Two-band structure in photoluminescence spectra from porous silicon and its dependence on excitation wavelength

Abstract

We have systematically measured the room-temperature photoluminescence spectra with a two-band structure from porous silicon (PS), as a function of excitation wavelengths in a wavelength range from 260 to 460 nm. Each spectrum can be fitted by two Gaussian functions centered at about 610 and 700 nm, the intensities of the two bands change with excitation wavelength and the intensity maxima occur when the excitation wavelength is about 340 and 400 nm, respectively. When the excitation wavelength exceeds 420 nm, the band at 610 nm is very weak. The above phenomena can be accounted for in the quantum confinement/luminescence centers model [G. G. Qin and Y. Q. Jia, Solid State Commun. 86, 559 (1993)], where it is supposed that there are two kinds of luminescence centers in SiOx layers covering the nanoscale silicon units in PS.