Growth of strained-layer GaAs/Ge superlattices by magnetron sputtering: Optical and structural characterization

Strained layer superlattices of GaAs/Ge/GaAs and Ge/GaAs/Ge have been grown by magnetron sputtering of different intercalated layer thickness. The sam ples exhibited good crystallographic quality, pseudomorphic growth on the s ubstrate, as well as superlattice characteristics. Layer periodicity, conce ntration profile and the thicknesses of the resultant films were examined b y high-resolution x-ray diffraction, secondary ion mass spectroscopy, infra red (IR) optical transmission measurements, and Raman spectroscopy. The het erostructures exhibited IR attenuation peaks in transmission between 0.5 an d 1.0 eV, whose energy position was characterized as a function of the thic kness of the intercalated thinner layers. The combined results of these tec hniques reveal that the intended GaAs layers are in fact composed of (GaAs) (1-x)(Ge-2)(x) alloys with a few percent Ge content. Experimental and theor etical results have been modeled with the transmittance model, which assume s that light hits the surface normally and takes the alternating layer thic knesses as variable parameters. Both, experimental and theoretical results agree to within 3%. (C) 2001 American Institute of Physics.