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.