Synthesis, structure, and optical properties of colloidal GaN quantum dots

Colloidal chemistry was used to synthesize GaN quantum dots. A GaN precursor, polymeric gallium imide, {Ga(NH)(3/2)}(n), which was prepared by the reaction of dimeric amidogallium with ammonia at room temperature, was heated in trioctylamine at 360 degrees C for one day to produce GaN nanocrystals. The GaN particles were separated, purified, and partially dispersed in a nonpolar solvent to yield transparent colloidal solutions that consisted of individual GaN particles. The GaN nanocrystals have a spherical shape and mean diameter of about 30 +/- 12 Angstrom. The spectroscopic behavior of colloidal transparent dispersion has been investigated and shows that the band gap of the GaN nanocrystals shifts to slightly higher energy due to quantum confinement. The photoluminescence spectrum at 10 K (excited at 310 nm) shows band edge emission with several emission peaks in the range between 3.2 and 3.8 eV, while the photoluminescence excitation spectrum shows two excited-state transitions at higher energies. (C) 1999 American Institute of Physics. [S0003-6951(99)04230-8].