Comparison of photoluminescence behavior of porous germanium and spark-processed Ge

The photoluminescence (PL) characteristics of spark-processed Ge (sp-Ge) and of anodically etched, porous Ge have been studied at various temperatures. Further, scanning electron micrographs and XPS profiles have been taken. The optical properties of these samples have been found to be guile different from each other. Specifically, two new PL peaks emerge in sp-Ge at low temperatures which are seen at room temperature only as shoulders. Concomitantly, the room temperature PL peak vanishes at low temperatures. A similar observation is not made for porous Ge. Moreover, the PL peak wavelengths in sp-Ge remain constant during cooling whereas a substantial shift of these peak wavelengths occur during cooling for porous Ge. These different observations are attributed to the differences in the structural configurations of the samples. (C) 2000 Elsevier Science B.V. All rights reserved.