domingo, 25 de julio de 2010


The samples considered in this review were grown by different techniques. One set of samples was grown by solid-source molecular-beam epitaxy (MBE) and consists of GaAs1−yNy/GaAs and InxGa1−xAs1−yNy/GaAs single quantum wells (QWs) having In concentration x=25 to 42%, N concentration y=0.7 to 5.2%, and QW thickness L=6.0 to 8.2 nm. MBE-grown GaAs1−y Ny/GaAs epilayers were also considered (layer thickness t=310 nm, with y <0.01 and y=0.81 and 1.3%). Another set of samples consists of four 0.5-μm-thick GaAs1−yNy/GaAs epilayers (y=0.043, 0.1, 0.21, and 0.5%) grown by metalorganic vapor-phase epitaxy [28,29]. Finally, GaP1−yNy epilayers were grown by gas-source MBE on GaP. In this case, nitrogen concentrations are y=0.05, 0.12, 0.6, 0.81, and 1.3%. The GaP1−yNy epilayer thickness is 250 nm for all samples, except for the y=1.3% epilayer, which is 750-nm thick. In all cases, the composition and layer thickness of the samples have been derived by X-ray diffraction measurements. Hydrogenation was obtained by ion-beam irradiation from a Kaufman source with the samples held at 300°C . The ion energy was about 100 eV, and the current density was a few tens of μA/cm2. Several hydrogen doses (dH=1014 to 1020 ions/cm2) were used.

Posthydrogenation thermal annealing was performed at 1.0×10−6 torr at temperatures, Ta, ranging between 220°C and 550°C and for various durations, ta, ranging between 1 and 50 h. The electronic properties of the samples were investigated mainly by means of photoluminescence (PL) spectroscopy. For InxGa1−xAs1−yNy and GaAs1−yNy samples, PL was excited by the 515-nm line of an Ar+ laser or by an Nd-vanadate laser (excitation wavelength equal to 532 nm). For GaP1− yNy, the 458-nm line of an Ar+ laser was used, instead. PL was dispersed then by a 1-m single-grating monochromator or a 0.75-m double monochromator and detected by a liquid-nitrogen-cooled Ge detector or (InGa)As linear array, or by a photomultiplier with a GaAs/Cs cathode. 
                                                ROSSANA HERNANDEZ
                                    ELECTRONICA DEL ESTADO SOLIDO

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