Photovoltaic properties of lead telluride thin film

Abstract

Polycrystalline PbTe thin film is prepared on glass substrate at 200 ~ PbTe thin film is Ntype and the carriers are electrons. The incident energy of photons, 3.4 eV, generates more electron carriers as the distance decreases which give rise to photoelectric current. The density of donors N d was determined to be 1.1 x 102o cm-3 which is consistent with the N:type conduction of PbTe. The activation energies of N-type PbTe thin films are 0.139, 0.139 and 0.126 eV below 60 ~ which change to P-type above 60 ~ This may be due to generation of Pb vacancies in the lattice. The piezoresistivity is measured, the increase of conductivity may be due to displacements of lattice defects under applied stress.Studies on PbTe thin film have shown that it was a direct transition semiconductor with small energy gap of 0.32 eV at 300 K [1] and had a positive temperature coefficient of the gap [2,3] and that PbTe was an extrinsic material in which the carriers were generated by deviation from the stoichiometry, considerable structural information on this material has been obtained. From an engineering point of view PbTe thin films are preferable for applications such as strain gauge, for large piezoresistance effect. Polycrystalline PbTe thin films are prepared on glass substrates by means of evaporation under various conditions of substrate temperature [4]. The transition of conduction type from N-type to P-type occurs in the vicinity of the substrate temperature of 270 ~ This paper reports measurements of I-V characteristic of illuminated thin film and piezoresistance effect.