LIGHT-EMITTING MECHANISM AND PORE-SIZE CONTROL OF POROUS SILICON LAYERS

The mechanism of the light emission from porous silicion layers (PSLs) has been studied. Surface of PSLs modified with thermal oxidation and chemical treatments are analyzed with infrared transmission, Raman scattering, and photoluminescence (PL) measurements. The microscopic structure of PSLs is changed from crystalline phase to an intermediate phase between crystal and amorphous phases, depending on the anodization conditions. Experimental results suggest that the origins for the visible light emission from porous silicon are attributed to both the siloxene compounds and the quantum size effect. The pore size of PSLs is controlled by adjusting HF concentration in the electrolyte solution. It was observed that the reduction of silicon wall thickness leads to the blue shift of PL energy.