Structure of III-Sb(001) growth surfaces: The role of heterodimers

We have determined the structure of AlSb and GaSb (001) surfaces prepared b y molecular beam epitaxy under typical Sb-rich device growth conditions. Wi thin the range of flux and temperature where the diffraction pattern is nom inally (1 x 3), we find that there are actually three distinct, stable (4 x 3) surface reconstructions. The three structures differ from any previousl y proposed for these growth conditions, with two of the reconstructions inc orporating mixed III-V dimers within the Sb surface layer. These heterodime rs appear to play an important role in island nucleation and growth.