Paper TF-TuP11
Study of Electronic Structure in In-Ga-ZnO Amorphous Semiconductor Films

Tuesday, November 1, 2011, 6:00 pm, Room East Exhibit Hall

Amorphous oxide semiconductor In-Ga-ZnO (IGZO) has unique electron transport properties such as large electron mobility (10-30 cm²/Vs) and good uniformity for active-matrix flat panel display applications [1-2]. Theoretical studies indicate the high electron mobility in amorphous IGZO is due to spherically spread orbitals of metal cations forming unaffected electron transport path. It has been proposed amorphous IGZO has strong ionic electronic structure compared to the covalent electronic structure in amorphous Si [3]. However, the transport mechanism to result in high electron mobility in amorphous structure has not been experimentally explained yet. The focus of this study is to use surface probe, optical as well as Raman spectroscopic techniques to investigate the electronic structure in IGZO. Amorphous IGZO thin films are being grown at room temperature by pulsed laser deposition. Initial Hall effect measurements indicate that amorphous IGZO films have electron concentration of 9×10¹⁹ cm^-3 with Hall mobility of 16.8 cm²/Vs. Raman spectroscopy is being used to analyze the lattice arrangement, i.e. the amorphous state and the bonding properties in IGZO films. During film processing, hydrogen is being introduced into the material system to modulate the defect state levels and band gap structure in IGZO. X-ray photoelectron spectroscopy is being used to obtain the valence band spectrum of IGZO films. The energy state within the band gap is being analyzed using deep level transient spectroscopy. The correlation of growth parameters on optical properties as well as electronic structure will be described in this work.

[1] K. Nomura, H. Ohta, K. Ueda, T. Kamiya, M. Hirano, H. Hosono, Science 300,1269 (2003).

[2] K. Hoshino, J.F. Wager, IEEE Trans. Electron Devices 31,818 (2010).

[3] T. Kamiya, H. Hosono, NPG Asia Mater. 2, 15 (2010).