Effects of Channel Length Scaling on the Signal-to-Noise Ratio in FET-Type Gas Sensor With Horizontal Floating-Gate

Abstract

We investigate the channel length ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${L}$ </tex-math></inline-formula> ) scaling effects on the signal-to-noise ratio (SNR) of the field-effect-transistor (FET)-type gas sensor with a horizontal floating-gate. A sensing layer, 15 nm of indium-gallium-zinc-oxide thin film, is deposited by the radio frequency sputtering method. Nitrogen dioxide is used as a target gas. The low-frequency noise characteristics of the FET-type gas sensor are explained by the carrier number fluctuation model with correlated mobility fluctuation. The SNR is proportional to the square root of the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${L}$ </tex-math></inline-formula> of the FET transducer. The result provides important guidelines in designing the sensor platform in FET-type gas sensors.