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RISS 인기검색어
- 검색키워드
- 저자 : Ved Prakash Verma (검색결과 3 건)
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김도현,전민현,전훈하,임재영,문주호,이성휘,Ved Prakash Verma,최원봉 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.51 No.III
The optical and the electrical properties of undoped zinc-oxide (ZnO) thin lms of various thicknesseswerecomparedwiththoseofGa-doped(GZO)thinlms. Transparent,high-qualityundoped ZnO and GZO lms were deposited successfully using radio-frequency (RF) sputtering at room temperature. The lms were polycrystalline with a hexagonal structure and a strongly preferred orientation along the c-axis. The lms had an average optical transmission >85 % in the visible partoftheelectromagneticspectrum. TheundopedZnOthinlmsweremoretransparentthanthe GZO thin lms. The ZnO thin-lm transistors (TFTs) were operated in the enhancement mode withathresholdvoltageof2.5V.Incontrary,theGa-dopedZnOTFTswereoperatedinadepletion mode with a threshold voltage of {3.4 V. We successfully demonstrated undoped and the Ga-doped ZnO TFTs by using conventional SiO2 gate insulators at room temperature. We postulate that undoped ZnO lms, which have not been treated to improve the optical properties, can be used, instead of doped ZnO lms, in transparent devices for next generation optoelectronic devices. The optical and the electrical properties of undoped zinc-oxide (ZnO) thin films of various thicknesses were compared with those of Ga-doped (GZO) thin films. Transparent, high-quality undoped ZnO and GZO films were deposited successfully using radio-frequency (RF) sputtering at room temperature. The films were polycrystalline with a hexagonal structure and a strongly preferred orientation along the $c$-axis. The films had an average optical transmission $>$85 \% in the visible part of the electromagnetic spectrum. The undoped ZnO thin films were more transparent than the GZO thin films. The ZnO thin-film transistors (TFTs) were operated in the enhancement mode with a threshold voltage of 2.5 V. In contrary, the Ga-doped ZnO TFTs were operated in a depletion mode with a threshold voltage of --3.4 V. We successfully demonstrated undoped and the Ga-doped ZnO TFTs by using conventional SiO$_2$ gate insulators at room temperature. We postulate that undoped ZnO films, which have not been treated to improve the optical properties, can be used, instead of doped ZnO films, in transparent devices for next generation optoelectronic devices.
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Hoonha Jeon,전민현,Do-Hyun Kim,Dongjo Kim,문주호,Kyoungseok Noh,Ved Prakash Verma,Wonbong Choi 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.51 No.III
In this paper we present bottom-gate-type ZnO-based TFTs with low threshold voltages fabricated with a conventional SiO$_2$ gate insulator by radio-frequency (RF) magnetron sputtering at room temperature. The SiO$_2$ is used as a gate insulator, and it is possible to achieve a low gate leakage current ($<$10 pA) by using this conventional SiO$_2$ oxide without new gate oxide materials. The ZnO film also has good uniformity and transparency. The ZnO TFTs operate in the enhancement mode with a threshold voltage of 2.5 V. A mobility of 0.018 cm$^2$/(V$\cdot$s), an on/off ratio of about 10$^4$, and a gate voltage swing of 1.7 V/decade are obtained. We successfully demonstrate that a ZnO TFT with comparable electrical characteristics can be fabricated by utilizing the conventional SiO$_2$ gate insulator. It is also possible to reduce the power consumption due to their low threshold voltage and low leakage current.
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전훈하,노경석,김도현,최원봉,전민현,Jeon, Hoon-Ha,Verma, Ved Prakash,Noh, Kyoung-Seok,Kim, Do-Hyun,Choi, Won-Bong,Jeon, Min-Hyon 한국진공학회 2007 Applied Science and Convergence Technology Vol.16 No.5
본 논문에서는 zinc oxide (ZnO)와 gallium이 도핑 된 zinc oxide (GZO)를 이용하여 radio frequency (RF) magnetron sputtering 방법에 의해 상온에서 제작된 bottom-gate 박막 트랜지스터의 특성을 평가하고 분석하였다. 게이트 절연층 물질로서 새로운 물질을 사용하지 않고 열적 성장된 $SiO_2$를 사용하여 게이트 누설 전류를 수 pA 수준까지 줄일 수 있었다. ZnO와 GZO 박막의 표면 제곱평균제곱근은 각각 1.07 nm, 1.65 nm로 측정되었다. 그리고 ZnO 박막은 80% 이상, GZO 박막은 75% 이상의 투과도를 가지고 있었고, 박막의 두께에 따라 투과도가 달라졌다. 또한 두 시료 모두 (002) 방위로 잘 정렬된 wurtzite 구조를 가지고 있었다. 제작된 ZnO 박막 트랜지스터는 2.5 V의 문턱 전압, $0.027\;cm^2/(V{\cdot}s)$의 전계효과 이동도, 104의 on/off ratio, 1.7 V/decade의 gate voltage swing 값들을 가지고 있었고, enhancement 모드 특성을 가지고 있었다. 반면에 GZO 박막 트랜지스터의 경우에는 -3.4 V의 문턱 전압, $0.023\;cm^2/(V{\cdot}s)$의 전계효과 이동도, $2{\times}10^4$의 on/off ratio, 3.3 V/decade의 gate voltage swing 값들을 가지고 있었고, depletion 모드 특성을 가지고 있었다. 우리는 기존의 ZnO와 1wt%의 Ga이 도핑된 ZnO를 이용하여 두 가지 모드의 트랜지스터 특성을 보이는 박막 트랜지스터를 성공적으로 제작하고 분석하였다. In this paper we present a bottom-gate type of zinc oxide (ZnO) and Gallium (Ga) doped zinc oxide (GZO) based thin film transistors (TFTs) through applying a radio frequency (RF) magnetron sputtering method at room temperature. The gate leakage current can be reduced up to several ph by applying $SiO_2$ thermally grown instead of using new gate oxide materials. The root mean square (RMS) values of the ZnO and GZO film surface were measured as 1.07 nm and 1.65 nm, respectively. Also, the transmittances of the ZnO and GZO film were more than 80% and 75%, respectively, and they were changed as their film thickness. The ZnO and GZO film had a wurtzite structure that was arranged well as a (002) orientation. The ZnO TFT had a threshold voltage of 2.5 V, a field effect mobility of $0.027\;cm^2/(V{\cdot}s)$, a on/off ratio of $10^4$, a gate voltage swing of 17 V/decade and it operated in a enhancement mode. In case of the GZO TFT, it operated in a depletion mode with a threshold voltage of -3.4 V, a field effect mobility of $0.023\;cm^2/(V{\cdot}s)$, a on/off ratio of $2{\times}10^4$ and a gate voltage swing of 3.3 V/decade. We successfully demonstrated that the TFTs with the enhancement and depletion mode type can be fabricated by using pure ZnO and 1wt% Ga-doped ZnO.
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