Fabrication of high quality two-dimensional electron gases by overgrowth of focused ion beam implantation doped AlxGa1−xAs

We use a combination of molecular beam epitaxy (MBE) and focused ion beam (FIB) implantation to fabricate selectively doped inverted GaAs/AlxGa1−xAs heterostructures containing two-dimensional electron gases (2DEGs). The FIB implantation doping is carried out after growth of the AlxGa1−xAs 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 View the MathML source prior to overgrowth as a means of significantly improving the electron mobility. Electron mobilities up to View the MathML source at View the MathML source after illumination have been obtained. For ex situ annealed samples the peak mobility was only View the MathML source, suggesting a higher quality of the regrown layer for the in situ annealed sample.