INVESTIGATION OF LUMINESCENCE IN STRAINED SIGE/SI MODULATED QUANTUM-WELL AND WIRE STRUCTURES

Luminescence properties associated with strain-induced band modification in SiGe/Si heterostructures such as quantum wells (QWS) and quantum wires (QWRS) are reviewed. Among several issues concerning formation of highly luminescent SiGe materials, surface segregation is shown to be the main cause of deteriorating interface integrity. To resolve the problem, a new technique called segregant-assisted growth (SAG) is proposed. SAG and gas-source MBE (GSMBE), which is considered to be quasi-SAG, are shown to provide high-quality SiGe/Si heterostructures with abrupt interfaces. Highly efficient band edge emissions are observed in not only type-1 but also spatially indirect type-2 QWS. The energy shift in QWS is discussed based upon the band modification due to surface segregation during growth. The ratio between the no-phonon (NP) peak and its phonon replica (TO) in the edge emission reflects the nature of the QWS formed with alloy materials. The coupling of QWS and evolution of superlattices are well understood based on the effective-mass approximation by precisely taking into account the band alignment. QWRS are well fabricated on V-groove patterned substrates and luminescent properties very different from those of QWS are observed. These findings indicate the high potential of SiGe/Si heterostructures, not only in scientific areas but also in device applications.