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The authors report on photomixing terahertz sources that overcome the transit time versus RC-time trade-off and allow for independent optimization of both of them, using a n-i-p-n-i-p superlattice. Furthermore, they take advantage of ballistic transport for reduced transit times. Apart from more favorable material parameters, In(Al)GaAs photomixers benefit from the advanced telecommunication laser technology around 1.55 μm as compared to GaAs. In such devices, a terahertz-power output of 1 μW has been achieved at 0.4 THz at a photocurrent of 3.8 mA. A comparison between corresponding GaAs- and InGaAs-based n-i-p-n-i-p photomixers reveals an improvement of performance by at least an order of magnitude for the latter one. [ABSTRACT FROM AUTHOR]

Ballistic thermal conductance in a three-dimensional quantum wire with a stub structure is presented under both stress-free and hard wall boundary conditions at low temperatures. A comparative analysis for two-dimensional and three-dimensional models is made. The results show that when stress-free boundary conditions are applied, the universal quantum thermal conductance can be observed regardless of the geometry details in the limit T→0, and the behavior of the thermal conductance is qualitatively similar to that calculated by two-dimensional model. However, when hard wall boundary conditions are applied, the thermal conductance displays different behaviors in both two-dimensional and three-dimensional models. [ABSTRACT FROM AUTHOR]

Implementation of the universal Toffoli gate in a ballistic nanowire based structure has been discussed in this letter. The gate operation is dependent on spin manipulation in nanowires. Spin injection into the Toffoli gate can be done using a similar intertwined ballistic nanowire based setup. The device inputs are digital voltages and the output is obtained by spin readout. Realization of NAND gate, fan out, and half-adder based on the Toffoli gate has also been presented. [ABSTRACT FROM AUTHOR]

The authors investigated the current-voltage characteristics of a 100 nm AlGaAs/InGaAs pseudomorphic high electron mobility transistor as a function of temperature. The drain current in the linear region showed a dramatic increase when the temperature was lowered below a critical value (TB) and the drain voltage is increased. A quantitative analysis based on self-consistent Schrödinger-Poisson and simple electrostatic band potential profile calculations was performed to model the transmission coefficient. The modeled results are consistent with the measured data, confirming that the main transport mechanism switches from a classical drift-diffusion transport into a quasiballistic transport when decreasing temperature below TB and increasing drain voltage. [ABSTRACT FROM AUTHOR]

The authors report an atomistic study of the ballistic current through silicon nanowire metal-oxide-semiconductor transistors. A self-consistent quantum ballistic transport model is used to calculate the current in gate-all-around nanowire transistors, taking into account the full-band structure of the quantum wire with a sp3 tight-binding approach. The authors demonstrate the occurrence of an optimal wire cross section for which the on-state/off-state current ratio is maximum, a result which cannot be obtained in a standard bulk effective mass description. [ABSTRACT FROM AUTHOR]

The authors discuss a generalized transport model including memory and nonlocal effects, which aims to describe the transition of heat transport from the diffusive regime to the ballistic regime. By using an effective thermal conductivity depending on the Knudsen number, they describe in a single equation the behavior of conductivity in terms of the system size and a reduction in the limit flux through nanoscale devices. [ABSTRACT FROM AUTHOR]

The authors show that both real and imaginary parts of the admittance of short (ballistic or quasiballistic) semiconductor structures are oscillatory functions of the frequency with the period determined by the inverse electron transit time with the Fermi velocity. This oscillatory dependence is caused by the phase difference between the electrons injected from the opposite contacts. [ABSTRACT FROM AUTHOR]

The authors have fabricated and studied a ballistic one-dimensional p-type quantum wire using an undoped AlGaAs/GaAs heterostructure. The absence of modulation doping eliminates remote ionized impurity scattering and allows high mobilities to be achieved over a wide range of hole densities and, in particular, at very low densities where carrier-carrier interactions are strongest. The device exhibits clear quantized conductance plateaus with highly stable gate characteristics. These devices provide opportunities for studying spin-orbit coupling and interaction effects in mesoscopic hole systems in the strong interaction regime where rs>10. [ABSTRACT FROM AUTHOR]

We have studied ballistic transport in a one-dimensional (1D) channel formed using surface gate techniques on a back-gated, high-mobility, bilayer two-dimensional hole system. At millikelvin temperatures, robust conductance quantization is observed in the quantum wire formed in the top layer of the bilayer system, without the gate instabilities that have hampered previous studies of 1D hole systems. Using source drain bias spectroscopy, we have measured the 1D subband spacings, which are 5–10 times smaller than in comparable GaAs electron systems, but 2–3 times larger than in previous studies of 1D holes. We also report the first observation of the anomalous conductance plateau at G=0.7×2e2/h in a 1D hole system. [ABSTRACT FROM AUTHOR]

In this letter, we explore the band structure effects on the performance of ballistic silicon nanowire transistors (SNWTs). The energy dispersion relations for silicon nanowires are evaluated with an sp3d5s* tight binding model. Based on the calculated dispersion relations, the ballistic currents for both n-type and p-type SNWTs are evaluated by using a seminumerical ballistic model. For large diameter nanowires, we find that the ballistic p-SNWT delivers half the ON-current of a ballistic n-SNWT. For small diameters, however, the ON-current of the p-type SNWT approaches that of its n-type counterpart. Finally, the carrier injection velocity for SNWTs is compared with those for planar metal-oxide-semiconductor field-effect transistors, clearly demonstrating the impact of quantum confinement on the performance limits of SNWTs. [ABSTRACT FROM AUTHOR]

We study ballistic electron transport through a finite chain of quantum circular rings in the presence of spin–orbit interaction of strength α. For a single ring, the transmission and reflection coefficients are obtained analytically and from them the conductance for a chain of rings as a function of α and of the wave vector k of the incident electron. We show that due to destructive spin interferences, the chain can be totally opaque for certain ranges of k, the width of which depends on the value of α. A periodic modulation of the strength α or of the ring radius widens the gaps considerably and produces a nearly binary conductance output. [ABSTRACT FROM AUTHOR]

We discuss an implementation of ballistic electron emission microscopy (BEEM), in which the metallic or metal–insulator “stack” of interest is formed directly over an avalanche p–n diode. This allows nanometer-resolution studies of hot-electron transport through technologically important device stacks with up to single electron sensitivity and >10 kHz measurement bandwidth when the avalanche diode is cooled to <200 K. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

This letter revises the interpretation of recent experiments showing quantized conductance on GaAs/GaAlAs constrictions or point contacts in terms of coherent ballistic and sequential transport. Our calculations show by using a first iterative self-consistent procedure that the experimental data can also be reconciled with sequential transport. The mean free path concept in the constriction is discussed in comparison with that of the reservoirs. We conclude that, for the higher modes, the former is much smaller than the latter, implying that in the constriction the transport may be sequential. [ABSTRACT FROM AUTHOR]

We introduce three basic components for the manipulation of quasi-classical ballistic electrons in very high mobility two-dimensional electron systems and evaluate their effectiveness using the transverse electron focusing technique. We present an electron absorber or electron randomizer, demonstrate electron focusing in an area of tunable electron density, and present a simplified version of an injector/collector for ballistic carriers in two dimensions. [ABSTRACT FROM AUTHOR]

Recent experimental studies of ballistic electron transport have pushed the transit time well into the subpicosecond dynamical regime. By applying the quantum dynamical theory to study ultrafast transient transport, we report results that are dramatically different from those predicted by the classical Boltzmann theory. [ABSTRACT FROM AUTHOR]

Examines the switching properties of a T-shaped quantum waveguide. Transient analysis of ballistic transport; Spectral contributions in the terahertz range; Accounts on the pronounced mixing effects; Sharing of electron wave function between the bound and metastables states of the initial and final eigenspectra.

Indicates the role of high voltage electroforming in the one-dimensional conductance quantization (1DCQ). Formation of quantum point contacts during devices deposition or electron injection; Details on the result in relation to ballistic point contact; Observation on a 1DCQ room temperature; Manifestation on the onset of conductance quantization.

The article reviews website regarding physics education on real-world small arms ballistics and U.S. Army Major General of Ordinance Julian Hatcher's notebook including www.en.wikipedia.org/wiki/Julian_Hatcher, www.tinyurl.com/WS-HatcherVideoReview, and www.books.google.de/books?isbn=0811749177.

The article presents a water drop pulser apparatus that generates a parabolic trajectory of water droplets. The apparatus, along with a stroboscope, allows students to observe the stop-action projectile motion from any vantage point. The apparatus consists of a standard low-voltage doorbell that is wrapped with latex tubing in such a way as to be vibrated by the bell clapper. Water is expelled through an eyedropper nozzle by the vibration of the clapper. A guide to construct the apparatus is presented.

A dual parameter representation of the barrier height and transmission extracted from ballistic electron emission spectroscopy spectra is presented and evaluated with respect to the noise present in the spectra and the conditions used for data fitting. Simulated dual parameter distributions incorporating only Gaussian (white) noise are compared to experimental dual parameter distributions for two interfaces, namely, Au/n-Si and Au/pentacene/n-Si. The authors find that for both measurements, noise and data fitting conditions can have significant influence on the distributions. Once these contributions are accounted for, such dual parameter representations provide statistical information related to the interfacial homogeneity of devices. [ABSTRACT FROM AUTHOR]