Jacek K. Furdyna

Structural properties of Bi{sub 2}Te{sub 3} and Bi{sub 2}Se{sub 3} topological insulators grown by molecular beam epitaxy on GaAs(001) substrates

Thin films of Bi2Te3 and Bi2Se3 have been grown on deoxidized GaAs(001) substrates using molecular beam epitaxy. Cross-sectional transmission electron microscopy established the highly parallel nature of the Te(Se)-Bi-Te(Se)-Bi-Te(Se) quintuple layers deposited on the slightly wavy GaAs substrate surface and the different crystal symmetries of the two materials. Raman mapping confirmed the presence of the strong characteristic peaks reported previously for these materials in bulk form. The overall quality of these films reveals the potential of combining topological insulators with ferromagnetic semiconductors for future applications.

Near-bandgap wavelength dependence of long-lived traveling coherent longitudinal acoustic phonons in GaSb-GaAs heterostructures

We report first studies of long-lived oscillations in optical pump-probe measurements on GaSb-GaAs heterostructures. The oscillations arise from a photogenerated coherent longitudinal acoustic phonon wave, which travels from the top surface of GaSb across the interface into the GaAs substrate, providing information on the optical properties of the material as a function of time/depth. Wavelength-dependent studies of the oscillations near the bandgap of GaAs indicate strong correlations to the optical properties of GaAs.

Direct evidence of the fermi-energy-dependent formation of Mn interstitials in modulation doped Ga1-yAlyAs/Ga1-xMnxAs/Ga1-yAlyAs heterostructures

Using ion channeling techniques, we investigate the lattice locations of Mn in Ga{sub 1-x}Mn{sub x}As quantum wells between Be-doped Ga{sub 1-y}Al{sub y}As barriers. The earlier results showed that the Curie temperature T{sub C} depends on the growth sequence of the epitaxial layers. A lower T{sub C} was found in heterostructures in which the Ga{sub 1-x}Mn{sub x}As layer is grown after the modulation-doped barrier. Here we provide direct evidence that this reduction in T{sub C} is directly correlated with an increased formation of magnetically inactive Mn interstitials. The formation of interstitials is induced by a shift of the Fermi energy as a result of the transfer of holes from the barrier to the quantum well during the growth.

Time-resolved second harmonic generation study of buried semiconductor heterointerfaces using soliton-induced transparency

The transient second harmonic generation and linear optical reflectivity signals measured simultaneously in reflection from GaAs/GaSb/InAs and GaAs/GaSb heterostructures revealed a new mechanism for creating self-induced transparency in narrow bandgap semiconductors at low temperatures, which is based on the dual-frequency electro-optic soliton propagation. This allows the ultrafast carrier dynamics at buried semiconductor heterointerfaces to be studied.

Molecular beam epitaxial growth of high-reflectivity and broad-bandwidth ZnTe/GaSb distributed Bragg reflectors

This paper reports the molecular beam epitaxial growth and characterization of high-reflectivity and broad-bandwidth distributed Bragg reflectors (DBRs) made of ZnTe/GaSb quarter-wavelength (λ/4) layers for optoelectronic applications in the midwave infrared spectral range (2–5 μm). A series of ZnTe/GaSb DBRs has been successfully grown on GaSb (001) substrates using molecular beam epitaxy (MBE). During the MBE growth, a temperature ramp was applied to the initial growth of GaSb layers on ZnTe to protect the ZnTe underneath from damage due to thermal evaporation. Post-growth characterization using high-resolution x-ray diffraction, atomic force microscopy, and transmission electron microscopy reveals smooth surface morphology, low defect density, and coherent interfaces. Reflectance spectroscopy results show that a DBR sample of seven λ/4 pairs has a peak reflectance as high as 99.0% centered at 2.56 μm with a bandwidth of 517 nm.

Anisotropic magnetoresistance inGa1−xMnxAs

We have measured the magnetoresistance in a series of Ga

Domain wall dynamics in GaMnAsP films with perpendicular anisotropy

_{1-x}

Resonant nano-photoluminescence of single CdSe/ZnSe self-assembled quantum dots

Mn

Ultrafast laser-induced coherent spin dynamics in ferromagneticGa1−xMnxAs/GaAsstructures

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MAGNETOLUMINESCENCE STUDY OF A TWO-DIMENSIONAL ELECTRON GAS CONFINED IN DILUTED-MAGNETIC-SEMICONDUCTOR QUANTUM WELLS

As samples with 0.033