IEEE Seminar Announcement
Title: Growth of III-Nitride Thin Films and Structures
Speaker: Dimitris Korakakis, Ph.D.
Date: Monday, Nov. 9, 2009
Time: 5:00-5:50 PM
Location: ESB G102, WVU Evansdale Campus

Abstract: III-Nitride based semiconductors are of significant interest for the fabrication of optoelectronic devices, such as Light Emitting Diodes (LEDs) and Laser Diodes (LDs), primarily due to the ability to engineer the emission across the visible spectrum and into the Ultra Violet (UV) regime by adjusting the molar concentration. Furthermore, due to the piezoelectric, electronic, and mechanical properties, III-Nitride materials are well suited for Micro-Electro Mechanical Systems (MEMs) or Nano-Electro Mechanical Systems (NEMs). In this work, the growth and characterization of III-Nitride thin films and structures via Metal Organic Vapor Phase Epitaxy (MOVPE) will be presented.

Within the III-Nitride material system, Aluminum Gallium Nitride (AlxGa1-xN) alloys are the most promising for UV device fabrication due to the wide, direct band gap, while Indium Nitride (InxGa1-xN) films are well suited for visible emission. The growth of high quality AlxGa1-xN alloys via MOVPE is challenging due to the large sticking coefficient of the Al species compared to that of Ga and also the high reactivity of Al precursors1. As a result, films are often characterized by large dislocation densities, cracks, and poor conductivity. Likewise, material growth issues arise in InxGa1-xN films due to the large lattice mismatch and low miscibility between InN and GaN2. The growth of AlxGa1-xN and InxGa1-xN films and the techniques used to improve quality will be discussed. In particular, digital alloy growth of AlxGa1-xN has been investigated as a viable means of growing high quality ternary alloys via MOVPE. Digital alloy growth consists of layers of binary or ternary alloys with a period thickness of a few monolayers1. The influence of the growth parameters on the film properties will be presented. Additionally, the influence of growth parameters on the V-defect formation in InxGa1-xN will be discussed.

In addition, the growth of III-Nitride structures will be presented. This will include the growth of AlN/GaN Distributed Bragg Reflectors (DBRs) and AlN suspended structures. Indium has been used as a surfactant during the growth of AlN/GaN DBRs and been shown to reduce the crack length per square millimeter by a factor of two. Finally, the growth of AlN suspended structures fabricated using a sacrificial silicon oxide layer will be presented. In this work infrared absorption spectra of polycrystalline and crystalline AlN films through micro-Fourier Transform Infrared Spectroscopy (FTIR) transmission techniques has been investigated.

1. M. E. Hawkridge, Z. Liliental-Weber, H. Jin Kim, S. Choi, D. Yoo, J. Ryou, and R. Dupuis. Appl. Phys. Lett. 94, 071905 (2009).
2. F. A. Ponce, S. Srinivasan, A. Bell, L. Geng, R. Liu, M. Stevens, J. Cai, H. Omiya, H. Marui, S. Tanaka, Phys. Status Solidi C 7 (2003).
   

Speaker bio: Dr. Korakakis received his B.S. in Theoretical Physics from London University, Queen Mary and Westfield Colleges in 1986, his M.S. in Manufacturing Engineering in 1994 from Boston University and his Ph.D. in Electrical Engineering in 1998 from Boston University. In 1997 he joined the School of Physics and Astronomy and the School of Electrical and Electronic Engineering at the University of Nottingham as research staff. In 2000 he joined the department of Physics at West Virginia University as a Research Assistant Professor. He joined the Lane Department of Computer Science and Electrical Engineering in 2002, where he is now an Associate Professor. His research is focused in the growth and characterization of III-nitride alloy films and heterostructures. He has published over 40 peer-reviewed articles and has more than 170 citations for his work in the past 6 years.