Separating parallel conduction from two-dimensional magnetotransport in   high mobility InP/InGaAs MOCVD-grown heterostructures
  In this Letter, four-point magnetotransport of high mobility InGaAs/InP heterointerfaces is measured from 1.6 K to 300 K and from 0 to 15 T, and an analysis is shown whereby the mobility and density of the two-dimensional (2D) accumulation layer can be separately characterized from that of the parallel conducting dopant layer over all but a small intermediate temperature range. Standard magnetotransport regimes are defined as the temperature increases from 1.6 K to 300 K, namely quantum Hall (QH), Shubnikov de Haas (SdH), and Drude regimes (D), and in the QH and D regimes different analyses are applied to deduce densities and mobilities of both layers separately. Quantitative conditions for the intermediate SdH regime are defined, within which both QH and D analyses fail. The density and activation energy of unintentional donors at the InP epilayer/substrate interface is deduced. At base temperature, QH minima are resolved down to B = 0.4 T at nu = 20, revealing a mobility of mu = 160,000 cm^2/Vs. The 2D system maintains this high mobility up to at least 40 K in this high quality structure. 
Yang Tang, Chuanle Zhou, M. Grayson
cond-mat.mes-hall cond-mat.mtrl-sci