L. Maingault

Enhanced carrier confinement in quantum dots by raising wetting layer state energy

A quantum dot design is proposed where the wetting layer states are shifted to higher energies. It is realized by including CdTe quantum dots between two thin MgTe layers. As both materials have nearly the same lattice parameter, the first MgTe layer forms a wetting layer with high carrier state energy. Consequently, the radiative regime of the dots is significantly extended to higher temperatures. The unusual temperature-dependence of the decay time is discussed using a model for localized and delocalized states.

Cross-sectional scanning tunneling microscopy study on II-VI multilayer structures

Cross-sectional scanning tunneling microscopy is used to study in the atomic scale the structural properties of ZnSeTe∕ZnTe multiple quantum wells and N:ZnTe delta-doped structures. Some peculiar effects are found on the cleaved (110) ZnTe surface plane, which have not been observed in III–V semiconductors. In particular, cleavage induced monatomic wide vacancy chains are always present on the Te sublattice. Furthermore, the semiconductor surface is manipulated when certain positive voltages are applied to the sample. Regarding the heterostructures, the ZnSeTe∕ZnTe quantum wells are found to have abrupt interfaces and the Se concentration is determined to be significantly larger than the nominal value.

Temperature Dependence Of The Exciton Homogeneous Linewidth In CdTe and CdSe Self‐assembled Quantum Dots: Limit Of Single Photon Source Operation

Excitonic emission in single CdTe/ Zn0.7Mg0.3Te and CdSe/ZnSe quantum dots has been obtained up to 160 K and 220 K respectively. The study of the linewidth thermal broadening allows us to estimate the temperature limit of single photon emission in CdTe and CdSe QDs.

Probing and Controlling the Spin State of Single Magnetic Atoms in an Individual Quantum Dot

Publisher Summary This chapter reviews that when magneto-electronic devices scales down, it becomes increasingly important to understand the properties of a single magnetic atom in a solid-state environment. Atomic scale surface probes are successfully used in this regard. More recently, optical probing of both magnetic and non-magnetic atoms in semiconductors is demonstrated. Magnetically doped semiconductors are used in the fabrication of electrically active devices that control the magnetic properties such as transition temperature and coercitive field. In these devices, a macroscopic number of magnetic atoms was manipulated. It presents here electrically active devices that control the charge state of an individual II–VI quantum dot (QD) doped with a single Mn atom. Quantum dots doped with magnetic atoms and filled with a tunable number of carriers can behave like tunable nanomagnets. The chapter also focuses on the observation of an individual spin in a QD that opens new possibilities in information storage. The spin of an isolated Mn atom should present a relaxation time in the millisecond range. This property could be exploited to store digital information on a single atom.

Controlling Mn concentration into CdTe quantum dots

Method of growth to get one single Mn in self‐assembled semiconductors Quantum Dot (QD) is presented. A simple model proves that a very low Mn density is needed prior to the QD nucleation. This was reached by inserting a thin ZnTe spacer between a Zn1−xMnxTe buffer and the CdTe QD layer. Control of Mn ions density is made by changing the thickness of the ZnTe spacer, with good reproducibility. Qualitative and quantitative comparison of optical spectra for different samples assess this original method of growth.

Engineering The Wetting Layer States To Reach Room Temperature Emission For CdTe Quantum Dot Structures

The confinement of excitons in CdTe/ZnMgTe quantum dots is shown to be significantly enhanced by the insertion of thin MgTe barrier layers next to the CdTe quantum dot layer. This has the effect to rise up the wetting layer states. As a consequence, excitons remain in the quantum dots up to higher temperatures.