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.

Electron mobilities in modulation‐doped semiconductor heterojunction superlattices

We present detailed experimental studies and modeling of the nonlinear absorption and refraction of GaAs/AlGaAs multiple quantum well structures (MQWS) in the small signal regime. Nonlinear absorption and degenerate four-wave mixing in the vicinity of the room temperature exciton resonances are observed and analyzed. Spectra of the real and imaginary parts of the nonlinear cross section as a function of wavelength are obtained, and these are in excellent agreement with experimental data. A simple model for excitonic absorption saturation is proposed; it accounts qualitatively for the very low saturation intensities of room temperature excitons in MQWS.

Room temperature excitonic nonlinear absorption and refraction in GaAs/AlGaAs multiple quantum well structures

Integrated optics and new wave phenomena in optical waveguides

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.

A new semiconductor superlattice

The broad spectrum of electronic and optical properties exhibited by oxides offers tremendous opportunities for microelectronic devices, especially when a combination of properties in a single device is desired Here we describe the use of reactive molecular-beam epitaxy and pulsed-laser deposition to synthesize functional oxides, including ferroelectrics, ferromagnets, and materials that are both at the same time Owing to the dependence of properties on direction, it is often optimal to grow functional oxides in particular directions to maximize their properties for a specific application But these thin film techniques offer more than orientation control; customization of the film structure down to the atomic-layer level is possible Numerous examples of the controlled epitaxial growth of oxides with perovskite and perovskite-related structures, including superlattices and metastable phases, are shown In addition to integrating functional oxides with conventional semiconductors, standard semiconductor practices involving epitaxial strain, confined thickness, and modulation doping can also be applied to oxide thin films Results of fundamental scientific importance as well as results revealing the tremendous potential of utilizing functional oxide thin films to create devices with enhanced performance are described

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A Thin Film Approach to Engineering Functionality into Oxides

Epitaxial structures grown by alternate monolayer depositions of GaAs and AlAs are reported. As many as 104 alternate (100) layers of GaAs and AlAs as thin as 1.0±0.1 and 1.0±0.1 monolayers, respectively, were deposited by sequential molecular beam epitaxial growth on a (100)GaAs substrate. Transmission electron microscopy showed the resultant films to be perfectly epitaxial with layered composition modulation of the expected periodicity. Their electronic properties were studied by optical absorption and luminescence.

W. Weigmann

Papers

Epitaxial structures with alternate‐atomic‐layer composition modulation

Summary Abstract: Optical characterization of interface disorder in multiquantum well GaAs–AlxGa1−xAs superlattice structures