Leo Esaki

Bio: Leo Esaki is an academic researcher from United States Department of the Army. The author has contributed to research in topics: Superlattice & Semiconductor. The author has an hindex of 15, co-authored 21 publications receiving 2910 citations.

Resonant tunneling in semiconductor double barriers

Abstract: Resonant tunneling of electrons has been observed in double‐barrier structures having a thin GaAs sandwiched between two GaAlas barriers. The resonance manifests itself as peaks or humps in the tunneling current at voltages near the quasistationary states of the potential well. The structures have been fabricated by molecular beam epitaxy which produces extremely smooth films and interfaces.

A new semiconductor superlattice

Abstract: We treat theoretically, through the use of Bloch functions, a new semiconductor superlattice where the interaction of the conduction band in one host material with the valence band of the other host material plays an important role. The result indicates that this superlattice offers new intriguing features, realizable with the In1−xGaxAs‐GaSb1−y Asy system. In addition, the tunneling probability is calculated across a barrier involving this system.

Molecular‐beam epitaxy (MBE) of In1−xGaxAs and GaSb1−yAsy

Abstract: Films of In1−xGaxAs and GaSb1−yAsy over the entire composition ranges have been grown on (100) GaAs, InAs, and GaSb substrates by MBE. In situ observations by high‐energy electron diffraction have revealed a variety of surface reconstructions and correlated the growth process with the lattice mismatch. The compositions are governed by the relative rates of In and Ga in In1−xGaxAs, but primarily by that of Sb in GaSb1−yAsy because of its dominant incorporation over As. In these alloys, Sn is found to be a donor throughout In1−xGaxAs but an amphoteric impurity in GaSb1−yAsy.

In1−xGaxAs‐GaSb1−yAsy heterojunctions by molecular beam epitaxy

Abstract: Smooth films of n‐In1−xGaxAs and p‐GaSb1−yAsy were grown by molecular beam epitaxy. As a function of the compositions, x and y, the lattice constants vary linearly while the energy gaps show a downward bowing. Abrupt heterojunctions made of these alloys with close lattice matching exhibit a series of current‐voltage characteristics which change from rectifying to Ohmic as x and y are reduced. The relative location of the band‐edge energies of the two semiconductors at the interface is shown to account for the unusual characteristics observed experimentally.

Molecular beam epitaxy of alternating metal-semiconductor films

Abstract: Alternately repeated layers of metal epitaxy on semiconductor substrates and semiconductor epitaxy on metal substrates are grown in an ultra-high vacuum evaporation system by first depositing the metal film on the clean surface of the semiconductor substrate over the temperature range between room temperature and 400 DEG C; and then depositing the semiconductor film on the clean surface of the metal over the temperature range between 500 DEG C and 600 DEG C.

Electron mobilities in modulation‐doped semiconductor heterojunction superlattices

Abstract: GaAs‐AlxGa1−xAs superlattice structures in which electron mobilities exceed those of otherwise equivalent epitaxial GaAs as well as the Brooks‐Herring predictions near room temperature and at very low temperatures are reported. This new behavior is achieved via a modulation‐doping technique that spatially separates conduction electrons and their parent donor impurity atoms, thereby reducing the influence of ionized and neutral impurity scattering on the electron motion.

Transport in Nanostructures

Abstract: 1. Introduction 2. Quantum confined systems 3. Transmission in nanostructures 4. Quantum dots and single electron phenomena 5. Interference in diffusive transport 6. Temperature decay of fluctuations 7. Non-equilibrium transport and nanodevices.

Carrier transport in transparent oxide semiconductor with intrinsic structural randomness probed using single-crystalline InGaO3(ZnO)5 films

Abstract: We have investigated carrier transport in a crystalline oxide semiconductor InGaO3(ZnO)5 using single-crystalline thin films. When carrier concentration is less than 2×1018cm−3, logarithm of electrical conductivity decreases in proportion to T−1∕4 and room-temperature Hall mobility was as low as ∼1cm2(Vs)−1. When carrier concentration was increased to 4×1018cm−3, the conduction mechanism changed to degenerate conduction and room-temperature Hall mobility was steeply increased to >10cm2(Vs)−1, showing metal–insulator transition behavior. These results are explained by percolation conduction over distribution of potential barriers formed around conduction band edge. The potential distribution is a consequence of potential modulation originating from random distribution of Ga3+ and Zn2+ ions in the crystal structure of InGaO3(ZnO)5.

Electronic structure of quantum dots

Abstract: The properties of quasi-two-dimensional semiconductor quantum dots are reviewed. Experimental techniques for measuring the electronic shell structure and the effect of magnetic fields are briefly described. The electronic structure is analyzed in terms of simple single-particle models, density-functional theory, and "exact" diagonalization methods. The spontaneous magnetization due to Hund's rule, spin-density wave states, and electron localization are addressed. As a function of the magnetic field, the electronic structure goes through several phases with qualitatively different properties. The formation of the so-called maximum-density droplet and its edge reconstruction is discussed, and the regime of strong magnetic fields in finite dot is examined. In addition, quasi-one-dimensional rings, deformed dots, and dot molecules are considered. (Less)