Plasma-assisted vapor liquid phase epitaxial growth of dilute GaSbxN1−x and GaBiyN1−y alloys: Confirmation of band gap reduction discontinuity

Single crystal quality films of dilute $\mathrm{Ga}{\mathrm{Sb}}_x{\mathrm{N}}_{1\ensuremath{-}x}$ and $\mathrm{Ga}{\mathrm{Bi}}_y{\mathrm{N}}_{1\ensuremath{-}y}$ alloys were synthesized through a plasma-assisted vapor liquid phase epitaxy technique in which nitrogen radicals, antimony, and bismuth species diffuse through molten gallium and form alloys at the substrate. Incorporation fractions $x$ up to 0.009 (three samples), and $y$ up to 0.011 (two samples) were achieved. Morphology and photoluminescence characteristics as well as x-ray spectra were evaluated confirming the alloys possess gallium nitride wurtzite structure but with a slightly higher lattice parameter as determined with differences of hundredths of degrees in the diffraction peak position of plane (002). UV-Vis spectrometry measurements of the alloys also resemble those of pure gallium nitride, indicating dilute anion substitution at the levels reported in this study are not sufficient to promote significant changes in the band gap versus host material, gallium nitride. First-principles density functional theory incorporating the local-density approximation/generalize gradient approximation+U formalism also reveals that relatively small concentration of Sb impurities is not sufficient to achieve a significant narrowing of gallium nitride band gap.