Anomalous temperature dependencies of photoluminescence for visible-light-emitting porous Si

Porous Si has been prepared by the electrochemical anodization method. At room temperature it has a light-emission peak energy in the range of 1.50–2.06 eV. The results from variable-temperature photoluminescence (PL) show anomalous temperature dependencies of the spectral characteristics: the emission intensity increases with decreasing temperature until reaching an intensity maximum at about 100–200 K, then it decreases at lower temperatures; the emission energy shift with temperature has no fixed trend and varies with sampling point. Such dependencies are reversible with the two directions of temperature change. The above observations can be explained by phonon participation in the light-emission process of porous Si.