No abstract

It is well known that the photoconductivity in thin polycrystalline layers of PbTe may be explained by the reduction of the height of intercrystalline barriers under illumination /1, 2/. However, the data presented in this note cannot be explained by means of the barrier model and point to the heterogeneous structure of the sensitized PbTe layer.This note deals with the mechanism of current percolation in the sensitized photosensitive layers of PbTe. Sensitization is achieved by annealing the sample in a vacuum a t residual gas pressure of 5x10 densation on the heated pyroceramic substrate in a vacuum of leads to an increase in photosensitivity and resistivity; new maxima appear in the spectral characteristics. Fig. 1 (curve 1) presents the spectral characteristic of the photosensitivity of an unsensitized layer of PbTe on mica substrate. A maximum of photocurrent is observed at 1 . 0 p m . After sensitization this maximum becomes more pronounced (curve 2 of Fig. l), and a new maximum at 1.5 y m appears. The same figure presents spectral characteristics of the optical density D, obtained by means of the spectrometers Specord M 40 and Specord 61 NIR (curves 1' and 2'). The absorption maximum and the step correspond to photoconductivity maxima at 1.0 and 1.5 pm, respectively, which a r e also obtained for sensitized PbTe layers on pyroceramic substrate.-3 Pa just after layer con- Pa. ItThe temperature dependence of the electrical conductivity in polycrystalline layers of PbTe, manufactured by thermal evaporation on heated pyroceramic substrates in a vacuum of Pa in the temperature range 110 and 300 K is exponential: 6 = Uo exp( -Ei/2 kT) with activation energy Ei = 0.26 eV.The electrical conductivity of sensitized layers in the temperature range between 120 and 270 K is described by Mott' s law b = Go e~p ( T , / T ) l /~ (Fig. 2). The CVCh (current-voltage characteristics) of photocurrent if in the sensitized 1 ) Universiteto 3, Vilnius, USSR.