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Tristate Memory Using Ferroelectric–Insulator–Semiconductor Heterojunctions for 50% Increased Data Storage
Author(s) -
Park Min Hyuk,
Lee Hyun Ju,
Kim Gun Hwan,
Kim Yu Jin,
Kim Jeong Hwan,
Lee Jong Ho,
Hwang Cheol Seong
Publication year - 2011
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.201101073
Subject(s) - ferroelectric ram , materials science , non volatile memory , ferroelectricity , heterojunction , semiconductor memory , optoelectronics , insulator (electricity) , electrode , scaling , memory cell , transistor , nanotechnology , electrical engineering , voltage , dielectric , computer science , computer hardware , chemistry , geometry , mathematics , engineering
Ferroelectric random‐access memory (FeRAM) is considered to be one of the best candidates for universal memory. However, difficult scaling of the memory cell size has hindered the realization of high density FeRAM. Given that size scaling is inherently limited by the complicated crystal structure and processing of ferroelectric materials, the highly stable and step‐wise three memory state of one cell can be another pathway to high‐density FeRAM. A feasible structure and actual operation of a tristate memory function for high‐density FeRAM is presented that uses stacked ferroelectric Pb(Zr,Ti)O 3 /insulating Al 2 O 3 /semiconducting ZnO layers with Pt top and bottom electrodes. The complicated electrical responses of the stacked structure to external stimuli are well understood based on the separated trapping of the compensating charges at the Pb(Zr,Ti)O 3 /Al 2 O 3 and Al 2 O 3 /ZnO interfaces and the discrete dissipation of the trapped charges during polarization switching in one direction. This unique function of the structure induces three discrete charge states that can be used to increase the memory density by 50% compared to conventional FeRAM at a given cell size.