A photovoltaic optoelectronic logic gate device based on a CoAl2O4-based heterojunction thin film and its fabrication method

Abstract

This invention discloses a photovoltaic optoelectronic logic gate device based on a CoAl2O4-based heterojunction thin film and its fabrication method. The invention addresses the problems of traditional optoelectronic logic gate devices, such as limited response bands, the need for external bias voltage for driving, high energy consumption, and limited logic functions. The photovoltaic optoelectronic logic gate device based on a CoAl2O4-based heterojunction thin film of this invention involves depositing a CoAl2O4 thin film on the upper surface of a SiC substrate using a pulsed laser. Multiple surface electrodes are disposed on the CoAl2O4 thin film, and a bottom electrode is disposed on the lower surface of the SiC substrate. By changing the position of the laser irradiation on the CoAl2O4 thin film, different logic gate functions are achieved. The CoAl2O4 thin film provided by this invention effectively promotes the separation of photogenerated electron-hole pairs and reduces the recombination rate by forming a CoAl2O4 / SiC structure. Under 266nm light source irradiation, the logic gate state switches rapidly with changes in the illumination position.

Description

Technical Field

[0001] This invention belongs to the field of photoelectric detection, specifically relating to a CoAl2O4-based heterostructure device based on laser pulse deposition and its fabrication method, and its application as a photoelectric logic gate device. Background Technology

[0002] In recent years, due to the continuous advancement of technologies such as big data and artificial intelligence, the amount of data has increased significantly. Current electronic logic gates have limitations in terms of accuracy and speed, and the explosive demand for large-scale data processing has sparked interest in new logic gate platforms. Compared to electronic logic gates, optoelectronic logic gates have advantages such as lower device integration, lower power consumption, and faster computing speed, attracting considerable attention in fields such as visible light communication, lidar, and artificial intelligence optical computing. Traditional optoelectronic logic gate devices generally rely on polarization modulation or multiple photoelectric input methods to achieve polymorphic logic, which suffers from complex manufacturing processes and limited response bands. Furthermore, most current devices typically require external bias voltage for driving, resulting in high energy consumption, and their logic functions are limited, making direct cascading using optical signals difficult. Therefore, there is an urgent need for optoelectronic logic gate devices with a simple structure, fast response speed, and the ability to perform multiple logic operations.

[0003] Lateral photovoltaic (PV) is a special type of surface photovoltaic phenomenon. Its most significant characteristic is that the photoelectric response signal output by the device changes as the light spot moves across the semiconductor surface. Current semiconductor heterojunction photodetectors based on the lateral PV effect offer advantages such as simple structure, high detection sensitivity, and no need for external power supply. Furthermore, the separation and transport of photogenerated carriers can be controlled through band structure modulation, further enhancing photoelectric performance. Moreover, based on the high dependence of signal strength on illumination position in such detectors, multiple logic gate structures can be implemented by processing the device surface to achieve different positions on the surface when illuminated by a laser.

[0004] SiC materials possess wide bandgap, high temperature resistance, radiation resistance, high breakdown electric field, and low dielectric constant. Spinel oxides, with their complex lattice structures and variable valence ion distributions, are widely used in spin logic devices, electrochemical energy materials, and semiconductor materials. Among them, spinel oxide films of CoAl2O4 exhibit good physical and chemical stability in complex environments. Their p-type conduction at room temperature and epitaxial growth on substrates with greater lattice mismatch make them ideal candidate materials for designing heterojunction optoelectronic devices. Combining CoAl2O4 with SiC to form a heterojunction can effectively construct a built-in electric field, maximizing the advantages of spinel oxide materials in optoelectronic devices and facilitating the fabrication of novel optoelectronic logic gate devices with high sensitivity and ultrafast response speeds. Summary of the Invention

[0005] The purpose of this invention is to address the problems of traditional optoelectronic logic gate devices, such as complex fabrication processes, limited response bands, the need for external bias voltage for driving, high energy consumption, and limited logic functions. This invention proposes a photovoltaic optoelectronic logic gate device based on a CoAl2O4 heterojunction thin film and its fabrication method. This method has advantages such as simple fabrication process, convenient operation, low cost, and easy control of experimental conditions. The device is self-powered and can achieve multiple optoelectronic logic gate structures by changing the illumination position under ultra-fast response speed, making it suitable for the field of optoelectronic detection.

[0006] The photovoltaic optoelectronic logic gate device based on CoAl2O4 heterojunction thin film of the present invention includes a SiC substrate, a CoAl2O4 thin film, multiple surface electrodes and a bottom electrode. A CoAl2O4 thin film with a thickness of 10~60nm is deposited on the upper surface of the SiC substrate using pulsed laser. Multiple surface electrodes are disposed on the CoAl2O4 thin film, and a bottom electrode is disposed on the lower surface of the SiC substrate. Different logic gate functions are realized by changing the position of the laser irradiation on the CoAl2O4 thin film.

[0007] This invention uses the lateral photovoltaic between different surface electrodes as the input value and the longitudinal photovoltaic between the surface electrode and the bottom electrode as the output value. When laser light is irradiated at different positions of the CoAl2O4 thin film, it can realize a variety of optoelectronic logic gate functions.

[0008] The method for fabricating photovoltaic optoelectronic logic gate devices based on CoAl2O4 heterojunction thin films of the present invention is carried out according to the following steps: 1. Mix Co2O3 powder and Al2O3 powder, press them into sheets using a mold, and then sinter them at 900~1100℃ to obtain CoAl2O4 target material; 2. The SiC substrate was ultrasonically cleaned in acetone, anhydrous ethanol and deionized water in sequence to obtain the cleaned SiC substrate. 3. After cleaning, the SiC substrate is placed on a tray in the chamber. After the chamber is evacuated, oxygen is introduced and the SiC substrate is heated. The CoAl2O4 target is irradiated with an excimer laser. The pulsed laser output is controlled to have an energy of 200mJ and a repetition frequency of 1~5Hz to deposit a thin film. After heat preservation, it is naturally cooled to obtain the CoAl2O4 / SiC heterojunction material. IV. Multiple surface electrodes are disposed on the CoAl2O4 thin film of the CoAl2O4 / SiC heterojunction material, and a bottom electrode is disposed on the lower surface of the SiC substrate to obtain a photovoltaic optoelectronic logic gate device based on the CoAl2O4 heterojunction thin film.

[0009] The application of the photovoltaic optoelectronic logic gate device based on the CoAl2O4-based heterojunction thin film of this invention is as an optoelectronic logic gate device.

[0010] This invention uses wide-bandgap semiconductor SiC as the substrate and CoAl2O4 as the thin film material to form a semiconductor heterojunction to fabricate optoelectronic logic gate devices. SiC is a wide-bandgap semiconductor material, and to a certain extent, its detection range is close to the short-wavelength region and can extend to the solar blind zone, which is beneficial for detection in specific environments.

[0011] The photovoltaic optoelectronic logic gate device based on CoAl2O4 heterojunction thin film and its fabrication method described in this invention have the following beneficial effects: 1. The CoAl2O4 thin film provided by this invention effectively promotes the separation of photogenerated electron-hole pairs by forming a CoAl2O4 / SiC structure, reduces the recombination rate, and significantly improves the photoelectric performance of the detector; 2. The photovoltaic optoelectronic logic gate device based on CoAl2O4 heterojunction thin film provided by this invention uses inexpensive and readily available raw materials, has a simple process, saves energy and reduces emissions, and greatly reduces costs; 3. The photovoltaic optoelectronic logic gate device based on CoAl2O4 heterojunction thin film provided by the present invention exhibits rapid switching of logic gate states under 266nm light source illumination as the illumination position changes, making it suitable for multi-logic gate photoelectric detection applications; 4. The photovoltaic optoelectronic logic gate device based on CoAl2O4 heterojunction thin film provided by this invention realizes multiple optoelectronic logic gates using a single device, exhibiting excellent performance and having broad application prospects. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the photovoltaic optoelectronic logic gate device of the CoAl2O4-based heterojunction thin film in Example 1; Figure 2 The graph shows the relationship between the potential difference between the surface electrode and the bottom electrode of the CoAl2O4 / SiC structure prepared in Example 1 as a function of laser power. Figure 3 The graph shows the relationship between the potential difference between two adjacent surface electrodes of the CoAl2O4 / SiC structure prepared in Example 1 and the laser power. Figure 4 The truth table diagram of the AND gate for the multiple logic gate test of the photovoltaic optoelectronic logic gate device of the CoAl2O4-based heterojunction thin film prepared in Example 1; Figure 5 The truth table of the XOR gate for the multiple logic gate test of the photovoltaic optoelectronic logic gate device of the CoAl2O4-based heterojunction thin film prepared in Example 1. Figure 6 The truth table of the "XNOR gate" for the multiple logic gate test of the photovoltaic optoelectronic logic gate device of the CoAl2O4-based heterojunction thin film prepared in Example 1. Figure 7The truth table of the NOR gate for the multiple logic gate test of the photovoltaic optoelectronic logic gate device of the CoAl2O4-based heterojunction thin film prepared in Example 1. Figure 8 The AND gate test results are shown in the multi-logic gate test of the photovoltaic optoelectronic logic gate device of the CoAl2O4-based heterojunction thin film prepared in Example 1. Figure 9 The XOR gate test result is shown in the test diagram of the multiple logic gate test of the photovoltaic optoelectronic logic gate device of the CoAl2O4-based heterojunction thin film prepared in Example 1. Figure 10 The test results of the "XNOR gate" are shown in the test diagram of the photovoltaic optoelectronic logic gate device of the CoAl2O4-based heterojunction thin film prepared in Example 1. Figure 11 The image shows the test results of the "ORNOT gate" of the photovoltaic optoelectronic logic gate device of the CoAl2O4-based heterojunction thin film prepared in Example 1. Detailed Implementation

[0013] Specific Implementation Method 1: The fabrication method of the photovoltaic optoelectronic logic gate device based on CoAl2O4 heterojunction thin film in this implementation method is carried out according to the following steps: 1. Mix Co2O3 powder and Al2O3 powder, press them into sheets using a mold, and then sinter them at 900~1100℃ to obtain CoAl2O4 target material; 2. The SiC substrate was ultrasonically cleaned in acetone, anhydrous ethanol and deionized water in sequence to obtain the cleaned SiC substrate. 3. After cleaning, the SiC substrate is placed on a tray in the chamber. After the chamber is evacuated, oxygen is introduced and the SiC substrate is heated. The CoAl2O4 target is irradiated with an excimer laser. The pulsed laser output is controlled to have an energy of 200mJ and a repetition frequency of 1~5Hz to deposit a thin film. After heat preservation, it is naturally cooled to obtain the CoAl2O4 / SiC heterojunction material. IV. Multiple surface electrodes are disposed on the CoAl2O4 thin film of the CoAl2O4 / SiC heterojunction material, and a bottom electrode is disposed on the lower surface of the SiC substrate to obtain a photovoltaic optoelectronic logic gate device based on the CoAl2O4 heterojunction thin film.

[0014] This embodiment of the photovoltaic optoelectronic logic gate device based on CoAl2O4 heterojunction thin film utilizes lateral photovoltaics generated between different surface electrodes and longitudinal photovoltaics between the surface and bottom electrodes as the input and output of the logic gate, achieving multiple optoelectronic logic gate characteristics by changing the laser irradiation position. This CoAl2O4 / SiC device promotes the separation of photogenerated carriers through the bandgap matching mechanism of the heterojunction, thereby effectively improving photoelectric performance and being applied to the construction of multiple optoelectronic logic gates.

[0015] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the molar ratio of Co2O3 powder to Al2O3 powder in step one is 1:2.

[0016] Specific Implementation Method 3: This implementation method differs from Specific Implementation Method 1 or 2 in that the sintering time in step 1 is 10~15h.

[0017] Specific Implementation Method Four: This implementation method differs from one of the specific implementation methods one to three in that the SiC substrate mentioned in step two is a 4H-SiC substrate.

[0018] Specific Implementation Method 5: This implementation method differs from Specific Implementation Methods 1 to 4 in that oxygen is introduced in step 3 and the pressure is controlled to be 0.01~20Pa.

[0019] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that the SiC substrate is heated to 600~650℃ in step three.

[0020] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One through Six in that in step three, the pulsed laser output is controlled to have an energy of 200mJ and a repetition frequency of 1Hz for pulsed laser deposition of thin films.

[0021] Specific Implementation Method 8: This implementation method differs from Specific Implementation Methods 1 to 7 in that, in step 3, the film is held in situ for 20-30 minutes after pulsed laser deposition.

[0022] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that the surface electrode in step four is made of gold, while the bottom electrode is made of dried silver paste.

[0023] Specific Implementation Method 10: The application of the photovoltaic optoelectronic logic gate device of the CoAl2O4-based heterojunction thin film in this implementation method is as an optoelectronic logic gate device.

[0024] This embodiment uses a 266nm wavelength light source to irradiate a CoAl2O4-based heterojunction thin film, which can be used to construct multiple optoelectronic logic gates.

[0025] Example 1: The fabrication method of the photovoltaic optoelectronic logic gate device based on CoAl2O4 heterojunction thin film in this example is carried out according to the following steps: 1. Co2O3 and Al2O3 are mixed into powder at a molar ratio of 1:2, pressed into tablets using a mold, and then sintered at 1000℃ for 12 hours to obtain CoAl2O4 target material; 2. The SiC substrate was ultrasonically cleaned for 10 minutes each in acetone, anhydrous ethanol and deionized water to obtain the cleaned SiC substrate. 3. Place the cleaned SiC substrate on a tray inside the chamber and evacuate the background vacuum to 4×10⁻⁶. -4 Using a cleaned SiC substrate as the substrate, pure oxygen was introduced to control the gas pressure at 0.1 Pa, and the temperature of the SiC substrate was adjusted to 620℃. An excimer laser was used to irradiate the CoAl2O4 target material, controlling the single pulse energy to be 200 mJ and the pulse frequency to be 1 Hz to deposit a CoAl2O4 layer with a thickness of 15 nm. After deposition, the layer was kept in situ for 30 min, and finally naturally cooled to room temperature to obtain a photovoltaic optoelectronic logic gate device based on a CoAl2O4 heterojunction thin film.

[0026] In this embodiment, the SiC substrate mentioned in step two was purchased from Tianke Heda Blue Light Semiconductor Co., Ltd., and the excimer laser mentioned in step three is a German Compex KrF gas laser.

[0027] The process of setting up the testing equipment for photovoltaic optoelectronic logic gate devices is as follows: Figure 1 This is a schematic diagram of a photovoltaic optoelectronic logic gate device based on the CoAl2O4-based heterojunction thin film prepared in Example 1. A laser (wavelength 266nm) is fixed on a stable support. After passing through a beam expander, a lens with a focal length of 1cm is placed in the optical path to focus the laser spot onto a point approximately 0.1mm in diameter on the thin film. Multiple pieces of gold are pressed onto the surface of the thin film as surface electrodes, and silver paste is coated on the bottom surface of the substrate as the ground electrode. The diameter of the surface electrodes is less than 0.5mm. An electric motor is used to control the movement of a two-dimensional translation stage, thereby changing the illumination position.

[0028] The near-ultraviolet photopotential sensor prepared according to Example 1, under laser irradiation at a wavelength of 266 nm and a power of 1 mW, exhibited a maximum potential difference of 422.13 mV / mm between the surface and bottom electrodes of the CoAl2O4 / SiC structure. Figure 2 The maximum potential difference between two adjacent electrodes on the surface reached 411.37 mV / mm. Figure 3 ).

[0029] Test methods for multiple optoelectronic logic gates: A laser (wavelength 266nm) is fixed on a stable support. After passing through a beam expander, a lens with a focal length of 1cm is placed in the optical path to focus the laser spot onto a point approximately 0.1mm in diameter on a thin film. Multiple pieces of gold are pressed onto the surface of the thin film as surface electrodes, and silver paste is coated on the bottom surface of the substrate as bottom electrodes. The diameter of the surface electrodes is less than 0.5mm. An electric motor is used to control the movement of a two-dimensional translation stage, thereby changing the position of the illumination. Using an oscilloscope, specifically a Tektronix DP05054 digital oscilloscope, the potential differences between surface electrodes a and b, and between surface electrodes a and c, of the CoAl2O4 / SiC structure were observed in real time (defined as input signals 1 and 2). By continuously changing the position of the laser irradiation on the device surface (from surface electrode a to surface electrode d), the potential differences between surface electrode a and the bottom electrode, surface electrode d and the bottom electrode, surface electrode a and surface electrode d, and surface electrode b and surface electrode d at different irradiation positions were observed sequentially (defined as output signals). By comparing with the truth table, it was found that multiple logic gates, including AND gate, XOR gate, XNOR gate, and NOR gate, were constructed. The structural schematic diagram and truth table for the multiple optoelectronic logic gate test are shown below. Figures 4-7 and Figures 8-11 As shown, the lateral photovoltaic generated between different surface electrodes of the device and the longitudinal photovoltaic between the device surface and bottom are used as the input and output of the logic gate. The multiple optoelectronic logic gate characteristics of the device are observed by changing the laser irradiation position.

[0030] This invention involves preparing a CoAl2O4 target material by pressing and sintering a mixture of Co2O3 and Al2O3 powders in a specific ratio. Using SiC as a substrate, a CoAl2O4 thin film is deposited on the substrate surface via pulsed laser deposition. After deposition, the film is held at the original temperature and then naturally cooled to room temperature, resulting in a CoAl2O4 / SiC heterojunction device. The lateral photovoltaics generated between different surface electrodes and the longitudinal photovoltaics between the device surface and bottom are used as the input and output of logic gates. By changing the laser irradiation position, the multi-stage optoelectronic logic gate characteristics of the device are observed. Tests show that the prepared CoAl2O4 / SiC device promotes the separation of photogenerated carriers through the bandgap matching mechanism of the heterojunction, thereby effectively improving photoelectric performance and enabling its application in the construction of multi-stage optoelectronic logic gates.

Claims

1. A photovoltaic optoelectronic logic gate device based on a CoAl2O4 heterojunction thin film, characterized in that... The photovoltaic optoelectronic logic gate device based on the CoAl2O4 heterojunction thin film includes a SiC substrate, a CoAl2O4 thin film, multiple surface electrodes, and a bottom electrode. A CoAl2O4 thin film with a thickness of 10~60nm is deposited on the upper surface of the SiC substrate using a pulsed laser. Multiple surface electrodes are disposed on the CoAl2O4 thin film, and a bottom electrode is disposed on the lower surface of the SiC substrate. Different logic gate functions are realized by changing the position of the laser irradiation on the CoAl2O4 thin film.

2. The method for fabricating photovoltaic optoelectronic logic gate devices based on CoAl2O4-based heterojunction thin films as described in claim 1, characterized in that... The fabrication method of this photovoltaic optoelectronic logic gate device is carried out according to the following steps:

1. Mix Co2O3 powder and Al2O3 powder, press them into sheets using a mold, and then sinter them at 900~1100℃ to obtain CoAl2O4 target material; 2. The SiC substrate was ultrasonically cleaned in acetone, anhydrous ethanol and deionized water in sequence to obtain the cleaned SiC substrate.

3. After cleaning, the SiC substrate is placed on a tray in the chamber. After the chamber is evacuated, oxygen is introduced and the SiC substrate is heated. The CoAl2O4 target is irradiated with an excimer laser. The pulsed laser output is controlled to have an energy of 200mJ and a repetition frequency of 1~5Hz to deposit a thin film. After heat preservation, it is naturally cooled to obtain the CoAl2O4 / SiC heterojunction material. IV. Multiple surface electrodes are disposed on the CoAl2O4 thin film of the CoAl2O4 / SiC heterojunction material, and a bottom electrode is disposed on the lower surface of the SiC substrate to obtain a photovoltaic optoelectronic logic gate device based on the CoAl2O4 heterojunction thin film.

3. The method for fabricating photovoltaic optoelectronic logic gate devices based on CoAl2O4-based heterojunction thin films according to claim 2, characterized in that... In step one, the molar ratio of Co2O3 powder to Al2O3 powder is 1:

2.

4. The method for fabricating photovoltaic optoelectronic logic gate devices based on CoAl2O4-based heterojunction thin films according to claim 2, characterized in that... The sintering time in step one is 10~15 hours.

5. The method for fabricating photovoltaic optoelectronic logic gate devices based on CoAl2O4-based heterojunction thin films according to claim 2, characterized in that... The SiC substrate mentioned in step two is a 4H-SiC substrate.

6. The method for fabricating photovoltaic optoelectronic logic gate devices based on CoAl2O4-based heterojunction thin films according to claim 2, characterized in that... In step three, oxygen is introduced and the pressure is controlled to be 0.01~20 Pa.

7. The method for fabricating photovoltaic optoelectronic logic gate devices based on CoAl2O4-based heterojunction thin films according to claim 2, characterized in that... In step three, the SiC substrate is heated to 600~650℃.

8. The method for fabricating photovoltaic optoelectronic logic gate devices based on CoAl2O4-based heterojunction thin films according to claim 2, characterized in that... In step three, the pulsed laser output is controlled to have an energy of 200 mJ and a repetition frequency of 1 Hz for pulsed laser deposition of thin films.

9. The method for fabricating a photovoltaic optoelectronic logic gate device based on a CoAl2O4-based heterojunction thin film according to claim 2, characterized in that... In step three, after pulsed laser deposition of the thin film, the film is kept in situ for 20-30 minutes.

10. The method for fabricating a photovoltaic optoelectronic logic gate device based on a CoAl2O4-based heterojunction thin film according to claim 2, characterized in that... In step four, the surface electrode is made of gold, while the bottom electrode is made of dried silver paste.

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