Junctionfree Gate Stacked Vertical TFET Hydrogen Sensor at Room Temperature
Sukanya Ghosh, Lintu Rajan, Arathy Varghese
Abstract
Presented through this work is an investigation of junctionfree gate-stacked (SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> + high-k) double gated vertical tunnel field-effect transistor (JF-GS-VTFET) with focus on its hydrogen (H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) sensing performance at room temperature (RT) for the first time. JF-GS-VTFET with vertically characterized channel length feature minimizes short channel effects (SCEs), elevates gate controllability over regular TFETs without the presence of any sharp doping gradient. A systematical study of the sensing performance is demonstrated through effective variations in Palladium (Pd) and Gold (Au) catalytic metal gate work functions corresponding to the concentration of hydrogen appearing at the gate metal surface. A concentration dependent thorough analysis has been illustrated in terms of energy band, potential, transfer and transient characteristics. Sensing capability of the device have been analyzed in terms of variations in detecting parameters such as transconductance (g <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sub> ), off current, on current, threshold voltage and sub-threshold slope in presence of the target gas using SILVACO ATLAS TCAD. At 1.04 ppm H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> gas concentration, the optimally designed sensor exhibits high I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ON</sub> /I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">OFF</sub> ratios in the order of ∼ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${10}^{13}$</tex-math></inline-formula> and ∼ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${10}^{11}$</tex-math></inline-formula> , high g <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sub> sensing responses of 99.98% and 98.93%, high off current sensing responses of ∼ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$1.895 \times {10}^4{\bm{\ }}$</tex-math></inline-formula> and ∼1 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$.47 \times {10}^4$</tex-math></inline-formula> , better sub-threshold swing sensing responses of ∼0.71 and ∼0.55, increased threshold voltage sensing responses of ∼0.27 and ∼0.25 for Pd and Au metal gates respectively at RT. Perceptible outcomes in terms of interface trap charge density have also been presented to recognize RT H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> sensing.