The Effects of illumination on electrical performance of ZnO
thin film transistors
S. Ruzgar1*, M. Caglar1, Y. Caglar1, S. Ilican1
1Department
of Physics, Faculty of Science, Anadolu University, Eskisehir, Turkey
*Corresponding author: serifruzgar@anadolu.edu.tr
Abstract Summary: In this study, the
nanostructured ZnO thin film transistors
(TFTs) were fabricated by using sol–gel
spin-coating method. Electrical properties
of the ZnO TFT under dark and various
illumination intensities were investigated.
The mobility values of the ZnO-TFT were
obtained to be 0.53 cm2/Vs and 0.9
cm2/Vs under dark and 100 mWatt/cm2
illumination, respectively.
space communications, flame detection
and ozone layer monitoring [4].
The response of ZnO-TFT to positive
gate voltage shows the existence of ntype active layer. The maximum value of
the drain current was observed at 100
mWatt/cm2 light intensity. These results
show us that the ZnO TFT can be used in
device modification for photodiode or
phototransistor.
For preparation of ZnO TFTs sol-gel spin
coating method was used. As a starting
material, 0.05 M zinc acetate dihydrate
[Zn(CH3COO)2•2H2O, ZnAc], as a solvent
and stabilizer 2-Methoxyethanol (C3H8O2)
and monoethanolamine (C2H7NO, MEA)
were used respectively. The molar ratio of
MEA/ZnAc was set at one to one. To
obtain clear and homogeneous solution,
this solution was stirred at 60 °C for 2 h.
Then, a liquid film was deposited on the
100 nm SiO2 layer (University wafer,
USA) by spin coater with a spin speed of
3000 rpm for 30s in the room
temperature. After each coating, ZnO
films were placed in an oven for 10
minutes at 300°C. After four coatings,
ZnO films were annealed for 2h at 750°C.
Following the coating of the ZnO films,
aluminum source and drain electrodes
with thickness 100nm were evaporated.
The channel width and length of the
transistor are 1000 µm and 50 µm,
respectively. And then silver paste was
used for the gate contact. The schematic
structure of ZnO TFT is given in Fig. 1.
Introduction:
Metal oxide semiconductor materials may
be the best candidates compared with
hydrogenated
poly-Si and organic
semiconductors counterparts in this
rapidly developing thin film transistor
application.
Among metal oxide semiconductors, Zinc
oxide (ZnO) has been extensively studied
because of its characteristic properties
such as a high direct band gap of ZnO
(3.3eV) inspires to transparent electronic
application [1] and large exciton binding
energy of 60 meV. The solutionprocessed semiconductors fabrication
has some advantage such as low-cost,
easy technology. Also, the sol–gel
method allows low temperature device
manufacturing [2]. ZnO TFTs have
recently studied intensively for its
ultraviolet detecting and high responsivity
properties [3]. ZnO-phototransistor can be
used at some technological area such as
In this study, we fabricated the solutionbased nanostructured ZnO-TFT with
bottom-gate top-contact architecture. The
effects of illumination on electrical
performance
of
ZnO-TFT
were
investigated.
Experimental:
Acknowledgement:
This work was supported by Anadolu University
Commission of Scientific Research Project under
Grant No. 1101F009 and under Grant
No.1501F030.
References
G. Cramer, “Fabrication and Comparison of
ZnO Thin Film Transistors with Various Gate
Insulators,” ELECTRONICS, Nnin. Reu.
2006, Research Accomplishments
[2] K.J. Chen, F.Y. Hung, S.J. Chang, S.J.
Young, ‘’Optoelectronic characteristics of UV
photodetector based on ZnO nanowire thin
films’’, J Alloys Compd, 479 (2009), p. 674
[3] H.S. Bae, M.H. Yoon, J.H. Kim, S. Im,
‘’Photodetecting properties of ZnO based thinfilm transistors’’ Appl. Phys. Lett., 83 (2003),
p. 5313
[4] W. Y. Weng, S. J. Chang, C. L. Hsu, and T. J.
Hsueh,’’ A ZnO-Nanowire Phototransistor
Prepared on Glass Substrates’’, ACS Appl.
Mater. Interfaces, 3 (2011), p.162–166
[1]
Fig. 1. Schematic structure of ZnO TFT.
Fig. 2. Plots of Id vs. Vd of the ZnO TFT
under various illuminations at Vg=0V.