A tellurium-based room temperature terahertz detector device

Abstract

The invention discloses a tellurium-based room temperature terahertz detector device, which has a metal-semiconductor-metal structure, a tellurium nanosheet material for the semiconductor, and titanium and gold for the metal electrodes. The Te terahertz detector has a chopping frequency of 1kHz at room temperature, a response time of only 9.7μs at an operating frequency of 172GHz, a response rate of up to 600kV / W, and a NEP of less than 0.1pW / Hz at a 1V bias and 1kHz modulation frequency. 0 . 5 After the detector was heated to 200℃ for 20 minutes and then cooled twice, the response remained basically unchanged. Te terahertz detector has the following advantages: 1. Simple structure; 2. Can work at room temperature; 3. High device sensitivity; 4. Fast response speed; 5. Good stability.

Description

Technical Field

[0001] The present invention relates to the field of terahertz detection, and in particular to a tellurium-based room temperature terahertz detection device. Background Art

[0002] Terahertz (THz) covers the range of 0.1 to 10 THz and is a gap band between infrared and microwave [1]. Terahertz waves have technical characteristics such as strong penetration, high safety, good directionality, and high bandwidth, and have great potential application value. At present, infrared and microwave detection technologies have been developed to a relatively mature level, while terahertz waves are a band that humans have little understanding of and development to date. There is an urgent need to develop terahertz detectors that can work at high temperatures and have high sensitivity.

[0003] Tellurium (Te) is an important p-type narrow bandgap semiconductor with a bandgap of 0.3 eV and good stability. It was once prepared into a photoconductive detector. In 1961, the NEP value of the tellurium detector at 3.4 μm was theoretically calculated to be 3.1×10 -13 W[2]. This type of photoelectric detection has the problem of wavelength (photon energy) selectivity. The detection band depends on the size of the band gap. In the mid- and far-infrared electromagnetic bands, due to the presence of thermal noise energy, thermal noise excitation and optical excitation form a competition mechanism, which significantly reduces the detection efficiency and requires low temperature (4.2K, 77K) or even deep low temperature (100-300mK) refrigeration. Based on the newly proposed new mechanism of light-induced potential well effect, the present invention designs a metal-semiconductor-metal (MSM) structure terahertz detection device based on Te material[3]. When a photon with 0.7meV energy (much smaller than the Te band gap width of 0.3eV) is incident on the designed metal-semiconductor-metal (MSM) structure, a potential well will be induced in the Te material. The free electrons in the metal electrode will enter the semiconductor material Te and be bound by the induced potential well, causing the carrier concentration in Te to change and the conductivity of the material to change accordingly. The signal is read out by applying an external bias electric field, thereby achieving room temperature high-sensitivity detection in the terahertz band.

[0004] The references mentioned above are as follows:

[0005] 1.B.Ferguson and X.-C.Zhang,Materials for terahertz science and technology,Nat.Mater.1,26–33(2002).

[0006] 2.D.Genzow,Infrared Photovoltaic Radiation Detector with TelluriumSingle Crystals,Phys.Stat.Sol.(a)1,K77(1971).

[0007] 3. Zhiming Huang, Wei Zhou, Jinchao Tong, Jingguo Huang, Cheng Ouyang, Yue Qu, Jing Wu, Yanqing Gao, and Junhao Chu, Extreme Sensitivity of Room-Temperature Photoelectric Effect for Terahertz Detection, Adv. Mater. 28, 112–117 (2016). Summary of the invention

[0008] In view of the problems of low detection sensitivity, complex structure and deep-cryogenic refrigeration required for far-infrared terahertz band detectors, the present invention designs a tellurium-based room-temperature terahertz detector device, which can detect photon energy far smaller than the bandgap width of tellurium, has high detector sensitivity, fast response speed, good stability and can operate at room temperature.

[0009] A tellurium-based room temperature terahertz detector device of the present invention adopts a high-resistance silicon substrate 1, on which there is a naturally oxidized silicon dioxide layer 2, a tellurium nanosheet 3 is transferred to the silicon dioxide layer 2, and then a bilaterally symmetrical butterfly-shaped positive electrode layer 4 and a butterfly-shaped negative electrode layer 5 are prepared on the tellurium nanosheet;

[0010] The high-resistance silicon substrate 1 has a thickness of 0.5 mm and a resistivity of 10000 Ω·cm;

[0011] The naturally oxidized silicon dioxide 2 has a thickness of 25 nm;

[0012] The tellurium nanosheet 3 is a single crystal material prepared by chemical vapor deposition, and the nanosheet has a thickness of 300-500nm, a width of 5-10μm, and a length of 10-30μm;

[0013] The butterfly-shaped positive electrode layer 4 and the butterfly-shaped negative electrode layer 5 are both made of 30nm thick titanium and 300nm thick gold. Titanium is sputtered first and then gold is sputtered. The titanium and gold positive and negative electrode layers cover the surface and edge of the step formed by the tellurium nanosheet 3 to form a metal-semiconductor-metal structure and form an ohmic contact at the contact point. Most of the electrode layers are grown on the surfaces of both sides of the step. The butterfly-shaped positive electrode layer 4 and the butterfly-shaped negative electrode layer 5 surround the two sides of the device and are respectively and The shape is distributed in mirror symmetry; the upper end surfaces of the butterfly-shaped positive electrode layer 4 and the butterfly-shaped negative electrode layer 5 form a left-right symmetrical butterfly antenna, with specific dimensions: the electrode width w is 500μm, the total length l at both ends is 4000μm, the electrode spacing a, i.e. the sensitive element length, is 5-10μm, and the electrode width at the contact with the sensitive element, i.e. the sensitive element width b, is 5-10μm.

[0014] The top view of the detector is shown in the attached figure. Figure 1 As shown, the cross-section and plane diagram at the center of the device are shown in Figure 2 As shown, 1 is high-resistance silicon, 2 is naturally oxidized silicon dioxide, 3 is tellurium nanosheets, 4 is a titanium positive electrode layer, and 5 is a titanium negative electrode layer.

[0015] The detector structure designed by the present invention is realized through the following specific process steps:

[0016] 1. Substrate selection

[0017] A high-resistance silicon (Si) substrate is selected, and there is a layer of naturally oxidized silicon dioxide (SiO2) on the surface of the substrate.

[0018] 2. Preparation and Transfer of Tellurium Nanosheets

[0019] Tellurium nanosheets were prepared by chemical vapor deposition and transferred to the substrate surface by mechanical exfoliation.

[0020] 3. Photolithography

[0021] A layer of photoresist is spin-coated on the surface of the silicon substrate sample with tellurium nanoparticles transferred thereon, the sample is placed in a dryer for drying, and the electrode is covered with a butterfly mask and then exposed using a photolithography machine.

[0022] 4. Development

[0023] The exposed samples are placed in the prepared developer for development. After development, the samples are taken out and placed in a drying oven for post-baking.

[0024] 5. Sputtering electrode

[0025] The sample was placed in a dual ion beam sputtering chamber and titanium and gold were sputtered sequentially to a certain thickness.

[0026] 6. Stripping

[0027] The sample is placed in a beaker filled with acetone solution and after heating in a water bath, the excess metal film will fall off. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Attached Figure 1 Schematic diagram of the detector from top view.

[0029] Attached Figure 2Schematic diagram of the cross section and plane at the center of the device.

[0030] The numbers in the accompanying drawings are: 1 is a high-resistance silicon substrate, 2 is a naturally oxidized silicon dioxide layer, 3 is a tellurium nanosheet, 4 is a butterfly-shaped positive electrode layer, and 5 is a butterfly-shaped negative electrode layer.

[0031] Attached Figure 3 This is the response waveform of the detector at room temperature with a chopping frequency of 1kHz and an operating frequency of 172GHz.

[0032] Attached Figure 4 Responsivity and noise equivalent power of Te terahertz detectors in the range of 169-173 GHz.

[0033] Attached Figure 5 This is the waveform diagram after the device was heated twice to 200℃ for 20 minutes and then cooled. DETAILED DESCRIPTION

[0034] According to the attached Figure 1 According to the structure shown, three types of detection devices were manufactured.

[0035] Embodiment detector 1 adopts a high-resistance silicon substrate with a substrate thickness of 0.5 mm and a resistivity of 10000 Ω·cm. There is a 25 nm thick silicon dioxide layer on the substrate. The Te nanosheets are transferred to the silicon dioxide layer by mechanical stripping. On the surface of the sample with the Te nanosheets transferred, butterfly-shaped positive and negative electrode layers are prepared by photolithography and dual ion beam sputtering. During sputtering, 30 nm thick titanium is sputtered first, and then 300 nm thick gold is sputtered. The electrode width is 500 μm, and the total length at both ends is 4000 μm. The electrode spacing, that is, the length of the sensitive element, is 5 μm, and the electrode width at the contact with the sensitive element, that is, the width of the sensitive element, is 5 μm.

[0036] The detector 2 of the embodiment adopts a high-resistance silicon substrate with a thickness of 0.5 mm and a resistivity of 10000 Ω·cm. There is a 25 nm thick silicon dioxide layer on the substrate. The Te nanosheets are transferred to the silicon dioxide layer by mechanical stripping. On the surface of the sample with the Te nanosheets transferred, butterfly-shaped positive and negative electrode layers are prepared by photolithography and dual ion beam sputtering. During sputtering, 30 nm thick titanium is sputtered first, and then 300 nm thick gold is sputtered. The electrode width is 500 μm, and the total length at both ends is 4000 μm. The electrode spacing, that is, the length of the sensitive element, is 5 μm, and the electrode width at the contact with the sensitive element, that is, the width of the sensitive element, is 10 μm.

[0037] The detector 3 of the embodiment adopts a high-resistance silicon substrate with a thickness of 0.5 mm and a resistivity of 10000 Ω·cm. There is a 25 nm thick silicon dioxide layer on the substrate. The Te nanosheets are transferred to the silicon dioxide layer by mechanical stripping. On the surface of the sample with the Te nanosheets transferred, butterfly-shaped positive and negative electrode layers are prepared by photolithography and dual ion beam sputtering. During sputtering, 30 nm thick titanium is sputtered first, and then 300 nm thick gold is sputtered. The electrode width is 500 μm, and the total length at both ends is 4000 μm. The electrode spacing, that is, the length of the sensitive element, is 10 μm, and the electrode width at the contact with the sensitive element, that is, the width of the sensitive element, is 10 μm.

[0038] The present invention is further described in detail below by introducing specific experimental steps.

[0039] 1. Preparation of tellurium nanosheet materials

[0040] Put the radon precursor into a quartz boat, and then place the quartz boat in the high-temperature reaction zone in the tube furnace chamber; place the inverted Si / SiO2 substrate on the quartz boat, and then place the quartz boat in the low-temperature growth zone. After vacuuming, argon gas is pumped in to exhaust the residual air in the quartz tube. During the reaction, argon gas flows in continuously at a flow rate of 40sccm. In the two temperature zones, it takes 20 minutes from room temperature to 200°C, and then after 30 minutes, the high-temperature zone can reach 520°C and the low-temperature zone can reach 450°C. The temperatures in the two temperature zones are maintained for 180 minutes. Finally, after 50 minutes, when the temperature drops to room temperature, the Te nanosheets grown on the substrate can be taken out.

[0041] 2. Preparation of tellurium-based room temperature terahertz detectors

[0042] The tellurium nanosheets were transferred to a high-resistance silicon substrate by mechanical stripping, and the photoresist AZ4330 was spin-coated on the sample. Spin coating parameters: 4000 rpm, 30 seconds. Then the sample was placed in a dryer and dried for 25 minutes at 65°C. After drying, a mask and a UV lithography machine SUSS MJB4 were used to make electrodes for 6 seconds. The developer was used for development, and the developer ratio was configured according to the ratio of AZ400K: deionized water = 1:4, and the development time was 30 seconds. After development, the sample was placed in a dryer for drying, and the parameters were the same as the pre-baking. Then the sample was placed in a dual ion beam sputtering chamber, and Ti and Au with a thickness of 30nm and 300nm were sputtered respectively. Then the sample was placed in a beaker filled with acetone solution and heated to 50°C in a water bath. After 30 minutes, the excess metal film was peeled off.

[0043] 3. Performance test of tellurium-based room temperature terahertz detector

[0044] The performance of the detector is tested using a terahertz test system. The modulated terahertz is irradiated vertically and uniformly on the detector surface. The exit of the source is 30 cm away from the detector, which is mounted on a test box. After the detector detects the terahertz wave, the response voltage signal is amplified by the preamplifier and finally read out by the lock-in amplifier. Figure 3 This is the response waveform of the Te terahertz detector at room temperature with a chopping frequency of 1kHz and an operating frequency of 172GHz. The response time is 9.7μs.

[0045] To further characterize the device performance, the response of the Te terahertz detector in the 169-173 GHz range at room temperature was measured under different bias voltages. At a modulation frequency of 1 kHz and a bias of 1 V, the device response in the 172 GHz range was as high as 90 μV. The device's responsivity and noise equivalent power are two important indicators for measuring device performance. Here, the device's responsivity is defined as R v =V ph / (P×A), V ph is the voltage response value of the device, P is the power density of the terahertz source radiated to the surface of the device, A is the area of ​​the sensitive element of the device, NEP is the minimum detectable power per unit bandwidth, NEP = v n / R v , v n is the RMS noise voltage, v n =(4k B Tr+2eI d r 2 ) 0.5 , k B is the Boltzmann constant, r is the resistance of the device, e is the unit charge, I d is the dark current when biased, and here is the bias current of the device. The optical power density at 170 GHz is P = 0.15 mW / cm 2 According to calculations, the device has a responsivity of up to 600kV / W at 172GHz and a NEP of less than 0.1pW / Hz at 1V bias and 1kHz modulation frequency. 0.5 ,like Figure 4 shown.

[0046] In order to test the stability of the device, the photodetector was heated to 200℃ for 20 minutes. After the detector was cooled, the response remained basically unchanged. The detector was heated to 200℃ for 20 minutes again. After cooling, the test response remained basically unchanged. Figure 5 As shown, the Te photodetector exhibits good stability in various harsh working environments.

Claims

1. A tellurium-based room temperature terahertz detection device, characterized in that: The device adopts a high-resistance silicon substrate (1) on which there is a naturally oxidized silicon dioxide layer (2), a tellurium nanosheet (3) is transferred onto the silicon dioxide layer (2), and then a bilaterally symmetrical butterfly-shaped positive electrode layer (4) and a butterfly-shaped negative electrode layer (5) are prepared on the tellurium nanosheet; The high-resistance silicon substrate (1) has a thickness of 0.5 mm and a resistivity of 10000 Ω·cm; The naturally oxidized silicon dioxide layer (2) has a thickness of 25 nm; The tellurium nanosheet (3) is a single crystal material prepared by chemical vapor deposition, and the nanosheet has a thickness of 300-500nm, a width of 5-10μm, and a length of 10-30 microns; The butterfly-shaped positive electrode layer (4) and the butterfly-shaped negative electrode layer (5) are both made of 30 nm thick titanium and 300 nm thick gold. Titanium is first sputtered and then gold is sputtered. The titanium and gold positive and negative electrode layers cover the surface and edge of the step formed by the tellurium nanosheet (3) to form a metal-semiconductor-metal structure and form an ohmic contact at the contact point. Most of the electrode layers are grown on the surfaces of both sides of the step. The butterfly-shaped positive electrode layer (4) and the butterfly-shaped negative electrode layer (5) are respectively formed around the two sides of the device. and The shape is distributed in mirror-symmetric manner; the upper end surfaces of the butterfly-shaped positive electrode layer (4) and the butterfly-shaped negative electrode layer (5) form a bilaterally symmetrical butterfly antenna, with specific dimensions as follows: the electrode width w is 500 μm, the total length l at both ends is 4000 μm, the electrode spacing a, i.e. the sensitive element length, is 5-10 μm, and the electrode width at the contact point with the sensitive element, i.e. the sensitive element width b, is 5-10 μm.

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