Structural and Optical Characterization of Dilute Bi-doped GaN Nanowires Grown by Molecular Beam Epitaxy

We have performed detailed studies of the epitaxy and characterization of dilute Bi-doped GaN nanostructures on Si substrate. During the growth, the substrate temperature is initially kept at a high temperature for nanowire formation followed by low-temperature epitaxy to promote Bi incorporation under N₂-rich conditions. Scanning electron microscopy shows that lowering the GaBiN growth temperature causes gradual changes in top c-plane nanowire morphology which indicates incremental incorporation of foreign Bi atoms. Room temperature photoluminescence emission is dominated by the band-to-band transition peak of wurtzite GaN at a wavelength of ~365 nm with intensities of Bi-doped GaN nanowires considerably lower than that of the intrinsic GaN nanowires. Moreover, room temperature micro-Raman spectra show that there are additional peaks near 650 cm^-1 and 729 cm^-1 in the Bi-doped samples which can be attributed to Bi local vibrational mode, indicative of a small amount of Bi incorporation in the GaN lattice. Such one-dimensional nanowires permit the synthesis of dislocation-free highly mismatched alloys due to strain relaxation, allowing efficient light absorption and charge carrier extraction. As such, work is in progress to study the photo(electro)chemical properties for N≡N and C-H bond activation of such a unique nanowire alloy system.