Effective mass enhancement of two-dimensional electrons in a one-dimensional superlattice potential

We report effective mass enhancement of two-dimensional (2D) electrons in an atomically precise one-dimensional AlGaAs/GaAs superlattice potential fabricated by the cleaved-edge overgrowth technique. Magnetotransport measurements reveal that the mobility of the 2D electrons increases with electron density n_2D. At low densities (n_2D∼1.3×10¹¹ cm^-2), the effective mass m* of the 2D electrons is 0.14 m_e, where m_e is the free-electron mass. This value of 0.14 m_e is twice the effective mass of electrons in GaAs (0.067 m_e). m* increases with n_2D and is ∼0.16 m_e at 2.7×10¹¹ cm^-2. We explain these results based on the formation of energy minibands along the superlattice direction. The electron scattering time τ is calculated from the mobility and effective mass data. At 0.3 K, τ increases with n_2D from 5 to 11 ps as n_2D is varied from 1.1×10¹¹ to 2.7×10¹¹ cm^-2.