Doping induced threshold voltage and I<sub>ON</sub>/I<sub>OFF</sub> ratio modulation in surrounding gate MOSFET for analog applications
Amit Das, Binod Kumar Kanaujia, S. S. Deswal, Sonam Rewari, Rajeev Gupta
Abstract
This paper gives a detailed and comprehensive insight for the simulation based investigation of doping induced modulation of the threshold voltage and I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ON</inf> /I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">OFF</inf> ratio in a silicon based surrounding gate metal oxide semiconductor field effect transistor (SG-MOSFET). This work explores the two important DC characteristics i.e. threshold voltage and I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ON</inf> /I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">OFF</inf> ratio which are important to investigate the analog performance of MOSFET. The current study shows that the low doping of source, channel and drain results in low threshold voltage but also, decreases the I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ON</inf> /I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">OFF</inf> ratio. Interestingly, keeping the drain doping higher than the source doping improves the threshold voltage but degrades the I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ON</inf> /I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">OFF</inf> ratio. The maximum change in threshold voltage and I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ON</inf> /I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">OFF</inf> ratio is approximately 430 mV and 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> times respectively which is obtained when the doping of the source, channel and drain are changed simultaneously by a factor of 1:10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> . The doping of source, channel and drain can significantly affect the threshold voltage and I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ON</inf> /I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">OFF</inf> ratio in short channel devices which necessitates the need of doping optimization to control both these characteristics.