Role of oxygen on the electrical activation of B in Ge by excimer laser annealing

The electrical activation of B+ implanted at 20keV with a fluence of 1x10(15)cm(-2) in crystalline Ge, following a laser annealing (=308nm) with multipulses (1, 3, or 10), was studied. Incomplete activation was observed for all the irradiated samples. The inactivation of B was correlated to the presence of oxygen, coming from the native germanium oxide. The formation of B-O complexes occurs during the solidification of the Ge, hampering the substitutionality and the electrical activation of the dopant. We estimated the diffusivity of oxygen in liquid Ge, approximate to 3x10(-5)cm(2)s(-1), by fitting the experimental O concentration profiles. These studies clarify the key role played by oxygen on the electrical activation of B in Ge by laser annealing, and have to be considered for the fabrication of junctions in advanced scaled Ge-based devices.