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298 results on '"Zheng Youdou"'

1. Multi-height metasurface for wavefront manipulation fabricated by direct laser writing lithography

Author

Ye Fan, Pivnenko Mike, Huang Huiyu, Chang Xin, Robinson Lee, Zheng Youdou, Shi Yi, and Chu Daping

Subjects
dielectric metasurfaces, direct laser writing, phase modulation, Physics, QC1-999
Abstract

We introduce two types of dielectric metasurfaces, consisting of 3 × 3 regions, which manipulate wavefront by different feature heights. Both polarization-dependent and polarization-independent metasurfaces are realized for phase depth of 0 ∼ 2π at 1550 nm, with considerable average transmittance of 80.1 and 85.1 %, respectively. The phase modulation capability can be extended over a broadband range of 1460.1–1618.0 nm for optical communications, by carefully designing nanofeature sizes. Moreover, the entire metasurfaces with nanofeatures of varying heights can be fabricated in a single process by using direct laser writing with high-precision, which is beneficial for mass production and promising in developing efficient and ultracompact devices.

Published
2023
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2. Stable single-mode operation of distributed feedback quantum cascade laser under high current via a grating reflector

Author

Ye Fan, Cheng Fengmin, Jia Zhiwei, Zhang Jinchuan, Zhuo Ning, Liu Fengqi, Zheng Youdou, and Shi Yi

Subjects
dfb qcl, grating reflector, light distribution, single-mode stability, Physics, QC1-999
Abstract

We report on an index-coupled distributed feedback (DFB) quantum cascade lasers (QCLs) of high single-mode stability by using of a grating reflector (GR) to reflect effectively light of a specific wavelength. Fabrications of the QCLs were performed with λ∕4 equivalent phase shift (EPS) or sampled Moiré grating (SMG) structure, which regulates the light intensity distribution in the cavity and coupling strength. Both EPS-GR and SMG-GR QCLs demonstrate a high emission wavelength precision and a side-mode-suppression-ratio (SMSR) of 24.5 dB at the injection current of 5 A and the pulse width of 5 μs, offering considerable output power even at the edge of the gain spectrum. Furthermore, we investigated the arrays of EPS-GR and SMG-GR QCLs with lower threshold current and higher output power by introducing semi-insulated InP (Fe) ranging from 8.25 to 8.67 μm and 8.16–8.63 μm, respectively. The present QCLs via a GR are prospective for applications requiring single-mode stability and wide tunability.

Published
2023
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3. Solar-blind ultraviolet photodetector based on vertically aligned single-crystalline β-Ga2O3 nanowire arrays

Author

Zhang Liying, Xiu Xiangqian, Li Yuewen, Zhu Yuxia, Hua Xuemei, Xie Zili, Tao Tao, Liu Bin, Chen Peng, Zhang Rong, and Zheng Youdou

Subjects
inductively coupled plasma etching, solar-blind photodetector, vertical β-ga2o3 nanowire arrays, Physics, QC1-999
Abstract

Vertically aligned nanowire arrays, with high surface-to-volume ratio and efficient light-trapping absorption, have attracted much attention for photoelectric devices. In this paper, vertical β-Ga2O3 nanowire arrays with an average diameter/height of 110/450 nm have been fabricated by the inductively coupled plasma etching technique. Then a metal-semiconductor-metal structured solar-blind photodetector (PD) has been fabricated by depositing interdigital Ti/Au electrodes on the nanowire arrays. The fabricated β-Ga2O3 nanowire PD exhibits ∼10 times higher photocurrent and responsivity than the corresponding film PD. Moreover, it also possesses a high photocurrent to dark current ratio (Ilight/Idark) of ∼104 and a ultraviolet/visible rejection ratio (R260 nm/R400 nm) of 3.5 × 103 along with millisecond-level photoresponse times.

Published
2020
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4. Structural Characterization of Mesoporous Silica Nanofibers Synthesized Within Porous Alumina Membranes

Author

Pan Lijia, Shi Yi, Zheng Youdou, Gong Zhihong, Ji Guangbin, Zheng Mingbo, Chang Xiaofeng, and Dai Weijie

Subjects
Mesoporous silica, Nanofiber, Anodic aluminum oxide, P123, Template synthesis, Materials of engineering and construction. Mechanics of materials, TA401-492
Abstract

Abstract Mesoporous silica nanofibers were synthesized within the pores of the anodic aluminum oxide template using a simple sol–gel method. Transmission electron microscopy investigation indicated that the concentration of the structure-directing agent (EO20PO70EO20) had a significant impact on the mesostructure of mesoporous silica nanofibers. Samples with alignment of nanochannels along the axis of mesoporous silica nanofibers could be formed under the P123 concentration of 0.15 mg/mL. When the P123 concentration increased to 0.3 mg/mL, samples with a circular lamellar mesostructure could be obtained. The mechanism for the effect of the P123 concentration on the mesostructure of mesoporous silica nanofibres was proposed and discussed.

Published
2009
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5. A Lateral AlGaN/GaN Schottky Barrier Diode with 0.36 V Turn-on Voltage and 10 kV Breakdown Voltage by Using Double Barrier Anode Structure

Author

Xu, Ru, Chen, Peng, Zhou, Jing, Li, Yimeng, Li, Yuyin, Zhu, Tinggang, Chen, Dunjun, Xie, Zili, Ye, Jiandong, Xiu, Xiangqian, Zhang, Rong, and Zheng, Youdou

Subjects
Condensed Matter - Materials Science, Physics - Applied Physics
Abstract

In this letter, we demonstrate a lateral AlGaN/GaN Schottky barrier diode (SBD) on sapphire substrate with low turn-on voltage (Von) and high breakdown voltage (VBK). By using a double barrier anode (DBA) structure formed by the mixture of Platinum (Pt) and Tantalum (Ta), the Von of the SBD can be as low as 0.36 V with a leakage current of 2.5E-6 A/mm. Supported by the high-quality carbon-doped GaN buffer on sapphire, the VBK can reach more than 10 kV with the anode-to-cathode spacing of 85 {\mu}m. Combining the VBK and the specific on-resistance (Ron,sp) of 25.1 m{\Omega}.cm^2, the power figure of merit of the SBD can reach 4.0 GW/cm^2, demonstrating a great potential for the application in ultra-high-voltage electronics., Comment: 4 pages, 4 figures and 1 table. This work has ever been successfully submitted to the IEEE Electron Device Letters for possible publication in Jan. 2022, and the manuscript ID is EDL-2022-01-0014. Finally, it is suggested to be submitted to another journal such as IEEE TED

Published
2022

9. High power Figure-of-Merit, 10.6-kV AlGaN/GaN lateral Schottky barrier diode with single channel and sub-100-{\mu}m anode-to-cathode spacing

Author

Xu, Ru, Chen, Peng, Zhou, Jing, Li, Yimeng, Li, Yuyin, Zhu, Tinggang, Cheng, Kai, Chen, Dunjun, Xie, Zili, Ye, Jiandong, Liu, Bin, Xiu, Xiangqian, Han, Ping, Shi, Yi, Zhang, Rong, and Zheng, Youdou

Subjects
Condensed Matter - Materials Science, Physics - Applied Physics
Abstract

GaN-based lateral Schottky diodes (SBDs) have attracted great attention for high-power applications due to its combined high electron mobility and large critical breakdown field. However, the breakdown voltage (BV) of the SBDs are far from exploiting the material advantages of GaN at present, limiting the desire to use GaN for ultra-high voltage (UHV) applications. Then, a golden question is whether the excellent properties of GaN-based materials can be practically used in the UHV field? Here we demonstrate UHV AlGaN/GaN SBDs on sapphire with a BV of 10.6 kV, a specific on-resistance of 25.8 m{\Omega}.cm2, yielding a power figure of merit of more than 3.8 GW/cm2. These devices are designed with single channel and 85-{\mu}m anode-to-cathode spacing, without other additional electric field management, demonstrating its great potential for the UHV application in power electronics., Comment: 18 pages, 7 figures. This work has ever been successfully submitted to Nature Electronics for possible publication in July 2021, and the manuscript ID is NATELECTRON-21074250

Published
2021

11. Localized surface plasmon enhanced InGaN-based light-emitting diodes with polygonal Au/Al nanoparticles

Author

Mao, Xiaokang, Yu, Zhiguo, Che, Peng, Zhou, Jing, Li, Yuyin, Feng, Jianbo, Xie, Zili, Zhao, Hong, Chen, Dunjun, Xiu, Xiangqian, Wang, Ke, Shi, Yi, Zhang, Rong, and Zheng, Youdou

Subjects
Physics - Optics, Physics - Applied Physics
Abstract

Localized surface plasmons (LSPs) have played a significant role in improving the light emission efficiency of light emitting diodes (LEDs). In this report, polygonal nanoholes have been fabricated in the p-GaN layer of InGaN-based LEDs by using Ni nanoporous film as the etching mask, and then Au/Al metal nanoparticles are embedded in the nanoholes to form the LSP structure. The coupling between the LSP and the LED has been clearly observed. The results show that the light output of the LEDs has been increased by 46% at higher current injection condition, and together with a shift of the gain peak position to the LSP peak resonance energy. As the coupling distance is decreased from 60 nm to 30 nm, the maximum enhancement factor increases to 2.38. The above results indicate that the LSP from the polygonal metal nanoparticles is a kind of very promising structure to enhance the lighting performance of the InGaN-based LEDs., Comment: 7 pages, 5 figures. This work has ever been successfully submitted to Crystals for possible publication in Feb. 2021, and the manuscript ID is crystals-1129650

Published
2021

12. 2.5-kV AlGaN/GaN Schottky Barrier Diode on Silicon Substrate with Recessed-anode Structure

Author

Xu, Ru, Chen, Peng, Liu, Menghan, Zhou, Jing, Yang, Yunfei, Li, Yimeng, Ge, Cheng, Peng, Haocheng, Liu, Bin, Xie, Zili, Zhang, Rong, and Zheng, Youdou

Subjects
Physics - Applied Physics, Condensed Matter - Materials Science
Abstract

In this letter, we demonstrate high-performance lateral AlGaN/GaN Schottky barrier diodes (SBD) on Si substrate with a recessed-anode structure. The optimized rapid etch process provides results in improving etching quality with a 0.26-nm roughness of the anode recessed surface. By using the high work function metal Pt as the Schottky electrode, a low Von of 0.71 V is obtained with a high uniformity of 0.023 V for 40 devices. Supported by the flat anode recess surface and related field plate design, the SBD device with the anode-cathode spacing of 15 um show the Ron,sp of 1.53 mOhm.cm2 only, the breakdown voltage can reach 1592 V with a high power FOM (Figure-of-Merit) of 1656 MW/cm2. For the SBD device with the anode-cathode spacing of 30 um, the breakdown voltage can be as high as 2521 V and the power FOM is 1244 MW/cm2., Comment: 5 pages, 9 figures. This work has ever been successfully submitted to the IEEE Electron Device Letters for possible publication in Sep. 2019, and the manuscript ID is EDL-2019-09-2015. Finally, it is suggested to be submitted to another journal such as IEEE JEDS

Published
2020
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13. Current Kink Effect in β-Ga₂O₃ MOSFETs Induced by Incomplete Ionization of Donors

Author

Yu, Xinxin, Gong, Hehe, Zhou, Jianjun, Shen, Zhenghao, Ren, Fangfang, Chen, Dunjun, Ou, Xin, Gu, Shulin, Kong, Yuechan, Li, Zhonghui, Chen, Tangsheng, Zhang, Rong, Zheng, Youdou, and Ye, Jiandong

Abstract

In this article, the origin of severe drain–source current kink effect in $\beta $ -Ga2O3 MOSFETs has been exploited by means of temperature- and pulse-dependent current–voltage (I–V) analysis. By reducing the pulse biasing widths, whereby the self-heating effect was negligible, the output characteristics were free of kink but with a rather low drain–source current density ( ${I}_{\text {DS}}$ ) at a high drain voltage ( ${V}_{\text {DS}}$ ) of 30 V. The current kink effect started to occur with a direct-current power consumption of approximately 850 mW/mm. The elimination of kink features was also observed together with a large ${I}_{\text {DS}}$ at elevated temperatures over 100 °C. These observations indicate that the kink effect is strongly related to thermal activation of incomplete ionized donors by either the self-heating effect or external intentional heating stress rather than high electric field. In terms of temperature-dependent current output characteristics, the thermal activation energy is determined to be 136 meV, which is consistent with the reported unintentional donors with a high activation energy of 110 meV. It implies that additional electrons are thermally activated and emitted from the incomplete ionized donors in $\beta $ -Ga2O3 channel or buffer layers through the self-heating effect, contributing to the channel conductivity modulation and the consequent current kink effect. These findings may bridge the knowledge gap between charge transport mechanisms and the reliability degradation of $\beta $ -Ga2O3 power switches.

Published
2024
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16. 4H-SiC Tetra-Lateral Position Sensitive Detector for Ultraviolet Measurements

Author

Wang, Yifu, Yang, Peichen, Du, Haoyu, Xu, Weizong, Zhou, Dong, Ren, Fangfang, Chen, Dunjun, Zhang, Rong, Zheng, Youdou, and Lu, Hai

Abstract

In this work, a tetra-lateral 4H-SiC ultraviolet (UV) lateral-effect position-sensitive detector (PSD) formed by selective-area ion implantation has been manufactured and characterized. The PSD with an $8\times 8$ mm photosensitive area presents a low dark current of 6 pA, a fast rise time of $12.6~\mu $ s, a high detectivity of $2.0\times 10^{{13}}$ cm $\cdot $ Hz $^{{0.5}} \cdot $ W $^{-{1}}$ , and a high responsivity of 0.13 A/W at 275 nm at 0 V. By applying transimpedance amplifier processing circuits, the PSD presents good 2-D position capability for UV light spots with a nonlinearity of 9.8% within more than 75% of the photosensitive area. The PSD also shows obvious independence on the reverse bias voltage, the spot size, and the incident light power. The interaction of the electrodes of PSD is considered to be the reason for nonlinearity by comparing the output signals. Moreover, the applications of precise angle measurement have been realized using this device as a sensor.

Published
2024
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17. High-V TH E-Mode GaN HEMTs With Robust Gate-Bias-Dependent V TH Stability Enabled by Mg-Doped p-GaN Engineering

Author

Jin, Yulei, primary, Zhou, Feng, additional, Xu, Weizong, additional, Wang, Zhengpeng, additional, Zhou, Tianyang, additional, Zhou, Dong, additional, Ren, Fangfang, additional, Xia, Yuanyang, additional, Wu, Leke, additional, Li, Yiheng, additional, Zhu, Tinggang, additional, Chen, Dunjun, additional, Zhang, Rong, additional, Ye, Jiandong, additional, Zheng, Youdou, additional, and Lu, Hai, additional

Published
2023
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28. High-VTH E-Mode GaN HEMTs With Robust Gate-Bias-Dependent VTH Stability Enabled by Mg-Doped p-GaN Engineering

Author

Jin, Yulei, Zhou, Feng, Xu, Weizong, Wang, Zhengpeng, Zhou, Tianyang, Zhou, Dong, Ren, Fangfang, Xia, Yuanyang, Wu, Leke, Li, Yiheng, Zhu, Tinggang, Chen, Dunjun, Zhang, Rong, Ye, Jiandong, Zheng, Youdou, and Lu, Hai

Abstract

Highly stable threshold voltage $({V}_{\text {TH}})$ characteristics are an essential reliability requirement for p -GaN/AlGaN/GaN high-electron-mobility transistors (p-GaN HEMTs) to withstand various gate bias stresses for power applications. In this work, we demonstrate high- ${V}_{\text {TH}}$ (3.0 V) p-GaN HEMTs with robust ${V}_{\text {TH}}$ stability by p -GaN gate engineering via Mg doping and activation. The ${V}_{\text {TH}}$ degradation rates of the resulting device under both pulsed- ${I}/{V}$ and bias temperature instability (BTI) stress conditions are less than 10% at high temperatures up to 150°, which is much lower than that of conventional Schottky-type p -GaN HEMTs (20%–30%). Such notable ${V}_{\text {TH}}$ characteristics are due to the impact ionization (I.I.)-dependent hole compensation under certain gate stress, which effectively alleviates the electron trapping effect and reduces positive ${V}_{\text {TH}}$ shift. The I.I. occurring in the fully depleted p -GaN layer has been confirmed by both positive temperature-dependent gate breakdown characteristics and numerical simulations. Furthermore, shallow- and deep-level hole traps are identified in the gate-stack of high- ${V}_{\text {TH}}$ devices by performing the deep-level transient spectroscopy (DLTS) technique. Consequently, the trapping effect associated with hole traps may also alleviate the undesired electron-trapping-induced ${V}_{\text {TH}}$ shift. These results provide a critical understanding of the ${V}_{\text {TH}}$ stability of the high- ${V}_{\text {TH}}$ p -GaN HEMTs (HVT-HEMTs) and important design guidance for commercial device development.

Published
2023
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31. AlGaN Quantum Disk Nanorods with Efficient UV-B Emission Grown on Si(111) Using Molecular Beam Epitaxy

Author

Zhang, Dongqi, primary, Tao, Tao, additional, Sun, Haiding, additional, Li, Siqi, additional, Jia, Hongfeng, additional, Yu, Huabin, additional, Shao, Pengfei, additional, Li, Zhenhua, additional, Wu, Yaozheng, additional, Xie, Zili, additional, Wang, Ke, additional, Long, Shibing, additional, Liu, Bin, additional, Zhang, Rong, additional, and Zheng, Youdou, additional

Published
2022
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47. Low Leakage Current and High Breakdown Field AlGaN/GaN MIS-HEMTs Using PECVD-SiN x as a Gate Dielectric.

Author

Gao, Xiaohui, Guo, Hui, Wang, Rui, Pan, Danfeng, Chen, Peng, Chen, Dunjun, Lu, Hai, Zhang, Rong, and Zheng, Youdou

Subjects
STRAY currents, PLASMA-enhanced chemical vapor deposition, MODULATION-doped field-effect transistors, DIELECTRICS, GALLIUM nitride
Abstract

In this paper, SiNx film deposited by plasma-enhanced chemical vapor deposition was employed as a gate dielectric of AlGaN/GaN high electron mobility transistors (HEMTs). We found that the NH3 flow during the deposition of SiNx can significantly affect the performances of metal–insulator–semiconductor (MIS) HEMTs. Compared to that without using NH3 flow, the device with the optimized NH3 flow exhibited three orders of magnitude lower gate leakage current, two orders of magnitude higher ON/OF drain current ratio, and an increased breakdown field by 69%. In addition, an in situ N2 plasma surface treatment prepared prior to SiNx deposition can further improve DC performances of MIS-HEMTs to a very low gate leakage current of 10−9 mA/mm and a high ON/OFF drain current ratio up to 109 by reducing the interface state density. These results demonstrate the great potential for using PECVD-SiNx as a gate dielectric in GaN-based MIS-HEMTs. [ABSTRACT FROM AUTHOR]

Published
2022
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