Bi surfactant mediated epitaxy of Ge on Si(111)

We have tested Bi for the surfactant mediated epitaxy of Ge on Si(111). Isl anding of Ge is prevented and a 2D layer growth of smooth and continuous Ge films is observed. The lattice mismatch is accommodated by a periodic arra y of dislocations confined to the Si/Ge interface. The large covalent radiu s of Bi reduces the binding energy, allowing Very efficient segregation and low doping levels even at low growth temperatures. Unfortunately, this res ults also in a high Bi desorption flux limiting the possible growth tempera tures below 600 degrees C. Consequently the Ge films show a high defect den sity in the order of 10(8) cm(-2) for stacking faults and 10(9) cm(-2) for dislocations which limit electron Hall mobility to values below 700 cm(2)/V s at room temperature. (C) 1999 Elsevier Science S.A. All rights reserved.