Abstract
We use a combination of molecular beam epitaxy (MBE) and focused ion beam (FIB) implantation to fabricate selectively doped inverted GaAs/Al x Ga 1− x As heterostructures containing two-dimensional electron gases (2DEGs). The FIB implantation doping is carried out after growth of the Al x Ga 1− x As barrier and enables the lateral patterning of the doped area. During the growth interruption we use an amorphous arsenic layer to protect the surface against contamination. We find an in situ MBE annealing step of 730°C for 20 s prior to overgrowth as a means of significantly improving the electron mobility. Electron mobilities up to 9.5×10 5 cm 2/ V s at 4.2 K after illumination have been obtained. For ex situ annealed samples the peak mobility was only 1.2×10 5 cm 2/ V s , suggesting a higher quality of the regrown layer for the in situ annealed sample.
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