Philippine E-Journals

X-Ray Diffraction Analysis of Strained IngaAs/GaAs Superlattices Grown on GaAs (001) Substrates Via Molecular Beam Epitaxy

Joel G. Fernando | Armando S. Somintac

Discipline: Education

 

Abstract:

Strained InxGal-xAs/GaAs superlattices grown on GaAs(100) substrates via Molecular Beam Epitaxy (MBE) are studied. The samples are characterized using non-destructive X-ray diffraction (XRD) measurements and photo luminescence (PL) spectroscopy. The Indium mole fractions and the period thicknesses of the samples are determined using XRD analysis along with standard elasticity theory. Discrepancies in the values of the period thickness and In mole fraction are observed in one sample and are attributed to the generation of misfit dislocations and strain relaxation. XRD short-angle scans, carried out in four azimuthal angles to assess the quality of the superlattices, show that the quality of the samples grown with high In content is inferior compared to samples with low In mole fraction. Using the conventional finite square well model, the theoretical PL energy emissions are computed and compared with the experimental PL emissions. The PL energy emissions of samples grown with higher indium content deviate significantly from theoretical PL emissions. These indicate that indeed the strains are relaxed in these samples. In addition, samples with high indium mole fraction show low-grade optical properties, e.g., low PL intensities and large full width at half maximum (FWHM).