Growth of GaN single crystals from a Na-Ga melt at 750°C and 5 MPa of N2

GaN single crystals were synthesized by heating a Na-Ga melt placed in a BN crucible at 750 degrees C and 5 MPa of N-2 for 200 h. The yields and morphology of the single crystals were varied with Na/(Na+Ga) molar ratio (r(Na)) in the starting composition of the melts, Colorless transparent bulk single crystals with a size of 3 mm in the longest direction were obtained at r(Na) = 0.60. The full-width at half-maximum (FWHM) of the rocking curve measured for 0004 X-ray diffraction peak was 25 arcsec, The electrical resistivity of the platelet crystals was 0.04 Omega cm with a carrier concentration (n-type) of 1-2 x 10(18) cm(-3) and a mobility of 100 cm(2) V-1 s(-1) at room temperature. No emission peaks or bands except at 365nm, corresponding to near-band emission, were observed at room temperature in the cathodoluminescence spectrum. (C) 2000 Elsevier Science B.V. All rights reserved.