Graphene terahertz detector integrated with mesh antenna and preparation method thereof

Abstract

The application discloses a graphene terahertz detector integrated with a grid-shaped antenna and a preparation method thereof. The device preparation steps mainly include the following steps: transferring single-layer graphene onto a silicon / silicon dioxide substrate, preparing the grid-shaped antenna through standard ultraviolet lithography and electron beam evaporation, removing the excessive graphene through an oxygen ion etching process, and finally obtaining the graphene terahertz detector integrated with the grid-shaped antenna through a wire bonding process. The device structure is sequentially from bottom to top: the first layer is an intrinsic silicon substrate, the second layer is an oxide layer, and the third layer is graphene and a grid antenna electrode. The terahertz detector is formed by the grid antenna and the graphene, the carrier distribution in the channel can be adjusted from the micro-atomic level, the unique grid antenna can achieve high-efficiency focusing of a terahertz light field, and finally the high-sensitivity terahertz detection at room temperature is realized. The application has the advantages of fast response speed of the detector, self-driven operation at room temperature, small noise equivalent power and large-scale integration.

Description

Technical Field

[0001] This invention relates to a semiconductor detection device technology, specifically a terahertz detection device based on the high carrier mobility of graphene. Background Technology

[0002] Terahertz electromagnetic spectrum ranges from 0.1 to 10 THz, combining the advantages of both microwave electronics and infrared photonics. Research in terahertz technology involves disciplines such as physics, chemistry, materials science, and semiconductor science and technology, making it a typical interdisciplinary frontier technology field. This provides new technological avenues for atmospheric remote sensing, 6G communications, national defense security, and non-destructive testing. Due to the importance of terahertz technology, it has sparked a research boom worldwide. Undoubtedly, finding photodetectors with high sensitivity, fast response, and room temperature stability in the terahertz band is crucial for the development of terahertz technology. After decades of development, commercially available terahertz photodetectors (Gaolei tubes, Schottky diodes, calorimeters, etc.) still face some application challenges, such as complex device manufacturing processes, poor flexibility, and high prices. These factors limit the widespread application of terahertz technology.

[0003] Graphene is essentially a planar thin film composed of carbon atoms arranged in sp2 hybrid orbitals, exhibiting a hexagonal honeycomb lattice structure. A single layer is approximately 0.335 nm thick, making it the thinnest known two-dimensional optoelectronic material. In 2004, Geim and Novoselov of the University of Manchester in the UK prepared graphene that could exist stably at room temperature using a method involving the layer-by-layer exfoliation of single-crystal graphite with transparent tape, thus breaking the classic theory that graphene cannot exist independently. In recent years, graphene has rapidly become a hot research topic in various fields due to its unique band structure and superior properties unmatched by other materials. Furthermore, graphene exists in single-crystal and polycrystalline forms; single-crystal graphene has fewer defects and higher performance than polycrystalline graphene. With the development of novel graphene-based devices of different sizes, higher demands are being placed on the fabrication of single-crystal graphene with fewer defects and varying sizes. Graphene is essentially a single-atom-layer thin film with a hexagonal lattice. In terms of thermodynamics, it has high thermal conductivity and high mechanical strength; in terms of electrical properties, it has a large specific surface area and high electron mobility. These properties make it irreplaceable in many fields such as micro-nano electronic devices, biosensors, and batteries, attracting the attention of many scholars at home and abroad.

[0004] Graphene possesses unique advantages in the field of photoelectric detection; however, its atomic-level thickness inevitably reduces the terahertz absorption efficiency and photoelectric conversion capability of the detector. Therefore, designing a suitable antenna coupling structure has become an effective solution for fabricating graphene terahertz detectors. Currently, in the research of related photoelectric detection devices, to improve the energy coupling efficiency of the device to the incident light signal, enhance the device's response performance, and improve the signal-to-noise ratio, a common method is to add a specifically designed coupling antenna to the device design, thereby coupling the detected radiation to the detector. In the field of terahertz detection technology, many researchers have attempted to integrate coupling antennas into the detection device to obtain better detection performance at room temperature. The response of antenna coupling is selective; coupling antennas used in the terahertz band include helical antennas, log-periodic antennas, square helical antennas, and butterfly antennas. For coupling antennas integrated with photoelectric detection devices, excellent antenna design requires a large antenna gain, stable directivity characteristics, a wide bandwidth adaptability, and easy impedance matching with the photosensitive element of the detection device. Summary of the Invention

[0005] This invention proposes a graphene terahertz detector integrated with a grid-like antenna and its fabrication method. Under the favorable conditions of efficient focusing of the terahertz light field by the grid-like antenna, the device generates a temperature gradient due to the difference in Seebeck coefficients at both ends, driving the unidirectional motion of charge carriers. This enables high-speed and highly sensitive terahertz detection and imaging functions in a self-driven operating mode at room temperature.

[0006] The detector's structure, from bottom to top, consists of: a first layer of high-resistivity silicon substrate 1; a second layer of silicon dioxide oxide 2; a third layer of graphene 3; a metal electrode 4 located to the left of the graphene; and a metal electrode 5 located to the right of the graphene.

[0007] The substrate 1 is an intrinsically high-resistivity silicon substrate with a resistivity of 10000-20000 Ω·cm;

[0008] The oxide layer 2 is silicon dioxide with a thickness of 280-300 nm;

[0009] The graphene 3 mentioned is graphene grown by chemical vapor deposition, with a thickness of approximately 0.335-0.8 nm;

[0010] The metal electrode 4 on the left side of the graphene and the electrode 5 on the right side of the graphene are metal composite electrodes, with chromium as the lower metal and gold as the upper metal, and a thickness of 80-110 nm.

[0011] This invention relates to a graphene terahertz detector integrated with a grid-like antenna and its fabrication method. The device fabrication includes the following steps: growing a single layer of graphene on a copper foil substrate using chemical vapor deposition; spin-coating the graphene on the copper foil substrate with polymethyl methacrylate (PMMA), then etching the copper foil substrate with ferric chloride solution; cleaning the sample with dilute hydrochloric acid after 24 hours; transferring the PMMA-coated graphene to a silicon / silicon dioxide substrate with an oxide layer; obtaining the grid antenna structure using standard ultraviolet lithography, electron beam evaporation, and lift-off processes; removing excess single-layer graphene from the substrate surface by oxygen ion etching; and encapsulating the device and a base using ultrasonic bonding to fabricate an integrated graphene terahertz detector with a grid-like antenna.

[0012] The advantages of this invention patent are:

[0013] 1) Graphene was chosen as the channel material. Graphene, being a semi-metallic material, can be photoexcited over a wide frequency range and can be used in terahertz detectors with broadband and high-speed optical responses.

[0014] 2) Graphene grown by chemical vapor deposition can be prepared on a large scale using the solution transfer method.

[0015] 3) By adopting an easily integrated grid-like antenna structure, electromagnetic waves in the subwavelength channel are focused, which can effectively enhance the coupling effect of terahertz waves at the channel.

[0016] 4) The non-uniform distribution of terahertz electromagnetic field is achieved by using an asymmetric coupling structure, which in turn causes non-uniform diffusion of hot electrons to form photocurrent, enabling the detector to operate in self-powered mode. Attached Figure Description

[0017] Figure 1 This is a side view schematic diagram of the graphene terahertz detector structure unit integrated with the mesh antenna of the present invention;

[0018] Figure 2 This is a top view schematic diagram of the structure of the graphene terahertz detector device integrated with the grid antenna of the present invention. Figure a shows the overall structure of the antenna, and Figure b shows the fine structure at the channel.

[0019] Figure 3 This is a schematic diagram of the optical response of the graphene terahertz detector integrated with the mesh antenna of the present invention under different bias voltages;

[0020] Figure 4 The graphene terahertz detector with integrated mesh antenna of the present invention is shown in the response time diagram under terahertz light at different frequencies.

[0021] Figure 5This is a schematic diagram of the noise voltage of the graphene terahertz detector integrated with the grid antenna of the present invention. Detailed implementation method:

[0022] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings:

[0023] This invention relates to a graphene terahertz detector integrated with a grid antenna, its fabrication method, mechanism research, and performance improvement. Specifically, it utilizes the high carrier mobility of graphene and efficiently focuses terahertz waves through an integrated and optimized grid antenna to form a potential gradient at both ends of the graphene, driving the flow of non-equilibrium carriers, reducing the dark current and noise equivalent power of the device, thereby achieving a self-driven operating mode at room temperature and zero bias.

[0024] The specific steps are as follows:

[0025] 1. Substrate selection

[0026] Intrinsic silicon 1 and silicon dioxide 2 covering it were selected as substrates.

[0027] 2. Preparation and transfer of graphene

[0028] A single layer of graphene was grown on a copper foil substrate using chemical vapor deposition. The graphene on the copper foil substrate was then spin-coated with polymethyl methacrylate (PMMA), and the copper foil substrate was etched with ferric chloride solution. After 24 hours, the sample was cleaned with dilute hydrochloric acid, and the PMMA-coated graphene was then transferred to a silicon / silicon dioxide substrate with an oxide layer.

[0029] 3. Fabrication of Grid Antenna Electrodes

[0030] The grid antenna structure electrode was fabricated using ultraviolet lithography, thermal evaporation coating, and traditional lift-off processes. Figure 2 The metal layer deposited by vapor deposition is chromium at the bottom and gold at the top, with a thickness that can be selected from 80-110nm.

[0031] 4. Packaged devices

[0032] The device is attached to the base PCB board and packaged using an ultrasonic process that integrates a grid-like antenna into a graphene terahertz detector.

[0033] 5. Photoelectric response test

[0034] A microwave signal source is used to establish a frequency doubling link, enabling output in the 0.02 to 0.3 THz frequency band. The pulse signal modulation frequency of the microwave source is used as the reference signal source for the lock-in amplifier and oscilloscope. Simultaneously, the detector photoelectric signal amplified by the preamplifier is connected to the input port of the lock-in amplifier, and the output signal is the signal further amplified by the lock-in amplifier. This system improves the signal-to-noise ratio and enables automated testing of terahertz detector response signals, response times, and other parameters. Figure 3 The photocurrent-dependent bias response characteristics of the device at 0.04, 0.08, and 0.12 THz are shown. The results demonstrate that the grid-antenna integrated graphene terahertz detector provided by this invention exhibits high photoresponsivity at zero bias, and that the method for improving the detection capability of the device through grid antenna integration is feasible. Figure 4 Response time diagrams of a graphene terahertz detector integrated as a grid antenna under illumination of 0.04, 0.08, and 0.12 THz. Figure 5 The noise spectral density of the graphene terahertz detector integrated with the grid antenna under illumination of 0.04, 0.08, and 0.12 THz is shown to indicate that the method of effectively reducing dark current provided by the grid antenna integrated graphene terahertz detector in this invention is feasible.

[0035] The graphene terahertz detector integrated with a grid antenna in this invention can significantly improve the overall optical response of the device, such as reducing dark current noise, achieving a response time in the microsecond range, high responsivity, and low power consumption with self-powered operation. The results suggest that the graphene terahertz detector integrated with a grid antenna in this invention may be an ideal approach to realizing the application of low-dimensional material technology in the terahertz range.

Claims

1. A graphene terahertz detector integrated with a grid antenna, comprising an intrinsic silicon substrate (1), an oxide layer (2), graphene (3), a grid antenna metal electrode (4), and a grid antenna metal electrode (5), characterized in that, The detector has the following structure from bottom to top: the first layer is an intrinsic silicon substrate (1), the second layer is an oxide layer (2), the third layer is graphene (3), and there are metal electrodes (4) on the left side of the graphene and metal electrodes (5) on the right side of the graphene. The substrate (1) is an intrinsically high-resistivity silicon substrate with a resistivity of 10000-20000 Ω·cm; The oxide layer (2) is silicon dioxide with a thickness of 280-300 nm; The graphene (3) mentioned is graphene grown by chemical vapor deposition with a thickness of about 0.335-0.8 nm; The metal electrode (4) on the left side of the graphene and the metal electrode (5) on the right side of the graphene are metal composite electrodes, with chromium as the lower metal and gold as the upper metal, and a thickness of 80-110 nm.

2. A method for fabricating a graphene terahertz detector integrated with a mesh antenna as described in claim 1, characterized in that... The method is as follows: A monolayer of graphene was grown on a copper foil substrate using chemical vapor deposition. The graphene on the copper foil substrate was then spin-coated with polymethyl methacrylate (PMMA), followed by etching of the copper foil substrate with ferric chloride solution. After 24 hours, the sample was cleaned with dilute hydrochloric acid, and the PMMA-coated graphene was transferred to a silicon / silicon dioxide substrate with an oxide layer. A grid antenna structure was obtained using standard ultraviolet lithography, electron beam evaporation, and lift-off processes. Excess monolayer graphene on the substrate surface was removed by oxygen ion etching. The device and the base were then packaged using ultrasonic bonding to fabricate an integrated grid antenna graphene terahertz detector.

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