Growth of nano- and microstructured GaN in bulk powder and on substrate

摘要

A detailed investigation has been carried out to study the effects of growth temperature, NH_3 flow rate, grinding-mediated annealing of the as-synthesized GaN powder, different substrates and Au catalyst on the products grown by a direct reaction of Ga with NH_3. Nanowires of diameter in the range 15-40 nm are grown around a narrow temperature zone, 1000 ℃ < t < 1100 ℃, with a 150 seem NH_3 gas flow rate. Beyond this temperature zone, GaN platelets are formed in a large scale. Annealing of the as-synthesized GaN powder at 800 ℃ after a grinding process results in the growth of dendrite-like GaN nanostructures and above 800 ℃, only hillocks of GaN platelets are grown. The layers formed on sapphire and ZnO/quartz substrates consist of GaN nano- and microrods of diameter 40-100 nm and 1-1.5 μm respectively that show ultraviolet (UV) emission peaks below 400 nm. Large-scale synthesis of GaN nanorods of diameter 60-100 nm has been achieved on Au/quartz substrate at 1050 ℃ with a 150 seem of NH_3 gas flow rate. The nanorods exhibit a strong UV emission peak indicating a better optical quality.