Electronic bulk and surface transport in n- and p-InAs films on GaAs substrates*

We experimentally studied magnetotransport of bulk carriers and surface electrons in InAs MOCVD-grown on GaAs, as well as the spin interaction between surface carriers and transition metal ions. Hall and Shubnikov-de Haas data show the existence of 3 carrier types: interface carriers at the GaAs/InAs interface, bulk carriers and surface state carriers. In n-type samples total density $\textit{n}$ and total mobility $\mu$ increase with increasing n-doping. At a threshold doping level, transport in the system changes from multi-carrier to single-carrier. In p-type InAs, $\textit{n}$ and $\mu$ show a strong temperature dependence, partly due to carrier freeze-out. The p-type InAs also shows GaAs/InAs interface carriers. At low temperatures and low magnetic fields, weak antilocalization (AL) is observed due to spin-orbit interaction, mostly from electrons with Rashba spin-orbit interaction in the surface accumulation layer. Due to its sensitivity to spin phenomena AL can be used as a sensitive probe of interactions between the surface electrons and local magnetic moments. The magnetic species modify the surface electron spin-flip scattering and spin-orbit scattering. Spin-orbit scattering is seen to be increased by Co$^{2+}$ and Ni$^{2+}$, while suppressed by Fe$^{3+}$.