Space-time scale adjustable Schottky barrier photoelectric detector and preparation method thereof

Abstract

The invention belongs to the related technical field of semiconductor devices, and discloses a spatio-temporal scale adjustable Schottky barrier photoelectric detector, which comprises a gate layer, a gate dielectric layer and a channel layer which are stacked in sequence, and a drain and a source which are stacked on the channel layer respectively, and the drain and the source are made of metal materials with different work functions respectively. The channel layer is made of a semiconductor material with the work function between the drain electrode and the source electrode and has the photosensitive property, and Schottky contact or ohmic contact is formed between the drain electrode and the source electrode and the channel layer. When the photoelectric detector works, the photoelectric detector has a rectification characteristic and a light response characteristic, and multi-stage regulation and control of the light response relaxation time can be realized by changing the grid voltage. The invention further discloses a corresponding preparation method. Compared with the prior art, the problems of fixed spatial-temporal scale, single application scene and the like of the photoelectric detector are effectively solved, so that the photoelectric detector is particularly suitable for the application requirements of large-detection-range and high-sensitivity light sensing calculation scenes.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor device technology, and more specifically, relates to a spatiotemporally adjustable Schottky barrier photodetector and its fabrication method. Background Technology

[0002] In recent years, the field of photoelectric detection and imaging has developed rapidly. Photodetectors, as devices that convert light signals into electrical signals, have been widely studied by industry and academia. Based on the contact type between the electrode and the photosensitive layer, they are mainly classified into photoconductive detectors, Schottky barrier detectors, and metal-semiconductor-metal detectors. Among them, Schottky barrier detectors have lower switching losses and dark currents, faster recovery speeds, and a planar structure, making their fabrication process simple and requiring no high-temperature diffusion or doping.

[0003] In existing technologies, the barrier height of Schottky barrier detectors depends on fabrication conditions, the contact between the metal and semiconductor, and the influence of surface states; the barrier height is determined once the device is fabricated. However, further research shows that in practical photodetection scenarios, a fixed Schottky barrier results in a single photoresponse current and photoresponse relaxation time in the photodetector, limiting the spatiotemporal scale range of detection and thus restricting its application potential in neuromorphic computing, edge computing, and machine vision.

[0004] Therefore, there is an urgent need for research and improvement in this field so that Schottky barrier detectors can be better applied to optical sensing computing scenarios with large detection range and high sensitivity. Summary of the Invention

[0005] To address one or more of the above-mentioned defects or improvement needs of existing technologies, this invention provides a spatiotemporally adjustable Schottky barrier photodetector and its fabrication method. By improving its specific structural composition and arrangement, especially by redesigning its working mechanism, this invention not only utilizes the source and drain electrodes to form Schottky and Ohmic contacts with the communication layer respectively to achieve rectification characteristics, but also introduces gate voltage regulation to change the Schottky barrier height, thereby obtaining an adjustable photoresponse relaxation time. Compared with existing technologies, this invention effectively solves the problems of fixed spatiotemporal scale and limited application scenarios of photodetectors, and is therefore particularly suitable for applications requiring large detection range and high sensitivity in optical sensing computing scenarios.

[0006] To achieve the above objectives, according to one aspect of the present invention, a spatiotemporally tunable Schottky barrier photodetector is provided. The photodetector includes a gate layer, a gate dielectric layer, and a channel layer stacked sequentially from bottom to top, and a drain and a source respectively stacked on the channel layer, wherein: The drain and the source are made of metal materials with different work functions, and the channel layer is made of a semiconductor material with a work function between that of the drain and the source and has photosensitive properties; the drain, the source and the channel layer form one of the following two types of contacts, which are different from each other: Schottky contact or Ohmic contact; When the aforementioned photodetector is in operation, the drain is connected to a voltage excitation source, and the source is grounded. In this way, under dark conditions, the photodetector has rectification characteristics, and its forward and reverse currents are of different magnitudes. Under illumination, the photodetector has photoresponse characteristics, and its photoresponse current increases with the increase of the optical power of the probe light. In addition, by changing the gate voltage, the Schottky barrier height of the photodetector changes accordingly, thereby achieving multi-level control of the photoresponse relaxation time.

[0007] As a further preferred embodiment of the present invention, the drain is made of a metal material with a first work function Φ1, the source is made of a second metal material with a second work function Φ2, and the channel layer is made of a p-type or n-type semiconductor material with a third work function Φ3, wherein Φ1 > Φ3 > Φ2.

[0008] As a further preferred embodiment of the present invention, the source electrode is made of a metal material with a first work function Φ1, the drain electrode is made of a second metal material with a second work function Φ2, and the channel layer is made of a p-type or n-type semiconductor material with a third work function Φ3, wherein Φ1 > Φ3 > Φ2.

[0009] As a further preferred embodiment of the present invention, the first metal material is selected from any one of the following: Au, Pt, Ni; the second metal material is selected from any one of the following: Al, W, Ti; and the semiconductor material is selected from any one or a combination of the following: SiTe, GeO, TiO, SnO.

[0010] As a further preferred embodiment of the present invention, the channel layer has photosensitive properties and its bandgap is smaller than the photon energy of the probe light.

[0011] As a further preferred embodiment of the present invention, under the condition of fixed optical power of the probe light, when the gate voltage is less than zero and gradually decreases, the Schottky barrier height of the photodetector decreases, the photoresponse current gradually increases, and the photoresponse relaxation time gradually increases; while when the gate voltage is greater than zero and gradually increases, the Schottky barrier height of the photodetector increases, the photoresponse current gradually decreases, and the photoresponse relaxation time gradually decreases.

[0012] As a further preferred embodiment of the present invention, for the above-mentioned photodetector, its photoresponse current decreases exponentially with the increase of the gate voltage, and its photoresponse relaxation time decreases substantially linearly with the increase of the gate voltage.

[0013] According to another aspect of the present invention, a corresponding preparation method is also provided, the method comprising the following steps: Step 1: Provide a heavily doped silicon substrate as the gate layer; Step 2: Deposit the gate dielectric layer on the gate layer using chemical vapor deposition; Step 3: Continue to deposit the channel layer on the gate dielectric layer using a co-sputtering method; Step 4: Define the source and drain patterns on the channel layer using electron beam lithography; Step 5: Deposit the drain and the source on the channel layer using a sputtering method, and form one of the following two types of contacts between the drain, the source and the channel layer, which are different from each other: Schottky contact or Ohmic contact.

[0014] In summary, the technical solutions conceived by this invention have the following main technical advantages compared with the prior art: (1) This invention improves the specific structure and configuration of the photodetector, especially redesigns its working mechanism. It can not only use the source and drain to form Schottky and Ohm contacts with the communication layer to achieve rectification characteristics, but also introduce gate voltage regulation to change the height of the Schottky barrier, thereby obtaining an adjustable light response relaxation time. Compared with the prior art, it effectively solves the problems of fixed spatiotemporal scale and single application scenario of photodetectors. (2) The photodetector designed in this invention has a compact overall structure and is easy to operate. Furthermore, by adjusting the gate power supply, the height of the Schottky barrier can be changed more flexibly and conveniently, thereby achieving precise adjustment of the photoresponse relaxation time. (3) The photodetector designed in this invention has an adjustable spatiotemporal scale, a large detection range, high sensitivity, is easy to fabricate on a large area, does not require high-temperature diffusion or doping processes, and is compatible with CMOS processes. (4) Compared with existing similar products, the photodetector designed in this invention can significantly improve the spatiotemporal scale range of detection, thereby helping to unleash its application potential in multiple fields such as neuromorphic computing, edge computing and machine vision. Therefore, it is particularly suitable for large detection range and highly sensitive light perception computing scenarios. Attached Figure Description

[0015] Figure 1This is a schematic diagram of the overall structure of the Schottky barrier photodetector with adjustable spatiotemporal scale according to the present invention. Figure 2 This is a process flow diagram of a preferred embodiment for fabricating the spatiotemporally tunable Schottky barrier photodetector of the present invention. Figure 3 This is a voltage-current scan curve obtained under dark and light conditions for a Schottky barrier photodetector provided in conjunction with a specific example of the present invention; Figure 4 This is a photoresponse current diagram obtained by applying different pulsed light powers to a Schottky barrier photodetector provided in conjunction with a specific example of the present invention. Figure 5a This is a current response diagram obtained by applying different gate voltages to a Schottky barrier photodetector provided in conjunction with a specific example of the present invention. Figure 5b This is a photoresponse current-gate voltage relationship diagram obtained from a Schottky barrier photodetector provided in conjunction with a specific example of the present invention; Figure 6 This is a schematic diagram of the optical response obtained by applying a single light pulse to a Schottky barrier photodetector provided in conjunction with a specific example of the present invention. Figure 7a This is a photoresponse relaxation time diagram obtained by applying different gate voltages to a Schottky barrier photodetector provided in conjunction with a specific example of the present invention; Figure 7b This is a graph showing the photoresponse relaxation time-gate voltage relationship obtained from a Schottky barrier photodetector provided in conjunction with a specific example of the present invention; In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, wherein: 1-Gate layer; 2-Gate dielectric layer; 3-Channel layer; 4-Drain; 5-Source. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0017] It should be understood that expressions such as "comprising" and "may include" as used in this application indicate the existence of the disclosed functions, operations, or constituent elements, and do not limit one or more additional functions, operations, and constituent elements. In this application, terms such as "comprising" and / or "having" may be interpreted as indicating a specific characteristic, number, operation, constituent element, component, or combination thereof, but should not be interpreted as excluding the existence or possibility of adding one or more other characteristics, numbers, operations, constituent elements, components, or combinations thereof.

[0018] It should be understood that the terms “center,” “upper,” “lower,” “front,” “rear,” “left,” “right,” “vertical,” “horizontal,” “inner,” “outer,” “clockwise,” “counterclockwise,” “axial,” “radial,” and “circumferential” indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0019] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0020] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0021] Figure 1 This is a schematic diagram of the overall structure of the Schottky barrier photodetector with adjustable spatiotemporal scale according to the present invention. The following will be combined with... Figure 1 To explain the invention in more detail.

[0022] like Figure 1 As shown in the figure, the present invention provides a Schottky barrier photodetector with adjustable spatiotemporal scale. The photodetector includes a gate layer 1, a gate dielectric layer 2 and a channel layer 3 stacked sequentially from bottom to top, as well as a drain 4 and a source 5 stacked on the channel layer 3, which will be described in detail below.

[0023] The drain 4 and source 5, which constitute key components of the present invention, are made of metal materials with different work functions. Correspondingly, the channel layer 3, which constitutes another key component of the present invention, is made of a semiconductor material with a work function between that of the drain 4 and the source 5 and has photosensitive properties. In addition, the drain 4, the source 5 and the channel layer 3 form one of the following two types of contacts, which are different from each other: Schottky contact or Ohmic contact.

[0024] More specifically, the source and drain electrodes are made of metals with different work functions. Commonly used metals with high work functions include Au, Pt, and Ni, while those with low work functions include Al, W, and Ti. The channel layer is made of n-type or p-type semiconductor material, with a work function between that of the source and drain electrodes. The channel layer forms Schottky or ohmic contacts with the source and drain electrodes, respectively. For example, the channel layer material can be one or more of SiTe, GeO, TiO, and SnO.

[0025] When the aforementioned photodetector is in operation, the drain 4 is connected to the voltage excitation source, and the source 5 is grounded. In this way, under dark conditions, the photodetector has rectification characteristics, and its forward and reverse currents are of different magnitudes. Under illumination conditions, the photodetector has photoresponse characteristics, and its forward and reverse currents are of different magnitudes. In addition, by changing the gate voltage, the Schottky barrier height of the photodetector changes accordingly, thereby achieving multi-level control of the photoresponse relaxation time.

[0026] More specifically, on the one hand, by forming Schottky or Ohmic contacts between the channel layer and the source and drain electrodes respectively, the photodetector exhibits rectification characteristics, with the forward current being much greater than the reverse current. Under illumination, the photodetector also exhibits photoresponse characteristics, with the photoresponse current increasing with the intensity of the light stimulus. On the other hand, changes in the gate voltage alter the Fermi level of the channel layer, thereby modulating the Schottky barrier height and achieving multi-level control of the photoresponse current and relaxation time. Specifically, when the Schottky barrier height decreases, the photoresponse current increases, and the photoresponse relaxation time increases; conversely, when the Schottky barrier height increases, the photoresponse current decreases, and the photoresponse relaxation time decreases.

[0027] The following is a specific embodiment of a photodetector used to illustrate the present invention.

[0028] In this specific embodiment, the photodetector includes a gate layer, a SiO2 gate dielectric layer, a channel layer, and source and drain electrodes. The source electrode is a W electrode, and the drain electrode is a Pt electrode. The channel layer is made of n-type semiconductor material SiTe, whose work function is greater than that of the source W and less than that of the drain Pt. The channel layer forms an ohmic contact with the source W and a Schottky contact with the drain Pt. Furthermore, in this embodiment, the SiTe channel layer has photosensitive properties with a bandgap of 1.51 eV. The wavelength of the probe light is 532 nm, corresponding to a photon energy of 2.33 eV.

[0029] Actual tests show that the above photodetector has rectification characteristics in dark conditions, and the forward current is much greater than the reverse current; under illumination conditions, it has photoresponse characteristics, and the magnitude of its photoresponse current increases with the increase of light stimulation intensity.

[0030] See Figure 2 The invention also provides a method for fabricating the Schottky barrier photodetector of the present invention, the method comprising the following steps: Step 1: Provide a heavily doped silicon substrate as gate layer 1; Step 2: Deposit gate dielectric layer 2 on gate layer 1 using chemical vapor deposition; Step 3: Deposit the channel layer 3 on the gate dielectric layer 2 using a co-sputtering method; Step 4: Define the source and drain patterns on channel layer 3 using electron beam lithography; Step 5: Deposit drain 4 and source 5 on channel layer 3 by sputtering, and form one of the following two types of contacts between drain 4, source 5 and channel layer 3, which are different from each other: Schottky contact or Ohmic contact.

[0031] Figure 3 This invention relates to a Schottky barrier photodetector provided in a specific example, showing voltage-current scan curves obtained under dark and illuminated conditions. Figure 3 It can be seen that under dark conditions, the forward current is greater than the reverse current, exhibiting rectification characteristics; under illumination conditions, both forward and reverse currents increase, with the reverse current increasing more than the forward current, which is due to the photo-induced reduction of the potential barrier.

[0032] Figure 4 This is a photoresponse current diagram obtained by applying different pulsed light powers to a Schottky barrier photodetector provided in conjunction with a specific example of the present invention. Figure 3 It can be seen that under zero gate voltage conditions, the photoresponse current increases with increasing optical power, showing a linear trend.

[0033] Figure 5aThis is a current response diagram obtained by applying different gate voltages to a Schottky barrier photodetector provided in conjunction with a specific example of the present invention. Figure 5b This is a photoresponse current-gate voltage relationship diagram obtained from a Schottky barrier photodetector provided in conjunction with a specific example of the present invention. From Figure 5a It can be seen that, under the condition of fixed optical power, when the gate voltage is less than zero and gradually decreases, the Fermi level rises, the Schottky barrier height decreases, and the photoresponse current gradually increases; when the gate voltage is greater than zero and gradually increases, the Fermi level decreases, the Schottky barrier height increases, and the photoresponse current gradually decreases. Summarizing the relationship between the photoresponse current and the gate voltage, it can be found that the photoresponse current decreases exponentially with increasing gate voltage, such as... Figure 5b As shown in the image.

[0034] Figure 6 This is a schematic diagram of the optical response obtained by applying a single light pulse to a Schottky barrier photodetector provided in conjunction with a specific example of the present invention. Figure 6 As shown, the rise time is 450 ms and the decay time is 340 ms.

[0035] Figure 7a This is a photoresponse relaxation time diagram obtained by applying different gate voltages to a Schottky barrier photodetector provided in conjunction with a specific example of the present invention. Figure 7b This is a photoresponse relaxation time-gate voltage relationship diagram obtained from a Schottky barrier photodetector provided in conjunction with a specific example of the present invention. From Figure 7a It can be seen that, under the condition of fixed optical power, when the gate voltage is less than zero and gradually decreases, the Fermi level increases, the Schottky barrier height decreases, the trap filling level in the SiTe channel layer increases, and the photoresponse relaxation time gradually increases; when the gate voltage is greater than zero and gradually increases, the Fermi level decreases, the Schottky barrier height increases, the trap filling level in the SiTe channel layer decreases, and the photoresponse relaxation time gradually decreases. Summarizing the relationship between photoresponse relaxation time and gate voltage, it can be found that the photoresponse relaxation time decreases with increasing gate voltage. Figure 7b As shown in the image.

[0036] In summary, the Schottky barrier photodetector of the present invention, through improvements to its specific structure and configuration, particularly its redesigned working mechanism, not only utilizes the source and drain electrodes to form Schottky and ohmic contacts with the communication layer respectively to achieve rectification characteristics, but also introduces gate voltage regulation to change the Schottky barrier height, thereby obtaining an adjustable photoresponse relaxation time. Compared with existing technologies, this effectively solves the problems of fixed spatiotemporal scale and limited application scenarios of photodetectors. The photodetector provided by the present invention has an adjustable gate spatiotemporal scale, a large detection range, high sensitivity, is easy to fabricate on a large area, requires no high-temperature diffusion or doping process, and is compatible with CMOS technology. Therefore, it is particularly suitable for large-detection-range, high-sensitivity optical sensing computing scenarios, and has good practical value and application prospects.

[0037] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A Schottky barrier photodetector with adjustable space-time scale, comprising a gate layer (1), a gate dielectric layer (2) and a channel layer (3) stacked in order from bottom to top, and a drain (4) and a source (5) each stacked on the channel layer (3), characterized in that: the drain (4) and the source (5) are made of metal materials with different work functions respectively, the channel layer (3) is made of a semiconductor material with a work function between the work functions of the drain (4) and the source (5) and has photosensitive properties; the drain (4), the source (5) and the channel layer (3) form one of the following two kinds of contacts and are different from each other: a Schottky contact or an Ohmic contact; when the photodetector is in operation, the drain (4) is connected to a voltage excitation source and the source (5) is grounded; in this way, the photodetector has rectification characteristics in the dark and its forward and reverse current sizes are different; under light conditions, the photodetector has light response characteristics and its light response current size increases with the increase of the light power of the detected light; in addition, by changing the gate voltage, the Schottky barrier height of the photodetector changes, thereby achieving multi-level control of the light response relaxation time. the drain (4) is made of a metal material with a first work function Φ1, the source (5) is made of a second metal material with a second work function Φ2, the channel layer (3) is made of a p-type or n-type semiconductor material with a third work function Φ3, and Φ1 > Φ3 > Φ2.

2. The Schottky barrier photodetector with adjustable space-time scale of claim 1, wherein, the source (5) is made of a metal material with a first work function Φ1, the drain (4) is made of a second metal material with a second work function Φ2, the channel layer (3) is made of a p-type or n-type semiconductor material with a third work function Φ3, and Φ1 > Φ3 > Φ2.

3. The Schottky barrier photodetector of claim 1, wherein the Schottky barrier photodetector is a Schottky barrier photodetector with a tunable spatial scale and a tunable temporal scale. the first metal material is selected from any one of Au, Pt and Ni; the second metal material is selected from any one of Al, W and Ti; and the semiconductor material is selected from any one or combination of SiTe, GeO, TiO and SnO.

4. The time and spatial scale adjustable Schottky barrier photodetector according to claim 2 or 3, wherein, the channel layer (3) has photosensitive properties and its band gap is smaller than the photon energy of the detected light.

5. The time and spatial scale adjustable Schottky barrier photodetector according to any one of claims 1-4, wherein, under the condition that the light power of the detected light is fixed, when the gate voltage is less than zero and gradually decreases, the Schottky barrier height of the photodetector decreases, the light response current gradually increases, and the light response relaxation time gradually increases; when the gate voltage is greater than zero and gradually increases, the Schottky barrier height of the photodetector increases, the light response current gradually decreases, and the light response relaxation time gradually decreases.

6. The time and spatial scale adjustable Schottky barrier photodetector according to any one of claims 1-5, wherein, for the photodetector, its light response current presents an exponential decrease trend with the increase of the gate voltage, and its light response relaxation time basically presents a linear decrease trend with the increase of the gate voltage.

7. The time and spatial scale adjustable Schottky barrier photodetector according to any one of claims 1-6, wherein, the method comprises the following steps:

8. A method for fabricating a Schottky barrier photodetector as claimed in any one of claims 1-7, characterized in that, step one: providing a heavily doped silicon substrate as the gate layer (1); step two: depositing the gate dielectric layer (2) on the gate layer (1) by chemical vapor deposition; ​ Step three: continue to deposit the channel layer (3) on the gate dielectric layer (2) by co-sputtering method; Step four: define the pattern of source and drain on the channel layer (3) by electron beam lithography; Step five: deposit the drain (4) and the source (5) on the channel layer (3) respectively by sputtering method, and the drain (4) and the source (5) form one of the following two kinds of contacts with the channel layer (3) respectively and are different from each other: Schottky contact or ohmic contact.

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