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5 Acta Physica Polonica A

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Excitonic Giant Zeeman Effect in Wide Gap Diluted Magnetic Semiconductors Based on ZnO and GaN

100%

Pacuski W. , Ferrand D. , Kossacki P. , Marcet S. , Cibert J. , Gaj J. , Golnik A.

Acta Physica Polonica A

2006

tom 110

nr 3

303-309

We present a theoretical description of the excitonic giant Zeeman effect observed in wide gap diluted magnetic semiconductors (Zn,Co)O and (Ga,Mn)N. In these materials, A and B excitons present quite complex energy shifts and change of oscillator strengths under magnetic field. These features can be well reproduced using an excitonic Hamiltonian, taking into account ion-carrier exchange, wurtzite trigonal crystal field, spin-orbit and electron-hole exchange interactions.

Optical Properties of Manganese-Doped Individual CdTe Quantum Dots

100%

Besombes L. , Léger Y. , Maingault L. , Ferrand D. , Bougerol C. , Mariette H. , Cibert J.

Acta Physica Polonica A

2005

tom 108

nr 4

527-540

The magnetic state of a single magnetic ion (Mn^{2+}) embedded in an individual quantum dot is optically probed using microspectroscopy. The fine structure of a confined exciton in the exchange field of a single Mn^{2+} ion (S=5/2) is analyzed in detail. The exciton-Mn^{2+} exchange interaction shifts the energy of the exciton depending on the Mn^{2+} spin component and six emission lines are observed at zero magnetic field. The emission spectra of individual quantum dots containing a single magnetic Mn atom differ strongly from dot to dot. The differences are explained by the influence of the system geometry, specifically the in-plane asymmetry of the quantum dot and the position of the Mn atom. Depending on both these parameters, one has different characteristic emission features which either reveal or hide the spin state of the magnetic atom. The observed behavior in both zero field and under magnetic field can be explained quantitatively by the interplay between the exciton-manganese exchange interaction (dependent on the Mn position) and the anisotropic part of the electron-hole exchange interaction (related to the asymmetry of the quantum dot).

Control of Ferromagnetism in Cd_{1-x}Mn_xTe Based Quantum Wells

84%

Bertolini M. , Boukari H. , Ferrand D. , Cibert J. , Tatarenko S. , Gilles B. , Maślana W. , Gaj J. , Kossacki P. , Dietl T.

Acta Physica Polonica A

2002

tom 102

nr 4-5

603-608

New structures aiming at controlling the ferromagnetic properties of diluted magnetic semiconductor quantum wells are presented. The carrier density is controlled by applying a voltage across a p-i-n diode. A new method, creating a 2D hole gas by adjusting the distance between the quantum well and surface, offers opportunities for a broader range of structures.

Carrier Density Control by Illumination in Surface Doped, p-Type (Cd,Mn)Te Quantum Wells

84%

Maślana W. , Kossacki P. , Gaj J. , Ferrand D. , Bertolini M. , Tatarenko S. , Cibert J. , Kutrowski M. , Wojtowicz T.

Acta Physica Polonica A

2006

tom 110

nr 2

255-262

We report both decrease and increase in the 2D carrier gas density in a simple (Cd,Mn)Te/(Cd,Mg)Te heterostructure with (Cd,Mn)Te quantum well. The two effects were achieved by light with different photon energies. The quantum wells were 10 nm wide with 2D hole gas supplied by surface states. For the sample with 25 nm cap layer thickness, it was possible to tune the hole gas concentration from almost empty well (hole density below 1×10^{10} cm^{-2}) to 45×10^{10} cm^{-2}. The illumination with 425 nm wavelength almost doubled the hole gas density from the initial 24×10^{10} cm^{-2}. The depletion mechanism was most effective for illumination with the orange (575 nm) light.

Photoluminescence of p-Doped Quantum Wells with Strong Spin Splitting

84%

Boukari H. , Kossacki P. , Bertolini M. , Ferrand D. , Cibert J. , Tatarenko S. , Gaj J. , Deveaud B. , Ciulin V.

Acta Physica Polonica A

2004

tom 106

nr 3

299-310

Photoluminescence of p-type modulation doped (Cd,Mn)Te quantum wells is studied with carrier density up to 5×10^{11} cm^{-2} at various spin splittings. This splitting can be made larger than the characteristic energies of the system thanks to the giant Zeeman effect. At small spin splitting and regardless of the carrier density, the photoluminescence exhibits a single line, which corresponds to the charged exciton in the singlet state. Above a certain spin splitting, the charged exciton is destabilized in favor of the exciton at vanishing hole density, and in favor of a double line at higher carrier density. It is found here that the charged exciton destabilization energy hardly depends on the carrier density. The double line is found to be band-to-band like, with the same initial state - where the holes have the same spin orientation - and final states that differ by some excitation of the 2D hole gas. In addition, the spin splitting needed to fully polarize the hole gas is twice smaller than expected from the single particle image and gives a unique insight into many-body effects in the hole gas.