Direct evidence for shallow acceptor states with nonspherical symmetry in GaAs.
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 T(d) 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.
Mahieu
G
G
Institut d'Electronique, de Microélectronique et de Nanotechnologie, IEMN, (CNRS, UMR 8520), Département ISEN, 41 bd Vauban, 59046 Lille Cedex, France.
Grandidier
B
B
Deresmes
D
D
Nys
J P
JP
Stiévenard
D
D
Ebert
Ph
P