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Low Gate Leakage Current HFET Structure Fabricated by Using a Step-free Airbridge Gate Process
Feng-Tso Chien,Chien-Liang Chan,Chi-Ling Wang,Chien-Nan Liao,Yao-Tsung Tsai,Hsien-Chin Chiu 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.56 No.3
Conventional heterostructure field-effect transistors (HFETs) have a high gate leakage current due to the gate electrode being in contact with the exposed channel layer and with the carrier-providing layer on the mesa sidewall. In this study, we use a new step-free (SF) air-bridge gate structure to reduce the gate leakage and improve the breakdown voltage. The proposed structure does not increase any MASKs as compared with the conventional process. In addition, this new structure promises a gate-source capacitance smaller than those of conventional heterostructure FET devices. Consequently, the high-frequency performance of the HFETs using the proposed structure can be improved.
Y.C. Huang,M.D. TuMuli Lulios,Chu-Ho Chang,M. Nasir Noor,Jen-Chung Shao,Chien-Liang Chiu,Tsair-Fwu Lee,Renata Wang 국제구조공학회 2024 Structural Engineering and Mechanics, An Int'l Jou Vol.90 No.3
This research explores a new finite element model for the free vibration analysis of bi-directional functionally graded (BDFG) beams. The model is based on an efficient higher-order shear deformation beam theory that incorporates a trigonometric warping function for both transverse shear deformation and stress to guarantee traction-free boundary conditions without the necessity of shear correction factors. The proposed two-node beam element has three degrees of freedom per node, and the inter-element continuity is retained using both C1 and C0 continuities for kinematics variables. In addition, the mechanical properties of the (BDFG) beam vary gradually and smoothly in both the in-plane and out-of-plane beam’s directions according to an exponential power-law distribution. The highly elevated performance of the developed model is shown by comparing it to conceptual frameworks and solution procedures. Detailed numerical investigations are also conducted to examine the impact of boundary conditions, the bi-directional gradient indices, and the slenderness ratio on the free vibration response of BDFG beams. The suggested finite element beam model is an excellent potential tool for the design and the mechanical behavior estimation of BDFG structures.