Photoluminescence from ${\mathrm{S}\mathrm{i}/\mathrm{S}\mathrm{i}\mathrm{O}}_2$ single quantum wells by selective excitation

We have studied the photoluminescence (PL) mechanism of crystalline Si single quantum wells sandwiched between ${\mathrm{SiO}}_2$ layers by site-selective excitation spectroscopy. The asymmetric PL spectrum is observed in the red spectral region at low temperatures and can be divided into two PL bands. The peak energy of the strong PL band is almost independent of the well thickness and appears near $\sim 1.65\mathrm{eV}.$ Under selective excitation at energies within the weak PL band, TO-phonon structures are observed in both PL and PL polarization spectra. Steplike TO-phonon structure in the PL spectrum of two-dimensional Si quantum wells is similar to that of zero-dimensional Si nanocrystals. The PL properties of very thin Si quantum wells are discussed.