Ultra-High B Doping During Si(1-X)ge(x)(001) Gas-Source Molecular-Beam Epitaxy: A Mechanistic Study of Layer Growth Kinetics, Dopant Incorporation, Electrical Activation, and Carrier Transport

Abstract

CB in Si1-xGex(001) increases with precursor flux ratio and B is incorporated into active sites at concentrations to C*B (Ts) = 2.5 x 1020 and 4.6 x 1020 cm-3 for x = 0 and 0.18 at Ts = 600 and 500°C, respectively. At higher B concentrations, there is a large decrease in the activated fraction of incorporated B. The total acceptor concentration continues to increase. No B precipitates or misfit dislocations were detected by HR-XRD or TEM. The out-of-plane lattice constant a⊥ decreases linearly with increasing C*B and non-linearly, for CB > C*B . Electrical properties are in good agreement with theoretical values to C*B . When thetaB > thetaB,sat, B accumulates in the upper layer, and a parallel incorporation channel becomes available in which B is incorporated as B-pairs which are electrically inactive.