(Ga,Mn)As grown on (311) GaAs substrates : Modified Mn incorporation and magnetic anisotropies

We report the results of a detailed study of the structural, magnetic, and magnetotransport properties of as-grown and annealed ${\mathrm{Ga}}_{0.91}{\mathrm{Mn}}_{0.09}\mathrm{As}$ thin films grown on $(311)A$ and $(311)B$ GaAs substrates. The high Curie temperature and hole density of the $(311)B$ material are comparable to those of GaMnAs grown on (001) GaAs under the same growth conditions, while they are much lower for the $(311)A$ material. We find evidence that Mn incorporation is more efficient for $(311)B$ than for (001) and significantly less efficient for $(311)A$ which is consistent with the bonding on these surfaces. This indicates that growth on $(311B)$ may be a route to increased Curie temperatures in GaMnAs. A biaxial magnetic anisotropy is observed for the (311) material with easy axes along the [010] and [001] out-of-plane directions. An additional uniaxial in-plane anisotropy is also observed with the easy axis along $[01\overline{1}]$ for the $(311)A$ material, and along $[\overline{2}33]$ for the $(311)B$ material. This observation may be of importance for the resolution of the outstanding problem of the origin of uniaxial anisotropy in (001) GaMnAs.