Papers by Keyword: Quantum Transport

Abstract: Starting from a three-dimensional transport model in the Landauer-Buttiker formalism we derive a scale-invariant expression for the drain current in a nano-transistor. Apart from dimensionless external parameters representing temperature, gate-, and drain voltage the normalized drain current depends on two dimensionless transistor parameters which are the characteristic length l and -width w of the electron channel. The latter quantities are the physical length and -width of the channel in units of the scaling length  = ~(2mF )􀀀1=2. Here F is the Fermi energy in the source contact and m is the eective mass in the electron channel. In the limit of wide transistors and low temperatures we evaluate the scale-invariant ID􀀀VD characteristics as a function of the characteristic length. In the strong barrier regime, i. e. for l & 20 long-channel behavior is found. At weaker barriers source-drain tunneling leads to increasingly signicant deviations from the long-channel behavior. We compare with experimental results.

Abstract: We develop a theory for scaling properties of quantum transport in nano-field effect transistors. Our starting point is a one-dimensional effective expression for the drain current in the Landauer-Büttiker formalism. Assuming a relatively simple total potential acting on the electrons the effective theory can be reduced to a scale-invariant form yielding a set of dimensionless control parameters. Among these control parameters are the characteristic length l and -width w of the electron channel which are its physical length and -width in units of the scaling length . Here is the Fermi energy in the source contact and is the effective mass in the electron channel. In the limit of wide transistors and low temperatures we evaluate the scale-invariant i-v characteristics as a function of the characteristic length. In the strong barrier regime, i. e. for long-channel behavior is found. At weaker barriers source-drain tunneling leads to increasingly significant deviations from the long-channel behavior.

Abstract: This study presents ionized impurity impacts on silicon nanowire MOS transistors. We calculate the current characteristics with a self-consistent three-dimensional (3D) Green’s function approach and show the effects of both acceptor and donor impurities on the physical electron properties. In particular, we emphasize that the presence of a donor induces different transport phenomena according to the applied gate bias. Our results show that the influence of a single impurity strongly depends on its position and induces high transistor performance variability with current modifications from 50% to two orders of magnitude.

Abstract: The device characteristics of the nanoscale metal/insulator tunnel transistor are investigated by solving the ballistic quantum transport equation in the device. The device performance in terms of the transfer characteristics, the drain output, and the threshold voltage change is assessed as the channel length is gradually reduced down to a few nanometer. We have found that the device characteristics remain almost the same if the channel length is reduced to around 10 nanometer, but below it, the device performance becomes drastically degraded. Effects of other device parameters such as the channel depth, tunnel barrier height, and the gate dielectric constant are also discussed.