A. M. Yakunin

Spatial structure of an individual Mn acceptor in GaAs.

The wave function of a hole bound to an individual Mn acceptor in GaAs is spatially mapped by scanning tunneling microscopy at room temperature and an anisotropic, crosslike shape is observed. The spatial structure is compared with that from an envelope-function, effective mass model and from a tight-binding model. This demonstrates that anisotropy arising from the cubic symmetry of the GaAs crystal produces the crosslike shape for the hole wave function. Thus the coupling between Mn dopants in GaMnAs mediated by such holes will be highly anisotropic.

Spatial Structure of Mn-Mn Acceptor Pairs in GaAs

The local density of states of Mn-Mn pairs in GaAs is mapped with cross-sectional scanning tunneling microscopy and compared with theoretical calculations based on envelope-function and tight-binding models. These measurements and calculations show that the crosslike shape of the Mn-acceptor wave function in GaAs persists even at very short Mn-Mn spatial separations. The resilience of the Mn-acceptor wave function to high doping levels suggests that ferromagnetism in GaMnAs is strongly influenced by impurity-band formation. The envelope-function and tight-binding models predict similarly anisotropic overlaps of the Mn wave functions for Mn-Mn pairs. This anisotropy implies differing Curie temperatures for Mn delta-doped layers grown on differently oriented substrates.

Charge manipulation and imaging of the Mn acceptor state in GaAs by Cross-sectional Scanning Tunneling Microscopy

Abstract An individual Mn acceptor in GaAs is mapped by cross-sectional scanning tunneling microscopy (X-STM) at room temperature and a strongly anisotropic shape of the acceptor state is observed. An acceptor state manifests itself as a cross-like feature which we attribute to a valence hole weakly bound to the Mn ion forming the (Mn 2+ 3d 5 +hole) complex. We propose that the observed anisotropy of the Mn acceptor wavefunction is due to the d-wave present in the acceptor ground state.

Imaging of the (Mn2+3d5 + Hole) Complex in GaAs by Cross‐Sectional Scanning Tunneling Microscopy

We present results on the direct spatial mapping of the wave function of a hole bound to a Mn acceptor in GaAs. To investigate individual Mn dopants at the atomic scale in both ionized and neutral configurations, we useda room temperature cross-sectional scanning tunneling microscope. We found that in the neutral configuration manganese manifests itself as an anisotropic cross-like feature. We attribute this feature to a hole, weakly bound to the Mn ion forming the (Mn 2 + 3d 5 + hole) complex.