Changes of the Physical Properties of Sputtered InGaN Thin Films Under Small Nitrogen Gas Flow Variations
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In this research work, InGaN triple compound was grown under low nitrogen gas flows by using the sputtering technique. The structural, optical and morphological characteristics of the InGaN compound have been studied in detail. X-ray diffraction (XRD) and Raman for structural analysis; absorption measurement technique for optical properties; scanning electron microscopy and atomic force microscopy (AFM) measurement techniques were used for the study of the morphological characteristics. In the XRD analysis, the film deposited at 0 sccm gas flow exhibits a (0002) peak of InN, (0002) and (10–11) peaks of GaN. Other films show dendritic structure. In the Raman analysis, the optical phonon modes of the InGaN compound are A1(LO) and E2(high). Optical band gaps are found to be 2.57 eV, 2.54 eV, 3.03 eV and 2.93 eV for 0–0.4–0.8–1.2 sccm, respectively. These changes are ascribed to the degraded crystallinity of the grown films at high nitrogen flow rates. The surface morphology of the InGaN films grown at 0 sccm displays clusters of near-spherical-shaped nanoparticles over the surface. In the results of the AFM, the surface topography of the InGaN thin films deposited with lower nitrogen content exhibited fewer grains on the surface, especially on 0.4 sccm gas flow rate. The number of grains increased with higher N2 gas flow rates. The surface roughness of the films decreased with increasing N2 gas flows. It is clear that surface morphology of the films depends on the gas flow rate very much. Due to their morphological properties, we can say that they are suitable structures for optoelectronic applications and friction applications in engineering. We can also say that films with a hexagonal crystal structure and different optical band gaps can be used in device applications such as LED, laser diode and power electronics.
KeywordsIII-Nitrides thin films sputtering N2 gas flow effect p-type Si substrate
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We are thankful to Dr. Emre Gür (Physics Dept., Atatürk University,) for all deposition and characterization measurements made at DAYTAM. We would like to thank Ahmet Emre Kasapoğlu (DAYTAM) for helping us work on the growth system.
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