An In(Ga)As quantum dot ring Bragg waveguide cavity suspended sample and a preparation process thereof

Abstract

This application discloses an In(Ga)As quantum dot ring Bragg waveguide cavity suspension sample and its fabrication process, including: preparing and pretreating the sample, wherein the sample comprises, from bottom to top, a GaAs substrate layer, an Al layer, and an Al layer. 0.75 Ga 0.25 An Al interlayer and a GaAs layer containing quantum dots are formed; a polymer mask layer with microcavities is prepared on the surface of the GaAs layer containing quantum dots; the microcavities are transferred from the mask layer to the GaAs layer containing quantum dots using dry etching; and the Al is hollowed out using wet etching. 0.75 Ga 0.25 As an intermediate layer, an In(Ga)As quantum dot microcavity suspension sample was obtained. Suspension of the In(Ga)As quantum dot microcavity through a combination of dry etching and wet etching hollowing-out process provides optimized optical performance and enhanced mechanical stability, and can play an important role in photonic device design and applications, sensing, and detection.

Description

Technical Field

[0001] This application relates to the field of semiconductor materials technology, specifically to an In(Ga)As quantum dot ring Bragg waveguide cavity suspension sample and its fabrication process. Background Technology

[0002] In the research and application of modern optical devices, improving the intensity of light-matter interaction is one of the key problems that needs to be solved. Optical microcavities have the ability to confine light fields in both time and space, and can confine light within a very small cavity through resonant cycles, thereby promoting the interaction between light and matter. They have been widely studied in the field of photonic information.

[0003] Currently, GaAs quantum dot microcavity samples have wide applications in optoelectronics and quantum computing. Among them, suspended samples have become a research focus due to their excellent optical properties and low loss characteristics. However, existing suspended sample preparation techniques mainly rely on wet preparation, that is, GaAs quantum dots are prepared on a liquid interface with low surface tension through chemical reaction to achieve suspension. Although this method can achieve the preparation of high-quality suspended samples, it has the following problems and limitations: (1) poor suspension stability, which is easily affected by environmental factors, resulting in unstable sample quality; (2) complex preparation process, requiring multiple cleaning and treatment, which is difficult to operate; (3) a large amount of solution is required, and the chemical waste generated in the process pollutes the environment. Summary of the Invention

[0004] To address the aforementioned shortcomings in this field, this application aims to provide an In(Ga)As quantum dot ring Bragg waveguide cavity suspension sample and its fabrication process. This application suspends the In(Ga)As quantum dot microcavity through a combination of dry etching and wet etching hollowing-out treatment, providing optimized optical performance and enhanced mechanical stability, and playing a significant role in photonic device design and applications, sensing, and detection.

[0005] According to one aspect of this application, a fabrication process for an In(Ga)As quantum dot ring Bragg waveguide cavity suspended sample is provided, comprising:

[0006] Sample preparation and pretreatment were performed. The sample, from bottom to top, includes a GaAs substrate layer, an Al layer, and an Al layer. 0.75 Ga 0.25 As intermediate sacrificial layer and GaAs layer containing InAs quantum dots;

[0007] A polymer mask layer with a precision of hundreds of nanometers was prepared on the surface of the GaAs layer containing quantum dots using an electron beam lithography process.

[0008] The microcavity is transferred from the polymer mask layer to the quantum dot-containing GaAs layer using dry etching to remove the residual polymer layer;

[0009] Wet corrosion hollowing out Al 0.75 Ga 0.25 As an intermediate sacrificial layer, an In(Ga)As quantum dot ring Bragg waveguide cavity suspended sample is obtained.

[0010] According to some embodiments of this application, the Al 0.75 Ga 0.25 The thickness of the As intermediate sacrificial layer is 300-1000 nm; the thickness of the GaAs layer containing InAs quantum dots is 80-200 nm.

[0011] According to some embodiments of this application, the dry etching sample stage is set to a temperature of 10-20°C.

[0012] According to some embodiments of this application, the etching gas for dry etching includes a Cl2 / BCl3 / Ar mixture.

[0013] According to some embodiments of this application, the etching gas flow rate is Cl2: 2-6 sccm, BCl3: 3-8 sccm, and Ar: 5-10 sccm.

[0014] According to some embodiments of this application, the pressure of He gas purging on the back side of the sample during dry etching is 10-20 Torr.

[0015] According to some embodiments of this application, the dry etching process pressure is 2-5 mTorr, the upper electrode (ICP) power is 500-800W, the lower electrode (Bias) power is 60W-110W, and the etching time is 1-3 min.

[0016] According to some embodiments of this application, the wet etching is HF wet etching;

[0017] According to some embodiments of this application, the HF wet etching process includes immersing the sample after dry etching sequentially in an HF solution, deionized water, and isopropanol.

[0018] According to some embodiments of this application, the concentration of the HF solution is 2%-10%.

[0019] According to some embodiments of this application, the soaking time of the sample in HF solution is 10-60s, the soaking time in deionized water is 5-15min, and the soaking time in isopropanol is 2-10min.

[0020] According to another aspect of this application, an In(Ga)As quantum dot ring Bragg waveguide cavity suspension sample prepared by the above-described preparation process is also provided. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the sample structure of an example embodiment of this application.

[0022] Figure 2 This is a schematic diagram of the dry etching and wet etching process in an example embodiment of this application.

[0023] Figure 3 This is a cross-sectional schematic diagram of the complete preparation process of an example embodiment of this application.

[0024] Figure 4 This is a schematic diagram showing the area outside the etchable area of ​​the sample covered by polyimide high-temperature tape, as an example embodiment of this application.

[0025] Figure 5 An optical microscope image of an In(Ga)As quantum dot sample in a suspended annular Bragg waveguide cavity, which is an example embodiment of this application.

[0026] Figure 6 A scanning electron microscope image of an In(Ga)As quantum dot sample with a suspended annular Bragg waveguide cavity, which is an example embodiment of this application. Detailed Implementation

[0027] The technical solution of this application will be clearly and completely described below with reference to the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0028] It should be particularly noted that similar substitutions and modifications made to this application are obvious to those skilled in the art, and they are all considered to be included in this application. Those skilled in the art can obviously make modifications or appropriate alterations and combinations to the methods and applications described herein without departing from the content, spirit, and scope of this application to implement and apply the technology of this application. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments.

[0029] Unless otherwise specified, this application is conducted under standard conditions or conditions recommended by the manufacturer. The raw materials or excipients used, as well as the reagents or instruments used, whose manufacturers are not specified, are all conventional products that can be obtained commercially.

[0030] The following is a detailed description of this application.

[0031] This application utilizes a combination of dry etching and wet etching to hollow out the AlGaAs layer, enabling the GaAs quantum dot microcavities to levitate and remain in contact with the underlying GaAs substrate. This approach offers significant advantages and promising applications compared to existing technologies, specifically:

[0032] (1) Improved optical performance: The preparation of suspended samples can reduce interfacial losses between materials, suppress back-side photon leakage, and improve photon collection efficiency. By hollowing out the sample, the top GaAs quantum dot microcavity can be separated from the bottom GaAs substrate, avoiding direct contact and interfacial scattering, making the transmission of light in the microcavity purer and more efficient.

[0033] (2) Enhanced Mechanical Stability: The preparation of suspended samples can improve the mechanical stability of the samples to a certain extent. After hollowing out, the GaAs quantum dot microcavities are no longer in contact with the wafer substrate or other solid supports, reducing the possibility of deformation and loosening caused by factors such as thermal expansion and contraction and stress, thereby improving the structural stability of the samples. In addition, the optical performance of suspended microcavity structure samples is highly dependent on the precise etching depth of the trenches. Changes in etching depth affect the resonant frequency, Purcell enhancement, and collection efficiency. Suspension gives the samples advantages in optical stability and repeatability.

[0034] (3) Photonic Device Design and Application: Suspended samples can play an important role in the design and application of optoelectronic devices. For example, suspended In(Ga)As quantum dot microcavities can serve as high-quality factor lasers or single-photon sources, providing lower energy loss and higher collection efficiency. In addition, when combined with other optical devices, suspended samples can also be used to construct novel micro-nano optical systems and quantum information processing platforms.

[0035] (4) Sensing and Detection Applications: Suspended samples can be applied in the fields of sensing and detection. By utilizing the sensitivity of suspended In(Ga)As quantum dot microcavities to optical signals and combining them with different functional materials or molecules, highly sensitive optical sensing and detection can be achieved. This type of suspended sample has broad application prospects in fields such as biomedicine and environmental monitoring.

[0036] The fabrication process of the In(Ga)As quantum dot ring Bragg waveguide cavity suspended sample in this application includes:

[0037] Preparation of experimental samples: The material structure from bottom to top is as follows: a GaAs substrate layer with a thickness of 350-450 mm, an Al layer with a thickness of 300-1000 nm. 0.75 Ga 0.25 As intermediate layer (hereinafter referred to as AlGaAs layer), 80-200nm thick GaAs layer containing InAs quantum dots.

[0038] Sample pretreatment: Cut a 1cm sample piece from the sample and ultrasonically clean it in organic solvent and deionized water in sequence for later use.

[0039] Preparation of the mask layer: A photoresist is spin-coated onto the sample surface, followed by electron beam exposure to form a polymer mask layer with a fine structure.

[0040] Dry etching to the intermediate layer: The polymer with microcavity structure after exposure and development is used as a mask layer. ICP dry etching is used, and a mixed gas with a Cl2 / BCl3 / Ar ratio is selected. With appropriate equipment process parameters and appropriate etching time, the etching is controlled to penetrate the GaAs layer containing quantum dots at the top. That is, the dry etching depth is 80-200nm, and the microcavity is transferred from the mask layer to the GaAs layer containing quantum dots.

[0041] The process parameter range for dry etching is as follows:

[0042] The sample to be etched is adhered to a 4-inch single-crystal silicon wafer using thermally conductive silicone oil. Polyimide high-temperature tape is applied around the sample to ensure stable etching rates. The sample is then placed in the rapid sample inlet chamber of the ICP (Inductively Coupled Processing) unit. Once the vacuum reaches the preset value, it is transferred to the etching chamber for etching. The equipment process parameters are set as follows: sample stage temperature 10-20℃, He gas purging pressure on the back of the sample 10-20 Torr, etching gases Cl2, BCl3, and Ar set to 2-6 sccm, 3-8 sccm, and 5-10 sccm respectively, process pressure 2-5 mTorr, upper electrode (ICP) power 500-800W, lower electrode (Bias) power 60W-110W, and etching time 1-3 min.

[0043] Wet etching: HF wet etching hollows out the AlGaAs layer beneath the microstructure, causing the GaAs layer containing InAs quantum dots to levitate.

[0044] The parameter ranges for wet corrosion are as follows:

[0045] After dry ICP etching, the sample is stripped of its resist and then immersed in an HF diluent with a concentration between 2% and 10%. The immersion time in the HF diluent is controlled between 10 and 60 seconds. Then, it is immersed in deionized water for 5 to 15 minutes, followed by immersion in isopropanol for 2 to 10 minutes. Finally, it is air-dried.

[0046] The technical solution of this application will be described in detail below with reference to specific embodiments.

[0047] Example

[0048] The structure of the sample used in the preparation experiment is shown in the figure. Figure 1As shown: The material structure from bottom to top is: a 350mm thick GaAs substrate layer, a 1mm thick Al layer... 0.75 Ga 0.25 As intermediate layer, 200nm thick GaAs layer containing InAs quantum dots. Figure 2 A preparation scheme combining dry and wet methods is presented. Figure 3 A schematic cross-sectional view of the complete preparation process is shown below:

[0049] Prepare the sample: Cut a sample about 1 cm in length and width, and clean it by sonication for 5 minutes each in acetone, isopropanol, alcohol and deionized water. Remove it and dry it with a nitrogen gun for later use.

[0050] Preparation of the polymer mask layer: An electron beam lithography (EPR) positive photoresist AR-P6200 was used to homogenize the sample at 6000 rpm for 60 seconds, followed by baking on a hot plate at 150°C for 60 seconds. The baked and cooled sample was then exposed using an electron beam lithography machine, developed in AR600-546 developer for 60 seconds, fixed in deionized water for 60 seconds, and finally baked at 80°C for 5 minutes to harden the film.

[0051] Etching to the middle AlGaAs layer: Using thermally conductive silicone oil, the sample to be etched is adhered to a 4-inch single-crystal silicon wafer. Polyimide high-temperature tape is then applied around the sample. Figure 4 As shown, to ensure the stability of the etching rate, the sample was placed in the rapid sample introduction chamber of the ICP. After the vacuum reached the preset value, it was transferred to the etching chamber for etching. The equipment process parameters were set as follows: the sample stage temperature was set to 20℃, the pressure of He gas purging on the back of the sample was 10 Torr, the etching gas Cl2 / BCl3 / Ar ratio was 4 sccm / 6 sccm / 7 sccm, the process pressure was set to 2.4 Torr, the upper electrode (ICP) power range was set to 600W, the lower electrode (Bias) power range was set to 60W, and the etching time was 2 min 5 s.

[0052] Remove the residual resist remaining after dry etching, place the sample in a resist remover, and bombard it with oxygen plasma for 10 minutes to remove the top resist carbonized by ICP etching; then immerse the sample in acetone at 50°C for 15 minutes to completely remove the residue; then immerse it in isopropanol for 10 minutes; finally, dry it with a nitrogen gun.

[0053] Wet etching: After dry ICP etching, the sample is stripped of its resist and then immersed in a 2% HF dilution solution. To control the extent of the etching process, the immersion time in the HF solution is limited to 20 seconds. Following this, the sample is immersed in deionized water for 10 minutes, then in isopropanol for 5 minutes, and finally air-dried. Under an optical microscope, the boundary lines of the HF etching process are clearly visible on the etched sample. Figure 5 As shown.

[0054] The suspended annular waveguide cavity In(Ga)As quantum dot sample prepared using the processing technology of this embodiment, such as Figure 6 As shown, the dry etching technique achieves ring spacing accuracy in the hundreds of nanometers and allows for controllable etching depth, clearly revealing the suspended ring waveguide structure and the central quantum dot disk.

[0055] This application addresses the following technical problems regarding the In(Ga)As quantum dot toroidal Bragg waveguide cavity suspension sample and its fabrication process:

[0056] 1. Precise control of etching depth and shape of ring Bragg waveguide cavities: Ring Bragg waveguide cavities play a crucial role in quantum dot coupling, thus requiring precise control of their etching depth and shape. This process achieves accurate control of microcavity depth and shape through precise electron beam exposure and dry etching.

[0057] 2. Preparation of high-quality suspended samples: Traditional preparation methods easily introduce impurities, defects, or surface roughness, affecting optical performance. This process achieves the preparation of high-quality suspended samples through dry etching of microcavities and wet etching to hollow them out.

[0058] 3. Improved Optical Performance: The preparation process of suspended samples has a significant impact on optical performance. This process, through wet etching to hollow out the waveguide, can effectively reduce waveguide loss and improve the optical quality of the waveguide, thereby enhancing overall optical performance.

[0059] The main steps of the dry-wet assembly process in this application are as follows:

[0060] 1. Design and processing of the substrate: First, select a suitable substrate material according to the design requirements and perform surface treatment to ensure good adhesion.

[0061] 2. Dry Etching of Microcavities: Using electron beam lithography and dry etching techniques, the microcavity structure of the annular Bragg waveguide is etched into the sacrificial layer. This step requires precise control of the etching depth and shape to achieve the desired microcavity structure.

[0062] 3. Wet etching hollowing: Using wet etching technology, microrings and sacrificial layers are hollowed out by etching to form a suspended sample. This step requires the selection of a suitable etchant and strict control of etching time and conditions to ensure a good suspended cavity structure.

[0063] 4. Cleaning and Inspection: After etching, the sample is thoroughly cleaned to remove residual corrosive agent and impurities. Then, the sample is inspected using tools such as a microscope to ensure that the prepared suspension sample meets the design requirements.

[0064] This process overcomes the following difficulties:

[0065] 1. Microcavity etching control: The dry etching process for microcavities requires precise control of etching depth and shape to ensure the quality and geometry of the microcavities.

[0066] 2. Wet corrosion hollowing: Wet corrosion hollowing requires the selection of appropriate corrosive agents and conditions, and strict control of corrosion time to avoid problems caused by over-corrosion or under-corrosion.

[0067] 3. Improved optical performance: By hollowing out the sample through wet etching, it is necessary to solve the problems of waveguide loss and optical quality to ensure that the prepared suspended sample has excellent optical performance.

[0068] The above is a detailed explanation of the technical problems addressed by the application, as well as the combined dry and wet process steps and challenges. Please note that further optimization and adjustments are needed based on specific circumstances when conducting related research and development in practical applications.

[0069] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of this application. It should be noted that, for those skilled in the art, several improvements and modifications can be made to this application without departing from the principles of this application, and these improvements and modifications also fall within the protection scope of the claims of this application.

Claims

1. A fabrication process for an In(Ga)As quantum dot ring Bragg waveguide cavity suspended sample, characterized in that, include: Sample preparation and pretreatment were performed. The sample, from bottom to top, includes a GaAs substrate layer, an Al layer, and an Al layer. 0.75 Ga 0.25 As intermediate sacrificial layer and GaAs layer containing InAs quantum dots; A polymer mask layer with a precision of hundreds of nanometers was prepared on the surface of the GaAs layer containing InAs quantum dots using an electron beam lithography process. The annular Bragg waveguide cavity is transferred from the polymer mask layer to the GaAs layer containing InAs quantum dots using dry etching, removing the residual polymer mask layer. The dry etching process includes a stage temperature of 10-20°C, an etching gas mixture of Cl2 / BCl3 / Ar, a He purge pressure of 10-20 Torr on the back side of the sample, a process pressure of 2-5 mTorr, an upper electrode power of 500-800 W, a lower electrode power of 60-110 W, an etching time of 1-3 min, and etching gas flow rates of Cl2: 2-6 sccm, BCl3: 3-8 sccm, and Ar: 5-10 sccm. Wet corrosion hollowing out Al 0.75 Ga 0.25 As an intermediate sacrificial layer, an In(Ga)As quantum dot ring Bragg waveguide cavity suspension sample is obtained; wherein, the wet etching is HF wet etching; the HF wet etching includes: immersing the dry-etched sample sequentially in HF solution, deionized water and isopropanol; the HF solution concentration is 2%-10%, the immersion time of the sample in HF solution is 10-60 s, the immersion time in deionized water is 5-15 min, and the immersion time in isopropanol is 2-10 min.

2. The preparation process according to claim 1, characterized in that, The Al 0.75 Ga 0.25 The thickness of the As intermediate sacrificial layer is 300-1000 nm; the thickness of the GaAs layer containing InAs quantum dots is 80-200 nm.

3. An In(Ga)As quantum dot annular Bragg waveguide cavity suspension sample prepared by the preparation process described in claim 1 or 2.

Images