Time-resolved optical studies of electronic spin scattering in diluted magnetic semiconductor heterostructures

Femtosecond spin dynamics in diluted magnetic semiconductor heterostructures are probed to observe the effects of dimensionality, local magnetic environment, and quantum confinement on electronic spin scattering. Low temperature polarization-resolved upconversion spectroscopy is used to explore the interplay between electronic and magnetic spins with femtosecond resolution in three distinct spin-engineered structures.; The first system is a set of ZnSe/Zn{dollar}sb{lcub}1-x{rcub}{dollar}Mn{dollar}sb{lcub}x{rcub}{dollar}Se spin superlattices in which the confining potential can be tuned by a magnetic field in a single structure. Studies reveal direct real-time observation of energy-dependent spin relaxation. Time-resolved polarization measurements reveal spin-flip scattering of carriers confined to a single magnetic quantum well. The spin scattering dynamics undergo a marked change as the magnetic field is increased to the point where a spin superlattice can form. Exciton lifetimes and spin relaxation are seen to be strongly dependent on both the energy and location of spin states in this heterostructure.; The second set of studies utilize ZnSe/Zn{dollar}sb{lcub}1-x{rcub}{dollar}Cd{dollar}sb{lcub}x{rcub}{dollar}Se double quantum wells coupled by thin Zn{dollar}sb{lcub}1-y{rcub}{dollar}Mn{dollar}sb{lcub}y{rcub}{dollar}Se barriers permitting exploration of the role of spin scattering during tunneling. In a magnetic field, the Zeeman splitting of the band structure in the barrier produces a spin dependent coupling between the wells. Systematic measurements reveal that carrier spin scattering to a final orientation is dependent on the initial spin state. Furthermore, both spin and energy relaxation, and the ultimate recombination state may be tuned by varying the applied field or the magnetic environment.; The last system is a new class of magnetic semiconductor heterostructures wherein fractional monolayers of the magnetic semiconductor MnSe are distributed digitally in a ZnSe/Zn{dollar}sb{lcub}1-x{rcub}{dollar}Cd{dollar}sb{lcub}x{rcub}{dollar}Se quantum well. While maintaining a fixed number of magnetic spins, rearrangement of the moments into a comb of planes results in heterostructures with well defined two-level electronic spin systems. Experiments reveal that carrier spin-flip scattering is solely dependent on the energy splitting between the Zeeman split spin states and is independent on the local magnetic environment.