Anisotropic distribution of stacking faults in (Ga,Mn)As digital ferromagnetic heterostructures grown by low-temperature molecular-beam epitaxy

摘要

We report on the microstructure of (Ga,Mn)As-based digital ferromagnetic heterostructures, which nominally consist of 40 periods of 0.75-monolayer (ML) Mn sheets between 17-ML GaAs spacer layers grown on GaAs(001) substrates by low-temperature molecular-beam epitaxy. Transmission electron microscopy studies reveal mainly stacking faults, which are preferentially coupled in V-shaped pairs with short intersecting lines along the [110] direction. With increasing the Ⅴ/Ⅲ beam equivalent pressure ratio, a stronger laterally inhomogeneous distribution of the Mn atoms is detected along the sheets resulting in a larger local strain and thus in a higher density of stacking fault pairs. Their anisotropic distribution is explained by the energetically favorable Mn-As bonding configuration that is induced by the specific surface morphology appearing at the low growth temperature.