Ultrathin-Body TiO2 Thin Film Transistors With Record On-Current Density, ON/OFF Current Ratio, and Subthreshold Swing via O2 Annealing

Abstract

In this letter, we report ultrathin-body(~15 nm) TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> thin film transistors (TFTs) with unprecedented electrical performance: ON-current density (I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</sub> ) of 16.7 mA/mm, ON/OFF current ratio (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> ) of 1.2 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">9</sup> and subthreshold swing (SS) of 101 mV/dec. The TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> channel layer was deposited by thermal atomic layer deposition (ALD) followed by post-annealing in O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ambient. The material characterizations indicate the formation of anatase TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> polycrystalline films and a lack of detectable oxygen vacancies, which could have acted as charging traps in channel and channel/dielectric interface, benefiting the ION and the SS. These high-performance ultrathin-body TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> TFTs open a new venue in many applications such as high-resolution display and radiofrequency identification (RFID) tag, where high on currents and steep SS are required.