Composition dependent transport properties of strain relaxed InxGa1−xAs(x<0.45) epilayers

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Abstract
The concentration and mobility of the two‐dimensional electron gas present at the interface between strain‐relaxed, lattice matched, InyAl1−yAs/InxGa1−xAs(x < 0.45), modulation doped heterojunctions grown by means of compositionally step‐graded buffer layers on GaAs substrates, were measured at room temperature and at 77 K. The composition dependence of the electron density is attributed to the dependence of the band‐gap energy of InxGa1−xAs and that of InyAl1−yAs on x, with a conduction band offset, ΔEc∼0.67ΔEg. The room temperature electron mobility increases from 9×103 cm2/V s for x=0.07 to 1.05×104 cm2/V s for x=0.45. Such strain‐relaxed heterostructures have higher electron mobilities than similar pseudomorphic structures with the same sheet electron concentration.