Using ion channeling techniques, an investigation was made of the lattice locations of Mn in Ga1–xMnxAs quantum wells between Be-doped Ga1–yAlyAs barriers. Earlier results had shown that the Curie temperature Tc depended upon the growth sequence of the epitaxial layers. A lower Tc was found in heterostructures in which the Ga1–xMnxAs layer was grown after the modulation-doped barrier. Here, direct evidence was furnished that this reduction in Tc was directly correlated with an increased formation of magnetically inactive Mn interstitials. The formation of interstitials was induced by a shift in the Fermi energy as a result of the transfer of holes from the barrier to the quantum well during growth.

Direct Evidence of the Fermi-Energy-Dependent Formation of Mn Interstitials in Modulation-Doped Ga1–yAlyAs/Ga1–xMnxAs/Ga1–yAlyAs Heterostructures. K.M.Yu, W.Walukiewicz, T.Wojtowicz, W.L.Lim, X.Liu, M.Dobrowolska, J.K.Furdyna: Applied Physics Letters, 2004, 84[21], 4325-7