All existing transistors are based on the use of semiconductor junctions formed by introducing dopant atoms into the semiconductor material. As the distance between junctions in modern devices drops below 10 nm, extraordinarily high doping concentration gradients become necessary. Because of the laws of diffusion and the statistical nature of the distribution of the doping atoms, such junctions represent an increasingly difficult fabrication challenge for the semiconductor industry. Here, we propose and demonstrate a new type of transistor in which there are no junctions and no doping concentration gradients. These devices have full CMOS functionality and are made using silicon nanowires. They have near-ideal subthreshold slope, extremely low leakage currents, and less degradation of mobility with gate voltage and temperature than classical transistors.

For more than four decades, transistors have been shrinking exponentially in size, and therefore the number of transistors in a single microelectronic chip has been increasing exponentially. Such an increase in packing density was made possible by continually shrinking the metal-oxide-semiconductor field-effect transistor (MOSFET). In the current generation of transistors, the transistor dimensions have shrunk to such an extent that the electrical characteristics of the device can be markedly degraded, making it unlikely that the exponential decrease in transistor size can continue. Recently, however, a new generation of MOSFETs, called multigate transistors, has emerged, and this multigate geometry will allow the continuing enhancement of computer performance into the next decade.

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We report on spectroscopy of a single dopant atom in silicon by resonant tunneling between source and drain of a gated nanowire etched from silicon on insulator. The electronic states of this dopant isolated in the channel appear as resonances in the low temperature conductance at energies below the conduction band edge. We observe the two possible charge states successively occupied by spin-up and spin-down electrons under magnetic field. The first resonance is consistent with the binding energy of the neutral D 0 state of an arsenic donor. The second resonance shows a reduced charging energy due to the electrostatic coupling of the charged D ÿ state with electrodes. Excited states and Zeeman splitting under magnetic field present large energies potentially useful to build atomic scale devices. DOI: 10.1103/PhysRevLett.97.206805 PACS numbers: 73.21.ÿb, 61.72.Vv Dopant atoms are essential in semiconductor technology since they provide extrinsic charges necessary to create devices such as diodes and transistors. Nowadays the size of these electronic devices can be made so small than the discreteness of doping can influence their electrical properties [1]. On the other hand, it may be an important breakthrough if a dopant could be used as the functional part of a device instead of just providing charges. As an example, dopant-based spin qubits in silicon are possible candidates for quantum computation [2,3] thanks to their longer spin coherence time [4] as compared to twodimensional quantum dots defined by top gates in III=V heterostructures [5,6]. Although dopants are well known in bulk semiconductors, specific questions arise in the context of nanoscale devices like the reduced lifetime of the twoelectron state under electric field involved by readout schemes of spin qubits [7]. The aim of this work is to study the electronic states of single dopants in gated silicon nanostructures to bring information useful for these issues.Electron tunneling through isolated impurities has been observed previously in two-terminal devices such as GaAs= Al; Ga As double barrier heterostructures [8,9]. Here we present experimental results on electron transport through the localized states of individual n-type dopants in silicon nanowires. In contrast to previous studies, our devices have a three-terminal configuration with source, drain, and gate electrodes allowing a detailed investigation of charge, orbital, and spin states. In particular, we observe both the neutral D 0 and negatively charged D ÿ states, and compare their binding energy with the case of bulk dopants. This work provides a quantitative description of the electronic properties of a single dopant connected to electrodes in a gated nanostructure. This is the first transport experiment measuring the charge states of a real atomic system with a 1=r attracting Coulomb potential, thus very different from quantum dots with harmonic potentials.Our devices are 60 nm tall crystalline silicon wires (fins) with large contacts patterned by 193 nm optical lithography and ...

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