Photoelectrical properties of amorphous Se Ge Te 25 20 55

This paper reports photoelectrical properties of Se25Ge20Te55 through measurements of ‘transient’ and ‘steady state’ photocurrents. The material displayed great sensitivity to optical and thermal stresses. A study of photoconductivity of Se25Ge20Te55 at different temperatures and at different levels of light intensity reveals that photoconductivity increases exponentially with increase in temperature. Photocurrent Iph.when plotted against light intensity F.follows a power law: IphAFg. The exponent g has been found nearly 0.5 suggesting bimolecular recombination. The decay portion of photocurrent has two components, i.e., a fast component in the beginning followed by a slow decay. The decay time constant td for the fast decay process increases with increasing temperature indicating the existence of deeper traps in the material whereas for slow decay process, it decreases with increasing temperature indicating the presence of gap states near the mobility edge. q1999 Elsevier Science B.V. All rights reserved.