Optical characterization of GaN by N+ implantation into GaAs at elevated temperature.

Both hexagonal wurtzite and cubic zinc blend GaN phases were synthesized in GaAs by 50 keV N+ implantation at 400 °C and subsequent annealing at 900 °C for 15 min in N2 ambient. The crystallographic structural and Raman scattering studies revealed that GaN phases were grown for fluence above 2×1017 cm-2. Temperature-dependent photoluminescence study showed a sharp direct band-to-band transition peak ∼3.32 eV at temperature ≤=200 K. The intermediate band-gap value, with respect to ∼3.4 eV for hexagonal and ∼3.27 eV for cubic phases of GaN, is indicative of the formation of mixed hexagonal and cubic phases [ABSTRACT FROM AUTHOR]