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Quantum dots (QDs) formed on GaAs(100) substrates by InAs deposition followed by (Al,Ga)As or (In,Ga,Al)As overgrowth demonstrate a photoluminescence (PL) peak that is redshifted (up to 1.3 μm) compared to PL emission of GaAs-covered QDs. The result is attributed to redistribution of InAs molecules in the system in favor of the QDs, stimulated by Al atoms in the cap layer. The deposition of a 1 nm thick AlAs cover layer on top of the InAs-GaAs QDs results in replacement of InAs molecules of the wetting layer by AlAs molecules, leading to a significant increase in the heights of the InAs QDs, as follows from transmission electron microscopy. This effect is directly confirmed by transmission electron microscopy indicating a transition to a Volmer-Weber-like QD arrangement. We demonstrate an injection laser based on this kind of QDs. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Reports on the results of photoluminescence analysis of ion-implanted and flash-annealed cadmium tellurium. Overview of the annealing of implantation-induced damage in crystals; Comparison between flash and furnace annealing; Example of the problem of separating growth and annealing-induced spectral characteristics from those due to dopant activation.

Presents a study that described a photoluminescence phenomenon resulting from carrier confinement at liquid-phase epitaxy gallium arsenide (GaAs)/AlGaAs heterointerface. Determination of the luminescence band of the GaAs/AlGaAs heterointerface; Relationship between the luminescence band and the heterointerface; Analysis of the peak energy of the luminescence band.

Investigates the effect of growth temperature using photoluminescence and deep level transient spectroscopy of high-quality InP grown by metalorganic chemical vapor deposition. Relationship between deep level transient spectroscopy and acceptor concentrations; Observations on several electron traps; Transitions observed in PL measurements.

Focuses on a study which examined the tunneling mechanism of electrons and holes to surface states from near-surface Al[sub0.3]Ga[sub0.7]As/GaAs quantum wells, using steady-state and time-resolved photoluminescence spectroscopy. Introduction to tunneling mechanism; Experimental procedure; Results and discussion.

Presents a study that investigated the polarization dependencies in the low-temperature photoluminescence and photoluminescence excitation of GaAs/AlGaAs quantum wire arrays. Discussion on the features of polarization modulation using a photoelastic modulator; Experiment conducted; Results.

Formation, emission, and lasing properties of strain-free InP(As)/AlInAs quantum dots (QDs) embedded in AlInAs microdisk (MD) cavity were investigated using transmission electron microscopy and photoluminescence (PL) techniques. In MD structures, the QDs have the nano-pan-cake shape with the height of ~2 nm, the lateral size of 20-50 nm, and the density of ~5×109 cm-2. Their emission observed at ~940 nm revealed strong temperature quenching, which points to exciton decomposition. It also showed unexpected type-I character, indicating In-As intermixing as confirmed by band structure calculations. We observed lasing of InP(As) QD excitons into whispering gallery modes in MD having the diameter of ~3.2 lm and providing a free spectral range of ~27 nm and quality factors up to Q~13 000. Threshold of ~50 W/cm2 and spontaneous emission coupling coefficient of ~0.2 were measured for this MD-QD system. [ABSTRACT FROM AUTHOR]

Presents a study that investigated the diffusion of copper into cadmium-tellurium (CdTe). Spectral features of CdTe; Effects of the diffusion on the photoluminescence intensity of the crystals; Role of cathodoluminescence and infrared microscopy in copper diffusion.

We report the formation of CdTe self-assembled quantum dots (QDs) on high-quality ZnTe epilayers grown on a GaSb substrate by molecular-beam epitaxy. Reflection high-energy electron diffraction and atomic force micro- scopy measurements clearly show the formation of CdTe QDs. Photoluminescence (PL) measurements on ZnTe-capped CdTe QD samples show a wide distribution of dot size. The temperature dependence of PL spectra indicates much stronger exciton localization in QDs than that in quantum wells. [ABSTRACT FROM AUTHOR]

We have studied the optical properties of pseudo-alloy monolayer InAs/GaAsN superlattices with highly planar interfaces. In spite of the two-dimensional growth mode, we found that the photoluminescence (PL) reveals strong exciton localization through the whole PL band, dominating the spectrum up to high excitation densities and observation temperatures. Pump-and-probe PL experiments provide the following time constants: (a) the exciton relaxation time to the ground states of the localization regions is found to be ∼40–70 ps, depending on the photon energy, and (b) the time for depopulation of these localized states is between 2 and 4 ns. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We report optical measurements (photoluminescence, Raman scattering, and infrared reflectance) of direct band gap and of optical phonon energies of Be[sub x]Zn[sub 1-x]Se alloys grown by MBE on (001) GaAs substrates for a wide range of Be concentrations. The high band gap of BeSe (5.15 eV) suggests the possibility of using isoternary alloys for ultraviolet optoelectronic applications. Be[sub x]Zn[sub 1-x]Se has the unique advantage that it can be lattice matched to Si at about x= 0.5. We observed a strong linear shift of the Be[sub x]Zn[sub 1-x]Se direct band gap to higher energies with increasing Be content (to 3.63 eV for x = 0.34). Furthermore, optical phonon parameters for the entire range of BeSe content have been obtained. Finally, polarized infrared and Raman spectra revealed local atomic ordering (anti-clustering) effects in the group-II sublattice. [ABSTRACT FROM AUTHOR]

We used high-spatial-resolution, low-temperature near-field scanning optical microscopy (NSOM) operating at magnetic fields B=0-10T to study the effects of Wigner localization (WL) on emission spectra of single self-organized InP/GaInP quantum dots (QDs) and investigate the stability of singly (trion) and doubly (tetron) charged exciton complexes in the weak quantum confinement regime. Using NSOM measurements together with configuration interaction calculations, we identify the dots having different electron population N(N=1-12), quantum confinement (ℏω0=0.6-8meV) and size D(D=70-170nm). For N=2, we observed a magnetic-field-induced molecular-droplet transition, accompanied by the decomposition of the tetron into a Wigner molecule complex (WMC), and the activation of rotovibronic structure. For N=1, unusually strong vibronic structure resulting from a trion-type WMC was observed. We have shown that magnetic-field-induced shifts of this structure allow measurement of single particle Fock-Darwin levels and angular momentum transitions of the WMC. In addition, we demonstrated the use of NSOM imaging to probe the charge density distribution and observed anomalous dependence of the image size on the quantum confinement, implying a pairing of electrons or formation of whispering gallery modes in the QD. We demonstrated that InP/GaInP QDs, provide a Wigner-Seitz radius (rs) up to 13, and that the measurements of NSOM magneto-optical spectroscopy using these dots makes it possible to study effects arising from strong Coulomb interaction of a few confined electrons (holes). [ABSTRACT FROM AUTHOR]