Direct evidence of the Fermi-energy-dependent formation of Mn interstitials in modulation-doped Ga1−yAlyAs/Ga1−xMnxAs/Ga1−yAlyAs heterostructures

Abstract

Using ion channeling techniques, we investigate the lattice locations of Mn in Ga1−xMnxAs quantum wells between Be-doped Ga1−yAlyAs barriers. Our earlier results showed that the Curie temperature TC depends on the growth sequence of the epitaxial layers. A lower TC was found in heterostructures in which the Ga1−xMnxAs layer is grown after the modulation-doped barrier. Here, we provide direct evidence that this reduction in TC is directly correlated with an increased formation of magnetically inactive Mn interstitials. The formation of interstitials is induced by a shift of the Fermi energy as a result of the transfer of holes from the barrier to the quantum well during the growth.