Luminescence of silicon thin film and SiGe multiple quantum wells realized on SOI

Abstract We have investigated photoluminescence (PL) of crystalline silicon-based layers sandwiched between SiO 2 barriers. We fabricate these structures on standard silicon on insulator (SOI) wafers realized by bonding techniques. Firstly, we realize silicon thin layers (50–200 nm) by thermal oxidation of the SOI free surfaces. At low temperature and under UV excitation, luminescence spectra is dominated by electron–hole droplet (EHD) or electron–hole plasma (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 / Si 1−x Ge x (x≈20%) multiple quantum wells (MQW) on SOI wafers. All the samples are capped by thermal SiO 2 layers. The main result is that luminescence from these samples is still observed up to room temperature; in comparison, the quenching temperature for similar Si/Si 1− x Ge x MQW directly grown on silicon substrates is 150 K. This result is due to the presence of the buried SiO 2 layer that avoids the thermal transfer of carriers from SiGe wells to the silicon substrate.