitaxial wafer, and obtaining the high-low shape structure of the accelerometer and the prototype of the cantilever beam and the mass block; The epitaxial wafer was then placed in a dilute nitric acid solution to remove residual nickel, and then rinsed in anhydrous ethanol and ultrapure water. Step 4: Evaporate a SiO2 layer on the exposed p-type GaN layer of the accelerometer, and do not evaporate the SiO2 layer in two areas 1 / 4 of the length of the cantilever beam at both ends.

[0020] Step 5: Use a spin coater to spin-coat photoresist AZ-5214 on the front side of the epitaxial wafer (the surface of the cantilever beam structure and the surface of the disk mass block) at a speed of 4000 rpm for 40 seconds (the photoresist thickness is 1.5 μm).

[0021] Step 6: Using electron beam evaporation technology to evaporate 700nm of metal nickel on the surface of the n-type gallium nitride layer (3), and then remove the residual photoresist.

[0022] Step 7: Using ICP etching technology, the pattern is etched downward from the n-type gallium nitride layer (3) to the surface of the Si layer (1), thereby transferring the pattern to the Si layer (1); The epitaxial wafer was then placed in a dilute nitric acid solution to remove residual nickel, and then rinsed in anhydrous ethanol and ultrapure water. Step 8: Use a mixture of hydrofluoric acid and dilute nitric acid to wet-etch the silicon until the bottom of the silicon substrate layer (1) is reached, leaving the cantilever beam structure and the disk mass block fully suspended. The etching gas is a mixture of HF and HNO3, and the etching time is 1 minute. Finally, remove the remaining photoresist.

[0023] It should be noted that the above content merely illustrates the technical idea of ​​the present invention and cannot be used to limit the scope of protection of the present invention. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications all fall within the scope of protection of the claims of the present invention.

Claims

1. A quantum confined Stark effect InGaN difference frequency accelerometer, characterized in that: The accelerometer uses a silicon-based nitride epitaxial wafer as a carrier, and includes a silicon substrate layer (1), an aluminum nitride buffer layer (2), an n-type gallium nitride layer (3), a quantum well layer (4), a p-type gallium nitride layer (5), and a SiO2 layer (6) arranged in sequence from bottom to top; a p-type electrode (7) arranged on the p-type gallium nitride layer (5); and an n-type electrode (8) arranged at the edge of the n-type gallium nitride layer (3). The silicon substrate layer (1) is completely etched away at the cantilever beam and the mass block, so that the cantilever beam and the mass block are fully suspended. A SiO2 layer (6) is plated outside two regions 1 / 4 of the length of the cantilever beam at both ends, and a p-type electrode (7) is deposited on the upper surface of the SiO2 layer (6) on the middle beam and on the disk mass block.

2. The quantum confined Stark effect InGaN difference frequency accelerometer according to claim 1, characterized in that: The n-type electrode (8) is arranged at the edge of the n-type gallium nitride layer (3) and is a square electrode, and the p-type electrode (7) is arranged on the p-type gallium nitride layer (5).

3. The quantum confined Stark effect InGaN difference frequency accelerometer according to claim 2, characterized in that: When power is turned on, only two areas on the cantilever beam that are 1 / 4 of the length away from the two ends will emit laser LD.

4. The quantum confined Stark effect InGaN difference frequency accelerometer according to claim 3, characterized in that: The cantilever beam is equipped with a mass block, and two regions on the cantilever, one-quarter the length from each end, are not deposited with SiO2. Before and after the acceleration load, the frequency wavelength of the laser changes due to the quantum-confined Stark effect, and the magnitude of the acceleration is detected through the difference frequency.

5. A method for preparing the InGaN difference frequency accelerometer with quantum confined Stark effect according to any one of claims 1 to 4, characterized in that: The following steps are involved: Step 1: Spin-coat a photoresist on the upper surface of the p-type gallium nitride (5) of the silicon-based gallium nitride epitaxial wafer, and then use optical lithography technology to define a rectangular connecting cantilever beam and a disk pattern on the spin-coated photoresist layer; Step 2: Electron beam evaporation is used to deposit 300-500 nm thick nickel on the surface of the defined pattern. The epitaxial wafer is then ultrasonically treated in acetone solution. The epitaxial wafer is then rinsed in ultrapure water, followed by anhydrous ethanol and ultrapure water, and the remaining photoresist is removed to obtain a nickel mask pattern. Step 3: Using ICP etching technology to etch down 2 mm to 2.5 mm to the n-type gallium nitride layer (3), thereby transferring the pattern defined in the first step to the n-type gallium nitride layer (3) of the silicon-based nitride epitaxial wafer, and obtaining the high-low shape structure of the accelerometer and the prototype of the cantilever beam and the mass block; Step 4: Remove metallic nickel with dilute nitric acid, and then immediately rinse in ultrapure water; Step 5: Vapor-deposit a SiO2 layer on the middle beam and the disk mass of the accelerometer, while not vapor-depositing the SiO2 layer on two areas of the cantilever beam that are 1 / 4 of the length away from the two ends. Step 6: Spin-coat photoresist on the beam and disc-shaped mass of the accelerometer to ensure that the beam structure and mass are not etched away during the etching process; Step 7: Electron beam evaporation is used to deposit 300-500 nm thick nickel on the surface of the defined pattern. The epitaxial wafer is then ultrasonically cleaned in acetone solution, followed by cleaning in anhydrous ethanol and ultrapure water. Finally, the remaining photoresist is removed to obtain a nickel mask pattern. Step eight, using ICP etching technology, etching the pattern downward until the middle is hollowed out, and finally cleaning the remaining photoresist; Step nine, using electron beam evaporation technology to evaporate a positive electrode on the upper surface of the p-type region electrode pattern, and to evaporate a negative electrode on the upper surface of the n-type region electrode pattern, so that the p-type gallium nitride layer (5) and the n-type gallium nitride layer (3) are respectively plated with positive and negative electrodes, and finally, the residual photoresist is removed to obtain the p-type region electrode (7) and the n-type region electrode (8); Step 10: Wet-etch silicon using a mixture of hydrofluoric acid and dilute nitric acid until the bottom of the silicon substrate layer (1), so that silicon columns and a bottom surface supporting the structure are formed in the silicon substrate layer (1), forming a suspended beam structure.

6. The method for preparing the quantum confined Stark effect InGaN difference frequency accelerometer according to claim 5, characterized in that: The positive electrode and the negative electrode are both evaporated Au / Ni.

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