High‐quality nonpolar m ‐plane GaN substrates grown by HVPE

Relatively large size (about 10 mm × 10 mm) m ‐plane GaN substrates are grown by hydride vapor phase epitaxy (HVPE). The high crystalline quality of the substrates was observed by X‐ray diffraction analysis. Typical full widths at half maximum values of X‐ray rocking curves measured for the (101 0) and (101 2) reflections were 25–35 arcsec and 30–40 arcsec, respectively. The defect density distribution was analyzed from the [101 0] direction by the cathodeluminescence method. The dark spot density decreased in the growth direction and could be as low as 2.5 × 105 cm–2. No stacking faults could be seen. The surface roughness after the lapping, polishing and cleaning was measured by atomic force microscopy and the RMS roughness was 0.072 nm. All of the phonon modes that the selection rules allow have been observed in polarized Raman measurements. High‐quality large‐size m ‐plane GaN substrates will enable the realization of commercial production of nonpolar devices. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)