Using solid-source molecular-beam epitaxy with a rf-plasma source, we have grown GaInNAs/GaAs single-quantum-well lasers operating at 1.32 μm. For a broad-area oxide stripe, uncoated Fabry–Perot laser with a cavity length of 1600 μm, the threshold current density is 546 A/cm2 at room temperature. The internal quantum efficiency for these lasers is 80%, while the materials losses are 7.0 cm−1. A characteristic temperature of 104 K was measured in the temperature range from 20 to 80 °C. Optical output up to 40 mW per facet under continuous-wave operation was achieved for these uncoated lasers at room temperature.
We have studied the effects of annealing of InGaNAs/GaAs heterostructures on diffusion at the interfaces and the resultant changes in optical and structural properties. Interdiffusion between In and Ga was found to be very significant. Inserting a thin compressively strained layer of InxdGa1−xdNydAs1−yd on either side of an InxqGa1−xqNyqAs1−yq quantum well (QW) suppressed this interdiffusion significantly. As a consequence, a blue shift of the photoluminescence signal after annealing remained small and the optical activity was largely improved. It was also found that a small amount of N incorporated in InGaAs QWs embedded in GaAs increased the In/Ga interdiffusion and that increased mechanical stresses enhanced the interdiffusion.
a b s t r a c tFe 1−x Co x nanowires in self-assembled arrays with varying compositions were produced by the templateassisted pulsed electrochemical deposition method. The structural and magnetic properties of the arrays were investigated using several experimental techniques. TEM analyses indicated that the nanowires were regular, uniform, 8 m in length and 50 nm in diameter. The results of X-ray diffraction indicated that the body-centered-cubic (bcc) (␣), face-centered-cubic (fcc) (␥), and hexagonal-close-packed (hcp) () Fe-Co phases appeared in different compositions. Magnetic measurements showed that the coercivity and squareness of the hysteresis loops of the Fe 1−x Co x changed with their compositions, which may be attributable to shape anisotropy. The room temperature 57 Fe Mössbauer spectra of the arrays of the Fe 1−x Co x nanowires revealed strong shape anisotropy.
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