We report an ultrahigh room-temperature hole drift mobility obtained in a Si0.2Ge0.8 quantum well with a parabolic-like Ge profile, which has at its core a p-type modulation-doped (MOD) Si/Si0.2Ge0.8/Si0.65Ge0.35/Si(001) heterostructure. High-conductivity holes at 293 K with a drift mobility of 3600 cm(2) V-1 s(-1) at a sheet carrier density of 4.94x10(12) cm(-2) were obtained in the Si0.2Ge0.8 quantum well after optimum annealing at 750degreesC for 30 min. Hall mobility and sheet carrier density of this heterostructure are 1776 cm(2) V-1 s(-1) and 2.37x10(13) cm(-2), respectively. Structural characterization of the as-grown and the annealed samples revealed that the annealing had caused Si0.2Ge0.8 channel broadening, smearing of interfaces, and formation of a parabolic-like Ge profile that significantly improved room-temperature hole transport properties. The reported values of hole mobility are much higher than in the bulk Ge. (C) 2004 American Institute of Physics
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