Phys. Rev. Lett. 94, 026407 (2005) [4 pages]Direct Evidence for Shallow Acceptor States with Nonspherical Symmetry in GaAsReceived 22 June 2004; published 20 January 2005 We investigate the energy and symmetry of Zn and Be dopant-induced acceptor states in GaAs using cross-sectional scanning tunnelling microscopy (STM) and spectroscopy at low temperatures. The ground and first excited states are found to have a nonspherical symmetry. In particular, the first excited acceptor state has a Td symmetry. Its major contribution to the STM empty-state images allows us to explain the puzzling triangular shaped contrast observed in the empty-state STM images of acceptor impurities in III-V semiconductors. © 2005 The American Physical Society URL:
http://link.aps.org/doi/10.1103/PhysRevLett.94.026407
DOI:
10.1103/PhysRevLett.94.026407
PACS:
71.55.Eq, 68.37.Ef
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