Self-induced ferroelectric 2-nm-thick Ge-doped HfO2 thin film applied to Ge nanowire ferroelectric gate-all-around field-effect transistor

• Published in: Applied physics letters 2020-12, Vol.117 (26)
• Main Authors: Lin, Yi-Wen, Sun, Chong-Jhe, Chang, Hao-Hsiang, Huang, Yu-Hsien, Yu, Tung-Yuan, Wu, Yung-Chun, Hou, Fu-Ju
• Format: Article
• Language: English
• Subjects: Aluminum oxide; Applied physics; Crystallization; Current leakage; Dielectric properties; Electric fields; Ferroelectric materials; Ferroelectricity; Field effect transistors; Germanates; Germanium; Hafnium oxide; Integrated circuits; Leakage current; Nanowires; Photoelectrons; Piezoelectricity; Power integrated circuits; Semiconductor devices; Thin films; Transistors
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/5.0029628

This paper reports a self-induced ferroelectric 2-nm-thick Ge-doped HfO2 (Ge:HfO2) thin film. Ge thermal desorption, incorporation into HfO2, and further Ge:HfO2 crystallization were all performed through rapid thermal annealing simultaneously. The ferroelectric property of a 2-nm-thick Ge:HfO2/2-nm-thick Al2O3 dielectric stack was confirmed using the polarization-electric field measurement. X-ray photoelectron spectroscopy was used to confirm that Ge bonded to HfO2 as Hf-germanates. Piezoresponse force microscopy was used to demonstrate the piezoelectric property of Ge:HfO2/Al2O3. Furthermore, a dielectric stack of Ge:HfO2/Al2O3 was applied as a gate insulator in a Ge nanowire gate-all-around ferroelectric field-effect transistor (Ge NW Fe-GAAFET). The device exhibited a minimum steep-sub-threshold slope of 47 mV/dec, a high ION/IOFF ratio of >106, and low gate leakage current; moreover, it was free of a drain-induced barrier lowering effect. The proposed self-induced ferroelectric Ge:HfO2 Ge NW Fe-GAAFET is feasible for future ultra-low power integrated circuit applications.