Solution-Processed La Alloyed ZrOx High-k Dielectric for High-Performance ZnO Thin-Film Transistors
Md Mobaidul Islam, Jewel Kumer Saha, Ravindra Naik Bukke, Mehedi Hasan, Mohammad Masum Billah, Narendra Naik Mude, Arqum Ali, Jin Jang
Abstract
We report La alloyed ZrO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> high-k gate insulator (GI) for ZnO thin-film transistors (TFTs) by solution-process. The La concentration in ZrO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> is varied from 0 to 7.5% for optimum device performance. The atomic force microscopy and X-ray photoelectron spectroscopy analysis of 5% La alloyed ZrO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> GI show smooth surface with higher metal-oxide (M-O) bonds and reduced defect density in the bulk compared with pristine ZrO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> . Therefore, ZnO TFT using 5% La alloyed ZrO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> GI exhibits hysteresis-free device performance, with saturation mobility of 11.58cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> /V · s, 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> ratio of 2.67 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8</sup> , threshold voltage of 1.25V, and subthreshold swing of 249mV/dec. We also achieve highly stable ZnO TFTs under positive bias stress using 5% La alloyed ZrO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> GI.