AMMONO METHOD OF GAN AND ALN PRODUCTION

The new method of GaN and AlN production, called AMMONO, consists in m etal reaction with supercritical ammonia at temperatures below 500 deg rees C and pressures below 5 kbar. The product of such a reaction, i.e , a powder of regular, well-shaped crystals (a few micrometres in size ), reveals a very intense and homogenous luminescence, even at room te mperature. Narrow exciton lines in photoluminescence measurements of A MMONO GaN, performed at helium temperature (FWHM similar to 1 meV), co nfirm its very good crystalline quality. Electron paramagnetic resonan ce measurements reveal that the AMMONO GaN has a high purity, and allo w estimation of the concentration of uncompensated shallow donors to b e less than 5 x 10(15) cm(-3) (a record low value for undoped GaN). (C ) 1998 Elsevier Science S.A.