Valence and conduction intersubband transitions in SiGe, Ge-rich, quantum wells on [001] Si0.5Ge0.5 substrates: A tight-binding approach

Electronic and optical properties of germanium-rich Si/SiGe quantum wells grown on Si0.5Ge0.5 substrates are investigated by a nearest neighbor tight-binding Hamiltonian. The basis set includes spds(*) orbitals with both spin states. Appropriate scaling laws account for strain effects. We present full electronic band structure calculations both for valence and conduction bands. Confinement effects on the electronic states are considered in detail. Optical spectra related to hole and electron intersubband transitions are derived. Our results for optical absorption due to valence intersubband transitions show excellent agreement with experimental spectra and previous k center dot p calculations. For the same quantum well samples, spectra due to conduction intersubband absorption are provided here. (c) 2006 American Institute of Physics.