1/f noise in InGaAs/GaAs linear graded buffer layers

Noise spectroscopy has been used as a sensitive technique to assess the quality of In/sub x/Ga/sub 1-x/As linear graded buffer layers grown onto GaAs substrates. Samples having different dislocation structure and quality, determined by design and growth conditions, have been analyzed. Samples with a high dislocation density have been shown to be very efficient 1/f noise sources, with Hooge's parameters (/spl alpha//sub H/) as high as 4/spl times/10/sup -1/. A Hooge model, based on mobility fluctuation in the depletion regions surrounding dislocations, has been used to explain the observed dependence of /spl alpha//sub H/ on mobility /spl mu/. While a power law /spl alpha//sub H//spl prop//spl mu//sup /spl beta// with /spl beta//spl ap/-1 is found for the noise generated in samples with a high dislocation density (HDD), /spl beta//spl ap/+2 seems to hold when sample quality improves, where much lower /spl alpha//sub H/ values (100 times) are obtained. These results allow to correlate the scattering centers that limit the mobility with the noise sources existing in the conducting layer of these structures.