Korean Journal of Materials Research (한국재료학회지)

Materials Research Society of Korea (한국재료학회)
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Properties of the RF Sputter Deposited n-ZnO Thin-Film and the n-ZnO/p-GaN heterojunction LED

RF스퍼터링법으로 성장시킨 n-ZnO 박막과 n-ZnO/p-GaN 이종접합 LED의 특성

  • Shin, Dongwhee (Department of Materials Engineering and Research Center for Infotronic Materials and Devices, Hanbat National University) ;
  • Byun, Changsub (Department of Materials Engineering and Research Center for Infotronic Materials and Devices, Hanbat National University) ;
  • Kim, Seontai (Department of Materials Engineering and Research Center for Infotronic Materials and Devices, Hanbat National University)
  • 신동휘 (한밭대학교 신소재공학과 및 정보전자부품소재연구소) ;
  • 변창섭 (한밭대학교 신소재공학과 및 정보전자부품소재연구소) ;
  • 김선태 (한밭대학교 신소재공학과 및 정보전자부품소재연구소)
  • Received : 2012.12.12
  • Accepted : 2013.02.26
  • Published : 2013.03.27
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Abstract

The ZnO thin films were grown on GaN template substrates by RF magnetron sputtering at different RF powers and n-ZnO/p-GaN heterojunction LEDs were fabricated to investigate the effect of the RF power on the characteristics of the n-ZnO/p-GaN LEDs. For the growth of the ZnO thin films, the substrate temperature was kept constant at $200^{\circ}C$ and the RF power was varied within the range of 200 to 500W at different growth times to deposit films of 100 nm thick. The electrical, optical and structural properties of ZnO thin films were investigated by ellipsometry, X-ray diffraction (XRD), atomic force microscopy (AFM), photoluminescence (PL) and by assessing the Hall effect. The characteristics of the n-ZnO/p-GaN LEDs were evaluated by current-voltage (I-V) and electroluminescence (EL) measurements. ZnO thin films were grown with a preferred c-axis orientation along the (0002) plane. The XRD peaks shifted to low angles and the surface roughness became non-uniform with an increase in the RF power. Also, the PL emission peak was red-shifted. The carrier density and the mobility decreased with the RF power. For the n-ZnO/p-GaN LED, the forward current at 20 V decreased and the threshold voltage increased with the RF power. The EL emission peak was observed at approximately 435 nm and the luminescence intensity decreased. Consequently, the crystallinity of the ZnO thin films grown with RF sputtering powers were improved. However, excess Zn affected the structural, electrical and optical properties of the ZnO thin films when the optimal RF power was exceeded. This excess RF power will degrade the characteristics of light emitting devices.

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References

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