Synthesis, optical properties and growth mechanism of leaf-like GaN crystal

Outwardly oriented leaf-like gallium nitride crystal assemblies were synthesized on alumina substrate by a facile thermal chemical vapor deposition method. The as-grown products were spherical conglomerate with "leaves" radiating from central core distributed sparsely on substrate. Each "leaf" with flat and smooth surface was single crystalline GaN with hexagonal structure, its normal dimensions were 4 μm in thickness, 35 μm in width and 300 μm in length. The micro-Raman measurement had shown E₂(high) mode located at 567 cm^-1 with a FWHM of 4 cm^-1 as well as the room temperature photoluminescence result of a strong near-band-edge emission at 369 nm without the yellow band evidenced the good crystalline quality of as-prepared "leaf"-like GaN crystal. The formation mechanism of leaf-like crystal assemblies was systematically investigated and discussed on the basis of the experiment results. The resultant leaf-like crystal assembly may be a promising building block for three-dimension device applications in future.