Effective mass (solid-state physics)

About: Effective mass (solid-state physics) is a research topic. Over the lifetime, 12539 publications have been published within this topic receiving 295485 citations.

Raman scattering from anisotropic LO‐phonon–plasmon–coupled mode in n‐type 4H– and 6H–SiC

Abstract: LO‐phonon–plasmon–coupled modes in n‐type 4H– and 6H–SiC single crystals with free‐carrier concentrations of 1016–1018 cm−3 have been measured by Raman scattering at room temperature. The axial‐type mode for which plasma oscillation and atomic displacement are parallel to the c axis, and the planar‐type mode for which these oscillations lie in the c plane, have been individually observed. From a line‐shape analysis of the observed spectra, the plasmon frequency, carrier damping, and phonon damping have been deduced. These quantities have large differences between the axial‐ and planar‐type mode in 6H–SiC, indicating its large crystal anisotropy. On the contrary, 4H–SiC shows small anisotropy. The longitudinal and transverse effective mass components of the electron have been determined from the plasmon frequency using carrier densities derived from Hall measurements. The deduced values are m∥=1.4m0 and m⊥=0.35m0 for 6H–SiC, and m∥=0.48m0 and m⊥=0.30m0 for 4H–SiC. The carrier mobility obtained from the ana...

Modeling the contribution of quantum confinement to luminescence from silicon nanoclusters

Abstract: We present a model for the luminescence spectrum of silicon nanoclusters. We propose that the major contribution to luminescence is from radiative recombination of confined excitons (quantum confinement). Utilizing the effective mass approximation we consider the variation in oscillator strength with cluster size and the associated change in the number of available free carriers. By varying both the mean cluster size and size distribution of silicon nanoclusters, the luminescence spectra are modeled to a good fit. We compare our model with experimental photoluminescence and electroluminescence data from this group and from others.

Bandstructure Effects in Silicon Nanowire Electron Transport

Abstract: Bandstructure effects in the electronic transport of strongly quantized silicon nanowire field-effect-transistors (FET) in various transport orientations are examined. A 10-band sp3d5s* semiempirical atomistic tight-binding model coupled to a self-consistent Poisson solver is used for the dispersion calculation. A semi-classical, ballistic FET model is used to evaluate the current-voltage characteristics. It is found that the total gate capacitance is degraded from the oxide capacitance value by 30% for wires in all the considered transport orientations ([100], [110], [111]). Different wire directions primarily influence the carrier velocities, which mainly determine the relative performance differences, while the total charge difference is weakly affected. The velocities depend on the effective mass and degeneracy of the dispersions. The [110] and secondly the [100] oriented 3 nm thick nanowires examined, indicate the best ON-current performance compared to [111] wires. The dispersion features are strong functions of quantization. Effects such as valley splitting can lift the degeneracies particularly for wires with cross section sides below 3 nm. The effective masses also change significantly with quantization, and change differently for different transport orientations. For the cases of [100] and [111] wires the masses increase with quantization, however, in the [110] case, the mass decreases. The mass variations can be explained from the non-parabolicities and anisotropies that reside in the first Brillouin zone of silicon.

A three-dimensional simulation of quantum transport in silicon nanowire transistor in the presence of electron-phonon interactions

Abstract: Based on the nonequilibrium Green’s function formalism, we have developed a three-dimensional (3D) simulation framework capable of handling electronic transport in nanoscale silicon devices within the effective mass and Hartree approximations. Using the deformation potential theory and the self-consistent Born approximation, we obtain the spatially local self-energy functions for the intravalley and intervalley phonon scattering mechanisms. To make the 3D simulation practicable, we reduce the computational complexity by using the mode space approach suitable for the device whose cross section is relatively uniform along the transport direction. We also obtain the expression for the phonon-limited low field mobility in the long channel limit from the linear response theory. As an application, we study the quantum transport of the silicon nanowire transistor whose channel length is 15nm in the ballistic limit and in the presence of the electron-phonon interactions. We can observe various effects of the elec...

Electron tunneling through alkanedithiol self-assembled monolayers in large-area molecular junctions

Abstract: The electrical transport through self-assembled monolayers of alkanedithiols was studied in large-area molecular junctions and described by the Simmons model [Simmons JG (1963) J Appl Phys 34:1793–1803 and 2581–2590] for tunneling through a practical barrier, i.e., a rectangular barrier with the image potential included. The strength of the image potential depends on the value of the dielectric constant. A value of 2.1 was determined from impedance measurements. The large and well defined areas of these molecular junctions allow for a simultaneous study of the capacitance and the tunneling current under operational conditions. Electrical transport for octanedithiol through tetradecanedithiol self-assembled monolayers up to 1 V can simultaneously be described by a single effective mass and a barrier height. There is no need for additional fit constants. The barrier heights are in the order of 4–5 eV and vary systematically with the length of the molecules. Irrespective of the length of the molecules, an effective mass of 0.28 was determined, which is in excellent agreement with theoretical predictions.