Fundamental Research on Nitride Metalirgy-New Rovte for GaN Synthesis-

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GaN is an important functional material because of its ability to emit short wave length light. Although nitriding of gallium metal by nitrogen gas is thermodynamically feasible at moderate temperatures, it is practically difficult under a normal pressure because incipient reaction leads to a layer of GaN which forms an effective barrier to further reaction. In this communication, we show that a complex nitride such as Li_3GaN_2 can act as a reaction mediator during nitriding of gallium alloys with nitrogen gas. GaN is synthesized without direct physical contact between gallium and nitrogen gas. Feasibility of this reaction is confirmed by measuring thermodynamic properties of Li_3GaN_2, and mechanism of this reaction is discussed using an isothermal chemical potential diagram constructed from the results of the present study. For example, the Gibbs energy of formation of Li_3GaN_2 is determined by measuring electromive force measurement using galvanic cell, and potential range of nitrogen chemical potential under GaN I Li_3GaN_2 two phase equilibrium is discussed. New approach for analyzing the feasibility of GaN synthesis through a mediator is demonstrated.