Carbon-doped high mobility two-dimensional hole gases on (110) faced   GaAs
  Carbon-doped high mobility two-dimensional hole gases grown on (110) oriented GaAs substrates have been grown with hole mobilities exceeding 10^6 cm^2/Vs in single heterojunction GaAs/AlGaAs structures. At these high mobilities, a pronounced mobility anisotropy has been observed. Rashba induced spin-splitting in these asymmetric structures has been found to be independent on the transport direction. 
S. Schmult, C. Gerl, U. Wurstbauer, C. Mitzkus and W. Wegscheider