Article

# Ballistic FET modeling using QDAME: quantum device analysis by modal evaluation

T. J. Watson Res. Center, IBM Corp., Yorktown Heights, NY, USA

IEEE Transactions on Nanotechnology (Impact Factor: 1.8). 01/2003; DOI: 10.1109/TNANO.2002.807388 Source: IEEE Xplore

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**ABSTRACT:**Confined structures presumably offer enhanced performance of thermoelectric devices. 1) Interfaces and boundaries create scattering sites for phonons, which reduces the thermal conductivity. 2) Reduced dimensionality increases the local density of states near the Fermi level, which increases the Seebeck coefficient. From these two phenomena, the net effect should be an increase in ZT, the performance parameter used to evaluate different materials and structures. These effects have been measured and modeled, but none of the models attempts to quantify the electron-phonon coupled effects particularly in the regime where quantum and scattering influences are found. Using the non-equilibrium Green's function (NEGF) approach, quantum wells composed of Si and Ge are studied and the important physics isolated. Results show a competing effect between the decrease in the electrical conductivity due to scattering with the increase in electrical conductivity with doping, leading to 77% decrease in the value of the power factor for the case of electron-optical phonon scattering. - [Show abstract] [Hide abstract]

**ABSTRACT:**A nonparabolic band model has been implemented for a one-dimensional electron gas, using a modified Schrödinger equation which takes into account size quantization in the transverse cross section of a silicon quantum wire. The quantized states and the corresponding one-dimensional density of states have been analyzed when the nonparabolicity is present, to quantify the importance of the effect of realistic bands at higher energies.Journal of Applied Physics 08/2005; · 2.21 Impact Factor - [Show abstract] [Hide abstract]

**ABSTRACT:**In this paper, we apply a two-dimensional quantum mechanical simulation scheme to study the effect of channel access geometries on device performance. This simulation scheme solves the non-equilibrium Green's function equations self-consistently with Poisson's equation and treats the effect of scattering using a simple approximation inspired by Büttiker. It is based on an expansion of the device Hamiltonian in coupled mode-space. Simulation results are used to highlight quan-tum effects and discuss the importance of scattering when examining the transport properties of nanoscale transistors with differing channel access geometries. Additionally, an efficient domain decomposition scheme for evaluating the performance of nanoscale transistors is also presented. This paper highlights the importance of scattering in understanding the performance of transistors with different channel access geometries.Journal of Applied Physics 01/2004; 95. · 2.21 Impact Factor

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