Metal Organic Chemical Vapor Deposition of Zinc Oxide
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Metal Organic Chemical Vapor Deposition of ZnO William E. Fenwick1, Vincent T. Woods1, Ming Pan1,2, Nola Li1, Matthew H. Kane1,3, Shalini Gupta1, Varatharajan Rengarajan2, Jeff Nause2, Ian T. Ferguson1,3* 1 School of ECE, Georgia Institute of Technology, Atlanta, GA 30332, USA 2 Cermet Inc, 1019 Collier Rd, Atlanta, GA 30318, USA 3 School of MSE, Georgia Institute of Technology, Atlanta, GA 30332, USA
ABSTRACT Thin films of ZnO were grown by metal organic chemical vapor deposition (MOCVD) in a vertical injection rotating disk reactor (RDR) system on sapphire substrates. Kinetics of ZnO growth by MOCVD were studied and an optimal growth window for a RDR tool was determined. Experimental growth conditions were chosen based on calculations of Reynolds Number (Re) and mixed convection parameter in order to select a growth window with stable gas flow and uniform heat transfer. Growth parameters were systemically varied within this window to determine the optimal growth conditions for this MOCVD tool and to study how these parameters affect film growth and quality. Properties of ZnNiO films grown by MOCVD were also studied to determine the effects of Ni incorporation on structural, optical, and magnetic properties.
INTRODUCTION Recent work has shown the potential to p-dope zinc oxide (ZnO) thin films for use in device applications. ZnO, with its direct wide bandgap of 3.37eV and high exciton binding energy, is promising in optoelectronic applications such as UV light emitters and detectors1. ZnO also has potential in applications such as gas sensors, acoustic resonators, surface acoustic wave (SAW) devices, and spintronic devices2. These applications, however, require the investigation and development of processes that can consistently yield high quality ZnO thin films and a better understanding of the effects of transition metal incorporation on structural, optical, and magnetic properties of ZnO. ZnO thin films have been grown using molecular beam epitaxy, magnetron sputtering, pulsed laser deposition, and spray pyrolysis. Recently, metal organic chemical vapor deposition (MOCVD) has gained popularity as a method to grow high quality ZnO thin films3. MOCVD is favored over other growth techniques because of its flexibility, controllability, scalability into larger commercial systems, and applicability to current device technology. However, unlike the relatively mature MOCVD technique for III-V compound semiconductor growth, research into MOCVD growth of ZnO is still in its early stages. Process development requires a detailed knowledge of reactor dynamics and growth kinetics. Reports in the literature show a large variation in growth conditions and results4. An understanding of how the growth parameters such as substrate temperature, chamber pressure, VI/II ratio, and disk rotation speed affect gas flow, heat distribution, and film growth is crucial to developing a process that can consistently yield high quality ZnO thin films.
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Corresponding author, 777 Atlantic Dr. Atlanta, GA 30332, Email
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