Atomic structure of the "non-polar" (110) surface of
some III-V compound semiconductors.
(a) The ideal, bulk-like, unrelaxed surface of GaAs(110).
(b) The actual structure involves a relaxation which results
in almost planar arangement of the first three atomic planes.
The gallium atoms have sp2 bonding configuration while the
arsenic atoms have filled dangling bond states.
This configuration leaves no surface states in the
middle of the band gap.