Chao Chen

University of Electronic Science and Technology of China, Hua-yang, Sichuan, China

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Publications (12)14.85 Total impact

  • Tao Wang · He Yu · Chao Chen · Yang Wang · Yadong Jiang
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    ABSTRACT: In this work, a modeling for reactive sputtering has been presented where the non-uniform current density is taken into account. The model in this paper can be used to understand the process of reactive magnetron sputtering. The results are compared with those that assume uniform discharge current density distributed on the target. It can be concluded that the process with the non-uniform discharge density shows a higher flow of gas reactive when occurring the hysteresis behavior. In addition, a study of the radial variation of the target composition in metallic and compound mode is also performed.
    7th International Symposium on Advanced Optical Manufacturing and Testing Technologies (AOMATT 2014); 09/2014
  • Chao Chen · Xing Zhao Liu
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    ABSTRACT: The effects of low energy (1.8 MeV) electron irradiation on enhancement-mode (E-mode) AlGaN/GaN high electron mobility transistors (HEMTs) have been reported. When the dose up to 1.1×1016 cm-2, the saturation drain current and maximal transconductance of E-mode AlGaN/GaN HEMTs increase after irradiation. However, almost no change of threshold voltage and gate leakage current is observed. The results are explained by the creation of positive charges in the AlGaN layer by ionizing energy loss, especially the creation of N vacancies and Ga vacancies by non-ionizing energy loss. Moreover, low-energy electron irradiation could recover the electron mobility.
    09/2013; 774-776:876-880. DOI:10.4028/
  • Xingzhao Liu · Chao Chen · Jun Zhu · Wanli Zhang · Yanrong Li
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    ABSTRACT: This paper presents the modulation effects of charged dielectrics on performance of AlGaN/GaN metal-insulator-semiconductor high-electron mobility transistors (MIS HEMTs). Using fluorinated Al2O3 as gate dielectrics, the threshold voltage of the devices shifted from conventional depletion-mode (D-mode) MIS HEMTs to enhancement-mode (E-mode) MIS HEMTs. And the threshold voltage (Vth) increased more positively by using a successive deposition of Al2O3 layer on the fluorinated Al2O3 as a blocking oxide layer. It was found that not the surface potential but rather the negative charges in the Al2O3 gate dielectrics are primary factors responsible for conversion from D-mode MIS HEMTs to E-mode MIS HEMTs by using fluorinated Al2O3 as gate dielectrics. The positive Vth modulation was attributed to the built-in electric field which was introduced by the charged dielectrics.
    Journal of Applied Physics 07/2013; 114(2). DOI:10.1063/1.4812220 · 2.18 Impact Factor
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    ABSTRACT: The enhancement-mode (E-mode) AlGaN/GaN metal-insulator-semiconductor high-electron mobility transistors (MISHEMTs) were realized by using fluorinated Al2O3 as gate dielectrics. The variations in binding-energy spectrum and valance-band spectrum in fluorinated-Al2O3/AlGaN/GaN are studied in this Letter, providing insights to mechanism underlying drastic threshold voltage (Vth) modulation of AlGaN/GaN MISHEMTs with fluorinated Al2O3 gate dielectrics. It was found that not the surface potential but rather the negative charges in Al2O3 gate dielectrics are the primary factor responsible for conversion from depletion-mode (D-mode) to E-mode AlGaN/GaN MISHEMTs by using fluorinated Al2O3 as gate dielectrics.
    Applied Physics Letters 03/2012; 100(13). DOI:10.1063/1.3699029 · 3.30 Impact Factor
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    ABSTRACT: High-performance enhancement-mode (E-mode) AlGaN/GaN metal-insulator-semiconductor HEMTs (MISHEMTs) were realized by using fluorinated Al<sub>2</sub>O<sub>3</sub> thin films as gate dielectrics. The depth profile of Fluoride atoms determined by X-ray photoelectron spectroscopy showed that the fluorine (F) ions were incorporated into the surface (approximately 2 nm) of the Al<sub>2</sub>O<sub>3</sub> gate dielectrics. With proper amount of F-ion incorporation, the threshold voltage of MISHEMTs shifted from - 4.8 to 0.11 V, converting depletion-mode (D-mode) MISHEMTs to E-mode ones. The E-mode MISHEMTs exhibited high performances including a high transconductance value of 153 mS/mm and a large saturated drain-current value I <sub>ds</sub> of 547 mA/mm. This paves a new way to fabricate E-mode AlGaN/GaN MISHEMTs and allows the monolithic integration of E/D-mode MISHEMTs for analog integrated circuits.
    IEEE Electron Device Letters 11/2011; 32(10-32):1373 - 1375. DOI:10.1109/LED.2011.2162933 · 2.75 Impact Factor
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    ABSTRACT: An AlGaN/GaN metal-insulator-semiconductor heterostructure field-effect transistor (MISHFET) with about 40 nm Al2O3 for both surface passivation and gate dielectric has been investigated and compared with the regular metal-semiconductor heterostructure field-effect transistor (MESHFET). The output characteristic measurements have shown that the MISHFET yielded 34% increase of the saturation drain current compared to the MESHFET. The Hall effect measurements of AlGaN/GaN two-dimensional electron gas (2DEG) coated with Al2O3 thin films indicated an increase of mobility and density of 2DEG, and thus a decrease of the parasitic series resistance. The XRD analysis of the AlGaN/GaN heterostructure showed that strain was introduced into the AlGaN barrier layer with Al2O3 coating. The energy band calculations showed that the biaxial tensile stress should possibly be the main mechanism for the performance improvement of the MISHFET.
    Semiconductor Science and Technology 05/2011; 26(8):085023. DOI:10.1088/0268-1242/26/8/085023 · 2.19 Impact Factor
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    ABSTRACT: Uncooled infrared detectors are applied widely in both civilian and military. Recently, novel microbolometers composing of two planes located at diffeent levels were proposed to improve the performance of the detectors. In this paper, such two-layer microbolometers were simulated by finite element analysis. Results reveal that when SiO2 film is utilized as the isolating and supporting material located at the lower bridge plane, the temperature rise of the pixel reaches 3∼5 times higher than those in the conventional one-layer microbolometers, and the maximum IR absorptance increases for about 40%. Therefore, these two-layer microbolometers are helpful for significantly improving the thermal and optical properties. However, their structural stability turns poor. Consequently, the mechanical properties for such two-layer microbolometers should be enhanced in practical applications.
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    ABSTRACT: A nearly square-like ferroelectric hysteretic loop of spin-coated and crystallized poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) with a remnant polarization 2 Pr of 20 µC cm−2 was obtained. The electrical transport properties of the P(VDF-TrFE)/AlGaN/GaN structure were investigated. The results show that the carrier density Ns, mobility μ, and resistivity ρ of AlGaN/GaN 2DEG can be directly and strongly modulated by an external electric field via the ferroelectric polymer P(VDF-TrFE): the Ns, μ, and ρ of AlGaN/GaN 2DEG exhibit closed hysteretic loops under a closed external electric field and the carrier density can be tuned as large as 235% only by changing the external electric field.
    Semiconductor Science and Technology 12/2010; 26(2):025010. DOI:10.1088/0268-1242/26/2/025010 · 2.19 Impact Factor
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    ABSTRACT: The way of improving the thickness uniformity of the thin film deposited by magnetron sputtering system is presented in this paper. A simple model for the magnetron sputtering system with a baffle between cathode target and substrate is described. Based on this model, it is possible to predict the relative deviation of film thickness with this baffle-model by taking the shape and size of baffle into the consideration. The purpose of this article is to explain how different baffle parameters affect the uniformity of thin film using the method of finite element with rectangle target in this magnetron system. It is found that there may exist optimum baffle conditions where the relative deviation of thin film thickness is less than 3 % with a diameter of Phi 150 mm substrate.
    Proceedings of SPIE - The International Society for Optical Engineering 05/2010; DOI:10.1117/12.866615 · 0.20 Impact Factor
  • Henan Zhao · Tao Wang · He Yu · Chao Chen · Yadong Jiang
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    ABSTRACT: In this article, the practical structure of two-color microbolometers for uncooled infrared detection was considered, a mathematical model to calculate infrared absorptance was described. The optical characteristic of multilayer structure consisting of Nitride (SiNx) infrared absorber film/ Vanadium (VOx) heat sensitive film/ SiNx support film/ the first optical resonant cavity/ a tunable reflecting Al micromirror/ the second optical resonant cavity /a bottom electrode made up of Al was investigated. According to optical admittance matrix theory, relation between infrared absorber film thickness, the first optical resonant cavity of two-color microbolometer and infrared absorptivity was simulated by MATLAB software.
    Proceedings of SPIE - The International Society for Optical Engineering 05/2010; 7658. DOI:10.1117/12.866319 · 0.20 Impact Factor
  • Journal of Micro/ Nanolithography, MEMS, and MOEMS 01/2010; 9(3). DOI:10.1117/1.3455343 · 1.43 Impact Factor
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    ABSTRACT: A tunable reflecting micromirror made up of two layers of Al and Si3N4 is designed to suspend between the silicon substrate and the heat sensitive membrane for measuring the actual temperature and color of an object based on comparison of two wavelength response windows, 3-5 mum and 8-12 mum. The micromirror, switching between two positions by an applied electrostatic voltage, provides a response to two wavelength windows by tuning the optical tunable resonant cavity. With different distances between the micromirror and the bottom electrode, the total capacitance of the tunable micromirror is gained based on electromagnetic analysis and theoretical equation. The pull-in voltage is calculated as 8.21 V by electrostatic-mechanical coupling analysis. But if the voltage is increased to about 9.73 V, the micromirror will touch the bottom electrode by pull-in behavior. At last, the vibration modes of the tunable micromirror are simulated using ANSYS, and the fabrication process flow of the two-color microbolometer is theoretically demonstrated.
    Proceedings of SPIE - The International Society for Optical Engineering 11/2009; DOI:10.1117/12.837798 · 0.20 Impact Factor