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GaAs 기판위에 성장된 단결정 AlAs 층의 선택적 산화 및 XPS ( X-ray photonelectron spectroscopy ) 분석
이용수 ( Young Soo Lee ),이용수 ( Young Soo Lee ),이정희 ( Jung Hee Lee ),태흥식 ( Heung Sik Tae ),이석헌 ( Suk Hun Lee ),이용현 ( Young Hyun Lee ) 한국센서학회 1996 센서학회지 Vol.5 No.5
A 1 ㎛ thick n-type GaAs layer with Si doping density of 1*10^17/㎤ and a 500Å thick undoped single crystalline AlAs layer were subsequently grown by molecular beam epitaxy on the n^+ GaAs substrate. The AlAs/GaAs layer was oxidized in N_2 bubbled H_2O vapor(95℃) ambient at 400℃ for 2 and 3 hours. From the result of XPS analysis, small amounts of As_2O_3, AlAs, and elemental As were found in the samples oxidized up to 2 hours. After 3 hours oxidation, however, various oxides related to As were dissolved and As atoms were diffused 3 hours the oxide surface. The as-grown AlAs/GaAs layer was selectively converted to Al_2O_3/GaAs at the oxidation temperature 400℃ for 3 hours. The oxidation temperature and time is very critical to stop the oxidation at the AlAs/GaAs interface and to form a defect-free surface layer.
GaN를 이용한 Schottky diode형 자외선 수광소자의 제작
성익중,이석헌,이채향,이용현,이정희,함성호,Seong, Ik-Joong,Lee, Suk-Hun,Lee, Chae-Hyang,Lee, Yong-Hyun,Lee, Jung-Hee,Hahm, Sung-Ho 대한전자공학회 1999 電子工學會論文誌, D Vol.d36 No.6
본 논문에서는 GaN 박막 위에 각각 알루미늄(Al)과 백금(Pt)을 증착하여 저항성 전극 및 투명한 schottky 전극을 형성한 평면형 자외선 수광소자를 제작하였다. 제작된 소자에 대해 전기적 특성과 광학적 특성을 조사하여 자외선 센서로서의 적합성을 검토하였다. 사파이어 기판위에 성장된 GaN 박막은 $7.8{\times}10^{16}cm^{-3}$의 도핑(doping)농도와 $138 cm^2/V{\cdot}s$의 이동도(mobility)를 가졌으며, 파장이 365 nm 이하인 빛만을 흡수하는 자외선 감지막 특성을 나타내었다. 5 V의 역방향 전압을 인가하였을 때 제조된 schottky형 자외선 센서는 325 nm의 자외선 파장에서 응답도가 2.84 A/W였고, $4{\times}10^4$의 큰 신호대 잡음비(SNR)의 $3.5{\times}10^9$W의 잡음등가전력(NEP)을 나타내었다. 따라서 이들 결과로부터 GuN를 이용한 schottky 다이오드가 가시광 차단 UV photodetector를 제조할 수 있음을 확인하였다. We fabricated a planar ultra-violet photodetector whose ohmic and schottky contacts were respectively formed with evaporated Al and Pt on the GaN layer. To examine the applicability of the device to the UV sensor, we investigated its electrical and optical characteristics. The GaN layer on the sapphire waver had $7.8{\times}10^{16}cm^{-3}$ of doping concentnation and the $138 cm^2/V{\cdot}s$ of electron mobility and it absorbed the spectrum of the light below 325 nm wavelength. It had the responsivity of 2.8 A/W of at 325 nm, and the signal to noise ratio(SNR) of $4{\times}10^4$, and the noise equivalent power(NEP) of $3.5{\times}10^9$W under 5 V reverse bias. These results confirmed that the GaN schottky diode had a solar blind properly when it was applied to the UV photodetector.
표면 Micromachining법을 이용한 MIMIC용 ZnO-FBAR(Thin-Film Bulk Acoustic Wave Resonator)의 제조 및 그 특성
김상호,조인귀,이석헌,최현철,이용현 경북대학교 센서기술연구소 1997 센서技術學術大會論文集 Vol.8 No.1
FBAR(Thin-Film Bulk Acoustic wave Resonator) is monolithically integrable with semiconductor device, leading to small size and low cost, high Q rf circuit elements with applications in the radar and communications area. FBAR with Air-gap used in high frequency range(GHz range) was fabricated by surface micromachining technique. Zinc Oxide(ZnO) thin film was used as piezoelectric material and was deposited by rf magnetron sputtering. The thickness of ZnO thin film was about 1 μm. Thin metal film(Ni-Cr:50 Å/Au:1000 Å) was used as top and bottom electrodes to reduce acoustic wave loss. The measured resonant frequency of the FBAR was 2.95 GHz and S_(11) value(forward reflection value) was -18.912 dB.
Al/α-BaTiO₃/SiO₂/TiW실리사이드 안티퓨즈의 제조
이재성,류창명,이석헌,김창균,이용현 경북대학교 센서기술연구소 1995 센서技術學術大會論文集 Vol.6 No.1
A metal-insulator-metal(MIM) antifuse has been developed for highly reliable performance and easily controllable program voltage. Sharp distribution of insulator breakdown voltage is obtained by using TiWsilicide film as a bottom electrode having extremely smooth surface. In the MIM antifuse composed of amorphous BaTiO_(3)/SiO_(2) layers, the breakdown voltage is reliably controlled by the thickness of amorphous BaTiO_(2) film and the leakage current is effectively suppressed by the SiO_(2) film. Low programming voltage(14.4V), low ON resistance (40-50Ω), and high OFF resistance(several GΩ) can be otained in the MIM antifuses having Al/α-BaTiO_(3)(120Å)/SiO_(2)(120 Å)/TiWsilicide structure. These MIM antifuse structure could be applicable to programming logic device.