A novel technique to make Ohmic contact to a buried two-dimensional   electron gas in a molecular-beam-epitaxy grown $GaAs/Al_{0.3}Ga_{0.7}As$   heterostructure with Mn $\delta$-doping
  We report on the growth and characterization of a new Diluted Magnetic Semiconductor (DMS) heterostructure that presents a Two-Dimensional Electron Gas (2DEG) with a carrier density $n \sim 1.08 \times 10^{12} cm^{-2}$ and a mobility $\mu \sim 600 cm^{2} / (Vs)$ at T $\sim$ 4.2K. As far as we know this is the highest mobility value reported in the literature for GaMnAs systems. A novel technique was developed to make Ohmic contact to the buried 2DEG without destroying the magnetic properties of our crystal. 
A. Bove, F. Altomare, N. B. Kundtz, Albert M. Chang, Y. J. Cho, X.   Liu, and J. Furdyna