Phase change optical synapse device, modulation method and preparation method

Abstract

The application discloses a kind of phase-change optical synapse devices and modulation method, preparation method, belong to integrated optoelectronic technology field;Heating layer is set under the heat conduction layer, and the heat conduction layer is transparent heat conduction film, and its thermal conductivity is greater than the thermal conductivity of heating layer, can evenly transmit the current joule heat generated by heating layer to phase-change material layer, reduce the temperature gradient in phase-change material layer plane;On this basis, set the surrounding layer surrounding phase-change material, can be well isolated heating layer and substrate, reduce substrate heat dissipation, improve heating efficiency;Under the dual action of heat conduction layer and surrounding layer, the application can avoid the recrystallization phenomenon that appears in amorphization process, realize the accurate regulation of phase-change material layer phase-change dynamics process, so that phase-change material layer has gradually crystallized ability and gradually amorphous ability, can realize bilateral polymorphic adjustment in larger modulation range, match the LTP and LTD rule of biological synapse.

Description

Technical Field

[0001] This invention belongs to the field of integrated optoelectronic technology, and more specifically, relates to a phase-change optical synapse device, its modulation method, and its fabrication method. Background Technology

[0002] With the rapid development of big data and artificial intelligence, data transmission, computation, and storage have become new challenges in the information field. The memory wall in the traditional von Neumann architecture has led researchers to shift their focus to neuromorphic computing. Meanwhile, due to the advantages of light, such as ultrafast transmission speed and wavelength division multiplexing parallel computing, photonic neuromorphic computing has become a popular research direction. Optical synaptic devices are an important component of photonic neuromorphic computing; however, traditional optical synaptic devices are mainly based on carrier dispersion effects or thermo-optic effects, resulting in high static power consumption and a small modulation range. Therefore, researching a novel optical synaptic device is of great significance.

[0003] In recent years, phase change materials have attracted widespread attention from scholars at home and abroad due to the huge difference in optical constants between the two phases (refractive index change > 1) and the multiple stable intermediate phase states that are non-volatile between crystalline and amorphous states. Some relatively good progress has been made in phase change optical synaptic devices. Existing phase change optical synaptic devices based on phase change materials mainly include all-optical phase change optical synaptic devices and electrothermal phase change optical synaptic devices. Among them, although all-optical phase change optical synaptic devices can achieve bilateral gradual phase transitions and match the LTP and LTD rules in biological synapses, their modulation range is relatively small. While electrothermal phase change optical synaptic devices have a larger modulation range, they can mostly only achieve unilateral multi-state modulation and cannot match the LTP and LTD rules in biological synapses. For example, an existing electrothermal phase change photosynapse device directly contacts the phase change material layer through a transparent oxide conductive heating layer to heat the phase change material layer. When the phase change material layer reaches a certain temperature, it undergoes a crystallization or amorphization transition, thereby changing the state of the phase change photosynapse device. However, in this process, the thermal conductivity of the transparent oxide conductive heating layer is relatively low, and there is a large temperature gradient on the surface, making it difficult to accurately control the phase composition ratio of the phase change material. Therefore, it is impossible for the phase change material to have both the ability to gradually crystallize and the ability to gradually amorphize, and it is impossible to achieve bilateral multi-state regulation, thus failing to match the LTP and LTD rules in biological synapses. Summary of the Invention

[0004] In view of the above-mentioned defects or improvement needs of the prior art, the present invention provides a phase change optical synapse device, modulation method and preparation method, so as to solve the technical problem that the prior art cannot achieve bilateral multi-state modulation within a large modulation range.

[0005] To achieve the above objectives, in a first aspect, the present invention provides a phase-change optical synapse device, comprising:

[0006] The substrate and waveguide layer are arranged sequentially from bottom to top;

[0007] A surrounding layer is disposed above the substrate and the waveguide layer, and a groove is disposed within the surrounding layer directly above the waveguide layer;

[0008] A phase change material layer and a thermally conductive layer are embedded sequentially from bottom to top in the groove;

[0009] A heating layer covering the upper surface of the heat-conducting layer;

[0010] A first metal electrode and a second metal electrode are disposed above the surrounding layer, on both sides of the groove, and both in contact with the heating layer;

[0011] A covering layer is placed above the heating layer and covers the area where the phase change material layer is located;

[0012] The surrounding layer is made of transparent heat-insulating oxide; the heating layer is made of transparent conductive oxide film; and the thermally conductive layer is made of transparent thermally conductive film with a thermal conductivity greater than that of the heating layer.

[0013] More preferably, the above-mentioned thermally conductive layer is an Al2O3 thin film or an AlN thin film.

[0014] More preferably, the thickness of the above-mentioned thermally conductive layer is 10-50 nm.

[0015] More preferably, the heating layer material is one of ITO, In2O3, and AZO.

[0016] More preferably, the thickness of the heating layer is 150-200 nm.

[0017] More preferably, the material of the surrounding layer is SiO2 or TiO2.

[0018] More preferably, the material of the capping layer is SiO2 or TiO2.

[0019] Secondly, the present invention provides a modulation method for the above-mentioned phase-change optical synapse device, comprising:

[0020] A voltage pulse is applied to the first metal electrode and the second metal electrode. The ratio of crystalline phase to amorphous phase in the phase change material layer is controlled by modulating the amplitude and / or pulse width of the voltage pulse, so as to achieve bilateral multi-state modulation of the phase change photosynaptic device.

[0021] More preferably, a first voltage pulse with gradually increasing amplitude is applied to the first metal electrode and the second metal electrode to gradually crystallize the phase change material layer;

[0022] A second voltage pulse with gradually increasing amplitude is applied to the first metal electrode and the second metal electrode to gradually amorphize the phase change material layer;

[0023] The amplitude of the first voltage pulse is controlled within the range of 1.5-2V, and the pulse width is controlled within the range of 20-100μs.

[0024] The amplitude of the second voltage pulse is controlled within the range of 2.5-3.5V, and the pulse width is controlled within the range of 0.5-5μs.

[0025] Thirdly, the present invention provides a method for fabricating a phase-change optical synapse device, comprising:

[0026] S1. A surrounding layer is fabricated above the substrate and the waveguide layer; wherein, a groove is provided in the surrounding layer directly above the waveguide layer; the waveguide layer is disposed above the substrate;

[0027] S2. Embed the phase change material layer and the thermal conductive layer sequentially from bottom to top in the groove;

[0028] S3. Prepare a heating layer covering the upper surface of the thermally conductive layer;

[0029] S4. Prepare a first metal electrode and a second metal electrode above the surrounding layer, located on both sides of the groove and in contact with the heating layer.

[0030] S5. Deposit a capping layer above the heating layer to cover the area where the phase change material layer is located, forming a phase change photosynapse device;

[0031] The surrounding layer is made of transparent heat-insulating oxide; the heating layer is made of transparent conductive oxide film; and the thermally conductive layer is made of transparent thermally conductive film with a thermal conductivity greater than that of the heating layer.

[0032] In summary, the above-described technical solutions conceived in this invention can achieve the following beneficial effects:

[0033] 1. This invention provides a phase-change photosynapse device, comprising a thermally conductive layer disposed above a heating layer, wherein the thermally conductive layer is a transparent thermally conductive thin film with a thermal conductivity greater than that of the heating layer; the thermally conductive layer uniformly transfers the Joule heat generated by the current in the heating layer to the phase-change material layer, thereby reducing the temperature difference between the highest and lowest temperatures within the phase-change material layer and lowering the temperature gradient within the phase-change material layer; furthermore, a surrounding layer is disposed around the phase-change material, the surrounding layer being made of a transparent thermally insulating oxide, which effectively isolates the heating layer from the substrate, reduces heat dissipation from the substrate, improves heating efficiency, and effectively dissipates the heat generated by the heating layer. Concentrated within the groove, this invention enables precise control of the phase composition of the phase change material within the groove. Under the dual action of the heating layer and the surrounding layer, this invention avoids recrystallization during amorphization, achieving precise control of the phase change kinetics of the phase change material layer, allowing the layer to possess both gradual crystallization and gradual amorphization capabilities. Simultaneously, this invention is also an electrothermal phase change photosynaptic device, with a larger modulation range compared to all-optical phase change photosynaptic devices. Based on this, this invention can achieve bilateral multi-state modulation within a larger modulation range, matching the LTP and LTD rules of biological synapses.

[0034] 2. The phase change optical synapse device provided by the present invention uses a surrounding layer that can alleviate the volume expansion of the phase change material during the phase change process, reduce the thermal stress on the heating layer, and improve the lifespan of the phase change optical synapse device.

[0035] 3. Furthermore, the phase change photosynaptic device provided by the present invention has a thermal conductive layer thickness of 10-50nm, which can improve heating efficiency without introducing additional energy loss while improving the temperature gradient. This allows the present invention to be driven with a lower voltage and with lower energy consumption.

[0036] 4. Furthermore, the phase change optical synapse device provided by the present invention has a heating layer thickness of 150-200nm, which can ensure the heating effect while making the phase change optical synapse device more stable and less prone to damage.

[0037] 5. The phase-change optical synapse device provided by this invention is compatible with existing CMOS processes and has the potential for large-scale application. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the structure of a phase-change optical synapse device provided in an embodiment of the present invention;

[0039] Figure 2 A cross-sectional transmission electron microscope image of the phase change optical synapse device provided in an embodiment of the present invention;

[0040] Figure 3The following diagrams illustrate the thermal field temperature distribution of the phase change material layer under different thermally conductive layer thicknesses, as provided in embodiments of the present invention: (a) is a partial thermal field temperature diagram of the phase change material layer with a thermally conductive layer thickness of 0 nm; (b) is a partial thermal field temperature diagram of the phase change material layer with a thermally conductive layer thickness of 10 nm; (c) is a partial thermal field temperature diagram of the phase change material layer with a thermally conductive layer thickness of 30 nm; (d) is a partial thermal field temperature diagram of the phase change material layer with a thermally conductive layer thickness of 50 nm; and (e) is a partial thermal field temperature diagram of the phase change material layer with a thermally conductive layer thickness of 70 nm.

[0041] Figure 4 The following are thermodynamic simulation diagrams of the heating layer under different heating layer thickness conditions provided in the embodiments of the present invention; wherein, (a) is a thermodynamic simulation diagram of the heating layer with a heating layer thickness of 150nm; (b) is a thermodynamic simulation diagram of the heating layer with a heating layer thickness of 175nm; and (c) is a thermodynamic simulation diagram of the heating layer with a heating layer thickness of 200nm.

[0042] Figure 5 The following are performance diagrams of the phase-change optical synapse device provided in the embodiments of the present invention; wherein, (a) is a diagram showing the change of light transmittance of the phase-change optical synapse device over time; (b) is a diagram showing the change of light transmittance of the phase-change optical synapse device over the number of cycles; and (c) is a diagram showing the bilateral multi-state modulation of the phase-change optical synapse device. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0044] To achieve the above objectives, in a first aspect, the present invention provides a phase-change optical synapse device, such as... Figure 1 As shown, it includes:

[0045] The substrate and waveguide layer are arranged sequentially from bottom to top;

[0046] A surrounding layer is disposed above the substrate and the waveguide layer, and a groove is disposed within the surrounding layer directly above the waveguide layer;

[0047] A phase change material layer and a thermally conductive layer are embedded sequentially from bottom to top in the groove;

[0048] A heating layer covering the upper surface of the heat-conducting layer;

[0049] A first metal electrode and a second metal electrode are disposed above the surrounding layer, on both sides of the groove, and both in contact with the heating layer;

[0050] A covering layer is placed above the heating layer and covers the area where the phase change material layer is located;

[0051] The surrounding layer is made of a transparent, heat-insulating oxide, such as SiO2 or TiO2. The heating layer is a transparent, conductive oxide film, such as ITO, AZO, or In2O3. The thermally conductive layer is a transparent, heat-conducting film with a thermal conductivity greater than that of the heating layer; it can be an Al2O3 or AlN film. Both the thermally conductive and heating layers can be prepared using magnetron sputtering or atomic layer deposition techniques. The capping layer can be made of materials such as SiO2 or TiO2.

[0052] It should be noted that the above-mentioned groove can be formed in several ways. It can be obtained by etching away the surrounding layer region directly above the waveguide layer, or it can be obtained directly by growing the surrounding layer using a window pre-reserved for the groove in photolithography. No limitation is made here. Ideally, the waveguide layer forms the bottom of the groove directly, with the phase change material layer in direct contact with the waveguide layer; more preferably, the phase change material layer and the waveguide layer are in close contact. However, under normal circumstances, due to process limitations, there is a certain gap between the phase change material layer and the waveguide layer (generally controlled within 100nm, preferably within 50nm), which is also acceptable. The thickness of the above-mentioned surrounding layer is generally set to be greater than or equal to 250nm, preferably, the thickness of the surrounding layer is 250–500nm.

[0053] By applying current to the metal electrode, the heating layer generates Joule heat under the action of the current, and the temperature rises. Through the heat transfer effect of the heat-conducting layer, the temperature of the phase change material rises. After reaching the temperature threshold, a phase transition occurs, thereby changing the degree of crystallization of the phase change material layer and achieving different states of the phase change material. The phase composition of the phase change material affects the transmittance of the photosynapse.

[0054] It should be noted that the shape of the aforementioned heat-conducting layer can be a planar trapezoidal structure, a rectangular structure, or a circular structure. Preferably, in one optional embodiment, the shape of the heat-conducting layer is a symmetrical planar rectangular structure. The shape of the heating layer can be a planar trapezoidal structure, a rectangular structure, or a circular structure, etc. Preferably, in one optional embodiment, the shape of the heating layer is a symmetrical planar trapezoidal structure, which can effectively concentrate heat in the central rectangular area, thereby achieving uniform heating of the phase change material layer.

[0055] In one alternative implementation, the first metal electrode and the second metal electrode can be multilayer electrodes formed by stacking any of the metals selected from gold, titanium, platinum and chromium.

[0056] In one alternative implementation, the substrate material and waveguide material of the phase change optical synapse device can be silicon waveguide, silicon nitride, etc.

[0057] In one optional implementation, the phase change material can be a compound composed of two or more elements among Ge, Sb, Te, and Se. Alternatively, it can be a new phase change material formed by doping the aforementioned phase change material (a compound composed of two or more elements among Ge, Sb, Te, and Se) with elements such as Sn, N, and C.

[0058] like Figure 2 The image shown is a cross-sectional transmission electron microscope (TEM) image of the phase change optical synapse device provided by an optional embodiment of the present invention along the waveguide direction. It can be seen that the phase change material layer, the thermal conductive layer, and the heating layer are clearly defined, the interface contact is good, the size and thickness are precisely controlled, which is consistent with the original device design, and the device fabrication process is excellent.

[0059] In one alternative implementation, the thickness of the thermal conductive layer can be selected as 10-70 nm, preferably 30-50 nm.

[0060] Specifically, such as Figure 3 The figures show the simulated thermal field temperature of the phase change material layer under different thermally conductive layer thicknesses (all other parameters are the same); Figure (a) shows the isotherm distribution of the phase change material layer with a thermally conductive layer thickness of 0 nm (no thermally conductive layer added); Figure (b) shows the isotherm distribution of the phase change material layer with a thermally conductive layer thickness of 10 nm; Figure (c) shows the isotherm distribution of the phase change material layer with a thermally conductive layer thickness of 30 nm; Figure (d) shows the isotherm distribution of the phase change material layer with a thermally conductive layer thickness of 50 nm; Figure (e) shows the isotherm distribution of the phase change material layer with a thermally conductive layer thickness of 70 nm. The isotherm distribution of the phase change material layer is shown in the figure. As can be seen from the figure, without a thermally conductive layer, the temperature gradient on the surface of the phase change material is large, with a significant difference between the highest and lowest temperatures. When the thickness of the thermally conductive layer is 10 nm, the temperature gradient shows a slight improvement. When the thickness of the thermally conductive layer is 30-50 nm, the temperature gradient is significantly improved, and the difference between the highest and lowest temperatures is smaller. However, when the thickness of the thermally conductive layer increases to 70 nm, as shown in Figure (e), on the one hand, the temperature of the phase change material decreases significantly, and on the other hand, the temperature uniformity of the phase change material decreases. In summary, a thermally conductive layer thickness of 10-50 nm can improve the temperature gradient, with the most significant improvement observed at 30-50 nm.

[0061] In one alternative implementation, the thickness of the heating layer can be selected as 150-200 nm.

[0062] Specifically, Figure 4Figures (a, b, and c) show the temperature distribution of the heating layer under different heating layer thicknesses (all other parameters are the same). Figure (a) shows the temperature distribution of the heating layer with a thickness of 150 nm; (b) shows the temperature distribution of the heating layer with a thickness of 175 nm; and (c) shows the temperature distribution of the heating layer with a thickness of 200 nm. The figures show that when the heating layer thickness exceeds 150 nm, the heat and temperature generated by the heating layer are sufficient to induce a phase transition in the phase change material. Experimental tests also show that when the heating layer thickness is less than 150 nm, the heating layer is prone to breakage, leading to device failure. Figures (a), (b), and (c) show that the area of ​​heat and temperature generated by the heating layer increases with increasing heating layer thickness. Furthermore, when the heating layer thickness reaches 200 nm, the area of ​​heat and temperature generated significantly exceeds the area of ​​the phase change material. Further increasing the thickness would result in unnecessary energy loss. Therefore, the optimal thickness for the heating layer is 150-200 nm.

[0063] To further illustrate the modulation effect of the phase-change optical synapse device provided by the present invention, the following detailed description is provided in conjunction with specific embodiments: Specific Implementation Method 1

[0065] In the phase change photosynaptic device of this embodiment, the thermally conductive layer is an Al2O3 thin film deposited by atomic layer deposition, the heating layer is an ITO thin film deposited by magnetron sputtering, the metal electrode material is Ti / Pt with a thickness of 10 / 100nm, and the capping layer material is SiO2.

[0066] This implementation method can achieve the following: Figure 5 The device performance diagrams shown are as follows: Figure (a) shows the light transmittance of the phase-change optical synapse device over time; Figure (b) shows the light transmittance of the phase-change optical synapse device over the number of cycles; and Figure (c) shows the bilateral multi-state modulation diagram of the phase-change optical synapse device. As can be seen from the figures, this embodiment can achieve simultaneous bilateral multi-state modulation of the phase-change material's gradual crystallization and amorphization, stable switching over 400 cycles, and a switching contrast exceeding 15 dB. Specific Implementation Method Two

[0068] In the phase change optical synapse device of this embodiment, the thermally conductive layer is an AlN thin film deposited by atomic layer deposition, the heating layer is an ITO thin film deposited by magnetron sputtering, the metal electrode material is Ti / Pt with a thickness of 10 / 100 nm, and the capping layer material is SiO2.

[0069] In this embodiment, the following can also be obtained: Figure 5 The switching performance diagram is shown; Table 1 shows the physical properties of Al2O3 and AlN. It can be seen from the table that their parameters are similar, so they can achieve similar heating effects.

[0070] Table 1

[0071] Specific Implementation Method 3

[0073] In the phase change photosynaptic device of this embodiment, the thermally conductive layer is an Al2O3 thin film deposited by atomic layer deposition, the heating layer is an In2O3 thin film deposited by magnetron sputtering, the metal electrode material is Ti / Pt with a thickness of 10 / 100nm, and the capping layer material is SiO2.

[0074] This embodiment can also yield the following results: Figure 5 The switching performance diagram is shown in Table 2; Table 2 shows the physical properties of ITO and In2O3. It can be seen that their parameters are similar, so they can achieve similar heating effects.

[0075] Table 2

[0076] Material resistivity Ω / cm Thermal conductivity W / (m·K) ITO <![CDATA[1.25×10 -3 ]]> 11 <![CDATA[In2O3]]> <![CDATA[1.6×10 -3 ]]> 11

[0077] In summary, this invention uses a transparent thin film with high thermal conductivity and low optical absorption as the thermally conductive layer material and a transparent conductive oxide thin film as the heating layer material. By controlling the thickness of the thermally conductive layer, the thickness of the heating layer, and the cover layer, the heating effect of the device can be adjusted, thereby achieving precise modulation of the phase change material state in the photosynaptic device, and thus realizing the gradual crystallization and gradual amorphization of the device.

[0078] Secondly, the present invention provides a modulation method for the above-mentioned phase-change optical synapse device, comprising:

[0079] A voltage pulse is applied to the first metal electrode and the second metal electrode. The ratio of crystalline phase to amorphous phase in the phase change material layer is controlled by modulating the amplitude and / or pulse width of the voltage pulse, so as to achieve bilateral multi-state modulation of the phase change photosynaptic device.

[0080] The related technical solutions are the same as those provided in the first aspect of this invention for the phase-change optical synapse device, and will not be described in detail here.

[0081] In one alternative implementation, a first voltage pulse with gradually increasing amplitude is applied to the first metal electrode and the second metal electrode to gradually crystallize the phase change material layer.

[0082] A second voltage pulse with gradually increasing amplitude is applied to the first metal electrode and the second metal electrode to gradually amorphize the phase change material layer;

[0083] The amplitude of the first voltage pulse is controlled within the range of 1.5-2V, and the pulse width is controlled within the range of 20-100μs.

[0084] The amplitude of the second voltage pulse is controlled within the range of 2.5-3.5V, and the pulse width is controlled within the range of 0.5-5μs.

[0085] It should be noted that by adjusting the amplitude and / or pulse width of the voltage pulse applied to the metal electrode, the applied energy can be precisely controlled, thereby controlling the gradual crystallization and amorphization process of the phase change material.

[0086] In one specific embodiment, the surrounding layer is SiO2 grown on the entire substrate and waveguide layer using chemical vapor deposition technology. Subsequently, an etched window is generated above the waveguide layer using ultraviolet lithography and etching processes, and a phase change material is filled in it, so that the phase change material is in close contact with the waveguide layer while being surrounded by SiO2.

[0087] After the phase-change photosynaptic device completes 200 switching cycles, a gradually crystallizing pulse is applied to the phase-change photosynaptic device. The pulse width is 30 μs, and the pulse amplitude is increased from 1.65V to 1.75V in steps of 0.01V, resulting in 11 crystallized intermediate states. Subsequently, the pulse width is changed to 2 μs, and the pulse amplitude is increased from 2.9V to 3.4V in steps of 0.05V, resulting in 11 amorphous intermediate states.

[0088] Thirdly, the present invention provides a method for fabricating a phase-change optical synapse device, comprising:

[0089] S1. A surrounding layer is fabricated above the substrate and the waveguide layer; wherein, a groove is provided in the surrounding layer directly above the waveguide layer; the waveguide layer is disposed above the substrate; wherein, the material of the surrounding layer is a transparent heat-insulating oxide;

[0090] In one alternative implementation, a surrounding layer is first deposited above the substrate and the waveguide layer. Then, the surrounding layer region directly above the waveguide layer is etched away to form a groove within the surrounding layer. For example, the surrounding layer is SiO2 grown on the entire substrate using chemical vapor deposition. Subsequently, an etched window (groove) is generated above the waveguide using ultraviolet lithography and etching processes, and a phase change material is filled in it, so that the phase change material is in contact with the waveguide layer while being surrounded by SiO2.

[0091] It should be noted that chemical vapor deposition is not the only technology for growing SiO2; other methods include magnetron sputtering, etc., which are not limited here.

[0092] In another alternative implementation, the growth window with pre-reserved grooves in the photolithography is used directly to grow and form a surrounding layer with grooves.

[0093] S2. A phase change material layer and a thermally conductive layer are sequentially embedded in the groove from bottom to top; wherein, the thermally conductive layer is a transparent thermally conductive film, and its thermal conductivity is greater than that of the heating layer.

[0094] In one optional embodiment, a phase change material is filled into the groove, so that the phase change material is in contact with the waveguide layer while being surrounded by SiO2. A transparent thermally conductive thin film with high thermal conductivity and low optical absorption is deposited above the phase change material layer of the phase change optical synapse device to form a thermally conductive layer; specifically, in this optional embodiment, an Al2O3 thin film with a thickness of 30-50 nm is deposited on the silicon waveguide substrate on which the phase change material is deposited to form a thermally conductive layer. It should be noted that, in addition to atomic layer deposition technology, deposition technology such as magnetron sputtering can also be used to deposit the thermally conductive layer, and there is no limitation.

[0095] S3. Prepare a heating layer covering the upper surface of the thermally conductive layer; wherein, the heating layer is a transparent conductive oxide thin film;

[0096] Specifically, a transparent conductive oxide thin film is deposited above the thermally conductive layer of the phase-change photosynthetic device to form a heating layer. In one optional embodiment, a heating layer pattern is first prepared above the thermally conductive layer using ultraviolet lithography, and then an ITO conductive thin film with a thickness of 150-200 nm is deposited using magnetron sputtering technology to form the heating layer. It should be noted that, in addition to magnetron sputtering technology, atomic layer deposition technology or other deposition techniques can also be used to deposit the heating layer, and there is no limitation on this method.

[0097] S4. Prepare a first metal electrode and a second metal electrode above the surrounding layer, located on both sides of the groove and in contact with the heating layer.

[0098] In one alternative implementation, in this embodiment, an electrode pattern is fabricated on the substrate using ultraviolet lithography, and then electrode materials are deposited using magnetron sputtering. The electrode materials are titanium and platinum, with thicknesses of 10 nm and 100 nm, respectively. It should be noted that the magnetron sputtering technique used here is not the only option; techniques such as electron beam evaporation (EBE) can also be used for fabrication.

[0099] S5. Deposit a capping layer above the heating layer to cover the area where the phase change material layer is located, forming a phase change photosynapse device;

[0100] In one alternative implementation, a pattern for the capping layer is prepared on the substrate using ultraviolet lithography, and then a 200 nm thick SiO2 layer is deposited using magnetron sputtering. It should be noted that magnetron sputtering is not the only alternative technique; other techniques such as physical chemical vapor deposition (PECVD) can also be used for preparation.

[0101] It should be noted that the photolithography process mentioned above is not limited to ultraviolet lithography; electron beam lithography (EBL) and other photolithography processes can also be used.

[0102] The related technical solutions are the same as those provided in the first aspect of this invention for the phase-change optical synapse device, and will not be described in detail here.

[0103] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A phase-change optical synapse device, characterized in that, include: The substrate and waveguide layer are arranged sequentially from bottom to top; A surrounding layer is disposed above the substrate and the waveguide layer, and a groove is disposed within the surrounding layer directly above the waveguide layer; A phase change material layer and a thermally conductive layer are sequentially embedded in the groove from bottom to top; A heating layer covering the upper surface of the thermally conductive layer; The first metal electrode and the second metal electrode are disposed above the surrounding layer, on both sides of the groove, and both in contact with the heating layer; A cover layer disposed above the heating layer and covering the area where the phase change material layer is located; The surrounding layer is made of a transparent heat-insulating oxide; the heating layer is a transparent conductive oxide film; and the thermally conductive layer is a transparent thermally conductive film with a thermal conductivity greater than that of the heating layer.

2. The phase-change optical synapse device according to claim 1, characterized in that, The thermally conductive layer is an Al2O3 thin film or an AlN thin film.

3. The phase-change optical synapse device according to claim 1, characterized in that, The thickness of the thermally conductive layer is 10-50 nm.

4. The phase-change optical synapse device according to any one of claims 1-3, characterized in that, The heating layer is made of one of ITO, In2O3, or AZO.

5. The phase-change optical synapse device according to any one of claims 1-3, characterized in that, The thickness of the heating layer is 150-200 nm.

6. The phase-change optical synapse device according to any one of claims 1-3, characterized in that, The material of the surrounding layer is SiO2 or TiO2.

7. The phase-change optical synapse device according to any one of claims 1-3, characterized in that, The material of the covering layer is SiO2 or TiO2.

8. The modulation method of the phase-change optical synaptic device according to any one of claims 1-7, characterized in that, include: A voltage pulse is applied to the first metal electrode and the second metal electrode. The ratio of crystalline phase to amorphous phase in the phase change material layer is controlled by modulating the amplitude and / or pulse width of the voltage pulse, so as to achieve bilateral multi-state modulation of the phase change photosynaptic device.

9. The modulation method of the phase-change optical synapse device according to claim 8, characterized in that, When the phase change photosynaptic device is subjected to the first multistate adjustment, a first voltage pulse with gradually increasing amplitude is applied to the first metal electrode and the second metal electrode to cause the phase change material layer to gradually crystallize. When the phase change photosynaptic device is subjected to the second polymorphism, a second voltage pulse with gradually increasing amplitude is applied to the first metal electrode and the second metal electrode to gradually amorphize the phase change material layer. The amplitude of the first voltage pulse is controlled within the range of 1.5-2V, and the pulse width is controlled within the range of 20-100μs. The amplitude of the second voltage pulse is controlled within the range of 2.5-3.5V, and the pulse width is controlled within the range of 0.5-5μs.

10. A method for fabricating a phase-change optical synaptic device, characterized in that, include: S1. A surrounding layer is prepared above the substrate and the waveguide layer; a groove is provided in the surrounding layer located directly above the waveguide layer; The waveguide layer is disposed above the substrate; S2. A phase change material layer and a thermally conductive layer are sequentially embedded in the groove from bottom to top. S3. Prepare a heating layer covering the upper surface of the thermally conductive layer; S4. A first metal electrode and a second metal electrode are prepared above the surrounding layer, located on both sides of the groove and in contact with the heating layer; S5. Deposit a capping layer above the heating layer to cover the area where the phase change material layer is located, forming a phase change photosynapse device; The surrounding layer is made of a transparent heat-insulating oxide; the heating layer is a transparent conductive oxide film; and the thermally conductive layer is a transparent thermally conductive film with a thermal conductivity greater than that of the heating layer.

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