MgZnO/ZnO 이중 구조의 성장을 위한 사파이어 기판에서의 InZnO 버퍼층 연구

염아람,김홍승,안형수,장낙원 한국물리학회 2019 새물리 Vol.69 No.1

The replacement of Zn by Mg increases the bandgap of ZnO from 3.37 eV to 7.8 eV. The quantum-well structure of MgZnO/ZnO can be utilized as an active layer for ultra violet light-emitting diode (UV-LED) and high-mobility field effect transistor (HEMT). However, forming a high-quality MgZnO/ZnO heterostructure is difficult because of the lattice mismatch and surface roughness of the ZnO layer on a sapphire substrate. This study was carried out to introduce an InZnO buffer layer for the formation of a good-quality ZnMgO/ZnO quantum-well structure. Pulsed laser deposition (PLD) was used for this purpose, and X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to evaluate the structural properties. Atomic force microscopy (AFM) was also performed to observe surface changes. The addition of only a small amount of In improved the surface roughness of the buffer layers. This revealed that a buffer layer of InZnO is favorable for growing ZnMgO/ZnO thin films of high quality. Mg에 의한 Zn의 치환은 ZnO의 밴드 갭을 3.37 eV에서 7.8 eV로 증가시킨다. 이를 이용하여 ZnMgO/ZnO의 양자우물 구조 형성 시 UV-LED (ultra violet light-emitting diode) 및 ZnO 기반 고이동도 전계효과 트랜지스터의 활성층으로 활용할 수 있다. 하지만 양질의 ZnMgO/ZnO 구조를 사파이어 기판위에 형성 시 격자 불일치 및 ZnO 층의 표면 거칠기 등으로 양질의 이중 구조 박막의 형성이 어려운 실정이다. 본 연구는 양질의 ZnMgO/ZnO 양자우물 구조 형성을 위하여 InZnO 버퍼층을 도입하여 박막 표면의 변화를 관찰하고자 진행하였다. 이를 위하여 펄스 레이저 증착법을 이용하였고 형성된 InZnO의 구조적 특성 평가를 위하여 X-선 회절법 및 투과 전자현미경 분석을 행하였다. 또한 표면 변화 관찰을 위하여 원자력 현미경 분석도 실시하였다. 소량의 In 첨가로 InZnO 버퍼층은 ZnO 층에 비해 표면 거칠기가 급격히 감소하여 양질의 ZnMgO/ZnO 박막을 성장하기 위한 유리한 조건을 갖추었다.

Influence of carrier suppressors on electrical properties of solution-derived InZnO-based thin-film transistors

심재준,박상희,조원주 한국진공학회 2016 한국진공학회 학술발표회초록집 Vol.2016 No.2

Thermally evaporated amorphous InZnO thin film applicable to transparent conducting oxide for solar cells

Lee, Woo-Jung,Cho, Dae-Hyung,Kim, Yi Do,Choi, Myung-Woon,Choi, Jin Chul,Chung, Yong-Duck Elsevier 2019 JOURNAL OF ALLOYS AND COMPOUNDS Vol.806 No.-

<P><B>Abstract</B></P> <P>In recent years, amorphous InZnO (a-IZO) film gets recognition for the possibility as a transparent conducting oxide (TCO) layer with outstanding its optical and electrical properties in photovoltaic devices. Generally, the sputtering technique is normally used to deposit a-IZO film, which suffers from plasma damage exerting a negative influence on device performance. Here, we suggest an alternative to deposit a-IZO film with a thermal evaporation technique using a simply customized system to compensate defects by plasma damage. Thermally grown IZO films by controlling two variables of Zn rate and substrate temperature show the distinguishable characters in terms of transparency, conductivity and crystalline structure with a substantial change of Zn content in In<SUB>1-<I>x</I> </SUB>Zn<SUB> <I>x</I> </SUB>O. Zn incorporation in IZO film is considered as a critical key to determining the crystal structure and IZO film quality. In the thermal evaporation system, phase transition occurs from crystalline to amorphous; the IZO film indicates the superior property in the amorphous phase than crystalline structure. We acquired the optimized IZO film with amorphous phase in the relative concentration of In<SUB>0.73</SUB>Zn<SUB>0.27</SUB>O grown at 200 °C. To demonstrate the feasibility of a-IZO film as a TCO layer, Cu(In,Ga)Se<SUB>2</SUB> solar cell was practically fabricated, which shows excellent performance. It is attributed to the absence of plasma damage during deposition of the a-IZO film, proved by the decrease of shunt resistance in the solar cell.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The InZnO films were deposited by a customized thermal evaporation system by varying the Zn rate and substrate temperature. </LI> <LI> The quality of the InZnO film can be decided by Zn content to determine the crystal structure. </LI> <LI> Thermally evaporated InZnO film is satisfied for alternative TCO material transformed into the amorphous phase. </LI> <LI> The CIGS solar cell with an amorphous InZnO film as a TCO layer shows the superior cell performance. </LI> </UL> </P>

Fabrication and Comparison of the Properties of SnInZnO and InZnO TFTs Processed by Using the Sol-gel Method

심종현,최준혁,이창민,박경,김형섭,이후정,임준형,문미란,정동근,주진호 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.57 No.61

We fabricated InZnO and SnInZnO thin film transistors using the sol-gel process and evaluated the effect of Sn alloying on the electrical properties and the microstructure of the films. We used high-purity indium nitrate hydrate, tin chloride dihydrate, and zinc acetate dihydrate as the precursors, which were dissolved in 2-methoxyethanol at molar ratios of 1:1 and 1:1:1 for InZnO and SnInZnO, respectively. The gel film was deposited onto a highly-doped p-type Si substrate by spin-coating, followed by sintering at 400 ℃ in air for 1 h. The microstructural observation indicated that the SnInZnO film had an amorphous structure whereas the InZnO film consisted of a mixed amorphous and nanocrystalline structure. For the SnInZnO thin film transisotor (TFT), the threshold voltage, the on/off current ratio, and the saturating mobility were 32.5 V, 1.8 × 10 5, and 3.12 cm 2/Vs, respectively, which were superior to those for the InZnO TFT. Based on the X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) analyses, the enhanced electrical properties were attributed to the improved controllability of the oxygen vacancies and to the amorphous structure afforded by the Sn alloying. Therefore, we conclude that SnInZnO semiconductors fabricated by using the sol-gel process represent a viable alternative to InGaZnO TFTs.

펄스레이저증착법으로 증착한 Indium Zinc Oxide 박막의 물성

최학순,정일교,신문수,김헌오,김용수,Choi, Hak-Soon,Jeong, Il-Kyo,Shin, Mun-Soo,Kim, Heon-Oh,Kim, Yong-Soo 한국전기전자재료학회 2011 전기전자재료학회논문지 Vol.24 No.7

Recently, n-InZnO/p-CuO oxide diode has attracted great attention due to possible application for selector device of 3-dimensional cross-point resistive memory structures. To investigate the detailed properties of InZnO (IZO), we have deposited IZO films on the fused quartz substrate using PLD (pulsed laser deposition) method at oxygen pressure of 1~100 mTorr and substrate temperature of RT$\sim600^{\circ}C$. The influence of oxygen pressure and substrate temperature on structural, optical and electrical of IZO films is analyzed using XRD (x-ray diffraction), SEM (scanning electron microscopy), UV-Vis spectrophotometry, spectroscopic ellipsometry (SE) and hall measurements. The XRD results shows that the deposited thin films are polycrystalline over $300^{\circ}C$ of substrate temperature independent of oxygen pressure. The resistivity of films was increased as oxygen pressure and substrate temperature decrease. The thickness and optical constants of the deposited films measured with UV-Vis spectrophotometer were also compared with those of broken SEM and SE results.

Channel scaling and field-effect mobility extraction in amorphous InZnO thin film transistors

Lee, Sunghwan,Song, Yang,Park, Hongsik,Zaslavsky, A.,Paine, D.C. Elsevier 2017 Solid-state electronics Vol.135 No.-

<P><B>Abstract</B></P> <P>Amorphous oxide semiconductors (AOSs) based on indium oxides are of great interest for next generation ultra-high definition displays that require much smaller pixel driving elements. We describe the scaling behavior in amorphous InZnO thin film transistors (TFTs) with a significant decrease in the extracted field-effect mobility μ<SUB>FE</SUB> with channel length <I>L</I> (from 39.3 to 9.9cm<SUP>2</SUP>/V·s as <I>L</I> is reduced from 50 to 5μm). Transmission line model measurements reveal that channel scaling leads to a significant μ<SUB>FE</SUB> underestimation due to contact resistance (<I>R</I> <SUB>C</SUB>) at the metallization/channel interface. Therefore, we suggest a method of extracting correct μ<SUB>FE</SUB> when the TFT performance is significantly affected by <I>R</I> <SUB>C</SUB>. The corrected μ<SUB>FE</SUB> values are higher (45.4cm<SUP>2</SUP>/V·s) and nearly independent of <I>L</I>. The results show the critical effect of contact resistance on μ<SUB>FE</SUB> measurements and suggest strategies to determine accurate μ<SUB>FE</SUB> when a TFT channel is scaled.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We obtained high field-effect mobility μ<SUB>FE</SUB> =45.4cm<SUP>2</SUP>/V·s in long channel <I>L</I> =50μm IZO TFTs. </LI> <LI> The apparent extracted μ<SUB>FE</SUB> collapses as <I>L</I> is scaled down. </LI> <LI> A method for recovering the correct μ<SUB>FE</SUB> is illustrated based on our TFT characteristics. </LI> </UL> </P>

스퍼터링 공정 압력이 InZnO 박막트랜지스터의 광학 및 전기적 특성에 미치는 영향

박지민,김형도,장성철,김현석,Park, Ji-Min,Kim, Hyoung-Do,Jang, Seong Cheol,Kim, Hyun-Suk 한국재료학회 2020 한국재료학회지 Vol.30 No.4

Amorphous In-Ga-Zn-O (a-IGZO) thin film transistors, because of their relatively low mobility, have limits in attempts to fulfill high-end specifications for display backplanes. In-Zn-O (IZO) is a promising semiconductor material for high mobility device applications with excellent transparency to visible light region and low temperature process capability. In this paper, the effects of working pressure on the physical and electrical properties of IZO films and thin film transistors are investigated. The working pressure is modulated from 2 mTorr to 5 mTorr, whereas the other process conditions are fixed. As the working pressure increases, the extracted optical band gap of IZO films gradually decreases. Absorption coefficient spectra indicate that subgap states increase at high working pressure. Furthermore, IZO film fabricated at low working pressure shows smoother surface morphology. As a result, IZO thin film transistors with optimum conditions exhibit excellent switching characteristics with high mobility (≥ 30㎠/Vs) and large on/off ratio.

Comparative Evaluation of Solution Processed InZnO Junctionless Thin-Film Transistors in Different Post-Treatment Method

박정훈,안민주,조원주 한국진공학회 2014 한국진공학회 학술발표회초록집 Vol.2014 No.2

Plasma-Enhanced Atomic Layer Deposition Processed SiO₂ Gate Insulating Layer for High Mobility Top-Gate Structured Oxide Thin-Film Transistors

Jong Beom Ko,Hye In Yeom,Sang-Hee Ko Park IEEE 2016 IEEE electron device letters Vol.37 No.1

<P>SiO2 processed by plasma-enhanced atomic layer deposition (PEALD) was applied as a gate insulator (GI) to the top gate high mobility InZnO (IZO) thin-film transistor (TFT). In as-fabricated devices, while IZO TFTs with GI processed by PEALD shows high ON/OFF ratio characteristics, the devices with GI deposited by plasma-enhanced chemical vapor deposition showed the conductive characteristics. From the secondary ion mass spectroscopy analysis, it is inferred that PEALD processed SiO2 generates fewer free electron donating elements in the active layer. The IZO TFT with PEALD processed GI exhibits a high-field effect mobility of 32.9 cm(2)/V.s, V-ON of -0.3 V, and Delta V-ON of 0.56 V under positive bias temperature stress (1 MV/cm, 60 degrees C, 3600 s) after being subject to thermal annealing at 350 degrees C.</P>

Analysis of Instability Mechanism under Simultaneous Positive Gate and Drain Bias Stress in Self-Aligned Top-Gate Amorphous Indium-Zinc-Oxide Thin-Film Transistors

Kim, Jonghwa,Choi, Sungju,Jang, Jaeman,Jang, Jun Tae,Kim, Jungmok,Choi, Sung-Jin,Kim, Dong Myong,Kim, Dae Hwan The Institute of Electronics and Information Engin 2015 Journal of semiconductor technology and science Vol.15 No.5

We quantitatively investigated instability mechanisms under simultaneous positive gate and drain bias stress (SPGDBS) in self-aligned top-gate amorphous indium-zinc-oxide thin-film transistors. After SPGDBS ($V_{GS}=13V$and $V_{DS}=13V$), the parallel shift of the transfer curve into a negative $V_{GS}$ direction and the increase of on current were observed. In order to quantitatively analyze mechanisms of the SPGDBS-induced negative shift of threshold voltage (${\Delta}V_T$), we experimentally extracted the density-of-state, and then analyzed by comparing and combining measurement data and TCAD simulation. As results, 19% and 81% of ${\Delta}V_T$ were taken to the donor-state creation and the hole trapping, respectively. This donor-state seems to be doubly ionized oxygen vacancy ($V{_O}^{2+}$). In addition, it was also confirmed that the wider channel width corresponds with more negative ${\Delta}V_T$. It means that both the donor-state creation and hole trapping can be enhanced due to the increase in self-heating as the width becomes wider. Lastly, all analyzed results were verified by reproducing transfer curves through TCAD simulation.