Photoluminescent n-type porous silicon fabricated in the dark

Abstract

The application of a lateral potential field and the resulting current flow across the sample that is believed to draw electrons away from the silicon substrate's surfaces was investigated. A phosphorous-doped 7ω cm n-type (100) silicon substrate of 500 μm thickness was cut into 5 mm by 20 mm pieces. Ohmic contacts were formed at the sample's two ends using GaIn-eutectic to which copper wires were attached, followed by sealing in epoxy resin leaving only the front face exposed. The samples were rinsed in ethanol for 2 minutes and mounted as working electrodes in a polytetrafluoroethylene cell containing HF and ethanol in a 1:4 ratio. A platinum mesh counter electrode was placed parallel to the specimen at a distance 1 cm above it. It was observed that the lateral potential field and the resulting current flow across the sample draws electrons away from silicon substrate's surfaces, thereby increasing the hole concentration at a greatly accelerated rate.