Fabrication of high-quality two-dimensional electron gases by overgrowth of focused-ion-beam-doped Al[sub x]Ga[sub 1-x]As

Reuter, D.; Riedesel, C.; Schafmeister, P.; Meier, C.; Wieck, A. D.
January 2003
Applied Physics Letters;1/20/2003, Vol. 82 Issue 3, p481
Academic Journal
We have investigated two-dimensional electron gases (2DEGs) in inverted selectively doped GaAs/Al[SUBx]Ga[SUB1-x]As heterostructures fabricated by molecular-beam epitaxy (MBE) overgrowth of focused-ion-beam (FIB)-doped Al[SUBx] Ga[SUB1-x]As layers. In a first MBE step, the Al[SUBx]Ga[SUB1-x]As barrier was grown, before the sample was transferred to the FIB system. There, Si was implanted with 60 keV employing doses between 1 × 10[SUP12] and 1 × 10[SUP14] cm[SUP-2] and thereafter the sample was transferred back to the MBE system where the Al[SUBx]Ga[SUB1-x]As spacer as well as the GaAs top layer were grown. To protect the surface during the growth interruption, an amorphous As layer was used. Either an in situ annealing step before regrowth (30 s at 730 °C) or an ex situ thermal processing (30 s at 750 °C) after regrowth was used to remove the crystal damage due to the implantation. For the ex situ annealing step, we obtained mobilities up to 1.2 × 10[SUP5] cm[SUP2]/V s at 4.2 K after illumination whereas we observed mobilities up to 1.5 × 10[SUP6] cm[SUP2]/V s employing the in situ annealing step.


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