Abstract
In2-2xAl2xS3-3yO3y alloys have been prepared on Pyrex(TM) glass substrates by the spray pyrolysis technique. The shape of the photoconductivity spectrums I-ph (hnu) and the variations I-ph (f ) and I-ph (V) allow us to understand the conduction mechanism and the photocarriers' recombination. For low compositions (xless than or equal to0.2), I-ph(V) parabolic variation shows that this conduction is limited by the space charge zone in accordance with Child's law (I(ph)proportional toV(2)) [N. F. Mott and R. W. Gurney, Electronics Processes in Ionic Crystals (Oxford, New York, 1940), p. 463]. The exploitation of such variation shows that the density of the trap centers increases with the composition. For xgreater than or equal to0.4, the electrical conduction instead follows Ohm's law. In the same way, the analysis of an extension of Devore's model [Phys. Rev. 102, 86 (1956)] as (I(ph)hnu)(2) versus photon energy hnu shows an increase of the band gap energy E-g according to a parabolic profile. On the other hand, for low compositions (x=0,0.05,0.1,0.2), the conductivity study as a function of the temperature presents a deviation to Arrhenius's law in the intermediate temperature domain ranging from 80 to 330 K. Moreover, in this domain, the study of the activation energy E-a(T) according to Werner's model [Solid State Phenom. 37, 214 (1994)] supposing potential fluctuations at the grain boundaries yields the values of the barrier high phi(b) and the standard deviation sigma(phi). From these results, we see that E-g increased versus x and that the electrical properties are essentially preserved for low aluminum concentration films. This may be due to a minor presence of an Al2O3 phase for such deposits. (C) 2002 American Institute of Physics.