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We have studied the magneto-photo luminescence (PL) of triply stacked layers of self-assembled InP quantum dots, For a small separation of the uppermost dot in (he triple stack from the other two closely stacked layers, only one PL peak is observed, whereas for a large separation two PL peaks are present: a broad low-energy and a narrow high-energy peak. We propose a model in which the low-energy peak is associated with the uppermost dot where alignment faults result in enhanced size fluctuations, broadening the line, The narrow high-energy peak originates from charges located in the double stack. In the large separation regime, an increased broadening of the PL line-width indicates that the size fluctuations are augmented as the layer separation is increased from 15 to 30 nm. (C) 2002 Elsevier Science B.V. All rights reserved.

We report photoluminescence (PL) measurements on doubly-stacked Layers of self-assembled InP quantum dots. The amount of material in the lower layer is kept constant. whilst in the upper layer it is systematically reduced. Zero-field PL measurements demonstrate that for each stack only one dot (the largest one) is occupied by an electron, and that when the amount of InP in both layers is the same the upper dots are larger. The behaviour of the holes, which art: confined by strain in the structure. is revealed by high field (50 T) PL experiments. The holes are found to be increasingly localised to a smaller and smaller volume as the size of the dots in the upper layer is reduced.

We have studied the magnetophotoluminescence of doubly stacked layers of self-assembled InP quantum dots in a GaInP matrix. 4.0±0.1 monolayers of InP were deposited in the lower layer of each sample, whereas in the upper layer 3.9, 3.4, and 3.0 monolayers were used. Low-temperature photoluminescence measurements in zero magnetic field are used to show that, in each case, only one layer of dots is occupied by an electron, and imply that when the amount of InP in both layers is the same, the dots in the upper layer are larger. High-field photoluminescence data reveal that the position and extent of the hole wave function are strongly dependent on the amount of InP in the stack. ©2001 American Institute of Physics.

We have measured the photoluminescence of stacked layers of self-assembled InP quantum dots in magnetic fields up to 50 T. In the samples with three stacked layers of dots strong electronic coupling was clearly observed for layer separations of 2 and 4 nm. For a sample with only two stacked layers of dots (separated by 4 nm) no coupling was observed. We attribute this difference in behaviour to a model in which the coupling is via holes that are weakly bound in the GaInP layers between the dots. Since the doubly stacked layers have only one such layer, no coupling is possible. (C) 2000 Elsevier Science B.V. All rights reserved.

We have studied the photoluminescence of doubly stacked layers of InP quantum dots in magnetic fields up to 50T. We find that in contrast to the triply stacked layers studied previously, which were strongly coupled for layer separations of 4 nm or less, the dots in the double layers do not couple. We explain this surprising difference in behaviour by proposing a model in which the holes are confined in the GaInP layers separating the stacked dots. For triply stacked dots two such layers exist, allowing the possibility of coupling via the holes. In doubly stacked dots, there is only one such layer, thus coupling is absent. Our model is consistent with measurements of the exciton masses and radii in the dl,ts, and with calculations of electron and hole wave functions in self-assembled quantum dots. (C) 2000 Elsevier Science B.V. All rights reserved.

We report photoluminescence measurements on stacked self-assembled InP quantum dots in magnetic fields up to 50 T. For triply stacked layers the dots become strongly coupled when the layer separation is 4 nm or less. In contrast, doubly stacked layers show no sign of coupling. We explain this puzzling difference in coupling by proposing a model in which the holes are weakly confined in the GaxIn1-xP layers separating the layers of dots, and are responsible for the coupling. Since only one such intervening layer exists in the doubly stacked dots coupling is excluded. Our model is strongly supported by the exciton masses and radii derived from our experimental results, and is consistent with available theory.

We report magnetophotoluminescence measurements of stacked layers of self-assembled InP quantum dots. With a magnetic field applied in the growth direction we have determined the exciton reduced mass from the field dependence of the photoluminescence energy. By applying a magnetic field perpendicular to the growth direction, we have analyzed the spatial confinement of the dots in the growth direction. We observe a large increase in the shift of the exciton energy between 0 and 50 T when the thickness of the GaInP spacer layer between the dots is reduced from 8 to 4 nm. This indicates a decrease in spatial confinement in the growth direction which we attribute to strong electronic coupling between vertically stacked dots. (C) 1999 American Institute of Physics. [S0003-6951(99)03832-2].

It is shown that the observed quantum Hall effect in epitaxial layers of heavily doped n-type GaAs with thickness (50-140 nm) larger the mean free path of the conduction electrons (15-30 nm) and, therefore, with a three-dimensional single-particle spectrum is induced by the electron-electron interaction. The Hall resistance Rxy of the thinnest sample reveals a wide plateau at small activation energy Ea=0.4 K found in the temperature dependence of the transverse resistance Rxx. The different minima in the transverse conductance Gxx of the different samples show a universal temperature dependence (logarithmic in a large range of rescaled temperatures T/T0) that is reminiscent of electron-electron-interaction effects in coherent diffusive transport. © 1999 The American Physical Society., SCOPUS: ar.j, info:eu-repo/semantics/published

We report the first photoluminescence (PL) measurements on stacked layers of self-assembled InP quantum dots in pulsed magnetic fields up to 50 T at 4.2 K. A strong increase of the diamagnetic shift with magnetic field parallel and perpendicular to the growth direction is observed by decreasing the stacked layer separation from 8 to 4 nm, indicating that in latter case the quantum dot layers are strongly coupled. This is confirmed by the decrease in PL line width, which is determined by the height homogeneity of a single dot or by the fluctuation of the total height of the coupled layers.