Photoluminescence Lifetime and Structure of Molecular Beam Epitaxy Porous Si1 − xGex Grown on Si

A study is presented of the local structure of intense visible light emitting porous SiGe with an initial Ge fraction of 30 at% grown on boron doped-Si substrates by Solid State Molecular Beam Epitaxy (SS-MBE). Analysis of the Extended X-ray Absorption Fine Structure (EXAFS) of the SS-MBE grown SiGe and their anodized porous counterparts processed under various conditions is used to obtain a better understanding of the visible light-emitting mechanism of porous SiGe. In addition, the photoluminescence decay dynamics of porous SiGe are examined and are found to differ in terms of speed and behaviour from porous Si. We interpret the origin of visible PL of the porous MBE SiGe films by considering the quantum confinement effect, as in the interpretation of PL from porous Si, and the evolution of the SiGe Si like-band structure.