Nov 21, 2013
Rare-Earth oxides for silicon-germanium quantum dot memories
Flash memory is predicted to be the dominant form of non-volatile memory in the future - thanks to its improved speed and lower power consumption, and modern flash memory devices using nanocrystal floating-gate MOSFETs could be real alternatives to magnetic and optical storage media. Conventional flash memory cells designed for 10-year data retention use a relative thick tunnel oxide to prevent charge leakage through defects, which leads to a compromised read/write speed and endurance characteristics. Incorporating quantum dots into the floating gate results in the reduction of charge leakage and power dissipation with enhanced programming speed. Researchers in India and Germany have now unveiled the memory characteristics of silicon and silicon-germanium quantum dots (QDs) embedded in epitaxial Rare-Earth oxide gadolinium oxide (Gd2O3) grown on Si (111) substrates. Multilayer Si as well as single layer Si1-xGex (where x=0.6) QDs show excellent memory characteristics, making them attractive for next-generation flash-floating-gate memory devices.
Researchers generally use SiO2 and high-dielectric oxides like aluminium oxide (Al02O3) and hafnium oxide (HfO2) for memory structures. Our groups have chosen rare-Earth GdO2O3 oxide, which can be epitaxially deposited on Si (111) for integrating Si and SiGe QDs. We used capacitance-voltage and conductance-voltage measurements to characterize the effect of quantum dots, interfaces, and trapped charges on the charge storage properties.
Our analyses show that multilayer Si QDs exhibit superior properties compared with their single-layer counterparts, and that incorporating Ge further enhances device performance. This is the first report on the charge storage behaviour using multilayer quantum dots within epitaxial rare-Earth based oxides exhibiting excellent memory characteristics.
The researchers presented their results in the journal Nanotechnology (in press).
Controlled quantum conductance in resistive switches highlights opportunity for atomic-scale memory (Mar 2012)
I-V study details flexible organic memory device (Jun 2009)
Nanowire memory could write data faster (Dec 2006)
About the author
Santanu Manna, Rakesh Aluguri and Ajit Katiyar are PhD students in the Department of Physics & Meteorology, Indian Institute of Technology Kharagpur, India. Dr Samaresh Das, an ex-student of the group is currently a research scientist in the Quantum Information Processing team at Hitachi Cambridge Laboratory, University of Cambridge, UK. Dr. Apurba Laha is assistant professor in the Department of Electrical Engineering, Indian Institute of Technology Bombay, India. Dr. H. J. Osten is professor and head of the Institute of Electronic Materials and Devices, Leibniz University, Germany. Dr. Samit K Ray is professor and head of the Department of Physics, Indian Institute of Technology Kharagpur, India.