  The spatial distribution of the local density of states (LDOS) at Mn
acceptors near the (110) surface of p-doped InAs is investigated by Scanning
Tunneling Microscopy (STM). The shapes of the acceptor contrasts for different
dopant depths under the surface are analyzed. Acceptors located within the
first ten subsurface layers of the semiconductor show a lower symmetry than
expected from theoretical predictions of the bulk acceptor wave function. They
exhibit a (001) mirror asymmetry. The degree of asymmetry depends on the
acceptor atoms' depths. The measured contrasts for acceptors buried below the
10th subsurface layer closely match the theoretically derived shape. Two
effects are able to explain the symmetry reduction: the strain field of the
surface relaxation and the tip-induced electric field.
