An interrogation of the zinc oxide–gallium oxide phase space by plasma enhanced chemical vapor deposition

• Published in: Journal of crystal growth Vol. 263; no. 1-4; pp. 283 - 290
• Main Authors: Robbins, J.J., Fry, C., Wolden, C.A.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.03.2004; Elsevier
• Subjects: A1. Phase diagrams; A3. Metalorganic chemical vapor deposition; B1. Gallium compounds; B1. Oxides; B1. Zinc compounds; Chemical vapor deposition (including plasma-enhanced cvd, mocvd, etc.); Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Materials science; Methods of deposition of films and coatings; film growth and epitaxy; Phase diagrams and microstructures developed by solidification and solid-solid phase transformations; Phase diagrams of other materials; Physics; B1. Oxides; B1. Gallium compounds; B1. Zinc compounds; A3. Metalorganic chemical vapor deposition; A1. Phase diagrams; Phase diagrams; Inorganic compounds; Electrical conductivity; Doping; Polycrystals; Bl. Oxides; Crystal growth from vapors; Gallium additions; Precursor; Bl. Zinc compounds; Thin films; PECVD; Al. Phase diagrams; Phase space; Semiconductor materials; Ternary compounds; Transition element compounds; Binary compounds; Amorphous state; Experimental study; CVD; Zinc oxides; Gallium oxides
• ISSN: 0022-0248; 1873-5002
• DOI: 10.1016/j.jcrysgro.2003.10.093

Polycrystalline metal oxide thin films were deposited by mixing combinations of diethylzinc and trimethylgallium into an oxygen plasma. Plasma-enhanced chemical vapor deposition was shown to be a flexible tool for materials exploration, as the entire zinc–gallium-oxide phase space was explored by simply altering precursor flow rates. Film identification was performed using measurements of intrinsic optical properties as well as X-ray diffraction. The compounds synthesized included zinc oxide, gallium-doped zinc oxide (ZnO:Ga), the spinel ZnGa2O4, and amorphous gallium oxide. A phase diagram was established for PECVD synthesis as a function of the organometallic precursor composition. It was found that gallium addition had a profound impact on both the deposition rate and resistivity of the films. Small levels the gallium addition produced an order of magnitude improvement in both deposition rate and electrical properties. When the gallium fraction was >50% the deposition rate saturated and the films were insulating. Optical emission spectroscopy was used to probe the plasma chemistry of the system. It was shown to be quite complex, typified by the example that decreasing the diethylzinc fraction in the feedstream dramatically increased the density of atomic zinc in the plasma.