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In YBa2Cu3O6+x the tetragonal to orthorhombic transition occurs around x equals 0.3, followed by a continuum variation of lattice parameters. Hence both, the structural and superconducting properties, depend upon the oxygen content in CuO chains. Conversel ...
Strain-compensated InAlAs/lnGaAs HEMT structures, grown on InP substrate, have been investigated in terms of structural and electrical properties. From detailed x-ray diffraction (XRD) investigations the compensation index and the evolution of the strain s ...
The kinetics of surface processes during the growth of GaN by molecular-beam epitaxy (MBE) with ammonia as the source of reactive nitrogen is studied theoretically and experimentally. A model of surface processes is developed taking into account specific e ...
Microcavity light-emitting diodes (MCLEDs) with top-emitting geometry have been grown by molecular beam epitaxy on GaAs and Si substrates. External quantum efficiencies of up to 10% were obtained for 420 x 420 mu m(2) homoepitaxial devices. The efficiency ...
We present here measurements on hexagonal cavities that have areas between 2.0 and 8.6 mu m/sup 2/. The 2D triangular lattice PBG mirrors are etched into a GaAs/AlGaAs waveguide heterostructure with 3 layers of InAs quantum dots at the centre of a 240 nm t ...
Microcavity light emitting diodes (MCLEDs) present several interesting features compared to conventional LEDs such as narrow linewidth, improved directionality and high efficiency. We report here on MCLEDs with a top emitting geometry. The MCLED layers wer ...
The properties of semiconductor laser diodes for trace gas measurements are reviewed. First, the modulation characteristics of these lasers are discussed. Then, two sensitive spectroscopic methods using a frequency-modulated near-IR laser are presented and ...
InGaN/GaN quantum wells (QWs) were grown by molecular-beam epitaxy on c-plane sapphire substrates. The growth of InGaN is carried out at 550 degrees C with a large V/III ratio to counteract the low efficiency of NH3 at that temperature and to promote the t ...
The kinetics of GaN growth by MBE using ammonia as the reactive nitrogen source is studied both under Ga-rich and N-rich conditions. It is shown that adsorption site blocking by Ga and N atoms as well as by surface NH, complexes is a crucial factor to cont ...
Photoluminescence lifetimes of the n = 2 level in a large quantum well show a clear nonmonotonic dependence on the density of optically generated carriers. Varying the power density over five orders of magnitude we prove directly the high efficiency of car ...