Assessment of microscopic lattice structures in dilute (AlGaIn)NAs laser materials by local mode spectroscopy and numerical simulations

Abstract

In the framework of a rigid-ion model we report the results of a comprehensive Green’s function analyses of the Fourier transform infrared (FTIR) absorption and Raman scattering data on localized vibrational modes (LVMs) to investigate the microscopic lattice structures related with the nitrogen incorporation in (AlGaIn)NAs alloys. Contrary to the outcome of a recent FTIR report of LVMs on GaInNAs multiple-quantum well structures, our group-theoretical analyses of impurity vibrations support the earlier IR and Raman scattering experiments providing corroboration to the fact that upon annealing and/or by increasing In(Al) composition in GaIn(Al)NAs there occur structural changes causing N environment to transform from NAsGa4 to NAsIn(Al)Ga3 and/or NAsIn2(Al2)Ga2 microstructures. From the force variation correlation with bond covalency for the closest mass acceptor CAs(a−) and isoelectronic NAs(i) defects in GaAs we have obtained the corrected value of u for Al–N bond predicting NAs local mode in AlAs (∼510cm−1) at a higher frequency than that of GaAs:N (471cm−1). Theoretical results of impurity modes for Al–N complexes in GaAlNAs are compared and discussed with the existing Raman data.