Fabrication and Characterization of Aluminum Doped Zinc Oxide Thin Film transistors Grown by Radio Frequency Sputtering Technique

Graduate #69
Discipline: Nanoscience
Subcategory: Nanoscience
Session: 3
Room: Park Tower 8228

Kelsea A. Yarbrough - Norfolk State University
Co-Author(s): Sangram K. Pradhan, Norfolk State University, Norfolk, VA; Messaoud Bahoura, Norfolk State University, Norfolk, VA

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In this present generation, display technology has rapidly advanced the necessity for commercial products for small handheld devices to large TVs. The backbone of these applications require a central operation of a Thin Film Transistor (TFT). Commercially, TFTs are being developed using hydrogenated amorphous silicon (a-Si:H) and/or indium gallium doped zinc oxide (IGZO). However a-Si:H is not a naturally transparent material, exhibits low mobility and possesses large leakage currents. Along with the shortcomings of a-Si:H, IGZO requires high fabrication and annealing temperatures, and also indium element is a rare element, proceeding to very limited storage on earth. The indium-free oxide-based channel material such as aluminum-doped zinc oxide (AZO) is an alternative material and can be fabricated on glass substrate for TFT application. High quality AZO thin films were grown using radio frequency (RF) sputtering technique on n-type silicon, glass, and sapphire for characterization purposes. The AZO thin films were grown at different temperatures and thicknesses to analyze the effect growth morphology and transistor characteristics. The effect of Al content on zinc oxide crystal lattice were investigated by Atomic Force Microscopy (AFM), X-ray diffraction, Field Emission-Scanning Electron Microscopy (FE-SEM), Ultra-violet visible spectroscopy, and Keithley 4200 Semiconductor Characterization System (SCS). AFM provided thin film roughness, grain size, and surface morphology. FE-SEM was performed to show cross sectional view of the fully developed thin film transistor. Keithley 4200 SCS provided transistor characteristics including on/off ratio, mobility, and threshold voltage. The present work will provide valuable scientific input of AZO TFTs for the improvement of TFT devices.

Funder Acknowledgement(s): This work is supported by the NSF-CREST Grant number HRD 1547771 and NSF-CREST Grant number HRD 1036494.

Faculty Advisor: Sangram K. Pradhan, skpradhan@nsu.edu

Role: The research I conducted was characterization of the AZO active layer including electrical, optical and structural characterization. Along with the characterization, I also conducted the fabrication of the AZO TFT. Assistance for the transistor characteristics was provided by the co-authors.