Photoelectrical properties of amorphous Se25Ge20Te55

This paper reports photoelectrical properties of Se25Ge20Te55 through measu rements of 'transient' and 'steady state' photocurrents. The material displ ayed great sensitivity to optical and thermal stresses. A study of photocon ductivity of Se25Ge20Te55 at different temperatures and at different levels of light intensity reveals that photoconductivity increases exponentially with increase in temperature. Photocurrent (I,,) when plotted against Light intensity (F) follows a power law: I-ph proportional to F-gamma. The expon ent gamma has been found nearly 0.5 suggesting bimolecular recombination. T he decay portion of photocurrent has two components, i.e., a fast component in the beginning followed by a slow decay. The decay time constant tau(d), for the fast decay process increases with increasing temperature indicatin g the existence of deeper traps in the material whereas for slow decay proc ess, it decreases with increasing temperature indicating the presence of ga p states near the mobility edge. (C) 1999 Elsevier Science B.V. All rights reserved.