Ambacher, Oliver

Cimalla, Volker

Wang, Chunyu

Digitale Bibliothek Thüringen

  PROCEEDINGS 11-15 September 2006      FACULTY OF ELECTRICAL ENGINEERING AND INFORMATION SCIENCE    INFORMATION TECHNOLOGY AND ELECTRICAL ENGINEERING - DEVICES AND SYSTEMS, MATERIALS AND TECHNOLOGIES FOR THE FUTURE      Startseite / Index: http://www.db-thueringen.de/servlets/DocumentServlet?id=12391 51. IWK Internationales Wissenschaftliches Kolloquium International Scientific Colloquium Impressum  Herausgeber: Der Rektor der Technischen Universität llmenau  Univ.-Prof. Dr. rer. nat. habil. Peter Scharff  Redaktion: Referat Marketing und Studentische Angelegenheiten  Andrea Schneider   Fakultät für Elektrotechnik und Informationstechnik  Susanne Jakob  Dipl.-Ing. Helge Drumm  Redaktionsschluss: 07. Juli 2006  Technische Realisierung (CD-Rom-Ausgabe):  Institut für Medientechnik an der TU Ilmenau  Dipl.-Ing. Christian Weigel  Dipl.-Ing. Marco Albrecht  Dipl.-Ing. Helge Drumm  Technische Realisierung (Online-Ausgabe):  Universitätsbibliothek Ilmenau    Postfach 10 05 65  98684 Ilmenau  Verlag:   Verlag ISLE, Betriebsstätte des ISLE e.V.  Werner-von-Siemens-Str. 16  98693 llrnenau   © Technische Universität llmenau (Thür.) 2006  Diese Publikationen und alle in ihr enthaltenen Beiträge und Abbildungen sind urheberrechtlich geschützt. Mit Ausnahme der gesetzlich zugelassenen Fälle ist eine Verwertung ohne Einwilligung der Redaktion strafbar.   ISBN (Druckausgabe): 3-938843-15-2 ISBN (CD-Rom-Ausgabe): 3-938843-16-0  Startseite / Index: http://www.db-thueringen.de/servlets/DocumentServlet?id=12391  51st Internationales Wissenschaftliches Kolloquium Technische Universität Ilmenau  September 11 – 15, 2006    Tuning of electrical properties of InxOy thin films grown by MOCVD for different applications Ch. Wang*, V. Cimalla, and O. Ambacher Institute of Micro – and Nanotechnologies, Technical University Ilmenau P.O.Box 100565, 98684 Ilmenau, Germany  Indium oxide is a very important material for microelectronic applications. It is a transparent semiconducting wide band gap (~ 3.6 eV) oxide material, which is n-type. Various methods for the preparation of In2O3 films like evaporation [1] and sputtering [2] are described in the literature. With such technologies, a variety of electrical properties of In2O3 thin films can be obtained (metallic, semiconducting, or insulating behavior). Thin highly conducting In2O3 films are widely used as transparent electrodes in optoelectronic devices, i.e. flat-panel displays [3] and solar cells [4]. The highly resistive In2O3 thin films are widely used in gas detectors [2], especially in ozone (O3) sensors [2]. Here, we report on a method of the deposition of InxOy films with the tunable properties by MOCVD for different applications. The InxOy films were deposited in a horizontal MOCVD reactor (AIX200) on c-plane Al2O3 substrates. TMIn and H2O have been used, respectively, as indium and oxygen sources. The electrical measurements at room-temperature showed the strong change in the electrical properties of the InxOy films (Fig. 1). The sheet electron density of the InxOy films decreased more than one order of magnitude, from 5.3*1014 cm-2 at 300°C to 4.5*1013 cm-2 at 500°C. At the same time, the special resistance increased about two orders of magnitude, from 3.8*10-3 Ωcm at 300°C to Fig. 1: Dependence of electron density of InxOyfilms on the substrate temperatures. 0246300 400 500 600temperature (°C)electron density (1014  cm-2)                                                 * Electronic mail: chunyu.wang@tu-ilmenau.de 2.5*10-1 Ωcm at 500°C. Furthermore, the films deposited at 300°C are degenerated as observed by temperature dependent measurements because the electron concentration increased only slightly (~40%) from liquid-nitrogen temperature to 270°C.  Optical transmission measurements were carried out on 60 nm thick films deposited at 300°C. The films have a transmittance of over 85% in the visible region (wavelength from 400 to 760 nm). From the points mentioned above, the films are suitable for applications as transparent conducting electrodes. The films deposited at high substrate temperatures are more resistive than those deposited at low temperatures. They are assumed to be applied in gas sensors, for example for O3. The resistance change of the InxOy film deposited at 600°C is shown in Fig. 2. The sample was annealed at 1100°C 30 s in oxygen atmosphere before measurements. The film was first exposed by UV-light (photoreduction). Then, it was exposed to O2 or O3 atmosphere (oxidation). The resistance changes only slightly, from about 2 kΩ after photoreduction to 6.6 kΩ after O2 exposure, while the resistance changes 20 times up to 40 kΩ after O3 exposure. Fig. 2: Photoreduction and subsequent oxidation by O2 and O3 of InxOy film deposited at 600°C. In conclusion, we have reported on the tuning of electrical properties of InxOy films grown by MOCVD. The films deposited at low substrate temperatures are degenerated and transparent in the visible range. So, they are suitable to work as conducting transparent electrodes. The films deposited at high substrate temperatures are more resistive and are suitable for gas sensors. It is feasible to grow InxOy films only using MOCVD for different applications. This work was supported by TMWTA within the project “INOZON” under grand no. B509-04011.  References:    [1] S. Muranaka, Thin Solid films 221 (1992) 1.    [2] M. Bender, N. Katsarakis, E. Gagaoudakis, E. Hourdakis, E. Douloufakis, V. Cimalla, and G. Kiriakidis, J. Appl. Phys. 90 (2001) 5382. [3] K. A. Evans, in: A. J. Downs (Ed.), Chemistry of aluminium, gallium, indium and tallium, Chapman & Hall, London, 1993, p. 248. [4] C. G. Granqvist, Appl. Phys. A 57 (1993) 19. 

Tuning of electrical properties of InxOy thin films grown by MOCVD for different applications

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Tuning of electrical properties of InxOy thin films grown by MOCVD for different applications

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