Abstract

GaMnAs is a highly interesting material system for future spintronic devices. We present a study of nonmagnetic GaAs quantum wells (QW) embedded in AlGaAs barriers, close to a ferromagnetic GaMnAs layer. The samples were grown on semi‐insulating GaAs(001) and contain two QWs, where one QW is close to the GaMnAs layer and the other one is farther away (120 nm), and serves as a reference. We studied the influence of the barrier material, e.g. a short‐period AlAs/GaAs superlattice. The photoluminescence (PL) of the upper QWs, close to the GaMnAs layer, show a significant broadening. Additionally, time‐resolved Faraday rotation (TRFR) reveals that the spin lifetime in the upper QW is up to 30 times longer than that in the lower QW. We attribute these observations to backdiffusion of Mn into the QW during and after growth. Both, the PL and the TRFR, are highly sensitive to small quantities (below 0.05 %) of Mn and allow us to study the efficiency of barrier layers in suppressing Mn diffusion.

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