Synthesis of rare-earth activated AlN and GaN powders via a three-step conversion process

Using a three-step solution method, we have successfully synthesized rare-earth (RE) activated AlN, GaN, and pure GaAlN powders. Aluminium and/or gallium nitrates are first dissolved in water. For AlN:RE, rare-earth nitrates converted from their corresponding oxides of Dy³⁺ and Tm³⁺ are then added to the precursor nitrate solution. The mixture is subsequently converted into Al(OH)₃:RE by combining with aqueous NH₄OH at room temperature. The product is then mixed with aqueous NH₄F to form (NH₄)₃AlF₆:RE. The conversion process is complete when the hexafluoride compound is flushed with anhydrous ammonia to produce the final nitride product AlN:Dy³⁺,Tm³⁺. GaN, GaN:Tb³⁺ and GaAlN are synthesized similarly. Single phase, pure GaN and GaAlN formation has been confirmed. Dysprosium oxide has been observed in AlN:Dy³⁺, Tm³⁺. Oxygen concentration of approximately 4 at% has been measured in GaN powders, and is slightly higher in AlN powders. Spectroscopic measurements show clearly observable emission from Dy³⁺ and Tm³⁺ coactivated AlN samples. In activated GaN samples, Tb ³⁺ emission has been observed.