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Stacked self-assembled In0.5Ga0.5As/GaAs quantum dot infrared photodetectors grown by low-pressure metal-organic chemical vapor deposition, with and without silicon dopants in the quantum dot layers, are investigated. The increase of dark currents observed at higher doping levels is attributed to higher defect density leading to stronger sequential resonant tunneling and to lowering of the operating temperature of the device. [ABSTRACT FROM AUTHOR]

We report the observation of efficient fluorescence upconversion in Sm-doped Gd2O3 nanopowders prepared by the spray pyrolysis method. The blue upconversion emission was observed with low-power continuous-wave excitation at 514, 561, 594, and 633 nm and with a pulsed femtosecond at 710 nm, in a laser scanning confocal microscope. This result indicates that Sm-doped Gd2O3 has the potential as a fluorescent label that may be excited in red, yellow, and green with blue emission. [ABSTRACT FROM AUTHOR]

We investigate photoluminescence from multilayer GaSb self-assembled quantum dots embedded in GaAs grown by metalorganic chemical vapor deposition. The spectra show the emission from quantum dots at about 1.09 eV and from the wetting layer at 1.39 eV. With increasing temperature the wetting layer emission quenches faster than the quantum dot emission. We also observe a decrease of the quantum dot peak energy at temperatures between 50 and 70 K and a peak shift with increasing excitation powers typical of type II structures. A large separation (300 meV) between the photoluminescence peaks from quantum dots and the wetting layer suggests differences in the intermixing at the GaSb/GaAs interface in the structures grown by metalorganic chemical vapor deposition and by molecular-beam epitaxy. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Raman measurements in backscattering configuration are employed to characterize the effect of nitrogen on the structural properties of a GaN[sub x]P[sub 1-x] alloy with x≤3%. The following effects of N incorporation on the vibrational spectra of GaNP are observed. First, frequencies of GaP-like and GaN-like longitudinal optical phonons exhibit strong compositional dependence, due to a combined effect of alloying and biaxial strain. Second, a dramatic quenching of two-phonon Raman scattering and an emergence of zone-edge GaP-like vibrations are observed. These effects are tentatively attributed to a local distortion of the GaNP lattice and/or compositional disorder in the alloy. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We report the observation of efficient fluorescence upconversion in Sm-doped Gd2O3 nanopowders prepared by the spray pyrolysis method. The blue upconversion emission was observed with low-power continuous-wave excitation at 514, 561, 594, and 633 nm and with a pulsed femtosecond at 710 nm, in a laser scanning confocal microscope. This result indicates that Sm-doped Gd2O3 has the potential as a fluorescent label that may be excited in red, yellow, and green with blue emission. [ABSTRACT FROM AUTHOR]