Trapping Processes in Amorphous Selenium

Blakney, R. M.; Grünwald, H.

doi:10.1103/physrev.159.664

Cited by 27 publications

(8 citation statements)

References 9 publications

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“…While the drift mobility decreases exponentially with decreasing temperature, the lifetime increases exponentially. This may seem unusual, but it is exactly what would be expected in the case of shallow trap controlled transport and a set of deep traps [19]. Notice that the activation energies for the lifetime are not too different than those corresponding activation energies for the drift mobility.…”

Section: Resultsmentioning

confidence: 78%

“…The thermally activated behavior in the drift mobility and the lifetime arise from the temperature dependence of , or r , inasmuch as carrier release is thermally activated; probability of release per unit time is o Ϫ1 exp(−E t /kT) where o is a phonon (an attempt to escape) frequency and E t is the energy depth of the traps from the transport band edge. The measured drift mobility from TOF and the lifetime from IFTOF are given by [19] = o and = o / so that…”

Section: Resultsmentioning

confidence: 99%

“…In simple terms, the effect of the shallow traps can be incorporated into a mobility reduction factor, , which for a discrete set of shallow traps is given by [19] ϭ c…”

Section: Resultsmentioning

confidence: 99%

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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: 78%

Section: Resultsmentioning

confidence: 99%

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

FogalBud

KasapSafa

2014

Can. J. Phys.

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“…This gives Because exp(-r/T1), exp(-t/T2), and exp(-emt) are linearly independent, we have c=o (14) where r = l / r l or 1/r2. Rearranging eq 15 we have r 2 -( 1 / r + N t C , + e , , ) r + ( e , / r ) = O (16) The solutions of eq 16 are…”

Section: (3)mentioning

confidence: 98%

“…The latter two factors are denoted by em, so that the generation rate is given by = Vt where r = 1/tj or l/r2. Rearranging eq 15 we have r2-(\/r + NtCllt + ejr + (em/r) = 0 (16) The solutions of eq 16 are r±=l/2[(l/T + NtCnt + em)± ((l/T + ^Cm + em)2-4em/r)'/2] (17) Choosing two linearly independent solutions we have r, = l/r+and r2 = l/r_ (18) and…”

Section: The Photoconductivity Modelmentioning

confidence: 99%

A study of the recombination processes of photogenerated charge carriers in tin dioxide/ion exchange polymer-zinc meso-tetraphenylporphyrin/gold cells

Huang¹,

Ioannidis²,

Lawrence³

1993

J. Phys. Chem.

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Theoretical approaches to the description of charge carrier recombination in insulators and semiconductors containing traps have been used to interpret photoconductive decay curves observed after illumination of SnO2/ ZnTPP-polyXIO/Au cells. Application of the double exponential solution derived from a simplified photoconductivity model accurately reproduces the decays and points to the involvement of both shallow and deep traps in the overall recombination process, which is consistent with experimental results presented in a previous report. From this approach, relevant parameters such as the relative rates of trapping, detrapping, and recombination for photogenerated charge carriers are estimated. However, the relatively large detrapping rate that this model yields for the deep traps involved outlines its limitation in describing recombination processes in systems of this type. A further analysis of these results, basedon a model for bimolecular trapping/annihilation processes where deep traps act solely as recombination centers, helps demonstrate how a single decay can be composed of two distinct recombination mechanisms, in agreement with previously reported data. During about the first 15 s of the decay, bimolecular recombination occurs mainly between charge carriers residing in shallow traps, also referred to as "free" carriers. At longer times, the bimolecular recombination becomes mediated by the deeper traps present in the system. The expression derived from the bimolecular/trapping annihilation model for the decay at longer times, which is arrived at by effectively turning off the free carrier recombination, is equivalent to the expression one gets for a process that is of a unimolecular type.

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Time‐of‐Flight Transient Photoconductivity Technique

Kasap

2022

Photoconductivity and Photoconductive Materials

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Trapping Processes in Amorphous Selenium

Cited by 27 publications

References 9 publications

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

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

A study of the recombination processes of photogenerated charge carriers in tin dioxide/ion exchange polymer-zinc meso-tetraphenylporphyrin/gold cells

Time‐of‐Flight Transient Photoconductivity Technique

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