Phonon Participation in the Light Emission Process of Porous GeSi Layer

Relaxed Ge_0.5Si_0.5/Si heterostructure was grown by the rapid radiant heating, very low pressure chemical vapor deposition (RRH-VLP/CVD). We report the anomalous temperature dependence of photoluminescence (PL) from porous GeSi layer at 77-300K. The peak-emission energy of PL spectra from porous GeSi layer decreases with increasing temperature while its peak intensity rises, which is quite different from the temperature dependence of porous Si layer. Such dependencies are reversible and independent of temperature-change directions. No obvious 480cm^-1 peak was observed in Raman spectrum, indicating that no substantial amorphous phase contributes the intense light emission from the porous materials. We attribute such anomalous behavior of porous GeSi layer to phonon participation in the light-emission process of porous GeSi layer.