Ordering and Electronic Properties of Self-Assembled Si/Ge Quantum Dots

We have combined Ge island nucleation during molecular beam epitaxy in the Stranski-Krastanow growth mode with step bunching in Si/SiGe multilayers on vicinal Si substrates in order to realize self-ordered arrays of nanostructures. Surface steps and the local strain fields surrounding strain-relaxed SiGe nanostructures influence the island nucleation and result in spatially ordered stable arrays of Ge dots. The controlled formation of vertically correlated stacks of wires, dots or dots on wires by such self-ordering processes offer novel functionality for future applications like infrared detectors and memories. The fundamental electronic and optical properties of self-assembled Ge dots embedded in Si are analyzed by photoluminescence, admittance and intra valence band photocurrent spectroscopy.