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Full-Text Articles in Nanoscience and Nanotechnology
Rough Interfaces In Thz Quantum Cascade Lasers, Tillmann Kubis, Gerhard Klimeck
Rough Interfaces In Thz Quantum Cascade Lasers, Tillmann Kubis, Gerhard Klimeck
Gerhard Klimeck
The impact of interface roughness scattering on the device performance of state-of-the-art THz quantum cascade lasers is theoretically analyzed using the non-equilibrium Green’s function formalism. It is shown that for a particular direct transition QCL design style rough interfaces hardly change the electronic energy spectrum, but dramatically reduce the occupation inversion and the optical gain. A spatial separation leading to a diagonal transition laser, leads in contrast to a limited sensitivity to interface roughness. Diagonal transition QCL designs result in a better device performance and an improved reliability with respect to interface roughness induced by growth quality variations.
A Comprehensive Atomistic Analysis Of Bandstructure Velocities In Si Nanowires, Neophytos Neophytou, Hans Kosina, Gerhard Klimeck
A Comprehensive Atomistic Analysis Of Bandstructure Velocities In Si Nanowires, Neophytos Neophytou, Hans Kosina, Gerhard Klimeck
Gerhard Klimeck
A 20 band sp3d5s* spin-orbit-coupled, semi-empirical, atomistic tight-binding (TB) model is used with a semi-classical, ballistic transport model, to theoretically examine the bandstructure carrier velocity under non-degenerate conditions in silicon nanowire (NW) transistors. Infinitely long, uniform, cylindrical and rectangular NWs, of cross sectional diameters/sides ranging from 3nm to 12nm are considered. For a comprehensive analysis, n-type and p-type NWs in [100], [110] and [111] transport orientations are examined. The carrier velocities of p-type [110] and [111] NWs increase by a factor of ~2X as the NWs’ diameter scales from D=12nm down to D=3nm. The velocity of n-type [110] NWs also …