THE ROLE OF A THIN AMORPHOUS-SILICON LAYER IN THE FABRICATION OF MICRO-PORED SILICON

Micro-pored silicon formed by electrochemical anodization of a p-type (100) Si wafer with a thin amorphous Si (a-Si) layer showed green colo red photoluminescence (PL) at room temperature. The a-Si thin films we re deposited on an Si(100) wafer by rf magnetron sputtering. The wafer s with and without a-Si layer were electrochemically anodized and anne aled by a rapid thermal process at 800 degrees C for 10 min. A strong green PL signal peaked at 543 nm appeared in the samples fabricated wi th a-Si thin film, while normally processed porous Si samples showed o nly a typical PL signal at 681 nm. From scanning electron microscopy, Auger electron spectroscopy, and Fourier transformed infra-red spectro scopy, it is suggested that the a-Si layer has the role of a mesh for the smooth and fine Si porosity which prevents oxidation during the an odization of the Si substrate.