From N isoelectronic impurities to N-induced bands in the GaNxAs1−x alloy

${\mathrm{GaN}}_x{\mathrm{As}}_{\text{1−x}}$ samples with $\text{x<3\%}$ grown by metalorganic vapor phase epitaxy were studied by low-temperature photoluminescence under hydrostatic pressure and photomodulated reflectance spectroscopy. The transformation from N acting as an isoelectronic impurity to N-induced band formation takes place at $\text{x≈0.2\%.}$ The N level does not shift with respect to the valence band edge of ${\mathrm{GaN}}_x{\mathrm{As}}_{\text{1−x}}.$ Concentration as well as hydrostatic-pressure dependence of the ${\mathrm{GaN}}_x{\mathrm{As}}_{\text{1−x}}$ bands can be described by a three band kp description of the conduction band state $E_{-}$ and $E_{+}$ and the valence band at $\text{k=0.}$ The model parameters for $\text{T<20}$ and $\text{T=300\hspace{0.05em}}\mathrm{K}$ were determined by fitting the model to the experimental data. Modeling the linewidth of the $E_{-}$ transition by combining the kp model and ion statistics leads to the conclusion that the electron-hole pairs are strongly localized.