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Comparable study of ZnInO & ZnN as channel layers for transparent transistors

Elias Aperathitis 1Vicky Kambilafka 1Mircea Modreanu 4Roussos Skervelakis 3George Kiriakidis 2,3

1. Microelectronics Research Group, Institute of Electronic Structure and Laser, Foundation for Research and Technology – Hellas, P.O. Box 1527, 71110 Heraklion, Crete, Greece, P.O. Box 1527, Heraklion 71110, Greece
2. University of Crete, Iraclion 71409, Greece
3. Institute of Electronic Structure and Laser, FORTH,, P.O. Box 1527, Vassilika Vouton, Heraklion 71110, Greece
4. University College Cork, Tyndall National Institute (TYNDALL), Lee Maltings, Prospect Row, Cork, Ireland


Fig.1 Source-drain current as a function of

source-drain voltage for gate voltages up to 20V.

ZnO is a wide band gap semiconductor (Eg ~ 3.3eV) with high exciton binding energy (~60 meV), has good transparency and its conductivity approaches that of the widely used n-type indium-tin-oxide (ITO). As a result, ZnO is the ideal material for many applications in the emerging field of transparent electronics and optoelectronics. While achieving p-type ZnO in a controllable, reproducible and reliable manner remains difficult, amorphous ZnO has been used as channel layer in the fabrication of transparent thin film transistors (TTFTs).

ZnO-based TTFTs  have been fabricated with promising results in replacing a-Si TFTs for many transparent applications (flat panel displays, oscillators, flexible electronics, etc).The ZnO-based materials which have been reported as channel layer in these TTFTs are: ZnO, ZnO:N and Zn-M-O where M=In, Ga, Sn.

In this investigation we report on the fabrication of TTFT having ZnN and ZnInO of varying Indium and Oxygen content   as channel and source-drain materials. The gate-bottom TFTs were fabricated on silica substrates, having rf-sputtered ITO as gate and HfO2 or SiO2 as the dielectric. The n-type ZnN channel layer was deposited by rf-sputtering from a zinc nitride target whereas the ZnInO layer was deposited by dc-magnetron sputtering utilizing a metallic ZnIn target in a varying oxygen plasma.

Typical IDS-vs-VDS characteristic of the normally off transistor (after annealing at 410oC in flowing nitrogen) having ZnN channel, HfO2 dielectric and metallic (Ti/Au) source and drain is seen in Fig.1. A direct comparison of the required annealing on the output characteristics of the devices as well as the material transport characteristics will be addressed along with target and processing flow for the TTFT fabrication.


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Related papers

Presentation: Poster at E-MRS Fall Meeting 2008, Symposium B, by Elias Aperathitis
See On-line Journal of E-MRS Fall Meeting 2008

Submitted: 2008-05-12 11:28
Revised:   2009-06-07 00:48