Graphene and Semiconductors

Statement of the Problem: Carbon doped GaN has been widely studied and applied for p-type GaN and yellow light-emitting diodes. However, the sites carbon located, related with luminescence, characteristics has not been confirmed.Methodology & Theoretical Orientation: GaN was implanted with carbon ion using dose of 1×10¹⁷ cm^-2 and 2×10¹⁷ cm^-2 and energy of 30 keV and 40 keV. And then the implanted samples were annealed at 800℃ for 20 min and 1 h under the N₂ atmosphere. The luminescence characteristics of carbon ion implanted GaN was evaluated by PL spectrum with wavelength of 325 nm. The lattice damage of GaN was characterized by Raman spectrum and corresponding vacancy-defect evolution before and after annealing was measured by slow positron annihilation.Conclusion & Significance: Most of carbon atoms would be located at the interstitial sites after carbon ion implantation due to the absorption of vacancies, and no obvious luminescence could be observed. As the implanted samples were annealed, strong yellow luminescence was emitted and the vacancy for N (V_N) or vacancy for Ga (V_Ga) was reduced resulting from the migration of interstitial carbon (C_i) and formation of complex between them. By contrast, samples with higher dose showed stronger yellow light emission, which was related with the lower migration rate of C_i and saturated concentration of C_i-V complex.