High-field conduction in some chalcogenide glasses

Current voltage (I-V) characteristics have been studied at various temperat ures in amorphous thin films of Ge22Se78-xBix and GexSe80-xTe20 where 0 les s than or equal to x less than or equal to 10. At low electric fields, ohmi c behaviour is observed. However, at high electric fields (E similar to 10( 4) V cm(-1)) the current becomes superohmic, Analysis of the data shows the existence of space charge-limited current (SCLC) in a-Ge22Se78-xBix in whi ch In (I/V) vs V curves are found to be straight lines with decreasing slop es at high temperatures, in accordance with the theory of SCLC for a unifor m distribution of traps. However, in the case of a-GexSe80-xTe20,, no SCLC is observed. Instead, In I vs V-1/2 curves are found to be straight lines w ith decreasing slopes at high temperatures. A more detailed analysis shows that the mechanism of conduction is of Poole-Frenkel type in this system. C opyright (C) 2000 John Wiley & Sons, Ltd.