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GeSi nanostructured films were obtained by cosputtering from two Ge and Si targets and subsequent annealing in furnace in N2 for 5 h at 700, 800 and 900 °C, with the aim to show the correlation between electrical properties and crystalline structure of the films. The as-deposited films are amorphous, have a Ge:Si composition of 55:45 and 185 nm thickness. The film structure was investigated by XRD and TEM, and the electrical behaviour was studied by measuring current–voltage (I–V) and current–temperature (I–T) characteristics and by discussing them in correlation with the structure. Different electrical behaviours of GeSi films corresponding to different structures have been evidenced. The 700 °C annealed GeSi films are formed of nanocrystals (7–15 nm) separated by amorphous regions (1–2 nm). These films present a superlinear I–V characteristic typical of high field-assisted tunnelling through potential barriers (amorphous regions) between nanocrystals. The I–T characteristic at low temperature follows a T−1/2 law showing a thermally activated tunnelling of carriers between neighboring GeSi nanocrystals. The films annealed at 800 and 900 °C have a like behavior, they are completely crystallized and present linear I–V and Arrhenius I–T dependences reflecting the polycrystalline behaviour.

Measurements of the visible photoluminescence and the decay of the photoluminescence, performed at different temperatures on porous silicon films, prepared by the anodization process under different conditions on (100) p-type silicon wafers are reported. A separation of the broad visible band of the photoluminescence in two subbands with maxima situated at 1.54 and 1.72eV at room temperature related to the preparation conditions is obtained. This separation is still present at low temperatures but is very weak. The PL decay process is well described by a bimolecular recombination. The decay time α−1 is in the order of microseconds at room temperature and nanoseconds at liquid nitrogen temperature. Nous presentons des nouveaux resultats concernants la variation de la luminescence de couches minces de silicium poroeux en fonction de la temperature et les conditions de preparation. Deux bandes d'emission sont identifiees a 1,54 et 1,72 eV. L'analyse du declin de cette luminescence indique l'existence d'un processus bimoleculaire de recombination radiative, caracterisee par une constant de temps de l'ordre microsecondes a la temperature ambiante et nanosecondes a la temperature d'azote liquide.