Transport properties of TCO-coated macroporous silicon structures

F. GARCES; L.N. ACQUAROLI; R. URTEAGA; A. DUSSAN; R.R. KOROPECKI; R. ARCE

La Plata, Buenos Aires

Conferencia; HK2010 Humboldt Kolleg-International Conference on Physics; 2011

In this work we present the electrical and photonic characterization of a semiconductor (Silicon Porous)/TCO (Transparent Conductor Oxide) junction obtained by the deposition of SnO2 and ZnO onto porous silicon, using the Sol-Gel technique. The porous silicon was prepared by the electrochemical anodization of a silicon wafer. The anodization conditions were chosen so as to produce a macroporous system, with pore size ranging in 0.8 to 1 m diameter. The transport of charge carriers through the interface was studied from measurements of current-voltage curves in dark and under illumination.. The SnO2 was doped with fluorine, and the ZnO was doped with aluminium. We analyzed the effects of the dopant concentration on the electrical properties of the junction. By fitting the J-V characteristic we evaluated the series resistence, ideality factor, reverse saturation current and photogenerated current. The values obtained for the ideality factor are quite high, between 9 and 20. This behavior can be attributed to formation of thin layer of SiO2 at interface TCO/Silicon porous. The results were analysed in relation with the structural properties of the grown films, such as lattice parameter and the crystallite size obtained by X-ray diffraction. Additionally, the light emission of porous silicon/TCO heterojunction was measured under the passage of electrical current for different applied voltages. The measured signal was collected by a photodiode as a function of time. The light intensity increases with increasing applied voltage, following a trend similar to that observed for the current in the J-V curves. This phenomenon, known as electroluminescence, has been rarely observed in macroporous silicon.