Growth of a Thick AlN Epilayer by Using the Mixed-Source Hydride Vapor Phase Epitaxy Method
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Growth of a Thick AlN Epilayer by Using the Mixed-Source Hydride Vapor Phase Epitaxy Method Kyoung Hwa Kim, Jung Hyun Park, Hyung Soo Ahn,∗ Min Yang and Sam Nyung Yi Department of Electronic Materials Engineering, Korea Maritime and Ocean University, Busan 49112, Korea
Injun Jeon and Chae Ryong Cho Department of Nanoenergy Engineering and Department of Nano Fusion Technology, Pusan National University, Busan 46241, Korea
Suck-Whan Kim† Department of Physics, Andong National University, Andong 36729, Korea (Received 20 April 2020; accepted 27 May 2020) A thick AlN epilayer with an approximately 1.25-mm thickness was grown on a sapphire substrate by using a mixed source (Al+Ga of very small amount) at around 1150 ◦ C for 2 hours and a mixedsource hydride vapor phase epitaxy (HVPE) method in a simplified reactor interlinked in series with no separation between the source and the growth zones. The simplified reactor was designed to minimize the reaction between quartz and AlCl vapor species of a high partial pressure at around 1150 ◦ C. The growth of the thick AlN epilayer seemed to be due to the very high growth rate (maximum value of 600 μm/h) resulting from the minimization of the response distance between the vapor species and the source gases caused by interlinking in series the edge of the source zone with the substrate in the growth zone. The characteristics of the grown thick AlN epilayer were investigated by using cross-sectional scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS), Raman spectrometry and X-ray diffraction (XRD). Keywords: AlN, Hydride vapor phase epitaxy, Sapphire substrate, AlCl DOI: 10.3938/jkps.77.282
I. INTRODUCTION
AlN epilayers are applied in many fields, such as detectors in solid-state ultraviolet, light-emitting diodes and high-performance III-nitride optoelectronic devices [1– 9], because the AlN epilayer with a direct energy gap of 6.2 eV has diverse characteristics including high thermal conductivity, and good chemical and physical stability [10–13]. The sapphire substrate has been used for growth of high-quality AlN epilayers because of the small lattice mismatch with the AlN epilayers. This is due to the small difference in the thermal expansion coefficients between the epilayer and the substrate which reduces the residual strain, caused by cracking of the layer during cooling and the formation of defects due to background doping, in the epitaxial layers [14–22]. Thin epilayers have been grown using techniques such as molecular beam epitaxy, metal-organic chemical vapor deposition (MOCVD) and sputtering. The growths ∗ E-mail: † E-mail:
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pISSN:0374-4884/eISSN:1976-8524
of thick materials, such as bulk AlN crystals, by using hydride vapor phase epitaxy (HVPE), vaporization, sublimation recondensation, ammonothermal, and solution growth methods have been reported: however, bulk AlN crystals, in spite of all this many research, are still useless for device applications because of poor quality and high cost [23–26]. Although
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