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

Abstract

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 [11¯0] 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.