Electroluminescence microscopy and spectroscopy of silicon nanocrystals inthin SiO2 layers

Stable continuously operable electroluminescent diodes have been fabricated by Sii-ion implantation and annealing of thin SiO2 layers on a silicon sub strate. The external quantum efficiency of the device is reaching 3 x 10(-5 ) for the best diodes. Electroluminescence (EL) emission band is wide and c entered at 800 nm. EL is due to radiative recombination of tunneling carrie rs in Si-nanocrystals(NC) with small contribution of oxide defects (peak at 650 nm). EL images reveal inhomogeneous emission structures on the microme ter scale. Mainly, a small number of bright spots with diffraction limited size (similar to 600 nm) with a homogeneous background are observed and the ir EL spectra measured using an imaging spectrometer with a liquid-nitrogen -cooled CCD camera. The bright EL spots originate from the efficiently exci ted emission of oxide defects and/or emission of a few (possibly single) Si -NC, most likely at places with locally increased current. The low efficien cy is probably a consequence of current tunneling through optically inactiv e nanocrystals or defects in a very thin oxide layer. (C) 2001 Elsevier Sci ence B.V, All rights reserved.