Highly stable amorphous zinc tin oxynitride thin film transistors under positive bias stress
Publication Date
2017-09-18Journal Title
Applied Physics Letters
ISSN
0003-6951
Publisher
AIP
Volume
111
Issue
12
Type
Article
This Version
AM
Metadata
Show full item recordCitation
Niang, K., Bayer, B., Meyer, J., & Flewitt, A. (2017). Highly stable amorphous zinc tin oxynitride thin film transistors under positive bias stress. Applied Physics Letters, 111 (12)https://doi.org/10.1063/1.5004514
Abstract
The stability of amorphous zinc tin oxynitride thin film transistors (a-ZTON TFTs) under
positive bias stress (PBS) is investigated. Thin films are deposited by remote plasma reactive
sputtering and are annealed at 300 °C in air for 1 hour, after which films are confirmed to be
highly amorphous by transmission electron microscopy. Typical a-ZTON TFTs exhibit a
threshold voltage of 2.5 V, a field effect mobility of 3.3 cm2 V
–1 s
–1
, a sub-threshold slope of
0.55 V dec–1 and a switching ratio over 106
. Using a thermalization energy analysis, the
threshold voltage shift under PBS is analysed. A maximum energy barrier to defect
conversion up to 0.91 eV is found, which is significantly greater than that the ~ 0.75 eV
energy barrier for amorphous indium gallium zinc oxide (a-IGZO) and amorphous zinc tin
oxide (a-ZTO) TFTs previously reported. The improved stability of these oxynitride TFTs
over amorphous oxide TFTs is explained by the elimination of less stable oxygen vacancies
due to the passivation of oxygen vacancies with nitrogen. The higher attempt-to-escape
frequency of 108
to 109
s
–1
in a-ZTON TFTs compared with 107
s
–1
in amorphous oxide
semiconductor TFTs, on the other hand, is attributed to the high homogeneity of the
amorphous film leading to strong carrier localization in the band tails.
Sponsorship
EPSRC (EP/M013650/1)
Identifiers
External DOI: https://doi.org/10.1063/1.5004514
This record's URL: https://www.repository.cam.ac.uk/handle/1810/274854
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