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A detailed account of the experimental results from optically detected magnetic resonance ͑ODMR͒ studies of grown-in defects in ͑Al͒GaNP alloys, prepared by molecular beam epitaxy, is presented. The experimental procedure and an in-depth analysis by a spin Hamiltonian lead to the identification of two Ga i defects ͑Ga i -A and Ga i -B͒. New information on the electronic properties of these defects and the recombination processes leading to the observation of the ODMR signals will be provided. These defects are deep-level defects. In conditions when the defect is directly involved in radiative recombination of the near-infrared photoluminescence band, the energy level of the Ga i -B defect was estimated to be deeper than ϳ1.2 eV from either the conduction or valence band edge. In most cases, however, these defects act as nonradiative recombination centers, reducing the efficiency of light emission from the alloys. They can thus undermine the performance of potential photonic devices. High thermal stability is observed for these defects.

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We report gas-source molecular-beam epitaxy of Ga1−xInxNyP1−y grown on GaAs(100) substrates. Nitrogen incorporation dramatically reduces the Ga1−xInxP band gap. With nitrogen incorporation, the photoluminescence (PL) peak energy exhibits an inverted S-shaped dependence with temperature, and the low-temperature PL spectra exhibit an asymmetric line shape with a low-energy tail. Both indicate the presence of N-related localized states, which dominate the radiative recombination processes at low temperature. N incorporation significantly reduces the free-electron concentration and mobility. The free-electron concentration of N-containing Ga0.48In0.52N0.005P0.995 decreases dramatically with high-temperature annealing (800 °C), from 4.4×1018 to 8.0×1016 cm−3. This is believed to be due to passivation of Si by N through the formation of Si–N pairs.

The nitrogen and hydrogen vibrational modes of hydrogenated GaAs(1-y)N(y) and GaP(1-y)N(y) have been studied by infrared absorption spectroscopy and density functional theory. Data for the stretching modes observed for samples containing both hydrogen and deuterium show that the dominant defect complex contains two weakly coupled N-H stretching modes. Theory predicts an H-N-H complex with C(1h) symmetry whose vibrational properties are in excellent agreement with experiment. Additional results provide further support for the defect model that has been proposed. Uniaxial stress results confirm that the symmetry of the H-N-H complex must be lower than trigonal. The vibrational properties predicted by theory for the H-N-H complex also lead to an assignment of the wagging modes that are observed. Experimental and theoretical results for GaAs(1-y)N(y) and GaP(1-y)N(y) are remarkably similar, showing that the same H-N-H defect complex is responsible for the properties of H in these fascinating materials