Experimental study of the effect of local atomic ordering on the energy band gap of melt grown InGaAsN alloys

We present a study of melt grown dilute nitride InGaAsN layers by x-ray photoelectron spectroscopy (XPS), Raman and photoluminescence (PL) spectroscopy. The purpose of the study is to determine the degree of atomic ordering in the quaternary alloy during the epitaxial growth at near thermodynamic equilibrium conditions and its influence on band gap formation. Despite the low In concentration (∼3%) the XPS data show a strong preference toward In–N bonding configuration in the InGaAsN samples. Raman spectra reveal that most of the N atoms are bonded to In instead of Ga atoms and the formation of N-centred In₃Ga₁ clusters. PL measurements reveal smaller optical band gap bowing as compared to the theoretical predictions for random alloy and localised tail states near the conduction band minimum. (paper)