Comparison of strained channel InGaAs high electron mobility structures grown on InP and GaAs

The carrier transport properties of strained In0.75Ga0.25As channels grown on (001) InP by molecular beam epitaxy in high electron mobility structures differ markedly from similarly strained (Delta d/d = 1.5 x 10(-2)) In0.22G a0.78As channels grown on (001) GaAs substrates. Hall sheet concentrations for the InP-based structures do not change significantly as the thickness o f the channel increases although the mobility does decrease by about 10%-15 % as the channel thickness increases to about 35 nm. GaAs-based structures show much more significant decreases in both sheet concentration and mobili ty at these higher channel thicknesses. < 110 > 60 degrees misfit dislocati ons are observed in both sets of samples, The density of misfits in the InP structures is only slightly lower than the density in the GaAs-based struc tures for a given channel thickness. The InP-based structures also show the presence of edge dislocations and surface roughness undulations along the < 100 > directions. It appears that misfit dislocations at the channel inte rfaces are less important for the transport properties of InP-based structu res than for GaAs-based structures. (C) 1999 American Vacuum Society. [S073 4-211X(99)01203-2].