Vibrational Characteristics of High-Quality MBE Grown GaAs_1-x-ySb_yN_x/GaAs (001) Epilayers

The significant disparity between the size and electronegativity of N and group-V (P, As, Sb) atoms in dilute III-V-Ns remains a cornerstone for developing the next-generation electronics. Variations in the structural, optical, and phonon properties of the quaternary GaAs_1-x-ySb_yN_x alloys are being used for improving the high-performance photovoltaic energy and optoelectronic technologies. Bandgap Eg tunability has assisted efficient light emission/detection to cover the crucial optical fiber wavelengths for the low-cost integrated chips in data communications and sensing devices. The lattice dynamical properties of these materials are critical for assessing the reliability to evaluate the performance of long-wavelength lasers, photodetectors, and multi-junction solar cells. Our systematic Raman measurements on high-quality MBE grown GaAs0.946Sb0.032N0.022/GaAs samples have detected ωTO(Γ)GaAs and ωTO(Γ)GaAs phonons along with a high frequency N_As local mode near ~476 cm^-1. Weak phonon structures on both sides of the broad 476 cm^-1 band are interpreted forming a complex N_As-Ga-Sb_As defect center. Using a realistic rigid-ion model in the Green's function framework, the simulations of impurity modes for isolated and complex defects have provided corroboration to the experimental data.