Centimeter-Sized Bulk GaN Single Crystals Grown by the Na-Flux Method with a Necking Technique

Abstract

Centimeter-sized bulk GaN single crystals with large dislocation-free areas were fabricated by the Na-flux method with a necking technique. This necking, which is the key technique in Czochralski growth of dislocation-free Si ingots, was realized using a newly developed GaN point seed. Structural properties of grown crystals were investigated using panchromatic cathodoluminescence (CL) measurements and X-ray diffraction. Prism-shape and well-faceted bulk GaN crystals with dimensions as large as 0.85 cm (width) and 1 cm (length) were grown by this technique. The GaN single crystal grown for 400 h have full-width at half-maximum values for c// and c⊥ as narrow as 42.8 and 32.5 arcsec, respectively, indicating an extremely high quality. Panchromatic CL images of (0001) GaN wafers sliced from grown crystals revealed that large areas of the wafers were dislocation free. We concluded that the necking technique in Na flux GaN growth may be a major breakthrough for fabricating large dislocation-free GaN ingots.