PHOTO-ASSISTED CONTINUOUS TUNING OF PHOTOLUMINESCENCE SPECTRA OF POROUS SILICON

The continuous shift in photoluminescence (PL) spectra of porous silic on (PS) has been analysed for the samples whose PL peak wavelengths ar e photo-assistedly tuned from red to blue. The PS layers are formed by anodizing p-type (100) Si wafers in an ethanoic HF solution in the da rk. The PL peak energy is controlled by in-situ post-anodization illum ination by a tungsten lamp. The evolution of PL spectra with increasin g the illumination time is studied in relation to that of PL excitatio n spectra, polarization memory, and surface chemical composition. The experimental results indicate that the green and blue PL spectra are a ttained only by photochemical etching without the growth of the surfac e oxide, and that the PL emission from PS is based on the oxide-free m echanism even in the blue band. (C) 1997 Elsevier Science S.A.