Drift mobility relaxation in <i>a</i>-Se

Kasap, S. O.; Polischuk, B.; Aiyah, Viswanath; Yannacopoulos, S.

doi:10.1063/1.345592

Cited by 19 publications

(7 citation statements)

References 22 publications

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“…If we were to suddenly reduce the temperature back down to 25°C, we would find a lower mobility and lifetime values than the initial values at 25°C, that is a smaller mobility and shorter lifetime for both electrons and holes. Both would slowly recover through structural relaxation processes along the lines we reported and discussed previously [14,16].…”

Section: Resultsmentioning

confidence: 84%

Temperature dependence of charge carrier ranges in stabilized a-Se photoconductors

FogalBud

KasapSafa

2014

Can. J. Phys.

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Using time-of-flight (TOF) and interrupted-field TOF we have measured the electron and hole drift mobilities, e and h , lifetimes, e and h , and hence carrier ranges, e e and h h , in stabilized a-Se as a function of temperature from −25 to 45°C. Above room temperature, e e and h h show a slight increase with temperature and peak around 31 and 35°C, respectively. The e e at 35°C and h h at 40°C are approximately the same as room temperature values. Below room temperature, down to −25°C, both e and h decrease with decreasing temperature with activation energies E e and E h that are 0.38 and 0.21 eV. The electron and hole lifetimes, e and h , are also thermally activated but they increase with decreasing temperature with activation energies E e and E h that are 0.31 and 0.18 eV. These are quite close to corresponding activation energies for the drift mobilities within experimental errors. The electron and hole ranges, e e and h h , therefore exhibit only a weak temperature dependence, both increase slightly with temperature. These observations are consistent with shallow trap controlled transport in the presence of a set of deep traps. The X-ray sensitivity of a photoconductor, among other factors, depends on the charge collection efficiency, which depends on electron and hole ranges, e e and h h . Because these carrier ranges do not show any significant temperature dependence, one can conclude that the X-ray sensitivity of stabilized a-Se over the temperature range from −25 to 40°C should not be affected by changes in the collection efficiency. Résumé: En utilisant des techniques de temps de vol (TOF), non et interrompu, nous mesurons les mobilités de dérive des électrons et des trous, e et h , les temps de vie, e et h , et donc la portée des porteurs de charge, e e et h h , dans du a-Se stabilisé en fonction de la température, de −25 à 45°C. Au dessus de la température de la salle, e e et h h augmentent légèrement avec la température avec un maximum à 31 et 35°C respectivement. On voit que e e à 35°C et h h à 40°C ont même valeur qu'à la température de la salle. Sous la température de la salle jusqu'à −25°C, à la fois e et h diminuent avec la température, avec des énergies d'activation E e ϭ 0.38 eV et E h ϭ 0.21 eV. Par contre, les temps de vie e et h croissent avec une baisse de la température, avec des énergies d'activation E e = 0.31 eV et E h = 0.18 eV. Aux erreurs de mesure près, ces énergies sont proches de celles pour la mobilité. Il s'ensuit que les portées e e et h h n'ont qu'une faible dépendance en température, les deux augmentant légèrement avec la température. Ces résultats sont cohérents avec ceux obtenus par transport contrôlé par pièges peu profonds en présence de pièges profonds. La sensibilité X d'un photoconducteur, parmi d'autres facteurs, dépend de l'efficacité à collecter des charges, qui, elle, dépend des portées e e et h h . Puisque ces portées ne montrent pas de dépendance significative en température, nous pouvons conclure que la sensibilité X du a-Se stabilisé ne devrait pas être affec...

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Section: Resultsmentioning

confidence: 84%

Temperature dependence of charge carrier ranges in stabilized a-Se photoconductors

FogalBud

KasapSafa

2014

Can. J. Phys.

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“…͓DOI: 10.1063/1.2930680͔ Structural relaxation ͑SR͒ is an atomic-level rearrangement observed in most amorphous materials below the crystallization temperature. SR can have an impact on optical, 1 mechanical, 2 and electronic transport properties, [3][4][5][6] and has been reported for metallic glasses, 7 amorphous semiconductors, such as Si, 8 Ge, 9 and chalcogenide glasses used in electronic nonvolatile memories based on phase change. 5,6 In the latter case, the resistance of the amorphous phase, which is used to designate the logic state of the memory, drifts with time as a result of SR. 5,6 Thus, SR can heavily impact the reliability of solid-state phase-change memory devices.…”

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confidence: 98%

“…The R increase is faster for increasing temperature, confirming that SR is a temperature-accelerated process. 3,8,15 The average transition time , describing a single defect annihilation event, can thus be given by the Arrhenius law,…”

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confidence: 99%

Temperature acceleration of structural relaxation in amorphous Ge2Sb2Te5

Ielmini

Lavizzari

Sharma

et al. 2008

Applied Physics Letters

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The structural relaxation (SR) process in an amorphous chalcogenide material (Ge2Sb2Te5) is studied by electrical measurements on phase-change memory devices. SR induces a change in the conduction regime from Poole to Poole–Frenkel transport, evidencing a temperature accelerated defect-annihilation process. Based on an Arrhenius kinetics with distributed activation energies, a temperature-acceleration law is shown, relating the time to reach a specific relaxed state to the temperature during isothermal experiments. This law is demonstrated comparing the time evolution of resistance for different temperatures. These results allow for a significant time reduction in reliability testing of devices and materials affected by SR.

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“…Amorphous selenium films of thickness 5&70 pm were prepared by evaporation of vitreous selenium pellets from an open Mo boat on to pre-oxidized aluminium substrates using conventional vacuum-deposition techniques as described previously (Kasap, Polischuk, Viswanath Aiyah and Yannacopoulos 1990). A number of a-Se films were prepared from different batches of selenium using different substrate temperatures to obtain variations in the hole lifetime (Berkes 1974).…”

Section: $2 Experimental Proceduresmentioning

confidence: 99%