INCREASED THERMAL-STABILITY DUE TO ADDITION OF GE IN B SI(1-1-1) HETEROSTRUCTURES/

Of the numerous adatom-induced root 3 surfaces, only B root 3/Si(1 1 1 ) has the adatom in a substitutional site. Thus, research on Si/B root 3/Si(1 1 1) has been motivated by the desire to create a new class of so-called delta-doped materials, in which holes produced by boron are trapped at the two-dimensional interface. Unfortunately, this structu re degrades with low temperature annealing. However, the addition of G e is expected to reduce the interfacial strain and so improve thermal stability. Previously, we have used synchrotron radiation and anomalou s X-ray diffraction techniques to determine ex situ the atomic structu re of such a system. Here, using synchrotron radiation we have studied in situ heterostructures grown by molecular beam epitaxy and verified the improved stability. Specifically, we find that including Ge exten ds the annealing range by more than 100 degrees C without significant degradation. We have also successfully grown a heterostructure consist ing of two B root 3 layers separated by a 40 Angstrom spacer.