The "n-like layer" is important in multilayer layer amorphous selenium (a-Se) based Xray
detector structures because it blocks the injection of holes from the positive electrode. The dark current in these devices is controlled primarily by hole injection,and the introduction of the n-like layer to block hole injection was a key development in the commercialization of a-Se X-ray detectors. An n-like a-Se layer is defined as a layer in which the electron range is much greater than the hole range, ¦Ìe¦Óe >> ¦Ìh¦Óh, where ¦Ó and ¦Ì are the lifetime and drift mobility of the charge carriers and the subscript e and h represent electrons and holes.<p>
This thesis examines the effect of doping a-Se with Group II elements (in particular Mg) towards finding a better n-like layer ¨C that with relatively long electron range (drift mobility ¡Á lifetime) , trap limited hole transport and which is stable against crystallization. Conventional Time of Flight (TOF) and Interrupted Field Time of Flight (IFTOF) transient photoconductivity measurements were used to characterize the
electron and hole transport in various Group II doped a-Se layers. The dependence of
the electron and hole lifetimes and drift mobilities on the composition of the n-like layer
was examined. The addition of Group II materials converts the a-Se starting material
from p-like into n-like. It was found that increasing the concentration of Mg increases
the electron range while limiting the hole range by modifying the population of deep
traps. The addition of As further limits the hole transport but does not alter the electron
range. The clear reproducibility of the thermal properties obtained from the Differential
Scanning Calorimetry (DSC) implies that small amounts of Mg can be used as a suitable n-type dopant.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:SSU.etd-08042009-103157 |
| Date | 17 August 2009 |
| Creators | Dash, Isha |
| Contributors | Oguocha, Ikechukwuka, Chen, Li, Teng, Daniel, Kasap, Safa |
| Publisher | University of Saskatchewan |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://library.usask.ca/theses/available/etd-08042009-103157/ |
| Rights | restricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Saskatchewan or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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