Tunneling in Systems of Coupled Dopant-Atoms in Silicon Nano-devices

Abstract

Following the rapid development of the electronics industry and technology, it is expected that future electronic devices will operate based on functional units at the level of electrically active molecules or even atoms. One pathway to observe and characterize such fundamental operation is to focus on identifying isolated or coupled dopants in nanoscale silicon transistors, the building blocks of present electronics. Here, we review some of the recent progress in the research along this direction, with a focus on devices fabricated with simple and CMOS-compatible-processing technology. We present results from a scanning probe method (Kelvin probe force microscopy) which show direct observation of dopant-induced potential modulations. We also discuss tunneling transport behavior based on the analysis of low-temperature I-V characteristics for devices representative for different regimes of doping concentration, i.e., different inter-dopant coupling strengths. This overview outlines the present status of the field, opening also directions toward practical implementation of dopant-atom devices.

Coulomb blockade and hopping transport behaviors of donor-induced quantum dots in junctionless transistors*

“…[4,5] On the other hand, this discreteness brings attractive applications based on the interplay between the potential modulations induced by individual dopants. [6,7] Single-electron transport mediated by individual dopants in silicon nanowire transistors was observed in previous experiments. [8][9][10][11] Dopant-induced quantum dot (QD) is considered as a promising candidate for the next generation of nano-electrical device, becoming the focus of quantum information.…”

Single-Charge Tunneling in Codoped Silicon Nanodevices

“…Figure 1 shows an overview of the space defined by the two doping concentrations, N D and N A , ranging from 10 17 cm −3 (corresponding to inter-dopant distances on the order of 20 nm) to more than 10 20 cm −3 (close to the solid solubility limits, corresponding to inter-dopant distances on the order of 2 nm). Assuming that this space is defined in a thin nanoscale Si layer, one can delineate several regimes that reveal different natures of dopants: (i) “atom” nature, where each individual dopant-atom is practically isolated from the others—at low concentrations, well below the metal-insulator transition (MIT) [ 25 , 26 ]; (ii) “molecule” nature, where several dopants can be found coupling to each other into “clusters” (with molecule-like behavior)—at medium concentrations, slightly below or above MIT [ 27 , 28 ]; (iii) “domain” nature, where a larger number of dopants dominantly define n -type or p -type zones (domains) [ 29 ] due to the uncorrelated distribution of opposite-polarity dopants—at higher concentrations, approaching the solid-solubility limits. The mid-line in this space corresponds to the full (complete) compensation.…”