Theory of polarization dependent intersubband transitions in p-type SiGeÕSi self-assembled quantum dots

Electronic and optoelectronic properties of SiGe/Si self-assembled quantum dots are calculated by the eight-band k"p method with a revised set of parameters. The model confirms that the Si12xGex transforms to a type-II structure when x is greater than 0.25 and given accurate effective masses for Si and Ge. The polarization dependent absorption spectra show a behavior quite different from what is seen in conduction band intersubband transitions in self-assembled InGaAs/GaAs dots. In-plane or x-polarized absorption increases as germanium content is increased but z-polarized absorption is highest for low germanium content. It is also shown that the z-polarized absorption can be of the same magnitude as in the x-direction by adjusting the dot composition. We also clarify how the envelope functions and the Block parts of the electronic states contribute to the absorption spectra. © 2004 American Institute of Physics. @DOI: 10.1063/1.1755848#