A new route for the synthesis of nitrides: The solvothermal preparation ofGaN

A new solvothermal route for the synthesis of nitrides is proposed using li quid NH3 as solvent in supercritical conditions. Such a preparation method was applied to the synthesis of GaN using gallium metal as starting materia l. GaN is a wide band-gap semi-conductor (3.4eV). It is a very attractive nitr ide due to its various applications in micro- and opto-electronics [1,2]. C onsequently, many research groups are interested in synthesising GaN. Two m ethods have been principally developed: (i) synthesis of thin films by epitaxy [3,4], (ii) synthesis of bulk GaN by high pressure method [5, 6]. The new proposed process leads to fine microcrystallites of GaN with the wu rtzite-type structure. The chemical purity can be optimised versus the synt hesis mechanism. The size and shape of the crystallites would be influenced by the nature of the nitriding additive and the thermodynamical conditions (pressure and temperature) used for the synthesis.