We have investigated the optical transitions in Ga1−yInyNxAs1−x/GaAs single and multiple quantum wells using photovoltaic measurements at room temperature. From a theoretical fit to the experimental data, the conduction band offset Qc, electron effective mass me*, and band gap energy Eg were estimated. It was found that the Qc is dependent on the indium concentration, but independent on the nitrogen concentration over the range x=(0–1)%. The me* of GaInNAs is much greater than that of InGaAs with the same concentration of indium, and increases as the nitrogen concentration increases up to 1%. Our experimental results for the me* and Eg of GaInNAs are quantitatively explained by the two-band model based on the strong interaction of the conduction band minimum with the localized N states.

We have studied the effect of rapid thermal annealing (RTA) on GaInNAs/GaAs quantum wells (QWs) grown by molecular-beam epitaxy using a dc plasma as the N source. It was found that RTA at low temperature (LT, 650 °C) and high temperature (HT, 900 °C) could both improve the QW quality significantly. To clarify the mechanism of quality improvement by RTA, a magnetic field perpendicular to the path of the N plasma flux was applied during the growth of the GaInNAs layers for the sake of comparison. It was found that LT-RTA mainly removed dislocations at interfaces related to the ion bombardment, whereas, HT-RTA further removed dislocations originating from the growth. LT-RTA caused only a slight blueshift of photoluminescence peak wavelength, probably due to defect-assisted interdiffusion of In–Ga at the QW interfaces. The blueshift caused by HT-RTA, on the other hand, was much larger. It is suggested that this is due to the fast defect-assisted diffusion of N–As at the QW interfaces. As defects are removed by annealing, the diffusion of In–Ga at interfaces would be predominant.