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Temperature and doping dependence of the optical absorption in amorphous hydrogenated silicon films
Thin Sohd Films, 89 (1982) 270
270
ELECTRONICS AND OPTICS
T E M P E R A T U R E AND D O P I N G D E P E N D E N C E O F T H E O P T I C A L A B S O R P T I O N IN A M O R P H O U S H Y D R O G E N A T E D SILICON F I L M S * J TARDY AND A. CACHARD
DOparternent de Phystque des' MatOmaux, Untversltb de Lyon 1. Vdleurbanne (France) R. MEAUDRE
Laboratolre de Phy~zque Electrontque, Unt~,ersttOde Lyon I. Vdleurbanne (France)
In this paper we report the temperature dependence of the optical gap Eo of amorphous hydrogenated silicon films. The films were prepared by d.c. sputtering in an Ar-H2 plasma. The gap was investxgated in the temperature range 77-580 K. At low temperatures a saturation-like behavlour is observed. When the temperature is increased we observe two different types of behaviour: in the range 290-460 K Eo decreases linearly with T at the rate 0.35 meV K - 1 ; above 460 K Eodecreases at the rate 1.43 meV K - 1. In the latter temperature range it is seen from the absorption curves that the samples have undergone irreversible changes. Significant loss of hydrogen is very improbable, as deduced from nuclear reaction analysis. Instead we infer some structural modifications such as reordering and/or annealing of voids. We also present the corresponding variations in the refractive index no. Similar experiments were performed on arsenic-doped films. The doping was achieved by ion implantation at doses ranging from 1013 to 1016 ions cm -z with subsequent annealing at 250 °C for 90 min. It is seen that the gap seems rather insensitive to the doping doses. This shows that the incorporation of arsemc atoms results in substitutional doping rather than in the synthesis of an alloy.
* Abstract of a paper presented at the Fifth International Thin F d m s Congress, Herzha-on-Sea, Israel, September 21-25, 1981 0040-6090/82/0000-0000/$02 75
,('~ Elsevier Sequola/Pnnted m The Netherlands
270
ELECTRONICS AND OPTICS
T E M P E R A T U R E AND D O P I N G D E P E N D E N C E O F T H E O P T I C A L A B S O R P T I O N IN A M O R P H O U S H Y D R O G E N A T E D SILICON F I L M S * J TARDY AND A. CACHARD
DOparternent de Phystque des' MatOmaux, Untversltb de Lyon 1. Vdleurbanne (France) R. MEAUDRE
Laboratolre de Phy~zque Electrontque, Unt~,ersttOde Lyon I. Vdleurbanne (France)
In this paper we report the temperature dependence of the optical gap Eo of amorphous hydrogenated silicon films. The films were prepared by d.c. sputtering in an Ar-H2 plasma. The gap was investxgated in the temperature range 77-580 K. At low temperatures a saturation-like behavlour is observed. When the temperature is increased we observe two different types of behaviour: in the range 290-460 K Eo decreases linearly with T at the rate 0.35 meV K - 1 ; above 460 K Eodecreases at the rate 1.43 meV K - 1. In the latter temperature range it is seen from the absorption curves that the samples have undergone irreversible changes. Significant loss of hydrogen is very improbable, as deduced from nuclear reaction analysis. Instead we infer some structural modifications such as reordering and/or annealing of voids. We also present the corresponding variations in the refractive index no. Similar experiments were performed on arsenic-doped films. The doping was achieved by ion implantation at doses ranging from 1013 to 1016 ions cm -z with subsequent annealing at 250 °C for 90 min. It is seen that the gap seems rather insensitive to the doping doses. This shows that the incorporation of arsemc atoms results in substitutional doping rather than in the synthesis of an alloy.
* Abstract of a paper presented at the Fifth International Thin F d m s Congress, Herzha-on-Sea, Israel, September 21-25, 1981 0040-6090/82/0000-0000/$02 75
,('~ Elsevier Sequola/Pnnted m The Netherlands