Search

We report the growth of InGaAs and InGaAsP quantum well heterostructures on InP substrates with [011] oriented grooves. We have shown that growth of these materials on non-planar substrates can result in lattice-mismatched layers on orientations other than (100) which in some cases gives rise to dislocations. In addition, the lateral patterning of quantum wells and quantum wire-like structures has been demonstrated in this material system. Finally, a quantum well laser, wherein lateral patterning of the well thickness was achieved by growing in a flat-bottomed groove, was fabricated. Without any additional growth steps these lasers exhibit a single stable spatial mode due to the waveguide formed at the groove. [ABSTRACT FROM AUTHOR]

We report cathodoluminescence (CL) imaging and transmission electron microscopy (TEM) studies of patterned GaAs/AlAs quantum well (QW) heterostructures grown by molecular beam epitaxy on periodically corrugated substrates. Faceting and surface diffusion during crystal growth result in significant lateral variations in QW thickness which translate quantum size effects into lateral band-gap patterning. The CL images directly display lateral periodic modulation in quantum well thickness and indicate the existence of two lateral potential wells formed at the bottom and apex of corrugations. Emission wavelengths are in agreement with TEM data on the patterned structures. Such periodic patterned QW heterostructures should be useful for the realization of arrayed one- and zero-dimensional semiconductor quantum structures, particularly lateral superlattice heterostructures. [ABSTRACT FROM AUTHOR]

For a variety of device applications, junction devices in particular, we have demonstrated a heterostructure system of Y1Ba2Cu3O7-y/Y1-xPrxBa2Cu3O7-y which maintains epitaxy over the entire Pr composition range x=0–1. We have grown both trilayer and multiperiod superlattices which show nearly single crystalline helium ion backscattering minimum yields of <6% in the topmost layer. X-ray diffraction measurements indicate c-axis orientation by a transverse scan across (005) line with a full width at half maximum of 0.6° and 0.4° on MgO and SrTiO3 substrates, respectively. Scanning Auger electron depth profiles and cross-sectional transmission electron micrographs indicate abrupt Pr/Y interfaces within one unit cell and virtually no disruption of the layered structure at the interface. These results indicate the potential for the growth of excellent heterostructures and superlattices of the high-temperature superconductors. [ABSTRACT FROM AUTHOR]

The GaAs-on-InP heteroepitaxial waveguides are demonstrated for the first time using molecular beam epitaxy. A propagation loss of 9.3 dB/cm was obtained for waveguides grown on a 3° off (100) InP substrate. Compared to the 16 dB/cm loss for waveguides on (100) InP substrates, the waveguides on misoriented InP substrates exhibited a significantly lower loss. Based on photoluminescence studies, we attribute the propagation loss in both samples mainly to optical absorption by crystal defects. Defect densities of 4×1017 cm-3 and 2×1017 cm-3 are estimated for material on (100) and 3° off (100) substrates, respectively. Such heteroepitaxial waveguides may have applications in long-wavelength photonic integrated circuits. [ABSTRACT FROM AUTHOR]

GaAs/AlGaAs superlattice heterostructures with layer thicknesses <=100 Å were grown by molecular beam epitaxy on nonplanar GaAs substrates. The resulting superlattices exhibit different periods, depending on the crystal plane on which they grow. Period variation of more than 50%, from 180 to 80 Å, was obtained for adjacent superlattice sections. The transition between regions of different periodicity was mostly smooth and occurred within lateral dimensions <=100 Å. Our results suggest that molecular beam epitaxy of superlattice heterostructures on patterned substrates provides a method for obtaining controllable lateral variations in physical properties which depend on the superlattice period. In particular, by growing quantum well heterostructures on nonplanar substrates, it might be possible to utilize the strong dependence of the carrier confinement energy on the well thickness in order to achieve lateral carrier confinement. [ABSTRACT FROM AUTHOR]