First-Principles Study of the Electronic Structure of Single-Crystalline InGaZnO4

Il-Joon Kang,박철홍 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.56 No.1

Through first-principles calculations, we investigate the electronic structures of single crystals of InGaZnO4 (sc-InGaZnO4), which have a complex structure consisting of InO2 layers inter-stacked with GaZnO2 double layers. Within the GaZnO2 layers, Zn and Ga atoms alternatively occupy the cation sites. We find that the conduction band of the sc-InGaZnO4 is composed of the hybridization of In-s, Ga-s, Zn-s and O-p orbitals while the valence bands are characterized dominantly by O-p orbitals. At the conduction band, the energy of In-s band are lower than those of Ga and Zn atoms the Ga-driven states are slightly lower than Zn-driven states, and the band widths of the Zn- and Ga-driven bands are wider than that of the In-driven band.

First-Principles Study of the Microscopic Properties of the O Vacancies in Single-Crystalline InGaZnO4

Il-Joon Kang,박철홍 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.56 No.1

Through first-principles calculations, the electronic structures and the microscopic properties of the O vacancies (VO) in the transparent semiconductor oxide InGaZnO4 are investigated. The results are compared to those for vacancies in In2O3, Ga2O3, and ZnO. Electronic structure calculations indicate that the VO make deep-donor levels in binary oxides while the VO make shallow donor-like levels in the quaternary InGaZnO4. The vacancy induced a tensile stress in all the tested oxides. The total energy calculations indicate that the VO are energetically favored to be located between the In-O and the Ga-Zn-O layers in InGaZnO4.

Improvement of Electrical Performance of InGaZnO/HfSiO TFTs with 248-nm Excimer Laser Annealing

Hau-Yuan Huang,Shui-Jinn Wang,Chien-Hung Wu,Chien-Yuan Lu 대한금속·재료학회 2014 ELECTRONIC MATERIALS LETTERS Vol.10 No.5

The influence of 248-nm KrF excimer laser annealing (ELA) with energy density between 0 and 400 mJ/cm2 on the electrical behavior of indium gallium zinc oxide (InGaZnO) thin-film transistors (TFTs) is investigated. The experimental results show that the saturation mobility and subthreshold swing are improved from 12.4 cm2/Vs and 100 mV/dec without ELA to 17.8 cm2/Vs and 75 mV/dec, respectively, by applying a 300 mJ/cm2 laser pulse after the source/drain deposition, while maintaining an almost unchanged turn-off voltage. Such improvements are attributed to the increase in the oxygen vacancies and reduction in the bulk traps in the InGaZnO channel.

Measurement of band offsets in MgO/InGaZnO4 heterojunction by X-ray photoelectron spectroscopy

최병수,K. W. Kim,B. P Gila,D. P. NORTON,S. J. PEARTON,조현 한양대학교 세라믹연구소 2017 Journal of Ceramic Processing Research Vol.18 No.9

Amorphous InGaZnO4 (α-IGZO) thin film transistors (TFTs) are one of the most promising candidates for switches in theactive-matrix and driver-integrated circuits of transparent liquid crystal displays and flexible displays. The stability andoverall performance of amorphous IGZO TFTs depend to a great extent on the band offsets in gate dielectric/α-IGZOheterojunction. The energy discontinuity in the valence band (ΔEV) and conduction band (ΔEC) in MgO/IGZO heterojunctionswere systematically examined by using X-ray photoelectron spectroscopy (XPS). The MgO gate dielectric was found to havea straddled type band offset alignment on the IGZO. The valence band offset value for the MgO/IGZO heterojunction wasdetermined as 0.81 ± 0.17 eV using the Ga 2p3/2, Zn 2p3/2 and In 3d5/2 energy levels as references. The bandgap energy differencebetween the MgO and IGZO led to a corresponding conduction band offset (ΔEC) of ~3.79 eV and a nested interface alignment.

SiOx interlayer to enhance the performance of InGaZnO-TFT with AlOx gate insulator

Jun Li,Fan Zhou,Hua-Ping Lin,Wen-Qing Zhu,Jianhua Zhang,Xue-Yin Jiang,Zhi-Lin Zhang 한국물리학회 2012 Current Applied Physics Vol.12 No.5

We have fabricated indium-gallium-zinc (IGZO) thin film transistor (TFT) using SiOx interlayer modified aluminum oxide (AlOx) film as the gate insulator and investigated their electrical characteristics and bias voltage stress. Compared with IGZO-TFT with AlOx insulator, IGZO-TFT with AlOx/SiOx insulator shows superior performance and better bias stability. The saturation mobility increases from 5.6 cm2/V s to 7.8 cm2/V s, the threshold voltage downshifts from 9.5 V to 3.3 V, and the contact resistance reduces from 132 Ucm to 91 Ucm. The performance improvement is attributed to the following reasons: (1) the introduction of SiOx interlayer improves the insulator surface properties and leads to the high quality IGZO film and low trap density of IGZO/insulator interface. (2) The better interface between the channel and S/D electrodes is favorable to reduce the contact resistance of IGZO-TFT.

펄스 레이저 증착 방법으로 성장한 InGaZnO4 박막의 물리적 특성 연구

황은상,서유성,박수환,배종성,안재석,황정식,박성균 한국진공학회 2011 한국진공학회 학술발표회초록집 Vol.40 No.0

소스 및 드레인 전극 재료에 따른 비정질 InGaZnO 박막 트랜지스터의 소자 열화

이기훈,강태곤,이규연,박종태,Lee, Ki Hoon,Kang, Tae Gon,Lee, Kyu Yeon,Park, Jong Tae 한국정보통신학회 2017 한국정보통신학회논문지 Vol.21 No.1

본 연구에서는 소스 및 드레인 전극 재료에 따른 소자 열화를 분석하기 위해 Ni, Al, 및 ITO를 소스 및 드레인 전극 재료로 사용하여 InGaZnO 박막 트랜지스터를 제작하였다. 전극 재료에 따른 소자의 전기적 특성을 분석한 결과 Ni 소자가 이동도, 문턱전압 이하 스윙, 구동전류 대 누설전류 비율이 가장 우수하였다. 소스 및 드레인 전극 재료에 따른 소자 열화 측정결과 Al 소자의 열화가 가장 심한 것을 알 수 있었다. InGaZnO 박막 트랜지스터의 소자 열화 메카니즘을 분석하기 위하여 채널 폭과 스트레스 드레인 전압을 다르게 하여 문턱전압 변화를 측정하였다. 그 결과 채널 폭이 넓을수록 또 스트레스 드레인 전압이 높을수록 소자 열화가 많이 되었다. 측정결과로부터 InGaZnO 박막 트랜지스터의 소자 열화는 큰 채널 전계와 주울 열의 결합 작용으로 발생함을 알 수 있었다. In this work, InGaZnO thin film transistors with Ni, Al and ITO source and drain electrode materials were fabricated to analyze a hot carrier induced device degradation according to the electrode materials. From the electrical measurement results with electrode materials, Ni device shows the best electrical performances in terms of mobility, subthreshold swing, and $I_{ON}/I_{OFF}$. From the measurement results on the device degradation with source and drain electrode materials, Al device shows the worst device degradation. The threshold voltage shifts with different channel widths and stress drain voltages were measured to analyze a hot carrier induced device degradation mechanism. Hot carrier induced device degradation became more significant with increase of channel widths and stress drain voltages. From the results, we found that a hot carrier induced device degradation in InGaZnO thin film transistors was occurred with a combination of large channel electric field and Joule heating effects.

A Simple Intermediate Approach of Sputter Deposition at Room Temperature for Improving the Stability of a-InGaZnO Thin Film Transistors

Chunlan Wang,Yebo Jin,Yuqing Li,Gangying Guo,Yongle Song,Hao Huang,Aolin Wang,Han He 대한금속·재료학회 2023 ELECTRONIC MATERIALS LETTERS Vol.19 No.4

Amorphous InGaZnO (a-InGaZnO) thin film transistors (TFTs) with stability and low-temperature deposition are importantchallenges for their application in flexible electronics. Herein, a-InGaZnO films were successfully obtained throughout thewhole process in the room-temperature sputtering system. An intermediate nitrogen treatment a-InGaZnO film link contributedto high performance a-InGaZnO TFTs. The current switching ratio of the optimal nitrogen treatment transistor is closeto 107,the field-effect mobility (μFE) is 11.7 cm2/Vs and threshold voltage (VTH) is − 0.12 V, respectively. And the 4-daythreshold voltage offset (ΔVTH) is reduced from 12.98 to 4.92 V. The improved electrical properties may be attributed to thereduction of defect concentration and average interfacial trap density due to nitrogen occupation of oxygen vacancies (VO).

Negative bias illumination stress instability in amorphous InGaZnO thin film transistors with transparent source and drain

Lee, J.H.,Yu, S.K.,Kim, J.W.,Ahn, M.J.,Cho, W.J.,Park, J.T. Pergamon Press 2016 Microelectronics and reliability Vol.64 No.-

<P>The investigations on the device instabilities in amorphous InGaZnO TFTs with metal (Ni) and transparent (ITO and InGaZnO) source and drain electrodes have been performed under negative bias stress (NBS), negative bias thermal stress (NBTS), negative bias illumination stress (NBIS) and negative bias thermal and illumination stress (NBTIS). From the measured device parameters in dark and under illumination conditions, a-IGZO TFTs with InGaZnO source and drain show an excellent device performances and lower device degradation than the devices with Ni and ITO source and drain under NBS and NBTS. However, amorphous IGZO TFTs with InGaZnO source and drain electrodes show more significant device degradation under NBIS and NBTIS. In order to explain our experimental results, we propose that the center responsible for the device instability is the process-related defects under NBS and NBTS, and the oxygen vacancy under NBIS and NBTIS, respectively. (C) 2016 Elsevier Ltd. All rights reserved.</P>

무접합 비정질 InGaZnO 박막 트랜지스터의 게이트 산화층 항복 특성

장유진,서진형,박종태,Chang, Yoo Jin,Seo, Jin Hyung,Park, Jong Tae 한국정보통신학회 2018 한국정보통신학회논문지 Vol.22 No.1

박막 두께가 다른 무접합 비정질 InGaZnO 막막 트랜지스터를 제작하고 박막 두께, 동작 온도 및 빛의 세기에 따른 소자의 성능 변수를 추출하고 게이트 산화층 항복전압을 분석하였다. 박막의 두께가 클수록 소자의 성능이 우수하나 드레인 전류의 증가로 게이트 산화층 항복전압은 감소하였다. 고온에서도 소자의 성능은 개선되었으나 게이트 산화층 항복 전압은 감소하였다. 빛의 세기가 증가할수록 광자에 의해 생성된 전자로 드레인 전류는 증가 하였으나 역시 게이트 산화층 항복전압은 감소하였다. 박의 두께가 클수록, 고온일수록, 빛의 세기가 강할수록 채널의 전자수가 증가하여 산화층으로 많이 주입되었기 때문이다. 무접합 a-IGZO 트랜지스터를 BEOL 트랜지스터로 사용하기 위해서는 박막 두께 및 동작 온도를 고려해서 산화층 두께를 설정해야 됨을 알 수 있었다. Junctionless amorphous InGaZnO thin film transistors with different film thickness have been fabricated. Their device performance parameters were extracted and gate oxide breakdown voltages were analyzed with different film thickness. The device performances were enhanced with increase of film thickness but the gate oxide breakdown voltages were decreased. The device performances were enhanced with increase of temperatures but the gate oxide breakdown voltages were decreased due to the increased drain current. The drain current under illumination was increased due to photo-excited electron-hole pair generation but the gate oxide breakdown voltages were decreased. The reason for decreased breakdown voltage with increase of film thickness, operation temperature and light intensity was due to the increased number of channel electrons and more injection into the gate oxide layer. One should decide the gate oxide thickness with considering the film thickness and operating temperature when one decides to replace the junctionless amorphous InGaZnO thin film transistors as BEOL transistors.