Time-resolved decay of the blue emission in porous silicon

Abstract

The technologically interesting blue emission from porous silicon has been studied using time-resolved photoluminescence. In as-etched samples prepared using the standard electrochemical method, the decay time is shown to be extremely fast (τ=0.86 ns). This decay time remains unchanged from room temperature down to 77 K. The porous material giving the blue emission is unstable and degrades rapidly under UV photoexcitation. A corresponding increase in red intensity with decreasing blue intensity is observed, demonstrating a correlation between the two types of emission. Under ambient light conditions at room temperature the material is more stable and remains emissive for a number of days.