Study of TiO2/ITO/ZnO:Al/p-Si photo-sensitive structure based on nanoparticles

By coupling sol-gel and RF sputtering techniques we have been fabricated a photo-sensitive structure: TiO2/ITO/ZnO:Al/p-Si. The electrical conduction shows a thermal assist tunneling process, involving a thermal activation energy about 130 meV. According to thermionic emission, the barrier height was found to increases with the rise of temperature. Such behavior was attributed to the effect of the presence of a Gaussian distribution of barrier heights at the ZnO:Al/p-Si interface. The mean-value of the barrier height (phi(b) = 735 mV) was determined using the modified Richardson plot versus 1/T. This value was in good agreement with the potential barrier height deduced from C-V measurements. The photovoltaic effect was studied in the 80-300 K temperature range. The open-circuit volateg (V-co) was found about 180 mV. The temperature dependence of V-co illustrates the effect of interface states in the V-co-losses. The short-circuit current (J(sc)) is found to be about 2.2 mA/cm(2), which allowed as to present for photo-current sensitive application, instead of photovoltaic application. The temperature dependence of J(sc) shows a negative temperature coefficient about -4.75 A mu A/K. This decrease was attributed to the rise of diffusion and tunnel current through the potential barrier induced by an interfacial oxide layer at the ZnO/p-Si interface.