A memristor based on a GaN / PEDOT:PSS planar heterojunction and a preparation method thereof

Abstract

The present invention discloses a memristor based on a GaN / PEDOT:PSS planar heterojunction and a preparation method thereof, including a substrate; a GaN thin film, the GaN thin film is p-type conductive, and the GaN thin film is attached to the surface of the substrate; a PEDOT:PSS organic layer, the PEDOT:PSS organic layer is p-type conductive, and the PEDOT:PSS organic layer is attached to the surface of the GaN thin film; a first electrode, forming an ohmic contact with the GaN thin film; and a second electrode, forming an ohmic contact with the PEDOT:PSS organic layer. Through the combined action of the space charge layer generated by the GaN / PEDOT:PSS heterojunction and the nitrogen vacancies in the GaN thin film, the present invention can realize the switching of the device resistance between the high resistance state and the low resistance state under the control of an external voltage, and realize the non-volatile writing and erasing of data.

Description

Technical Field

[0001] The present invention belongs to the technical field of microelectronic devices, and particularly relates to a memristor based on a GaN / PEDOT:PSS planar heterojunction and a preparation method thereof. Background Art

[0002] The resistive switching phenomenon of materials has attracted extensive attention in recent years, especially its application in resistive random access memories (RRAMs), which is considered to be one of the most promising emerging non-volatile memories in the industry due to its advantages such as high speed, high integration density, and low power consumption. Generally speaking, a memristive device is based on a simple capacitive structure, that is, an insulating or semiconductor material is used between two electrodes. By applying a bias voltage to the electrodes, the memristive device can be switched between at least two different states, one is the low resistance state (which can also be called the "1" state), and the other is the high resistance state (which can also be called the "0" state). If considering the position where the switching event occurs on the cross-section of the memristive element, memristors can be divided into conductive filament type and interface type. Conductive filament type resistive switching is related to the filament channels formed by metal or oxygen vacancies, while interface type resistive switching is usually related to physical or chemical phenomena occurring at the semiconductor / electrode interface or heterojunction interface.

[0003] Compared with the memristor with a simple metal-oxide-metal structure, the memristor based on heterojunction design has a wide variety of choices in the selection of constituent materials, and the device structure and composition can be flexibly adjusted by changing the heteromaterial. In addition, the heterojunction interface can generate an interface potential barrier, a depletion layer, a built-in electric field, and charge trapping effects, which have an additional adjustment function for the memristor. Constructing a heterojunction interface is one of the effective means to regulate the performance of memristors and reveal the resistive switching mechanism, and the memristors developed based on heterojunctions have unique advantages in terms of power consumption, stability, and reliability. Summary of the Invention

[0004] The purpose of this part is to outline some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this part, as well as in the abstract and title of the present application, to avoid obscuring the purpose of this part, the abstract, and the title. However, such simplifications or omissions shall not be used to limit the scope of the present invention.

[0005] In view of the above and / or problems existing in the prior art, the present invention is proposed.

[0006] One of the purposes of the present invention is to provide a memristor based on a GaN / PEDOT:PSS planar heterojunction. Through the combined action of the space charge layer generated by the GaN / PEDOT:PSS heterojunction and the nitrogen vacancies in the GaN thin film, the writing and erasing of the high / low resistance states of the memristor are realized.

[0007] To solve the above technical problems, the present invention provides the following technical solutions: A memristor based on a GaN / PEDOT:PSS planar heterojunction, comprising,

[0008] A substrate;

[0009] A GaN thin film, the GaN thin film being p-type conductive, and the GaN thin film being attached to the surface of the substrate;

[0010] A PEDOT:PSS organic layer, the PEDOT:PSS organic layer being p-type conductive, and the PEDOT:PSS organic layer being attached to the surface of the GaN thin film;

[0011] A first electrode, forming an ohmic contact with the GaN thin film; and,

[0012] A second electrode, forming an ohmic contact with the PEDOT:PSS organic layer.

[0013] As a preferred embodiment of the memristor based on a GaN / PEDOT:PSS planar heterojunction of the present invention, wherein: the material of the substrate is Al2O3.

[0014] As a preferred embodiment of the memristor based on a GaN / PEDOT:PSS planar heterojunction of the present invention, wherein: the resistivity of the GaN thin film is 0.1 to 100 Ω·cm, and the film thickness is 200 nm to 2 μm.

[0015] As a preferred embodiment of the memristor based on a GaN / PEDOT:PSS planar heterojunction of the present invention, wherein: the film thickness of the PEDOT:PSS organic layer is 10 to 300 nm, and the conductivity is 10 to 1000 S / cm.

[0016] As a preferred embodiment of the memristor based on a GaN / PEDOT:PSS planar heterojunction of the present invention, wherein: the first electrode comprises a single layer formed of one of nickel, aluminum, copper, silver, gold, platinum, titanium, gallium, indium, and scandium or a stack formed of a plurality of them.

[0017] As a preferred embodiment of the memristor based on a GaN / PEDOT:PSS planar heterojunction of the present invention, wherein: the second electrode comprises a single layer formed of one of nickel, aluminum, copper, silver, gold, platinum, titanium, gallium, indium, and scandium or a stack formed of a plurality of them.

[0018] Another object of the present invention is to provide a preparation method of the memristor based on a GaN / PEDOT:PSS planar heterojunction as described in any one of the above, comprising,

[0019] Providing a substrate;

[0020] Epitaxially grow a GaN thin film on a substrate by metalorganic chemical vapor deposition;

[0021] Spin-coat a precursor solution of a PEDOT:PSS organic layer on the surface of the GaN thin film, and evaporate the solvent to form a PEDOT:PSS organic layer;

[0022] Use magnetron sputtering technology to form a first ohmic contact electrode on the GaN thin film and a second ohmic contact electrode on the PEDOT:PSS organic layer.

[0023] As a preferred embodiment of the preparation method of the memristor based on the GaN / PEDOT:PSS planar heterojunction of the present invention, wherein: the p-type conductivity of the GaN thin film is achieved by Mg doping, and the doping concentration is 10 17 ~10 19 cm -3 .

[0024] As a preferred embodiment of the preparation method of the memristor based on the GaN / PEDOT:PSS planar heterojunction of the present invention, wherein: the precursor solution is a mixture of an aqueous solution of poly(3,4-ethylenedioxythiophene) / polystyrene sulfonate with a volume ratio of 5:1 to 50:1 and isopropanol.

[0025] As a preferred embodiment of the preparation method of the memristor based on the GaN / PEDOT:PSS planar heterojunction of the present invention, wherein: for the evaporation of the solvent, the evaporation temperature is 70 to 150 °C and the evaporation time is 5 to 20 min.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] Through the combined action of the space charge layer generated by the GaN / PEDOT:PSS heterojunction and the nitrogen vacancies in the GaN thin film, the present invention can switch the device resistance between a high resistance state and a low resistance state under the control of an external voltage, realizing non-volatile writing and erasing of data. Description of the Drawings

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings. Among them:

[0029] Figure 1 It is a schematic diagram of the result of a memristor based on a GaN / PEDOT:PSS planar heterojunction provided in Embodiment 1 of the present invention;

[0030] Figure 2 The hysteresis current-voltage curve of the memristor based on the GaN / PEDOT:PSS heterojunction provided in Embodiment 1 of the present invention.

[0031] Figure 3 The fast switching cycle characteristics of the memristor based on the GaN / PEDOT:PSS heterojunction provided in Embodiment 1 of the present invention.

[0032] Figure 4 The resistance state retention characteristics of the memristor based on the GaN / PEDOT:PSS heterojunction provided in Embodiment 1 of the present invention. Detailed implementation manners

[0033] To make the above objects, features, and advantages of the present invention more obvious and understandable, the following describes the detailed implementation manners of the present invention in conjunction with the embodiments of the specification.

[0034] In the following description, many specific details are set forth to facilitate a thorough understanding of the present invention. However, the present invention may be implemented in other ways different from those described herein. Those skilled in the art can make similar generalizations without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0035] Secondly, the so-called "one embodiment" or "embodiment" refers to specific features, structures, or characteristics that may be included in at least one implementation manner of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that excludes other embodiments.

[0036] Unless otherwise specified, the raw materials used in the embodiments are commercially purchased. Unless otherwise specified, the means involved in the embodiments are conventional technical means in the art.

[0037] Embodiment 1

[0038] As Figure 1 shown, a memristor based on a GaN / PEDOT:PSS planar heterojunction provided in this Embodiment 1 includes a p-type conductive GaN thin film 200 grown on an Al2O3 substrate 100, a p-type conductive PEDOT:PSS organic layer 300 deposited on the GaN thin film 200, a first electrode 400 that forms an ohmic contact with the GaN thin film 200, and a second electrode 500 that forms an ohmic contact with the PEDOT:PSS organic layer 300.

[0039] The specific preparation method of the above memristor based on the GaN / PEDOT:PSS planar heterojunction is as follows:

[0040] (1) The p-type GaN thin film doped with Mg element was epitaxially grown on the Al2O3 substrate by metal-organic chemical vapor deposition. Using metal-organic bis(cyclopentadienyl)magnesium (Cp2Mg) as the doping metal source, the Mg element doping of the GaN epitaxial thin film was prepared to achieve p-type conductivity of the GaN thin film. The doping concentration of Mg element was controlled by regulating the flow rate of the metal-organic source bis(cyclopentadienyl)magnesium. The Mg doping concentration of the prepared GaN thin film was about 10 18 cm -3 , and the resistivity of the p-type GaN thin film prepared by the above method was about 1 Ω·cm.

[0041] (2) The GaN thin film was cut into a square substrate of 10*10 mm 2 , and was cleaned with acetone, alcohol and deionized water for later use.

[0042] (3) The aqueous solution of poly(3,4-ethylenedioxythiophene) / poly(styrenesulfonate) was filtered with a 0.24-μm aqueous filter, and a precursor solution of the p-type PEDOT:PSS organic layer was prepared by mixing it with isopropanol at a volume ratio of 10:1.

[0043] (4) Based on the solution spin-coating method, the GaN thin film was partially masked with a mask plate first, and the precursor solution of the PEDOT:PSS organic layer was spin-coated on the masked GaN thin film. The precursor solution was a mixture of an aqueous solution of poly(3,4-ethylenedioxythiophene) / poly(styrenesulfonate) and isopropanol with a volume ratio of 10:1; then it was heated on a hot stage at 100 °C for 10 min to evaporate the organic solvent to obtain the PEDOT:PSS organic layer; the mask layer on the GaN was removed, thus obtaining the GaN / PEDOT:PSS organic-inorganic planar heterojunction.

[0044] (5) Using magnetron sputtering and a mask plate, square array titanium-gold electrodes of 1*1 mm 2 were prepared on the PEDOT:PSS surface and the GaN surface of the heterojunction to obtain the heterojunction memristive device.

[0045] Example 2

[0046] A group of electrodes with adjacent heterointerfaces were selected for the electrical property test of the memristor, and the obtained hysteresis current-voltage curve was as Figure 2 shown. Whether the voltage sweep test was carried out under negative bias or positive bias, a current hysteresis loop could be obtained, indicating that the GaN / PEDOT:PSS planar heterojunction memristor we prepared was a bipolar memristor.

[0047] There are two processes of set and reset in the device:

[0048] (1) When the bias voltage is gradually swept from 0 V to -10 V, the device current gradually increases. When the bias voltage exceeds a certain threshold, the interface electron high-speed transmission channel will be turned on. Even if the bias voltage is then swept back from -10 V to 0 V, the device can maintain a low-resistance state ("1" state) in a relatively large voltage range. This process of changing from a low-resistance state ("0" state) to a high-resistance state ("1" state) is called setting;

[0049] (2) When the bias voltage is gradually swept from 0 V to 10 V, the device current is relatively large and the device is in a low-resistance state ("1" state). When the bias voltage is swept back from 10 V to 0 V, the device current significantly decreases and the device is in a high-resistance state ("0" state). This process of changing from a high-resistance state ("1" state) to a low-resistance state ("0" state) is called resetting. By controlling the voltage as described above, the writing and reading of the high and low resistance states of the GaN / PEDOT:PSS planar heterojunction memristor can be achieved, realizing the data storage function.

[0050] To verify the stability and reliability of the device, further switching cycle tests and retention tests of the memristive characteristics of the device were carried out. The switching cycle test is as Figure 3 shown. 150 switching cycles were performed on the device. The high-resistance state resistance value of the device is 5.95×10 9 Ω, and the low-resistance state resistance value is 3.88×10 6 Ω. The switching ratio remains at about 1.53×10 3 , showing good stability. The retention test of the device is as Figure 4 shown. Even when the working time exceeds 10080 s, the device still maintains a switching ratio of more than 10 3 , demonstrating excellent reliability.

[0051] According to the test results of the embodiment, it shows that the GaN / PEDOT:PSS planar heterojunction memristor prepared according to the present invention is a bipolar memristor, having excellent storage performance, a large switching ratio, good retention, and high stability, and is suitable for scientific research and commercial development.

[0052] By using Mg-doped p-type GaN thin films and an improved p-type PEDOT:PSS organic layer, the present invention constructs a GaN / PEDOT:PSS organic-inorganic planar heterojunction, providing a memristive device with a large switching ratio, high stability, and strong reliability. The realization of this planar heterojunction type memristor not only provides a new device structure solution but also enriches the types of materials that make up the memristor. At the same time, the constructed GaN / PEDOT:PSS organic-inorganic planar heterojunction forms a space charge layer due to the diffusion of electrons and holes. Together with the nitrogen vacancy defects in the GaN thin film, the space charge layer can open and close the high-speed electron transport channel at the heterojunction interface under the influence of an external bias voltage, obtaining the low-resistance state and high-resistance state of the device. Based on the efficient blocking and opening effects of the built-in electric field at the interface, the GaN / PEDOT:PSS organic-inorganic planar heterojunction memristor provided by the present invention achieves a high-to-low resistance state ratio of more than 1000, a stability with unchanged performance after more than 150 cycle switches, and an ultra-long retention time of more than 10 4 seconds. The GaN / PEDOT:PSS planar heterojunction memristor provided by the present invention has a simple preparation process, a large switching ratio, and excellent retention, and has important commercial and scientific value.

[0053] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A memristor based on a GaN / PEDOT:PSS planar heterojunction, characterized in that: Comprising, a substrate (100); A GaN thin film (200), the GaN thin film (200) is p-type conductive, the GaN thin film (200) is attached to the surface of the substrate (100), wherein, the resistivity of the GaN thin film (200) is 0.1~100 Ω·cm, the film thickness is 200 nm~2 µm, the p-type conductive property of the GaN thin film is achieved by Mg doping, and the doping concentration is 10 17 ~10 19 cm -3 ; a PEDOT:PSS organic layer (300), the PEDOT:PSS organic layer (300) being p-type conductive, the PEDOT:PSS organic layer (300) adhering to the surface of the GaN thin film (200), wherein the film thickness of the PEDOT:PSS organic layer (300) is 10 - 300 nm and the conductivity is 10 - 1000 S / cm; a first electrode (400) forming an ohmic contact with the GaN thin film (200); and, a second electrode (500) forming an ohmic contact with the PEDOT:PSS organic layer (300).

2. The memristor based on the GaN / PEDOT:PSS planar heterojunction according to claim 1, characterized in that: The material of the substrate (100) is Al2O3.

3. The memristor based on the GaN / PEDOT:PSS planar heterojunction according to claim 1, characterized in that: The first electrode (400) comprises a single layer formed of one of nickel, aluminum, copper, silver, gold, platinum, titanium, gallium, indium, and scandium or a stack formed of a plurality thereof.

4. The memristor based on the GaN / PEDOT:PSS planar heterojunction according to claim 3, wherein: The second electrode (500) comprises a single layer formed of one of nickel, aluminum, copper, silver, gold, platinum, titanium, gallium, indium, and scandium or a stack formed of a plurality thereof.

5. The preparation method of the memristor based on the GaN / PEDOT:PSS planar heterojunction according to any one of claims 1 to 4, characterized in that: Comprising, providing a substrate; epitaxially growing a GaN thin film on the substrate by metalorganic chemical vapor deposition; spin-coating a precursor solution of the PEDOT:PSS organic layer on the surface of the GaN thin film and evaporating the solvent to form the PEDOT:PSS organic layer; using magnetron sputtering technology to form a first electrode with an ohmic contact on the GaN thin film and a second electrode with an ohmic contact on the PEDOT:PSS organic layer.

6. The preparation method of the memristor based on the GaN / PEDOT:PSS planar heterojunction according to claim 5, characterized in that: The precursor solution is a mixture of an aqueous solution of poly(3,4-ethylenedioxythiophene) / polystyrene sulfonate and isopropyl alcohol with a volume ratio of 5:1 - 50:

1.

7. The preparation method of the memristor based on the GaN / PEDOT:PSS planar heterojunction according to claim 6, characterized in that: For evaporating the solvent, the evaporation temperature is 70 - 150 °C and the evaporation time is 5 - 20 min.

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