AMMONO method of GaN and AlN production

The new method of GaN and AlN production, called AMMONO, consists in metal reaction with supercritical ammonia at temperatures below 500 degrees 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 temperature. Narrow exciton lines in photoluminescence measurements of AMMONO GaN, performed at helium temperature (FWHM similar to 1 meV), confirm its very good crystalline quality. Electron paramagnetic resonance measurements reveal that the AMMONO GaN has a high purity, and allow estimation of the concentration of uncompensated shallow donors to be less than 5 x 10(15) cm(-3) (a record low value for undoped GaN). (C) 1998 Elsevier Science S.A.