Seminars Archive

In-situ structural assessment of III-V semiconductor surfaces and interfaces by grazing incidence X-ray diffraction

Abstract
An ultra-high vacuum surface diffraction station has been operated at the
LURE synchrotron radiation facility since 1987. Compared to similar
beamlines, this set up has the unique feature to couple the UHV
diffractometer with a molecular beam epitaxy chamber for arsenic based
III-V compounds. A large part of the scientific program both from external
users and from the local staff is then concerned with gallium (indium)
arsenide related research. After a brief description of the experimental
set-up, a survey of the recent achievements in this field will be
presented. The emphasis will be put on the surface structure of ternary
InxGa1-xAs alloys strained on GaAs, where evidence for cation ordering at
the surface of a disordered bulk has been obtained through the
crystallographic analysis of the 2x3 recontruction1. The departure from
theideal surface composition In0.67Ga10.33As induces faulted boundaries
responsible for the observed shift of the diffraction maxima towards
incommensurate 2xn positions. Being sensitive to the gallium and indium
distribution in the near surface layers, X-ray diffraction enables not only
to confirm but also to go beyond the description of these ternary surfaces
provided by scanning tunnelling microscopy2.