Preparation of large freestanding GaN substrates by hydride vapor phase epitaxy using GaAs as a starting substrate

A freestanding GaN substrate over 2 inches in size was successfully prepared for the first time by hydride vapor phase epitaxy (HVPE) using GaAs as a starting substrate. In the experiment, a GaAs (111)A substrate with a SiO2 mask pattern on its surface was used. A thick GaN layer was grown on the CaAs substrate at 1030 degreesC through the openings in the SiO2 mask. By dissolving the GaAs substrate in aqua regia, a freestanding GaN substrate about 500 mum thick was obtained. The full-width at half maximum (FWHM) in the omega -mode X-ray diffraction (XRD) profile of GaN (0002) plane was 106 arcsec. The dislocation density of the GaN substrate obtained was determined to be as low as 2 x 10(5) cm(-2) by plan-view transmission electron microscopy (TEM). Hall measurements revealed the n-type conductivity of the GaN substrate with typical carrier concentration and carrier mobility of 5 x 10(18) cm(-3) and 170 cm(2), V-1, s(-1), respectively.