Chao Chen

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

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Publications (6)13.14 Total impact

  • 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 · 2.19 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 · 3.52 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 · 3.02 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 · 2.21 Impact Factor
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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 · 2.21 Impact Factor