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

GaNxAs1-x samples with 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 x approximate to 0.2%. The N level does not shift with respect to the valence band edge of GaNxAs1-x. Concentration as well as hydrostatic-pressure dependence of the GaNxAs1-x bands can be described by a three band kp description of the conduction band state E- and E+ and the valence band at k = 0. The model parameters for T<20 and T = 300 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. (C) 2000 American Institute of Physics. [S0003-6951(00)02423-2].