SOME OPTICAL AND EPR PROPERTIES OF STRAIN-FREE GAN CRYSTALS OBTAINED BY AMMONO METHOD

AMMONO GaN is grown spontaneously from ammonia solution in form of reg ular, well shaped,few micrometer crystals. Photoluminescence spectra o f these crystals are characterized by fixed positions of very narrow e xciton lines (FWHM down to 1 meV), where free excitons A, B, C, resolv ed two donor bound excitons and acceptor bound exciton are visible. Fi xed position of exciton lines is in contrast to small changes of line energies which have been always observed for epitaxial GaN layers beca use of strain present in them. Free electron concentration of AMMONO G aN is less than few times 10(15) cm(-3), as estimated from EPR signal of shallow donor. The above-mentioned facts qualified these crystals a s state of the art strain-free, model material for basic parameter mea surements of GaN. In this work, results of PL and EPR measurements per formed on AMMONO GaN crystals are presented and discussed.