Physica B 340–342 (2003) 1113–1118 Hot carriers and excitation of Si/SiO x interface defect photoluminescence in Si nanocrystallites T.V. Torchynska a, *, A. Diaz Cano a , M. Morales Rodriguez b , L.Yu. Khomenkova c a ESFM - National Polytechnic Institute, Ed. 9, U.P.A.L.M., Mexico D.F. 07738, Mexico b Department of Mathematics, UPIBI –National Polytechnic Institute, Mexico D.F., Mexico c Institute of Semiconductor Physics at National Academy of Sciences of Ukraine, Kiev 252028, Ukraine Abstract In low-dimensional silicon wires and dots, as supposed earlier (Phys. Rev. B 65 (2002) 115313), hot carrier ballistic transport towards the Si/SiO x interface can enhance the excitation of oxide defect-related photoluminescence (PL) bands. This article presents new experimental results supporting the role of ballistic transport in bright visible photoluminescence of silicon nano-crystallites. The intensity dependences of the ‘‘red’’ and ‘‘orange’’ photolumines- cence bands on excitation light wavelengths, diameters of Si nano-crystallites and surface area of porous layers have been analysed. The models of optical transitions at the excitation of both PL bands are discussed as well. r 2003 Elsevier B.V. All rights reserved. Keywords: Porous silicon; Hot carrier ballistic transport; Photoluminescence 1. Introduction Semiconductor quantum dots (QDs) are basic elements of future nanoelectronics and nanopho- tonics because Si is the most important electronics material. Silicon nanocrystals have attracted great attention after 1990, when very bright emission in the red spectral range (1.6–2.0eV) was discovered in porous silicon (PSi). Up to now the main question concerns whether this emission is an extrinsic or intrinsic property of silicon wires and dots. The popular viewpoint supposes the light emission is the result of a quantum confinement effect [1]. This effect should create the localized states in Si nanocrystallites and enhance the oscillator strength of direct optical transitions. However even recent results [2] of single Si QD photoluminescence (PL) investigation cannot con- firm the quantum confinement PL model. The full- width at half-maximum (FWHM) of PL bands connected with single Si QDs is obtained in the range of 120–210 meV. Note that FWHM of PL bands connected with QD ensemble in direct band gap materials is 20–40meV [3] and for single QDs it is 10–100 meV [4]. Trying to explain the high FWHM value of single QD the authors [2] supposed the phonon assisted PL mechanism in Si nanocrystallites. Recent investigations have shown that visible PL band in PSi has a complex nature and can be represented as the sum of elementary bands peaked in different PSi samples at hn m =1.70–1.85 or ARTICLE IN PRESS *Corresponding author. Tel.: 5257296000x55031; fax: 5257296000x55003. E-mail address: ttorch@esfm.ipn.mx (T.V. Torchynska). 0921-4526/$-see front matter r 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.physb.2003.09.176