Abstract
Metallic channel transistors have been proposed as the candidate for sub-10 nm technology node. However, the conductivity modulation in metallic channels can only be observed at low temperatures usually below 100 K. In this study, room-temperature field effect and modulation of the channel resistance was achieved in the metallic channel transistors, in which the oxygen-doped TiN ultrathin-body channels were prepared by the atomic layer delta doping and deposition (AL3D) with precise control of the channel thickness and electron concentration. The decrease of channel thickness leads to the reduction in electron concentration and the blue shift of absorption spectrum, which can be explained by the onset of quantum confinement effect. The increase of oxygen incorporation results in the increase of interband gap energy, also giving rise to the decrease in electron concentration and the blue shift of absorption spectrum. Because of the significant decrease in electron concentration, the screening effect was greatly suppressed in the metallic channel. Therefore, the channel modulation by the gate electric field was achieved at room temperature due to the quantum confinement and suppressed screening effect with the thickness down to 4.8 nm and the oxygen content up to 35% in the oxygen-doped TiN ultrathin-body channel.
Highlights
With the rapid evolution of semiconductor technology down to the sub-10 nm technology node, nanoscale transistors based on new structures and materials have been explored[1,2,3,4,5,6,7,8,9,10,11]
The blue shift of the PL spectra of the Titanium nitride (TiN) nanoparticles has been observed with the decreasing particle sizes from 20 nm to 5.4 nm, which was deduced from the quantum confinement effect[42,43,44,45,46,47]
The decrease in the electron concentration in the oxygen-doped TiN layers might be explained by the reduction in the density of states with the decreasing film thickness because of the quantum confinement effect
Summary
With the rapid evolution of semiconductor technology down to the sub-10 nm technology node, nanoscale transistors based on new structures and materials have been explored[1,2,3,4,5,6,7,8,9,10,11]. One of the possible candidates for sub-10 nm devices is the junctionless transistors (JLTs), in which an ultrathin semiconductor body with a single doping type in the source, channel, and drain has been proposed[2, 12,13,14,15]. Metallic channels may be the promising solution for overcoming the random dopants fluctuations in JLTs. Unlike the semiconductor-based JLTs, the source, channel, and drain in metallic channel transistors are composed of metallic ultrathin bodies. The high electron concentration in metallic channels allows the channel free of the heavy doping as required in JLTs, and so the issue of random dopants fluctuations can be avoided. The screening effect leads to the difficulty in modulating the electron concentration by the electric field, giving rise to the poor gate control as the dimension of metallic channels is greater than the screening length. The atomic engineering of dopant incorporation might induce the modification of the band structure to get new electrical properties of nanoscale thin films
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