The incorporation of vacancy clusters and vacancy point defects during the growth of Si/Si0.64Ge0.36/Si structures were observed, for growth at 250 to 550C, by using positron annihilation spectroscopy. A clear correlation was observed between the electrical characteristics of the structures and the size and concentration of the clusters. A defect concentration of less than 5 x 1016/cm3 was required for the onset of 2-dimensional hole gas behavior. A further reduction in concentration, to below 1016/cm3, resulted in optimum electrical performance. The depth at which defects were observed increased with decreasing growth temperature, thus indicating the existence of defect mobility during growth or subsequent annealing.

Growth Temperature Dependence for the Formation of Vacancy Clusters in Si/Si0.64Ge0.36/Si Structures. A.P.Knights, R.M.Gwilliam, B.J.Sealy, T.J.Grasby, C.P.Parry, D.J.F.Fulgoni, P.J.Phillips, T.E.Whall, E.H.C.Parker, P.G.Coleman: Journal of Applied Physics, 2001, 89[1], 76-9