Comparing Effects of Vacuum Annealing and Dry Oxidationon the Photoluminescence of Porous Si

Abstract
Effects of vacuum annealing and dry oxidation on the photoluminescence properties of porous Si are reported. Anodized porous Si is formed by electrochemical etching in an aqueous HF solution of 16 to 48 wt% with a current density of 10 to 70 mA/cm2. A subsequent vacuum annealing (from 400°C to 800°C) weakens the intensity of the photoluminescence, whereas, oxidation using dry oxygen at 5 Torr above 800°C increases the intensity remarkably in addition to providing blue shifts as large as 100 nm. This study suggests that the visible photoluminescence is due to the modified quasi-direct band-gap structure of Si by the quantum confinement of electrons and holes.