Two-peak photoluminescence and light-emitting mechanism of porous silicon

A two-peak photoluminescence (PL) spectrum of ${\mathit{p}}^{\mathrm{-}}$-type porous silicon (PS) has been observed in atmospheric stored samples. According to different spectral characteristics, especially linewidth, and different effects induced by storage and illumination of samples, the low- and high-energy peaks are identified as due to emission caused by quantum confinement effects of remnant Si walls of PS and siloxene and/or ${\mathrm{SiO}}_2$ on PS surfaces, respectively. A light-emitting mechanism accounting for the two-peak PL spectrum is discussed.