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Young-Joon Han,Yong-Jin Choi,In-Tak Cho,Sung Hun Jin,Jong-Ho Lee,Hyuck-In Kwon IEEE 2014 IEEE electron device letters Vol.35 No.12
<P>We investigate the effects of ambient atmosphere on the electrical performance of p-type tin monoxide (SnO) thin-film transistors (TFTs), and present the effective method for the passivation of SnO TFTs using a SU-8 organic layer. The experimental data shows that the SnO TFTs without a passivation layer suffer from the electrical performance degradation under humid environments, which implies that the formation of the passivation layer is necessary in p-type SnO TFTs for the stable operation of the devices. The SU-8 organic layer was successfully incorporated as a passivation layer of SnO TFTs. The SnO TFTs with a SU-8 passivation layer exhibit very similar transfer characteristics with those without a passivation layer, and show much improved long-term durability and bias stress stability compared with the SnO TFTs without a passivation layer under air environments.</P>
Chae-Eun Oh,Hwan-Seok Jeong,Su-Hyeon Lee,Dong-Ho Lee,Yeong-Gil Kim,Myeong-Ho Kim,Kyoung Seok Son,Jun Hyung Lim,Sang-Hun Song,Hyuck-In Kwon 대한전자공학회 2023 Journal of semiconductor technology and science Vol.23 No.1
We study the effects of oxygen content in indium-gallium-zinc oxide (IGZO) thin films on the output characteristics of IGZO thin-film transistors (TFTs) under high current driving conditions. Output curves were characterized at a high gate-to-source voltage (= 40 V) from both oxygen-rich and oxygen-poor IGZO TFTs. Characterization results showed that the drain current (ID) decreased with an increase in the drain-to-source voltage (VDS) under high-VDS conditions in the oxygen-rich IGZO TFTs, but abruptly increased with VDS in the oxygen-poor IGZO TFTs. From the detailed analysis of the transfer and capacitance-voltage curves obtained after output curve characterization by varying the VDS sweep range, the abnormal behavior of the output curves was mainly attributed to the increased number of trapped electrons within the gate dielectric and that of the doubly ionized oxygen vacancies in IGZO during the output curve characterization at high VDSs in oxygen-rich and oxygen-poor IGZO TFTs, respectively. The abnormality of the output curve was more significant in a wider channel device in both TFTs, which was attributed to the increased device temperature due to the self-heating effects.
Ching-Lin Fan,Yi-Yan Lin,Yan-Hang Yang 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.61 No.8
This study presents a combined scheme of rapid thermal annealing (RTA) and multi-channel structure for improving the performance of polycrystalline silicon (poly-Si) thin film transistors (TFTs). Results show that RTA treatment can improve device performance by decreasing the number of in-grain defects and improving the quality of the gate oxide. The multi-channel structure improves the electrical characteristics of the poly-Si TFTs by decreasing the number of grainboundary defects. Thus, the combined scheme can effectively reduce defect states and improve the gate-oxide’s quality simultaneously, resulting in a significant improvement in the performance of poly-Si TFTs. In addition, the performance improvement is particularly apparent for the TFTs with a thinner gate oxide and smaller channel length. Therefore, the proposed scheme is a good candidate for improving the electrical characteristics of TFTs for use in small-to-medium size displays.
Highly Robust Flexible Oxide Thin-Film Transistors by Bulk Accumulation
Xiuling Li,Billah, Mohammad Masum,Mativenga, Mallory,Di Geng,Yong-Hwan Kim,Tae-Woong Kim,Young-Gug Seol,Jin Jang IEEE 2015 IEEE electron device letters Vol.36 No.8
<P>We report the achievement of flexible oxide thin-film transistors (TFTs) that are highly robust under mechanical bending stress. Fabricated on solution-processed polyimide, the oxide TFTs employ the dual-gate structure with an amorphous-indium-gallium-zinc oxide (a-IGZO) semiconductor, silicon dioxide gate insulators, and molybdenum gate and source/drain electrodes. High mechanical stability is achieved by shorting the two gates together to induce bulk accumulation (BA)-a condition in which the channel accumulation layer of electrons extends the entire depth of the active layer. It is shown experimentally that the BA a-IGZO TFTs exhibit better stability under bending stress compared with single gate-driven TFTs. From TCAD simulations, the immunity to slight variations in carrier concentration under tensile strain is found to be a result of the high gate-drive intrinsic of the BA TFTs.</P>
Kim, D.,Lee, D.,Yoon, S.,Jang, J.,Hong, M. Elsevier 2012 Current Applied Physics Vol.12 No.suppl4
This paper presents a low temperature fabrication of amorphous IGZO TFTs (a-IGZO TFTs) via high density CVD and superimposed rf/dc magnetron sputtering below 150 <SUP>o</SUP>C Low temperature processed SiO<SUB>x</SUB> films were been prepared in high density plasma chemical vapor deposition with inductively-coupled plasma (ICP) source and their electrical properties of these films have been investigated as a function of an ICP power and an O<SUB>2</SUB> flow rate. Also, we found that a-IGZO semiconductor could be affected by a dc self-bias of a target surface using a superimposed rf/dc magnetron sputtering. Increasing a dc self-bias, higher post-annealing temperature is needed to achieve their electrical characteristics of a-IGZO TFTs. For a low-temperature and high performance a-IGZO TFTs, therefore, it is necessarily considered that a-IGZO semiconductors could be damaged due to accelerated negative oxygen ions during conventional magnetron sputtering.
Investigation of Low-Frequency Noise Properties in High-Mobility ZnON Thin-Film Transistors
Chan-Yong Jeong,Hee-Joong Kim,Dae-Hwan Kim,Hyun-Suk Kim,Eok Su Kim,Tae Sang Kim,Joon Seok Park,Jong-Baek Seon,Kyoung Seok Son,Sunhee Lee,Seong-Ho Cho,Young Soo Park,Dae Hwan Kim,Hyuck-In Kwon IEEE 2016 IEEE electron device letters Vol.37 No.6
<P>We investigate the low-frequency noise (LFN) properties of amorphous zinc oxynitride (a-ZnON) thin-film transistors (TFTs) exhibiting high field-effect mobilities ranging from 48.5 to 118.9 cm<SUP>2</SUP>/V · s, depending on the gas flow rates during the deposition process. The measured noise power spectral density of the drain current shows that the LFN in a-ZnON TFTs obeys the classical 1/f noise theory, i.e., it is proportional to 1/f <SUP>γ</SUP> with γ~1 in the frequency range from 10 Hz to 1 kHz. The LFN from the a-ZnON TFT is successfully interpreted by the correlated number fluctuation-mobility fluctuation model. The near-interface dielectric trap density (Nτ) and the Coulomb scattering coefficient (α<SUB>S</SUB>) extracted from the measured LFN in a-ZnON TFTs are similar to those from the previously reported values for amorphous indium-gallium-zinc oxide TFTs. The relatively large values of N<SUB>T</SUB> and α<SUB>S</SUB> from the a-ZnON TFTs formed under O<SUB>2</SUB>-rich environment are mainly attributed to the high degree of disorder of the a-ZnON channel layer caused by the energetically broad and high density of subgap tail states.</P>
Hong Woo Lee,Bong Seob Yang,Yoon Jang Kim,Ah Young Hwang,Seungha Oh,Jong Hwan Lee,Jae Kyeong Jeong,Hyeong Joon Kim IEEE 2014 IEEE transactions on electron devices Vol.61 No.9
<P>This study examined the effects of the chamber pressure, radio frequency power and oxygen flow ratio during channel deposition on the performance and photobias stability of zinc tin oxide (ZTO) thin film transistors (TFTs). The densification of the ZTO thin film allowed the improvement in the field-effect mobility and the suppression in the negative bias illumination stress (NBIS) instability of the resulting TFTs simultaneously, irrespective of the specific process condition. The porosity in the ZTO channel layer was shown to prevent the effective intercalation of the Sn 5s orbital and, thus, deteriorate the field-effect mobility. Furthermore, the increased effective surface area in the porous ZTO film adversely affected the NBIS stability of the resulting TFTs because the porosity-related surface states and oxygen vacancy defects provide the hole trapping centers and the delocalized electron free carrier, respectively. Therefore, the densification of ZTO channel layer is a key factor for the high mobility and good photobias stability of the TFTs. This concept can be applicable for any metal-oxide-TFTs.</P>
Studies of the Stability of Microcrystaline Silicon Bottom-Gate TFTs under Electrical Stress
Oumkelthoum Moustapha,Alexey Abramov,Y. Bonnassieux,P. Roca i Cabarroca,H. Y. Choe 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.54 No.1
We present, in this paper, the stability results under bias stres of n-type microcrystaline silicon (μc-Si:H) botom- gate thin-film transistors (TFTs) with various intrinsic layer compositions (a single μc-Si layer or a dual intrinsic layer made of a-Si:H and μc-Si). TFTs were fabricated using the conventional amorphous silicon (a-Si:H) TFT proces(low temperature Plasma Enhanced Chemical Vapor Deposition). Our results suggest that the dual layer structure is advantageous in terms of procesing while keping good mobility and stability. After 24 hr of electrical stres the threshold voltage drift (ΔV<SUB>T</SUB>) was les than 0.2 V and mobility drift (Δμ) was about 8 %. In order to understand the causes of the instability, experimental analyses were performed; they showed that charge trapping at the interface was responsible for the degradation in the TFTs. Simulation of the impact of threshold voltage (V<SUB>T</SUB>) and the mobility drifts showed that a 1-V variation in V<SUB>T</SUB> induced a variation of 36 % in OLED curent and that a variation of 20 % in the mobility leads to a 23 % variation in the OLED curent.
Controlled Zr doping for inkjet-printed ZTO TFTs
Kim, Hunho,Choi, Woon-Seop Elsevier 2017 CERAMICS INTERNATIONAL Vol.43 No.6
<P><B>Abstract</B></P> <P>This study examined the effects of controlled Zr doping on the electrical properties of inkjet-printed zinc-tin oxide (ZTO) thin-film transistors (TFTs). In contrast to previous reports, below a certain doping concentration, improved electrical properties were obtained due to the effectively suppressed oxygen vacancies, reduced trapped electrons, and controlled carrier concentrations. The 0.0025M Zr-doped inkjet-printed ZTO TFTs showed higher mobility, higher on-to-off current ratio, lower threshold voltage, and lower subthreshold slope of 6.43cm<SUP>2</SUP>/Vs, 3.72×10<SUP>8</SUP>, 3.35V, and 0.53V/dec, respectively, compared to the un-doped TFTs. The bias stability of the Zr-doped inkjet-printed ZTO TFT was also improved.</P>
양희왕,조병수,박주현,신석윤,함기율,서형탁,전형탁 한국물리학회 2014 Current Applied Physics Vol.14 No.12
We reported the effects on the electrical behavior of amorphous indiumegalliumezinc oxide (a-IGZO) thin film transistors (TFTs) after introducing various positions and sizes of Au nanoparticles (NPs) in the channel layer. These TFTs showed an off-current increase and threshold voltage (Vth) shift compared to conventional a-IGZO TFTs. The effects of Au NPs are explained to form the carrier conduction path which causes the current leakage in the channel layer, and act as either electron injection sites or trap sites. Therefore, this study demonstrates that the optimized control of size and position of Au NPs in the channel layer is crucial for its application in the electrical stability improvement and Vth control of a- IGZO TFTs.