Guidelines for Ferroelectric-Semiconductor Tunnel Junction Optimization by Band Structure Engineering
Pengying Chang, Gang Du, Jinfeng Kang, Xiaoyan Liu
Abstract
Tunneling processes of ferroelectric tunnel junction (FTJ) based on metal-ferroelectric-insulator-semiconductor (MFIS) stack are studied for both n- and p-type semiconductor electrodes using experimentally calibrated model. In the model, the calculation of ON- ( J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mathrm ON</sub> ) and OFF-current ( J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mathrm OFF</sub> ) in MFIS-FTJ considers the electron tunneling from both conduction (CBE) and valence band (VBE), and hole tunneling from the valence band (VBH). Depending on metal work function, doping concentration and remnant polarization, the conduction modes in both n- and p-type MFIS can respectively be classified according to the contribution of minority carriers in semiconductor. The optimal tunneling electroresistance (TER) ( ≈ J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mathrm ON</sub> /J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mathrm OFF</sub> ) for the n-type device is achieved, when semiconductor works under depletion/accumulation state driven by polarization reversal. With respect to its p-type counterpart, the accumulation/strong inversion state is preferable. The underlying physics are revealed, that if semiconductor goes into the strong inversion, the tunneling of VBH will increase the J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mathrm OFF</sub> and decrease the TER ratio in n-type device, whereas the tunneling of CBE will increase the J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mathrm ON</sub> and thus TER ratio in p-type device. Guided by the model, the band structure engineering of MFIS structure is provided to design and optimization of FTJ performance.