PHOTOLUMINESCENCE AND RAMAN-STUDY OF POROUS SIGE

The photoluminescence bands in the visible and in the infrared of poro us Sice layers with initial Ge contents of 5% and 20%, prepared by ano dical etching, are investigated at different temperatures. At room tem perature the photoluminescence spectra are dominated by an intense red photoluminescence band centered at 1.8 eV. A weaker blue photolumines cence band is also observed which becomes more important at low temper atures. Raman measurements indicate only a low degree of confinement i n our porous SiGe layers. The occurrence of blue-green luminescence se ems to originate from the oxygen inclusions in the crystalline porous structure. Infrared photoluminescence spectroscopy on the porous layer shows that the broad infrared band known from porous Si is missing in the porous SiGe layers, but transitions via defects in the crystallin e structure of the porous layers are observed. (C) 1996 American Insti tute of Physics.