CN114497267A - TMDCs-based electric field induced Schottky photodiode and preparation method thereof - Google Patents
TMDCs-based electric field induced Schottky photodiode and preparation method thereof Download PDFInfo
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Abstract
The invention provides an electric field induction Schottky photodiode based on two-dimensional transition metal chalcogenide (TMDCs) and a preparation method thereof, the Schottky photodiode sequentially comprises a conductive substrate (101-1), an insulating medium layer (101-2) and a two-dimensional transition metal chalcogenide TMDCs layer (201) from bottom to top, and a source electrode (301-1) and a drain electrode (301-2) which are both made of metal materials are respectively arranged on the two-dimensional transition metal chalcogenide TMDCs layer (201). When voltage is applied to the drain electrode, the carrier concentration of TMDCs below the metal contact is regulated and controlled by a longitudinal electric field between the drain electrode and the conductive substrate, and the Schottky barrier height at the drain electrode is changed, so that the switching characteristic of the Schottky diode is realized. Under the illumination, the photon-generated carriers are separated under the action of a transverse electric field between the source electrode and the drain electrode to form a photoelectric signal.
Description
Technical Field
The invention belongs to the technical field of photoelectric detection, and particularly relates to an electric field induced Schottky photodiode based on transition metal chalcogenide (TMDCs) and a preparation method thereof.
Background
The photoelectric detector is based on the influence of light radiation on materials, changes of electrical parameters such as conductivity and the like, so that the purpose of converting optical signals into electric signals is achieved, and optical communication, biomedical imaging, atmospheric quality detection spectrum and the like are all concrete embodiments of application of photoelectric detection technology. Due to the unique physical properties and energy band structures of the TMDCs (such as thin thickness and weak charge shielding of the TMDCs, strong light absorption of the TMDCs compared with a bulk material with the same thickness and the like), the TMDCs have huge application prospects in the aspects of new-generation photoelectric detection and other photoelectric applications.
The photoelectric detector based on TMDCs mainly has three device structures of a resistance type (photoconductor), a field-effect transistor type (photofield effect transistor) and a diode type (photodiode). Due to the existence of a built-in electric field of the photodiode, photogenerated excitons are easy to separate in a depletion region and tend to have higher response speed, and meanwhile, due to the property of a high resistance state of a junction region, the off-state dark current of the photodiode is lower, so that the detection sensitivity of the photodiode is greatly improved. The preparation of the photodiode at present mainly depends on the control doping to control the generation of the P-type and N-type TMDCs, and the control modes mainly include electrostatic doping, chemical doping, plasma doping, laser doping and the like, wherein the electrostatic doping control is reversible and does not damage the material per se, so that the material generates additional defects. At present, the technology based on electrostatic doping mainly comprises ionic liquid regulation and discrete grid regulation, the ionic liquid is unstable at normal temperature, the preparation process of a discrete grid device is complicated, the success rate is low, and meanwhile, the photoelectric detection application is greatly limited due to the fact that the junction coupling generated by the regulation is too weak and the reverse dark current is too high.
Disclosure of Invention
Aiming at the defects and technical difficulties of the existing photodiode preparation by utilizing electrostatic regulation, the invention innovatively provides an electric field induced Schottky photodiode based on two-dimensional transition metal chalcogenide (TMDCs) and a preparation method thereof. The method comprises the steps of preparing a TMDCs film on a conductive substrate covered with a thin layer of insulating medium, depositing metal on the surface of the TMDCs to prepare source and drain electrodes, etching away part of the insulating medium beside a source electrode to form an insulating medium window exposing the conductive substrate, and finally connecting the bottom conductive substrate with the source electrode by depositing the metal to form one end of a Schottky diode, wherein the end is zero-biased or grounded, and a drain electrode which is not connected to the conductive substrate is used as the other end of the Schottky diode. When voltage is applied to the drain electrode, the carrier concentration in TMDCs below the drain terminal electrode is regulated and controlled by a longitudinal electric field between the drain electrode and the conductive substrate, and the Schottky barrier height at the drain electrode is changed, so that the switching characteristic of the Schottky diode is realized. Under illumination, the photo-generated carriers are separated under the action of a transverse electric field between the source electrode and the drain electrode to form photoelectric signals.
In order to achieve the above object, according to one aspect of the present invention, the present invention provides a two-dimensional transition metal chalcogenide (TMDCs) -based electric field induced schottky photodiode, characterized in that the schottky photodiode comprises, in order from bottom to top, a conductive substrate (101-1), an insulating dielectric layer (101-2), and a two-dimensional transition metal chalcogenide TMDCs layer (201), wherein a source electrode (301-1) and a drain electrode (301-2) both made of a metal material are further disposed on the two-dimensional transition metal chalcogenide TMDCs layer (201); wherein the two-dimensional transition metal chalcogenide TMDCs layer (201) is intrinsic undoped or doped with a concentration of not more than 1018cm-3The doping state of (a); the source electrode (301-1) and the conductive substrate (101-1) are equal in potential, the insulating medium layer (101-2) is used as a gate medium, and the drain electrode (301-2) and the source electrode (301-1) are respectively in contact with the two-dimensional transition metal chalcogenide TMDCs layer (201) to form a Schottky barrier; the gate capacitance of the insulating medium layer (101-2) is not less than 1.4 x 10-7F/cm2By applying voltages with different polarities to the drain electrode (301-2), the longitudinal electric field between the drain electrode (301-2) and the conductive substrate (101-1) can regulate and control the carrier concentration and polarity of TMDCs (transition metal oxides) contacting with the drain electrode (301-2), so that the Fermi level of the TMDCs at the contact part is changed, and finally the Schottky barrier size at the drain end is changed, and the effect is realizedThe rectification and the switching action of the diode are realized; besides, the photon-generated carriers can be separated under the action of a transverse electric field between the source and the drain to output photoelectric signals, so that photoelectric detection is realized.
As a further preferable mode of the present invention, the source electrode (301-1) is connected to the conductive substrate (101-1) through a communication contact electrode layer (401), and the source electrode (301-1) and the conductive substrate (101-1) are always kept at zero bias voltage or grounded.
As a further preferable aspect of the present invention, the schottky diode is an electron type schottky diode, and the barrier height at which electrons are injected from the drain (301-2) and the source (301-1) into the TMDCs in a thermal equilibrium state is not less than 0.2 eV;
alternatively, the Schottky diode is a hole type Schottky diode, and the barrier height of holes injected into TMDCs from the drain (301-2) and the source (301-1) is not less than 0.2eV in a thermal equilibrium state.
In a further preferred embodiment of the present invention, the thickness of the two-dimensional transition metal chalcogenide TMDCs layer (201) is 1nm to 100 nm.
In a further preferred embodiment of the present invention, the transition metal chalcogenide used in the two-dimensional transition metal chalcogenide TMDCs layer (201) is MoS2、MoSe2、MoTe2、WS2、WSe2Or any one of ternary and higher compound crystals composed of them.
As a further preferred embodiment of the present invention, the schottky diode is a single device or a periodic array structure.
According to another aspect of the present invention, there is provided a method for manufacturing the above-mentioned TMDCs-based electric field induced schottky photodiode, comprising the steps of:
(1) providing a conductive substrate with a thin-layer insulating medium covered on the surface, wherein a TMDCs film is arranged on the thin-layer insulating medium;
(2) carrying out patterning treatment on the TMDCs thin film by adopting a photoetching process to form a window for exposing part of the TMDCs thin film;
(3) depositing metal on the surface of the TMDCs thin film graphic structure to form an electrode layer, thereby forming source and drain electrodes which are respectively connected with two ends of a target conductive channel region;
(4) patterning the formed area beside the source electrode by adopting a photoetching process again to form a window for exposing a part of the thin-layer insulating medium film;
(5) etching the thin-layer insulating medium pattern structure by taking the photoresist as a mask to form a window for exposing part of the conductive substrate;
(6) patterning the window and the source electrode which form the exposed conductive substrate by adopting a photoetching process again to form a window for communicating the conductive substrate and the source electrode;
(7) and depositing metal on the patterned window by taking the photoresist as a mask to realize the communication between the conductive substrate and the source electrode.
Further preferably, in the step (1), the thin insulating medium is SiO2、Al2O3、HfO2、TiO2、ZrO2、Y2O3、La2O3、Ta2O5And boron nitride or a composite structure thereof, wherein the thickness of the insulating layer is 2-200nm, and the gate capacitance of the insulating layer is not less than 1.4 × 10-7F/cm2(ii) a The conductive substrate is conductive metal Au, Al and Cu or a heavily doped semiconductor, preferably heavily doped P-type or N-type Si; wherein the doping concentration corresponding to the heavy doping is not less than 1019cm-3；
In the step (1), the TMDCs thin film is transferred to a conductive substrate by a dry method or a wet method, or is obtained by directly carrying out TMDCs thin film growth on the conductive substrate by a Chemical Vapor Deposition (CVD) method;
in the step (1), the TMDCs thin film layer is MoS2、MoSe2、MoTe2、WS2、WSe2One of them or any one of ternary and above compound crystal composed of them, the thickness of the TMDCs film is between 1nm-100 nm;
in the step (1), the TMDCs are intrinsic undoped or doped with a concentration not higher than 1018cm-3The doping state of (a);
in the step (5), the etching process is a dry etching process or a wet etching process; preferably, the dry etching is Reactive Ion Etching (RIE).
Compared with the existing photodiode generated by electrostatic regulation, the method has the advantages that the process is simplified, a fixed-point transfer technology is not needed, and the success rate of the device under the structure is greatly improved. Meanwhile, it is proposed for the first time that a longitudinal electric field is used to induce and generate a schottky diode, and by the strong regulation and control action of a thin-layer insulating medium, carriers regulated and controlled by a field effect under a small applied voltage will obviously change the fermi level of TMDCs (transition metal oxides) in a metal electrode (e.g., drain) contact region, thereby affecting the schottky barrier in the contact region, and realizing the on and off of a device under voltages of different polarities (that is, based on the invention, the gate capacitance of an insulating layer is not less than 1.4 × 10-7F/cm2Under the condition of (1.5) V, the carrier concentration of TMDCs in the metal electrode contact region is effectively changed by applying a small voltage, for example, ± 1.5V, so as to affect the schottky barrier of the contact region, thereby realizing the on/off of the device under voltages with different polarities). In the preparation, the bottom part of the insulating medium is also skillfully designed to be etched, so that the electrode at one end of the top part is communicated with the conductive substrate at the bottom part, and the device which needs three-end input originally is changed into two-end input, which is beneficial to the preparation of large-area integration of the structure. The TMDCs have a layered structure, the thickness of a single layer is less than 1nm, and the small-layer nano-scale TMDCs material can be easily prepared by a micro-mechanical stripping technology. And under the same thickness, the absorptivity of the two-dimensional TMDCs to light is far higher than that of the traditional thin layer material.
Compared with the means of ionic liquid regulation and discrete gate regulation in the prior art, the method is based on the doping principle of electrostatic doping, but the overall structure design of the device has obvious advantages. Specifically, on the one hand, compared with the regulation and control of the ionic liquid, the regulation and control of the invention can work stably at normal temperature, while the ionic liquid is unstable at normal temperature and can only work at low temperature; meanwhile, the device is controlled by a bottom electric field, the surface of the material can realize the whole-domain lossless light absorption, and the ionic liquid generally covers the surface of the material and has a certain reflection effect on light, so that the photoelectric performance of the device is influenced. On the other hand, compared with the discrete gate regulation, the device preparation process does not involve a complex fixed-point transfer process, the yield of device preparation is ensured, and meanwhile, impurities introduced in the transfer process cannot occur to influence the performance of the device. Meanwhile, the device adopting the discrete gate control structure belongs to a multi-terminal device, and relates to a plurality of voltage input ends, so that the complexity of circuit design is increased.
The invention can form larger barrier of electron or hole especially by using metal with preferable work function requirement as drain-source electrode, taking electron type schottky diode (i.e. schottky barrier of schottky diode is electron barrier type) as an example, under thermal equilibrium state, the barrier height of electron injected into TMDCs from drain metal and source metal is preferably not less than 0.2eV, so that electron injected into TMDCs from source end is blocked under forward bias of drain end, to ensure that schottky diode has good reverse cut-off characteristic; and for a hole type schottky diode (i.e., the schottky barrier of the schottky diode is a hole barrier type), the barrier height of holes injected into the TMDCs from the drain metal and the source metal in a thermal equilibrium state is preferably not less than 0.2eV, so that the injection of holes into the TMDCs from the source under a drain-side reverse bias is blocked to ensure that the schottky diode has a good reverse blocking characteristic. Further, the barrier height can be further expanded under the regulation and control of the longitudinal electric field, so that compared with most of photodiodes regulated and controlled by static electricity, the electric field induced Schottky photodiode based on TMDCs has relatively smaller off-state dark current, and the device performance is improved. In addition, the novel field-induced Schottky photodiode process is compatible with a mainstream semiconductor planar process, and is expected to be periodically integrated on a chip of a conventional semiconductor in an array manner.
Drawings
Fig. 1 is a schematic plane view of an electric field induced schottky photodiode based on two-dimensional transition metal chalcogenides (TMDCs) in embodiment 1 of the present invention.
Fig. 2 is a schematic cross-sectional view of a two-dimensional transition metal chalcogenide (TMDCs) -based electric field induced schottky photodiode according to embodiment 1 of the present invention.
Fig. 3 is a schematic plane view of a periodic array of electric field induced schottky photodiodes based on two-dimensional transition metal chalcogenides (TMDCs) in embodiment 2 of the present invention.
Fig. 4 is a graph showing actually measured output characteristics of the two-dimensional transition metal chalcogenide (TMDCs) -based electric field induced schottky photodiode in the dark state according to example 1 of the present invention.
Fig. 5 is a graph showing the output characteristics of the two-dimensional transition metal chalcogenide (TMDCs) -based electric field induced schottky photodiode according to embodiment 1 of the present invention as a function of light intensity. The curves in the graph are sequentially from bottom to top corresponding to increasing light intensity, i.e. from dark state (dark) and light intensity of 0.5mW cm-2Continuously increasing until the light intensity is 10175mW cm-2。
The meanings of the reference symbols in the figures are as follows:
101-1 conductive substrate
101-2 insulating dielectric layer
201 TMDCs thin film layer
301-1 source electrode
301-2 drain electrode
401 communicating the conductive substrate with the electrode of the source terminal (i.e., communicating the contact electrode layer)
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
Generally speaking, the invention prepares a TMDCs film on a conductive substrate covered with a thin layer of insulating medium, deposits metal on the surface of the TMDCs to prepare a source electrode and a drain electrode, then etches away part of the insulating medium beside the source electrode to form an insulating medium window exposing the conductive substrate, finally deposits metal to connect the bottom conductive substrate and the source electrode to form one end of a Schottky diode, wherein the end is zero-biased or grounded, and a drain electrode which is not connected with the conductive substrate is used as the other end of the Schottky diode. By utilizing the strong grid control capability of the thin-layer insulated gate dielectric, when voltage is applied to the drain electrode, the concentration and polarity of carriers in TMDCs (transition metal oxides) below the contact of the drain end metal electrode are induced to change by a longitudinal electric field between the drain electrode and the conductive substrate, and the Schottky barrier height at the drain electrode is changed, so that the switching characteristic (namely, the rectification characteristic) of the Schottky diode is realized. The change of the Schottky barrier of the Schottky diode mainly exists between TMDCs and drain metal, carriers are injected from the drain under forward conduction, and the barrier at the source is not influenced by the voltage of a drain terminal. Under illumination, the photo-generated carriers are separated under the action of a transverse electric field between the source electrode and the drain electrode to form photoelectric signals.
Fig. 1 and 2 are schematic views of an electric field induced schottky photodiode based on two-dimensional transition metal chalcogenides (TMDCs) according to the present invention. Fig. 3 is a schematic plane structure diagram of a periodic array of two-dimensional transition metal chalcogenide (TMDCs) -based electric field induced schottky photodiodes according to the present invention. It should be noted that the drawings provided in the present embodiment are only for illustrating the basic idea of the present invention, and the drawings only show the components related to the present invention rather than being drawn according to the number, shape and size of the components actually implemented, and the types, the numbers and the proportions of the components can be changed and the layout of the components can be more complicated.
Example 1:
as shown in fig. 1 and 2, the two-dimensional transition metal chalcogenide (TMDCs) -based electric field induced schottky photodiode according to the present embodiment at least includes: the substrate comprises a conductive base 101-1 (which can be obtained by heavily doping a semiconductor wafer, and can also be conductive metal Au, Al, Cu and the like), and an insulating medium layer 101-2 positioned on the surface of the conductive base 101-1; a TMDCs thin film layer 201; a source electrode 301-1 in communication with the bottom conductive substrate; a voltage applied drain 301-2 for connecting the bottom conductive substrate to the top source electrode 401. Of course, in addition to providing the through contact electrode layer 401, the source electrode 301-1 and the conductive substrate 101-1 may be grounded, respectively, as long as the potentials of the two are equal.
The method for manufacturing a two-dimensional transition metal chalcogenide (TMDCs) -based electric field induced schottky photodiode according to this embodiment at least includes:
step S1, providing a conductive substrate covered with a thin layer of insulating medium, and forming a TMDCs film on the conductive substrate;
the TMDCs thin film can be formed by transferring a TMDCs thin film layer to a conductive substrate by a dry method or a wet method, or can be formed by directly carrying out TMDCs thin film growth on a target conductive substrate by a Chemical Vapor Deposition (CVD) (similar to the conventional requirement of CVD, the temperature resistance of an insulating medium needs to be paid attention at the moment);
optionally, the conductive substrate 101-1 may be a conductive metal of Au, Al, Cu or a heavily doped semiconductor such as P++Si, N of++Si (heavily doped doping concentration can be controlled to be generally not less than 10)19cm-3)；
Optionally, the insulating dielectric layer 101-2 is an oxide material SiO2、Al2O3、HfO2、TiO2、ZrO2、Y2O3、La2O3And Ta2O5Or a composite structure of them, or boron nitride h-BN, the thickness of the insulating layer is 2-200nm, and the gate capacitance of the insulating layer is not less than 1.4 x 10-7F/cm2(similar to a capacitance calculation formula of a plate capacitance model, the higher the dielectric constant of an insulating dielectric material is, the thinner the thickness of the insulating dielectric layer 101-2 is, the higher the gate capacitance is, and the stronger the gate control capability is; the invention has no hard requirements on the type and the thickness of an insulating gate dielectric, and only needs the gate capacitance of an insulating layer to meet the requirements);
optionally, in the step (1), the TMDCs thin film layer may be MoS2、MoSe2、MoTe2、WS2、WSe2One of them or any one of ternary and above compound crystal composed of them, the thickness of the TMDCs film is between 1nm-100 nm;
in the step (1), the TMDCs should be in an intrinsic undoped or doped state, and if the doping concentration is not higher than 1018cm-3；
In this embodiment, the insulating substrate is made of P-type heavily doped silicon as the conductive base 101-1, 20nm atomic layer deposition HfO2As a thin insulating dielectric layer 101-2. Preparation of multilayer (20nm) WS on the above-described insulating substrate 101 by dry transfer mechanical lift-off2And the intrinsic thin film is used as a two-dimensional TMDCs thin film layer to prepare the electronic Schottky diode.
Step S2, carrying out graphical processing on the TMDCs film by adopting a photoetching process to form a window for exposing part of the TMDCs film, which specifically comprises the following steps:
forming photoresist on the surface of the two-dimensional TMDCs layer, exposing the photoresist layer through a photomask of a visual domain designed by relevant software, developing by using a corresponding developing solution, and imaging the photoresist;
for example, it may specifically be: step S201, in WS2Spin-coating S1815 photoresist on the surface, spin-coating 500 rpm for 5S, spin-coating 4000 rpm for 60S to form a photoresist film layer with a thickness of about 1500nm, and drying at 110 ℃ for 3 min;
step S202, photoetching, exposing the photoresist through a photomask with a preset layout, wherein the exposure dose is 40mJ/cm2And fixing in a large amount of deionized water immediately after development for 20 seconds, thereby forming a pattern structure on the photoresist.
Step S3, depositing metal on the surface of the TMDCs film pattern structure to form an electrode layer, thereby forming source and drain electrodes 301-1 and 301-2 respectively connected with two ends of the target conductive channel region, specifically:
depositing metal by using the graphical photoresist as a mask and adopting a physical vapor deposition method, and then removing the photoresist by using a photoresist solution to form a metal electrode layer;
in this embodiment, electron beam evaporation of a stack of 20nm Ti and 100nm Au is used, followed by photoresist stripping to form N-type contact electrode layers (i.e., source 301-1 and drain 301-2).
Step S4, performing patterning processing on the formed region beside one of the electrodes by using the photolithography process again to form a window exposing a part of the thin insulating medium, specifically:
spin-coating photoresist on the surface of the TMDCs layer on which the metal contact electrode is formed, exposing the photoresist layer by using a photomask with a preset layout, and then developing and patterning the photoresist;
for example, it may specifically be:
step S401, in WS2Spin-coating S1815 photoresist on the surface, spin-coating 500 rpm for 5S, spin-coating 4000 rpm for 60S to form a photoresist film layer with a thickness of about 1500nm, and drying at 110 ℃ for 3 min;
step S402, photoetching, exposing the photoresist through a photomask with a preset layout, wherein the exposure dose is 40mJ/cm2And fixing in a large amount of deionized water immediately after development for 20 seconds, thereby forming a pattern structure on the photoresist.
Step S5, using the photoresist as a mask, etching the thin insulating medium pattern structure to form a window exposing part of the conductive substrate, specifically:
taking the patterned photoresist as a mask, and adopting surface treatment methods such as a wet etching process or a reactive ion etching process to enable the insulating dielectric layer in the window area to generate physical or chemical changes so as to remove the insulating dielectric layer and expose the conductive substrate at the bottom; the etching process can be flexibly adjusted, and only the insulating medium at the window needs to be completely corroded so that the bottom conductive substrate is exposed on the surface;
in the present embodiment, the reactive ion etching process is used, and the reaction gas is SF6The flow rate is 60sccm, the cavity gas pressure is set to 10mtorr, the power is set to 100W, the reaction time is 60s, and the patterned photoresist is used as a mask to perform etching processing on the window area.
Step S6, performing patterning processing on the exposed conductive substrate window and the source electrode by using the photolithography process again to form a window for communicating the conductive substrate and the source electrode, specifically:
spin-coating a photoresist on the surface on which the etching window is formed, exposing the photoresist layer by using a photomask with a preset layout, then developing and patterning the photoresist;
for example, it may specifically be:
step S601, in WS2Spin-coating S1815 photoresist on the surface, spin-coating 500 rpm for 5S, spin-coating 4000 rpm for 60S to form a photoresist film layer with a thickness of about 1500nm, and drying at 110 ℃ for 3 min;
step S602, performing photoetching, namely exposing the photoresist through a photomask with a preset layout, wherein the exposure dose is 40mJ/cm2And fixing in a large amount of deionized water immediately after development for 20 seconds, thereby forming a pattern structure on the photoresist.
And 7, depositing metal on the graphical window by taking the photoresist as a mask to realize the communication between the conductive substrate and the source electrode, wherein the method specifically comprises the following steps:
depositing metal by using the graphical photoresist as a mask and adopting a physical vapor deposition method, and then removing the photoresist by using a photoresist solution to form a metal electrode layer;
the second-time deposited metal material (i.e., the material used for communicating the conductive substrate with the electrode 401 at the source end) is not limited, and mainly plays a role in conducting without considering the matching problem of work functions;
in this embodiment, 100nm Au is evaporated by electron beam, and then photoresist is removed to form the connection contact electrode layer 401.
And (4) carrying out performance detection on the prepared electronic Schottky diode. Fig. 4 shows the actually measured output characteristics of the device under the dark state condition, and fig. 5 shows the variation of the output characteristics of the device with the light intensity.
Taking FIG. 4 as an example, when Vds<At 0 (i.e., reverse bias), electrons are injected from the drain into the TMDCs, the schottky barrier between the drain and the TMDCs layer is reduced (compared to the thermal equilibrium state), and | VdsThe larger the I, thedsThe larger the size, the on state of the device; when V isds>At 0 (i.e. forward bias)) Electrons are injected into the TMDCs from the source electrode, but the electrons are influenced by the Schottky barrier between the source metal and the TMDCs layer, the injection of the electrons into the TMDCs from the source electrode is blocked, and the Schottky barrier height of the source electrode is not influenced by VdsInfluence with VdsIncrease of (I)dsThe increase is slow, and the device is in an off state.
Example 2:
as shown in fig. 3, based on the present invention, a periodic array of two-dimensional transition metal chalcogenides (TMDCs) -based electric field induced schottky photodiodes can be further constructed, which is mainly different from embodiment 1 in that embodiment 1 has only 1 target conducting channel region, but this embodiment can construct a plurality of target conducting channel regions on the same TMDCs thin film layer region by using the cross distribution of the source 301-1 and the drain 301-2, thereby obtaining a periodic array of schottky photodiodes.
The above embodiments are merely examples, and for example, the metal material forming the schottky barrier and the TMDCs semiconductor material may be modified as long as the drain metal and the source metal respectively form schottky contacts with the TMDCs, and the schottky barrier against electrons is provided. In addition, besides the electronic schottky diode, the hole schottky diode can be obtained based on the invention, and at the moment, the schottky barrier formed by the contact of the metal and the TMDCs semiconductor material is only required to be adjusted to be matched with the hole carriers (similarly, the barrier height of holes injected into the TMDCs from the drain metal and the source metal in a thermal equilibrium state is preferably not less than 0.2eV, so that the injection of the holes into the TMDCs from the source under the negative bias of the drain terminal is blocked, and the schottky diode is ensured to have good reverse cut-off characteristic).
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (8)
1. Electric field induction schottky barrier based on two-dimensional transition metal chalcogenide (TMDCs)The Schottky photodiode is characterized by comprising a conductive substrate (101-1), an insulating medium layer (101-2) and a two-dimensional transition metal chalcogenide TMDCs layer (201) from bottom to top in sequence, wherein a source electrode (301-1) and a drain electrode (301-2) which are made of metal materials are respectively arranged on the two-dimensional transition metal chalcogenide TMDCs layer (201); wherein the two-dimensional transition metal chalcogenide TMDCs layer (201) is intrinsic undoped or doped with a concentration of not more than 1018cm-3The doping state of (a); the source electrode (301-1) and the conductive substrate (101-1) are equal in potential, the insulating medium layer (101-2) is used as a gate medium, and the drain electrode (301-2) and the source electrode (301-1) are respectively in contact with the two-dimensional transition metal chalcogenide TMDCs layer (201) to form a Schottky barrier; the gate capacitance of the insulating medium layer (101-2) is not less than 1.4 x 10-7F/cm2By applying voltages with different polarities to the drain electrode (301-2), the longitudinal electric field between the drain electrode (301-2) and the conductive substrate (101-1) can regulate and control the carrier concentration and polarity of TMDCs (transition metal oxides) contacting with the drain electrode (301-2), so that the Fermi level of the TMDCs at the contact part is changed, and finally the Schottky barrier size at the drain end is changed, and the rectification and switching action of the diode is realized; besides, the photon-generated carriers can be separated under the action of a transverse electric field between the source and the drain to output photoelectric signals, so that photoelectric detection is realized.
2. The TMDCs-based field induced schottky photodiode of claim 1, wherein the source electrode (301-1) is connected to the conductive substrate (101-1) through a via contact electrode layer (401), and the source electrode (301-1) and the conductive substrate (101-1) are always maintained at zero bias voltage or grounded.
3. The TMDCs-based electric field induced schottky photodiode of claim 1 wherein the schottky diode is an electron type schottky diode having a barrier height for electrons injected from the drain (301-2) and source (301-1) into TMDCs of no less than 0.2eV at thermal equilibrium;
alternatively, the Schottky diode is a hole type Schottky diode, and the barrier height of holes injected into TMDCs from the drain (301-2) and the source (301-1) is not less than 0.2eV in a thermal equilibrium state.
4. The tmds-based electric field induced schottky photodiode of claim 1, wherein the thickness of the two-dimensional transition metal chalcogenide tmds layer (201) is 1nm to 100 nm.
5. The tmds-based field induced schottky photodiode of claim 1, wherein the transition metal chalcogenide used for the two-dimensional transition metal chalcogenide tmds layer (201) is MoS2、MoSe2、MoTe2、WS2、WSe2Or any one of ternary and higher compound crystals composed of them.
6. The TMDCs-based electric field induced Schottky photodiode of any one of claims 1-5, wherein the Schottky diode is a single device or a periodic array structure.
7. The method for manufacturing the TMDCs-based E-field induced Schottky photodiode according to any one of claims 1-6, comprising the steps of:
(1) providing a conductive substrate with a thin-layer insulating medium covered on the surface, wherein a TMDCs film is arranged on the thin-layer insulating medium;
(2) carrying out patterning treatment on the TMDCs thin film by adopting a photoetching process to form a window for exposing part of the TMDCs thin film;
(3) depositing metal on the surface of the TMDCs thin film graphic structure to form an electrode layer, thereby forming source and drain electrodes which are respectively connected with two ends of a target conductive channel region;
(4) patterning the formed area beside the source electrode by adopting a photoetching process again to form a window for exposing a part of the thin-layer insulating medium film;
(5) etching the thin-layer insulating medium pattern structure by taking the photoresist as a mask to form a window for exposing part of the conductive substrate;
(6) patterning the window and the source electrode which form the exposed conductive substrate by adopting a photoetching process again to form a window for communicating the conductive substrate and the source electrode;
(7) and depositing metal on the patterned window by taking the photoresist as a mask to realize the communication between the conductive substrate and the source electrode.
8. The method according to claim 7, wherein in the step (1), the thin insulating medium is SiO2、Al2O3、HfO2、TiO2、ZrO2、Y2O3、La2O3、Ta2O5And boron nitride or a composite structure thereof, wherein the thickness of the insulating layer is 2-200nm, and the gate capacitance of the insulating layer is not less than 1.4 × 10-7F/cm2(ii) a The conductive substrate is conductive metal Au, Al and Cu or a heavily doped semiconductor, preferably heavily doped P-type or N-type Si; wherein the doping concentration corresponding to the heavy doping is not less than 1019cm-3；
In the step (1), the TMDCs thin film is transferred to a conductive substrate by a dry method or a wet method, or is obtained by directly performing TMDCs thin film growth on the conductive substrate by a Chemical Vapor Deposition (CVD);
in the step (1), the TMDCs thin film layer is MoS2、MoSe2、MoTe2、WS2、WSe2One of them or any one of ternary and above compound crystal composed of them, the thickness of the TMDCs film is between 1nm-100 nm;
in the step (1), the TMDCs are intrinsic undoped or doped with a concentration not higher than 1018cm-3The doping state of (a);
in the step (5), the etching process is a dry etching process or a wet etching process; preferably, the dry etching is Reactive Ion Etching (RIE).
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