Origin of size-dependent photoluminescence decay dynamics in colloidal γ-Ga2O3 nanocrystals

We studied size-dependent dynamics of defect-based photoluminescence of colloidal gamma-Ga2O3 nanocrystals in the framework of the donor-acceptor pair model. Two theoretical models were developed based on relative positioning of donor and acceptor sites: (1) for random distribution of defects throughout the nanocrystal volume and (2) for surface segregation of defects. The results of the modeling indicate that defect sites are predominantly located in the vicinity of nanocrystal surfaces and that the density of defects increases with decreasing nanocrystal size. The donor Bohr radius obtained as a fitting parameter suggests an increase in the donor binding energy with decreasing nanocrystal size. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3698390]