Efficiency of optical spin injection and spin loss from a diluted magnetic semiconductor ZnMnSe to CdSe nonmagnetic quantum dots

Abstract

Magneto-optical spectroscopy in combination with tunable laser spectroscopy is employed to study optical spin injection from a diluted magnetic semiconductor ͑DMS͒ ZnMnSe into nonmagnetic CdSe quantum dots ͑QDs͒. Observation of a DMS feature in the excitation spectra of the QD photoluminescence polarization provides clear evidence for optical spin-injection from the DMS to the QDs. By means of a rate equation analysis, the injected spin polarization is deduced to be about 32% at 5 T, decreasing from 100% before the injection. The observed spin loss is shown to occur during the spin injection process including crossing the heterointerfaces and energy relaxation within the QDs.

Growth-temperature dependence of optical spin-injection dynamics in self-assembled InGaAs quantum dots

“…2,3 However, there is still a need to take a closer look at the spin states during the injection of spin-polarized carriers or excitons, i.e., spin injection from a layered semiconductor barrier into a QD. [5][6][7][8][9][10] Such spin injection has the potential to provide the key to applying the spin states of QDs to spin-functional optical devices, as one would need to inject spin-polarized carriers from electrodes into QDs to achieve a practical device structure. Indeed, spin-polarized light emitting diodes and lasers based on QDs have been discussed; [11][12][13][14] however, spin injection is recognized as being much more difficult than spin-independent carrier injection due to the relative instability of the spin states in layered semiconductors, which allows them to easily relax during the injection process.…”

Impact of artificial lateral quantum confinement on exciton-spin relaxation in a two-dimensional GaAs electronic system

“…[1][2][3][4][5] Understanding the relaxation phenomena of the spin states of carriers or excitons is essential for determining the spin functionalities, because the spin information created and stored in these semiconductor quantum structures will be dissipated by the spin relaxation. It is well known that the spin-relaxation times of electrons, heavy holes (hhs), and excitons in the self-assembled QDs of compound semiconductors, such as InAs, 6 InGaAs, 7 CdSe, 8,9 and CdTe, 10 are significantly longer than those in two-or three-dimensional electronic systems such as QWs. [11][12][13][14][15] Therefore, a better and more comprehensive understanding of the effects of lateral quantum confinement of carriers or excitons on the spin-relaxation mechanism, in the absence of strong influences from complicated shapes and/or interfacial chemical states, is necessary for stabilization of the spin states in semiconductor QDs.…”

Anomalous spectral dependence of optical polarization and its impact on spin detection in InGaAs/GaAs quantum dots

“…This can be done by electrical spin injection from an adjacent ferromagnetic layer, 7 a diluted magnetic semiconductor, 8 Mn-doped InAs QD nanomagnets, 9 or by optical spin injection through circularly polarized optical excitation of an adjacent nonmagnetic semiconductor layer under optical orientation conditions. 6 Though properties of spin injectors and spin transport have received great attention during the past decade, [7][8][9][10][11][12][13] detailed studies of influence of non-resonant spin (carrier) injection density on optical polarization properties of QDs remain few. In optical orientation experiments of GaAs barriers and In(Ga)As wetting layers (WL) with a photon energy below the band-to-band (BB) optical transition energy from the spin-orbit split-off state of valence band (VB) to conduction band (CB), r þ -polarized excitation light preferably generates spin-down CB electrons whereas r À -polarized excitation light does the opposite.…”