Quantum limited stark effect based optomechanical microcavity accelerometer and preparation method thereof

Abstract

The application discloses an indium gallium nitride quantum well optomechanical microcavity accelerometer based on quantum limited Stark effect, a beam laser diode takes a silicon-based nitride epitaxial wafer as a carrier, and comprises a silicon substrate layer, an aluminum nitride layer, a u-shaped gallium nitride 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, a p-type electrode arranged on the p-type gallium nitride layer and an n-type electrode arranged at the edge of the n-type gallium nitride layer. The nitride material on the silicon substrate utilizes a photoetching and ICP etching process to prepare a micro-beam stress sensitive area LD light emitting, and laser LD is obtained at the stress sensitive area of the beam after electrification. Under the electrification condition, the frequency wavelength of the laser changes before and after acceleration load due to the quantum limited Stark effect, and the acceleration size can be perceived through the difference frequency.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of quantum electronics and the field of optoelectromechanical technology, and particularly relates to an optoelectromechanical microcavity accelerometer based on quantum confined Stark effect and a preparation method thereof. BACKGROUND

[0002] The velocity meter is an important component of the inertial navigation system, and the optical accelerometer is a new type of accelerometer, which has the advantages of miniaturization, low cost, high sensitivity, anti-electromagnetic interference and impact resistance. However, the current optical accelerometer adopts SI, SIN and other passive materials, the sensing component itself does not emit light, and an external light source needs to be integrated, which limits high-density photoelectric integration. The following technical problems currently exist:

[0003] The design of the whole accelerometer with one beam and mass block needs to consider the influence of the length of the beam on light emission, the influence of the mass block, the realization of the quantum confined Stark effect, and the possibility of realization in the actual processing process.

[0004] The wiring of the device needs to consider that the position of the wiring cannot affect the normal work of the device. SUMMARY

[0005] To solve the above problems, the application discloses an optoelectromechanical microcavity accelerometer based on quantum confined Stark effect. Under the condition of power supply, the frequency and wavelength of laser will change before and after the acceleration load due to the quantum confined Stark effect, and the size of the acceleration can be perceived through the difference frequency.

[0006] The application is an optoelectromechanical microcavity accelerometer based on quantum confined Stark effect, which takes a silicon-based nitride epitaxial wafer as a carrier and includes a silicon substrate layer, an aluminum nitride layer, a u-shaped gallium nitride layer, an n-type gallium nitride layer, a quantum well layer, a p-type gallium nitride layer, a SiO2 layer, a p-type electrode arranged on the p-type gallium nitride layer, and an n-type electrode arranged at the edge of the n-type gallium nitride layer. The silicon substrate layer is etched from top to bottom, only the square plate and the part below the beam are reserved, so that the shape of the beam and the square plate is exposed, and the n-type electrode is arranged on the upper side of the exposed n-type gallium nitride layer.

[0007] Further, the accelerometer contains a beam with a mass block in the middle.

[0008] Further, in the accelerometer, under the condition of power supply, the frequency and wavelength of laser will change before and after the acceleration load due to the quantum confined Stark effect, and the size of the acceleration can be perceived through the difference frequency.

[0009] The application utilizes optical lithography and ICP etching process to prepare an accelerometer with a beam. A reasonable process step is designed, including etching the shape of a template, to obtain a single beam supported by a column and with smooth edges.

[0010] The application discloses a preparation method of an indium gallium nitride quantum well photo-mechanical-electrical microcavity accelerometer based on quantum limited Stark effect.

[0011] Step 1: spin coating photoresist on the p-type gallium nitride upper surface of a silicon-based gallium nitride epitaxial wafer, and then defining a pattern of two square plates connected by a beam on the spin-coated photoresist layer by using optical lithography technology;

[0012] Step 2: evaporating 300-500 nm thick metal nickel on the defined pattern by using electron beam evaporation technology, then placing the epitaxial wafer into acetone solution for ultrasonic treatment, then placing the epitaxial wafer into ultrapure water for cleaning, then placing the epitaxial wafer into anhydrous ethanol and ultrapure water for cleaning in sequence, and finally removing residual photoresist, to obtain a mask pattern of nickel.

[0013] Step 3: etching down 2-2.5 mu m to the middle of the n-type gallium nitride layer by using ICP etching technology, so as to transfer the pattern defined in the first step to the n-type gallium nitride layer of the silicon-based nitride epitaxial wafer, to obtain the structure of the beam of the accelerometer;

[0014] Step 4: removing the metal nickel by dilute nitric acid, and then immediately cleaning in ultrapure water;

[0015] Step 5: evaporating a SiO2 layer on the middle beam of the accelerometer, but not evaporating the SiO2 layer on the small square at one fourth of the beam.

[0016] Step 6: spin coating photoresist on the beam and the surrounding surface of the accelerometer, to ensure that the beam structure and the periphery are not etched in the etching process, and to play a protective role;

[0017] Step 7: evaporating 300-500 nm thick metal nickel on the defined pattern by using electron beam evaporation technology, then placing the epitaxial wafer into acetone solution for ultrasonic cleaning, then placing the epitaxial wafer into anhydrous ethanol and ultrapure water for cleaning in sequence, and finally removing residual photoresist, to obtain a mask pattern of nickel.

[0018] Step 8: etching the pattern down to hollow the middle by using ICP etching technology, and finally removing residual photoresist;

[0019] Step 9: evaporating a positive electrode on the p-type electrode pattern by using electron beam evaporation technology, and evaporating a negative electrode on the n-type electrode pattern, so that the p-type gallium nitride layer and the n-type gallium nitride layer are respectively plated with positive and negative electrodes, and finally removing residual photoresist, to obtain the p-type electrode and the n-type electrode.

[0020] Step 10: Wet etching of silicon is performed using a mixture of hydrofluoric acid and dilute nitric acid until the bottom of the silicon substrate is reached, forming silicon pillars and a bottom surface that support this structure in the silicon substrate, thus creating a suspended beam structure.

[0021] Furthermore, both the positive and negative electrodes are vapor-deposited Au / Ni.

[0022] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0023] 1. This invention uses a single epitaxial wafer, eliminating the need to grow different materials, resulting in a simple structure, small size, and easy integration. Compared to current optical accelerometers made with passive materials such as Si and SiN, it offers advantages such as miniaturization, low cost, high sensitivity, resistance to electromagnetic interference, and shock resistance. 2. This project designs a single laser on an electrically pumped InGaN quantum well beam to construct an opto-mechatronic microcavity accelerometer. Under acceleration load, the piezoelectric polarization field caused by the mechanical strain of the beam induces the quantum confinement Stark effect in the quantum well, causing a change in the laser frequency wavelength of the electrically pumped beam laser. The magnitude of acceleration is sensed through this frequency wavelength change. Attached Figure Description

[0024] Figure 1 Side view of an indium gallium nitride quantum well opto-electro-mechanical microcavity accelerometer based on the quantum-confined Stark effect.

[0025] Figure 2 Top view of an indium gallium nitride quantum well opto-electro-mechanical microcavity accelerometer based on the quantum confinement Stark effect.

[0026] Figure 3 Flowchart of the fabrication process for an indium gallium nitride quantum well opto-electro-mechanical microcavity accelerometer based on the quantum confinement Stark effect.

[0027] Figure 4 Stress distribution on the surface of the accelerometer under net gravitational field.

[0028] Figure 5 Displacement and deformation of the intermediate beam of the accelerometer under net gravitational field.

[0029] The figure shows: 1-silicon substrate, 2-aluminum nitride layer, 3-u-type gallium nitride, 4-n-type gallium nitride layer, 5-quantum well layer, 6-p-type gallium nitride layer, 7-SiO2 layer, 8-p-type electrode, 9-n-type electrode, 10-stress-sensitive region, 11-beam. Detailed Implementation

[0030] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. It should be noted that the terms "front," "rear," "left," "right," "up," and "down" used in the following description refer to directions in the accompanying drawings, and the terms "inner" and "outer" refer to directions toward or away from the geometric center of a specific component, respectively.

[0031] Example 1: As Figures 1-2 As shown in this embodiment, an indium gallium nitride quantum well opto-electro-mechanical microcavity accelerometer based on the quantum confinement Stark effect is described. The accelerometer uses a silicon-based nitride epitaxial wafer as a carrier and includes, from bottom to top, a silicon substrate layer 1, an aluminum nitride layer 2, a u-type gallium nitride layer 3, an n-type gallium nitride layer 4, a quantum well layer 5, a p-type gallium nitride layer 6, and a SiO2 layer 7. A p-type electrode 8 is disposed on the p-type gallium nitride layer 6, and an n-type electrode 9 is disposed at the edge of the n-type gallium nitride layer 4. A beam 11 is retained in the middle of the silicon substrate layer 1. When energized, the stress-sensitive area 10 of the beam emits a laser LD.

[0032] This accelerometer is a rectangular ring connected in the middle by a beam with a mass block in the middle. The two square blocks on both sides of the beam are hollowed out. The p electrode 8 consists of a beam and a square electrode, with a mass block in the middle of the beam. The stress-sensitive area 10 of the beam is not coated with a SiO2 layer, while the rest is coated with a SiO2 layer 7. The p-type electrode 8 is deposited on the upper surface of the SiO2 layer 7 on the middle beam. The n-type electrode 9 is deposited on the n-type gallium nitride layer 4 on the other side and is a square electrode.

[0033] The stress-sensitive zone 10 occupies one-quarter of the length of beam 11; when beam 11 is energized, only the stress-sensitive zone 10 will emit laser LD.

[0034] This embodiment uses a silicon-based nitride epitaxial wafer as a carrier. From bottom to top, the layers are: a silicon substrate, an aluminum nitride layer, a u-type gallium nitride layer, an n-type gallium nitride layer, a quantum hydrazine layer, a p-type gallium nitride layer, a SiO2 layer, a p-type electrode disposed on the p-type gallium nitride layer, and a square n-type electrode disposed at the edge of the n-type gallium nitride layer. The entire silicon substrate is etched away, leaving only the central beam and the area below the perimeter of the accelerometer. The n-type electrodes are disposed on the exposed sides of the n-type gallium nitride layer. The accelerometer features a beam with a mass block located between two square disks. The beam width is 20 μm. The p-type electrode, covering the p-type gallium nitride layer, consists of a beam 300 μm long and a square electrode 30 μm long and 20 μm wide. The electrode thickness is 120 nm.

[0035] like Figure 3As shown in this embodiment, the method for fabricating an indium gallium nitride quantum well opto-electro-mechanical microcavity accelerometer based on the quantum confinement Stark effect is as follows:

[0036] Step 1: Clean the purchased commercial silicon substrate gallium nitride epitaxial wafer with acetone, anhydrous ethanol and ultrapure water by ultrasonication (5 min) in sequence, and then dry it with nitrogen gas; use a spin coater to spin coat the photoresist AZ-5214 on the front side of the epitaxial wafer (the upper surface of the p-type nitride layer 5) at a speed of 4000 rpm for 40 seconds (photoresist thickness is 1.5 micrometers).

[0037] Optical lithography was used to define a pattern of two squares connected to a beam with a mass block on a spin-coated photoresist layer. The lithography machine model was MA6.

[0038] Step 2: Electron beam evaporation is used to deposit 350nm of metallic nickel on the surface of the P-type gallium nitride layer 6, and then the residual photoresist is removed.

[0039] Step 3: ICP etching technology is used to etch the nitride layer down to the n-type gallium nitride layer 4, thereby transferring the pattern defined in the first step to the n-type gallium nitride layer 3 of the silicon-based nitride epitaxial wafer, to obtain the accelerometer beam structure.

[0040] Then, the epitaxial wafer was placed in a dilute nitric acid solution to remove residual metallic nickel, and then rinsed in anhydrous ethanol and ultrapure water in sequence.

[0041] Step 4: Deposit a SiO2 layer on one of the beams in the middle of the accelerometer, but do not deposit a SiO2 layer on a small square at the end of the beam.

[0042] Step 5: Use a spin coater to spin coat the photoresist AZ-5214 on the front side of the epitaxial wafer (the surface of the beam structure and the square surfaces around it) at a speed of 4000 rpm for 40 seconds (the photoresist thickness is 1.5 micrometers).

[0043] Step 6: Electron beam evaporation is used to deposit 420nm metallic nickel on the surface of the n-type gallium nitride layer 4, and then the residual photoresist is removed.

[0044] Step 7: Using ICP etching technology, the pattern is etched downwards until the center is hollowed out;

[0045] Then, the epitaxial wafer was placed in a dilute nitric acid solution to remove residual metallic nickel, and then rinsed in anhydrous ethanol and ultrapure water in sequence.

[0046] Step 8: Wet etching of silicon using a mixture of hydrofluoric acid and dilute nitric acid is performed until the bottom of silicon substrate 1 is reached, forming silicon pillars and a bottom surface supporting this structure in silicon substrate 1, thus suspending one beam structure of the LD. The etching gas is a mixture of HF and HNO3, and the etching time is 1 minute. Finally, the residual photoresist is removed.

[0047] COMSOL Multiphysics is a multiphysics simulation platform encompassing multiple modules including fluid dynamics, electromagnetics, heat transfer, structural dynamics, chemical engineering, acoustics, and equations. By simply providing the coupling relationships between various scenarios and physical fields, the software can express these relationships. This software was used to simulate this invention.

[0048] Steady-state studies of the device were conducted under net gravity, and the stress distribution on the device surface is shown in Figures 4 and 5. It can be observed that the stress at one-quarter of the beam is significantly greater than the stress around it.

Claims

1. A method for fabricating an indium gallium nitride quantum well opto-electro-mechanical microcavity accelerometer based on the quantum confinement Stark effect, characterized in that, The accelerometer uses a silicon-based nitride epitaxial wafer as a carrier and includes, from bottom to top, a silicon substrate layer (1), an aluminum nitride layer (2), a u-type gallium nitride layer (3), an n-type gallium nitride layer (4), a quantum well layer (5), a p-type gallium nitride layer (6), and a SiO2 layer (7). A p-type electrode (8) is disposed on the p-type gallium nitride layer (6), and an n-type electrode (9) is disposed at the edge of the n-type gallium nitride layer (4). The silicon substrate layer (1) retains a central beam (11). After power is applied, the stress-sensitive area (10) of the beam emits a laser LD. This accelerometer is a rectangular ring with a mass block in the middle. The beams are connected, and the two square blocks on both sides of the beam are hollowed out; the p-type electrode (8) is composed of a beam and a square electrode, and the beam has a mass block in the middle; the stress-sensitive area (10) of the beam is not coated with SiO2 layer, and the rest is coated with a layer of SiO2 layer (7). The p-type electrode (8) is deposited on the upper surface of the SiO2 layer (7) on the middle beam; the n-type electrode (9) is deposited on the n-type gallium nitride layer (4) on the other side, and is a square electrode; the stress-sensitive area (10) accounts for one-quarter of the length of the beam (11); when the beam (11) is energized, only the stress-sensitive area (10) will emit laser LD; the specific method includes the following steps: Step 1: Spin-coat photoresist onto the p-type gallium nitride surface of the silicon-based gallium nitride epitaxial wafer, and then use optical lithography to define a pattern of two square disks connected by a beam on the spin-coated photoresist layer; Step 2: Electron beam evaporation is used to deposit 300-500nm thick nickel on the defined pattern surface. Then, the epitaxial wafer is placed in an acetone solution for ultrasonic treatment. After that, the epitaxial wafer is cleaned in ultrapure water, and then cleaned in anhydrous ethanol and ultrapure water in sequence. Finally, the residual photoresist is removed to obtain a nickel mask pattern. Step 3: ICP etching technology is used to etch down 2μm-2.5μm to the n-type gallium nitride layer, thereby transferring the pattern defined in the first step to the n-type gallium nitride layer of the silicon-based nitride epitaxial wafer, to obtain the structure of a beam of the accelerometer; Step 4: Remove metallic nickel with dilute nitric acid, then immediately rinse thoroughly with ultrapure water; Step 5: Deposit a SiO2 layer on the middle beam of the accelerometer, but do not deposit a SiO2 layer on the small square at one-quarter of the beam. Step 6: Spin-coat photoresist onto one beam and the surrounding surface of the accelerometer to ensure that the beam structure and the surrounding area will not be etched away during the etching process, thus providing protection. Step 7: Electron beam evaporation is used to deposit a 300-500nm thick layer of metallic nickel on the defined pattern surface. Then, the epitaxial wafer is placed in an acetone solution for ultrasonic cleaning, followed by cleaning in anhydrous ethanol and ultrapure water. Finally, the residual photoresist is removed to obtain a mask pattern of nickel. Step 8: Using ICP etching technology, the pattern is etched downwards until the center is hollowed out, and finally the residual photoresist is cleaned. Step 9: Electron beam evaporation is used to deposit a positive electrode on the surface of the p-type electrode pattern and a negative electrode on the surface of the n-type electrode pattern, so that positive and negative electrodes are deposited on the p-type gallium nitride layer (6) and the n-type gallium nitride layer (4) respectively. Finally, the residual photoresist is removed to obtain the p-type electrode (8) and the n-type electrode (9). Step 10: Wet etching of silicon is performed using a mixture of hydrofluoric acid and dilute nitric acid until the bottom of the silicon substrate (1) is reached, so that silicon pillars and bottom surfaces supporting this structure are formed in the silicon substrate (1), forming a suspended beam structure.

2. The method for fabricating an indium gallium nitride quantum well opto-electro-mechanical microcavity accelerometer based on the quantum confinement Stark effect according to claim 1, characterized in that, Both the positive and negative electrodes are vapor-deposited Au / Ni.

3. The method for fabricating an indium gallium nitride quantum well opto-electro-mechanical microcavity accelerometer based on the quantum confinement Stark effect according to claim 1, characterized in that: Before and after acceleration load, due to the quantum confinement Stark effect, the frequency wavelength of the laser will change, and the magnitude of acceleration can be sensed through the difference frequency.

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