Magneto-optical and transport studies of ultrahigh mobility films of InAs grown on GaAs by molecular beam epitaxy

InAs layers of very high electrical quality are grown on GaAs substrates by molecular beam epitaxy (MBE). The observation of sharp cyclotron resonance and donor lines (linewidths approximately=1 cm -1 ) in far-infrared magneto-optical studies suggest that the low-temperature mobilities in the bulk of the films are in the range 200 000-300 000 cm 2 V -1 s -1 with an electron concentration of approximately=2*10 14 cm -3 . A strong but broad cyclotron resonance line and the Shubnikov-de Haas effect are observed from a two-dimensional electron gas (2DEG) at the surface or GaAs interface (n S approximately=1*10 12 cm -2 and mu s approximately=20 000 cm 2 V -1 s -1 ). As a consequence of parallel conduction from the low mobility layer the Hall mobility measured from a 5 mu m thick sample is 80 000 cm 2 V -1 s -1 at 77 K and that in a 2 mu m sample is only 30 000 cm 2 V -1 s -1 . The width of bulk cyclotron resonance and impurity lines depend only weakly on thickness and consequently scattering from dislocations generated by the misfit at the GaAs/InAs interface is not thought to affect the bulk mobility strongly down to film thicknesses of 1 mu m. The parallel conduction from the 2DEG also produces a large magnetoresistance. Please note - the first author name has been corrected from Homes to Holmes