Epitaxial Growth of TiN ON GaAs(100) by Pulsed Laser Deposition
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EPITAXIAL GROWTH OF TiN ON GaAs(100) BY PULSED LASER DEPOSITION TSVETANKA S. ZHELEVA, K. JAGANNADHAM, A. KUMAR AND J. NARAYAN Department of Materials Science and Engineering, North Carolina State University, Raleigh,NC 27695-7916 ABSTRACT Epitaxial growth of TiN films on GaAs(100) by pulsed laser deposition has been studied. Excimer KrF laser (X=248 nm, t=30 ns) has been used for deposition of TiN films in a chamber maintained at vacuum of < 10-6 torr. The microstructure of TiN films has been characterized by x-ray diffraction and transmission electron microscopy (TEM). Cross-sectional high resolution TEM showed a smooth unreacted interface between the single crystalline TiN film and GaAs. The predominant epitaxial relationship was found to be [11O]TiN//[01O]GaAs, (220)TiN//(040)GaAs at a substrate temperature of 3500 C. Modelling of epitaxial growth showed that the interfacial energy is an important term responsible for 450 rotation of the TiN unit cell with respect to that of GaAs. The high strain energy associated with the coherent epilayer is reduced by domain epitaxial growth. These films were characterized using high-resolution TEM techniques, and experimental results were rationalized by thin film growth modeling. INTRODUCTION Titanium nitride is used as a diffussion barrier because of its high temperature (up to 5500C) stability, chemical stability, and low diffussion rate of impurities [11. Titanium nitride films grown epitaxially at low temperature possess very low resistivity and can be used for metallization. Further, TiN also has good etch-stop capability enabling a chlorine based dry-etch chemistry to be employed without undercut or post etch corrosion. Laser physical vapor deposition is one of the most useful deposition techniques because the high kinetic energy associated with the laser plume gives rise to crystalline epitaxial growth even at low temperatures. Recently we reported domain epitaxial growth of titanium nitride on silicon [2.1. It was shown that domain epitaxial growth with four unit cells of titanium nitride matching with three unit cells of silicon becomes favorable due to a decrease of the lattice strain in the epilayer. Because of the high carrier mobility and resistance against radiation damage, TiN/GaAs structures form a potential candidate for use in high speed electronic and optoelectronic devices. In the present work , we have investigated epitaxial growth of TiN on GaAs(001) substrates using pulsed laser deposition. The characteristics of epitaxial growth were analyzed by x-ray diffraction and high resolution electron microscopy techniques. The results are found to be consistent with our model calculations. EXPERIMENTAL RESULTS Titanium nitride thin films were deposited on GaAs(100) by the laser physical vapor deposition (LPVD) process[3]. Eximer KrF laser with X=248 rim, t=30ns was used at 5 Hz repetition rate. The laser has been used with an incident energy density on the TiN target of 10 J/cm 2 . The GaAs substrate was cleaned for ten minutes each in TCE (trichlorethylene),
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