278 research outputs found
Monte Carlo calculations for metal-semiconductor hot-electron injection via tunnel-junction emission
We present a detailed description of a scheme to calculate the injection current for metal-semiconductor systems using tunnel-junction electron emission. We employ a Monte Carlo framework for integrating over initial free-electron states in a metallic emitter and use interfacial scattering at the metal-semiconductor interface as an independent parameter. These results have implications for modeling metal-base transistors and ballistic electron emission microscopy and spectroscopy
BEEM imaging and spectroscopy of buried structures in semiconductors
Ballistic Electron Emission Microscopy (BEEM) has been shown to be a powerful tool for nanometer-scale characterization of the spatial and electronic properties of semiconductor structures. In this article, we will discuss general aspects of BEEM experiment and theory in true ballistic and quasi-ballistic hot carrier transport. We will review the current state and recent progress in the use of the BEEM imaging and spectroscopy to study metal-semiconductor and metal-insulator-semiconductor interfaces, buried semiconductor heterojunctions and novel quantum objects. Various theoretical BEEM models are discussed, and their ability to describe BEEM experiments is examined. Special attention is drawn to the role of the electron scattering in the metal base layer, at the metal-semiconductor interface and in the semiconductor heterostructure on BEEM spectra
Radiation induced zero-resistance states in GaAs/AlGaAs heterostructures: Voltage-current characteristics and intensity dependence at the resistance minima
High mobility two-dimensional electron systems exhibit vanishing resistance
over broad magnetic field intervals upon excitation with microwaves, with a
characteristic reduction of the resistance with increasing radiation intensity
at the resistance minima. Here, we report experimental results examining the
voltage - current characteristics, and the resistance at the minima vs. the
microwave power. The findings indicate that a non-linear V-I curve in the
absence of microwave excitation becomes linearized under irradiation, unlike
expectations, and they suggest a similarity between the roles of the radiation
intensity and the inverse temperature.Comment: 3 color figures; publishe
Ballistic electron microscopy and spectroscopy of metal and semiconductor nanostructures
Ballistic electron emission microscopy (BEEM) and its spectroscopy utilize ballistic transport of hot carriers as a versatile tool to characterize nanometer-scale structural and electronic properties of metallic and semiconducting materials and their interfaces. In this review, recent progress in experimental and theoretical aspects of the BEEM technique are covered. Emphasis is drawn to the development of BEEM in several emerging fields, including spin-sensitive hot-carrier transport through ferromagnetic thin films and multilayers, hot-electron spectroscopy and imaging of organic thin films and molecules, and hot-electron induced electroluminescence in semiconductor heterostructures. A brief discussion on BEEM of cross-sectional semiconductor heterostructures and advanced insulator films is also included
Comment on anomalous dispersion and scattering rates for multiphonon spontaneous decay in He II
We report on new measurements of the spontaneous decay threshold energy Ec for high-frequency phonon propagation in He II at saturated vapor pressure at T=0.1 K. Superconducting tin tunnel generators and aluminum tunnel detectors were used in this study. The measurements show that the mean free path becomes much larger than the propagation length of 1.1 mm for a value of Ec =9.8±0.15 K. This agrees with the value originally reported (Ec =9.5±0.4 K) by Dynes and Narayanamurti using aluminum tunnel generators, but is shown to correspond to the point where the phase velocity equals the sound velocity, when the phonons become stable, as first proposed by Pitayevski and Levinson. Evidence for n-phonon decay at energies lower than Ec is presented for n≥2 with a short mean free path (<0.3 mm) at the two-phonon decay energy. The measured values of the dispersion parameters are shown to agree closely with the spline fit to neutron data due to donnelly, donnelly, and Hills
Observations of conduction-band structure of 4H- and 6H-SiC
Ballistic electron-emission spectroscopy (BEES) and photoluminescence are used to study conduction-band structure related transport properties of the 4H and 6H polytypes of SiC. A secondary energy threshold at 2.7 eV is observed in the BEES spectrum of 4H-SiC, in good agreement with a value of 2.8 eV deduced from reported ab initio calculations. The results from 6H-SiC, are suggested to be influenced by transport properties of other polytype inclusions, also supported by band-edge transitions evident in 6H-SiC photoluminescence spectra
Initialization of a nuclear spin system over the quantum Hall regime for quantum information processing
The application of the quantum mechanical properties of physical systems to
realize novel computational schemes and innovative device functions have been
topics of recent interest. Proposals for associated devices are to be found in
diverse branches of physics. Here, we are concerned with the experimental
realization of some elements needed for quantum information processing using
nuclear spin immersed in a confined electronic system in the quantum Hall
regime. Thus, we follow a spin-handling approach that (a) uses the Overhauser
effect in the quantum Hall regime to realize a large nuclear polarization at
relatively high temperatures, (b) detects the nuclear spin state by measuring
the influence of the associated magnetic field on Electron Spin Resonance, and
(c) seeks to apply the electronic spin exciton as the spin transfer mechanism.
Some measurements examining the viability of this approach are shown, and the
utility of the approach for initializing a nuclear spin system at a relatively
high temperature is pointed ou
Imaging subsurface reflection phase with quantized electrons
Lead quantum wells (QW) epitaxially grown on annealed Pb/Si(111) interface form a model system for the study of interactions between quantized electrons and adiabatically modulated boundaries. Tunnel spectra of this system reveal a previously unknown adiabatic shift of QW resonances due to lateral variations of the electronic reflection phase at the buried interface. With this effect, lateral distribution of the subsurface reflection phase can be probed, using scanning tunneling microscopy
- …