Silicon field-effect transistors have now reached gate lengths of only a few tens of nanometers, containing a countable number of dopants in the channel. Such technological trend brought us to a research stage on devices working with one or a few dopant atoms. In this work, we review our most recent studies on key atom devices with fundamental structures of silicon-on-insulator MOSFETs, such as single-dopant transistors, preliminary memory devices, single-electron turnstile devices and photonic devices, in which electron tunneling mediated by single dopant atoms is the essential transport mechanism. Furthermore, observation of individual dopant potential in the channel by Kelvin probe force microscopy is also presented. These results may pave the way for the development of a new device technology, i.e., single-dopant atom electronics.
We have comparatively studied the effects of electron injection in individual phosphorus-donor potential wells at 13 K and 300 K by Kelvin probe force microscopy in silicon-on-insulator metal-oxide-semiconductor field-effect-transistors. As a result, at 13 K, localized single-electron filling into the phosphorus-donor potential well is found, reflecting single-electron tunneling transport through individual donors, whereas at 300 K, spatially extended and continuous electron filling over a number of phosphorus-donors is observed, reflecting drift-diffusion transport.
Electronic potential measurements performed by low-temperature Kelvin probe force microscopy on silicon-on-insulator lateral nanoscale pn junctions are presented. The electronic potential landscape contains a region of enhanced potential induced by interdiffused dopants with deeper ground-state levels compared to bulk. The discrete dopant distribution can be observed in specific line profiles. In most line profiles, time-dependent potential fluctuations due to charging and discharging of dopants give rise to a localized-noise area corresponding to the depletion region.
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