Abstract: Square patterns with different sizes are prepared on c-sapphire by plasma-enhanced chemical vapor deposition of SiO2,conventional optical lithography,and wet chemical etching.The GaN film is selectively grown on this patterned c-sapphire by hydride vapor phase epitaxy.An optical microscope,atomic force microscope,scanning electron microscope,high resolution double crystal X-ray diffraction (DCXRD),and Raman shift spectrum are used to analyze the sample.The GaN layer with a thickness of about 20μm grown on an area of 100μm×100μm is crack-free while the GaN layers grown on areas of 300μm×300μm and 500μm×500μm have cracks.Thus,the full width at half maximum (FWHM) of DCXRD of (0002) reflection of GaN grown on the independent square window of c-sapphire decreases when the area of window decreases,indicating better quality GaN single crystal.The minimum FWHM is 530" .From the corner of the square window towards its edge and center,the in-plane compressive stress of GaN decreases due to the interaction between the epitaxial lateral overgrown GaN wings and the SiO2 mask underneath,and the bending of 90° of threading dislocations at the border of the window regions.

Key words: GaN, selective area growth, HVPE