The effect of periodic silane burst on the properties of GaN on Si (111) substrates
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The effect of periodic silane burst on the properties of GaN on Si (111) substrates K. Y. Zang 1, S. J. Chua 1,2 and C. V. Thompson 1,3 1 Singapore-MIT Alliance, E4-04-10, NUS, 4 Engineering Drive 3, 117576, Singapore 3 Department of Materials Science and Engineering, MIT, Cambridge, MA 02139, USA L. S. Wang 2, S. Tripathy2 and S. Y. Chow 2 2 Institute of Materials Research & Engineering, 3 Research Link, 117602, Singapore ABSTRACT The periodic silane burst technique was employed during metalorganic chemical vapor deposition of epitaxial GaN on AlN buffer layers grown on Si (111). Periodic silicon delta doping during growth of both the AlN and GaN layers led to growth of GaN films with decreased tensile stresses and decreased threading dislocation densities, as well as films with improved quality as indicated by x-ray diffraction, micro-Raman spectroscopy, atomic force microscopy, and transmission electron microscopy. The possible mechanism of the reduction of tensile stress and the dislocation density is discussed in the paper. INTRODUCTION
Heteroepitaxial growth of Gallium nitride (GaN) materials has been intensively studied for the application in opto-electronic devices and high-power, high temperature microelectronic devices due to its wide bandgap characterics. Major developments have led to the commercial products such as high brightness blue/green light emitting diodes 1 and laser diodes 2. Growth of GaN onto silicon substrate offers very attractive potential for incorporating GaN devices onto silicon-based very large-scale integrated circuits, low cost and available in large wafer size of silicon. However, due to the large difference in lattice constant, crystal structure, and thermal expansion coefficient, it is rather difficult to epitaxially grow GaN on Si substrate3. A high density of threading dislocations on the order of (109~1010 cm-2) exists in the GaN film on silicon substrates due to large lattice mismatch, which will affect the performance of the GaN based devices4-6. On the other hand, cracks are typically formed either due to the large tensile stress in the GaN film during growth or during the cooling down process with large difference in thermal expansion coefficient between GaN and Si. Reducing tensile stress and dislocation density are the important issues to be solved for the growth of crack-free and device-quality GaN on silicon substrate. To overcome these difficulties, many solutions including introduction of low temperature-AlN interlayer7-9, SiNx mask10 or delta-doping technique11-13 during the growth of GaN layer have been attempted as an effective way to reduce the dislocation densities and improve the crystalline qualities of GaN films on silicon. In this study, we report the growth of high quality of GaN on silicon with periodic silane burst during growth of both the high-temperate AlN buffer layer and GaN layers by metalorganic chemical vapour deposition (MOCVD). The effects of the periodic silane burst technique on the reduction of dislocation density and tensile stress
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