Photoelectric memory and preparation method and modulation method thereof

Abstract

The invention provides a photoelectric memory and a preparation method and a modulation method thereof, and belongs to the technical field of photoelectric memories. The photoelectric memory comprises a substrate; the polarization layer is located on the first surface of the substrate, and the polarization layer is made of a material with a spontaneous polarization effect; the photosensitive layer is located on the polarization layer or located between the substrate and the polarization layer, and the photosensitive layer is suitable for generating a photo-induced electron-hole pair in response to an optical signal incident to the photosensitive layer; wherein the polarization layer forms a built-in electric field in the photosensitive layer based on a spontaneous polarization effect, the built-in electric field is suitable for separating photo-generated electron-hole pairs, and the photoelectric memory realizes optical signal writing and nonvolatile storage based on a capture effect of a defect state of the photosensitive layer on photo-generated holes. The photoelectric memory provided by the invention has the advantages of good retention characteristic, high switch ratio and polymorphic storage capability.

Description

Technical Field

[0001] The present invention relates to the technical field of optoelectronic storage. At least one embodiment of the present invention relates to an optoelectronic memory, and particularly to an optoelectronic memory with automatic writing and non-volatility, and its preparation method and modulation method. Background Art

[0002] Optoelectronic memories naturally have the advantage of integrating sensing and storage functions, which is conducive to simplifying the system architecture and improving information processing efficiency. Their excellent multi-state storage characteristics also help to alleviate the storage pressure in the current big data era. The key to realizing non-volatile storage of optical signals lies in the effective separation and storage of photo-generated carriers. However, in the existing technical solutions, in order to achieve the spatial separation of photo-generated electron-hole pairs, it is inevitable to apply a high voltage to the device gate, resulting in a large device power consumption (or high operation complexity), which limits the practical application of optoelectronic memories. Summary of the Invention

[0003] In view of this, in order to at least partially solve the above-mentioned technical problems, the present invention provides an optoelectronic storage device and its preparation method and modulation method.

[0004] According to an embodiment of one aspect of the present invention, an optoelectronic storage device is provided, including:

[0005] A substrate; a polarization layer located on the first surface of the substrate, the polarization layer being made of a material with spontaneous polarization effect; and a photosensitive layer located on the polarization layer or between the substrate and the polarization layer, the photosensitive layer being adapted to generate photo-generated electron-hole pairs in response to an optical signal incident on the photosensitive layer; wherein, the polarization layer forms a built-in electric field in the photosensitive layer based on the spontaneous polarization effect, and the built-in electric field is adapted to separate the photo-generated electron-hole pairs, and based on the capture effect of the photo-generated holes by the defect states of the photosensitive layer, the optoelectronic memory realizes the writing and non-volatile storage of optical signals.

[0006] According to an embodiment of another aspect of the present invention, a preparation method of an optoelectronic memory is provided, including: growing a polarization layer on a substrate, wherein the material of the polarization layer has a spontaneous polarization effect; and growing a photosensitive layer on the polarization layer.

[0007] According to an embodiment of still another aspect of the present invention, a modulation method of an optoelectronic memory is provided, including:

[0008] Irradiating an optical signal onto the photosensitive layer of the optoelectronic memory to realize the writing and non-volatile storage of the optical signal.

[0009] According to the photoelectric memory provided in the above embodiments of the present invention, a polarization layer is formed between the substrate and the photosensitive layer. By utilizing the depletion effect of the spontaneous polarization effect of the polarization layer on the photosensitive layer, a space charge region is formed in the photosensitive layer. The built-in electric field in the space charge region can achieve rapid spatial separation of the photo-generated electron-hole pairs in the photosensitive layer, realizing automatic writing of the optical signal applied to the photoelectric memory. And based on the capture effect of the defect states of the photosensitive layer on the photo-generated holes, combined with the blocking effect of the polarization barrier region on the photo-generated electrons, non-volatile storage of the optical signal is achieved. The photoelectric memory provided by the present invention has good retention characteristics, a high on-off ratio, and multi-state storage capabilities. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings of the embodiments will be briefly introduced below. Obviously, the accompanying drawings in the following description only relate to some embodiments of the present invention and do not limit the present invention.

[0011] Figure 1 Schematic cross-sectional view of the photoelectric memory provided by the embodiment of the present invention;

[0012] Figure 2 Schematic cross-sectional view of the photoelectric memory provided by another embodiment of the present invention;

[0013] Figure 3 Flowchart of the preparation method of the photoelectric memory provided by the embodiment of the present invention;

[0014] Figure 4 Schematic diagram of the drift process of photo-generated electron-hole pairs during the writing process of the optical signal of the photoelectric memory provided by the embodiment of the present invention;

[0015] Figure 5 Schematic diagram of the working principle of the writing process of the optical signal of the photoelectric memory provided by the embodiment of the present invention;

[0016] Figure 6 Schematic diagram of the working principle of the erasing process of the optical signal of the photoelectric memory provided by the embodiment of the present invention;

[0017] Figure 7 Schematic diagram of the working principle of the photoelectric memory provided by the embodiment of the present invention during the entire working cycle of writing / reading after writing / erasing / reading after erasing;

[0018] Figure 8 Schematic diagram of the retention characteristics of the photoelectric memory provided by the embodiment of the present invention in two modes of "on" state and "off" state; and

[0019] Figure 9 Schematic diagram of the multi-state storage of the photoelectric memory provided by the embodiment of the present invention.

[0020] Description of reference numerals:

[0021] 1-substrate; 2-polarization layer; 3-photosensitive layer; 4-source; 5-drain; 6-gate; 7-photogenerated holes; 8-photogenerated electrons; 9-interface defects; 10-defect states in the photosensitive layer. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical scheme and advantages of the present invention more clear, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. However, the present invention can be implemented in different forms and should not be construed as being limited to the embodiments set forth herein. On the contrary, providing these embodiments will make the invention thorough and complete and fully convey the scope of the present invention to those skilled in the art. In the accompanying drawings, for clarity, the sizes and relative sizes of layers and regions may be exaggerated, and the same reference numerals throughout represent the same elements.

[0023] The terms used herein are only for describing specific embodiments and are not intended to limit the present invention. The terms "comprise", "include", etc. used herein indicate the existence of the features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0024] In related technologies, the key to achieving non-volatile storage of optical signals lies in the effective separation and storage of photogenerated carriers generated by optical signals. In order to achieve spatial separation of photogenerated electron-hole pairs, it is inevitable to apply a high voltage to the device gate, resulting in high device power consumption and high operational complexity.

[0025] In view of this, the present invention provides a photoelectric storage device and a preparation method and a modulation method thereof. The photoelectric storage device provided by the present invention can realize the writing and non-volatile storage of optical signals without applying a high gate voltage on the gate of the device, which can reduce the power consumption of the device and also reduce the operation complexity of the device.

[0026] Figure 1 A cross-sectional schematic diagram of an optoelectronic memory provided by an embodiment of the present invention.

[0027] According to an exemplary embodiment of the present invention, the present invention provides an optoelectronic memory, referring to Figure 1 As shown, including:

[0028] Substrate 1;

[0029] A polarization layer 2 is located on the first surface of the substrate 1, and the polarization layer 2 is made of a material having a spontaneous polarization effect; and

[0030] The photosensitive layer 3 is located on the polarization layer 2 or between the substrate 1 and the polarization layer 2. The photosensitive layer 3 is adapted to generate photo-generated electron-hole pairs in response to an optical signal incident on the photosensitive layer 3.

[0031] Wherein, the polarization layer 2 forms a built-in electric field in the photosensitive layer 3 based on the spontaneous polarization effect. The built-in electric field is adapted to separate the photo-generated electron-hole pairs. Based on the capture effect of the photo-generated holes by the defect states of the photosensitive layer 3, the optoelectronic memory realizes the writing and non-volatile storage of optical signals.

[0032] Reference Figure 1 As shown, the above optoelectronic memory further includes: a source electrode 4 and a drain electrode 5, which are respectively located on the photosensitive layer 3; and a gate electrode 6, which is located on the second surface of the substrate 1 opposite to the first surface.

[0033] Figure 2 It is a schematic cross-sectional view of the optoelectronic memory provided by another embodiment of the present invention.

[0034] Reference Figure 2 As shown, the above optoelectronic memory further includes a source electrode 4 and a drain electrode 5, which are respectively located on the photosensitive layer 3; and a gate electrode 6, which is located on the polarization layer 2.

[0035] In an embodiment of the present invention, the substrate 1 is made of a highly conductive material. The substrate 1 can be, for example, a (111)-plane p-type silicon highly conductive substrate. The resistivity of the substrate 1 is 0.001 Ω·cm - 0.1 Ω·cm, and can be, for example, 0.001 Ω·cm, 0.005 Ω·cm, 0.01 Ω·cm, 0.05 Ω·cm, 0.1 Ω·cm, but is not limited to the listed values.

[0036] In some embodiments, the material of the substrate 1 can be, for example, gallium arsenide, silicon carbide or gallium nitride.

[0037] In some embodiments, the thickness of the substrate 1 can be, for example, 500 μm.

[0038] In an embodiment of the present invention, the polarization layer 2 is made of a material with a spontaneous polarization effect; the material of the polarization layer 2 includes GaN, AlN, AlGaN or AlScN.

[0039] In some embodiments, the spontaneous polarization intensity of the polarization layer 2 is 0.01 C / cm 2 ~1 C / cm 2 , and can be, for example, 0.01 C / cm 2 , 0.05 C / cm 2 , 0.1 C / cm 2 , 0.5 C / cm 2 , 1 C / cm 2, but not limited to the recited values. If the spontaneous polarization intensity is too small, the spontaneous polarization effect of the polarization layer 2 is not significant, and it is difficult to achieve rapid separation of photo-generated electron-hole pairs. If the spontaneous polarization intensity is too large, the built-in electric field in the photosensitive layer is too large, which will affect the gate voltage applied during the reading process of the written optical signal and is not conducive to the reading of the optical signal.

[0040] In an embodiment of the present invention, the thickness of the polarization layer 2 is 1 nm to 1000 nm. For example, it can be 1 nm, 10 nm, 100 nm, 500 nm, 1000 nm, but not limited to the recited values. If the thickness of the polarization layer 2 is too thin, electrons will undergo quantum tunneling through the polarization layer 2, resulting in an increase in the dark current of the device, thereby reducing the stability of the device; if the thickness of the polarization layer 2 is too thick, the series resistance of the device will increase, affecting the device performance, such as resulting in a slower response speed or a weakened read current signal.

[0041] In some embodiments, the photosensitive layer 3 is a gallium oxide semiconductor material or a doped gallium oxide semiconductor material. For example, it can be tin-doped gallium oxide, germanium-doped gallium oxide, but not limited to the recited doping elements. Doping can improve the conductivity of the gallium oxide semiconductor material, thereby increasing the read current of the device. The crystal form of the gallium oxide semiconductor material is not limited herein.

[0042] In some embodiments, the photosensitive layer 3 can be, for example, a gallium oxide thin film, and the type of the gallium oxide thin film can be, for example, ε-Ga2O3.

[0043] In some embodiments, the thickness of the photosensitive layer 3 is 1 nm to 1000 nm; for example, it can be 1 nm, 10 nm, 20 nm, 50 nm, 100 nm, 1000 nm, but not limited to the recited values.

[0044] In an embodiment of the present invention, the materials of the source electrode 4, the drain electrode 5, and the gate electrode 6 are independently selected from one of Ti / Au, Ti / Al / Ni / Au, Cr / Au, Ag, In, Al, Pd, ITO, Ni / Au, Pt, Au, and graphene.

[0045] In an embodiment of the present invention, the capture effect of the defect states of the photosensitive layer 3 on photo-generated holes includes: oxygen vacancies in the photosensitive layer 3, gallium vacancies in the photosensitive layer 3, and / or interface defect states between the photosensitive layer 3 and the polarization layer 2 are suitable for capturing photo-generated holes to inhibit the recombination of photo-generated electrons and photo-generated holes.

[0046] In an embodiment of the present invention, the thicknesses of the source electrode 4, the drain electrode 5, and the gate electrode 6 are independently 5 nm - 500 nm. For example, it can be 5 nm, 10 nm, 100 nm, 200 nm, 500 nm, but not limited to the recited values.

[0047] In an embodiment of the present invention, the shapes of the source electrode 4, the drain electrode 5, and the gate electrode 6 are not limited herein, and the shapes of the source electrode 4, the drain electrode 5, and the gate electrode 6 are independently selected from one of a square, a circle, an interdigital shape, and a polygon.

[0048] According to an exemplary embodiment of the present invention, the present invention provides a modulation method for an optoelectronic memory, including: irradiating an optical signal onto a photosensitive layer of the optoelectronic memory to achieve writing and non-volatile storage of the optical signal.

[0049] In an embodiment of the present invention, the optical signal is in the solar-blind ultraviolet light band.

[0050] Figure 3 It is a flowchart of a preparation method for the optoelectronic memory provided by the embodiment of the present invention.

[0051] According to an exemplary embodiment of the present invention, the present invention provides a preparation method for an optoelectronic memory, referring to Figure 1 、 Figure 3 shown, including: operations S1 to S4.

[0052] Operation S1, growing a polarization layer 2 on a first surface of a substrate 1, and the material of the polarization layer 2 has a spontaneous polarization effect.

[0053] In an embodiment of the present invention, before growing the polarization layer 2 on the first surface of the substrate 1, the substrate 1 is cleaned to remove impurities of the substrate 1, and is dried and baked with nitrogen for later use. For example, the substrate 1 is sequentially placed in acetone, isopropyl alcohol, and deionized water for ultrasonic cleaning and rinsing, and after rinsing clean, it is dried with nitrogen.

[0054] In some embodiments, the polarization layer 2 is an aluminum nitride thin film, and the thickness of the polarization layer 2 is 200 nm.

[0055] In some embodiments, the growth method of the polarization layer 2 includes but is not limited to metal organic chemical vapor deposition (MOCVD), radio frequency magnetron sputtering, molecular beam epitaxy (MBE), pulsed laser deposition (PLD), halide vapor phase epitaxy (HVPE), low pressure chemical vapor deposition (LPCVD), and atomic layer deposition (ALD).

[0056] Operation S2, growing a photosensitive layer 3 on the polarization layer 2.

[0057] In some embodiments, the growth method of the photosensitive layer 3 includes but is not limited to metal organic chemical vapor deposition (MOCVD), radio frequency magnetron sputtering, molecular beam epitaxy (MBE), pulsed laser deposition (PLD), halide vapor phase epitaxy (HVPE), low pressure chemical vapor deposition (LPCVD), atomic layer deposition (ALD).

[0058] In some embodiments, the photosensitive layer 3 is made of an ε-Ga2O3 thin film. Specifically, a gallium oxide thin film is grown on the aluminum nitride thin film by MOCVD. The type of the gallium oxide thin film is ε-Ga2O3, and the thickness of the ε-Ga2O3 thin film can be, for example, 100 nm. During the growth process, the temperature is controlled at 480 °C and the pressure is 25 Torr.

[0059] Operation S3: The source electrode 4 and the drain electrode 5 are respectively grown on the photosensitive layer 3.

[0060] In some embodiments, the source electrode 4 and the drain electrode 5 are grown on the photosensitive layer 3 by electron beam evaporation coating. The materials of the source electrode 4 and the drain electrode 5 are both a stack of Ti and Au (Ti / Au). The thickness of Ti is 40 nm and the thickness of Au is 60 nm.

[0061] Operation S4: The gate electrode 6 is grown on the second surface of the substrate 1 opposite to the first surface.

[0062] In some embodiments, Ti / Al / Ni / Au is grown by electron beam evaporation coating, with thicknesses of 20 nm / 160 nm / 40 nm / 80 nm respectively.

[0063] The following schematically illustrates the designed optoelectronic memory, its manufacturing method, and modulation method. It should be noted that this example is only a specific embodiment of the present invention and does not limit the protection scope of the present invention.

[0064] Embodiment 1

[0065] Reference Figure 1 As shown, an optoelectronic memory is prepared. Specifically, p-Si is used as the substrate 1, an AlN thin film is grown on the first surface of the p-Si as the polarization layer 2, and ε-Ga2O3 is grown on the AlN thin film as the photosensitive layer 3. A Ti / Au stack is grown on the photosensitive layer 3 as the source electrode 4 and the drain electrode 5. Ti / Al / Ni / Au is grown on the second surface of the p-Si as the gate electrode 6.

[0066] Figure 4 It is a schematic diagram of the drift process of photo-generated electron-hole pairs during the writing process of the optical signal of the optoelectronic memory provided by the embodiment of the present invention.

[0067] Figure 5 It is a schematic diagram of the working principle of the writing process of the optical signal of the optoelectronic memory provided by the embodiment of the present invention.

[0068] Reference Figure 4 、 Figure 5As shown, when a photo-optical memory is irradiated with an optical signal (deep ultraviolet light, DUV) in the solar-blind ultraviolet band, the optical signal generates photo-generated electron-hole pairs. Under the action of the built-in electric field in the space charge region on the ε-Ga2O3 side, the photo-generated holes 7 migrate towards the ε-Ga2O3 / AlN interface, while the photo-generated electrons 8 drift in the opposite direction, resulting in a positive pulse current at the drain and an increase in the drain current. This indicates that the photo-optical memory provided by the embodiment of the present invention can effectively separate photo-generated electron-hole pairs in the power-off state and achieve the "writing" of optical signals. A part of the photo-generated holes near the ε-Ga2O3 / AlN interface is captured by the interface defects 9, and a part is captured by the defect states 10 in ε-Ga2O3. For the photo-generated electrons in the photosensitive layer 3, due to the blocking of the built-in electric field, they cannot effectively enter the vicinity of the ε-Ga2O3 / AlN interface, inhibiting the recombination process of photo-generated electrons and photo-generated holes, and achieving non-volatile storage of optical signals.

[0069] Figure 6 It is a schematic diagram of the working principle of the erasing process of the optical signal of the photo-optical memory provided by the embodiment of the present invention.

[0070] Refer to Figure 6 As shown, after removing the optical signal, a voltage pulse with an amplitude of 40 V and a pulse width of 100 ms is applied to the gate, and the drain current becomes 0, that is, the "erasing" of the optical signal is achieved.

[0071] Figure 7 It is a schematic diagram of the working principle of the photo-optical memory provided by the embodiment of the present invention in the entire working cycle of writing / reading after writing / erasing / reading after erasing.

[0072] One working cycle of the photo-optical memory includes the writing of optical signals, the reading after the writing of optical signals, the erasing of optical signals, and the reading after the erasing of optical signals.

[0073] Refer to Figure 7 As shown, when the applied gate-source voltage V gs = 0 and the drain-source voltage V ds = 0, after irradiating the photo-optical memory with an optical signal in the deep solar-blind ultraviolet band, the drain current increases, and the "writing" of the optical signal is achieved. After removing the optical signal, at this time, the device is in the "on" state. The gate-source voltage (V gs ) and the drain-source voltage (V ds ) of the device are set to 15 V and 5 V respectively for the "reading" operation, and the corresponding reading current is 100 nA, achieving the "reading after writing" of the optical signal.

[0074] Refer to Figure 7As shown, after removing the optical signal, an electrical pulse with an amplitude of 40 V and a pulse width of 100 ms is applied to the gate, and the drain current becomes 0, that is, the "erasure" of the optical signal is achieved. After removing the electrical pulse, the gate-source voltage (V gs ) and the drain-source voltage (V ds ) of the device are set to 15 V and 5 V respectively for the "read after erasure" operation, and the corresponding read current is 10 pA. At this time, the device is in the "off" state.

[0075] Figure 8 It is a schematic diagram of the retention characteristics of the optoelectronic memory provided by the embodiment of the present invention in two modes of "on" state and "off" state.

[0076] Figure 8 It shows the change of the drain current of the optoelectronic memory with time during optical writing ("on" state) and after write-erase operation ("off" state). Among them, the time of both the optical writing operation and the erasure operation is 100 ms. After the storage time exceeds 20000 s, the device still has a switching ratio of more than 7×10 4 , indicating that the optoelectronic memory of the embodiment of the present invention has good retention characteristics.

[0077] Figure 9 It is a schematic diagram of multi-state storage of the optoelectronic memory provided by the embodiment of the present invention.

[0078] The change of the storage state is realized by changing the number of input optical signals (optical pulses). Referring to Figure 9 shown, as the number of optical pulses increases, the drain current of the device also increases. Moreover, there is a good linear correlation between the drain current of the device and the number of optical pulses, indicating that the optoelectronic memory provided by the embodiment of the present invention has multi-state storage characteristics.

[0079] Referring to Figure 9 shown, after applying an optical pulse and the optoelectronic storage device realizes the "writing" of the optical signal, after waiting for 1200 s to read, the drain current does not decrease significantly, which also indicates that the optoelectronic memory provided by the embodiment of the present invention has good retention characteristics.

[0080] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An optoelectronic memory, characterized in that, Comprising: A substrate (1); A polarization layer (2), located on a first surface of the substrate (2), the polarization layer (2) being made of a material having a spontaneous polarization effect; and A photosensitive layer (3), located on the polarization layer (2) or between the substrate (1) and the polarization layer (2), the photosensitive layer (3) being adapted to generate photoexcited electron-hole pairs in response to an optical signal incident on the photosensitive layer (3); Wherein, the polarization layer (2) forms a built-in electric field in the photosensitive layer (3) based on the spontaneous polarization effect, and the built-in electric field is adapted to separate the photoexcited electron-hole pairs. Based on the trapping effect of the defect states of the photosensitive layer (3) on photoexcited holes, the photoelectric memory realizes the writing and non-volatile storage of the optical signal.

2. The optoelectronic memory according to claim 1, characterized in that, The spontaneous polarization intensity of the polarization layer (2) is 0.01 C / cm 2 ~1 C / cm 2 .

3. The optoelectronic memory according to claim 1, characterized in that, The material of the polarization layer (2) includes GaN, AlN, AlGaN or AlScN; Preferably, the thickness of the polarization layer (2) is 1 nm to 1000 nm.

4. The optoelectronic memory according to claim 1, characterized in that, The material of the photosensitive layer (3) is a gallium oxide semiconductor material or a doped gallium oxide semiconductor material.

5. The optoelectronic memory according to claim 1, characterized in that, The trapping effect of the defect states of the photosensitive layer (3) on photoexcited holes includes: Oxygen vacancies in the photosensitive layer (3), gallium vacancies in the photosensitive layer (3) and / or interface defect states between the photosensitive layer (3) and the polarization layer (2) are adapted to trap the photoexcited holes to inhibit the recombination of photoexcited electrons and photoexcited holes.

6. The optoelectronic memory according to claim 1, characterized in that, Further comprising: A source electrode (4) and a drain electrode (5), respectively located on the photosensitive layer (3); And A gate electrode (6), located on a second surface of the substrate (1) opposite to the first surface.

7. The optoelectronic memory according to claim 1, characterized in that, Further comprising: A source electrode (4) and a drain electrode (5), respectively located on the photosensitive layer (3); And A gate electrode (6), located on the polarization layer (2).

8. A method for preparing a photodetector according to any one of claims 1 to 7, characterized in that, Comprising: Growing a polarization layer (2) and a photosensitive layer (3) sequentially on a substrate (1); Or, growing a photosensitive layer (3) and a polarization layer (2) sequentially on a substrate (1); Wherein, the material of the polarization layer (2) has a spontaneous polarization effect.

9. A modulation method for an optoelectronic memory according to any one of claims 1 to 7, characterized in that, Comprising: Irradiating an optical signal onto the photosensitive layer of the photoelectric memory to realize the writing and non-volatile storage of the optical signal.

10. The modulation method according to claim 9, characterized in that, The optical signal is in the solar-blind ultraviolet light band.

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