Electron and hole spin lifetimes in Zn1−xMnxSe and Zn1−yFeySe based heterostructures

Abstract

We have studied carrier spin relaxation in diluted magnetic semiconductor (DMS) epilayer and spin superlattice samples using polarization and magnetic field dependent photoluminescence. The giant Zeeman splitting of the DMS materials permits unambiguous identification of electron and hole excitonic spin relaxation times. We find that the heavy hole spin lifetime τhs is comparable to the radiative recombination time τr, and substantially longer than the electron spin lifetime τes, with τhs/τr≊4 and τes/ τr≊0.06. We attribute these long spin lifetimes to the strain induced splitting of the bulk degenerate light and heavy hole bands, which inhibits mixing of the hole spin states and subsequent heavy hole spin flip relaxation processes. In the regime of weak confinement, the spin relaxation times are independent of the degree of quantum confinement, the number of interfaces, the magnetic ion concentration, and the magnetic species. We conclude that spin flip via exchange scattering between the carriers and magnetic ions is not the dominant excitonic spin relaxation mechanism.