We show theoretically that it is possible to design SiGe-based quantum well structures in which conduction intersubband transitions are induced by normal incidence infrared radiation. A sp3d5s* tight binding model has been adopted to evaluate the electronic states and optical transitions between lowest conduction confined states of a superlattice composed of one pure Ge quantum well separated by SiGe alloys, grown along the  direction. We find that significant optical coupling between confined states in the Ge wells is achieved at normal incidence radiation by the off-diagonal elements of the mass tensor. The minimum energy Ge conduction valleys are, in fact, tilted with respect to the  growth axis. For comparison we show that no such coupling can be realized for the conduction states confined in a similar structure composed by Si quantum wells because the ellipsoids of the lowest conduction valleys are oriented along the growth direction.
|Autori interni:||VIRGILIO, MICHELE|
|Autori:||Virgilio M; Grosso G|
|Titolo:||Conduction intersubband transitions at normal incidence in Si1-xGex quantum well devices|
|Anno del prodotto:||2007|
|Digital Object Identifier (DOI):||10.1088/0957-4484/18/7/075402|
|Appare nelle tipologie:||1.1 Articolo in rivista|