Luminescence of silicon thin film and SiGe multiple quantum wells realizedon SOI

We have investigated photoluminescence (PL) of crystalline silicon-based la yers sandwiched between SiO2 barriers. We fabricate these structures on sta ndard silicon on insulator (SOI) wafers realized by bonding techniques. Fir stly, we realize silicon thin layers (50-200 nm) by thermal oxidation of th e SOI free surfaces. At low temperature and under W excitation, luminescenc e spectra is dominated by electron-hole droplet (EHD) or electron-hole plas ma (EHP) recombination. We show that the behavior of the condensed phase is strongly modified by the spatial confinement of the carriers. Secondly, we grow by CVD Si/Si1-xGex (x approximate to 20%) multiple quantum wells (MQW ) on SOI wafers. All the samples are capped by thermal SiO2 layers. The mai n result is that luminescence from these samples is still observed up to ro om temperature; in comparison, the quenching temperature for similar Si/Si1 -xGex MQW directly grown on silicon substrates is 150 K. This result is due to the presence of the buried SiO2 layer that avoids the thermal transfer of carriers from SiGe wells to the silicon substrate. (C) 2001 Elsevier Sci ence B.V. All rights reserved.