2013 年 38 巻 2 号 p. 261-264
As electronic device dimensions are continuously reduced, new functions based on atomistic considerations can be implemented. Single-dopant transistors have been proposed based on a different mechanism as compared to conventional transistors, by making use of tunneling transport via individual dopant atoms located in nanoscale-channel transistors. However, typical dopants have shallow ground-state levels and thermally-activated transport becomes dominant at high temperatures. It is necessary to find a way to enhance the tunnel barrier height, i.e., to deepen the ground-state level, so that tunneling operation is maintained up to higher temperatures. In this work, as a first step, we use an atomistic simulation to extract information about the properties of dopants in nanostructures, in particular about the importance of channel design. For donors embedded in specifically-shaped channels, dielectric confinement effect is strong enough to ensure an enhancement of the tunnel barrier height. For the experimental study, we fabricated and characterized electrically nanoscale silicon-on-insulator field-effect transistors with ultra-thin stub-shaped channels. It was found that tunneling operation can be maintained even at elevated temperatures (approximately 100 K), which makes single-dopant transistors promising for more practical applications.
