Gallium Nitride Single Crystal Growth by Flux Method

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Colorless transparent platelet single crystals with a maximum area of 10.0 X 5.0mm^2 by 0.03-0.1 mm thick was obtained at 750℃, 5Mpa of N2 for 360h and 0.60 of Na/(Ga+Ns)mole ratio (γ_<Na>). At 800℃, 3MPa of N_2 for 250h and γ_<Na>=0.60, colorless transparent prismatic crystals having a size of 1.0x0.5x0.5 mm^3 were obtained. Prismatic single crystals with 1.0xO.5x0.5 mm3 size were also obtained at 750℃, 5MPa of N_2 for 450h and γ_<Na>=0.54. The morphology of GaN single crystals tended to change from platelet to prismatic with increasing growth temperature, decreasing N_2 pressure and decreasing γ_<Na>.The fill width at half-maximum (FWHM) of the rocking curve measured for O004 X-ray diffraction peak was 25 arcsec, for 1 mm size platelet crystals and 32 arcsec, for 3 mm size platelet crystals. Hall measurements were carried out by the van der Pauw technique for the platelet crystals having a size of 1x1x0.2 mm^3. The concentration of free electrons in the crystal was 1-2x10^<18>cm-^3 and the mobility was 100 cm^2V-^1S-^1 at room temperature. The electrical conductivity was about 25 Ω-1cm-1 and almost independent of temperature between 120 and 350 K. The near band-edge emission of GaN was observed at 365 nm (3.4eV) by CL spectroscopy. No bands or peaks except the peak from the near band emission were observed. These results indicate the high quality of the GaN single crystals synthesized in this study.