Near-infrared absorption and semimetal-semiconductor transition in 2 nm ErAs nanoparticles embedded in GaAs and AlAs

Journal ArticleWe report strong near-infrared absorption peaks in epitaxial films of GaAs and AlAs containing approximately 0.5-5% of the semimetal ErAs. The energy of the resonant absorption peak can be changed from 0.62 to 1.0 eV (2.2-1.4 μm) by variation of the ErAs volume fraction and the substrate temperature. We interpret the infrared absorption in terms of transitions across an energy gap caused by a confinement-induced semimetal-semiconductor transition. An effective mass model relates the changes in nanoparticle diameter observed in transmission electron microscopy to the energy gap

Probing energy barriers and quantum confined states of buried semiconductor heterostructures with ballistic carrier injection: An experimental study

A three-terminal spectroscopy that probes both subsurface energy barriers and interband optical transitions in a semiconductor heterostructure is demonstrated. A metal-base transistor with a unipolar p-type semiconductor collector embedding InAs/GaAs quantum dots (QDs) is studied. Using minority/majority carrier injection, ballistic electron emission spectroscopy and its related hot-carrier scattering spectroscopy measures barrier heights of a buried AlxGa1-xAs layer in conduction band and valence band respectively, the band gap of Al0.4Ga0.6As is therefore determined as 2.037 +/- 0.009 eV at 9 K. Under forward collector bias, interband electroluminescence is induced by the injection of minority carriers with sub-bandgap kinetic energies. Three emission peaks from InAs QDs, InAs wetting layer, and GaAs are observed in concert with minority carrier injection.Comment: 11 pages, 4 figures, submitted to Physical Review

Scattering-Assisted Tunneling: Energy Dependence, Magnetic Field Dependence, and Use as an External Probe of Two-Dimensional Transport

For more than three decades, research on tunneling through planar barriers has focused principally on processes that conserve momentum parallel to the barrier. Here we investigate transport in which scattering destroys lateral momentum conservation and greatly enhances the tunneling probability. We have measured its energy dependence using capacitance spectroscopy, and we show that for electrons confined in a quantum well, the scattering enhancement can be quenched in an applied magnetic field, enabling this mechanism to function as an external probe of the origin of the quantum Hall effect.Engineering and Applied Science

Scattering-assisted tunneling: energy dependence, magnetic field dependence, and use as an external probe of two-dimensional transport

For more than three decades, research on tunneling through planar barriers has focused principally on processes that conserve momentum parallel to the barrier. Here we investigate transport in which scattering destroys lateral momentum conservation and greatly enhances the tunneling probability. We have measured its energy dependence using capacitance spectroscopy, and we show that for electrons confined in a quantum well, the scattering enhancement can be quenched in an applied magnetic field, enabling this mechanism to function as an external probe of the origin of the quantum Hall effect

Influence of Mn dopants on InAs/GaAs quantum dot electronic states

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98664/1/ApplPhysLett_98_141907.pd

Interface atomic structure of epitaxial ErAs layers on (001) In0.53Ga0.47As and GaAs

High-angle annular dark-field (HAADF) imaging in scanning transmission electron microscopy was used to determine the atomic structure of interfaces between epitaxial ErAs layers with the cubic rock salt structure and In0.53Ga0.47As and GaAs, respectively. All layers were grown by molecular beam epitaxy. We show that the interfacial atomic arrangement corresponds to the so-called chain model, in which the zinc blende semiconductor is terminated with a Ga layer. Image analysis was used to quantify the expansion between the first ErAs plane and the terminating Ga plane. In the HAADF images, a high intensity transfer from the heavy Er columns into the background was observed in the ErAs layer, whereas the background in In0.53Ga0.47As was of much lower intensity

Cross-plane Seebeck coefficient of ErAs:InGaAs∕InGaAlAs superlattices

We characterize cross-plane and in-plane Seebeck coefficients for ErAs:InGaAs/InGaAlAs superlattices with different carrier concentrations using test patterns integrated with microheaters. The microheater creates a local temperature difference, and the cross-plane Seebeck coefficients of the superlattices are determined by a combination of experimental measurements and finite element simulations. The cross-plane Seebeck coefficients are compared to the in-plane Seebeck coefficients and a significant increase in the cross-plane Seebeck coefficient over the in-plane Seebeck coefficient is observed. Differences between cross-plane and in-plane Seebeck coefficients decrease as the carrier concentration increases, which is indicative of heterostructure thermionic emission in the cross-plane direction. (c) 2007 American Institute of Physics

Cross-plane Seebeck coefficient of ErAs : InGaAs/InGaAlAs superlattices

Abstract We characterize cross-plane and in-plane Seebeck coefficients for ErAs:InGaAs/InGaAlAs superlattices with different carrier concentrations using test patterns integrated with microheaters. The microheater creates a local temperature difference, and the cross-plane Seebeck coefficients of the superlattices are determined by a combination of experimental measurements and finite element simulations. The cross-plane Seebeck coefficients are compared to the in-plane Seebeck coefficients and a significant increase in the cross-plane Seebeck coefficient over the in-plane Seebeck coefficient is observed. Differences between cross-plane and inplane Seebeck coefficients decrease as the carrier concentration increases, which is indicative of heterostructure thermionic emission in the cross-plane direction. We characterize cross-plane and in-plane Seebeck coefficients for ErAs: InGaAs/ InGaAlAs superlattices with different carrier concentrations using test patterns integrated with microheaters. The microheater creates a local temperature difference, and the cross-plane Seebeck coefficients of the superlattices are determined by a combination of experimental measurements and finite element simulations. The cross-plane Seebeck coefficients are compared to the in-plane Seebeck coefficients and a significant increase in the cross-plane Seebeck coefficient over the in-plane Seebeck coefficient is observed. Differences between cross-plane and in-plane Seebeck coefficients decrease as the carrier concentration increases, which is indicative of heterostructure thermionic emission in the cross-plane direction. Cross-plane Seebeck coefficient of ErAs: InGaAs/ InGaAlAs superlattice